High-Speed Ground Transportation

Noise and Vibration Impact Assessment

Office of Railroad Development

U. S. Department

of Transportation

Federal Railroad

Administration 

October 2005
FINAL REPORT

High-Speed Ground Transportation

Noise and Vibration Impact Assessment

HMMH Report No. 293630-4

October 2005

Prepared by:

Harris Miller Miller & Hanson Inc.

15 New England Executive Park

Burlington, Massachusetts 01803

Submitted to:

Parsons Transportation Group

1133 15th Street NW

Washington, D.C. 20005-2701

TABLE OF CONTENTS

Chapter 1 - INTRODUCTION.............................................................................................1-1

1.1 PURPOSE.............................................................................................................1-1

1.2 ORGANIZATION OF THE MANUAL ..............................................................1-2

Chapter 2 - BASICS OF HIGH-SPEED TRAIN NOISE.....................................................2-1

2.1 NOISE DESCRIPTORS .......................................................................................2-3

2.1.1 Standard U.S. Noise Descriptors..................................................................2-4

2.1.2 Other Noise Descriptors...............................................................................2-5

2.1.3 The Lmax-SEL Relationship ........................................................................2-5

2.1.4 Onset Rate.....................................................................................................2-8

2.2 SOURCES OF HIGH-SPEED TRAIN NOISE....................................................2-9

2.2.1 Regime I: Propulsion Sources...................................................................2-10

2.2.2 Regime II: Mechanical/Structural Sources................................................2-12

2.2.3 Regime III: Aerodynamic Sources .............................................................2-12

2.3 SOUND PROPAGATION PATH......................................................................2-13

2.3.1 Divergence ..................................................................................................2-13

2.3.2 Absorption/Diffusion..................................................................................2-15

2.3.3 Shielding.....................................................................................................2-15

2.4 MATHEMATICAL MODEL OF HIGH-SPEED TRAIN NOISE....................2-17

2.4.1 Identification of Sources.............................................................................2-17

2.4.2 Basic Equations ..........................................................................................2-20

Chapter 3 - NOISE IMPACT CRITERIA ............................................................................3-1

3.1 NOISE IMPACT CRITERIA FOR HIGH SPEED RAIL PROJECTS................3-1

3.1.1 Basis of Noise Impact Criteria......................................................................3-1

3.1.2 Definitions of Levels of Impact....................................................................3-5

3.2 APPLICATION OF NOISE IMPACT CRITERIA..............................................3-7

3.2.1 Noise-Sensitive Land Uses...........................................................................3-7

3.2.2 Considerations in Applying the Noise Impact Criteria .................................3-8

3.2.3 Mitigation Policy Considerations.................................................................3-9

Chapter 4 - INITIAL NOISE EVALUATION.....................................................................4-1

4.1 NOISE SCREENING PROCEDURE ..................................................................4-2

4.2 GENERAL NOISE ASSESSMENT ....................................................................4-4

4.2.1 Noise Source Levels for General Assessment .....................................................4-6

4.2.2 Project Operating Conditions ..............................................................................4-7

4.2.3 Propagation Characteristics .................................................................................4-8

4.2.4 Study Area Characteristics................................................................................4-11

4.2.5 Noise Impact Estimation....................................................................................4-13

4.2.6 Noise Impact Inventory.....................................................................................4-14

4.2.7 Noise Mitigation Requirements.........................................................................4-16
Chapter 5 - DETAILED NOISE ANALYSIS......................................................................5-1

5.1 EXISTING CONDITIONS ........................................................................................5-3

5.1.1 Step 1: Noise Sensitive Receivers ................................................................5-3

5.1.2 Step 2: Existing Noise Exposure ..................................................................5-5

5.2 PROJECTIONS OF HIGH-SPEED TRAIN NOISE .................................................5-7

5.2.1 Step 3: Source Reference Leve ls..................................................................5-8

5.2.2 Step 4: Project Operating Conditions.........................................................5-10

5.2.3 Step 5: Propagation of Noise to Receivers.................................................5-11

5.2.4 Step 6: Cumulative Noise Exposure ...........................................................5-16

5.2.5 Step 7: Maximum Noise Level for Train Passbys ......................................5-21

5.3 STEP 8: NOISE IMPACT ASSESSMENT.............................................................5-23

5.3.1 Assessment Procedure ................................................................................5-23

5.3.2 Example of GIS Implementation................................................................5-24

5.4 MITIGATION OF NOISE IMPACT .......................................................................5-26

5.4.1 Source Treatments ......................................................................................5-27

5.4.2 Path Treatments ..........................................................................................5-29

5.4.3 Receiver Treatments...................................................................................5-31

Chapter 6 - GROUND-BORNE VIBRATION CONCEPTS...............................................6-1

6.1 DESCRIPTORS OF GROUND-BORNE VIBRATION AND NOISE...............6-3

6.1.1 Vibratory Motion..........................................................................................6-3

6.1.2 Amplitude Descriptors..................................................................................6-3

6.1.3 Ground-Borne Noise.....................................................................................6-4

6.2 HUMAN PERCEPTION OF GROUND-BORNE VIBRATION AND NOISE .6-5

6.2.1 Typical Levels of Ground-Borne Vibration and Noise ................................6-5

6.2.2 Quantifying Human Response to Ground-Borne Vibration and Noise ........6-6

6.3 FACTORS THAT INFLUENCE GROUND-BORNE VIBRATION AND NOISE.

..............................................................................................................................6-7

6.4 GROUND-BORNE VIBRATION FROM HIGH-SPEED TRAINS.................6-10

Chapter 7 - VIBRATION IMPACT CRITERIA..................................................................7-1

Chapter 8 - PRELIMINARY VIBRATION ASSESSMENT..............................................8-1

8.1 VIBRATION SCREENING PROCEDURE........................................................8-2

8.2 GENERALIZED VIBRATION ASSESSMENT PROCEDURE........................8-3

8.2.1 Base Curve ....................................................................................................8-3

8.2.2 Adjustment Factors.......................................................................................8-5

8.3 INVENTORY OF VIBRATION IMPACT........................................................8-11

Chapter 9 - DETAILED VIBRATION ASSESSMENT......................................................9-1

9.1 ASSESSMENT OF VIBRATION IMPACT........................................................9-3

9.2 CHARACTERIZING EXISTING VIBRATION CONDITIONS .......................9-4

9.3 VIBRATION PREDICTION PROCEDURE.......................................................9-7

9.3.1 Background ...................................................................................................9-7
9.3.2 Overview of Prediction Procedure using Measured Transfer Mobility........9-8

9.3.3 Measuring Transfer Mobility and Force Density (Vibration Propagation 

Testing) ......................................................................................................................9-9

9.3.4 Vibration and Structure-Borne Noise in Buildings ....................................9-16

9.4 VIBRATION MITIGATION .............................................................................9-19

Chapter 10 - NOISE AND VIBRATION DURING CONSTRUCTION ..........................10-1

10.1 CONSTRUCTION NOISE....................................................................................10-2

10.1.1 Noise from Typical Construction Equipment and Operations ...................10-2

10.1.2 Construction Noise Assessment .................................................................10-3

10.1.3 Mitigation of Construction Noise ..............................................................10-7

10.2 CONSTRUCTION VIBRATION .........................................................................10-8

10.2.1 Vibration Source Levels from Construction Equipment ...........................10-8

10.2.2 Construction Vibration Assessment ...........................................................10-9

10.2.3 Construction Vibration Mitigation ...........................................................10-10

10.2.4 Special Note on Pile Driving ....................................................................10-11

Chapter 11 - DOCUMENTATION OF NOISE AND VIBRATION ASSESSMENT......11-1

11.1 THE TECHNICAL REPORT ON NOISE AND VIBRATION ...........................11-1

11.1.1 Organization of Technical Report .................................................................11-1

11.2 THE ENVIRONMENTAL DOCUMENT............................................................11-3

11.2.1 Organization of Noise and Vibration Sections ...............................................11-4

APPENDIX A - BACKGROUND – NOISE CONCEPTS ................................................. A-1

A.1 NOISE METRICS ............................................................................................... A-1

A.1.1 A-weighted Level: The Basic Noise Unit......................................................... A-1

A.1.2 Maximum Level (Lmax) During a Single Noise Event...................................... A-2

A.1.3 SEL: The Cumulative Exposure from a Single Noise Event ........................... A-3

A.1.4 Hourly Equivalent Sound Level [Leq(h)]Error! Bookmark not defined. .......... A-3

A.1.5 Day-Night Sound Level (Ldn): The Cumulative 24-Hour Exposure from All 

Events.......................................................................................................................... A-6

A.1.6 Other Descriptors.............................................................................................. A-9

A.2 RECEIVER RESPONSE TO TRANSPORTATION NOISE............................... A-10

A.3 NOISE IMPACT CRITERIA DEVELOPMENT.................................................. A-13

A.3.1 Relevant Literature ......................................................................................... A-14

A.3.2 Basis for Noise Impact Criteria Curves.......................................................... A-15

A.3.3 Equations for Noise Impact Criteria Curves................................................... A-17

A.4 STARTLE EFFECTS FROM RAPID ONSET RATES ....................................... A-18

A.4.1 High-Speed Rail Noise Signatures................................................................. A-18

A.4.2 Research on Startle Effects............................................................................. A-19

A.4.3 Startle Effects Applied to High-Speed Train Impact Assessment.................. A-20

A.5 EFFECTS ON LIVESTOCK AND WILDLIFE................................................... A-22

A.5.1 Summary......................................................................................................... A-22

A.5.2 Noise Descriptor ............................................................................................. A-23
A.5.3 Thresholds for Disturbance............................................................................. A-23

A.5.4 Habituation...................................................................................................... A-23

APPENDIX B - DETERMINING EXISTING NOISE........................................................B-1

APPENDIX C - CONVERTING BETWEEN Lmax AND SEL ........................................ C-1

A.1 COMPUTING Lmax FOR A SINGLE TRAIN PASSBY ...................................... C-1

A.2 COMPUTING REFERENCE SEL'S FROM LMAX FOR GENERAL 

ASSESSMENT METHOD.............................................................................................. C-2

APPENDIX D -HIGH SPEED TRAIN VIBRATION MEASUREMENTS ...................... D-1

APPENDIX E - SOURCE REFERENCE LEVELS FOR CONVENTIONAL TRAINS ...E-1

APPENDIX F - GLOSSARY OF TERMS ..........................................................................F-1

APPENDIX G - BACKGROUND INFORMATION FOR FRA NOISE SCREENING 

TABLE ................................................................................................................................ G-1
LIST OF FIGURES

Figure 2-1 The Source-Path-Receiver Framework.....................................................

Figure 2-2 Typical A-Weighted Sound Levels..........................................................

Figure 2-3 Typical High-Speed Train Passby............................................................

Figure 2-4 Typical Longer-Duration High-Speed Train Event..................................

Figure 2-5 An “Energy” View of Noise Events.........................................................

Figure 2-6 Measured High-Speed Rail Onset Rates...................................................

Figure 2-7 Generalized Sound Level Dependence on Speed.....................................

Figure 2-8 Noise Sources on a Steel-Wheeled High-Speed Rail System..................

Figure 2-9 Noise Sources on a Maglev System.........................................................

Figure 2-10 Attenuation Due to Distance (Divergence)...............................................

Figure 2-11 Attenuation Due to Soft (Sound-Absorptive) Ground.............................

Figure 2-12 Noise Barrier Geometry............................................................................

Figure 2-13 Measured Values of Lmax,s vs Speed from High-Speed Rail Systems.....

Figure 2-14 Measured Values of SEL vs Speed from High-Speed Rail Systems........

Figure 3-1 Noise Impact Criteria for High-Speed Rail Projects................................

Figure 3-2 Increase in Cumulative Noise Levels Allowed by Criteria (Land Use 

Cat. 1 & 2)................................................................................................

Figure 4-1 Generalized SEL vs Speed for a High-Speed Train Passby.....................

Figure 4-2 Distance from Tracks within which Startle Can Occur for HSR..............

Figure 4-3 Typical Corridor Segment for Example 4-1, Alignment Alternative 2....

Figure 4-4 Noise Exposure vs Distance for Example 4-1.......................................

Figure 5-1 Guide to Selecting Receivers of Interest.................................................

Figure 5-2 Recommended Microphone Locations for Existing Noise Measurements

Figure 5-3 Computation of Ground Factor G for Ground Attenuation......................

Figure 5-4 Barrier Geometry Models of Terrain for Computation of Shielding........

Figure 5-5 Determining Noise Impact Using GIS.....................................................

Figure 6-1 Propagation of Ground-Borne Vibrations into Buildings........................

Figure 6-2 Different Methods of Describing a Vibration Signal..............................

Figure 6-3 Typical Levels of Ground-Borne Vibration.............................................

Figure 6-4 Occupant Response to Urban Transit-Induced Residential Vibration......

Figure 8-1 Generalized Ground-Borne Vibration Curve............................................

Figure 9-1 Impact Method for Measuring Transfer Mobility....................................

Figure 9-2 Schematic of Two Approaches for Transfer Mobility Measurements.....

Figure 9-3 Equipment Required for Field Testing and Laboratory Analysis............

Figure 9-4 Analysis of Transfer Mobility..................................................................

Figure 9-5 Force Densities for High-Speed Trains....................................................

Figure 9-6 Characteristics Force Spectra for the TR08 on Each Type of Guideway.

Figure 9-7 Approximate Foundation Response for Various Types of Buildings.......

Figure A-1 Example A-Weighted Sound Level Time Histories.................................

Figure A-2 Typical Hourly Leq’s................................................................................

Figure A-3 Typical Ldn’s............................................................................................

Figure A-4 Community Reaction to New Noise, Relative to Existing Noise in a 

Residential Urban Environment...............................................................

Figure A-5 Community Annoyance Due to Noise.....................................................

2-2

2-3

2-6

2-6

2-7

2-8

2-10

2-11

2-11

2-14

2-15

2-16

2-19

2-19

3-3

3-7

4-7

4-11

4-18

4-20

5-3

5-6

5-13

5-15

5-26

6-2

6-3

6-6

6-8

8-4

9-10

9-12

9-13

9-14

9-17

9-17

9-18

A-5

A-6

A-9

A-12

A-13
LIST OF FIGURES (continued)

Figure A-6 Time History of A-Weighted Sound Level of Maglev at 25 m.......

Figure A-7 Zones of Potential Startle Effect..............................................................

Figure D-1 Overall Vibration Velocity Level for Different High Speed Trains.........

Figure D-2 Best-Fit Curves of Vibration Velocity Level vs Distance........................

Figure D-3 Vibration Velocity vs Distance Calculated from Smoothed 1/3 Octave 

Bands.......................................................................................................

Figure D-4 Comparison of 1/3 Octave Band Spectra.................................................

Figure D-5 Line-Source Transfer Mobility of the Test Sites......................................

Figure D-6 Force Density Functions Derived from Measurements............................

Figure D-7 Projected Vibration Velocity, Transfer Mobility from Site in France......

Figure D-8 Projected Vibration Velocity, Transfer Mobility from Site in Sweden....

Figure D-9 Projected Vibration Velocity, X2000 Force Density................................

A-19

A-21

D-1

D-2

D-3

D-4

D-4

D-5

D-6

D-6

D-7
LIST OF TABLES

Table 2-1 Summary of International Rail Noise Descriptors....................................

Table 3-1 Noise Levels Defining Impact for High Speed Rail Projects...................

Table 3-2 Land Use Categories and Metrics for High Speed Rail Noise Impact 

Criteria......................................................................................................

Table 3-3 Interim Criteria for High Speed Rail Noise Effects on Animals..............

Table 3-4 Noise Impact Criteria: Effect on Cumulative Noise Exposure.................

Table 4-1 Screening Distances for Noise Assessments............................................

Table 4-2 Reference Parameters of 50 Feet from Track/Guideway..........................

Table 4-3 Shielding Corrections for Track Geometry...............................................

Table 4-4 Computation of Noise Exposure at 50 Feet for General Assessment.......

Table 4-5 Estimating Existing Noise Exposure for General Assessment.................

Table 4-6 Sample Noise Impact Inventory Table.....................................................

Table 4-7 Sample Noise Impact Inventory Table........................................

Table 5-1 Noise-Sensitive Land Uses.......................................................................

Table 5-2 Source Reference SELs at 50 Feet...........................................................

Table 5-3 Computation of Shielding: Barriers and Terrain......................................

Table 5-4 Computation of Leq and Ldn......................................................................

Table 5-5 Computation of Excess Shielding: Rows of Buildings and Dense Tree 

Zones......................................................................................................

Table 5-6 High Speed Rail Noise Mitigation Measures............................................

Table 6-1 Human Response to Different Levels of Ground-Borne Noise and 

Vibration................................................................................................

Table 6-2 Factors that Influence Levels of Gournd-Borne Vibration and Noise......

Table 7-1 Ground-Borne Vibration and Noise Impact Criteria.................................

Table 7-2 Ground-Borne Vibration and Noise Impact Criteria for Special Buildings

Table 8-1 Screening Distances for Vibration Assessments.......................................

Table 8-2 Adjustment Factors for Generalized Predictions of Ground-Borne 

Vibration and Noise..................................................................................

Table 10-1 Construction Equipment Noise Emission Levels.....................................

Table 10-2 General Assessment Criteria for Construction Noise...............................

Table 10-3 Detailed Assessment Criteria for Construction Noise..............................

Table 10-4 Vibration Source Levels for Construction Equipment (From Measured 

Data)........................................................................................................

Table A-1 Summary of Noise Levels Associated with Effects on Animals and Birds...

Table C-1 Computation of Lmax for a High-Speed Train Passby using General 

Assessment or Detailed Analysis Method................................................

Table C-2 Computation of SEL for a High-Speed Train Passby from Lmax for 

General Assessment...............................................................................

Table E-1 Noise Source Reference Levels for Conventional Freight Trains (SEL 

at 50 feet)..................................................................................................

2-5

3-4

3-5

3-5

3-6

4-3

4-4

4-6

4-9

4-10

4-15

4-16

5-4

5-10

5-14

5-17

5-18

5-28

6-8

6-9

7-2

7-4

8-2

8-6

10-4

10-7

10-7

10-10

A-24

C-2

C-4

E-2

LIST OF EXAMPLES

Example 4-1 Initial Noise Evaluation Comparing Two High-Speed Rail Alignments..

Example 4-2 Conversion of Specified Lmax to Source Reference Level in SEL.............

Example 5-1 Detailed Noise Projection Procedure........................................................

Example 5-2 Calculation of Lmax using Detailed Noise Analysis Procedure..................

Example 8-1 General Vibration Assessment of a High-Speed Train Alignment...........

4-17

4-21

5-18

5-22

8-12

Chapter 1: Introduction 1-1

CHAPTER 1 - INTRODUCTION

1.1 PURPOSE

This manual provides procedures for the assessment of potential noise and vibration impacts 

resulting from proposed high-speed ground transportation (HSGT) projects, including high-speed 

trains using traditional steel-wheel on steel-rail technology and magnetically levitated (maglev) 

systems1. This document reflects the result of research conducted for the Federal Railroad 

Administration (FRA) and is presented as part of FRA's efforts to promote the consideration of 

HSGT as a transportation option in those intercity corridors where it has the potential to be a cost 

effective and environmentally sound component of the intermodal transportation system. The 

National Environmental Policy Act and related statutes, regulations and orders (NEPA) mandate 

consideration of potential impacts on the human and natural environment as part of the decision 

making process when Federal agencies evaluate proposals to fund or otherwise approve major 

actions. Most states have similar environmental review requirements.

Experience during previous environmental impact reviews of high-speed rail projects has shown that 

possible increases in noise and vibration are frequently among the potential impacts of most concern 

to residents in the vicinity of the proposed project. As the interest in HSGT grows and 

environmental review of HSGT projects are initiated in several locations across the country, it 

becomes clear to FRA that there is a need to provide a standardized set of procedures for the 

evaluation of noise and vibration impacts. There is also a need to provide guidance to promoters and 

designers of HSGT projects on ways in which the design of those projects can incorporate measures 

that address these concerns. And there is a need for providing a means through which public agency 

reviewers of projects can determine where and to what extent the public benefits of HSGT justify 

investment in impact mitigation. This manual attempts to fulfill these needs.

 

1

For brevity, this manual uses the terms “high-speed ground transportation” and “high-speed train” 

interchangeably, both referring to high-speed guided intercity transportation. 
1-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

1.2 ORGANIZATION OF THE MANUAL

This manual is divided into two parts, noise and vibration. Each part has a parallel organization, 

which addresses the following topics:

Topic Noise Vibration

Basic Concepts Chapter 2 Chapter 6

Criteria Chapter 3 Chapter 7

Initial Evaluation Chapter 4 Chapter 8

Detailed Analysis Chapter 5 Chapter 9

Construction Noise/Vibration Chapter 10.1 Chapter 10.2

Documentation Chapter 11 Chapter 11

Appendices

A. Background for Noise Concepts

B. Existing Noise Determination

C. Noise Source Reference Level Determination 

D. Trainset Vibration Measurement Results

E. Freight and Passenger Train Noise Levels

F. Glossary of Terms

G. Background Information for FRA Noise Screening Table
Chapter 2: Basics of High-Speed Train Noise 2-1

CHAPTER 2 - BASICS OF HIGH-SPEED TRAIN NOISE

Noise from high-speed train systems is similar to noise from other rail systems except for a few 

unique features resulting from the higher speeds of travel. The rail systems defined as "high-speed" 

are primarily steel wheeled, both electrically powered and fossil fueled, capable of maximum speeds 

of 125 mph and greater. Noise characteristics of these trains vary considerably as speed increases. 

Consequently, this manual sub-divides these systems into three categories:

• “high-speed,” with a maximum speed of 150 mph,

• “very high-speed,” with a maximum speed of 250 mph, and

• “maglev,” magnetically levitated and powered systems representing the upper range of speed 

performance up to 300 mph. 2

Because ancillary sources are not unique to high speed train systems, noise from electrical 

substations, maintenance facilities, yards, and stations, are not addressed in this manual. These noise 

sources are substantially the same for any type of rail system and do not have characteristics specific 

to high-speed train systems. The methods described in the corresponding transit noise manual from 

Federal Transit Administration are applicable.3 

This chapter discusses the basic concepts of high-speed ground transportation noise to provide 

background for the assessment procedures presented in Chapters 4 and 5. Noise from a ground 

transportation system is often expressed in terms of a Source-Path-Receiver framework. This 

framework is sketched in Figure 2-1 and is central to all environmental noise studies. Each project 

source generates close-by noise levels, which depend upon the type of source and its operating 

characteristics. Then, along the propagation path between all sources and receivers, noise levels are 

 

2Noise from maglev in this manual is based principally on research and test track data from the 

German TransRapid System, currently under development.

3U.S. Department of Transportation, Federal Transit Administration, “Transit Noise and Vibration 

Impact Assessment," Final Report, DOT-T-95-16, April 1995.
2-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

reduced (attenuated) by distance, intervening obstacles, and other factors. Finally, at each receiver, 

noise combines from all sources and may interfere with receiver activities. 

This chapter emphasizes the sources of noise from high-speed trains and, to a lesser extent, the path

component, which includes aspects such as sound attenuation with increasing distance from the 

source, excess attenuation due to atmospheric absorption and ground effects, and acoustic shielding 

by terrain, sound barriers, or intervening buildings. 

In brief, this chapter contains:

• a summary of the noise descriptors used in this manual for high-speed train noise (Section 2.1);

• an overview of noise sources, including a list of major sources specific to high-speed train 

systems and discussion of noise-generation mechanisms (Section 2.2);

• an overview of noise paths, with a discussion of the various attenuating mechanisms on the path 

between source and receiver (Section 2.3);

• a summary of the theoretical models used to predict high-speed train noise, in addition to actual 

measurement data from existing high-speed trains (Section 2.4).

Figure 2-1 The Source-Path-Receiver Framework
Chapter 2: Basics of High-Speed Train Noise 2-3

2.1 NOISE DESCRIPTORS

The universal descriptor used for environmental noise is the A-weighted sound level. It describes 

the level of noise measured at a receiver at any moment in time and is read directly from noisemonitoring equipment, with the weighting switch set on "A." Typical A-weighted sound levels for 

high-speed ground transportation and other sources are shown in Figure 2-2. The high-speed ground 

transportation sources are described further in Section 2.4.

Figure 2-2 Typical A-Weighted Sound Levels 

As shown in Figure 2-2, typical A-weighted sound levels range from the 40s to the 90s, where 40 is 

very quiet and 90 is very loud. The scale in the figure is labeled "dBA" to denote the way Aweighted sound levels are typically written. The letters "dB" stand for "decibels" and refer to the 

general strength of the noise. The letter "A" indicates that the sound has been filtered to reduce the 

strength of very low and very high-frequency sounds, much as the human ear does. Without this 

A-weighting, noise monitoring equipment would respond to events people cannot hear, such as highfrequency dog whistles and low-frequency seismic disturbances. On the average, each A-weighted 

sound level increase of 10 decibels corresponds to an approximate doubling of subjective loudness. 

A summary of fundamentals of noise is given in Appendix A and definitions of acoustical terms are 

given in Appendix F.
2-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

2.1.1 Standard U.S. Noise Descriptors

This manual uses the following single -number descriptors; all based on the A-weighted sound level 

as the fundamental unit, for environmental noise measurements, computations, and assessment:

The Maximum Level (Lmax) during a single noise event. There are two standard ways of 

obtaining the Lmax, one using the "fast" response setting on the sound level meter, or Lmax,f

(obtained by using a 0.125 second averaging time), and the other using the "slow" setting, or 

Lmax,slow (obtained by using a 1 second averaging time). Lmax,fast can occur arbitrarily and is 

usually caused by a single component on a moving train, often a defective component such as 

a flat spot on a wheel. As a result, inspectors from the Federal Railroad Administration use 

Lmax,fast to identify excessively noisy locomotives and rail cars during enforcement of Railroad 

Noise Emission Compliance Regulations.4 Lmax,slow, with its greater averaging time, tends to 

de-emphasize the effects of non-representative impacts and impulses and is generally better 

correlated with the Sound Exposure Level (SEL), defined below, which is the basis of impact 

assessment. Thus, Lmax,slow is typically used for modeling train noise mathematically. In 

general, however, the Lmax descriptor in either form is not recommended for noise impact 

assessment. Because it is used in vehicle -noise specifications and commonly measured for 

individual vehicles, equations are included in Appendix C to convert between Lmax,slow and the 

cumulative descriptors described below. 

The Sound Exposure Level (SEL) describes a receiver's cumulative noise exposure from a 

single noise event. It is represented by the total A-weighted sound energy during the event, 

normalized to a one-second interval. It is the primary descriptor of high-speed rail vehicle 

noise emissions and an intermediate value in the calculation of both Leq and Ldn (defined 

below).

The Hourly Equivalent Sound Level [Leq(h)] describes a receiver's cumulative noise 

exposure from all events over a one-hour period. The underlying metric for calculating Leq(h) 

from single noise events during a one-hour period is SEL. Leq(h) is used in this manual to 

assess noise for non-residential land uses. For assessment, Leq is computed for the loudest 

operating hour during the hours of noise-sensitive activity.

The Day-Night Sound Level (Ldn or DNL) describes a receiver's cumulative noise exposure 

from all events over a 24-hour period. The basic unit used in calculating Ldn is the Leq(h) for 

each one-hour period. It may be thought of as a noise exposure, totaled after increasing all 

nighttime A-Levels (between 10 p.m. and 7 a.m.) by 10 decibels. Every noise event during 

 

4U.S. Department of Transportation, Federal Railroad Administration, “Railroad Noise Emission 

Compliance Regulations,” Final Rule, 48 Federal Register 56756 - 56761; December 23, 1983 (23 Code of 

Federal Regulations 210).
Chapter 2: Basics of High-Speed Train Noise 2-5

the 24-hour period increases this exposure, louder events more than quieter events, and events 

that are of longer duration more than briefer events. In this manual, Ldn is used to assess noise 

for residential land uses. Typical community Ldns range from about 50 to 70 dBA, where 50 

represents a quiet noise environment and 70 is a noisy one. 

Detailed definitions and mathematical representations of all of these noise descriptors are presented 

in Appendix A. 

2.1.2 Other Noise Descriptors

Noise from high-speed ground transportation systems is often measured, reported or referred to in 

terms of other descriptors used primarily in Europe and Japan. These descriptors are slightly 

different in their mathematical definitions from the U.S. descriptors listed above. To avoid 

confusion with the descriptors used in this manual, Table 2-1 provides a partial list of these 

descriptors and a brief definition of each. Mathematical definitions to assist the user to translate data 

to the descriptors in this manual are provided in Appendix A.

Table 2-1 Summary of International Rail Noise Descriptors

Metric Abbreviation(s) Country Definition

Laeq,P or Lp,p Germany, France

A-weighted Passby Level

Lmax(mean) Scandinavia

Equivalent A-weighted soundpressure level, energy-averaged over 

the time of passby (train length).

One-Hour Leq Laeq,1h or Lp,1h Germany, France Sound-pressure level, energyaveraged over one hour.

Average A-weighted 

Maximum Level LAmax Japan

Power-averaged "slow" maximum 

level (Lmax,s) of 20 consecutive train 

passbys.

Sound Exposure Level LAE Japan

Power-averaged value of sound 

exposure within 10 dB of LAmax, 

sampled at a time interval of 5/3 sec.

2.1.3 The Lmax-SEL Relationship

To help the reader gain a preliminary understanding of high-speed ground transportation noise 

descriptors and the interrelationships among descriptors, the following discussion illustrates how 

SEL, the fundamental descriptor used in calculating noise exposure, from single events, relates to 

Lmax. Both descriptors characterize a single noise event; however, they do not always correlate with 

each other. 

The Lmax for a typical high-speed train passby is identified in Figure 2-3, where time is plotted 

horizontally and A-weighted sound level is plotted vertically. The event shown represents a 

measured time signature of a TGV passby at 180 mph at 82 feet (25 meters).
2-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Figure 2-4 Typical Longer-Duration High-Speed Train Event

The noise exposure that occurred during a high-speed train passby, is shaded in Figure 2-3. This 

exposure represents the total amount of sound energy that enters the receiver's ears (or the measurement 

microphone) during the passby. A noise event of longer duration, a Eurostar train passby at 90 mph, is 

shown in Figure 2-4. For this event, the noise exposure is large due to duration. Since the Eurostar train 

is nearly two times as long as the standard TGV trains, both the added length and slower speed contribute 

to the increased duration of the Eurostar event. Compared with the event in Figure 2-3, the Lmax is 4 dBA 

lower, but the measured SELs are the same. 

Figure 2-3 Typical High-Speed Train Passby
Chapter 2: Basics of High-Speed Rail Noise 2-7

The time histories in Figures 2-3 and 2-4, but with a stretched vertical scale are repeated in Figure 2-5. 

The stretched scale corresponds to a linear scale of sound pressure, or energy, at any moment in time. 

Mathematically, sound energy is proportional to 10 raised to the (L/10) power, that is, 10(L/10). The 

stretched vertical scale represents noise exposure as energy exposures. Only when plotted at this 

stretched scale do the shaded zones properly correspond to the noise exposures that underlie the SEL. 

The shaded zones in the two frames have equal areas, corresponding to equal noise exposures for these 

two very different noise events.

Each frame of the figure also contains a tall, thin shaded zone of one-second duration. This tall zone is 

the way to envision SELs. In the tall zone, the original shaded zone has been squeezed shorter and 

shorter in time, while retaining the same area. As its duration is squeezed, its height increases to keep the 

area constant. If a noise exposure shading is squeezed to a duration of one second, its height will then 

equal its SEL value; mathematic ally, its area is now 10(L/10) times one second. Note that the resulting 

height of the squeezed zone depends both upon the Lmax and the duration of the event – that is, upon the 

total area under the original, time-varying A-weighted sound level. 

Figure 2-5 An “Energy” View of Noise Events
2-8 High-Speed Ground Transportation Noise and Vibration Impact Assessment

2.1.4 Onset Rate

An important characteristic of the noise from high-speed rail systems is the onset rate of the sound 

signature. Onset rate is the average rate of change of increasing sound pressure level in decibels per 

second (dB/sec) during a single noise event. The rapid approach of a high-speed train is accompanied by 

a sudden increase in noise for a receiver near the tracks. Researchers report that sounds of approaching 

vehicles carry a sense of convergence and cause greater annoyance than receding sounds.5 Moreover,

sounds with fast onset rates are more annoying than sounds with less rapid variation or steady noise with 

the same maximum noise level.6 Research by the U.S. Air Force on the effect of onset rate on aircraft 

noise annoyance shows that people are increasingly annoyed by sudden sounds with onset rates greater 

than about 15 dB per second (dB/sec), as described more fully in Appendix A.7,8 Onset rates of greater 

than 15 dB/sec occur for receivers within 60 feet of a 150 mph train, and occur at greater distances for 

trains at higher speeds. Measured onset rates for a steel wheel train (ICE) and a maglev train (TR 07) are 

shown plotted for the ratio of speed to distance in Figure 2-6. The plot shows that onset rate:

• increases as speed increases for a given distance, and

• decreases as distance increases for a given speed.

 

5G. Rosinger, D. W. Nixon and H.E. von Gierke, “Quantification of the Noisiness of ‘Approaching’ and 

‘Receding’ Sounds,” J. Acoust. Soc. Am., 48, pp. 843-853, October 1970.

6K. Plotkin, L.C. Sutherland, J.A. Molino, “Environmental Noise Assessment for Military Aircraft Training 

Routes: Volume 2: Recommended Noise Metric.” Wyle Laboratories Report WR 86-21 prepared for WrightPatterson Air Force Base AAMRL/BBE, April 1987.

7K.J. Plotkin, K. W. Bradley, J.A. Molino, K.G. Helbing, D.A. Fisher. “The Effect of Onset Rate on 

Aircraft Noise Annoyance, Vol. 1: Laboratory Experiments,” US Air Force Systems Command, Report Number 

AL-TR-1992-0093, May 1992.

8

E. Stusnick, K.A. Bradley, J.A. Molino, and G. deMiranda. “The Effect of Onset Rate on Aircraft Noise 

Annoyance, Vol. 2: Rented Home Experiment.” US Air Force Materiel Command, Report Number AL/OE-TR1993-0170, October 1992.

Figure 2-6 Measured High-Speed Rail Onset Rates
Chapter 2: Basics of High-Speed Rail Noise 2-9

Although the measured onset rates in Figure 2-6 do not exceed about 25 dB/sec at normal measurement 

distances, actual onset rates can rise to greater values close to the tracks. When onset rates exceed about 

30 dB/sec people tend to be startled, or surprised by the sudden onset of the sound. Startle as an added 

factor in annoyance is discussed in Appendix A-4. The onset rate of 30 dB/sec is used as the basis for 

establishing distances within which startle is likely to occur and serves as added information in the impact 

assessment methods presented in Chapters 4 and 5.

2.2 SOURCES OF HIGH-SPEED TRAIN NOISE

The total wayside noise generated by a high-speed train passby consists of several individual noisegenerating mechanisms, each with its own characteristics of source location, strength, frequency content, 

directivity, and speed dependence. These noise sources can be generalized into three major regimes:9

Regime I. propulsion or machinery noise,

Regime II. mechanical noise resulting from wheel/rail interactions and/or guideway vibrations, 

and

Regime III. aerodynamic noise resulting from airflow moving past the train.

For a conventional train with a maximum speed of up to about 125 mph, propulsion and mechanical noise 

are sufficient to describe the total wayside noise. The aerodynamic noise component begins to be an 

important factor when the train speed exceeds about 160 mph.

The significance of these different regimes is that, for a given train, there are three distinct speed ranges in 

which only one sound source dominates the total noise level. The dependence of the A-weighted sound 

level on vehicle speed (S) for a typical high-speed train is illustrated in Figure 2-7. A qualitative 

indication of the maximum sound level during a passby is plotted vertically in this figure. The three 

speed regimes are labeled "I," "II," and "III," each corresponding to the dominant sound source in the 

regime, or propulsion, mechanical, and aerodynamic noise, respectively. The speed at which the 

dominant sound source changes from one to another is called an acoustical transition speed (vt). The 

transition from propulsion noise to mechanical noise occurs at the lower acoustical transition speed (vt1), 

and the transition from mechanical to aerodynamic noise occurs at the upper acoustical transition speed 

(vt2). 

The various noise sources for a steel-wheeled high-speed tracked system and maglev system are 

illustrated in Figures 2-8 and 2-9 respectively. These sources differ in where they originate on the train 

and in what frequency range they dominate. 

 

9

B. Barsikow and B. Müller, “Wayside noise generated by the German high-speed transport systems, ICE 

and Transrapid,” 72nd Annual Meeting of the Transportation Research Board, Washington, D.C., 1993.
2-10 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Figure 2-7 Generalized Sound Level Dependence on Speed

2.2.1 Regime I: Propulsion Sources

Steel-Wheeled Trains. At low speeds, Regime I, propulsion mechanisms, or machinery and auxiliary 

equipment that provide power to the train are the predominant sound sources. Most high-speed trains are 

electrically powered; the propulsion noise sources are, depending on the technology, associated with 

electric traction motors or electromagnets, control units, and associated cooling fans (see Figure 2-8). 

Fans can be a major source of noise; on conventiona l steel-wheeled trains fans are usually located near 

the top of the power units, about 10 feet above the rails. Fan noise tends to dominate the noise spectrum 

in the frequency bands near 1000 Hz. External cooling fan noise tends to be constant with respect to train 

speed, which makes fans the dominant noise when a train is stopped in a station.

Maglev Trains. Noise from the propulsion magnets in a maglev system is a result of induced vibration 

from magnetic forces. One source of vibration is oscillating magnetostriction, which also causes the 

characteristic hum sometimes heard from electrical transformers and which is likely to be tonal in 

character (see Figure 2-9). Sound at the magnetic pole-passing frequency is another effect of magnetic 

traction; the interaction of the moving vehicle and the stationary magnetic poles at a uniform spacing 

causes a tonal sound that varies uniformly with velocity. These forces are located at the magnet gaps 

between the vehicle and the guideway. Propulsion noise in general has a relatively weak speed 

dependence, typically following a relationship of ten times the logarithm of speed. 
Chapter 2: Basics of High-Speed Rail Noise 2-11

Figure 2-8 Noise Sources on a Steel-Wheeled High-Speed Rail System

Figure 2-9 Noise Sources on a Maglev System
2-12 High-Speed Ground Transportation Noise and Vibration Impact Assessment

2.2.2 Regime II: Mechanical/Structural Sources

Steel-Wheeled Trains. The effects of wheel-rail interaction of high-speed trains, guideway structural 

vibrations, and vehicle -body vibrations fall into the category of mechanical noise sources. These sources 

tend to dominate the total noise level at intermediate speeds (Regime II), and cover the widest of the three 

speed regimes. For steel-wheeled trains, wheel-rail interaction is the source of the rolling noise radiated 

by steel wheels and rails caused by small roughness elements in the running surfaces. This noise source 

is close to the trackbed with an effective height of about 2 feet above the rails. The spectrum for rolling 

noise peaks in the 2 kHz to 4 kHz frequency range, and it increases more rapidly with speed than does 

propulsion noise, typically following the relationship of 30 times the logarithm of train speed. Wheel-rail 

noise typically dominates the A-weighted sound level at speeds up to about 160 mph. 

Maglev Trains. Maglev technology is not free from mechanical/structural noise sources despite the lack 

of physical contact with the guideway. The maglev analogies to wheel-rail noise from a steel-wheeled 

train are noise from wheels rolling on guideway support surfaces at low speeds for electrodynamic (EDS) 

systems, which require forward motion up to a certain speed before lift can occur, and noise from

magnetic pole-passing. Sound also is radiated by guideway vibrations and vehicle body vibrations. Both 

of these sources tend to radiate sounds at relatively low acoustical frequencies; fundamental resonance 

frequencies of guideway support beams are generally below 10 Hz, with radiation from box beam panels 

up to about 80 Hz. Vehicle body vibrations depend on the details of body panel construction; they can 

result in substantial sound radiation throughout the audible range. For maglev systems, the combination 

of all mechanical sources results in an increase of noise approximately 40 times the logarithm of speed. 

2.2.3 Regime III: Aerodynamic Sources

Propulsion and rolling noise are generally sufficient to describe the total noise up to speeds of about 160 

mph for steel-wheeled trains. Above this speed, however, aerodynamic noise sources tend to dominate 

the radiated noise levels. These sources begin to generate significant noise at speeds of about 180 mph, 

depending on the magnitude of the mechanical/structural noise. For maglev, this transition occurs at a 

lower speed due to low levels of mechanical noise.

Steel-Wheeled Trains. Aerodynamic noise is generated from high-velocity airflow over the train. For a 

conventional steel-wheeled train, the components of aerodynamic noise are generated by unsteady flow 

separations at the front and rear of the train and on structural elements of the train (mainly in the regions 

encompassing the trucks, the pantograph, inter-coach gaps, and discontinuities along the surface), and a 

turbulent boundary layer generated over the entire surface of the train. 

Maglev Trains. For a maglev vehicle, aerodynamic noise sources include the flow separation on the 

front and rear ends, vortex shedding from the antennae, flow interactions in the gap between the vehicle 

and guideway, the wake generated at the trailing end, and the turbulent boundary layer. 

Aerodynamic sources generally radiate sound in the frequency bands below 500 Hz, generally described 

as a rumbling sound. Aerodynamic noise level increases with train speed much more rapidly than does 

propulsion or rolling noise, with typical governing relationships of 60 to 70 times the logarithm of speed.
Chapter 2: Basics of High-Speed Rail Noise 2-13

2.3 SOUND PROPAGATION PATH

This section contains a qualitative overview of noise-path characteristics from source to receiver, 

including attenuation along these paths. Sound paths from source to receiver are predominantly air-borne. 

Along these paths, sound reduces with distance due to (1) divergence , (2) absorption/diffusion, and (3) 

shielding. The general equation for the prediction of the A-weighted sound level at various distances 

from the track can be expressed as follows:

LA = LA(ref) + Cd + Ca + Cg + Cb

where: LA(ref) = a known A-weighted sound level at some reference distance ref from the source

Cd = adjustment factor for attenuation due to divergence

Ca = adjustment factor for excess attenuation due to atmospheric absorption

Cg = adjustment factor for excess attenuation from ground absorption

Cb = adjustment factor for excess attenuation due to obstacles such as barriers, berms, and 

buildings.

In nearly all cases, the adjustment factors are negative numbers due to the nature of the reference 

conditions. Each of these adjustment factors are discussed in Sections 2.3.1-2.3.3 in terms of their 

mechanisms of sound attenuation. Specific equations for computing noise-level attenuations along 

source-receiver paths are presented in Chapters 4 and 5. Sometimes a portion of the source-to-receiver 

path is not through the air, but rather through the ground or through structural components of the 

receiver's building. Ground-borne and structure-borne noise propagation are discussed in Chapter 6. 

2.3.1 Divergence

Sound levels naturally attenuate with distance. Such attenuation, technically called “divergence,” 

depends upon source configuration and source-emission characteristics. Divergence is shown graphically 

for point sources and line sources separately in terms of how they attenuate with distance in Figure 2-10. 

The divergence adjustment factor, Cd, for the receiver is plotted vertically relative to the sound level 50 

feet from the source. As shown, the sound level attenuates with increasing distance due to the geometric 

spreading of sound energy. 

For sources grouped closely together (called point sources), attenuation with distance is large: 6 decibels 

per doubling of distance. Most individual noise sources on a moving high-speed rail vehicle radiate 

sound as point sources. When many point sources are arrayed in a line, all radiating sound at the same 

time so any one source is not distinguishable, the arrangement is called a line source. For line sources, 

divergence with distance is less: 3 decibels per doubling of distance for Leq and Ldn, and 3 to 6 decibels 

per doubling of distance for Lmax. A train passing along a track or guideway can be considered a line 

source. In Figure 2-10, the line source curve separates into three separate lines for Lmax, with the point of 

departure depending on the length of the line source. For example, close to a short train, it behaves like a 

line source; far away, it behaves as a point source. The curves shown in Figure 2-10 are for illustrative 

purposes only, and the exact equations for these curves given Chapter 5 should be used for quantitative 

analyses.
2-14 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Some sound sources, such as warning bells, radiate sound energy nearly uniformly in all directions. 

These are called nondirectional, or monopole , sources. For train noise, however, the rolling noise from 

wheel-rail interactions, as well as some types of aerodynamic noise, is complicated because the sources 

do not radiate sound equally well in all directions. This unequal radiation is known as source directivity, 

which is a measure of the variation in a source's radiation with direction. Studies have shown that wheelrail noise can be modeled by representing the source as a line source (or continuous row of point sources) 

with dipole directivity. 10 A dipole radiation pattern has also been observed in the turbulent boundary 

 

10E.J. Rathe, “Railway noise propagation,” J. Sound Vib. 51, 371-388 (1977).

Figure 2-10 Attenuation due to Distance (Divergence)
Chapter 2: Basics of High-Speed Rail Noise 2-15

layer near the sides of a train.11 Typically, a dipole source radiates a directivity pattern such that the 

sound pressure is proportional to the cosine of the angle between the source orientation and the receiver. 

Consequently, wheel-rail noise is propagated more efficiently to either side of a moving train than in 

front, above or behind it. 

2.3.2 Absorption/Diffusion

In addition to the attenuation from geometric spreading of the sound energy, sound levels are further 

attenuated when sound paths lie close to absorptive or "soft" ground, such as freshly plowed or 

vegetation-covered areas. This additional attenuation, which can be 5 decibels or more within a few 

hundred feet, is illustrated graphically in Figure 2-11. In this figure the adjustment factor, Cg, is plotted 

vertically as a function of distance. At very large distances, wind and temperature gradients can alter the 

ground attenuation shown here; such variable atmospheric effects generally influence noise levels well 

beyond the range of typical railway noise impact and are not included in this manual. Equations for the 

curves in Figure 2-11 are presented in Chapter 5.

Figure 2-11 Attenuation due to Soft (Sound-Absorptive) Ground

2.3.3 Shielding

Sound paths are sometimes interrupted by noise barriers, by terrain, by rows of buildings, or by 

vegetation. Noise barriers, usually the most effective means of mitigating noise in sensitive areas, are the 

most important of these path interruptions. A noise barrier reduces sound levels at a receiver by breaking 

the direct path between source and receiver with a solid wall; vegetation, in contrast, hides the source but 

does not reduce sound levels significantly. Sound energy reaches the receiver only by bending 

(diffracting) over the top of the barrier, as shown in Figure 2-12. This diffraction reduces the sound level 

at the receiver.

 

11W.F. King, “On the boundary layer contribution to wayside noise generated by high-speed tracked 

vehicles,” Inter-Noise ‘94 Proceedings (1994), pp.175-180.
2-16 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Figure 2-12 Noise Barrier Geometry

Noise barriers for transportation systems typically attenuate noise at the receiver by 5 to 15 dBA (which 

corresponds to an adjustment factor Cb range of -5 to -15 dBA), depending upon receiver and source 

height, barrier height, length, and distance from both source and receiver. The attenuation of noise by a 

barrier also is frequency dependent, i.e., all other factors being the same, the higher the frequency of the 

noise, the greater the barrier attenuation. As discussed in Section 2.2, the peak frequencies and source 

heights of high-speed ground transportation noise vary according to the dominant noise source in a 

particular speed regime. In general, aerodynamic noise has lower peak frequencies than does wheel-rail 

noise, which means that a barrier is less effective at attenuating aerodynamic noise. In addition, 

aerodynamic noise sources tend to be located higher up on the train than wheel-rail noise sources. As a 

result, a noise barrier high enough to shield aerodynamic noise will be relatively expensive compared to a 

barrier for controlling wheel-rail noise, since it must extend 15 feet or more above the top of rail. For 

operating speeds up to about 160 mph, a barrier high enough to shield wheel-rail and other lower car body 

sound sources would normally provide sufficient sound attenuation. 

Barriers on structure, very close to the source, provide less attenuation than predicted using standard 

barrier attenuation formulae, due to reverberation (multiple reflections) between the barrier and the body 

of the train. This reverberation can be offset by increased barrier height, which is easy to obtain for such 

close barriers, and/or the use of acoustically absorptive material on the source side of the barrier. These 

concepts are illustrated in Figure 2-12. Acoustical absorption is included as a mitigation option in 
Chapter 2: Basics of High-Speed Rail Noise 2-17

Chapter 5. Equations for barrier attenuation, as well as equations for other sound-path interruptions, also 

are presented in Chapter 5.

2.4 MATHEMATICAL MODEL OF HIGH-SPEED TRAIN NOISE

The development of the high-speed ground transportation noise prediction model consists of two distinct 

parts: (1) identification of sources, and (2) modeling of the outdoor sound propagation. Part (1) involves 

the identification and localization of sound sources specific to high-speed trains, and is based solely on 

empirical data. Section 2.4.1 presents an overview of the available data used to quantify these sources. 

Part (2) involves the application of sound propagation theory to account for characteristics of the noise 

path. Section 2.4.2 provides a summary of the mathematical models used to predict sound levels at 

specific locations.

2.4.1 Identification of Sources

Most of the data used to develop the high-speed ground transportation noise model are taken from 

measurements of revenue service high-speed train operations in Europe.12 These measurements of 

electrically powered trains include the TGV and Eurostar trains in France, the X2000 tilt train in Sweden, 

and the Pendolino tilt train in Italy. The purpose of the measurement program was to document wayside 

noise levels from representative European high-speed trainsets, with the specific objective of developing a 

prediction model for high-speed ground transportation noise. In addition, an existing database of noise 

measurements from the U.S. Northeast Corridor (NEC) Electrification Project 13, the National Maglev 

Initiative (NMI) Project 14, and various other sources, provide supplementary data on ICE (Germany), 

TGV, X2000, RTL-2 (gas-turbine powered), and TR07 (German maglev trainsets). These data are 

supplemented by recent measurements of the Acela 15, non-electric locomotive (gas-turbine powered) 16, 

and an updated version of the German maglev train TR0817.

As an overview of the available data, measured noise levels from the various high-speed trainsets are 

plotted over a range of speeds in Figures 2-13 and 2-14. A graph of Lmax,fast as a function of train speed, 

normalized to a reference distance of 100 feet is shown in Figure 2-13. Figure 2-14 shows the noise level 

 

12U.S. Department of Transportation, Federal Railroad Administration, Summary of European High-Speed 

Rail Noise and Vibration Measurements, DTFR53-94-A-00056, December 1998.

13U.S. Department of Transportation, Federal Railroad Administration, Northeast Corridor Improvement 

Project Electrification -New Haven,CT to Boston, MA: Final Environmental Impact Statement/Report, Volume II: 

Technical Studies , Chapter 4. Noise and Vibration. DOT/FRA/RDV-94/01-B, DOT-VNTSC-FRA-94-6, Final 

Report October 1994.

14U.S. Department of Transportation, Federal Railroad Administration, Noise from High Speed Maglev 

Systems, DOT/FRA/NMI-92/18, January 1993.

15U.S. Department of Transportation, Federal Railroad Administration, Noise Characteristics of Northeast 

Corridor High-Speed Trainsets, DTFR53-94-A-00060, September 2000.

16U.S. Department of Transportation, Federal Railroad Administration, High-Speed Non-Electric 

Locomotive Noise Measurements, HMMH Report 298240, DTFR53-98-D-00004, October 2001.

17U.S. Department of Transportation, John A. Volpe National Transportation Systems Center, Noise 

Characteristics of the Transrapid TR08 Maglev System, DOT-VNTSC-FRA-02-13, July 2002.
2-18 High-Speed Ground Transportation Noise and Vibration Impact Assessment

plotted in terms of SEL, with the data normalized to a reference distance of 100 feet and a reference train 

length of 740 feet. Data from the following test programs are represented in these figures:

• Revenue service operations in Europe. Data from the European measurement program conducted in 

France, Italy and Sweden referred to above are plotted as individual data points in the graphs. Each 

data point represents a large quantity of data averaged over similar speed events. Sites were selected 

to cover a relatively wide speed range. They include operations of the TGV and Eurostar in France, 

Pendolino in Italy, and X2000 in Sweden.

• Maglev test track in Germany. TR08 noise curve is based on regression analysis of data obtained 

from tests on a prototype maglev vehicle (TransRapid TR08) at the maglev test track in Emsland, 

Germany.

• Trainset demonstrations on NEC. Curves of noise level versus speed generated by the noise model 

developed as part of the NEC Electrification Project are included.18 These curves are based on 

measurements conducted on the Northeast Corridor as part of demonstration testing of several newertechnology trainsets (including the German ICE, Swedish X2000, and the U.S./French RTL-2 

Turboliner) in the U.S. The curves are plotted up to the actual maximum speed obtained for each 

trainset during testing, even though the maximum allowable speed may be higher.

• Acela compliance tests. Noise measurements were conducted during compliance testing at the 

Transportation Technology Center in Colorado.

The results in Figures 2-13 and 2-14 indicate that the European steel-wheeled train measurement data 

generally fall within the range of the train noise curves developed for the NEC Project. The results also 

suggest that:

ÿ The TGV trains tested in Europe have noise emissions similar to the ICE and RTL-2 trains tested in 

the U.S. 

ÿ Wayside noise levels for the X2000 and Pendolino trains averaged about 5 decibels higher than other 

trains measured, with noise emissions similar to the X2000 train tested in the U.S.

ÿ Data for the Eurostar trains showed the greatest variation, with noise levels scattered over the range 

for other trains.

Maglev noise levels are consistently low relative to the steel-wheeled trains, but it is clear that as 

speeds reach the upper limits there is less difference between the steel-wheeled and the maglev 

technologies in the level of noise generated as the aerodynamic component becomes significant.

 

18Because the NEC noise models were developed with less detailed consideration of noise subsources and 

propagation effects, they do not necessarily yield identical results as computed using the more updated models 

presented in Chapters 4 and 5 of this manual.
Chapter 2: Basics of High-Speed Rail Noise 2-19

Figure 2-13 Measured Values of Lmax, s vs Speed from High-Speed Trains

Figure 2-14 Measured Values of SEL vs Speed from High-Speed Trains
2-20 High-Speed Ground Transportation Noise and Vibration Impact Assessment

2.4.2 Basic Equations

The general approach used to model noise from high-speed trains considers each noise source from a train 

passby separately as a moving line source of given length, height, speed dependence, and directivity 

pattern. The standard model for noise from wheel-rail interactions is an incoherent dipole line source.9 

Most other sources, such as propulsion and aeroacoustic mechanisms, can be modeled as having simple 

monopole directivity.19,20

Since the noise impact criteria are based on noise exposure metrics Leq and Ldn , the noise computations 

are based on a reference SEL for each source corresponding to a set of reference operating conditions. 

Since Lmax is often the quantity that is measured or provided in vehicle noise specifications, it is important 

to understand the relationship between Lmax and SEL. The following equations based on Rathe’s model9

can be used to relate SEL to Lmax under reference conditions:

for dipole sources

for monopole sources

where:

 

19

 The radiating parts of aerodynamic noise such as the pantograph and the turbulent boundary layer near 

the wall can originate from dipole -like sources. However, because of the turbulent nature of the sound-generating 

mechanisms, the directions of the axes of dipoles are likely to vary in time and position, resulting in a more or less 

randomly radiating chaos of fluctuating dipoles. Thus, the global directivity pattern of a train is more appropriately 

modeled as a monopole, even though the sources may be dipoles locally.

20J.D. van der Toorn, H. Hendriks, T.C. van den Dool, “Measuring TGV source strength with 

SYNTACAN,” J. Sound Vib. 193(1), 1996, p. 113-121.

SEL L { }

len

v

= max +











10log  −10log 2a+sin(2a) +3.3

SEL L ( )

len

v

= max +











10log  − 10 log 2a + 3.3

( )

L v

len

v

y

max ref

len

y

=

=

=

=

=

−

reference L under reference conditions ( , y ), dBA,

reference source length, feet,

reference train speed, mph,

, radians, and

reference observer distance from track centerline, feet.

max,s ref

a tan 1

2
Chapter 2: Basics of High-Speed Rail Noise 2-21

Reference conditions are given in tables in Chapters 4 and 5. The following equation is then used to 

adjust a reference SEL to other operating conditions at the reference distance y:

where:

SEL and Lmax are descriptors of noise levels from a single train passby. The following equations are used 

to predict noise exposure in terms of the cumulative metrics Leq(h) and Ldn, and to adjust for divergence 

and the effects of the propagation path:

where:

Methods for calculating the correction factors Cd, Cg, and Cs are based on source type, receiver distance, 

and cross-sectional geometry are presented in Chapters 4 and 5. 

SEL SEL len

len

K

v

v

ref

ref ref

= +

















+

















10 log log

len

K

v

=

=

=

source length, feet,

speed coefficient, and

train speed, mph.

L h SEL V C C C

L

eq d g b

dn

Leq day Leq night

( ) log( ) .

log .

( ) ( )

= + + + + −

= × + ×

















−

























+

10 35 6

10 15 10 9 10 13 8

10

10

10

V

C

C

C

L day L h

L night L h

d

g

b

eq eq

eq eq

=

=

=

=

=

=

hourly volume of train traffic, in trains per hour

correction for divergence (distance attenuation), dB

correction for ground attenuation, dB

correction for excess shielding due to barriers or berms, dB

daytime L , or energy - average during daytime hours (7 a. m. to 10 p.m.)

nighttime L or energy - average during nighttime hours (10 p.m. to 7 a.m.)

eq

eq

( ) ( )

( ) , ( )
2-22 High-Speed Ground Transportation Noise and Vibration Impact Assessment
Chapter 3: Noise Impact Criteria 3-1

CHAPTER 3 - NOISE IMPACT CRITERIA

The criteria used in evaluating noise impacts from high-speed ground transportation are based on 

maintaining a noise environment considered acceptable for land uses where noise may have an effect. 

These criteria take into account the unusual noise characteristics of high-speed rail operations, including 

the effects of startle on humans, livestock, and wildlife to the extent that these effects are known. 

The noise impact criteria for high-speed ground transportation facilities are presented in Section 3.1. 

These criteria are adapted from criteria developed by the Federal Transit Administration for rail noise 

sources operating on fixed guideways or at fixed facilities.21 The criterion for the onset of moderate

impact varies according to the existing noise level and the predicted project noise level, and it is 

determined by the minimum measurable change in community reaction. The corresponding criterion for 

severe impact also varies according to the existing noise level as well as the project noise level, but it is 

determined by the change in community reaction between an acceptable and an unacceptable noise 

environment. Guidelines for the application of the criteria are included in Section 3.2, and background 

material on the development of the criteria is included in Appendix A.

3.1 NOISE IMPACT CRITERIA FOR HIGH SPEED RAIL PROJECTS

The noise impact criteria for high-speed ground transportation projects are shown in graphs and tables in 

this section. The equations used to define these criteria are included in Appendix A. The criteria apply to 

high-speed train operations as well as to fixed facilities such as storage and maintenance yards, passenger 

stations and terminals, parking facilities, and substations.

3.1.1 Basis of Noise Impact Criteria

The noise impact criteria for human annoyance, presented in Figure 3-1 and Table 3-1, are based on 

comparison of the existing outdoor noise levels and the future outdoor noise levels from a proposed highspeed train project. They incorporate both absolute criteria, which consider activity interference caused 

by the high-speed train project alone, and relative criteria, which consider annoyance due to the change in 

the noise environment caused by the project. These criteria were developed to apply to a wide variety of 

 

21U.S. Department of Transportation, Federal Transit Administration. “Transit Noise and Vibration Impact 

Assessment,” Final Report, DOT-T-95-16, April 1995.
3-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

surface transportation modes, to recognize the heightened community annoyance caused by late-night or 

early-morning operations, and to respond to the varying sensitivities of communities to projects under 

different background noise conditions.

The noise criteria and descriptors for human annoyance depend on land use, as defined in Table 3-2. 

Further guidance on the definition of land use, the selection of the appropriate noise metric, and the 

application of these criteria are given in Section 3.2, with more detailed guidelines provided in Chapters 4 

and 5.

Noise effects on livestock and wildlife also have been considered. There are no established criteria 

relating high-speed train noise and animal behavior. However, some characteristics of high-speed train 

noise are similar to low overflights of aircraft, and researchers generally agree that high noise levels from 

aircraft overflights can have a disturbing effect on both domestic livestock and wildlife. Some animals get 

used to noise exposure, while some do not. Documented effects range from simply taking notice and 

changing body position to taking flight in panic. Whether these responses represent a threat to survival of 

animals remains unclear, although panic flight may result in injuries to animals in rough terrain or in 

predation of unprotected eggs of birds. A limited amount of quantitative noise data relating actual levels 

to effects provides enough information to develop a screening procedure to identify areas where noise 

from high speed train operations could affect domestic and wild animals. The basis for the screening is 

shown in Table 3-3. A summary of recent literature related to noise effects on livestock and wildlife is 

included in Appendix A. 
Chapter 3: Noise Impact Criteria 3-3

Figure 3-1 Noise Impact Criteria for High Speed Rail Projects
3-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Table 3-1 Noise Levels Defining Impact for High Speed Train Projects

Project Noise Impact Exposure,* Leq(h) or Ldn (dBA)

Category 1 or 2 Sites Category 3 Sites

Existing Noise 

Exposure*

Leq(h) or Ldn

(dBA) No Impact Moderate

Impact Severe Impact No Impact ModerateImpact Severe Impact

<43 < Ambient+10 Ambient +

10 to 15 >Ambient+15 <Ambient+15 Ambient +15 to 20 >Ambient+20

43 <52 52-58 >58 <57 57-63 >63

44 <52 52-59 >59 <57 57-64 >64

45 <52 52-59 >59 <57 57-64 >64

46 <52 52-59 >59 <57 57-64 >64

47 <52 52-59 >59 <57 57-64 >64

48 <53 53-59 >59 <58 58-64 >64

49 <53 53-59 >59 <58 58-64 >64

50 <53 53-60 >60 <58 58-65 >65

51 <54 54-60 >60 <59 59-65 >65

52 <54 54-60 >60 <59 59-65 >65

53 <54 54-60 >60 <59 59-65 >65

54 <55 55-61 >61 <60 60-66 >66

55 <55 55-61 >61 <60 60-66 >66

56 <56 56-62 >62 <61 61-67 >67

57 <56 56-62 >62 <61 61-67 >67

58 <57 57-62 >62 <62 62-67 >67

59 <57 57-63 >63 <62 62-68 >68

60 <58 58-63 >63 <63 63-68 >68

61 <58 58-64 >64 <63 63-69 >69

62 <59 59-64 >64 <64 64-69 >69

63 <60 60-65 >65 <65 65-70 >70

64 <60 60-66 >66 <65 65-71 >71

65 <61 61-66 >66 <66 66-71 >71

66 <61 61-67 >67 <66 66-72 >72

67 <62 62-67 >67 <67 67-72 >72

68 <63 63-68 >68 <68 68-73 >73

69 <64 64-69 >69 <69 69-74 >74

70 <64 64-69 >69 <69 69-74 >74

71 <65 65-70 >70 <70 70-75 >75

72 <65 65-71 >71 <70 70-76 >76

73 <65 65-72 >72 <70 70-77 >77

74 <65 65-72 >72 <70 70-77 >77

75 <65 65-73 >73 <70 70-78 >78

76 <65 65-74 >74 <70 70-79 >79

77 <65 65-75 >75 <70 70-80 >80

>77 <65 65-75 >75 <70 70-80 >80

* Ldn is used for land use where nighttime sensitivity is a factor; Leq during the hour of maximum transit noise exposure is used for land use 

involving only daytime activities.
Chapter 3: Noise Impact Criteria 3-5

Table 3-2 Land Use Categories and Metrics for High Speed Train Noise Impact Criteria

Land Use

Category

Noise Metric*

(dBA) Description of Land Use Category

1 Outdoor Leq(h)**

Tracts of land where quiet is an essential element in their intended purpose. 

This category includes lands set aside for serenity and quiet, and such land 

uses as outdoor amphitheaters and concert pavilions, as well as National 

Historic Landmarks with significant outdoor use.

2 Outdoor Ldn

Residences and buildings where people normally sleep. This category 

includes homes, hospitals, and hotels where a nighttime sensitivity to noise 

is assumed to be of utmost importance.

3 Outdoor Leq(h)**

Institutional land uses with primarily daytime and evening use. This 

category includes schools, libraries, and churches, where it is important to 

avoid interference with such activities as speech, meditation, and 

concentration on reading material. Buildings with interior spaces where 

quiet is important, such as medical offices, conference rooms, recording 

studios and concert halls fall into this category, as well as places for 

meditation or study associated with cemeteries, monuments, and museums. 

Certain historical sites, parks and recreational facilities are also included.

*

 Onset-rate adjusted sound levels (Leq, Ldn) are to be used where applicable.

** Leq for the noisiest hour of transit-related activity during hours of noise sensitivity.

Table 3-3 Interim Criteria for High Speed Train Noise Effects on Animals

Animal Category Class Noise Metric Noise Level (dBA)

Mammals (Livestock) SEL 100

Domestic

Birds (Poultry) SEL 100

Mammals SEL 100

Wild

Birds SEL 100

3.1.2 Definitions of Levels of Impact

The noise impact criteria are defined by two curves relating project noise levels to existing noise. Below 

the lower curve in Figure 3-1, a proposed project is considered to have no noise impact since, on the 

average, the introduction of the project will result in an insignificant increase in the number of people 

highly annoyed by the new noise. The curve defining the onset of moderate noise impact stops increasing 

at 65 dB for Category 1 and 2 land use, a standard limit for an acceptable living environment as defined 

by a number of federal agencies. Project noise above the upper curve is considered to cause Severe 

Impact since a significant percentage of people would be highly annoyed by the new noise. This curve 

flattens out at 75 dB for Category 1 and 2 land use, a level associated with an unacceptable living 

environment. As indicated by the right-hand scale on Figure 3-1, the project noise criteria are 5 decibels 

higher for Category 3 land uses since these types of land use are considered to be slightly less sensitive to 

noise than the types of land use in categories 1 and 2.
3-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment

The proposed project is judged to have a moderate impact between these two curves. The change in the 

cumulative noise level is noticeable to most people, but it may not be sufficient to cause strong, adverse 

reactions from the community. In this transitional area, other project-specific factors must be considered 

to determine the magnitude of the impact and the need for mitigation, such as the predicted level of 

increase over existing noise levels and the types and numbers of noise-sensitive land uses affected.

Although the curves in Figure 3-1 are defined in terms of the project noise exposure and the existing noise 

exposure, it is important to emphasize that the increase in the cumulative noise – when the project noise is 

added to existing noise – is the basis for the criteria. The complex shapes of the curves are based on the 

considerations of cumulative noise increase described in Appendix A. To illustrate this point, Figure 3-2 

shows the noise impact criteria for Category 1 and 2 land use in terms of the allowable increase in the 

cumulative noise exposure. The horizontal axis is the existing noise exposure and the vertical axis is the 

increase in cumulative noise level due to the high-speed train project. The measure of noise exposure is 

Ldn for residential areas and Leq for land uses that do not have nighttime noise sensitivity. Since Ldn and 

Leq are measures of total acoustic energy, any new noise source in a community will cause an increase, 

even if the new source level is less than the existing level. Figure 3-2 shows that the criterion for impact 

allows a noise exposure increase of 10 dBA if the existing noise exposure is 42 dBA or less but only a 1 

dBA increase when the existing noise exposure is 70 dBA.

As the existing level of ambient noise increases, the allowable level of project noise increases, but the 

total allowable increase in community noise exposure is reduced. This reduction accounts for an 

unexpected result -- project noise exposure levels that are le ss than the existing noise exposure can still 

cause impact. The examples in Table 3-4 more clearly illustrate the levels of project noise and existing 

levels of exposure that result in crossing the threshold of impact.

Table 3-4 Noise Impact Criteria: Effect on Cumulative Noise Exposure

Ldn or Leq in dBA (rounded to nearest whole decibel)

Existing Noise 

Exposure Project Noise Exposure Combined Total Noise Exposure

Noise Exposure 

Increase

45 51 52 7

50 53 55 5

55 55 58 3

60 57 62 2

65 60 66 1

70 64 71 1

75 65 75 0
Chapter 3: Noise Impact Criteria 3-7

Figure 3-2 Increase in Cumulative Noise Levels Allowed by Criteria (Land Use Cat. 1 & 2)

Any increase in allowable noise exposure greater than shown in Table 3-4 will cause impact. This table 

shows that as the existing noise exposure increases from 45 dBA to 75 dBA, the allowed project noise 

exposure increases from 51 dBA to 65 dBA. However, the allowed increase in the cumulative noise level 

decreases from 7 dBA to 0 dBA (rounded to the nearest whole decibel). The justification for this 

decrease is that people already exposed to high levels of noise will notice and be annoyed even by only a 

small increase in the amount of noise in their community. In contrast, if the existing noise levels are quite

low, a greater change in the community noise will be required for the equivalent level of annoyance. It 

should be noted that these annoyance levels are based on general community reactions to noise at varying 

levels that have been documented in scientific literature and do not account for specific community 

attitudinal factors that may exist.

3.2 APPLICATION OF NOISE IMPACT CRITERIA

This section provides practical guidance on interpretation of the land use categories and application of the 

impact criteria.

3.2.1 Noise-Sensitive Land Uses

As indicated in Section 3.1.1, the noise impact criteria and descriptors for human annoyance depend on 

land use, designated either Category 1, Category 2, or Category 3. Category 1 includes tracts of land 

where quiet is an essential element in their intended purpose, such as outdoor concert pavilions or 

National Historic Landmarks where outdoor interpretation routinely takes place. Category 2 includes 

residences and buildings where people sleep, while Category 3 includes institutional land uses with 

daytime and evening use, such as schools, places of worship, and libraries.

The criteria do not apply to most commercial or industrial uses because, in general, the activities within 

these buildings are compatible with higher noise levels. They do apply, however, to business uses that 

depend on quiet as an important part of operations, such as sound and motion picture recording studios.
3-8 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Historically significant sites are treated as noise-sensitive depending on the land use activities. Sites of 

national significance with considerable outdoor use required for site interpretation would be in Category 

1. Historical sites that are currently used as residences would be in Category 2. Historic buildings with 

indoor use of an interpretive nature involving meditation and study fall into Category 3. Category 3 sites 

include museums, significant birthplaces, and buildings in which significant historical events occurred.

Most busy downtown areas have buildings that are historically significant because they represent a 

particular architectural style or are prime examples of the work of an historically significant designer. If 

the buildings or structures are used for commercial or industrial purposes and are located in busy 

commercial areas, they are not considered noise-sensitive, and the noise impact criteria do not apply. 

Similarly, historical transportation structures, such as terminals and railroad stations, are not considered 

noise-sensitive sites. These buildings or structures are, of course, afforded special protection under 

Section 4(f) of the DOT Act and Section 106 of the National Historic Preservation Act. However, based 

strictly on how they are used and the settings in which they are located, these types of historical buildings 

are not considered noise-sensitive sites.

While parks are considered in general to be noise-sensitive sites, in some cases actual noise sensitivity 

depends on how the park is being used. Parks used for passive purposes such as reading, meditation, and 

conversation would be considered more noise-sensitive than ones used for sports or other active 

recreational pursuits.

3.2.2 Considerations in Applying the Noise Impact Criteria

The procedure for assessing Impact is to determine the existing noise exposure and the predicted project 

noise exposure at a given site, in terms of either Ldn or Leq(h) as appropriate, and to plot these levels on 

Figure 3-1. In locations very near the right-of-way, the “onset-rate adjusted sound level” may be used 

(Figure 4-2). The location of the plotted point in the three impact ranges is an indication of the 

magnitude of the impact. For simplicity, noise impact also can be determined by using Table 3-1, 

rounding all noise level values to the nearest whole decibel before using the table. This level of precision 

is sufficient for determining the degree of noise impact at specific locations and should be adequate for 

most applications. However, a more precise determination of noise impact may be appropriate in some 

situations, such as estimating the distance from the project to which noise impact extends. In such cases, 

more precise noise limits can be determined using the criteria equations provided in Appendix A.

The noise criteria are to be applied outside the building locations for residential land use and at either the 

property line or the nearest point of use for parks and other significant outdoor use. However, for 

locations where land use activity is solely indoors, noise impact may be less significant if the outdoor-toindoor reduction is greater than for typical buildings (about 25 dB with windows closed). Thus, if the 

project sponsor can demonstrate that this is the case, mitigation may not be needed.

It is important to note that the criteria specify a comparison of future project noise with existing noise and 

not with projections of future "no-build" noise exposure (i.e., without the project). This is because 

comparison of a projection with an existing condition is more accurate than comparison of a projection 

with another projection. Furthermore, it should be emphasized that it is not necessary nor is it 

recommended that the existing noise exposure be determined by taking measurements at every noisesensitive location in the project area. Rather, the recommended approach is to characterize the noise 
Chapter 3: Noise Impact Criteria 3-9

environment for "clusters" of sites based on measurements or estimates at representative locations in the 

community. In view of the sensitivity of the noise criteria to the existing noise exposure, careful 

characterization of the existing noise is important. Guidelines for selecting representative receiver 

locations and determining ambient noise are provided in Appendix B.

Application of criteria for livestock and wildlife provides information on the exposed area in which noise 

could have an effect, even if the consequences of those effects are not fully known. Researchers have 

observed both behavioral and physiological effects with the approximate single event sound levels listed 

in Table 3-3. The noise descriptors used by the researchers are not always well defined, but the best 

descriptor for a single event that incorporates both level and duration is the Sound Exposure Level (SEL). 

Procedures for calculating SEL for varying distances from high speed train passbys are described in 

Chapters 4 and 5. Criteria are not yet fully developed to the point where dose-response relationships can 

be fully described for different animal species. However, the assessment is based on the assumption that 

impact occurs when a noise event is sufficiently loud to generate an observable effect in domestic 

livestock or wildlife. The term “wildlife” is assumed to include all endangered species until speciesspecific information can be developed.

3.2.3 Mitigation Policy Considerations

FRA’s traditional approach to abatement of noise sources from high speed train systems is embodied in 

its Railroad Noise Emission Compliance Regulation. 22 Rather than specific environmental regulations, 

the compliance regulation is intended to enforce the “Noise Emission Standards for Transportation 

Equipment: Interstate Rail Carriers” promulgated by the U.S. Environmental Protection Agency.23 These 

Standards limit the amount of noise emitted from power cars and rail cars under stationary and moving 

conditions. In addition, the National Environmental Policy Act (NEPA) establishes a broad mandate for 

federal agencies to incorporate environmental protection and enhancement measures into the programs 

and projects they help promote, approve and/or finance.24 FRA strongly encourages noise abatement on 

high speed train projects, especially where severe noise impacts are identified according to methods of 

this manual.

 

22U.S. Department of Transportation, Federal Railroad Administration,”Railroad Noise Emission 

Compliance Regulations,” Final Rule, 48 Federal Register 56756- 56761; December 23, 1983 (49 Code of Federal 

Regulations 210).

23U.S. Environmental Protection Agency, “Noise Emission Standards for Transportation Equipment: 

Interstate Rail Carriers,” 40 Code of Federal Regulations 201, July 1, 1984.

24United States Congress, National Environmental Policy Act of 1969; P.L. 91-190, January 1, 1970.
3-10 High-Speed Ground Transportation Noise and Vibration Impact Assessment
 Chapter 4: Initial Noise Evaluation 4-1

CHAPTER 4 - INITIAL NOISE EVALUATION

This chapter contains procedures for an initial evaluation of potential noise impacts from a high-speed 

train project. The goals of an initial noise evaluation are to identify the potential for impacts and to 

determine their order of magnitude, so that a more detailed analysis can be done in areas where significant 

impacts are found during later phases of the design processes. The initial evaluation includes two parts: a 

preliminary screening of the project corridor to identify areas of potential impact, especially when the 

technology or alignments have not been selected, and a general noise assessment for when more details 

are known or when representative cases are required. The Screening Procedure is described in Section 

4.1 and the General Assessment procedures are described in Section 4.2. An example of an initial noise 

evaluation appears at the end of this chapter. The initial evaluation results in an inventory of buildings 

where noise impact could occur and where noise mitigation measures, such as noise barriers, may be 

needed. In this regard, the method is designed to overstate the potential impact. This information is 

useful for comparing alternatives and selecting those with the least potential for noise impacts.

Noise from high-speed trains passing near noise-sensitive receptors is the focus of an initial evaluation. 

Except for special cases, other ancillary project noise sources, such as electrical sub-stations, roadway 

traffic near passenger stations, and maintenance facilities generally should not be considered at this stage 

of planning. Usually, a lack of detail on the design and placement of these types of noise sources 

precludes a meaningful noise assessment.

The screening procedure of the initial evaluation is based on the type of technology and the type of area 

the alignment is passing through. The screening procedure identifies areas where impacts are likely to 

occur, but it does not attempt to predict noise exposure at specific receptors or to estimate the mitigation 

requirements. The screening procedure is appropriate for very early phases of a project when the 

alternatives are still at a conceptual stage.

The General Assessment portion of the initial evaluation is based on noise source and land use 

information likely to be available at early stages in the project development process. The General 

Assessment includes estimating source levels for the high-speed train technology being considered, 

estimating existing noise exposure using a simplified procedure, determining noise impact based on the 

criteria given in Chapter 3, and preparing an inventory of the potential impacts and mitigation 

requirements. The General Assessment can help establish the most promising corridor locations for 

further project evaluation.

For programmatic environmental reviews of long transportation corridors that cover extensive 

geographical areas, a programmatic noise assessment can be accomplished by adapting the screening 

procedure to incorporate some aspects of the general assessment procedure. By applying the general 

noise assessment procedure to a few representative cases in the project area, screening distances can be 

adjusted to a specific high-speed train technology and to regional geographic conditions. By completing a 

general noise assessment of a full range of representative cases, typical high-speed train noise impacts can 
4-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

be defined that reflect regional land development patterns and existing noise sources.

4.1 NOISE SCREENING PROCEDURE

The Noise Screening Procedure is based on very general assumptions and can be applied in the early 

phases of a project before specific project elements have been defined. Screening distances appropriate 

for the project are used to define the study area for any subsequent noise impact assessment. Distances 

for project types are listed in Table 4-1. When there are noise-sensitive receptors within the screening 

distance, impact is possible, and as the project definition evolves, the procedures for General (this 

chapter) and Detailed (Chapter 5) Noise Assessments are used to determine the extent and severity of 

impact. 

Screening indicates whether any noise-sensitive receivers are close enough to the proposed alignments for 

noise impact to be possible, and identifies locations where the project has little possibility of noise 

impact. Screening can be useful when making a broad-brush comparison of potential impacts for 

different corridors. Screening also can be used to select segments that will be studied in more detail and to 

define the study area of any subsequent noise impact assessment. This selection can be important in 

delineating the extent of a noise impact study since high-speed train corridors may extend over hundreds 

of miles. Where no noise-sensitive land uses are within the screening distance, no further noise 

assessment is necessary. This approach allows the noise analysis to focus on locations where impacts are 

likely. 

The Screening Procedure takes account of the noise impact criteria, the type of project, and noisesensitive land uses. For screening purposes, all noise-sensitive land uses are considered to be in a single 

category. The distances given in Table 4-1 delineate a project's noise study area. The areas defined by 

the screening distances are sufficiently large to encompass all potential impacts in most cases. The 

distances were developed using typical noise emissions of high-speed trains, but with the typical number 

of operations and speeds of a given project type and the threshold of moderate impact from Chapter 3 to 

obtain worst case conditions. The assumed conditions for the screening distances are summarized in 

Table 4-2 and described in more detail in Appendix G. This approach gives a conservative estimate of 

impact. With the greater refinement in the general and detailed procedures, the noise impact distances 

should always be less than the screening distances listed in Table 4-1. 

In some cases it may be desirable to scale up or down the screening distances corresponding to known 

conditions in a corridor. This can be done by adjusting the project assumptions in Table 4-2 and applying 

the equations in Section 4.2. Corridor existing conditions can be adjusted using the approach described in 

Appendix G. The adjusted levels are assessed according to the threshold of moderate impact. 

The Screening Procedure is applicable to high-speed train projects using either steel-wheeled or maglev 

technologies. Screening distances by the type of corridor or alignment involved, either shared with an 

existing rail or highway corridor or newly built through undeveloped land, are listed in Table 4-1.

The steps for the Screening Procedure are:

Step 1. Project Setting. Determine the type of transportation corridor and existing noise 

environment. Locate them on Table 4-1. Review the assumptions given in Table 4-2. If 

known operations vary by a factor of 2 or more from assumptions for railroad or highway 

corridors, adjust existing noise environments using FTA or FHWA methods described in 
 Chapter 4: Initial Noise Evaluation 4-3

Appendix G. For many high-speed rail projects, the corridor can vary from one type to 

another, both in alignment characteristics and ambient environment, over the length of the 

project corridor. These variations should be identified and considered when screening an 

entire project corridor.

Step 2. Technology. Determine the appropriate column (steel-wheel on steel rail or maglev and 

speed regime) under Screening Distance in Table 4-1. If speed regimes are not known, use 

regime III (highest speed). If operations are expected to differ significantly (factor of 2) 

from assumptions in Table 4-2, calculate project noise according to Section 4-2 and 

determine distance to the threshold of moderate impact. Apply this distance from the 

guideway centerline. 

Step 3. Study Area Characteristics. Within the distance noted above, locate any of the noisesensitive land uses listed in Table 3-2.

Step 4. Assessment. If it is determined that none of the listed land uses are within the distances 

noted in Table 4-1, then no further noise analysis is needed. On the other hand, if one or 

more of the noise-sensitive land uses are within the screening distances noted in Table 4-1, 

then the project will require further analysis using the General Noise Assessment procedures 

described in the following section.

Table 4-1 Screening Distances for Noise Assessments

Screening Distance in Feet for Project Type and 

Speed Regime*

Steel-Wheeled Maglev Corridor

Type

Existing Noise

Environment

Reg. II Reg. III Reg. II Reg. III

Urban/Noisy Suburban - unobstructed 300 ft. 700 ft. 50 ft. 400 ft.

Railroad Urban/Noisy Suburban - intervening buildings** 200 300 50 250

Quiet Suburban/Rural 500 1200 50 700

Urban/Noisy Suburban - unobstructed 250 600 50 400

Highway Urban/Noisy Suburban - intervening buildings** 200 350 50 250

Quiet Suburban/Rural 400 1100 50 600

Urban/Noisy Suburban - unobstructed 350 700 75 450

New Urban/Noisy Suburban - intervening buildings** 250 350 75 300

Quiet Suburban/Rural 600 1300 150 800

*Measured from centerline of guideway or rail corridor. Minimum distance is assumed to be 50 ft.

**Rows of buildings assumed to be at 200 ft., 400 ft., 600 ft., 800 ft. and 1000 ft. parallel to guideway.
4-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Table 4-2. Assumptions for Screening Distances*

Corridor Type Assumed Operations

Freight Railroad 10 daytime, 2 nighttime

1 locomotive, 40 cars

55 mph

Highway 4-lanes, 1,450 peak hour volume

95% automobiles, 2% medium trucks, 3% heavy trucks

55 mph

New No major rail or road corridors

Urban/Noisy suburban Ldn = 60 dB

Quiet suburban/Rural Ldn = 50 dB

Project Type Operations Speeds

Steel wheel 2 power cars, 10 coaches

45 daytime, 12 nighttime

Regime II @ 100 mph

Regime III @ 180 mph

Maglev 10 cars,

45 daytime, 12 nighttime

Regime II @ 100 mph

Regime III @ 200 mph

*See Appendix G for details.

4.2 GENERAL NOISE ASSESSMENT

The General Noise Assessment determines the potential for noise impact by applying simplified models 

to estimate train noise and existing ambient noise, and then comparing the results with the impact criteria 

in Chapter 3. The procedure involves noise predictions commensurate with the level of detail of available 

data in the early stages of project planning and environmental clearance. For projects in preliminary 

stages of planning, a general assessment may be all that is needed to evaluate noise impacts and to 

propose mitigation measures. The General Assessment also can be used to compare alternatives, such as 

locations of alignments or candidate high-speed transportation modes (steel-wheeled versus maglev 

technology), and can provide the appropriate level of detail about noise impacts for a corridor or sub-area 

study. A combination of the Screening Procedure and General Assessment may be applied to long 

transportation corridors in programmatic environmental assessments.

The general noise assessment procedure starts with determining the project noise level at a reference 

distance for the various project alternatives. This reference noise source level differs depending on the 

type of high-speed vehicle chosen for the project. The noise generated by each vehicle depends on the 

source characteristics described in Chapter 2. The reference noise source level is then used to compute 

noise exposure, accounting for anticipated operating conditions based on information about the project. 

At an early project stage, the information available may include:

• candidate technology or vehicle type

• guideway variations

• hours of operation

• headways

• design speed

• alternative alignments.

This information is not sufficient to predict noise levels at all locations along the right-of-way, but by 

using conservative estimates (for example, maximum design speeds and operations at design capacities) it 

is sufficient to estimate worst-case noise impacts.

The steps in the general noise assessment are described in detail in the following sections and are 
 Chapter 4: Initial Noise Evaluation 4-5

summarized below:

Step 1. Source Levels 

• Place the alternative under study into one of three categories: steel-wheeled electric -powered, steelwheeled fossil fuel-powered, or maglev. 

• Determine the source reference level, which pertains to a typical passby of the project vehicle in a 

given speed range under reference operating conditions. Use Table 4-3. The noise descriptor, SEL, 

used to define the reference level is discussed in Chapter 2. If Lmax is available from source 

measurements or specifications, a conversion to SEL is necessary. Use the method described in 

Appendix C.

Step 2. Project Operating Conditions

• Convert the source reference level to noise exposure in terms of Leq(h) or Ldn at the reference 

distance of 50 feet under anticipated project operating conditions. Use the appropriate equations

contained in Table 4-5, depending upon the type of source.

• Correct the noise exposure to account for vertical terrain effects, such as embankments and trenches. 

Use the method described in Section 4.2.2.

Step 3. Propagation Characteristics

• Draw a noise exposure-versus-distance curve for this source, which will show the project noise 

exposure as a function of distance, ignoring shielding. Use the method described in Section 4.2.3.

• Estimate the reduction in noise level to account for shielding attenuation from rows of buildings. Use 

the general rule given at the bottom of Table 4-6. It is important to include adjustments for shielding 

attenuation from rows of buildings; omitting them can result in unrealistically high estimates of noise 

impact.

• Draw an adjusted exposure-versus-distance curve.

• Identify noise-sensitive locations very close to the tracks where receivers may be startled by rapid 

onset rates of noise from high-speed trains. The distance defining a potential startle zone is identified 

in Section 4.2.3. 

Step 4. Study Area Characteristics

• Estimate the existing noise exposure for areas adjacent to the project. Use the methods described in 

Section 4.2.4.

Step 5. Noise Impact Estimation

• Locate the distance at which project noise exposure results in impact corresponding to the estimated 

existing noise exposure, on a point-by-point basis. Use the impact criteria from Chapter 3. 

• Connect the points to obtain a contour line around the proje ct, which signifies the outer limits of 

impact.

Alternatively, when it is desired to compare different technologies:

• Determine contours corresponding to specific noise levels from the exposure-vs.-distance curves (for 

example, 60 dBA, 65 dBA, 70 dBA contours).

Step 6. Noise Impact Inventory

• Tabulate noise-sensitive land uses within the specific contours.
4-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Step 7. Noise Mitigation

• Estimate the noise reduction that would be achieved with mitigation in the community areas where 

potential for impact has been identified.

• Repeat the tabulation of noise impacts after mitigation has been applied.

4.2.1 Noise Source Levels for General Assessment

The procedure starts with establishing the noise source levels, expressed in terms of SEL under reference 

conditions of speed, distance, and length. These quantities are given in Table 4-2 for the two general 

categories of high-speed trains: steel-wheeled (including both electric -and fossil fuel-powered 

locomotives) and maglev trains. 

Reference SELs for each type of high-speed vehicle are given in Table 4-3 for the three speed regimes 

corresponding to propulsion, mechanical, and aerodynamic noise sources dominating the overall wayside 

noise. The speed regimes are discussed in Chapter 2. These speed regimes are defined by transition 

speeds, St1 and St2, as well as speed-dependency coefficients K, which represent the slopes of the SEL 

versus speed curve in each regime. These parameters are included in Table 4-3. For each speed regime, 

the table also lists the reference SEL, reference speed, and reference length. These parameters are used 

in the equations of Table 4-5 to predict the noise exposure at 50 feet. A reference distance of 50 feet is 

used to minimize propagation effects. 

Table 4-3 Reference Parameters at 50 feet from Track/Guideway

Vehicle Type

Reference Quantity Abbreviation Steel-Wheeled Speed

Regime

Electric Fossil Fuel

Maglev

I 89 dBA 87 dBA 72 dBA

Reference SEL SELref II 93 dBA 94 dBA 73 dBA

III 99 dBA n/a 78 dBA

I 3 5 2

Speed Coefficient K II 17 16 17

III 47 n/a 50

I 20 mph 20 mph 20 mph

Reference Speed Sref II 90 mph 90 mph 60 mph

III 180 mph n/a 120 mph

I 70 feet 70 feet 82 feet

Reference Length lenref II 664 feet 664 feet 82 feet

III 70 feet n/a 82 feet

St1

I II 60 mph 60 mph 60 mph

Transition Speed

St2

II III 170 mph n/a 120 mph
 Chapter 4: Initial Noise Evaluation 4-7

A generalized plot of SEL as a function of speed, with each of the three speed regimes identified is shown 

in Figure 4-1. This plot illustrates use of several of the parameters listed in Table 4-3 in each of the three 

speed regimes. It differs from Figure 2-7 in that it plots SEL, not Lmax, versus speed and represents the 

relationship as three discrete straight-line segments to approximate the smooth curve. The general 

equation relating SEL to speed for each speed regime at the reference distance (50 feet) is defined as:

where S = train speed in miles per hour, and all other quantities are de fined by the reference parameters 

given in Table 4-3. As indicated in Figure 4-1, the speed coefficient K represents the “slope” of the line 

in each speed regime.

Figure 4-1 Generalized SEL vs Speed for a High-Speed Train Passby

4.2.2 Project Operating Conditions

After determining the reference level for the candidate high-speed train technology, the next step is to 

determine noise exposure at 50 feet expressed in terms of Ldn and Leq(h). The additional data needed 

include:

• number of train passbys during daytime hours (defined as 7 a.m. to 10 p.m.) and nighttime hours 

(defined as 10 p.m. to 7 a.m.),

















= +

ref

ref S

S

SEL SEL K log
4-8 High-Speed Ground Transportation Noise and Vibration Impact Assessment

• maximum number of train passbys during hours that Category 1 or Category 3 land uses are normally 

in use (usually the peak-hour train volume),

• number and unit length of locomotives (power cars) and passenger coaches per train,

• speed (maximum expected), and

• guideway configuration.

Shielding. Attenuation from various types of shielding including noise barriers, also should be accounted 

for at this step of the process. Shielding attenuation depends primarily on geometrical factors relating the 

noise source, receiver, and intervening terrain or structures. The approximate noise reduction provided 

from the shielding effects of track layout such as trenches and embankments, as well as from "negative" 

shielding (i.e., noise increase) for elevated structures are provided in Table 4-4 . These noise reductions 

are given in terms of a correction factor, Cs, to be added to the reference SEL.

If noise mitigation is determined necessary at the end of the first pass of the General Assessment, Table 4-

4 also gives the nominal noise reduction achieved by a 10-foot high wayside noise barrier, the most 

common mitigation measure for railway noise.

The equations necessary for calculating these quantities based on the reference SEL, adjusted to account 

for operating conditions, and the parameters listed here are listed in Table 4-5.

4.2.3 Propagation Characteristics

The process described in the Section 4.2.2 results in estimates of noise exposure at 50 feet for the 

proposed project. This section describes the procedure used to estimate the project noise exposure at 

other distances, resulting in a noise exposure versus distance relationship sufficient for use in a general 

assessment. The procedure is as follows:

1. Noise Exposure at 50 feet. Determine the Ldn or Leq at 50 feet for the appropriate vehicle type 

using the equations in Table 4-5.

2. Attenuation with Distance. Adjust for the distance to the receiver using the equation:













= −

50

( ) ( ) 15 log tan , 50

d

L orL L orL dn eq atdis ce d dn eq at feet

where d is the perpendicular distance from the receiver to the track centerline in feet. This equation gives 

an approximate relationship between noise exposure and distance that can be used to determine the noise 

impact for the first row of unobstructed buildings. This relationship can be plotted to display noise from 

both unmitigated and mitigated conditions to assess the benefits from mitigation measures.
 Chapter 4: Initial Noise Evaluation 4-9

Table 4-4 Shielding Corrections for Track Geometry

CASE Speed 

Regime

Shielding 

Correction

(Cs)

I

0 dBA

II

–10 dBA

1) Tracks in Shallow Cut

III

–3 dBA

I

–10 dBA

II

–15 dBA

2) Tracks in Deep Trench or Cut

III

–10 dBA

I

+4 dBA

II

+4 dBA

3) Tracks on Aerial Structure

III

+2 dBA

I

0 dBA

II

–5 dBA

4) Tracks on Embankment

III

0 dBA

I

0 dBA

II

–10 dBA

5) Noise Barrier

III

–5 dBA
4-10 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Table 4-5 Computation of Noise Exposure at 50 feet for General Assessment

Quantity Equation

SEL at 50 ft: 















+

















= +

ref ref

ref len

len

S

S

SEL SEL K log 10 log

Hourly Leq at 50 ft: Leq (h) = SEL+10logV +Cs −35 .6

Daytime Leq at 50 ft: ( )

( )

V Vd

h

eq eq L day L =

=

Nighttime Leq at 50 ft: ( ) ( ) eq eq V Vn

L night L h ==

Ldn at 50 ft:

( ) ( )

10 log 15 10 9 10 13.8

10

10

10

−

















= ∗ + ∗











 +











 L day L night

dn

eq eq

L

9

number of trains from 10 pm to 7 am

average hourly nighttime volume of train traffic, in trains per hour

15

number of trains from 7 am to10 pm

average hourly daytime volume of train traffic, in trains per hour

average hourly vol ume of train traffic, in trains per hour

train speed, in miles per hour

length of leading power unit, ft in Speed Regime III

total train length, ft in Speed Regime II

total length of power unit(s), ft in Speed Regime I

=

=

=

=

=

=











→

→

→

=

n

V

d

V

V

S

len
 Chapter 4: Initial Noise Evaluation 4-11

3. Shielding from Rows of Buildings. Account for shielding attenuation from rows of intervening 

buildings for second row receivers and beyond. Without accounting for shielding, impacts may be 

substantially over-estimated. Use the following general rules to determine the effect of shielding 

from intervening rows of buildings:

• Assign 3 dB of shielding attenuation for the first row of intervening buildings only. 

(Attenuation means a subtraction from the sound level.)

• Assign 1.5 dB of shielding attenuation for each subsequent row, up to a maximum total 

attenuation of 10 dB.

Rapid Onset Rates

As discussed in Chapter 2, there is considerable evidence that increased annoyance is likely to occur for 

train noise events with rapid onset rates. The relationship of speed and distance to define locations where 

the onset rate for high speed train operations may cause surprise is shown in Figure 4-2, assuming open 

flat terrain with unobstructed view of the tracks in both directions. The potential for increased annoyance 

for the most part is confined to an area very close to the tracks. For example, Figure 4-2 shows that 150 

mph high-speed train operations would have the potential for surprise within 32 feet of the track 

centerline. 

For the purposes of a General Noise Assessment, it is necessary only to identify noise-sensitive locations 

where surprise may be an additional annoyance. The speed information contained in Figure 4-2 should be 

used to determine the distance within which surprise could occur. Any noise-sensitive land use within 

that distance should be identified as a candidate for increased annoyance. 

Figure 4-2 Distance from Tracks within which Surprise Can Occur for HST

4.2.4 Study Area Characteristics

The impact criteria described in Chapter 3 base the threshold of impact on estimates of existing noise 

exposure in the vicinity of the project. Impact is assessed using a combination of the existing noise 

exposure and the additional noise exposure that will be caused by the project. The Detailed Analysis 

procedures presented in Chapter 5 base the existing noise exposure on noise measurements at 
4-12 High-Speed Ground Transportation Noise and Vibration Impact Assessment

representative locations in the community. It is generally a good idea to base all estimates of existing 

noise on measurements, especially at locations known to be noise-sensitive. However, measurements are 

not always possible at the general assessment stage. This section gives procedures for estimating existing 

noise in the project study area from general data available early in project planning. The procedure uses 

Table 4-5, where a neighborhood's existing noise exposure is based on proximity to transportation sources 

such as nearby major roadways or railroads, or on population density in locations away from major 

sources of noise. The process is as follows:

1. Mapping: Obtain scaled mapping and aerial photographs showing the project location and 

alternatives. A scale of 1 inch = 200 or 400 feet is appropriate for the accuracy needed in the noise 

assessment. The size of the base map should be sufficient to show distances of at least 1,000 feet 

from the center of the alignment. Mapped areas are now available in GIS formats that provide 

great accuracy.

2. Sensitive Receivers: Review the maps, together with land use information, to determine the 

proximity of the noise-sensitive land uses to the project and to the nearest major roadways and 

railroad lines. When necessary, windshield surveys or more detailed land use maps may confirm 

the location of sensitive receivers. For land uses more than 1,000 feet from major roadways or 

railroad mainlines (see definitions in Table 4-5), obtain an estimate of the population density in the 

immediate area, expressed in people per square mile. When using population density, take care to 

exclude areas where there are no residences or sensitive land uses.

3. Existing Noise Exposure (highway, roadway, railroad and new corridors): Use Table 4-6 to 

estimate existing noise exposure. Existing noise exposure is estimated by first looking at a site's 

proximity to major roads and railroad lines. If the site is located far enough from any major "linear" 

sources so that ambient noise is dominated by local streets and community activities, then the 

estimate should be based on population density alone. If the site is within about 1,000 feet of a 

major linear source, an estimate of the noise exposure from that source should be made based on 

generalized assumptions. Compare the noise levels from each of the three categories (roadways, 

railroads, and population density) and select the highest level to estimate the current exposure. In 

all cases, the noise levels are underestimated to provide a conservative impact assessment.

Major roadways are separated into two categories: interstates, or roadways with four or more lanes 

that allow trucks; and “others,” parkways without trucks and city streets with the equivalent of 75 

or more heavy trucks per hour or 300 or more medium trucks per hour. The estimated roadway 

noise levels are based on data for light to moderate traffic on typical highways and parkways using 

the FHWA25 highway noise prediction model. Where a range of distances is given, the predictions 

are made at the outer limit, thereby underestimating the traffic noise at the inner distance. For 

highway noise, distances are measured from the centerline of the near lane for roadways with two 

lanes, while for roadways with more than two lanes the distance is measured from the geometric 

mean of the roadway, computed as follows:

( )( ) DGM = DNL DFL

where:

D

GM

 is the distance to the geometric mean, DNL and DFL are distances to the nearest lane 

and farthest lane centerlines, respectively.

 

25U.S. Department of Transportation, Federal Highway Administration, “FHWA Highway Traffic Noise Prediction Model,” 

FHWA-RD-77-108, December 1978.
 Chapter 4: Initial Noise Evaluation 4-13

For railroads, the estimated noise levels are based on an average train traffic volume of 5 to 10 

trains per day at 30 to 40 mph for mainline railroad corridors, and the noise levels are provided in 

terms of Ldn only. Distances are referenced to the track centerline or, in the case of multiple 

tracks, to the centerline of the rail corridor. Because of the intermittent nature of train operations, 

train noise will affect the Leq only during certain hours of the day, and these hours may vary from 

day to day. To reduce the chance of inaccurate estimates of noise impact when using the one-hour 

Leq descriptor, the Leq at sites near rail lines should be estimated based on nearby roadways or 

population density unless very specific train information is available.

In areas away from major roadways, noise from local noise sources is estimated using a 

relationship determined by the U.S. EPA.26 EPA determined that ambient noise can be 

approximately related to population density in locations away from transportation corridors, such 

as airports, major roads, and railroad tracks, according to the following relation:

Ldn = 22+ 10 log (p) (in dBA)

where p = population density in people per square mile. 

4. Existing noise exposure (rail transit corridor): If the proposed high-speed train project corridor is to 

be shared with an existing rail transit corridor (rapid transit, commuter rail, etc.), the methods 

described in Steps 1 through 3 are not adequate to characterize existing noise exposure accurately. 

Since existing noise exposure is a strong function of distance from the existing rail corridor, 

general estimates such as those presented in Table 4-6 are difficult to make, given the high 

variability in the operational characteristics of transit systems. In such cases, noise measurements 

at representative locations along the corridor are essential to estimate existing noise accurately. 

The procedure for the Detailed Noise Analysis (Chapter 5) recommends that these measurements 

be supplemented and/or substantiated through noise prediction methods developed specifically for 

different transit modes. These methods are provided in the guidance manual published by US 

Department of Transportation, Federal Transit Administration. 27

4.2.5 Noise Impact Estimation

It is often desirable to draw noise impact contours on land use maps to aid the impact inventory. Once the 

contours are on the map, the potential noise impacts can be estimated by counting the buildings inside the 

contours. The process is as follows:

1. Project versus Existing Noise Exposure. Identify the noise-sensitive neighborhoods and buildings 

and estimate existing noise exposure following the procedures described in Section 4.2.4. Use the 

estimate of existing noise exposure and the noise impact criteria in Figure 3-1 to determine two 

levels of project noise exposure that would cause Moderate Impact and Severe Impact. 

2. Noise Impact Contours. Determine the distances from the project to the two identified impact 

levels using the noise exposure-versus-distance relationships from Section 4.2.2. Plot points on the 

 

26U.S. Environmental Protection Agency, "Population Distribution of the United States as a Function of Outdoor Noise Level," 

Report 550/9-74-009, June 1974.

27US Department of Transportation, Federal Transit Administration, Transit Noise and Vibration Impact Assessment, Report No. 

DOT-T-95-16, April 1995.
4-14 High-Speed Ground Transportation Noise and Vibration Impact Assessment

land use map corresponding to those distances in the neighborhood under study. Continue this 

process for all areas surrounding the project. Connect the plotted points by lines to represent the 

noise impact contours.

3. Noise Exposure Contours. Alternatively, if it is desired to plot specific noise contours at, for 

example, 65 dBA, the distances also can be determined directly from the approach described in 

Section 4.2.2. Again, plot the points associated with a given noise level on the land use map and 

connect by lines to represent that contour.

It should be noted that the impact contours will move in and out with respect to the project boundary as 

the existing ambient exposure changes, as project source levels change, and as the amount of acoustical 

shielding changes. In general, the points should be placed close enough to allow a smooth curve to be 

drawn. For a General Assessment, the contours may be drawn through buildings and salient terrain 

features as if they were not present. This practice is acceptable considering the level of detail associated 

with a project in its early stages of development.

4.2.6 Noise Impact Inventory

The next step in the General Assessment is to develop an inventory of noise-sensitive land uses that are 

within the impact contours. Use land use information and the noise impact contours developed in Section 

4.2.5 to count buildings within the impact contours. In some cases it may be necessary to supplement the 

land use information or to determine the number of dwelling units within a multi-family building with a 

visual survey.
 Chapter 4: Initial Noise Evaluation 4-15

Table 4-6 Estimating Existing Noise Exposure for General Assessment

Distance from Major Noise Source1 (feet)

Population Density

(people per sq mile) Noise Exposure Estimates (dBA)

Interstate 

Highways2

Other 

Roadways3

Railroad Lines4

Leq

Day

Leq

Evening

Leq

Night Ldn

10 - 49

50 - 99

100 - 199

200 - 399

400 - 799

800 and up

75

70

65

60

55

50

70

65

60

55

50

45

65

60

55

50

45

40

75

70

65

60

55

50

10 - 49

50 - 99

100 - 199

200 - 399

400 and up

70

65

60

55

50

65

60

55

50

45

60

55

50

45

40

70

65

60

55

50

10 - 29

30 - 59

60 - 119

120 - 239

240 - 499

500 - 799

800 and up

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

75

70

65

60

55

50

45

1 - 99

100 - 299

300 - 999

1,000 - 2,999

3,000 - 9,999

10,000 - 29,999

30,000 and up

35

40

45

50

55

60

65

30

35

40

45

50

55

60

25

30

35

40

45

50

55

35

40

45

50

55

60

65

Notes:

1 Distances do not include shielding from intervening rows of buildings. General rule for estimating shielding attenuation in populated 

areas: Assume 1 row of buildings every 100 ft; -4.5 dB for the first row, -1.5 dB for every subsequent row up to a maximum of -10 dB 

attenuation.

2 Roadways with 4 or more lanes that permit trucks, with traffic at 60 mph.

3 Parkways with traffic at 55 mph, but without trucks, and city streets with the equivalent of 75 or more heavy trucks per hour and 300 

or more medium trucks per hour at 30 mph.

4 Main line railroad corridors typically carrying 5 to 10 trains per day at speeds of 30 to 40 mph.

The steps for developing the inventory are:

1. Construct tables for all the noise-sensitive land uses identified in the three land-use categories from 

Chapter 3.

2. For each alternative, tabulate buildings and sites that lie within the impact contours. For residential 

buildings, estimate either the number of buildings or number of dwelling units. Other pertinent 

information, such as existing noise levels, corridor segment delineations and expected train speed 

also may be useful in relating to the impacts. An example table is shown in Table 4-7.

3. Prepare summary tables showing the number of buildings and dwelling units within each impact 

zone for each alternative. Utilize the summary table to compare the alternatives, including those 

with and without noise mitigation measures.

4. Determine the possible need for mitigation based on the degree of impact and appropriate policy 

considerations.
4-16 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Table 4-7 Sample Noise Impact Inventory Table

Alignment: 1

Scenario: HS-Electric

Corridor Segment Distance to 

Contour (ft)

Impact Inventory without mitigation 

(Number of Buildings)

Milepost Moderate Impact Severe Impact

Description

From To

Existing 

Ldn (dBA)

Avg Train 

Speed 

(mph) Impact Severe 

Impact SF MF Inst SF MF Inst

Downtown Area 0.0 4.6 70 50 45 25 0 2 0 0 0 0

Inside I-95 4.6 5.7 65 80 70 40 6 1 0 0 0 0

To Route 100 5.7 9.5 65 100 80 45 12 0 0 2 0 0

To Pleasant St 9.5 12.0 65 60 60 30 1 0 0 0 0 0

Smithtown Station 12.0 12.2 60 25 40 20 0 0 0 0 0 0

Lakeville mountains 12.2 20.8 55 80 80 40 1 0 0 0 0 0

Central Valley 20.8 26.9 60 110 100 55 7 0 0 4 0 0

To Rt 66 crossing 26.9 33.4 60 125 110 65 6 0 1 2 0 0

I-84 corridor 33.4 41.6 65 140 125 75 14 0 1 5 0 1

To South St 41.6 44.2 65 80 70 40 2 0 0 1 0 0

Business District 44.2 46.2 65 55 60 30 0 1 0 0 0 0

Springfield Station 46.2 46.4 65 25 40 20 0 0 0 0 0 0

SF: Single-Family Residential Inst: Institutional (schools, 

MF: Multi-Family Residential churches, hospitals)

4.2.7 Noise Mitigation Requirements

The final step of the General Assessment is to estimate the noise mitigation measures required to 

minimize the number of impacts. The primary noise control treatment for steel-wheeled high-speed rail 

systems is the installation of wayside noise barriers.

28

 The approximate noise barrier lengths and 

locations developed in a general assessment will provide a preliminary basis for evaluating the costs and 

benefits of impact mitigation. This section provides guidelines for making order-of-magnitude cost 

estimates for noise barriers based on the length of barrier required. A more complete description of noise 

mitigation, with consideration given to other available mitigation treatments applied at the source, path, or 

receiver, and the benefits resulting from each is provided in Chapter 5.

Train noise barriers need to be high enough to effectively block the line of sight between the noise source 

and the receiver. The dominant source of train noise over most operating speeds for steel-wheeled highspeed rail, as with conventional rail systems, is wheel-rail interaction. To shield this noise effectively, 

relatively low barriers located close to the track are usually sufficient. A barrier with its top edge 6 to 8 

feet above the top of rail at the right-of-way line usually achieves effective shielding. A barrier at this 

height above the top of rail can reduce wheel-rail noise by 8 to 10 dBA.

 

28 Due to the unique characteristics of maglev systems, noise control considerations are likely to be made at the 

outset as an integral part of the system design. Retrofitting a maglev system for noise mitigation measures such as 

sound barriers is likely to incur great costs. Such design options as building sidewalls into the guideway structure, 

using a concrete rather than a steel guideway, and minimizing structural vibrations of the guideway and vehicle 

through design are noise control measures that can be taken as a baseline condition. As a result, it may not be 

applicable to estimate preliminary mitigation without more detailed information on system design. 
 Chapter 4: Initial Noise Evaluation 4-17

The attenuation of sound by a barrier is frequency dependent; all other things being equal, the higher the 

frequency of the noise, the greater the barrier attenuation. Because the sound energy for aerodynamic 

sound sources is in the low frequencies (below 500 Hz) these sources are inherently difficult to shield 

with a barrier. Further, because the sound level due to aerodynamic sources increases rapidly with 

increasing speed, a standard 8-foot barrier is less effective at high speeds, where aerodynamic sources 

dominate the overall sound level.

A relatively low barrier will not shield sound sources located high above the guideway, since such 

sources would protrude above the top of the barrier. This noise includes noise from propulsion sources, 

such as cooling fans, as well as aerodynamic noise generated at the upper part of the train. A description 

of these sources is presented in Chapter 2.

The following steps can be applied in making a preliminary estimate of the noise mitigation measures that 

might be required following an initial evaluation of noise impact:

1. Barrier Height. Assume an average noise barrier height of 8 feet as a cost-effective mitigation 

measure for high-speed rail noise impact. If shielding noise from higher noise sources (such as 

propulsion units) or protecting higher floors of residences is required, assume a 16-foot-high 

barrier.

2. Barrier Length. In addition to height, determine the length of noise barriers needed to extend far 

enough to each side of the affected receiver so that train noise from beyond the ends of the barrier 

does not significantly degrade its acoustical performance. As a rule, the barrier should be long 

enough to shield the entire train length for an angle of at least 60 degrees in either direction. 

3. Barrier Cost. Make a mitigation cost estimate based on the average height and length, assuming a 

unit cost of $20 per square foot. Use this cost to perform a cost-benefit analysis, if required.

4. Barrier Effectiveness. Assume a net barrier attenuation of 5 dBA for an 8 foot-high barrier, and 8 

dBA for a 16-foot-high barrier. These attenuations are applicable to both Leq and Ldn. Reassess 

impact with mitigation based on these reductions using the methods in this chapter.

It is important to note that the barrier estimates made in the initial evaluation are preliminary. Detailed 

barrier designs should be developed during the final engineering phase of the project. Some of the factors 

to be addressed during the final engineering phase are the structural, aesthetic, and acoustical feasibility 

of the barriers, as well as their cost effectiveness with respect to their acoustical benefits. The barriers 

should be constructed if they are found to be practical and prudent.

Examples 4-1 and 4-2 provide two examples of noise analyses utilizing the procedures presented in this 

chapter. Example 4-1 illustrates the Initial Noise Evaluation procedure for a representative high-speed 

rail project alternatives analysis, including both the Noise Screening and General Assessment. The source 

reference levels used in the analysis are taken directly from Table 4-2, since it is assumed that at this stage 

measurements or specifications of the equipment are unknown. Example 4-2 demonstrates the conversion 

of a measured or specified Lmax to the appropriate source reference level in SEL for use in the General 

Assessment procedure, using the methods presented in Appendix C.

Example 4-1. Initial Noise Evaluation Comparing Two High-Speed Rail Alignments

This example illustrates the initial noise evaluation procedure for a hypothetical high-speed rail project. 

The project involves an alternatives analysis of a proposed steel-wheeled high-speed rail system to serve a 

200-mile intercity corridor. Two alignment options are available, characterized by the following typical 
4-18 High-Speed Ground Transportation Noise and Vibration Impact Assessment

corridor segments:

Alignment Alternative 1: A direct route through primarily undeveloped, rural areas with farmland and 

scattered residences within 1,000 feet of the corridor. The track would be welded rail on ballast 

and concrete ties at-grade, designed for a maximum speed of 160 mph.

Alignment Alternative 2: Along the median of a busy multi-lane interstate highway (typical vehicle speeds 

of 60 to 70 mph during freely flowing conditions), passing through a densely developed area with

mixed residential and commercial land use. The alignment would be fully grade-separated, with 

welded rail on aerial structure (direct-fixation track on concrete slab), and with a maximum design 

speed of 160 mph. An example of a typical corridor segment is illustrated by the plan map in 

Figure 4-3. The closest unobstructed residences are 80 to 200 feet from the median centerline.

Assumptions

The assumptions for the project are the same for both alignment alternatives and are as follows:

• Proposed System: Steel-wheeled electrically powered high-speed train consisting of two power cars 

(one on each end) and 10 passenger coaches. Unit length of each power car is 73 feet, unit length of 

each passenger coach is 63 feet.

• Proposed Service: Total of 57 trains per day operating between 5:00 a.m. and 12:00 a.m. Headways 

are 20 minutes during daytime hours (7 a.m. to 10 p.m.) and 20 minutes during nighttime hours (10 

p.m. to 12 a.m., 5 a.m. to 7 a.m.) This service results in the following average hourly volumes:

VD = 3 trains/hour

VN = 1.33 trains/hour

Figure 4-3 Typical Corridor Segment for Example 4-1, Alignment Alternative 2
Chapter 4: Initial Noise Evaluation 4-19

Procedure

For steel-wheeled systems, the screening procedure (Table 4-1) calls for additional analysis for noisesensitive land use within 350 feet of a shared highway corridor, and 1300 feet of a new corridor through 

undeveloped land, thereby requiring further noise analysis for both alternatives. The procedure is 

summarized as follows:

Determination of Noise Exposure at 50 feet

1. Determine reference SEL at 50 feet and parameters for proposed system

Table 4-3 indicates that the maximum design speed of 160 mph puts the system in speed regime II. 

Thus, the following parameters are applied:

SELref = 93 dBA

K = 17

Sref= 90 mph

lenref = 664 feet

The actual source length is defined in Table 4-5 as the total train length, which is calculated as:

len = power cars + coaches = 776 feet

Using the first equation in Table 4-5, adjust to SEL at 50 feet for actual operating conditions,

SEL = SELref + K log (S/Sref) + 10 log (len/lenref)

= 93 + 17 log (160/90) + 10 log (776/664)

= 97.9 dBA, or 98 dBA (rounded).

2. Calculate Leq(h) and Ldn at 50 feet, adjusting for track geometry

For Alignment 1, the track is at-grade so there is no shielding adjustment for track geometry, i.e., 

Cs = 0. Thus, using the equations in Table 4-5, 

Leq(day) = SEL + 10 log (Vd) + Cs - 35.6

= 98 + 10 log (3) + 0 - 35.6 = 67.2 dBA

Leq(night) = SEL + 10 log (Vn) + Cs - 35.6

= 98 + 10 log (1.33) + 0 - 35.6 = 63.6 dBA

and, Ldn = 70.7 dBA, or 71 dBA (rounded)

For Alignment 2, speed regime II, Table 4-4 indicates that Cs = +4 dBA for aerial structure. Thus, 

Leq(day) = 98 + 10 log (3) + 4 - 35.6 = 71.2 dBA

Leq(night) = 98 + 10 log (1.33) + 4 - 35.6 = 67.6 dBA

and, Ldn = 74.7 dBA, or 75 dBA (rounded)

Estimate Propagation of Project Noise Exposure with Distance

3. Apply Noise Exposure-Versus-Distance Relationship

Using the method described in Section 4.2.3, the distance correction equation is applied to the 

project Ldn at 50 feet. A resulting curve of Ldn versus distance is obtained for each alignment 
4-20 High-Speed Ground Transportation Noise and Vibration Impact Assessment

option, as shown in Figure 4-4.

Estimate Existing Noise Exposure

4. Estimate existing noise at noise-sensitive sites

For Alignment 1, there are no major roadways or rail lines contributing to the existing ambient 

noise. Thus, the existing noise exposure should be estimated based on population density. For a 

predominantly rural area, a population density of 300-1000 people/square mile can be assumed, 

yielding an ambient Ldn of 45 dBA (from Table 4-5). From Figure 3-1, the corresponding project 

noise exposure Ldns causing impact for Category 2 land uses (residential) are 52 dBA and 59 dBA, 

for Moderate Impact and Severe Impact, respectively. 

For Alignment 2, the highway (the dominant noise source) is a major linear source from which 

noise attenuates rapidly with distance. Thus, it would be inaccurate in this case to assign a single 

"generalized" noise level to characterize a large area, as for Alignment 1. The existing noise 

exposure should be estimated as a function of distance from the highway on a site-specific basis.

From Figure 4-3, unobstructed residences range from 80 to 200 feet from the highway. Based on 

the information in Table 4-6 the Ldn is 70 dBA for residences closer than 100 feet from a major 

interstate highway, and 65 dBA for residences between 100 and 200 feet.

Figure 4-4 Noise Exposure vs Distance for Example 4-1

Applying the impact criteria curves in Figure 3-1, the project noise levels that cause impact for 

Alignment 2 are listed in the following table:

Project Ldn Criterion Distance to 

Highway

Existing Noise,

Ldn

Onset of 

Moderate Impact

Onset of 

Severe Impact

50 - 99 ft 70 dBA 64 dBA 69 dB

100 - 200 ft 65 dBA 61 dBA 66 dB
Chapter 4: Initial Noise Evaluation 4-21

Even though the criteria allow for a higher project Ldn for Alignment 2 than for Alignment 1 due 

to the higher existing noise environment, the net allowable increase is less for Alignment 2 (1 to 4 

dB) than for Alignment 1 (8 to 14 dB).

Noise Impact Contours

5. Determine Distances to Moderate Impact and Severe Impact

Distance-to-impact contours for each alignment are determined by extrapolating along the curves 

in Figure 4-4 and the project impact thresholds defined in Step 4. The results are summarized as 

follows for the residences:

Distance to Noise Impact 

Threshold, feet Alternative Distance

Existing 

Noise,

Ldn Moderate 

Impact

Severe 

Impact

Alignment 1 1000 ft 45 dBA 980 330

50 - 99 ft 70 dBA 250 110 Alignment 2

100 - 200 ft 65 dBA 450 200

6. Draw Noise Impact Contours

Draw contours for each affected residence based on the distances given in the table in Step 5. The 

impact distances are defined in terms of distance from the project corridor centerline. 

For Alignment 2, the Impact contours are shown in Figure 4-3. The Severe Impact contours do not 

go beyond the edge of the highway and are thus omitted for simplicity. The moderate impact noise 

contours are drawn at the two different distances, 250 feet and 450 feet, resulting from the change 

in existing noise based on distance to the highway. 38 residential buildings are located within the 

contours defining Moderate Impact (shaded in Figure 4-3). 

7. Estimate Startle Effects/Wildlife

For either alignment, the distance within which startle could occur is the same. Using a speed of 

160 mph in Figure 4-2 results in a distance of approximately 33 feet within which a person could 

be startled by a high-speed train. None of the buildings in Alignment 2 is within that distance. 

The distance within which wildlife could be disturbed also should be evaluated. According to 

Table 3-3, whenever the SEL exceeds 100 dBA there is a potential for effects on animals. Using 

Alignment 1 as a likely example, the SEL at 50 feet is 98 dBA. Using the propagation equation 

given in Section 4.2.3 with SEL in place of Leq (which is valid since both are sound energy 

descriptors), the distance “d” becomes 37 feet for SEL = 100 dBA. Consequently, wildlife could 

be disturbed within 37 feet of the tracks in Alignment 1.

End of Example 4-1

Example 4-2. Conversion of Specified Lmax to Source Reference Level in SEL

In the previous example, Alignment 2 is chosen as the preferred project alternative. The proposed system 

is modeled on a high-speed electric trainset with the following noise performance:
4-22 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Lmax = 86 dBA, measured at a distance of 82 ft from track centerline and a speed of 100 mph,

which puts us in Regime II for the General Assessment.

The steps to convert Lmax to the equivalent source reference levels for use in the General Assessment, 

instead of the tabulated value in Table 4-2, are as follows:

1. Convert to SEL under specified conditions

The parameters needed to evaluate the second equation in Table C-2 of Appendix C are:

len = 776 feet,

S = 100 mph,

d = 82 feet, and

1.36

2

arctan  =











∝=

d

len

sin (2a )= 0.41

Substituting into this equation we get SEL at the specified distance and speed:

 − ( × + )+ =











= + 10 2 1.36 0.41 3.3

100

776

SEL 86 10LOG LOG 93.2 dBA, or 93dBA (rounded)

2. Normalize to reference conditions of Table 4-3

Use the fourth equation in Table C-2 to normalize the SEL to the appropriate reference parameters 

in Table 4-2, for comparison with the tabulated level. The following values are required from 

Table 4-2:

K = 17,

Sref = 90 mph, and

ref len = 664 feet.

Evaluating the fourth equation in Table C-2 yields:

SELref = 94.8 dBA, or 95dBA (rounded)

Thus, this value of SELref, based on the specified Lmax, is 2 dBA higher than the tabulated value, 93 

dBA, in Table 4-3 for a steel-wheeled electric train in this speed regime.

End of Example 4-2













−

















+

















= +

len d

len

S

S

SEL SEL K

ref ref

ref

50 log 10 log 15 log
 Chapter 5: Detailed Noise Analysis 5-1

CHAPTER 5 - DETAILED NOISE ANALYSIS 

Procedures for performing a comprehensive assessment of noise impact for proposed high-speed train 

projects are presented in this chapter. The Detailed Noise Analysis allows site-specific noise predictions and 

mitigation evaluations for full consideration of noise impacts at specific receptors identified through the 

General Assessment. Considerably more precision can be achieved with the Detailed Noise Analysis than is 

possible with the General Assessment described in Chapter 4. While the General Assessment involves the use 

of generalized, overall noise source levels and simplified noise projection models, a Detailed Noise Analysis 

considers the noise from each subsource component, with each component defined in terms of a noisegenerating mechanism (e.g., propulsion, wheel-rail, aerodynamic), reference noise level, location along the 

train, and speed dependency. The Detailed Noise Analysis also uses more precise methods to estimate 

adjustments for horizontal and vertical geometry, ground absorption, and shielding. Furthermore, the method 

can be adapted to conventional freight and passenger train operations using information provided in 

Appendix E. Although the Detailed Noise Analysis procedures present all the information needed to predict 

noise and assess impact under "normal" circumstances, sometimes it will be appropriate to adapt the 

procedures using practical engineering judgment to reflect a project's specific design parameters. 

The Detailed Noise Analysis is appropriate for assessing previously identified noise impacts for high-speed

train projects after the preferred alignment and candidate high-speed train technologies have been selected. 

At this point some preliminary engineering has been completed as part of the preparation of an environmental 

document (usually an Environmental Impact Statement). Information required to perform a Detailed Noise 

Analysis includes the type of vehicle equipment to be used, train schedules, speed profiles, plan and profiles 

of guideways, locations of access roads, and landform topography, including adjacent terrain and building 

features. 

Equations, rather than graphs or tables of numbers, are used in these procedures as the primary mode of 

computation to allow the use of spreadsheets and/or programmable calculators. These equations and their 

supporting text have been streamlined in this chapter to provide a concise view of the Detailed Noise 

Analysis. Background information on noise concepts and the basics of high-speed train noise are presented in 

Chapter 2 and Appendix A. 

The steps in performing the Detailed Analysis parallel the steps for the General Noise Assessment, although 

more refined procedures are used to predict project noise and evaluate mitigation measures. The steps are 

outlined below. 
5-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

Existing Conditions 

Step 1. Noise Sensitive Receivers. Guided by the information in Section 5.1.1, identify noise-sensitive 

receivers. The number of receivers will depend upon the land use in the vicinity of the proposed 

project and the extent of the study area defined by the screening procedure described in Chapter 4. 

An initial evaluation (using the procedures presented in Chapter 4) will provide a good indication 

of the extent of potential impacts. 

Step 2. Existing Noise Exposure . Estimate the existing noise exposure at each noise sensitive receiver or 

cluster of receivers using the methods presented in Section 5.1.2. 

Projections of High-Speed Rail Noise 

Step 3. Source Reference Levels. Determine the technology applicable to the project: steel-wheeled highspeed (electric or fossil fuel), steel-wheeled very high-speed, or maglev. For each noise subsource, 

determine noise exposure in terms of SEL under reference operating conditions. These reference 

levels should incorporate source-noise mitigation that will be incorporated into the system 

specifications. 

Step 4. Project Operating Conditions. Adjust the subsource reference SELs to the anticipated 

operating conditions of the project (i.e., train consist and speed). 

Step 5. Propagation of Noise to Receivers. Develop an SEL-versus-distance relationship for each 

subsource that includes the effects of shielding along the path, as well as any propagation-path 

mitigation that will be included in the project. 

Step 6. Total Noise Exposure. Determine total SEL at each receiver by combining the levels from all 

subsources. Use the SEL to calculate total noise exposure [Ldn or L

eq

 (h)] using project operating 

parameters, including train schedule, speed, and length. 

Step 7. Maximum Noise Level for Train Passbys. (optional) If determining compliance with vehicle 

noise limits, project specifications or comparison with measured noise levels is desired, calculate 

the Lmax using equations provided in Appendix C.

Noise Impact Assessment 

Step 8. Noise Impact Assessment. Assess noise impact at each receiver or cluster of receivers using the 

criteria described in Chapter 3. If a geographic information system (GIS) database is available, 

incorporating the noise projections and the impact assessment into the GIS database can be an 

effective means of identifying and displaying where noise impact is expected to occur and 

comparing the relative impacts for different alternatives. While a conceptual approach for GIS 

implementation is provided, the details of this process are beyond the scope of this document. 

Mitigation of Noise Impact 

Step 9. Mitigation of Noise Impact. Where the assessment shows impact, evaluate alternative 

mitigation measures; then loop back to Step 3, modify the project noise computations, and 

reassess the remaining noise impact. The locations where noise mitigation is needed and any 
 Chapter 5: Detailed Noise Analysis 5-3

residual impacts with mitigation also can be effectively displayed with GIS databases. 

5.1 EXISTING CONDITIONS 

5.1.1 Step 1: Noise Sensitive Receivers 

The basic steps in identifying noise sensitive receptors are: 

ÿ Identify all noise-sensitive land uses. 

ÿ Find individual receivers, such as isolated residences and schools. 

ÿ Group residential neighborhoods into "clusters" that have similar levels of existing noise and 

would have similar levels of project noise. 

The steps in identifying noise sensitive receivers, both the number of receivers needed and their locations, are 

shown in Figure 5-1. 

Figure 5-1 Guide to Selecting Receivers of Interest

Identify Noise-Sensitive Land Uses 

A Detailed Noise Analysis usually should be performed for all noise-sensitive land uses where impact is 

identified in a General Noise Assessment. If a General Noise Assessment has not been done, all noisesensitive sites within the area defined by the noise screening procedure should be included. In areas where 

ambient noise is low, the assessment will include land uses that are farther from the proposed project than for 

areas with higher ambient levels. 

Three categories of land most likely to be affected by noise from high-speed train projects are listed in Table 

5-1. If noise impact was identified at other types of buildings/areas with noise-sensitive use by the general 

noise assessment, these types also should be identified. 
5-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

Table 5-1 Noise-Sensitive Land Uses

Land Uses Specific Use Selecting Receivers

Outdoor noise

senstitive areas

• Parks

• Historic sites used for interpretation

• Amphitheaters

• Recreation areas

• Playgrounds

• Cemeteries

• Select each noise-sensitive site

Residences • Single family residences

• Multi-family residences (apartment 

buildings, duplexes, etc.)

• Select each isolated residence

• For residential areas with uniform noise 

levels, cluster as described in text

Indoor noisesensitive sites

• Places of worship

• Schools

• Hospitals/nursing homes

• Libraries

• Public meeting halls

• Concert halls/auditoriums/theaters

• Recording/broadcast studios

• Museums and certain historic buildings

• Hotels and motels

• Select each noise-sensitive building

Sources of information that can be helpful in locating noise-sensitive land uses in the vicinity of the 

proposed project include: 

• Land use maps prepared by regional or local planning agencies or by the project staff. Particularly 

useful are project-specific maps (track plans, right-of-way plan and profile), which provide building-bybuilding detail for land uses bordering the project. 

• USGS maps prepared by the United States Geological Survey, generally at 2,000-foot scale. These maps 

show individual buildings except in highly urbanized areas, and generally show the location of all 

schools and places of worship, plus many other public -use buildings. The topographic contours on these 

maps can be useful for estimating acoustical shielding. 

• Road and town maps. These maps can supplement the USGS maps. They are generally more up-to-date 

and may be of larger scale. 

• Aerial photographs, especially those of 400-foot or smaller scale. When current, aerial photos are 

valuable in locating potential noise-sensitive land uses close to the proposed project and for determining 

the distances between receivers and the project alignment. 

• Windshield survey of the corridor. Definitive identification of noise-sensitive sites often requires driving 

the corridor and annotating land uses on base maps. Driving the corridor may be the only way to identify 

new construction, to confirm land uses very close to the project boundary, and to identify site 

characteristics such as topography and terrain features that are not readily apparent from maps. 

Selecting Individual Receivers 

Typically, major noise-sensitive public buildings, isolated residences, and relatively small outdoor noisesensitive areas will be selected as individual receivers. Some judgment in selection is required to avoid a 

noise analysis where it is obviously not needed. For example, many roadside motels are not particularly 

sensitive to noise from outdoors. On the other hand, buildings and outdoor areas that the community 

considers to be particularly noise sensitive must be included. Isolated residences that are particularly close to 
 Chapter 5: Detailed Noise Analysis 5-5

the project should certainly be included, while those at some distance may often be omitted or clustered 

together with other land uses, as described in the next section. 

Relatively small outdoor noise-sensitive areas should be evaluated using judgment and common sense. For 

example, playgrounds can often be omitted unless they directly abut the proposed project since noise 

sensitivity in active playgrounds is generally low. 

Clustering Noise-Sensitive Land Uses 

Residential neighborhoods and relatively large outdoor noise-sensitive areas often can be clustered, 

simplifying the analysis without compromising accuracy. These neighborhoods/areas should be subdivided 

into clusters of approximately uniform noise, each containing a collection of noise-sensitive sites. Uniformity 

of both project noise and ambient noise should be attained, guided by these receiver-tosource distance 

considerations: 

• In general, project noise drops off with distance from the project. For this reason, project noise 

uniformity requires nearly equal distances between the project noise source and all points within the 

cluster. Such clusters will usually be shaped as narrow strips parallel to the rail corridor. Clusters within 

which the noise exposure will vary over a range of 2 decibels or less are suggested. The fact that noise 

exposure from rail operations drops off approximately 3 to 4.5 decibels per doubling of distance from the 

tracks, assuming propagation over open terrain, should be used as guidance. The drop-off will be faster 

when rows of buildings, terrain, or other obstacles offer acoustical shielding. 

• Ambient noise usually drops off from non-project sources in the same manner as noise from project 

sources. For this reason, clustering for uniform ambient noise will usually result in long narrow strips 

parallel to major roadways or circling major point sources of ambient noise, such as a manufacturing 

facility. Clusters within which the ambient noise will vary over a range of 3 to 5 decibels or less are 

recommended, though this may be hard to judge without measurements. 

After defining the cluster, one receiver should be selected as representative of the cluster. Generally the 

receiver closest to the project and at an intermediate distance from the predominant sources of existing 

noise should be selected. 

5.1.2 Step 2: Existing Noise Exposure 

In estimating existing noise exposure, one must first decide whether, and how thorough, a noise survey will 

be performed. Some noise monitoring should be performed unless extenuating circumstances make 

measurements impractical. Project schedule, bad weather, and limited budget are typical reasons that 

measurements may not be possible. The most common approach is to use measurements at representative 

sites to characterize existing noise. When measurements are not possible, the existing noise exposure can be 

estimated using Table 4-5 in Chapter 4. A penalty for using the convenient tabular estimates is a built-in 

conservatism in the projections. That is, the projections under-predict the ambient noise somewhat, and 

thereby over-predict relative noise impact. 

Guidelines for noise measurements to characterize existing noise exposure for both residential and 

nonresidential land uses include: 

• For non-residential land uses, measure for 30 to 60 minutes at the receiver, preferably on at least two 

nonsuccessive weekdays (generally between Monday morning and Friday afternoon). Select the hour of 

the day when the project activity is expected to be at a maximum. 

• For residential land uses, measure for a full 24 hours at the receiver for one or more weekday periods 
5-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

(generally between Monday morning and Friday afternoon). 

• Use judgment in positioning the measurement microphone. Location of the microphone at the receiver 

depends upon the proposed location of the high-speed rail alignment. If, for example, a new rail line will 

be in front of the house, do not locate the microphone in the back yard. Recommended measurement 

positions corresponding to various locations of the project source are illustrated in Figure 5-2. 

• Undertake all measurements in accordance with good engineering practice, following guidelines 

contained in ASTM and ANSI Standards.29,30

Figure 5-2 Recommended Microphone Locations for Existing Noise Measurements

Measurements made at representative receivers often are used to estimate noise exposure at other similar 

 

29 American Society for Testing and Materials, "Standard Guide for Measurement of Outdoor A-Weighted Sound Levels," 

E 1014-84, Philadelphia, 1984. 

30 American National Standards Institute, "Method for the Measurement of Sound Pressure Levels," ANSI S1.13-1971 

(R1976), New York, 1971. 
 Chapter 5: Detailed Noise Analysis 5-7

receivers. In other situations, several hourly Leq measurements at a receiver can be used to estimate Ldn. 

Both of these options require the intuition gained from experience and knowledge of acoustics to select

representative measurement sites. 

Measurements at one receiver can be used to represent the noise environment at other sites, but only when 

proximity to major noise sources is similar among the sites. For example, a residential neighborhood with 

otherwise similar homes may have greatly varying noise environments. One part of the neighborhood may be 

located where the ambient noise is clearly due to highway traffic. A second part, toward the interior of the 

neighborhood, may have highway noise as a factor, but also will receive a significant contribution from other 

community noise. In a third part of the neighborhood, located deep in the residential area, local street traffic 

and other community activities could dominate the ambient noise. In this example, three or more 

measurement sites would be required to represent the varying ambient noise conditions in a single 

neighborhood. 

Representative measurement sites typically can be used to estimate noise levels at other sites when both 

share the following characteristics: 

• proximity to the same major transportation noise sources, such as highways, rail lines, and aircraft flight 

patterns, 

• proximity to the same major stationary noise sources, such as power plants, industrial facilities, rail yards 

and airports, and 

• similar type and density of housing, such as single -family homes on quarter-acre lots and multifamily 

housing in apartment complexes. 

Acoustical professionals are often adept at such computations from partial data and are encouraged to use 

their experience and judgment in fully utilizing the measurements in their computations. On the other hand, 

people lacking a background in acoustics should use the procedures in Appendix B to accomplish this same 

aim. The procedures contained in Appendix B are an attempt to systematize such computations from partial 

measurements. As a safety factor, these procedures underestimate ambient noise to account for reduced 

precision compared with full noise measurements. 

5.2 PROJECTIONS OF HIGH-SPEED TRAIN NOISE 

Once receivers have been selected, projections of noise from high-speed trains can be developed for each 

receiver. The subsequent steps in the computation procedure, described in detail in Sections 5.2.1 through 

5.2.5, are: 

Step 3. Source Reference Levels. Establish the type of system for the proposed high-speed rail 

project. Determine the reference SEL, length, and speed relationship for each noise 

subsource on the train. 

Step 4. Project Operating Conditions. Adjust each subsource SEL to the operating conditions of the 

project (consist and speed). 

Step 5. Propagation of Noise to Receivers. Estimate the propagation effects of geometric spreading, 

ground attenuation, and shielding for each subsource SEL to develop an SEL-versus-distance 
5-8 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

relationship. Compute an overall, combined SEL from all subsources for a single train passby 

as a function of distance. 

Step 6. Total Noise Exposure. Use the project's operating parameters to calculate overall noise 

exposure at each receiver from the combined SEL. 

Step 7. Maximum Noise Level for Train Passbys. If necessary, calculate the maximum noise 

Level (Lmax) from a single train passby. Lmax is not used in the assessment of noise impact, 

but may be useful for comparisons with measurement data or project specifications. 

5.2.1 Step 3: Source Reference Levels 

The wayside noise level generated by a high-speed train passby depends primarily on system design and its 

operating conditions. The SEL used to describe a given system under a fixed set of operating conditions 

(speed, consist, track configuration) at a reference distance is called the source reference level. Since a 

number of high-speed rail systems are in existence worldwide, with design variations ranging from the type 

of propulsion mechanism to the car body shape, it is necessary to develop a set of generalized source 

reference levels for use in the prediction model established in this manual. A review of available data 

resulted in grouping all existing high-speed rail systems into the following five categories: 

• High-Speed, Steel-Wheeled Electric 

Electric-powered, locomotive-hauled trains with maximum operating speeds of 150 mph, 

• High-Speed, Steel-Wheeled Fossil Fuel Fossil fuel-powered, locomotive-hauled trains with maximum 

operating speeds of 150 mph, 

• High-Speed, Steel-Wheeled EMU 

Electric-powered multiple unit (EMU) trains with maximum operating speeds of 150 mph, 

• Very High-Speed, Steel-Wheeled Electric 

Electric-powered, locomotive-hauled or EMU trains with maximum operating speed of up to 250 mph, 

and 

• Maglev 

Magnetically-levitated trains with maximum operating speed of 300 mph. 

Once the appropriate system category is selected, the first action in the detailed noise prediction procedure 

for high-speed train passbys is to establish the source reference level and the corresponding reference 

conditions for that category. Depending on the system category, this source reference level can be broken 

down into two or more subsources as described in Chapter 2. These subsources relate directly to the various 

location-specific noise-generating mechanisms on the train, and can be categorized into one of the following 

three component categories: 

• propulsion, 

• mechanical, or 

• aerodynamic noise. 

The relevant subsources and their nominal noise reference levels to be used in computing noise exposure for 
 Chapter 5: Detailed Noise Analysis 5-9

each of the five system categories of high-speed trains are listed in Table 5-2 and for conventional trains in 

Table E-1. In these tables, the reference SEL for each subsource is given for the reference distance of 50 feet 

from the track centerline. Also given in the tables are the definition and reference value of the associated 

length of each subsource; for example, wheel-rail noise is associated with the entire train length, while 

propulsion noise originates only from the power cars. The subsource length is an important parameter, since 

SEL is an energy descriptor and for a train is always defined normalized to some reference length. The 

subsource heights, expressed in terms of the height above the rails (or guideway), are also listed in Table 5-2 

and Table E-1 and are used in evaluating shielding and other propagation effects as described in Section 

5.2.3. 

The levels in Table 5-2 are based on the results of the background measurement and research program that 

preceded the preparation of this manual. That program has resulted in an extensive database of noise data on 

most existing high-speed train systems, ensuring that Table 5-2 is reasonably accurate for the existing 

technologies. However, when specific equipment has been selected for a project, it will be more accurate to 

base the impact assessment on noise measurements of that equipment.31

For some projects, source-noise levels will be pre-defined; for example, noise limits are usually included in 

the specifications for purchase of new vehicles. Compliance with such specifications, almost always defined 

in terms of Lmax, can be checked using the equations found in Appendix C. This option is addressed further in 

Section 5.2.5, accompanied by an example in which noise projections are used to determine compliance with 

a noise specification given in terms of Lmax. 

 

31 As a cautionary note, measurements to obtain reference quantities as in Table 5-2 require special techniques to separate 

subsource components and are beyond the scope of this manual. If single level measurements are performed, methods for converting 

these levels to the simplified reference levels used in the General Assessment procedure (Chapter 4) are given in Appendix C. 
5-10 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

Table 5-2 Source Reference SELs at 50 feet

Subsource Parameters Reference Quantities

System Category and 

Features(a)

Example

Systems

Subsource 

Component

Length

Definition,

len

Height

Above

Rails 

(ft)

SELref

(dBA)

lenref

(ft)

Sref

(mph)

K

Propulsion lenpower 3 75 70 90 15

HS ELECTRIC

• Steel-Wheeled

• High-Speed

• Locomotive-Hauled

• Electric Power

X2000

Talgo 

(electric)

Amtrak Acela

Wheel-rail lentrain 1 85 634 90 28

Propulsion lenpower 10 83 73 20 10

HS FOSSIL FUEL

• Steel-Wheeled

• High-Speed

• Locomotive-Hauled

• Fossil Fuel Power

RTL-2

Talgo (gas 

turbine)

Jet-Train

Wheel-rail lentrain 1 91 634 90 20

Propulsion lenpower 10 86 73 20 1

HS EMU

• Steel-Wheeled

• High-Speed

• Electric Multiple

Units (EMU)

Pendolino

IC-T

Wheel-rail lentrain 1 91 634 90 20

Propulsion lenpower 12 86 73 20 0

Wheel-rail lentrain 1 91 634 90 20

Train Nose lenpower 10 89 73 180 60

Wheel Region lentrain 5 89 634 180 60

VHS ELECTRIC

• Steel-Wheeled

• Very High-Speed

• Locomotive-Hauled

• Electric Power

TGV

Eurostar

ICE

Shinkansen

A

E

R

O Pantograph (b) 15 86 - 180 60

Propulsion lentrain 1.5 68 165 90 8

Guideway/Structural lentrain -5 80 295 90 30

Train Nose lenpower 5 61 20 90 50 MAGLEV TR08 A

E

R

O

TBL(C) lentrain 10 78 82 120 50

(a) HS (High-Speed) = maximum speed 150 mph

 VHS (Very High-Speed) = maximum speed 250 mph

 MAGLEV = maximum speed 300 mph

(b) originates as a point source (no length)

(c) Turbulent Boundary Layer

5.2.2 Step 4: Project Operating Conditions 

Since the source reference levels given in Table 5-2 are for a specific train length and speed, they must be 

normalized to reflect the actual operating conditions of the project. In other words, trains whose consists are 

different from the reference consists assumed in Table 5-2 require conversion since they will produce 

different noise exposure. The same is true for trains at speeds other than those listed in Table 5-2. As 

guidance, a 40 percent change in the number of power cars or coaches per train, or a 15 percent change in 
 Chapter 5: Detailed Noise Analysis 5-11

train speed, will produce an approximate 2-decibel change in noise exposure. 

Once the appropriate system category and reference quantities are established, the following input 

parameters are required to adjust each reference SEL to the appropriate operating conditions: 

• number of passenger cars in the train, Ncars, 

• number of power units in the train, Npower, 

• length of one passenger car, ulencar, 

• length of one power unit, ulenpower, and 

• train speed in miles per hour, S. 

The following equation should be used to adjust each "nth " subsource SEL to the operating conditions 

identified above: 

( )

n

ref

n

ref

n

n ref S

S

K

len

len

SEL SEL 















+

















= + 10 log log

The consist adjustment in the above equation is reflected in the "10 log(len/lenref)" term, where len 

represents the subsource length (lenpower, lentrain) specified in Table 5-2. These variables are defined as: 

, power Npower ulenpower len = × and

( ) ( ).

train N power ulenpower Ncars ulencar len = × + ×

The speed adjustment is given by the "K log(S/Sref)" term, using the appropriate value for K in Table 5-2. 

5.2.3 Step 5: Propagation of Noise to Receivers 

Propagation characteristics must now be considered in order to compute the noise exposure at 

specific receivers, using the project SEL at 50 feet for each subsource as the basis for calculation. 

The sequence in this process are as follows: 

ÿ Determine the propagation characteristics between each subsource and the receiver. 

ÿ Develop an SEL-distance relationship for each subsource. 

ÿ Add a final adjustment using the appropriate shielding term based on intervening barriers and/or 

terrain features between subsource and receiver. 

The steps required to carry out this sequence, resulting in calculation of a specific noise exposure-versusdistance relationship for each noise subsource, are described below: 

1. Set up cross-sectional geometries: Draw several approximate topographic sections, each 

perpendicular to the path of moving sources or radially outward from point sources, similar to 

those shown in Figure 5-3. Draw separate sections, if necessary, to account for significant changes 

in topography and/or track geometry. Use judgment to reasonably limit the number of cross 

sections required. 

2. Estimate Ground Effects:32 For each topographic cross section, use the relationships illustrated in 

Figure 5-3 to determine the effective path height, Heff, and from it the ground factor, G, for the 

 

32 Ontario Ministry of Environment, “ORNAMENT: Ontario Road Noise Analysis Method for Environment and Transportation,” 

November 1988.
5-12 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

wheel-rail and propulsion noise subsources only. For aerodynamic noise subsources, ground 

absorption has little attenuating effect and can be disregarded. 

Larger values of G mean larger amounts of ground attenuation with increasing distance from the 

source. As shown in Figure 5-3, Heff depends upon subsource heights, which are defined in terms of 

height above rails in Table 5-2, and upon receiver heights, which is usually taken as 5 feet above 

ground for both outdoor receivers and first floor receivers. 

Because of the different effective source heights for the wheel-rail and propulsion noise subsources, 

each will have a different Heff and therefore ground factor. For acoustically "hard" (i.e., 

nonabsorptive) ground conditions, and for all aerodynamic noise subsources, G should be taken to be 

zero. Application of the computations in Figure 5-3 is restricted to topographies for which horizontal 

distances are much greater than the vertical distances. In cases where the vertical distance, such as 

the elevation of the source or receiver, is of the same order of magnitude as any of the horizontal 

distances, G can be taken as zero if the line of sight is unbroken. Otherwise use the shielding method 

described in the next step. 

3. Estimate Shielding due to Terrain and Noise Barriers: If the line of sight between subsource and 

receiver is unbroken, calculation of the ground factor (G) alone is sufficient to describe the attenuation 

of noise with increasing distance. However, if shielding between source and receiver in the form of 

intervening noise barriers and/or terrain features due to natural topography or to track geometry (e.g., 

track in cut or on embankment) breaks the line of sight, an additional attenuation must be included in 

the calculation of propagation effects. 

Equations for computing the attenuation due to shielding (Ashielding) are provided in Table 5-3 for the 

basic cross-sectional geometry shown in the figure at the bottom of the table. This fundamental sourcebarrier-receiver geometry can also be used to model the barrier effect of terrain features that protrude 

above the line of sight, such as the edge of a deep cut, an embankment, or an earth berm. Examples of 

application of the shielding model are shown in Figure 5-4. 
 Chapter 5: Detailed Noise Analysis 5-13

IN GENERAL: Heff = sum of average path heights on either side of barrier

Hb = 0 for no barrier

2

s 2 b r

eff

H H H

H

+ +

= (1)

2

2

,

2

s b c r

eff

H H H H

H

ForB A

+ + +

=

<

Example 1: Source in shallow cut

*Otherwise use Equation (1)

2

2

,

s b c r

eff

b c

H H H H

H

ForH H

+ − +

=

>

Example 2: Receiver elevated

2

,

s c r

eff

b c

H H H

H

ForH H

+ +

=

<

(1)

,

2

useEquation

Example 3: Source in sloped cut ForA< B

2

2

,

2

s b c r

eff

H H H H

H

ForA B

+ + +

=

>

2

2

,

2

s c r

eff

H H H

H

ForA B

+ +

=

>

Example 4: Source and receiver separated by trench

2

,

2

s r

eff

H H

H

ForA B

+

=

<

Ground Factor

For soft ground:

42

5 42

5

42

1

0

0.75

0.66

>

< <

<



























= −

eff

eff

eff

eff

H

H

H

H

G

For hard ground:

G = 0

Notes:

Values for Sub-Source Heights (Hs) are given in 

Table 5-2

Equations for Heff remain valid even when Hb=0.

Figure 5-3 Computation of Ground Factor G for Ground Attenuation
5-14 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

Table 5-3 Computation of Shielding: Barriers and Terrain

Subsource Type Equation for Barrier Attenuation

PROPULSION [ ] 































+

















= 5

tanh 4.46

2.51 min 15 20 log

P

P

A or barrier

WHEEL-RAIL [ ] 































+

















= 5

tanh 6.27

3.54 min 20 20 log

P

P

A or barrier

AERODYNAMIC [ ] 































+

















= 5

tanh 2.22

1.25 min 15 20 log

P

P

A or barrier

Barrier Insertion Loss:

( ) 











= = − −

50

10 log DAshielding ILbarrier Abarrier GNB GB

D = closest distance between the receiver and the source, in feet

P = path length difference, in feet (see figure below)

GNB = Ground factor G computed without barrier (see Figure 5-3)

GB = Ground factor G computed with barrier (see Figure 5-3)

Basic Cross-Sectional Geometry:

( )

2 2 A DSB H B H S

P A B C

= + −

= + −

( )

2 2

B = DBR + H B − H R

( ) ( )

2 2

C = DSB + DBR + HS − H R
 Chapter 5: Detailed Noise Analysis 5-15

Figure 5-4 Barrier Geometry Models of Terrain for Computation of Shielding
5-16 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

4. Calculate SEL versus Distance: For each subsource SEL at 50 feet developed earlier in the analysis, plot a 

noise exposure-versus-distance curve, with SEL represented on the vertical axis and distance on the 

horizontal axis, by evaluating one of the following equations over a range of distances D: 

at ft Ashielding

D

G

D

SEL SEL −















−















= −

42

10 log

50

50 10 log For wheel-rail subsources

 at ft Ashielding

D

G

D

SEL  −











 −











= −

29

10 log

50 50 10 log For propulsion subsources

 at ft Ashielding

D

SEL  −











= −

50 50 10 log For aerodynamic subsources

5.2.4 Step 6: Cumulative Noise Exposure 

The procedures followed in Step 5 (Section 5.2.3) result in calculation of subsource SELs as a function of 

distance from the project corridor. The next step is to combine the subsources to yield a total SEL value for a 

train passby and convert from SEL to a measure of cumulative noise exposure based on a specific operating 

schedule. As guidance, a 40 percent change in either the number of trains per hour or the number of trains per 

day will produce an approximate 2-decibel change in cumulative noise exposure (Leq or Ldn). The procedure is 

as follows: 

1. Total Passby SEL: Calculate the total passby SEL by combining the subsource SELs obtained following 

Step 4 (Section 5.2.2), using the third equation in Table 5-4. The equations for subsource SEL at 50 feet 

and at distance D are repeated in Table 5-4 for clarity and to illustrate the continuity of the procedure.

2. Noise-Sensitive Hours: Determine the relevant time periods for all receivers that may be affected by the 

project. For residential receivers, the two time periods of interest for computation of Ldn are: daytime 

(7:00 a.m. to 10:00 p.m.) and nighttime (10:00 p.m. to 7:00 a.m.). For non-residential receivers, choose 

the loudest project hour during noise-sensitive activity. Several different hours may be of interest for 

non-residential receivers, depending on the hours the facility is used.

3. Train Operations: Determine number of trains per hour. 

For residential receivers: 

Vd, the average hourly daytime (7 a.m. to 10 p.m.) train volume, and 

Vn, the average hourly nighttime (10 p.m. to 7 a.m.) train volume.

For non-residential receivers: 

V, the hourly train volume for each hour of interest. 

4. Hourly Leq: Compute Leq(h) using the fourth equation in Table 5-4 for each hour of interest.

5. Day-Night Sound Level (Ldn): If the project noise will affect any residential receivers, compute the total 

train Ldn using the last three equations in Table 5-4. 
 Chapter 5: Detailed Noise Analysis 5-17

Table 5-4 Computation of Leq and Ldn

Quantity Equation

n

th Subsource†

Subsource SEL

at 50 ft:

( )

















+

















= +

ref

n

ref

n

n ref S

S

K

len

len

SEL SEL 10 log log

for Wheel/Rail Subsources

for Propulsion Subsources

Subsource SEL 

at distance D:



















 −











−

 −











 −











−

 −











 −











−

=

n at ft shielding

n at ft shielding

n at ft shielding

n

A

D

SEL

A

D

G

D

SEL

A

D

G

D

SEL

SEL

50

10 log

29

10 log

50

10 log

42

10 log

50

10 log

50

50

50

for Aerodynamic Subsources

N Subsources:

Total SEL for train 

passby:





















= ∑=

10

1

10 log 10

SELi

N

i

SEL

Hourly Leq: ( ) ( ) Leq h = SEL + V − 6 − Aexcess 10log 35.

Daytime Leq: ( ) ( ) eq eq V Vd

L day L h ==

Nithttime Leq : ( ) ( ) eq eq V Vn

L night L h ==

Ldn:

( ) ( ( ) )

10 log 15 10 9 10 13.8

10

10

10 −

















= ⋅ + ⋅

L day L night +

dn

eq eq

L

V = average hourly volume of train traffic, in train per hour

Vd = average hourly daytime volume of traffic, in trains per hour

 = number of trains, 7 am to 10 pm

15

Vn = average hourly nighttime volume of train traffic, in trains per hour

 = number of trains, 10 pm to 7 am

9

† See Section 5.2.2 for definition of terms
5-18 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

6. Excess Shielding: If necessary, adjust for excess shielding. At this point, excess shielding (Aexcess) that 

is site-specific and not directly related to the vertical geometry of the source relative to the receiver (as 

computed in Step 5) can be applied to the overall noise exposure. Such excess shielding can be caused 

by intervening rows of buildings, dense tree zones, and any other obstruction between the source and 

the receiver. The attenuations are applied to overall L

eq

 and Ldn and not to the individual subsource 

contributions. Equations for computing these attenuations are given in Table 5-5. 

Table 5-5 Computation of Excess Shielding: Rows of Buildings and Dense Tree Zones

Condition Equation

If gaps in the row of buildings constitute less than 35 

percent of the length of the row: Abuildings = min {10 or [1.5 (R-1) + 5]}

If gaps in the row of buildings constitute between 35 and 

65 percent of the length of the row:

 = min {10 or [1.5 (R-1) + 3]}

If gaps in the row of buildings constitute more than 65 

percent of the length of the row:

 = 0

Where at least 100 feet of trees intervene between source 

and receiver, and if no clear line-of-sight exists between 

source and receiver, and if the trees extend 15 feet or more 

above the line-of-sight:

Atrees = min 











20

10 Wor

If above conditions do not occur: Atrees = 0

NET ATTENUATION Aexcess = max {Abuildings or Atrees}

R =

W =

Number of rows of houses that intervene between source and receiver

Width of the tree zone along the line-of-site between source and receiver, in feet

An example of application of Steps 1 through 6 of the Detailed Noise Analysis procedure for a 

hypothetical proposed high-speed rail project follows. 

Example 5-1. Detailed Noise Projection Procedure 

Consider the following system:

Proposed Equipment: The project will use a steel-wheeled electric train with 2 power cars (one on each 

end) and 8 passenger coaches. The maximum design speed will be 180 mph, placing it in the “Very 

High-Speed” category in Table 5-2. The locomotives are 73 feet long each, and the cars are each 61 

feet long. 

Proposed Service: Hours of revenue service from 5:00 a.m. to midnight. Hourly volumes are:

Daytime (7 a.m. to 10 p.m.):

Vd = 4 trains/hour

Nighttime (10 p.m. to 12 p.m., 5 a.m. to 7 a.m.):

Vn = 1 train/hour

In the corridor segment of concern, the train will pass through a deep cut with sloped walls, and we are 

concerned with the sound exposure at a 5-foot receiver standing 80 feet from the edge of the cut (200 feet 
 Chapter 5: Detailed Noise Analysis 5-19

from the centerline of the near track).

The geometry is illustrated in case 3 of Figure 5-3, with the following parameter values:

A = 105 feet

B = 200 feet

Hr = 5 feet

Hc = 49 feet

Hb = 0 feet, and

Hs = subsource heights as given in Table 5-2 for Very High-Speed trains.

1. Calculate the ground factor, G, for the wheel-rail and propulsion subsources using the equations in 

Figure 5-3:

Heff = 

2

H S + 2Hb + Hc + Hr

= 

( ) ( ) ( ) ( )

2

1 + 2× 0 + 49 + 5

 = 27.5 for wheel-rail

and, Heff = 

( ) ( ) ( ) ( )

2

12 + 2 × 0 + 49 + 5

= 33 for propulsion.

Using the equation for G, again from Figure 5-3,

G = .75 















−

42

1

Heff

 =.75 











−

42

27.5

1 = .26 for wheel-rail

and, = .75 











=

42

33 1 = .16 for propulsion.

2. Since the line of sight between the receiver and the source may be broken by the cut (see Figure 5-

4(b)), determine the shielding due to the terrain. Using the geometry from Table 5-3, with the barrier 

height represented by the height of the cut, 

DSB = 120 feet,

DBR = 80 feet,

HR = 54 feet (receiver height + height of cut),

HB = 49 feet, and

HS = heights of wheel-rail, propulsion, and aerodynamic subsources from Table 5-2.

Use these values to obtain the lengths A, B, C, and P in Table 5-3:

Propulsion Wheel-Rail Train Nose Wheel Region Pantograph 

A 125.6 129.2 126.2 127.8 124.7 

B 80.2 80.2 80.2 80.2 80.2 

C 204.4 206.9 204.8 205.9 203.8 

P 1.4 2.5 1.6 2.1 1.1 
5-20 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

Insert the path length difference, P, into the equations for Barrier Attenuation from Table 5-3, 

which yields:

Abarrier,propulsion = 14.4,

Abarrier,wheel-rail = 20.0,

Abarrier,train nose = 8.9,

Abarrier,wheel region = 10.1, and

Abarrier,pantograph = 7.6.

Solve for the insertion loss using the fourth equation in Table 5-3. Because this system does not 

have a man-made barrier, set GNB and GB=0. This yields:

Ashielding,propulsion = 14.4,

Ashielding,wheel-rail = 20.0,

Ashielding,train noise = 8.9,

Ashielding,wheel region = 10.1, and

Ashielding,pantograph = 7.6.

3. To calculate the noise exposure as a function of distance, normalize the reference quantities in Table 5-

2 to the actual operating conditions of the proposed system, using the method from Section 5.2.2. This 

results in the following subsource SELs:

Propulsion = 89 dBA,

Wheel-rail = 97 dBA,

Train nose = 92 dBA,

Wheel region = 89 dBA, and

Pantograph = 86 dBA.

Using these values, evaluate the equations in section 5.2.3 at a distance of 200 feet at each subsource. 

Add the subsource SELs together to obtain the total SEL exposure. A plot of the total SEL versus 

distance for this example is given below. At 200 feet, the sound exposure level at the receiver will be 

about 80 dBA.
 Chapter 5: Detailed Noise Analysis 5-21

SEL vs. Distance

Train in Cut

4. Using the Leq and Ldn equations in Table 5-4, compute the cumulative noise exposure at the receiver:

Leq(day) = 51 dBA,

Leq(night) = 45 dBA, and

Ldn = 52 dBA.

End of Example 5-1

5.2.5 Step 7: Maximum Noise Level for Train Passbys 

Noise impact assessment in this manual is based on either Ldn or L

eq

; therefore, normally it is not necessary to 

determine and tabulate the maximum levels (Lmax). However, often it is desirable to include estimates of Lmax

since:

• it is representative of what people hear at any particular instant; 

• it is straightforward to measure with a standard sound level meter; 

• noise limits in vehicle specifications are usually in terms of Lmax; and 

• because Lmax represents the sound level heard during a transportation vehicle passby, people can related 

this metric with other environmental noises, such as an aircraft flyover or a truck passby. 

Although Lmax is not used in this manual as a basis for assessing noise impact, when used in conjunction 

with L

eq

(h) or Ldn it can provide a more complete description of the noise effects of a proposed project. Lmax

also may be necessary in determining compliance with the project noise limits. Equations for

computing Lmax from SEL and also for estimating a single reference SEL (for use in the General Assessment 

method presented in Chapter 4) from a specified or measured value of Lmax are given in Appendix C. 

Application of these equations is illustrated in Example 5-2. 
5-22 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

Example 5-2. Calculation of Lmax using Detailed Noise Analysis Procedure

This example demonstrates how to compute Lmax combining the methods described in Chapter 5 and the 

equations given in Appendix C. The segment in question will utilize an electric locomotive-hauled train with 

a maximum design speed of 150 mph, which places it in the “high speed” category of Table 5-2. The land 

abutting the rail corridor is flat with no shielding, and the tracks are on a 3-foot high embankment. The 

receiver is assumed to be 5 feet high, and the noise specification requires Lmax at a distance of 50 feet away 

from the centerline of the tracks. The trainset is made up 2 power units (one at each end of the set) and 10 

passenger coaches. The parameters for this train are,

SELref,propulsion = 86 dBA,

SELref,wheel-rail = 91 dBA,

Nlocos = 2,

Ncars = 10,

Llocos = 73 feet,

Lcars = 61 feet,

Ltotal,locos = 146 feet,

Ltotal,cars = 610 feet,

S= 150 mph, and

D= 50 feet.

The SELs for each subsource must be computed for the proposed consist ands peed using the methods 

described in section 5.2. Then, Lmax from each subsource can be calculated using the equations in 

Appendix C. The highest subsource Lmax is used in the noise specification for this trainset.

First, the effective path heights must be calculated to determine the ground attenuation. As shown in Figure 

5-3, the effective ground height is 

Heff =(Hs+2Hb+Hr)/2

so Heff = 4.5 for the wheel-rail subsource, and

Heff = 9 for the propulsion subsource.

This corresponds to 

G = .66 for the wheel-rail subsource, and

G = .59 for the propulsion subsource.

The reference parameters given in Table 5-2 must now be adjusted to actual speed and distance conditions by 

using the equations from section 5.2.2. It should be noted that for cases where the locomotives are located on 

opposite ends of the train, they should be treated separately; the equations in Section 5.2.2 assume the 

locomotives are in groups. In other words,

SELpropulsion = SELref, propulsion+10log (73/73) +15log (150/20)

= 99.1

for each power unit, and

SELwheel/rail = SELref,wheel/rail +10log((146+610) / 634) + 20log(150/90)

= 96.2

for the wheel/rail component of the train. 

Using the equations in section 5.2.3, the SEL at 50 feet for each power unit is:
 Chapter 5: Detailed Noise Analysis 5-23

SEL = SELpropulsion- 10log 











50

D

- 10G log 











29

D

, which yields

SEL = 99.1 – 10log 











50

50

- 10 (.59) log 











29

50 = 97.7

and for the wheel-rail subsource is:

SEL = SELwheel/rail – 10log 











50

D

- 10G log 











42

D

, which yields

SEL = 96.2 – 10log 











50

50

- 10 (.66) log 











42

50 = 95.7

These SELs can now be used in the equations given in Table C-1. First, ∝ corresponding to 

propulsion and wheel/rail noise must be calculated: 

∝ = arctan (L/2D)

 = .63 for propulsion noise and

= 1.4 for wheel/rail noise.

Then,

Lmax,propulsion = 97.7-10log(73/150)+10log(2x.63)-3.3

= 98.5 dBA, or 99 dBA (rounded)

Lmax,wheel/rail = 95.7-10log(610/150)+10log[(2x1.44)+sin(2x1.44)]-3.3

= 91.3 dBA, or 91 dBA (rounded).

The total Lmax is the largest of the two:

Lmax,total = 99 dBA.

End of Example 5-2

5.3 STEP 8: NOISE IMPACT ASSESSMENT 

This section outlines procedures for assessing noise impact using the existing and projected noise results 

developed using the methodologies described in the previous sections. These procedures can be applied not 

only to noise impact from high-speed train operations, including projects built within a highway or railroad 

corridor, but also to impacts from fixed facilities such as storage and maintenance yards, passenger stations 

and terminals, parking facilities, and substations. 

5.3.1 Assessment Procedure 

Noise impact should be assessed at each receiver of interest using the criteria for high-speed train projects 

described in Chapter 3 as follows: 

1. Existing Noise Exposure . Tabulate existing ambient noise exposure (rounded to the nearest whole 

decibel) at all receivers of interest identified earlier in the analysis. 

2. Project Noise Exposure . Tabulate project noise exposure at these receivers using the analytical 

procedures described in this chapter. In the tabulation, account for added annoyance from startle for 

receivers located within the distances given in Figure 4-2 (Chapter 4). 

3. Noise Impact Criteria. Determine the level of noise impact (No Impact, Moderate Impact or Severe 
5-24 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

Impact) by comparing the existing and project noise exposure based on the impact criteria in Chapter 3. 

4. Noise Impact Inventory. Document the results in noise-assessment inventory tables. These tables should 

include the following types of information: 

• receiver identification and location, 

• land-use description, 

• number of noise-sensitive sites represented (usually the number of residential buildings or 

dwelling units), 

• closest distance to the project, 

• existing noise exposure, 

• project noise exposure, 

• level of noise impact (No Impact, Moderate Impact or Severe Impact), and 

• potential for startle. 

In addition, these tables should indicate the total number of receivers predicted to experience Impact or 

Severe Impact. 

5. Graphical Illustration of Noise Impact. Illustrate the areas of Moderate Impact and Severe Impact on 

maps or aerial photographs. This illustration could consist of noise impact contours on the maps or aerial 

photographs, along with the impact areas highlighted. This is done by delineating two impact lines: one 

between the areas of No Impact and Moderate Impact and the second between Moderate Impact and 

Severe Impact. To conform with the practices of another agency (e.g., FHWA, FAA), include several 

contour lines of constant project noise, such as Ldn 65, Ldn 70 and Ldn 75. 

6. Magnitude of Noise Impact. Determine the magnitude of the impacts as the basis of the assessment, 

defined by the two threshold curves delineating onset of Moderate Impact and Severe Impact. 

Interpretation of the two impact regimes is discussed in Chapter 3. 

7. Maximum Noise Level. Evaluate and tabulate Lmax at sensitive receivers and locations where SEL 

exceeds the interim criteria for effects on animals as discussed in Chapter 3. 

5.3.2 Example of GIS Implementation 

Geographic Information System (GIS) technology can be a useful tool in graphically identifying and 

displaying noise impacts, as well as simplifying the mapping and inventorying work that is needed to 

complete the impact assessment. While development of a GIS method was not within the scope of this 

manual, an example showing a conceptual method of implementing GIS is given in this section. 

The GIS example utilizes the parameters of Alignment Alternative 1 in Example 4-1 (Chapter 4). This 

corridor will use a high-speed electric trainset with a maximum speed of 180 mph, passing through a rural 

area with scattered residences, as shown in Figure 5-5. 

Procedure 

The screening procedure calls for further analysis for noise-sensitive land use within 1,000 feet of a new 

corridor. Using GIS, the procedure is as follows: 

Step 1. Digitize GIS Input Map. Input a diagram of the project area into the GIS by digitizing a map, 

using aerial or satellite photography, CAD, or other methods. The GIS will determine grade 
 Chapter 5: Detailed Noise Analysis 5-25

crossings, embankments and cuts from topographic contours. Environmental features such as 

dense foliage are selected by choosing the appropriate icon and applying the feature to the 

map. 

Step 2. Identify the sensitive receivers. Identify and label all sensitive land uses by address and

owner, either manually, or by importing the information from a database. Distances from 

each receiver to the track will be computed automatically. 

Step 3. Input train parameters. Obtain train data such as speed, type and number of cars for input to 

the noise propagation model, which is linked to the GIS. As demonstrated in Example 4-1 

(Chapter 4), the onset for impact and severe impact is 990 and 350 feet, respectively. The GIS 

will automatically calculate the distances for impact and severe impact, and draw the noise 

contours as shown in Figure 5-5. 

Step 4. Assess impact at specific receivers. Predictions of noise and vibration levels at specific 

receivers will also be calculated automatically using the noise contour information obtained. 

To view statistics for a certain residence, select the residence and a dialog box will appear, 

providing receiver information including address, owner, and projected noise and vibration 

levels from high-speed trains. 

Step 5. Input new parameters. To view the effects of different train configurations and/or speeds, 

input the new parameters into the GIS and the model will redraw new impact contours and 

update the noise and vibration levels at each receiver. 

Once the receiver and geographic information has been entered into the system, it is possible to change any 

number of variables, including track position, train configuration, and shielding and receive updated noise 

and vibration predictions with little effort. Use of GIS technology also allows residents who live near a 

corridor to see the specific impact that a train project would have on them.
5-26 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

Figure 5-5 Determining Noise Impact using GIS

5.4 MITIGATION OF NOISE IMPACT 

This section provides guidance for evaluating noise reduction measures at locations where the noise impact 

assessment shows either Severe Impact or Moderate Impact. Severe Impacts are likely to generate 

considerable annoyance and activity interference and are therefore considered to be adverse effects in the 

context of most environmental regulations. Consequently, remedies in terms of alternative alignments or 

mitigation measures must be proposed and analyzed for locations for which impacts are assessed to be 

severe. The more “Moderate” Impact category ranges from Threshold to Severe. In this range, other factors 

may be considered, such as costs and benefits, practicality, prior exposure, severity of impact, and land use 

sensitivity in decisions regarding the application of noise mitigation. In general, mitigation options are chosen 

from those listed below, and then relevant portions of the project noise are recomputed and reassessed to 

account for this mitigation. This reassessment provides an accurate prediction of the noise reduction and the 
 Chapter 5: Detailed Noise Analysis 5-27

resulting net impact of the project, assuming the incorporation of mitigation measures either in the initial 

project plans by the project proponent, or as a condition imposed by the approving public agency. 

The source levels used in this manual are typical of high-speed train systems designed according to current 

engineering practice, but they do not include special noise control features that could be incorporated in the 

specifications at extra cost (e.g., wheel skirts, pantograph shrouds). Such measures could further reduce 

noise impact and warrant consideration by project proponents and public agencies where the Initial Noise 

Evaluation indicates the potential for extensive areas of severe impact. 

Mitigation of noise impact from high-speed train projects may involve treatments at the three fundamental

components of the noise problem: (1) at the noise source, (2) along the source-to-receiver propagation path, 

or (3) at the receiver. A list of practical noise mitigation measures that should be considered is summarized in 

Table 5-6. This table is organized according to whether the treatment applies to the source, path, or receiver, 

and includes estimates of the acoustical effectiveness of each treatment. The treatments are discussed in 

Sections 5.4.1 through 5.4.3. Note the mitigation treatments are not additive within each group. Professional 

judgment is required to determine the total effectiveness, but one can usually add the effectiveness of one 

treatment from each group. 

5.4.1 Source Treatments 

Vehicle Noise Specifications 

Incorporating noise control features during the specification and design of the vehicle is among the most 

effective noise mitigation treatments. The development and enforcement of stringent but achievable noise 

specifications by the project sponsor is a major step in controlling noise everywhere on the system. It is 

important to ensure that noise levels quoted in the specifications are achievable with the application of best 

available technology during the development of the vehicle and reasonable in light of the noise reduction 

benefits and costs. Effective enforcement includes imposing significant penalties for noncompliance with the 

specifications. 

Wheel Treatments 

A major source of noise from steel-on-steel high-speed train systems is the wheel-rail interaction, which has 

three components: roar, impact, and squeal. Roar is the rolling noise caused by small-scale roughness on the 

wheel tread and rail running surface. Impacts are caused by discontinuities in the running surface of the rail 

or by flat spots on the wheels. Squeal occurs when a steel-wheel tread or its flange rubs across the rail, setting 

up resonant vibrations in the wheel, which cause it to radiate a screeching sound.

Various wheel designs and other mitigation measures to reduce the noise from each of these three 

mechanisms include: 

• Resilient and damped wheels to reduce rolling noise, but only slightly. A typical reduction is 2 decibels 

on tangent track. This treatment is more effective in eliminating wheel squeal in tight curves; reductions 

of 10 to 20 decibels for high frequency squeal noise is typical. 

• Spin-slide control systems, similar to anti-locking brake systems on automobiles, reduce the incidence 

of wheel flats (localized flat spots on wheels), a major contributor of impact noise. Trains with smooth
5-28 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

wheel treads can be up to 20 decibels quieter than those with wheel flats. To be effective, the anti-locking 

feature should be in operation during all braking phases, including emergency braking. Wheel flats are 

more likely to occur during emergency braking than during dynamic braking.

• Maintenance of wheels by truing eliminates wheel flats from the treads and restores the wheel profile. 

An effective maintenance program includes the installation of equipment to detect and correct wheel flats 

on a continuing basis. 

Table 5-6 High Speed Train Noise Mitigation Measures

Application Mitigation Measure Effectiveness

Stringent Vehicle & Equipment Noise Specifications Varied

Placement of HVAC systems Varied

Sound-Absorptive Duct Lining for Air Intake/Exhaust Varied

Operational Restrictions Varied

Resilient or Damped For Rolling Noise on Tangent Track: 2 dB

Wheels

For Wheel Squeal on Curved Track: 10-20 dB

Vehicle Skirts 6-10 dB

Under-car Absorption 5 dB

Spin-slide control (prevents flats) **

Wheel Truing (eliminates wheel flats) **

Rail Grinding (eliminates corrugations) **

Turn Radii greater than 1000 ft (Avoids Squeal)

Rail Lubrication on Sharp Curves (Reduces Squeal)

Movable-point Frogs (reduce rail gaps at crossovers) (Reduces Impact Noise)

Elimination of all surface discontinuities/edges on Vehicle Body 3-6 dB

SOURCE

Pantograph cover or shroud 5 dB

Sound Barriers close to Vehicles 6-10 dB

Sound Barriers at ROW Line 5-8 dB

Alteration of Horizontal & Vertical Alignments Varied

Acquisition of Buffer Zones Varied

Ballast on At-Grade Guideway 3 dB

Ballast on Aerial Guideway 5 dB

PATH

Resilient Track Support on Aerial Guideway Varied

Acquisition of Property Rights for Construction of Sound Barriers 5-10 dB RECEIVER

Building Noise Insulation 5-15 dB

**These mitigation measures work to maintain a high-speed rail system in its as-new condition. Without incorporating 

them into the system, noise levels could increase by up to 10 dB.

Vehicle Treatments 

Vehicle noise mitigation measures are applied to the various mechanical systems associated with 

propulsion, ventilation, and passenger comfort; these include: 

• Propulsion systems of high-speed train vehicles include electric traction motors and fossil fuel turbine 

engines. Noise from the propulsion system depends on the type of unit and the level of noise mitigation is 

built into the design. 

• Ventilation requirements for vehicle systems are related to the noise generated by a vehicle. Fan noise 

often remains a major noise source after other mitigation measures have been instituted because of the 

need to have direct access to cooling air. This problem applies to heat exchangers for electric traction 
 Chapter 5: Detailed Noise Analysis 5-29

motors and air-conditioning systems. Fan quieting can be accomplished by installation of one of several 

new designs of quiet, efficient fans. Forced-air cooled electric traction motors can be quieter than selfcooled motors at operating speeds. Placement of fans on the vehicle can make a significant difference in 

the noise radiated to the wayside or to patrons on the station platforms. 

• The vehicle body design can provide shielding and absorption of the noise generated by the vehicle 

components. Acoustical absorption under the car has been demonstrated to provide up to 5 decibels of 

mitigation for wheel-rail noise and propulsion-system noise on rapid transit trains33. Similarly, vehicle 

skirts over the wheels can provide more than 5 decibels of mitigation. By providing their own noise 

barriers, vehicles with these features can provide cost-effective noise reduction. 

Guideway Support 

The smoothness of the running surface is critical in the mitigation of noise from a moving vehicle. Due to the 

high train speeds, smooth rail running surfaces are essential for controlling noise at acceptable levels on highspeed rail systems. Roughness of rail surfaces can be eliminated by grinding rails, thereby reducing noise 

levels by up to 10 decibels. 

Operational Restrictions 

Restrictions on operations are not a desirable mitigation option because of service demands. However, in 

extreme cases they can be a viable option. Two changes in operations that can mitigate noise are decreasing 

speed in selected, noise-sensitive areas and reducing nighttime (10 p.m. to 7 a.m.) operations. Because noise 

from high-speed trains depends on speed, a reduction of speed results in lower noise levels. The effect can be 

considerable. For example, each halving of speed on a steel-wheel/steel-rail system results in a 6 dB 

reduction in noise exposure (see Table 5-2). Complete elimination of nighttime operations has a strong effect 

on reducing the Ldn, because nighttime noise is increased by 10 decibels when calculating Ldn. 

It is expected that most new high-speed train systems will be grade-separated, eliminating the need for 

grade crossings and their associated noise levels. However, when grade crossings are present in lowerspeed track segments, other operational restrictions that can reduce noise impact include minimizing or 

eliminating horn blowing and other types of audible warning signals. These mitigation options must be 

compliant with FRA safety regulations and guidelines. 

5.4.2 Path Treatments 

Sound Barriers 

Sound barriers are probably the most common noise mitigation measure used in surface transportation 

modes. Sound barriers are effective in mitigating noise when they break the line-of-sight between source and 

receiver. The mechanism of sound shielding is described in Chapter 2. The necessary height of a barrier 

depends on factors such as the source height and the distance from the source to the barrier. For example, a 

barrier located very close to the nearest track need only be 3 to 4 feet above the top of rail to effectively 

 

33 C.E. Hanson, “Noise Control for Rapid Transit Cars on Elevated Structures,” Journal of Sound and Vibration 87 (2):

285-294 (1983).
5-30 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

reduce wheel-rail noise, providing noise reductions of 6 to 10 decibels. The height of barriers farther away 

from the adjacent track, such as on the right-of-way line or for trains on the far track, or for screening many 

aerodynamic noise sources, must be increased to provide equivalent effectiveness. Otherwise, the 

effectiveness of the barrier could drop to 5 decibels or less, even if it breaks the line of sight. Where the 

barrier is very close to the vehicle or where the vehicles travel between sets of parallel barriers, barrier 

effectiveness can be increased by as much as 5 decibels by applying sound-absorbing material to the inner 

surface of the barrier. 

Similarly, the length of the barrier wall is important in its effectiveness. The barrier must be long enough to 

screen out a moving train along most of its visible path. This length is necessary so that train noise from 

beyond the ends of the barrier will not severely compromise noise-barrier performance at sensitive 

locations.

Noise barriers can be made of any outdoor weather-resistant solid material that meets a minimum sound 

transmission loss requirement. The sound requirements are not particularly strict; they can be met by many 

commonly available materials, such as 16-gauge steel, 1-inch-thick plywood, and any reasonable thickness 

of brick or concrete. The normal minimum requirement is a surface density of 3 pounds per square foot. To 

sustain wind loads, structural requirements are more stringent. Most importantly, achieving the maximum 

possible noise reduction requires careful sealing of gaps between barrier panels and between the barrier 

and the ground or elevated guideway deck.

Costs for noise barriers, based on highway installations, range from $15 to $25 per square foot of installed 

noise barrier at-grade, not counting design and construction inspection costs. The cost of installation on an 

aerial structure is approximately the same as at-grade, unless the structure has to be strengthened to 

accommodate the added weight and wind load.

Locating a train alignment in a reasonably deep cut or trench, as part of a grade separation, can accomplish 

the same result as installing a noise barrier. The walls of the trench serve the same function as barrier walls 

in breaking the line-of-sight between source and receiver.

Noise Buffers 

Because noise levels attenuate with distance, increasing the distance between noise sources and the 

closest sensitive receivers can be an effective mitigation measure. This buffer can be accomplished by 

locating alignments away from sensitive sites. In areas of severe impact, acquiring land or easements for 

noise buffer zones is an option that may be considered.

Ground Absorption 

Propagation of noise over ground is affected by whether the ground surface is absorptive or reflective. Noise 

from vehicles at-grade is strongly affected by the character of the ground in the immediate vicinity of the 

vehicle. Guideways for train systems can be either reflective or absorptive, depending on whether they are 

concrete or ballast. Ballasted track construction can reduce train noise 3 decibels at-grade and up to 5 

decibels on aerial structure.
 Chapter 5: Detailed Noise Analysis 5-31

5.4.3 Receiver Treatments

Sound Barriers 

In certain cases it may be possible to acquire limited property rights for the construction of sound barriers at 

the receiver. As discussed above, barriers need to break the line of sight between the noise source and the 

receiver to be effective and are most effective when they are closest to either the source or the receiver. 

Procedures for estimating barrier effectiveness are given earlier in this chapter.

Building Insulation 

In cases where rights-of-way are restricted, the only practical noise mitigation measure may be to provide 

sound insulation for the building. The most effective treatments are to caulk and seal gaps in the building 

envelope and to install windows that are specially designed to meet acoustical transmission-loss 

requirements. These windows are usually made of multiple layers of glass and are beneficial for heat 

insulation as well as for sound insulation. Depending on the quality of the original windows, the new 

windows can provide noise reductions of 5 to 15 decibels. Such windows are usually nonoperable so that 

central ventilation or air conditioning would be needed. Additional sound insulation, if needed, can be 

provided by sealing vents and ventilation openings and relocating them to a side of the building away from 

the noise source. 
5-32 High-Speed Ground Transportation Noise and Vibration Impact Assessment 
Chapter 6: Ground-Borne Vibration Concepts 6-1

CHAPTER 6 - GROUND-BORNE VIBRATION CONCEPTS

Noise and vibration are traditionally linked in environmental impact assessments because the two 

disciplines are perceived to have many physical characteristics in common. For example, noise can be 

generated by vibration of surfaces. Both involve fluctuating motion: noise is oscillating motion of air and 

vibration is oscillating motion of structures or the ground. Both are analyzed as wave phenomena: noise 

is made up of sound waves in air and vibration travels as waves in the ground. Both can be measured in 

decibels. Both are considered sensory effects: noise is related to hearing and vibration is related to 

feeling. Despite their similarities, however, noise and vibration require entirely different kinds of 

analyses. The fact that ground-borne vibration travels through a succession of solid media, such as 

various kinds of soil, rock, building foundation, and building structure, to reach the receiver makes 

vibration more complicated to measure and to predict than noise.

This chapter provides a general background on ground-borne vibration and summarizes the available data 

on ground-borne vibration caused by high-speed trains. The material presented is based largely on 

empirical data, since ground-borne vibration is a more complex phenomenon than that of airborne noise. 

The information contained in this chapter forms the basis of the assessment procedures presented in 

Chapters 7, 8, and 9.

The effects of ground-borne vibration include perceptible movement of the building floors, rattling of 

windows, shaking of items on shelves or hanging on walls, and rumbling sounds. In extreme cases, such 

vibration can damage buildings and other structures. Building damage is not a factor for most surface 

transportation projects, except during construction when there may be occasional blasting and pile 

driving. Annoyance from vibration often occurs when the vibration exceeds the threshold of perception 

by 5 to 10 decibels. This vibration level is an order of magnitude below the damage threshold for normal 

buildings.

The basic concepts of ground-borne vibration are illustrated for a high-speed train system in Figure 6-1. 

The train wheels rolling on the rails create vibration energy transmitted through the track support system 

into the trackbed or track structure. The amount of energy that is transmitted into the track structure 

depends strongly on factors such as how smooth the wheels and rails are and the resonance frequencies of 

the vehicle suspension system and the track support system. 
6-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Although a maglev train has no direct contact with its guideway, dynamic loads on the guideway structure 

during its motion do create vibration energy in the structure. This energy is transmitted through the 

guideway supports to the ground.

Figure 6-1 Propagation of Ground-Borne Vibrations into Buildings

The vibration of the track or guideway structure excites the adjacent ground, creating vibration waves that 

propagate through the various soil and rock strata to the foundations of nearby buildings. The vibration 

propagates from the foundation throughout the remainder of the building structure. The maximum 

vibration amplitudes of floors and walls of a building often occur at the resonance frequencies of those 

building elements. 

The vibration of floors and walls may cause perceptible vibration, rattling of items such as windows or 

dishes on shelves, or a rumble noise. The rumble is the noise radiated from the motion of the room 

surfaces. In essence, the room surfaces act like a giant loudspeaker. This is called ground-borne noise.

Ground-borne vibration is almost never annoying to people who are outdoors. Although the motion of 

the ground may be perceived, the motion does not provoke the same adverse human reaction without the 

effects associated with the shaking of a building. In addition, the rumble noise that usually accompanies 

the building vibration can only occur inside buildings.
Chapter 6: Ground-Borne Vibration Concepts 6-3

6.1 DESCRIPTORS OF GROUND-BORNE VIBRATION AND NOISE

6.1.1 Vibratory Motion

Vibration is an oscillatory motion, which can be described in terms of displacement, velocity, or 

acceleration. Because the motion is oscillatory, there is no net movement of the vibration element, and 

the average of any of the motion descriptors is zero. Displacement is the easiest descriptor to understand. 

For a vibrating floor, the displacement is simply the distance that a point on the floor moves away from 

its static position. The velocity represents the instantaneous speed of the floor movement, and 

acceleration is the rate of change of the speed.

Although displacement is easier to understand than velocity or acceleration, it is rarely used to describe 

ground-borne vibration. This is because most transducers used for measuring ground-borne vibration use 

either velocity or acceleration, and, even more 

important, the response of humans, buildings, and 

equipment to vibration is more accurately described 

using velocity or acceleration. 

6.1.2 Amplitude Descriptors

Vibration consists of rapidly fluctuating motions with 

an average motion of zero. The various methods 

used to quantify vibration amplitude are shown in 

Figure 6-2. The raw signal is the lighter weight curve 

in the top graph. This is the instantaneous vibration 

velocity, which fluctuates about the zero point. The 

peak particle velocity (PPV) is defined as the 

maximum instantaneous positive or negative peak of 

the vibration signal. PPV often is used in monitoring 

of blasting vibration since it is related to the stresses 

that are experienced by buildings.

Although PPV is appropriate for evaluating the 

potential of building damage, it is not suitable for 

evaluating human response. It takes some time for 

the human body to respond to vibration signals. In a 

sense, the human body responds to an average 

vibration amplitude. Because the net average of a 

vibration signal is zero, the root mean square (RMS) 

amplitude is used to describe the "smoothed" 

vibration amplitude. The RMS of a signal is the 

Figure 6-2 Different Methods of Describing a 

Vibration Signal
6-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

average of the squared amplitude of the signal. The average is typically calculated over a 1-second 

period. The RMS amplitude is shown superimposed on the vibration signal in Figure 6-2. The RMS

amplitude is always less than the PPV and is always positive.34

The PPV and RMS velocities are normally described in inches per second in the U.S. and in meters per 

second in the rest of the world. Although it is not universally accepted, decibel notation is in common use 

for vibration. Decibel notation serves to compress the range of numbers required to describe vibration. 

The bottom graph in Figure 6-2 shows the RMS curve of the top graph expressed in decibels. Vibration 

velocity level in decibels is defined as: 

















= ×

ref

v

v

v

L 10 20 log

where "Lv" is the velocity level in decibels, "v" is the RMS velocity amplitude, and "vref" is the reference 

velocity amplitude. A reference always must be specified whenever a quantity is expressed in terms of 

decibels. The accepted reference quantities for vibration velocity are 1x10-6 in./sec in the U.S. and either 

1x10-8 m/sec or 5x10-8 m/sec in the rest of the world. Because of the variations in the reference 

quantities, it is important to state clearly the reference quantity being used whenever velocity levels are 

specified. All vibration levels in this manual are referenced to 1x10-6 in./sec. Although not a universally 

accepted notation, the abbreviation "VdB" is used in this document for vibration decibels to reduce the 

potential for confusion with sound decibels.

6.1.3 Ground-Borne Noise

As discussed above, the rumbling sound caused by the vibration of room surfaces is called ground-borne 

noise. The annoyance potential of ground-borne noise is usually characterized using the A-weighted 

sound level. Although the A-weighted level is almost the only descriptor for community noise, there are 

potential problems when characterizing low-frequency noise using A-weighting. This is because of the 

non-linearity of human hearing, which causes sounds dominated by low-frequency components to seem 

louder than broadband sounds that have the same A-weighted level. The result is that a ground-borne 

noise level of 40 dBA sounds louder than 40 dBA broadband airborne noise. This anomaly is accounted 

for by setting the limits for ground-borne noise lower than would be the case for broadband noise.

 

34The ratio of PPV to maximum RMS amplitude is defined as the crest factor for the signal. The crest factor 

is always greater than 1.71, although a crest factor of 8 or more is not unusual for impulsive signals. For groundborne vibration from trains, the crest factor is usually 4 to 5.
Chapter 6: Ground-Borne Vibration Concepts 6-5

6.2 HUMAN PERCEPTION OF GROUND-BORNE VIBRATION AND NOISE

This section gives some general background on human response to different levels of building vibration, 

thereby establishing the basis for the criteria for ground-borne vibration and noise that are presented in 

Chapter 7.

6.2.1 Typical Levels of Ground-Borne Vibration and Noise

In contrast to airborne noise, ground-borne vibration is not a phenomenon that most people experience 

every day. The background vibration velocity level in residential areas is usually 50 VdB or lower, well 

below the threshold of perception for humans, which is around 65 VdB. Most perceptible indoor 

vibration is caused by sources within buildings such as operation of mechanical equipment, movement of 

people, or slamming of doors. Typical outdoor sources of perceptible ground-borne vibration are 

construction equipment, steel-wheeled trains, and traffic on rough roads. If the roadway is smooth, the 

vibration from traffic is rarely perceptible.

Common vibration sources and the human and structural response to ground-borne vibration are 

illustrated in Figure 6-3. The range of interest is from approximately 50 VdB to 100 VdB. Background 

vibration is usually well below the threshold of human perception and is of concern only when the 

vibration affects very sensitive manufacturing or research equipment, such as electron microscopes and 

high resolution photo lithography equipment.

The relationship between ground-borne vibration and ground-borne noise depends on the frequency 

content of the vibration and the acoustical absorption of the receiving room. The more acoustical 

absorption in a room, the lower the noise level will be. For a room with average acoustical absorption, 

the sound pressure level is approximately equal to the average vibration velocity level of the room 

surfaces.35 Hence, the A-weighted level of ground-borne noise can be estimated by applying A-weighting 

to the vibration velocity spectrum. Since the A-weighting at 31.5 Hz is -39.4 dB, if the vibration 

spectrum peaks at 30 Hz, the A-weighted sound level will be approximately 40 decibels lower than the 

velocity level. Correspondingly, if the vibration spectrum peaks at 60 Hz, the A-weighted sound level 

will be about 25 decibels lower than the velocity level.

 

35The sound level approximately equals the average vibration velocity level only when the velocity level is 

referenced to 1 micro inch/second. When velocity level is expressed using the international standard of 1x10-8

m/sec, the sound level is approximately 8 decibels lower than the average velocity level.
6-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment

6.2.2 Quantifying Human 

Response to Ground-Borne 

Vibration and Noise

One of the major problems in 

developing suitable criteria for 

ground-borne vibration is that there 

has been relatively little research 

into human response to vibration, 

in particular, human annoyance 

with building vibration. However, 

experience with U.S. rapid transit 

projects over the past 20 years 

represents a good foundation for 

developing suitable limits for 

residential exposure to groundborne vibration and noise from 

high-speed rail operations.

The relationship between the 

vibration velocity level measured 

in 22 homes and the general 

response of the occupants to 

vibration from rapid transit trains is 

illustrated in Figure 6-4. The data 

points shown were assembled from measurements that had been performed for several transit systems. 

The subjective ratings are based on the opinion of the person who took the measurements and the 

response of the occupants. These data were previously published in the "State-of-the-Art Review of 

Ground-borne Noise and Vibration."36 Both the occupants and the people who performed the 

measurements agreed that floor vibration in the "Distinctly Perceptible" category was unacceptable for a 

residence. The data in Figure 6-4 indicate that residential vibration exceeding 75 VdB is unacceptable if 

trains are passing every 5 to 15 minutes, as is usually the case with urban transit trains. Additional social 

survey data is provided by a Japanese study on vibration pollution conducted in 1975. 37 The percent of 

people annoyed by vibration from high-speed trains in Japan is shown by the “% annoyed” curve in 

Figure 6-4. Note that the scale corresponding to the percent annoyed is on the right hand axis of the 

graph. The results of the Japanese study confirm the conclusion that at vibration velocity levels ranging 

from 75 to 80 VdB, many people will find the vibration annoying.

 

36J.T. Nelson, H.J. Saurenman, “State-of-the-Art Review: Prediction and Control of Ground-Borne Noise 

and Vibration from Rail Transit Trains,” U.S. Department of Transportation, Urban Mass Transportation 

Administration, Report Number UMTA-MA-06-0049-83-4, DOT-TSC-UMTA-83-3, December 1983.

37Y. Tokita, “Vibration Pollution Problems in Japan,” In Inter-Noise 75, Sendai, Japan, pp. 465-472, 1975.

Figure 6-3 Typical Levels of Ground-Borne Vibration
Chapter 6: Ground-Borne Vibration Concepts 6-7

6.3 FACTORS THAT INFLUENCE GROUND-BORNE VIBRATION AND NOISE

Developing accurate estimates of ground-borne vibration is complicated by the many factors that can 

influence vibration levels at the receiver position. Factors that have significant effects on the levels of 

ground-borne vibration are discussed in this section. Some of these factors that are known to have, or are 

suspected of having, a significant influence on the levels of ground-borne vibration and noise are 

summarized in Table 6-2. As the table indicates, the physical parameters of the track, trainsets, geology, 

and receiving building all influence vibration levels. The important physical parameters can be divided 

into the following four categories:

Operational and Vehicle Factors: This category includes all of the parameters that relate to train 

vehicles and the operation of trains. Factors such as high speed, stiff primary suspensions on the 

vehicle, and flat or worn wheels will increase the possibility of ground-borne vibration problems.

Guideway: The type and condition of the rails, the type of guideway, the rail support system, and the 

mass and stiffness of the guideway structure can all influence the level of ground-borne vibration. 

Worn rail and wheel impacts at special trackwork can substantially increase ground-borne 

vibration. A high-speed train system guideway will be either in tunnel, open trench, at-grade, or 

aerial viaduct. It is rare for ground-borne vibration to be a problem with aerial structures, except 

when guideway supports are located within 50 feet of buildings. Directly radiated airborne noise is 

usually the dominant problem from guideways at-grade or in cut, although vibration can sometimes 

be a problem. For tunnels that are under residential areas, however, ground-borne noise and 

vibration are often among the most significant environmental problems.

Geology: Soil conditions are known to have a strong influence on the levels of ground-borne vibration. 

Among the most important factors are the stiffness and internal damping of the soil and the depth 

to bedrock. Experience has shown that vibration propagation is more efficient in clay soils as well 

as areas with shallow bedrock; the latter condition seems to channel or concentrate the vibration 

energy close to the surface, resulting in ground-borne vibration problems at large distances from 

the track. Factors such as layering of the soil and depth to water table can also have significant 

effects on the propagation of ground-borne vibration.

Receiving Building: Ground-borne vibration problems occur almost exclusively inside buildings. 

Therefore, the characteristics of the receiving building are a key component in the evaluation of 

ground-borne vibration. The train vibration may be perceptible to people who are outdoors, but it 

is very rare for outdoor vibration to cause complaints. The vibration levels inside a building 

depend on the vibration energy that reaches the building foundation, the coupling of the building 

foundation to the soil, and the propagation of the vibration through the building structure. The 

general guideline is that the more massive a building is, the lower its response to incident vibration 

energy in the ground.
6-8 High-Speed Ground Transportation Noise and Vibration Impact Assessment

The human response to 

different levels of groundborne noise and vibration 

is described in Table 6-1. 

The first column lists 

vibration velocity levels, 

and the next two columns 

list the corresponding 

noise levels assuming that 

the vibration spectrum 

peaks at either 30 Hz or 60 

Hz. As discussed above,

the A-weighted noise level 

will be approximately 40 

dB less than the vibration 

velocity level if the 

spectrum peak is around 

30 Hz, and 25 dB lower if 

the spectrum peak is around 60 Hz. However, human response measures illustrate that achieving either 

the acceptable vibration or acceptable noise levels does not guarantee that the other will be acceptable. 

For example, the noise caused by vibrating structural components may be very annoying even though the 

vibration cannot be felt.

Table 6-1 Human Response to Different Levels of Ground-Borne Noise and Vibration

RMS Vibration Noise Level

Velocity Level Low Freq1 Mid Freq2

Human Response

65 VdB 25 dBA 40 dBA

Approximate threshold of perception for many humans. Lowfrequency sound usually in audible, mid-frequency sound excessive 

for quiet sleeping areas.

75 VdB 35 dBA 50 dBA

Approximate dividing line between barely perceptible and distinctly 

perceptible. Many people find train vibration at this level 

unacceptable. Low-frequency noise acceptable for sleeping areas, 

mid-frequency noise annoying in most quiet occupied areas.

85 VdB 45 dBA 60 dBA

Vibration acceptable only if there are an infrequent number of 

events per day. Low-frequency noise unacceptable for sleeping 

areas, mid-frequency noise unacceptable even for infrequent events 

with institutional land uses such as schools and churches.

Notes:

1. Approximate noise level when vibration spectrum peak is near 30 Hz.

2. Approximate noise level when vibration spectrum peak is near 60 Hz.

Figure 6-4 Occupant Response to Urban Transit-Induced

Residential VibrationError! Unknown switch argument.
Chapter 6: Ground-Borne Vibration Concepts 6-9

Table 6-2 Factors that Influence Levels of Ground-Borne Vibration and Noise

Factors Related to Vibration Source

Factors Influence

Vehicle 

Suspension

If the suspension is stiff in the vertical direction, the effective vibration forces will be higher. 

On transit cars, only the primary suspension affects the vibration levels, the secondary 

suspension that supports the car body has no apparent effect. Similar effects are likely to occur 

with high-speed trainsets.

Wheel Condition Wheel roughness and flat spots are the major cause of vibration from steel-wheel/steel-rail train 

systems. 

Track Surface Rough track is often the cause of vibration problems. Maintaining a smooth track surface will 

reduce vibration levels.

Track Support 

System

On rail systems, the track support system is one of the major components in determining the 

levels of ground-borne vibration. The highest vibration levels are created by track that is rigidly 

attached to a concrete trackbed. The vibration levels are much lower when special vibration 

control track systems such as resilient fasteners, ballast mats, and floating slabs are used.

Speed As intuitively expected, higher speeds result in higher vibration levels. Doubling speed usually 

results in vibration levels 4 to 6 decibels higher.

Track Structure

The general rule -of-thumb is that the heavier the track structure, the lower the vibration levels. 

The vibration levels from a lightweight bored tunnel will usually be higher than from a poured 

concrete box tunnel.

Depth of 

Vibration Source

There are significant differences in the vibration characteristics when the source is underground 

compared to at the ground surface. 

Factors Related to Vibration Path

Factor Influence

Soil Type It is generally expected that vibration levels will be higher in stiff clay type soils than in loose 

sandy soils.

Rock Layers

Vibration levels often seem to be high near at-grade track when the depth to bedrock is 30 feet 

or less. Tunnels founded in rock will result in lower vibration amplitudes close to the tunnel. 

Because of efficient propagation, the vibration level does not attenuate as rapidly in rock as it 

does in soil.

Soil Layering Soil layering will have a substantial, but unpredictable, effect on the vibration levels since each 

stratum can have significantly different dynamic characteristics.

Depth to Water 

Table

The presence of the water table is often expected to have a significant effect on ground-borne 

vibration, but evidence to date cannot be expressed with a definite relationship.

Frost Depth There is some indication that vibration propagation is less efficient when the ground is frozen.

Factors Related to Vibration Receiver

Factor Influence

Foundation Type The general rule -of-thumb is that the heavier the building foundation, the greater the coupling 

loss as the vibration propagates from the ground into the building.

Building 

Construction

Since ground-borne vibration and noise almost always are evaluated in terms of indoor 

receivers, the propagation of the vibration through the building must be considered. Each 

building has different characteristics relative to structure-borne vibration, although the general 

rule-of-thumb is that the more massive a building is, the lower the levels of ground-borne 

vibration will be.

Acoustical 

Absorption

The amount of acoustical absorption in the receiver room affects the levels of ground-borne 

noise.
6-10 High-Speed Ground Transportation Noise and Vibration Impact Assessment

6.4 GROUND-BORNE VIBRATION FROM HIGH-SPEED TRAINS

Available data on ground-borne vibration from high-speed trains are from measurements of test programs 

involving the Acela in the United States and the TransRapid TR08 in Germany, and revenue service 

operations of the X2000 in Sweden, the Pendolino in Italy, and the TGV and Eurostar trains in France. 

Acela and TR08 tests were performed in 2000-2001. The European revenue service data were obtained in 

May 1995 as part of the data collection task involved in preparing this manual. Vibration measurements 

were made at two sites in each country, with vibration propagation testing done at one primary site in 

each country. This measurement program represents one of the first times that the same detailed groundborne vibration testing procedure has been carried out in several different countries for high-speed trains 

operating under normal revenue conditions. 

One of the major problems in characterizing ground-borne vibration from trains is that geology has a 

major influence in vibration levels, and there are no analytical methods of factoring out the effects of 

geology. This makes it very difficult to compare the levels of ground-borne vibration from different types 

of trains, unless they are operating on the same track. An experimental method of characterizing 

vibration propagation characteristics at a specific site that was developed to work around this problem38

was applied during the tests in Sweden, Italy, and France.

This propagation test procedure basically consists of dropping a weight on the ground and measuring the 

force of the impact and the vibration pulses at various distances from the impact point. The transfer 

functions between the vibration pulses and the force impulse are then used to characterize vibration 

propagation. Assuming a reasonably linear system, these transfer functions define the relationship 

between any type of exciting force and the resulting ground vibration.

The end result of the propagation test is a measure of the transmissibility of ground vibration, or line 

source transfer mobility, as a function of distance from the train. Measurements of train vibration and 

line source transfer mobility at the same site can be used to derive a "force density" function that 

characterizes the vibration forces of a train independent of the geologic conditions at the site. The test is 

discussed in greater detail in Chapter 9.

The steps used to analyze the train vibration and ground transfer mobility data to derive force densities 

were as follows:

1. Transfer mobility and train vibration were expressed in terms of frequency-dependent representations, 

or frequency spectra.

2. Raw transfer mobility data for point sources were combined to approximate line source transfer 

mobility at each test site. 

 

38U.S. Department of Transportation, Federal Transit Administration, Transit Noise and Vibration Impact 

Assessment, “Chapter 11: Detailed Vibration Analysis,” Report DOT-T-95-16, April 1995.
Chapter 6: Ground-Borne Vibration Concepts 6-11

3. Best-fit curves of level vs. distance for each frequency band were obtained using linear regression or 

other curve-fitting technique, approximate line-source transfer mobility, and train vibration spectra 

as a function of distance from the source.

4. The difference between the train vibration spectrum and the transfer mobility spectrum at the same 

distance, or the force density spectrum, was calculated. Theoretically the force density should be 

independent of distance. In practice, however, force density is calculated at each measurement 

distance, and the average force density is used to characterize each type of trainset. For all of the 

trainsets, the force densities at the six measurement distances converged to within 3 to 4 decibels of 

the average.
6-12 High-Speed Ground Transportation Noise and Vibration Impact Assessment
Chapter 7 Vibration Impact Criteria 7-1

CHAPTER 7 - VIBRATION IMPACT CRITERIA

The environmental impacts of vibration from high-speed trains are similar to those from other types of 

trains. The resulting building vibration can be perceptible and intrusive to building occupants and can 

cause secondary rattling of windows, items on shelves, and pictures hanging on walls. In addition, the 

sound reradiated from vibrating room surfaces, referred to as ground-borne noise, often will be audible in 

the form of a low-frequency rumbling sound.

Because of the relatively rare occurrence of annoyance due to ground-borne vibration and noise, there has 

been only limited sponsored research of human response to building vibration and structure-borne noise. 

However, with the construction of new rail rapid transit systems in the past 20 years, considerable 

knowledge has been gained as to how communities will react to various levels of building vibration. This 

experience, combined with the available national and international standards,39,40 represents a good 

foundation for predicting annoyance from ground-borne noise and vibration in residential areas that 

would be caused by a high-speed rail project. The criteria for ground-borne vibration and noise included 

in this chapter are based on the FTA manual Transit Noise and Vibration Impact Assessment41 with only 

minor modifications.

The criteria for environmental impact from ground-borne vibration and noise presented in Table 7-1 are 

based on the maximum levels for a single event. The criteria account for variation in land use as well as 

the frequency of events, which can differ widely among high-speed train projects. Most experience is 

with the community response to ground-borne vibration from rail rapid transit systems with typical 

 

39Acoustical Society of America, “American National Standard: Guide to Evaluation of Human Exposure 

to Vibration in Buildings,” ANSI S3.29-1983 (ASA 48-1983).

40International Standards Organization, “Evaluation of Human Exposure to Whole-Body Vibration, Part 2: 

Continuous and Shock-Induced Vibrations in Buildings (1-80Hz),” ISO-2361-2, 1989.

41U.S. Department of Transportation, Federal Transit Administration, Transit Noise and Vibration Impact 

Assessment, Report Number DOT-T-95-16, April 1995.
7-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

headways in the range of 3 to 10 minutes and each vibration event lasting less than 10 seconds. Intuition 

suggests that with many fewer events each day, as is typical for high-speed train projects, it should take 

higher vibration levels to evoke the same community response. Consequently, the criteria distinguish 

between projects with frequent and infrequent events, where Frequent Events are defined as more than 70 

events per day. The dividing line between frequent and infrequent events was originally selected in the 

FTA manual such that most commuter rail projects fall into the infrequent event category. Intercity rail 

operations are assumed to fall into the infrequent category.

Table 7-1 Ground-Borne Vibration and Noise Impact Criteria

Ground-Borne Vibration Impact 

Levels

(VdB re 1 micro inch/sec)

Ground-Borne Noise Impact 

Levels

(dB re 20 micro Pascals)

Land Use Category

Frequent1

Events

Infrequent2

Events

Frequent1

Events

Infrequent2

Events

Category 1: Buildings where 

vibration would interfere with 

interior operations.

65 VdB365 VdB3 N/A4 N/A4

Categor y 2: Residences and 

buildings where people normally 

sleep.

72 VdB 80 VdB 35 dBA 43 dBA

Category 3: Institutional land uses 

with primarily daytime use.

75 VdB 83 VdB 40 dBA 48 dBA

Notes:

1. Frequent Events is defined as more than 70 vibration events per day.

2. Infrequent Events is defined as fewer than 70 vibration events per day.

3. This criterion limit is based on levels that are acceptable for most moderately sensitive equipment such as 

optical microscopes. Vibration-sensitive manufacturing or research will require detailed evaluation to define 

the acceptable vibration levels. Ensuring lower vibration levels in a building often requires special design of the 

HVAC systems and stiffened floors.

4. Vibration-sensitive equipment is not sensitive to ground-borne noise.

The criteria are based primarily on experience with passenger train operations, rather than freight train 

operations. The difference is that passenger train operations, whether rapid transit, commuter rail, 

normal, or high-speed intercity, create vibration events that last less than about 10 seconds. A typical 

line-haul freight train is about 5,000 feet long. At a speed of 30 mph, it takes a 5,000-foot freight train 

approximately two minutes to pass. Even though the criteria are primarily based on experience with 

shorter vibration events and this manual is oriented towards high-speed train projects, in some situations 

potential impacts from freight train ground-borne vibration may need to be evaluated. The prime example 

is the operation of high-speed trains within an existing freight railroad right-of-way. Some guidelines for 

applying these criteria to rail corridors with existing freight or passenger trains are given later in this 

chapter.

The criteria for acceptable ground-borne vibration are expressed in terms of RMS velocity levels in 

decibels. The criteria for acceptable ground-borne noise are expressed in terms of A-weighted sound 

level. The limits are specified for the three land-use categories defined below:
Chapter 7 Vibration Impact Criteria 7-3

Vibration Category 1: High Sensitivity – Category 1 includes buildings where it is essential that 

ambient vibrations be kept very low for the operations within the building. Vibration levels in this 

category may be well below levels associated with human annoyance. (Concert halls and other 

special use facilities are covered separately in Table 7-2.) Typical land uses covered by Category 1 

are vibration-sensitive research and manufacturing facilities, hospitals with vibration-sensitive 

equipment, and university research operations. The degree of sensitivity to vibration will depend 

on the specific equipment that will be affected by the vibration. Equipment such as electron 

microscopes and high-resolution photolithography equipment can be very sensitive to vibration, 

and even normal optical microscopes will sometimes be difficult to use when vibration is well 

below the human annoyance level. Semiconductor manufacturing is an example of a vibrationsensitive process.

The vibration limits for Vibration Category 1 are based on acceptable vibration for moderately 

vibration-sensitive equipment, such as optical microscopes and electron microscopes with vibration 

isolation systems. Defining limits for equipment that is even more sensitive requires a detailed 

review of the specific equipment involved. This type of review is usually performed during the 

final design phase and not as part of the environmental impact assessment. Mitigation of train 

vibration that affects sensitive equipment typically involves modification of the equipment 

mounting system or relocation of the equipment rather than applying vibration control measures to 

the high-speed rail project. 

This category does not include most computer installations or telephone switching equipment. 

Although the owners of this type of equipment often are very concerned about the potential of 

ground-borne vibration interrupting smooth operation of their equipment, computers and other 

electronic equipment are rarely sensitive to vibration. Most such equipment is designed to operate 

in typical building environments where it may experience occasional shock from bumping and 

continuous background vibration caused by other equipment.

Vibration Category 2: Residential – This category covers all residential land uses and any buildings 

where people sleep, such as hotels and hospitals. No differentiation is made between different 

types of residential areas. This equal consideration is given primarily because ground-borne 

vibration and noise are experienced indoors, and building occupants have practically no means to 

reduce their exposure. Even in a noisy urban area, bedrooms often will be quiet in buildings that 

have effective noise insulation and tightly closed windows. Hence, an occupant of a bedroom in a 

noisy urban area is likely to be just as sensitive to ground-borne noise and vibration as someone in 

a quiet suburban area.

Vibration Category 3: Institutional – Vibration Category 3 includes schools, churches, other 

institutions, and quiet offices that do not have vibration-sensitive equipment, but still have the 

potential for activity interference. Although it is generally appropriate to include office buildings 

in this category, it is not appropriate to include all buildings that have any office space. For 

example, most industrial buildings have office space, but buildings primarily for industrial use are 

not intended to be included in this category.
7-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Some buildings, such as concert halls, television and recording studios, and theaters, can be very sensitive 

to vibration and noise but do not fit into any of the three categories. Because of the sensitivity of these 

buildings, they usually warrant special attention during the environmental assessment of a high-speed rail 

project. Criteria for acceptable levels of ground-borne vibration and noise for various types of special 

buildings are given in Table 7-2. 

The criteria related to ground-borne vibration causing human annoyance or interfering with use of 

vibration-sensitive equipment are listed in Tables 7-1 and 7-2. It is extremely rare for vibration from train 

operations to cause any sort of building damage, even minor cosmetic damage. However, there is 

sometimes concern about damage to fragile historic buildings located near the right-of-way. Even in 

these cases, damage is unlikely except when the track will be very close to the structure. Damage 

thresholds that apply to these structures are discussed in Chapter 10.

In most cases, except near railroad tracks, the existing environment does not include a significant number 

of perceptible ground-borne vibration or noise events. However, it is common for high-speed train 

projects to use parts of existing rail corridors. The criteria given in Tables 7-1 and 7-2 do not indicate 

how to account for existing vibration, a common situation for high-speed rail projects using existing rail 

right-of-ways. Methods of handling representative scenarios include the following:

1. Infrequently used rail corridor: Use the vibration criteria from Tables 7-1 and 7-2 when the existing 

rail traffic consists of four or less trains per day.

2. Moderately used rail corridor: If the existing traffic consists of 5 to 12 trains per day with vibration 

that substantially exceeds the impact criteria, there is no impact as long as the project vibration levels 

estimated using the procedures outlined in either Chapter 8 or 9 are at least 5 VdB less than the 

existing vibration. Vibration from existing trains could be estimated using the General Assessment 

procedures in Chapter 8; however, it is usually preferable to measure vibration from existing train 

traffic.

3. Heavily used rail corridor: If the existing traffic exceeds 12 trains per day and if the project will not 

Table 7-2 Ground-Borne Vibration and Noise Impact Criteria for Special Buildings

Ground-Borne Vibration Impact Levels

(VdB re 1 micro-inch/sec)

Ground-Borne Noise Impact Levels

(dB re 20 micro-Pascals)

Type of Building or Room

Frequent1

Events

Infrequent2

Events

Frequent1

Events

Infrequent2

Events

Concert Halls

TV Studios

Recording Studios

Auditoriums

Theaters

65 VdB

65 VdB

65 VdB

72 VdB

72 VdB

65 VdB

65 VdB

65 VdB

80 VdB

80 VdB

25 dBA

25 dBA

25 dBA

30 dBA

35 dBA

25 dBA

25 dBA

25 dBA

38 dBA

43 dBA

Notes:

1. Frequent Events is defined as more than 70 vibration events per day. 

2. Infrequent Events is defined as fewer than 70 vibration events per day. 
Chapter 7 Vibration Impact Criteria 7-5

significantly increase the number of vibration events (less than doubling the number of trains is 

usually considered not significant), there will not be additional impact unless the project vibration, 

estimated using the procedures of Chapters 8 or 9, will be higher than the existing vibration. In 

locations where the new trains will be operating at much higher speeds than the existing rail traffic, it 

is likely that the high-speed trains will generate substantially higher levels of ground-borne vibration. 

When the project will cause vibration more than 5 VdB greater than the existing source, the existing 

source can be ignored and the vibration criteria in Tables 7-1 and 7-2 applied to the project.

4. Moving existing tracks: Another scenario where existing vibration can be significant is a new highspeed rail line within an existing rail right-of-way that will require shifting the location of existing 

tracks. Where the track relocation will cause higher vibration levels at sensitive receptors, then the 

projected vibration levels from both rail systems must be compared to the appropriate impact criterion 

to determine if there will be new impact. If impact is judged to have existed prior to moving the 

tracks, new impact will be assessed only if the relocation results in more than 3 VdB increase in 

vibration level. Although the impact thresholds given in Tables 7-1 and 7-2 are based on experience 

with vibration from rail transit systems, they can be applied to freight train vibrations as well. 

However, locomotive and rail car vibration should be considered separately. Because the locomotive 

vibration only lasts for a few seconds, the infrequent event limit is appropriate, but for a typical linehaul freight train where the rail car vibration lasts for several minutes, the frequent-event limits 

should be applied to the rail car vibration. Some judgment must be exercised to make sure that the 

approach is reasonable. For example, some spur rail lines carry very little rail traffic (sometimes only 

one train per week) or have short trains, in which case the infrequent limits are appropriate. 
7-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment
Chapter 8: Preliminary Vibration Assessment 8-1

CHAPTER 8 - PRELIMINARY VIBRATION ASSESSMENT

Procedures that can be used to develop generalized predictions of ground-borne vibration and noise are 

described in this chapter. There are three different levels of detail for projecting ground-borne vibration:

Screening – The screening procedure uses a table of distances to dete rmine whether noise-sensitive land 

uses are close enough to the proposed high-speed train system for impact from ground-borne 

vibration to be possible. More detailed analysis is required if any sensitive land uses are within the 

screening distances. The screening procedure does not require any specific knowledge about the 

vibration characteristics of the system or the geology of the area.

General Assessment – The general level of assessment uses generalized data to develop a curve of 

vibration level as a function of distance from the track. The vibration levels at specific buildings 

are estimated by reading values from the curve and applying adjustments to account for factors 

such as track support system, train speed, track and wheel condition, type of building, and receiver 

location within the building. The general level deals only with the overall vibration velocity level 

and the A-weighted sound level. It does not consider the frequency spectrum of the vibration or 

noise.

Detailed Analysis – The detailed analysis involves applying all of the available tools for accurately 

projecting the vibration impact at specific sites. The procedure outlined in this manual includes a 

test of the trainset (or similar trainset) to define the forces generated by the vibration source and 

tests at the sites in question to define how the local geology affects vibration propagation. 

Developing detailed projections of ground-borne vibration is considerably more complex than 

developing detailed projections of airborne noise. The vibration projection procedure is not only 

complex, but also has not yet been standardized. Accurate projections of ground-borne vibration 

require professionals with experience in performing and interpreting vibration propagation tests. 

As such, detailed vibration predictions are usually performed during the final design phase of a 

project when there is sufficient reason to suspect adverse vibration impact from the project. 

The Screening and General Assessment methods are discussed in this chapter. The Detailed Analysis 

procedure, which is based on measurements to characterize vibration propagation at specific sites, is 

presented in Chapter 9.

General and detailed predictions do not always have a clear distinction. For example, it is often 
8-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

appropriate to use several representative measurements of vibration propagation along the planned 

alignment in developing generalized propagation curves. At other times, generalized prediction curves 

may be sufficient for most of an alignment, with detailed analysis applied to particularly sensitive 

buildings, such as a concert hall.

The purpose of the General Assessment is to provide a relatively simple method of developing estimates 

of the overall levels of ground-borne vibration and noise that can be compared to the acceptability criteria 

given in Chapter 7. For many projects, particularly when comparing alternatives, this level of detail will 

be sufficient for the environmental assessment. Where potential problems exist, the Detailed Analysis is 

then undertaken during final design of the selected alternative to define accurately the level of impact and 

design mitigation measures. A Detailed Analysis usually will be required when designing special tracksupport systems, such as floating slabs or ballast mats. Detailed Analysis is not usually required if the 

mitigation measure consists of relocating a crossover or turnout. 

8.1 VIBRATION SCREENING PROCEDURE

The screening method is intended to be applied early in a project development before many details on the 

system have been defined. It allows a quick check to identify whether and where impacts from groundborne vibration are likely. Screening distances for three different speed ranges and two general types of 

land use are given in Table 8-1. 

Table 8-1 Screening Distances for Vibration Assessments

(applicable to steel-wheel/steel-rail high-speed train systems)

Screening Distance, ft

Train Speed

Land Use Train 

Frequency*

Less than

 100 mph

100 to 

200 mph

200 to 

300 mph

Frequent 120 220 275

Residential

Infrequent 60 100 140

Frequent 100 160 220

Institutional

Infrequent 20 70 100

*Frequent = greater than 70 passbys per day.

 Infrequent = less than 70 passbys per day.

The screening distances given in Table 8-1 are based on the criteria presented in Chapter 7 and the 

Generalized Assessment procedures discussed in Section 8.2, assuming "normal" vibration propagation 

conditions. "Efficient" vibration propagation conditions, characterized by the transmission of ground 

vibration at low rates of attenuation with distance, can result in substantially higher vibration levels. 

Efficient propagation has not been assumed in developing the screening distances, since it is a relatively 

unusual condition and assuming efficient propagation would overestimate the potential for vibration 

impact. However, by not accounting for the possibility of efficient vibration propagation, some potential 

impact areas may not be identified in the screening process. When there is evidence of efficient 

propagation, such as previous complaints about existing rail facilities or a history of problems with 

construction vibration, the distances in Table 8-1 should be increased by a factor of 2.
Chapter 8: Preliminary Vibration Assessment 8-3

8.2 GENERALIZED VIBRATION ASSESSMENT PROCEDURE

The basic approach of the General Assessment procedure is to use a base curve of overall ground-surface 

vibration as a function of distance from the source, then to apply adjustments to this curve to account for 

factors such as track support system, train speed, track and wheel condition, building type, and receiver 

location within the building. Steel-wheel/steel-rail technology has, in terms of ground-borne vibration, 

similar characteristics to existing intercity passenger train and transit trains. Maglev technology has some 

unique characteristics based on measurements at the test facility in Germany.

8.2.1 Base Curve

The generalized projection curves for high-speed trains are shown in Figure 8-1. These curves represent 

typical ground-surface vibration levels assuming equipment in good condition and speeds of 150 mph. 

The levels must be adjusted to account for factors such as different speeds, equipment, and geologic 

conditions than those assumed in the figure. The curves in Figure 8-1 are based on the ground-borne 

vibration measurement data discussed in Appendix D.

The steel-wheel curve in Figure 8-1 is applicable to high-speed trains both at-grade and in tunnel. The 

rationale for applying the same curve to these two very different conditions is based on the analysis done 

for the FTA manual Transit Noise and Vibration Impact Assessment.

42 In developing generalized 

prediction curves for the FTA manual, investigators found that transit trains operating at grade and in 

tunnel had similar overall vibration levels. This finding was rather surprising because transit trains 

operating in tunnels tend to generate more vibration complaints than those operating on at-grade track. 

This tendency is probably due to two factors: (1) tunnels are usually located close to buildings, often 

directly under them, in densely developed areas, and (2) for at-grade systems, airborne noise from train 

passbys is usually more noticeable than the ground-borne vibration generated. Although the overall 

vibration levels from trains operating in tunnel and above grade are similar, there are differences in the 

frequency spectra of the vibration. The ground-borne vibration from trains in tunnels tends to be higher 

frequency than the vibration from at-grade track, and higher frequencies make the ground-borne noise 

from tunnels more noticeable in nearby buildings.

 

42U.S. Department of Transportation, Federal Transit Administration, Transit Noise and Vibration Impact 

Assessment, Report Number DOT-T-95-16, April, 1995.
8-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Figure 8-1 Generalized Ground-Borne Vibration Curve

The steel-wheel curve in Figure 8-1 is the same as the curve in the FTA manual (ref. 1) that is applicable 

to urban transit trains, except that this curve is 10 VdB higher to account for the speed adjustment from 50 

mph for urban transit to 150 mph for high-speed rail. This curve represents the high range of the 

available measurement data of high-speed train ground-borne vibration. Only data from locations known 

to have unusual vibration propagation conditions were consistently above the curve. 

Experience with ground-borne vibration data from trains has shown that a 5 to 10-decibel fluctuation in 

vibration levels under apparently similar conditions is not uncommon. The curves in Figure 8-1 represent 

the upper range of the measurement data. Although actual levels fluctuate widely, ground-borne vibration 

rarely will exceed the curves in Figure 8-1 by more than 1 or 2 decibels unless there are extenuating 

circumstances, such as rail corrugations or flat spots on wheels for the steel-wheel mode, or efficient 

vibration propagation for all technologies.

It is not recommended to show projections of normal fluctuation as a "range" of vibration levels. For 

example, the projected level from Figure 8-1 at a train speed of 150 mph is about 72 VdB, the threshold 

for acceptable ground-borne vibration for residential land uses, at a distance of 180 feet from the track 

centerline. If shown as a range to reflect normal fluctuations, the projected level of ground-borne 

vibration might be given as a range between 67 and to 72 VdB, and the interpretation of whether the 

projected vibration levels exceed the impact threshold becomes unclear. However, because actual levels 

of ground-borne vibration will sometimes differ substantially from the projections, some care must be 

taken when interpreting projections. Some guidelines are given below:
Chapter 8: Preliminary Vibration Assessment 8-5

1. Projected vibration is below the impact threshold. Vibration impact is unlikely in this case.

2. Projected ground-borne vibration is 0 to 5 decibels greater than the impact threshold. In this range 

there is still a significant chance (at least 50 percent) that actual ground-borne vibration levels will 

be below the impact threshold. In this case, the impact would be reported in the environmental 

document as exceeding the applicable threshold, and a commitment would be made to conduct 

more detailed studies to refine the vibration impact analysis and determine appropriate mitigation 

during final design. A site-specific Detailed Analysis may show that vibration control measures 

are not needed.

3. Projected ground-borne vibration is 5 decibels or more greater than the impact threshold. Vibration 

impact is probable and some type of vibration control should be incorporated into the final design 

of the project.

The two most important factors that must be accounted for in a General Assessment are the type of 

vibration source and the vibration propagation characteristics. It is well known that there are situations in 

which ground-borne vibration propagates much more efficiently than normal. The result is unacceptable 

vibration levels at distances two to three times the normal distance. Unfortunately, the geologic 

conditions that promote efficient propagation have not been well documented and are not fully 

understood. Shallow bedrock or clay soils often are involved. One possibility is that shallow bedrock 

acts to keep the vibration energy near the surface. Much of the energy that would normally radiate down 

is directed back towards the surface by the rock layer, with the result that the ground surface vibration is 

higher than normal.

8.2.2 Adjustment Factors

Once the vibration levels have been projected using the base curves in Figure 8-1, the adjustments listed 

in Table 8-2 can be used to develop vibration projections for specific receiver positions inside buildings. 

All of the adjustments are given as numbers to be added to, or subtracted from, the base level. The 

adjustment parameters are speed, wheel and rail type and condition, type of track or guideway support 

system, type of building foundation, and number of floors above the basement level. Many of these 

adjustments depend heavily on the frequency spectrum of the vibration source and the frequency 

dependence of the vibration propagation. The single numbers given are suitable for generalized 

evaluation of the vibration impact and vibration mitigation measures since they are based on typical 

vibration spectra. However, the general adjustments are not adequate for detailed evaluations of impact 

of sensitive buildings or for detailed specification of mitigation measures. Careful consideration of the 

shape of the actual vibration spectra will avoid selection of an inappropriate vibration control measure, 

which in some cases could actually cause an increase in the vibration levels.
8-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Table 8-2 Adjustment Factors for Generalized Predictions of Ground-Borne Vibration and Noise

Factors Affecting Vibration Source for Steel-Wheel Technology

Source Factor Adjustment to Propagation Curve Comment

Vehicle 

Speed

Adjustment

(Ref Speed = 150 mph)

300 mph +6.0 dB

200 mph 2.5 dB

150 mph 0.0 dB

100 mph -3.5 dB

Speed

75 mph -6.0 dB

Vibration level is approximately proportional to 

20*log(speed/speedref). Sometimes the variation 

with speed has been observed to be as low as 10 to 

15 log(speed/speedref).

Resilient Wheels 0 dB

Resilient wheels do not generally affect groundborne vibration except at frequencies greater than 

about 80 Hz.

Worn Wheels or Wheels 

with Flats +10 dB

Wheel flats or wheels that are unevenly worn can 

cause high vibration levels. This problem can be 

prevented with wheel truing and slip-slide detectors 

to prevent the wheels from sliding on the track.

Worn or Corrugated Track +10 dB

If both the wheels and the track are worn, only one 

adjustment should be used. Corrugated track is a 

common problem; however, it is difficult to predict 

the conditions that cause corrugations to occur. 

Rail grinding can remove rail corrugations.

Crossovers and Other 

Special Trackwork

Select

highest

one

that

applies

+10 dB

Wheel impacts at special trackwork with standard 

frogs will significantly increase vibration levels. 

The increase will be less at greater distances from 

the track. Moveable point frogs mitigate this 

problem.

Floating Slab Trackbed -15 dB

The reduction achieved with a floating slab 

trackbed is strongly dependent on the frequency 

characteristics of the vibration.

Ballast Mats -10 dB Actual reduction is strongly dependent on 

frequency of vibration.

High Resilience Fasteners -5 dB

Slab track with track fasteners that are very 

compliant in the vertical direction can reduce 

vibration at frequencies greater than 40 Hz.

Resiliently Supported Ties

Select

highest

one

that

applies

-10 dB

Resiliently supported tie systems in tunnel have 

been found to provide very effective control of lowfrequency vibration.

Relative to at-grade tie & ballast:

Aerial/Viaduct structure -10 dB

Open Cut 0 dB

Relative to bored tunnel in soil:

Station -5 dB

Cut and Cover -3 dB

Type of Track Structure

Rock-Based -15 dB

The general rule is the heavier the structure, the 

lower the vibration levels. Putting the track in cut 

may reduce the vibration levels slightly. Rockbased tunnels will shift vibration to a higher 

frequency.

Factors Affecting Vibration Source for Maglev Technology

Source Factor Adjustment to Propagation Curve Comment

Vehicle Speed Adjustment

(Ref. Speed=150 mph)

300 mph + 14 dB

200 mph + 4 dB

150 mph 0 dB

100 mph - 8 dB

Speed

75 mph - 10 dB

Speed relationship is highly dependent on 

structural response of guideway.
Chapter 8: Preliminary Vibration Assessment 8-7

Table 8 Continued...

Concrete Reference

Steel + 1 dB

Hybrid + 2 dB

At-Grade + 0 dB

Type of Guideway

Structure

Switch + 10 dB

Adjustments are based on limited data on 

prototype structure. Vibration levels depend on 

structural design.

Factors Affecting Vibration Path

Path Factor Adjustment to Propagation Curve Comment

Geologic Conditions that 

Promote Efficient 

Vibration 

Efficient propagation in soil

+10 dB 

Refer to the text for guidance on identifying 

areas where efficient propagation is possible. 

Propagation Propagation 

in rock layer

Dist.

50 ft

100 ft

150 ft

200 ft

Adjust.

+2 dB

+4 dB

+6 dB

+9 dB

The positive adjustment accounts for the lower 

attenuation of vibration in rock compared to 

soil. Because it is more difficult to get vibration 

energy into rock, propagation through rock 

usually results in lower vibration than 

propagation through soil.

Wood Frame -5 dB

1-2 Stone Masonry -7 dB

2-4 Story Masonry -10 dB

Large Masonry on Piles -10 dB

Large Masonry on 

Spread Footings -13 dB

Coupling to Building 

Foundation

Foundation in Rock 0 dB

The general rule is the heavier the building 

construction, the greater the coupling loss.

Factors Affecting Vibration Receiver

Receiver Factor Adjustment to Propagation Curve Comment

Floor-to-floor Attenuation 1 to 5 floors above grade: -2 

dB/floor

6 to 10 floors above grade: -1 

dB/floor additional

This factor accounts for dispersion and 

attenuation of the vibration energy as it 

propagates through a building.

Amplification due to 

Resonances of Floors, 

Walls, and Ceilings

+6 dB

The actual amplification will vary greatly 

depending on the type of construction. The 

amplification is lower near the wall-floor and 

wall-ceiling intersections.

Factors Affecting Ground-borne Noise

Receiver Factor Adjustment to Propagation Curve Comment

Radiated Sound Peak frequency of ground vibration:

 Low frequency (<30 Hz): -50 dB 

 Typical (peak 30 to 60 Hz):-35 dB 

 High frequency (>60 Hz): -20 dB 

Use these adjustments to estimate the Aweighted sound level given the average 

vibration velocity level of the room surfaces. 

See text for guidelines for selecting low-, 

typical-, or high-frequency characteristics. Use 

the high-frequency adjustment for subway 

tunnels in rock or if the dominant frequencies of 

the vibration spectrum are known to be 60 Hz or 

greater.

The following guidelines are used to select the appropriate adjustment factors. Note that the adjustments 

for wheel and rail condition for the steel-wheel technology are not cumulative. When more than one 

adjustment may apply, the general rule is to apply only the largest adjustment. For example, the 

adjustment for corrugated rail is 10 decibels and the adjustment for flat spots on wheels is 10 decibels. In 
8-8 High-Speed Ground Transportation Noise and Vibration Impact Assessment

an area with both, the projected vibration levels should be increased by 10 decibels, not 20 decibels. 

Similarly, only one of the vibration mitigation treatments is applied.

Factors Affecting Vibration Source

Train Speed: The levels of ground-borne vibration and noise vary approximately at 20 times the 

logarithm of speed. This relationship means that doubling train speed will increase the vibration 

levels approximately 6 decibels and halving train speed will reduce the levels by 6 decibels. The 

adjustments for 75 to 300 mph using a reference speed of 150 mph are given in Table 8-2. The 

relationship:

adjustment (VdB) = 















×

ref speed

speed 20 log

should be used to calculate the adjustments for other speeds.

Steel-Wheel Trainsets: The levels of ground-borne vibration and noise generated by a train passby 

depend heavily on the trainset's suspension system, wheel condition, and wheel type. The vehicle 

suspension consists of springs and dampers that affect the vibration transmitted to the track support 

system by the wheel/rail interaction. Generally, stiff springs tend to increase the frequency and 

amplitude of vibrations. Deteriorated wheel condition also will increase vibration levels. It can be 

assumed that a high-speed rail system will have wheels in good condition. However, when older 

vehicles will be used on new track, it may be appropriate to include an adjustment for wheel 

condition. Wheels with flat spots or corrugations can cause vibration levels that are 10 decibels 

higher than normal. Resilient wheels will reduce vibration levels at frequencie s greater than the 

effective resonance frequency of the wheel. Because this resonance frequency is relatively high, 

often greater than 80 Hz, resilient wheels usually have only a marginal effect on ground-borne 

vibration.

Track System and Support: The type of rail (welded or special trackwork), the track support system, and 

the condition of the rail all affect the vibration generated by the track system. The base curve 

(Figure 8-1) assumes welded rail in good condition. Jointed rail causes higher vibration levels than 

welded rail; however, track on new high-speed rail systems virtually always will be welded. The 

wheel impacts at special trackwork, especially frogs at crossovers, create much higher vibration 

forces than normally experienced on tangent track. Because of the higher vibration levels at 

special trackwork, crossovers often are the principal areas of vibration impact on new systems. 

Special spring- or movable-point frogs are used as a method of mitigating the vibration impact. 

These special frogs eliminate the gaps in the running rail. 

Modifying the track support system is another method of mitigating vibration impact. Special track 

support systems such as ballast mats, highly resilient track fasteners, resiliently-supported ties, and 

floating slabs all have been shown to be effective in reducing vibration levels.

The condition of the running surface of the rails can strongly affect vibration levels. Factors such 

as corrugations, general wear, or mill scale on new track can cause vibration levels that are 5 to 15 

decibels higher than normal. Mill scale usually will wear off after some time in service. However, 

the track must be ground to remove corrugations or to reduce the roughness from wear.
Chapter 8: Preliminary Vibration Assessment 8-9

Track Structure: The weight and size of the track structure affects the vibration radiated by that structure. 

Vibration levels will generally be lower for heavier track structures. Hence, the vibration levels 

from a cut-and-cover concrete double -box tunnel can be assumed to be lower than the vibration 

from a lightweight, concrete-lined bored tunnel. Whether or not the tunnel will be founded in 

bedrock is another factor affecting the radiated vibration. Bedrock is considered to be hard rock. It 

is usually appropriate to consider soft siltstone and sandstone to be more similar to soil than hard 

rock. As seen in Table 8-2, whether the tunnel is founded in soil or rock will make up to a 15 

decibel difference in the vibration levels. The vibration from aerial structures is lower than from 

at-grade track because of the mass of the structure, the reduced coupling to the ground, and the 

extra distance that the vibration must travel before it reaches the receiver.

Guideway Structure (Maglev): Vibration from maglev systems is not well documented. Limited data are 

available from measurements conducted on the prototype system operating in Germany. These 

data indicate that ground-borne vibrations depend on guideway structural design details. Lowest 

vibration levels are associated with the prototype concrete guideway. Higher levels are obtained 

near the steel and hybrid (concrete beam, steel deck) guideways. Vibration levels are even higher 

near the switch. A true at-grade maglev guideway has yet to be measured.

Factors Affecting Vibration Path

Propagation Characteristics: The General Assessment process requires the selection of one general 

propagation characteristic. When considering at-grade vibration sources, the selection is between 

"normal" vibration propagation and "efficient" vibration propagation. Efficient vibration 

propagation results in vibration levels approximately 10 decibels higher than normal vibration 

propagation, which more than doubles the potential impact zone for ground-borne vibration. 

Although geologic conditions are known to have a significant effect on the vibration levels, it is 

rarely possible to develop more than a broad-brush understanding of the vibration propagation 

characteristics for a General Assessment. The conservative approach would be to use the 10-

decibel adjustment for efficient propagation to evaluate all potential vibration impact. The problem 

with this approach is that it tends to overstate greatly the potential for vibration impact. Hence, it is 

best to review available geological data and any complaint history from existing rail lines and 

major construction sites near the high-speed rail corridor to identify areas where efficient 

propagation is possible. If there is any reason to suspect efficient propagation conditions, then a 

Detailed Analysis during final design should include vibration propagation tests at the areas 

identified as potentially efficient propagation sites.

Some geologic conditions are repeatedly associated with efficient propagation. Shallow bedrock, 

less than 30 feet below the surface, is likely to cause efficient propagation. Other factors that can 

be important are soil type and stiffness. In particular, soils with heavy clay content have 

sometimes been associated with efficient vibration propagation. Investigation of soil-boring 

records can be used to estimate depth to bedrock and the presence of problem soil conditions. 

Coupling-to-Building Foundation: Since annoyance from ground-borne vibration and noise is an indoor 

phenomenon, the effects of the building structure and its foundation on the vibration propagation 

path must also be considered. Wood frame buildings, such as the typical residential structure, are 

more easily excited by ground-borne vibration than heavier buildings. In contrast, large masonry 

buildings with spread footings have a low response to ground-borne vibration.
8-10 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Factors Affecting Vibration Receiver

Type of Building and Receiver Location in Building: Vibration generally reduces in level as it 

propagates through a building. As indicated in Table 8-2, a 1- to 2-decibel attenuation per floor is 

usually assumed. Resonances of the building structure, particularly the floors, will tend to 

counteract this attenuation and will cause some amplification of the vibration. Consequently, for a 

wood-frame structure, the building-related adjustments nearly cancel out. The adjustments for the 

first floor assuming a basement are: -5 decibels for the coupling loss; -2 decibels for the 

propagation from the basement to the first floor; and +6 decibels for the floor amplific ation. The 

total adjustment is -1 decibel.

Vibration Radiated as Ground-Borne Noise: The levels of radiated noise can be estimated given the 

average vibration amplitude of the room surfaces (floors, walls and ceiling) and the total acoustical 

absorption in the room. The average result is that the numerical value of sound-pressure level is 

approximately equal to that of the vibration velocity level when the velocity level is referenced to 

1x10-6in/sec. However, to estimate the A-weighted sound level from the velocity level, it is 

necessary to have some information about the frequency spectrum. The A-weighting adjustment 

drops rapidly at low frequencies, reflecting the relative insensitivity of human hearing to low 

frequencies. For example, A-weighting is -16 dB at 125 Hz, -26 dB at 60 Hz and -40 dB at 30 Hz. 

Adjustments for vibration depending on whether it has low-frequency, typical or high-frequency 

characteristics are provided in Table 8-2. Some general guidelines for classifying the frequency 

characteristics are:

• Low Frequency: Low-frequency vibration characteristics can be assumed for most surface 

track, tunnels surrounded by sandy soil with low cohesion, or a track support system with 

vibration isolation. 

• Typical: The typical vibration characteristic is the default assumption to be used for tunnels 

unless information indicates that one of the other assumptions is appropriate. It should be 

used for surface track when the soil is very stiff with a high clay content.

• High Frequency: High-frequency characteristics should be assumed for tunnels whenever 

the transit structure is founded in rock or when there is very stiff clay soil.

A factor that can be particularly complex to address is the effect of vibration propagation through rock. 

There are three factors from Table 8-2 that need to be included when a tunnel will be founded in rock:

• The -15 decibel adjustment in the "Type of Track Structure" category. 

• The adjustment based on the propagation distance in the "Geologic Conditions" category. 

This positive adjustment increases with distance because vibration attenuates more slowly in 

rock than in soil.

• The "Coupling to Building" category. When a building foundation is directly on the rock 

layer, there is no "coupling loss" due to the weight and stiffness of the building. The 

standard coupling factors should be used if there is at least a 8-foot layer of soil between the 

building foundation and the rock layer.
Chapter 8: Preliminary Vibration Assessment 8-11

8.3 INVENTORY OF VIBRATION IMPACT

The results of the General Assessment are expressed in terms of an inventory of all sensitive land uses 

where either ground-borne vibration or ground-borne noise from the project exceed the impact thresholds 

described in Chapter 7. The General Assessment may include a discussion of mitigation measures likely 

be needed to reduce vibration to acceptable levels at impacted locations.

The purpose of the General Assessment procedure is to develop a reasonably complete inventory of the 

buildings that may experience ground-borne vibration or ground-borne noise that exceed the impact 

criteria. At this point, a conservative assessment of the impact is preferred. It is better to include some 

buildings where ground-borne vibration may be below the impact threshold than to exclude buildings 

where it may exceed the impact threshold.

The steps for developing the inventory are:

Step 1: Identification of Vibration-sensitive Land Uses

1) Identify all vibration-sensitive land uses within Screening Distance from Table 8-1.

2) Categorize vibration-sensitive land uses according to the categories in Table 7-1.

3) Construct tables of land uses by category.

Step 2: Estimation of Vibration Impact

1) Apply General Assessment procedure to obtain ground-borne vibration and groundborne noise levels at each sensitive land use identified in Step 1.

2) Compare estimation with impact thresholds in Table 7-1.

3) Identify vibration-sensitive land uses where impact thresholds are exceeded.

Step 3: Preparation of Impact Inventory

1) Prepare summary tables showing the number of buildings in each category impacted 

by ground-borne vibration and ground-borne noise. This tabluation is done for 

each alternative.

2) Utilize the summary tables to compare alternatives by the number of buildings impacted.

Step 4: Mitigation of Impact

1) Select appropriate mitigation method from Section 9-4.

2) Re-assess impacts based on application of mitigation measures.

An example of a receiver-specific General Vibration Assessment for a hypothetical high-speed rail 

project follows. The assumed parameters of the project and receiver are typical of the preliminary 

planning stage of a project, and it is assumed that no project-specific vibration measurements have been 

performed.
8-12 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Example 8-1. General Vibration Assessment of a High-Speed Train Alignment

A high-speed train proposed for a corridor in the Midwest passes through a suburb an average of once an 

hour. A hospital is located 30 feet from the right-of-way line. The train speed is projected to be 120 mph 

in this section. The tracks are continuously welded on concrete tie -and-ballast in this at-grade section. 

The distance from track centerline to the right-of-way is 50 feet. Soil conditions are unknown. 

Determine if ground-borne vibration and noise from the train will cause impact on the second floor of this 

three-story brick building.

Step 1: Identification of Vibration-Sensitive Land Use

1) Category . A hospital is categorized in “Vibration Category 2: Residential” 

according to Chapter 7.

2) Screen. The “Vibration Screening Procedure” in Section 8.1 shows that for a 120-

mph train with “infrequent” service (less than 70 passbys per day), a residential 

land use within 100 feet should be identified as a potentially affected location. 

The hospital is located 80 feet from the tracks, well within the screening 

distance.

Step 2: Estimation of Vibration Impact

1) Base Curve. The “Generalized Ground-Borne Vibration Curve” (Figure 8-1) shows a 

vibration level of 78 VdB at 80 feet for a train at 150 mph.

2) Adjustments. Refer to Table 8-2.

2.1 Speed Adjustment. Adjustments for speeds other than 150 mph are 

included in Table 8-2. Unfortunately, 120 mph is not one of the 

adjustments given. Therefore, the speed correction of 20 log (speed/150) 

is used.

20 log (120/150) = -1.9 dB

Round off to -2 dB.

2.2 Trainsets. Assume wheels in good condition. No adjustment is applied.

2.3 Track System. Assume rails are in good condition. No adjustment. 

2.4 Track Structure. At-grade tie and ballast is the reference condition. No 

adjustment is applied.

2.5 Propagation Characteristics. Propagation is considered to be normal 

unless proven otherwise. The soil conditions are unknown, so assume no 

adjustment.

2.6 Type of Building and Receiver Location. The hospital building falls into 

the category of “2-4 Story Masonry” so the coupling adjustment is -10db. 

The receiver is on the 2nd floor so the “Floor-to-floor 
Chapter 8: Preliminary Vibration Assessment 8-13

Attenuation” is -2dB. Low-frequency characteristics can be assumed for 

most surface track, so the “Radiated Sound” adjustment is -50dB to 

convert the vibration level in VdB to sound level in dBA.

2.7 Calculation

i. Ground-Borne Vibration:

Base vibration level = 78 VdB

Speed adjustment = -2 dB

Wheel condition = 0 dB

Track system = 0 dB

Track structure = 0 dB

Propagation = 0 dB

Foundation coupling = -10 dB

Receiver location = -2 dB

Floor response = +6 dB

 _______

Estimated Vibration

Level = 70 VdB

ii. Ground-Borne Noise:

Vibration Level = 70 VdB

Radiated Sound = -50 VdB to dBA adjustment

_______

Estimated Sound Level = 20 dBA

2.8 Impact Assessment. Ground-borne vibration and noise impact criteria are 

given in Table 7-1. The hospital in this case falls under “Category 2: 

Residential” land uses exposed to “Infrequent Events.” The 

corresponding threshold for ground-borne vibration impact is 80 VdB 

and for ground-borne noise impact is 43dBA. Neither threshold is 

exceeded at the hospital.

End of Example 8-1

8-14 High-Speed Ground Transportation Noise and Vibration Impact Assessment 

Chapter 9: Detailed Vibration Assessment 9-1

CHAPTER 9 - DETAILED VIBRATION ASSESSMENT

The Detailed Assessment approach presented in this chapter provides a means to determine general 

vibration propagation conditions along a proposed high-speed train corridor and to develop specific 

projections for sensitive buildings where vibration impact is predicted by a General Assessment. The 

goal of the Detailed Assessment is to develop accurate projections of ground-borne vibration using all 

available tools and, when necessary, to design mitigation measures.

Local geologic conditions can have a very large effect on the impact distances of ground-borne vibration. 

This effect was dramatically demonstrated by the vibration test results described in Appendix D. 

Vibration measurements of the X2000 trains in Sweden indicate that, at the test site, impacts could occur 

at distances greater than 300 feet from the tracks. In contrast, the tests also showed that the X2000 trains 

at the TGV test site in France would not cause vibration impacts beyond about 60 feet. The difference 

appears to be entirely due to the geologic conditions. 

Projections using the General Assessment procedures described in Chapter 8 are based on the high range 

of data from sites that appear to have "normal" geology. This means that the actual levels of groundborne vibration will usually be 5 VdB or more lower than projections developed using the General 

Assessment curve and adjustments, and will rarely exceed projections developed using the General 

Assessment approach. However, an important qualification is that there will be some, apparently rare, 

conditions where the actual levels of ground-borne vibration will be substantially higher than those 

projected using the General Assessment procedures.

As indicated above, it can be appropriate to use the Detailed Assessment procedures at several locations 

along the proposed corridor during the preliminary phases of a high-speed train project to refine the 

General Assessment projection curves. A Detailed Assessment is also appropriate during the final design 

and engineering phases for areas where a General Assessment has indicated the potential for impact. 

Procedures for developing detailed assessments of ground-borne vibration are constantly evolving. 

Analytical techniques for solving vibration problems are complex and the technology continually 

advances. The material contained in this chapter is not intended to provide the novice with a complete 

methodology for conducting a Detailed Assessment. Rather, the approach presented focuses on the key 

steps usually taken by a qualified professional.
9-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Three examples of cases where Detailed Vibration Assessment might be required are:

1. A particularly sensitive building, such as a major concert hall, is within the impact zone. A 

Detailed Assessment would ensure that effective vibration mitigation is feasible and economically 

reasonable.

2. The General Assessment indicates that a proposed high-speed rail project may create vibration 

impact for a large number of residential buildings adjacent to the alignment. The projections for 

many of the buildings exceed the impact threshold by less than 5 decibels, which means that more 

accurate projections may show that vibration levels will be below the impact criterion. If the cost 

of measures to mitigate vibration would significantly increase project costs, a Detailed Assessment 

to determine the vibration impact as accurately as possible is warranted.

3. A high-speed rail alignment will be close to university research buildings where vibration-sensitive 

optical instrumentation is used. Vibration from the trains could make it impossible to continue to 

use the building for this type of research. A Detailed Assessment would determine if it is possible 

to control the vibration from the trains so that sensitive instrumentation would not be affected.

A Detailed Vibration Assessment consists of three main steps:

Step 1. Survey Existing Vibration. Although knowledge of the existing levels of ground-borne 

vibration is not usually required for the assessment of vibration impact, a survey of the 

existing vibration may be valuable in some instances. Examples include documenting 

existing background vibration at sensitive buildings, measuring the vibration levels created 

by sources such as existing rail lines, and, in some cases, characterizing the general 

background vibration in the project corridor. Characterizing existing vibration conditions is 

discussed in Section 9.1.

Step 2. Predict Future Vibration and Vibration Impact. All of the available analytical tools 

should be applied in a Detailed Assessment to develop the best possible estimates of the 

potential for vibration impact. An approach to projecting ground-borne vibration that 

consists of measuring vibration propagation characteristics at specific sites is discussed in 

Section 9.3. The vibration propagation test procedure is described in Section 9.3 and the 

assessment of vibration impact is discussed in Section 9.1.

Step 3. Develop Mitigation Measures. Controlling the impact from ground-borne vibration 

requires developing cost-effective measures to reduce the vibration levels. The Detailed 

Assessment can identify practical vibration control measures that will be effective at the 

dominant vibration frequencies and compatible with the given trackway structure (aerial, atgrade, subway) and track support system. Vibration mitigation measures are discussed in 

Section 9.4.

The discussion in this chapter generally assumes vibration analysis of steel-wheel rail systems. The 

procedures are equally applicable to maglev systems. 
Chapter 9: Detailed Vibration Assessment 9-3

9.1 ASSESSMENT OF VIBRATION IMPACT

The purposes of the vibration impact assessment are to inventory all sensitive land uses that may be 

adversely affected by the ground-borne vibration and noise from a proposed high-speed train project and 

to determine the mitigation measures that will be required to eliminate or minimize the impacts. This 

requires projecting the levels of ground-borne vibration and noise, comparing the projections with the 

appropriate impact criteria, and developing a list of suitable mitigation measures. The General 

Assessment is incorporated as an intermediate step in the impact assessment because of its relative 

simplicity and potential to narrow the areas requiring Detailed Assessment.

The assessment of vibration impact proceeds according to the following steps:

Step 1: Screening. Screen the entire proposed high-speed train corridor to identify areas where there is 

the potential for impact from ground-borne vibration. The vibration screening method is described 

in Chapter 8. If sensitive land uses are not located within the screening distances, it is not 

necessary to perform any further assessment of ground-borne vibration. 

Step 2: Vibration Source Levels. Define a curve of ground-surface vibration level as a function of 

distance that can be used with the General Assessment. Usually this will mean selecting the 

generalized curve from Figure 8-1 or adapting measurements from an existing facility.

Step 3: Vibration Propagation Characteristics. Use the General Assessment Procedure to estimate 

vibration levels for specific buildings or groups of buildings. 

Step 4: Study Area Characteristics. In some cases a vibration survey to characterize existing ambient 

vibration may be necessary. As discussed in Section 9.2, although knowledge of the existing 

ambient vibration is not generally required to evaluate vibration impact, there are times when a 

survey of existing conditions is valuable. One common example is when the train project will be 

located in an existing rail right-of-way shared by freight trains. Guidelines on the procedure to be 

used to account for existing vibration that is higher than the impact limit for the project vibration 

are provided in Chapter 7.

Step 5: Vibration Impact Estimation and Inventory. Compare the projected levels with the impact 

criteria given in Table 7-1 to determine whether vibration impact is likely. The goal of this step is 

to develop a reasonably accurate catalog of the buildings that will experience ground-borne 

vibration or noise levels that exceed the criteria. In the General Assessment, it is best to make a 

conservative assessment of the impact by including some buildings where the actual vibration 

ultimately is at or slightly below the impact threshold. Usually it is far easier to control vibration 

during design and construction rather than to retrofit vibration control measures to solve 

unanticipated problems that develop once the system is operational. In locations where General 

Assessment indicates impact, the more refined techniques of Detailed Assessment should be 

employed. 

Step 6: Vibration Mitigation. For areas where the impact criteria may be exceeded, review potential 

mitigation measures and assemble a list of feasible approaches to vibration control. To be feasible, 

the measure, or combination of measures, must be capable of providing a significant reduction of 

the vibration levels, usually at least 4 dB, while being cost effective. 
9-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Because vibration control is frequency-dependent, specific recommendations of vibration control 

measures can be made only after the frequency characteristics of the vibration have been evaluated. 

Use the Detailed Vibration Assessment to develop specific mitigation recommendations where it is 

important to estimate the spectrum of ground-borne vibration at potentially affected buildings. 

This type of assessment is often performed during final design rather than during the environmental 

assessment stage. Because a Detailed Assessment is more accurate than a General Assessment, 

there will be cases where the Detailed Assessment will show that the vibration and noise levels will 

be below the applicable criteria and that mitigation is not required. If the projected levels are still 

above the limits, the spectra provided by the Detailed Assessment should be used to evaluate 

mitigation measures.

9.2 CHARACTERIZING EXISTING VIBRATION CONDITIONS

Ambient vibration is rarely of sufficient magnitude to be perceptible or to cause audible ground-borne 

noise unless there is a major vibration source close by, such as a rail line. In most cases, perceptible 

vibration inside a building is caused by equipment or activities within the building itself, such as heating 

and ventilation systems, footsteps, or doors closing. Because the existing ambient vibration is usually 

below human perception, a limited survey is sufficient even for a Detailed Assessment. This contrasts 

with analysis of noise impact, where documenting the existing ambient noise level is required to assess 

the impact. 

Examples of situations where measurements of the ambient vibration are valuable include:

• Determining existing vibration at sensitive buildings. Serious vibration impact may occur when 

there is vibration-sensitive manufacturing, research, or laboratory activities within the screening 

distances. Careful documentation of the existing vibration will provide valuable information on the 

real sensitivity of the activity to external vibration and will provide a reference condition under which 

vibration is acceptable.

• Using existing vibration sources to characterize propagation. Existing vibration sources such as 

freight trains, industrial processes, quarrying operations, or normal traffic sometimes can be used to 

characterize vibration propagation. Carefully designed and performed measurements may eliminate 

the need for more complex propagation tests.

• Documenting existing levels of general background vibration. Some measurements of the 

existing levels of background vibration can be useful simply to document that, as expected, the 

vibration is below the normal threshold of human perception. Existing vibration in urban and 

suburban areas is usually due to traffic. If a measurement site has existing vibration approaching the 

range of human perception (e.g., the maximum vibration velocity levels are greater than about 65 

VdB), then this site should be carefully evaluated for the possibility of ground conditions causing 

"efficient" vibration propagation. Areas with efficient vibration propagation could have vibration 

problems when the project is built.

• Documenting vibration from existing rail lines. Measurements to document the levels of vibration 

created by existing rail lines can be important in evaluating the impact of the new vibration source 

and determining vibration propagation characteristics in the area. As discussed in Chapter 7, if 
Chapter 9: Detailed Vibration Assessment 9-5

vibration from an existing rail line will be higher than that from the high-speed trains, there may not 

be impact even though the normal impact criterion would be exceeded.

Although ground-borne vibration is almost exclusively a problem inside buildings, measurements of 

existing ambient vibration generally should be performed outdoors. Two important reasons for this are: 

(1) equipment inside the building may cause more vibration than exterior sources, and (2) the building 

structure and the resonances of the building can have strong, but difficult to predict, effects on the 

vibration. However, there are situations where measurements of indoor vibration are appropriate. For 

example, documenting vibration levels inside a vibration-sensitive building can be important since 

equipment and activities inside the building may cause vibration greater than that from external sources 

such as street traffic or aircraft overflights. Floor vibration measurements should be taken near the center 

of a floor span where the vibration amplitudes are the highest.

The goal of most ambient vibration tests is to characterize the root mean square (RMS) vertical vibration 

velocity level at the ground surface. In almost all cases, it is sufficient to measure only vertical vibration 

and ignore the transverse components of the vibration. Although transverse components can transmit 

significant vibration energy into a building, the vertical component usually has greater amplitudes than 

transverse vibration. Moreover, vertical vibration is usually transmitted more efficiently into building 

foundations than transverse vibration.

The manner in which a transducer used to measure vibration is mounted can affect the measured levels of 

ground-borne vibration. However, research has shown that, at the frequencies usually of concern for 

ground-borne vibration (generally less than 200 Hz), straightforward methods of mounting transducers on 

the ground surface or on pavement are adequate for vertical vibration measurements.43,44,45 Quick-drying 

epoxy or beeswax can be used to mount transducers to smooth paved surfaces or to metal stakes driven 

into the ground. Rough concrete or rock surfaces require special mountings. One approach is to use a 

liberal base of epoxy to attach small aluminum blocks to the surface and then mount the transducers on 

the aluminum blocks.

Selecting sites for an ambient vibration survey primarily requires good common sense. Sites selected to 

characterize a high-speed train corridor should be distributed along the entire project and should be 

representative of the types of vibration environments found in the corridor. These would commonly 

include: 

 

43J.T. Nelson, H.J. Saurenman, G.P. Wilson, "Metrorail Operational Sound Level Measurements: GroundBorne Vibration and Noise Levels," prepared by Wilson Ihrig & Associates for Washington Metropolitan Area 

Transit Authority, December 1979.

44T.G. Gutowski, L.E. Wittig, C.L. Dym, "Some Aspects of the Ground Vibration Problem," Noise Control 

Engineering, vol. 10:3, pp 94-101, 1978.

45H. Nolle, "High Frequency Ground Vibration Measurements," Shock and Vibration Bulletin, vol. 48:4, pp 

95-103, 1978.
9-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment

• sites in quiet residential areas removed from major traffic arterials to characterize low-ambient 

vibrations,

• sites along major traffic arterials and highways or freeways to characterize high vibration areas,

• sites in any area with vibration-sensitive activities, and

• sites near any significant existing source of vibration such as a railroad line.

The transducers should be located near the building setback line for background vibration measurements. 

Ambient measurements along railroad lines ideally will include: multiple sites; several distances from the 

rail line at each site; and 4 to 10 train passbys for each test. Because of the irregular schedule for freight 

trains and, on many rail lines, the low number of operations each day, it is often impractical to perform 

tests at more than two or three sites along the rail line or to measure more than two or three passbys at 

each site. Rail type and condition strongly affect the vibration levels. Consequently, the track at each 

measurement site should be inspected by experienced personnel to locate any switches, bad rail joints, 

corrugations, or other factors that could be responsible for higher than normal vibration levels.

The appropriate methods of characterizing ambient vibration are dependent on the type of information 

required for the analysis. Some examples are as follows:

Ambient Vibration: Ambient vibration is usually characterized with a continuous 10- to 30-minute 

measurement of vibration. The equivalent energy level, or Leq, of the vibration velocity level over 

the measurement period gives an indication of the average vibration energy. Leq is equivalent to a 

long averaging time RMS level. Specific events can be characterized by the maximum RMS level 

(Lmax) of the event or by performing a statistical analysis of RMS levels over the measurement 

period. An RMS averaging time of one second should be used for statistical analysis of the 

vibration level.

Specific Events: Specific events such as train passbys should be characterized by the RMS level during 

the time that the train passes by. If the locomotives have vibration levels more than 5 VdB higher 

than the vehicles, a separate RMS level for the locomotives should be obtained. The locomotives 

usually can be characterized by the Lmax during the train passby. The RMS averaging time or time 

constant should be one second when determining Lmax. Sometimes it is adequate to use Lmax to 

characterize the train passby, which is simpler to obtain than the RMS averaged over the entire train 

passby.

Frequency Analysis: When the vibration data will be used to characterize vibration propagation or for 

other special analysis, a frequency analysis of the vibration is required. An example would be if 

vibration transmission characteristics of the ground are suspected of having particular frequency 

characteristics. For many analyses, 1/3 octave band charts are best for describing the vibration 

characteristics. Narrowband spectra also can be valuable, particularly for identifying pure-tone 

characteristics and designing mitigation measures.

It is preferable that ambient vibration be characterized in terms of the RMS velocity level, not the peak 

particle velocity (PPV), which is commonly used to monitor construction vibration. As discussed in 

Chapter 6, RMS velocity level is considered to be better correlated to human response than PPV.
Chapter 9: Detailed Vibration Assessment 9-7

9.3 VIBRATION PREDICTION PROCEDURE

9.3.1 Background

Predicting ground-borne vibration associated with a transportation project is a developing field. 

Because ground-borne vibration is a complex phenomenon that is difficult to model and predict 

accurately, most projection procedures that have been used for high-speed train and other types 

of rail projects rely on empirical data. Although no single method stands out as the best 

approach for all situations, the procedure described in this section is one of the most promising 

because it is based on site-specific tests of vibration propagation. The procedure, which was 

developed under an FTA (formerly UMTA) research contract,46 is recommended for detailed 

evaluations of ground-borne vibration. The same procedure is discussed in Chapter 11 of the 

FTA manual Transit Noise and Vibration Impact Assessment.47 Other approaches to predicting 

ground-borne vibration have included pure analytical and pure numerical approaches. Some of 

these approaches were presented at an international workshop on railway noise.48

There is still work to be done before a comprehensive prediction method will be available that can be 

confidently applied on sensitive projects. The measurements of high-speed train vibration performed in 

France, Italy, and Sweden as part of preparation of this manual are discussed in Appendix D. An 

important observation from those tests is that vibration from high-speed trains is not caused by 

mechanisms that are substantially different than vibration from lower speed trains such as rapid transit 

and light rail trains. This means that procedures for predicting vibration from transit and passenger trains 

are equally applicable to high-speed trains, following scaling to the appropriate speed. The data show that 

vibration amplitudes are approximately proportional to 20×log(speed) from 50 mph to over 150 mph.

Perhaps the biggest problem for most prediction approaches is that vibration propagation through the soil 

and rock layers that are between the source and the receiver is extremely difficult to define. Attenuation 

along the propagation path is a critical component of any prediction procedure. Even when boreholes are 

made at regular intervals along a rail alignment, unless the geology is very uniform, they do not uncover 

geologic variations along the vibration propagation path from the train line to receiver, which is 

perpendicular to the guideway. A primary goal of the procedure presented in this section is to 

characterize vibration propagation with empirical tests. This makes it unnecessary to infer propagation 

characteristics from standard geologic parameters such as soil classification, wave speed, and density. 

 

46J.T. Nelson, H.J. Saurenman, "A Prediction Procedure for Rail Transportation Ground-Borne Noise and 

Vibration," Transportation Research Record 1143, National Research Council, Transportation Research Board 

(Washington, D.C.), August 1988.

47U.S. Department of Transportation, Federal Transit Administration, Transit Noise and Vibration Impact 

Assessment, Report DOT-T-95-16, April 1995.

48 "The Fifth International Workshop on Railway and Tracked Transit System Noise," Voss, Norway, June 

21-24, 1995, (Proceedings published in Journal of Sound Vibration, Vol. 193, No. 1, 1996).
9-8 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Experience has shown that the test procedure provides a reasonable estimate of vibration propagation 

characteristics and that it can identify areas where ground-borne vibration will be higher than normal 

because of geologic conditions that promote efficient propagation.

9.3.2 Overview of Prediction Procedure using Measured Transfer Mobility

The prediction method described in this section was developed to enable train vibration measurements 

collected in one city to be used to predict vibration levels in another city where the geologic conditions 

may be completely different. The procedure uses a special measured function, called transfer mobility, 

which defines the relationship between an exciting force and the resulting vibration velocity at the ground 

surface. The transfer mobility combines the effects of the media the vibration waves pass through, the 

types of vibration waves, and all possible paths the vibration can take to go from the source to the 

receiver. 

Transfer mobility is a function of both frequency and distance from the source. The transfer mobility 

between two points completely defines the composite vibration propagation characteristics between the 

two points. In most practical cases, receivers are close enough to the train tracks that the vibration cannot 

be considered to be originating from a single point; the vibration source is more appropriately 

characterized as a line source. Consequently, the point transfer mobility must be modified to approximate 

a line source. In the text that follows, TMpoint is used to indicate the measured point source transfer 

mobility and TMline is used for the line source transfer mobility derived from TMpoint. Both are assumed 

to be in decibels with consistent reference quantities.

Predicting ground-borne vibration at a specific site requires the transfer mobility function for the site and 

an applicable force density function. The force density function is usually derived from measurements at 

an existing high-speed train line. In essence, the force density is the normalized ground-borne vibration 

with the effects of geology removed. The measured transfer mobility of a site along an existing highspeed train system can be used to estimate the force density function that is independent of the geology. 

The prediction procedure considers ground-borne vibration to be divided into the following components:

1. Excitation Force (Force Density): The vibration energy is created by oscillatory and impulsive 

forces. Steel wheels rolling on smooth steel rails create random oscillatory forces. When a wheel 

encounters a discontinuity such as a rail joint, an impulsive force is created. The force excites the 

track structure, such as the railway tunnel, or the ballast for at-grade track. In the prediction 

method, the combination of the actual force generated at the wheel/rail interface and the vibration 

of the track structure are usually combined into an equivalent force density level. The force density 

level describes the force that excites the soil/rock surrounding the track structure.

2. Vibration Propagation (Transfer Mobility): The excitation of the track structure causes 

vibration waves in the soil that propagate away from the track structure. Vibration energy can 

propagate through the soil or rock in a variety of wave forms. All ground vibration includes shear 

and compression waves. In addition, Rayleigh waves, which propagate along the ground surface, 

can be a major carrier of vibration energy. The mathematical modeling of vibration is complicated 

when, as is usually the case, there are soil strata with different elastic properties. The propagation 

through the soil/rock is modeled using the experimentally determined transfer mobility.

3. Building Vibration: When the ground vibration excites a building foundation, it sets the building 

into motion and starts vibration waves propagating throughout the building structure. The 
Chapter 9: Detailed Vibration Assessment 9-9

interaction between the ground and the foundation causes some reduction in vibration levels. The 

amount of reduction depends on the mass and stiffness of the foundation. The more massive the 

foundation, the lower the response to ground vibration. As the vibration waves propagate through 

the building, they can create perceptible vibration and cause annoying rattling of windows and 

decorative items either hanging on walls or located on shelves. 

4. Audible Noise: In addition to perceptible vibration, the vibration of room surfaces radiates lowfrequency sound that may be audible. The sound level is affected by the amount of acoustical 

absorption in the receiver room.

The combination of the force density level and the transfer mobility is used to predict the ground-surface 

vibration. A fundamental assumption of the prediction approach outlined here is that the force density, 

transfer mobility, and the building coupling to the ground are all independent factors. The following 

equations are the basis for the prediction procedure, where all of the quantities are in decibels with 

consistent reference values:

Lv = LF + TMline + Cbuild

LA = Lv + Krad + KA-wt

where: Lv = RMS vibration velocity level in one 1/3 octave band,

LA = A-weighted sound level in one 1/3 octave band,

LF = force density for a line vibration source such as a train,

TMline = line source transfer mobility from the tracks to the sensitive site,

Cbuild = adjustments to account for ground–building foundation interaction and 

attenuation of vibration amplitudes as vibration propagates through 

buildings,

Krad = adjustment to convert from vibration to sound pressure level, which also 

for the amount of acoustical absorption inside the room (A value of zero 

can be used for Krad for typical residential rooms when the decibel 

reference value for Lv is 1 micro in./sec.[ref. 4]), and

KA-wt = A-weighting adjustment at the 1/3 octave band center frequency.

All of the quantities given above are functions of frequency. The standard approach to dealing with the 

frequency dependence is to develop projections on a 1/3 octave band basis using the average values for 

each 1/3 octave band. The end result of the analysis is the 1/3 octave band spectra of the ground-borne 

vibration and the ground-borne noise. The spectra are then used to calculate overall vibration velocity 

level and the A-weighted sound level. This is in contrast to the General Assessment procedures, where 

the overall vibration velocity level and A-weighted sound level are predicted without any consideration of 

the particular frequency characteristics of the propagation path.

9.3.3 Measuring Transfer Mobility and Force Density (Vibration Propagation Testing)

The overall purpose of vibration propagation testing is to obtain data that can be used to estimate the 

following quantities: 

1. Point Source Transfer Mobility. This is basically an intermediate quantity that is applicable to 

point vibration sources. It is a function of both frequency and distance from the source.
9-10 High-Speed Ground Transportation Noise and Vibration Impact Assessment

2. Line Source Transfer Mobility. The measured point source transfer mobilities are used to estimate 

an equivalent line source transfer mobility for each test site.

3. Force Density. The force density characterizes the vibration-generating characteristics of the 

train/track system that will be used. It can be based on previous measurements, or testing can be 

done at an existing facility to measure the force density. If no suitable measurements are available, 

testing should be done at a high-speed rail facility with equipment similar to the planned vehicles. 

Adjustments for factors such as train speed, track support system, and vehicle suspension will 

usually be needed to match the force density to the conditions at specific sites. The force density 

represents an incoherent line of vibration force equal to the length of the trains. The unit of force 

density is force divided by square root of train length, represented here in decibels relative to 1 

lb/(ft)1/2. 

The basic field procedure for at-grade and tunnel testing of transfer mobility is illustrated in Figure 9-1. 

The goal of the test is to create vibration pulses that travel from the source through the ground to the 

receiver, using the same path that will be taken by ground-borne vibration from the train. As shown in 

Figure 9-1, a weight is dropped from a height of 3 to 4 feet onto a load cell, which is calibrated to 

measure force. Accelerometers are placed on the ground along a line leading away from the point of 

force application. The responses of the load cell and accelerometers are recorded on a multichannel tape 

recorder for subsequent analysis in the laboratory. 

When the procedure is applied to tunnels, the force must be located at the approximate depth of the 

tunnel. This is done by drilling a bore hole and locating the load cell at the bottom of the hole. The tests 

Figure 9-1 Impact Method for Measuring Transfer Mobility
Chapter 9: Detailed Vibration Assessment 9-11

are usually performed at the same time that the bore holes are drilled. This allows using the soil-sampling 

equipment on the drill rig for the transfer mobility testing. The load cell is attached to the bottom of the 

drill string and lowered to the bottom of the hole. A standard soil sampling hammer, which is usually a 

140-lb. weight dropped 18 inches onto a collar attached to the drill string, is used to excite the ground. 

The load cell must be capable of operating underwater if the water table is near the surface or if a slurry 

drilling process is used.

For point sources, such as the columns of a maglev guideway, a point source force spectrum is used 

instead of force density.

Field Procedures

The process of measuring transfer mobility involves impacting the ground and measuring the resulting 

vibration pulse at various distances from the impact. Two different methods, shown in Figure 9-2, that 

have been used to estimate equivalent line source transfer mobility from point source transfer mobility 

are:

1. Lines of transducers: A site is characterized by tests using one or more lines of transducers with the 

impact at one end of the line. The total length of the line ranges from 150 to 300 feet. Figure 9-2a 

shows a site being characterized using three lines perpendicular to the rail line. Regression 

techniques are applied to the 1/3 octave band transfer function data to obtain smooth point-source 

transfer mobility function curves. Once the point source transfer mobility has been defined, the

line source transfer mobility can be calculated using numerical integration techniques (ref. 4). 

Optimal use of a single borehole can be made by running three or four transducer lines in a radial 

pattern from each borehole.

2. Lines of impacts: This configuration is shown in Figure 9-2b. One line of transducers is used and 

the ground is impacted at evenly-spaced intervals along a line perpendicular to the transducer line. 

Since the impacts represent a train, it is best if the line of impacts can be along the track centerline. 

When this is not possible, the impact line should parallel the tracks. After the 1/3 octave band 

point source transfer mobilities are obtained, the equivalent line source transfer mobility is 

obtained by combining the point source transfer mobilities to approximate a numerical integration. 

This procedure was used to derive force density functions for X2000, Pendolino, and TGV high 

speed trains. Recent experience has shown that this approach is more accurate and more repeatable 

than the first approach. Unfortunately, this approach is usually impractical for tunnels since the 

ground must be impacted at the bottom of boreholes to approximate propagation from a tunnel 

structure.
9-12 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Instrumentation

Performing a vibration propagation test requires specialized equipment. Most of the equipment is readily 

available from several commercial sources. Commercially available load cells can be used as the force 

transducer. For borehole testing, the load cells must be hermetically sealed and capable of sustaining 

impact forces at the bottom of a 30- to 100-foot deep hole partia lly filled with water. A typical 

instrumentation array for field testing and laboratory analysis of transfer mobility is shown in Figure 9-3. 

The force transducer should be capable of impact loads of 5,000 to 10,000 pounds. Either accelerometers 

or geophones can be used as the vibration transducers. A requirement is that the transducers with 

associated amplifiers be capable of accurately measuring levels of 0.0001 inches/sec at 40 Hz and have 

flat frequency response from 6 Hz to 400 Hz. The tape recorder also must have flat response over the 6 to 

400 Hz frequency range. Adequate low-frequency response usually requires either an instrumentationquality FM recorder or a digital recorder. The response of most normal direct-record tape recorders is 

inadequate at frequencies below about 30 Hz. 

Figure 9-2 Schematic of Two Approaches for Transfer Mobility Measurements

Figure 9.2a Approach 1 for Vibration Propagation Tests Figure 9.2b Approach 2 for Vibration Propagation 

Tests
Chapter 9: Detailed Vibration Assessment 9-13

Figure 9-3 Equipment Required for Field Testing and Laboratory Analysis

The narrowband spectrum analyzer is the key element of the laboratory instrumentation. The analyzer 

must be capable of capturing impulses from at least two channels and calculating the frequency spectrum 

of the transfer function between the force and vibration channels. All transfer functions should include 

the average of at least 20 impulses. Averaging more impulses will improve signal enhancement at a rate 

of 3 dB improvement for each doubling of the number of impacts. Signal enhancement is particularly 

important when the vibration transducer is more than 100 feet from the impact.

As illustrated in Figure 9-3, the spectrum analyzer usually is interfaced to a computer, which is required 

to adapt the narrowband transfer function data into a format suitable for evaluating 1/3 octave band 

transfer mobility. The raw transfer function data usually include several hundred frequency bands. By 

transforming from narrowband to 1/3 octave band spectra, each spectrum is reduced to 15 to 20 bands. 

This step reduces the amount of data that must be evaluated to develop the generalized curves. There are 

specialized multi-channel spectrum analyzers that have built-in capabilities that are sufficient for this data 

analysis.

Analysis of Transfer Mobility Data

Transfer mobility functions are developed from field measurements in following steps:

Step 1. Analyze the field data to generate narrowband point source transfer mobilities.

Step 2. Calculate 1/3 octave band transfer mobilities at each measurement point from the narrowband 

results. Because typical spectrum analyzers are not capable of obtaining 1/3 octave band 

transfer functions, this processing is performed after transferring the data to a computer. 
9-14 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Step 3. Calculate the transfer mobility as a function of distance for each 1/3 octave band. 

Step 4. If steel-wheel point source technology at grade, compute the line source transfer mobility as a 

function of distance in each 1/3 octave band.

The two field test procedures that have been used to develop estimates of line-source transfer mobility are 

shown in Figure 9-2. Of the two procedures, the first, involving a single impact point for each line of 

accelerometers, requires considerably more analysis and professional judgment to develop line source 

transfer mobility. However, there are some situations, such as elevated guideway columns, where a 

single impact point is the only practical method to apply. 

The steps in developing line-source 

transfer mobility curves with field data 

from the first procedure are illustrated in 

Figure 9-4. The analysis starts with the 

narrowband transfer function between 

source and receiver at each measurement 

position. There should be a minimum of 

four distances in any test line. Because of 

the possibility of local variations in 

propagation characteristics, when feasible, 

three or more lines should be used to 

characterize a site. A total of 10 to 20 

transducer positions are often used to 

characterize each site. Assuming that the 

spectrum analyzer calculates 400 line 

narrowband transfer functions for each 

position, a total of 4,000 to 8,000 numbers 

must be calculated for each site.

The next step in the analysis procedure is to calculate the equivalent 1/3 octave band transfer functions. 

This reduces each spectrum from 400 to 15 numbers. As shown in Figure 9-4, the 1/3 octave band 

spectrum is much smoother than the narrowband spectrum. The third step is to calculate a best-fit curve 

of transfer mobility as a function of distance for each 1/3 octave band. When analyzing a specific site, the 

best-fit curve will be based on 10 to 20 data points. Up to several hundred points could be used to 

determine average best-fit curves for a number of sites.

The 1/3 octave band best-fit curves can be applied directly to point vibration sources. However, because 

trains are better represented as line vibration sources, a fourth step is necessary: calculate an equivalent 

line source transfer mobility using numerical integration. 

The analysis involving the second field procedure is slightly different from the first. In this approach, the 

train is represented by impacts at equally spaced intervals along a line perpendicular to the transducer 

line. This approach is particularly suited to characterizing a specific building since by placing a 

Figure 9-4 Analysis of Transfer Mobility
Chapter 9: Detailed Vibration Assessment 9-15

transducer inside the building; it is possible to measure line source transfer mobility from the tracks to 

this point in the building. The resulting transfer mobility combines the vibration path to the building 

foundation, coupling to the building, and propagation of the vibration energy through the building. This 

approach can greatly improve the accuracy of projections for that building.

Using the second procedure, a segment of a train can be represented by a line of impact positions along 

the track centerline at 10- or 20-foot intervals. The 1/3 octave band point source transfer mobilities for 

each transducer location can then be summed following the trapezoidal rule for numerical integration to 

directly calculate line-source transfer mobility. The following equation should be used to perform the 

numerical integration:

where: h = impact interval,

TMpi = point source transfer mobility for ith impact location, and

n = last impact location.

This approach is considerably more direct than is possible with lines of vibration transducers. An 

important feature of this approach is that the impact line usually can be shorter, sometimes much shorter 

than the train. For example, at a distance of 50 feet from a 600-foot train, most of the vibration energy 

will come for the part of the train closest to the receiver. In this case, the 600-foot train could be 

accurately modeled using a 200-foot impact line. Judgment must be used in deciding on an appropriate 

length for the impact line in balancing accuracy of the results, available test conditions in the field, 

budget, and time constraints.

Deriving Force Density

Force density is not a quantity that can be measured directly. It must be inferred from measurements of 

transfer mobility and train vibration at the same site. Using a line of impacts to measure line source 

transfer mobility (developed using the second transfer mobility test procedure) will give the best force 

density results. The force density for each 1/3 octave band is then simply:

LF = Lv - TMline

where: LF = force density,

LV = measured train ground-borne vibration, and

Tmline = line source transfer mobility.

The standard approach is to develop force density from the average of measurements at three or more 

positions. 









































2

10

+10 +...+10 +

2

10

TM = 10 x h x

10

TM

10

TM

10

TM 10

TM

line 10

p

n

pn-1p2

p

1

log
9-16 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Trackbed force densities developed from measurements of the Acela, TGV, X2000, and Pendolino trains 

are shown in Figure 9-5. Adjustments must be made to the force density to account for differences 

between the facility where the force density was measured and the new system. Guidance for making 

these adjustments can be found in a U.S. Department of Transportation report.49

A force spectrum developed from measurements of the Transrapid TR08 is shown in Figure 9-6.

9.3.4 Vibration and Structure-Borne Noise in Buildings

The propagation of vibration from the building foundation to the receiver room is a very complex 

phenomenon, dependent on the specific design of the building. Detailed evaluation of the vibration 

propagation requires extensive use of numerical procedures, such as finite element modeling. An 

evaluation this detailed generally is not practical for individual buildings considered in this manual. The 

propagation of vibration through a building and the radiation of sound by vibrating building surfaces 

consequently is estimated using simple empirical or theoretical models. The recommended procedures 

are outlined in the Handbook of Urban Rail Noise and Vibration Control50. The approach consists of 

adding the following adjustments to the 1/3 octave band spectrum of the projected ground-surface 

vibration:

1. Building response or coupling loss. This represents the change in the incident ground-surface 

vibration due to the presence of the building foundation. The adjustments in the Handbook are shown in 

Figure 9-7.

 

49J.T. Nelson, H.J. Saurenman, "State-of-the-Art Review: Prediction and Control of Ground-Borne Noise 

and Vibration from Rail Transit Trains," Report Number UMTA-MA-06-0049-83-4, U.S. Department of 

Transportation, Urban Mass Transit Administration, December 1983.

50H.J. Saurenman, J.T. Nelson, G.P. Wilson, Handbook of Urban Rail Noise and Vibration Control, 

prepared under contract to US DOT/Transportation Systems Center, Report UMTA-MA-06-0099-82-2, February 

1982.
Chapter 9: Detailed Vibration Assessment 9-17

Figure 9-5 Force Densities for High-Speed Trains

Figure 9-6 Characteristics Force Spectra for the TR08 on Each Type of Guideway
9-18 High-Speed Ground Transportation Noise and Vibration Impact Assessment

2. Transmission through the building. The vibration amplitude will decrease as the vibration 

energy propagates from the foundation through the remainder of the building. The normal 

assumption is that vibration attenuates by 1 to 2 dB for each floor.

3. Floor resonances. Vibration amplitudes will be amplified because of resonances of the 

floor/ceiling systems. For a typical wood frame residential structure, the fundamental 

resonance is usually in the 15 to 20 Hz range. Reinforced-concrete slab floors in modern 

buildings will have fundamental resonance frequencies in the 20 to 30 Hz range. An 

amplification resulting in a gain of approximately 6 dB should be used in the frequency range 

of the fundamental resonance. 

4. Radiated noise. The projected floor vibration is used to estimate the levels of ground-borne 

noise. The primary factors affecting noise level are the average vibration level of the room 

surfaces and the amount of acoustical absorption within the room. As discussed above, the 

radiation adjustment is zero for typical rooms, which gives:

LA » Lv + KA-wt

where: LA = A-weighted sound level in a 1/3 octave band,

Lv = average RMS vibration velocity level, and

KA-wt = A-weighting adjustment at the center frequency of the 1/3 octave band.

The A-weighted levels in the 1/3 third octave bands are then combined to give the overall Aweighted sound level.

Figure 9-7 Approximate Foundation Response for Various Types of Buildings (Ref. 50)
Chapter 9: Detailed Vibration Assessment 9-19

9.4 VIBRATION MITIGATION

Mitigation can minimize the adverse effects of project ground-borne vibration on sensitive land uses. 

Available data indicate that ground-borne vibration from steel-wheel/steel-rail high-speed trains is caused 

by the same mechanisms as vibration from lower speed trains. Consequently, the approaches to 

controlling ground-borne vibration from transit systems generally are applicable to high-speed trains. 

Because ground-borne vibration is not as common a problem as environmental noise, the mitigation 

approaches have not been as well defined. In some cases it has been necessary to develop innovative 

approaches to control the impact. Examples are the floating slab systems that were developed for the 

Washington, D.C. and Toronto transit systems and wheel-flat detectors that have been used to identify 

vehicles in need of maintenance. 

The importance of adequate wheel and rail maintenance in controlling levels of ground-borne vibration 

cannot be overemphasized. Problems with rough wheels or rails can increase vibration levels by as much 

as 20 dB, negating the effects of even the most effective vibration control measures. It is rare that 

practical vibration control measures will provide more than 15 to 20 dB attenuation. When ground-borne 

vibration problems are associated with existing rails and rolling stock, often the best control measure is to 

implement new or improved maintenance procedures. Grinding rough or corrugated rail and 

implementing wheel truing to restore the wheel surface and contour may reduce vibration more than 

completely replacing the existing track system with floating slabs.

Assuming that the track and vehicles are in good condition, the options to further reduce ground-borne 

vibration fit into one of seven categories: (1) maintenance procedures, (2) location and design of special 

trackwork, (3) vehicle modifications, (4) changes in the track support system, (5) building modifications, 

(6) adjustments to the vibration transmission path, and (7) operational changes.

Maintenance

As discussed above, effective maintenance programs are essential for keeping ground-borne vibration 

levels under control. When the wheel and rail surfaces are allowed to degrade, the vibration levels can 

increase by as much as 20 dB compared to a new or well maintained system. Maintenance procedures 

that are particularly effective at avoiding increases in ground-borne vibration include:

• Rail grinding on a regular basis, particularly for rail that develops corrugations. Rail condition 

monitoring systems are available to optimize track conditions.

• Wheel truing to re-contour the wheel, provide a smooth running surface, and remove wheel flats. 

The most dramatic vibration reduction results from removing wheel flats. However, significant 

improvements also can be observed simply from smoothing the running surface. Wheel condition 

monitoring systems are available to optimize wheel conditions.
9-20 High-Speed Ground Transportation Noise and Vibration Impact Assessment

• Reconditioning vehicles, particularly when components such as suspension system, brakes, and 

wheels will be improved, and slip-slide detectors will be installed.

• Installing wheel condition monitoring systems to identify those vehicles most in need of wheel 

truing.

Location and Design of Special Trackwork

Most vibration impact from a new train system is caused by wheel impacts at the special trackwork for 

turnouts and crossovers. Careful review of crossover and turnout locations during the preliminary 

engineering stage is an important step in minimizing potential for vibration impact. When feasible, the 

most effective vibration control measure is to relocate the special trackwork to a less vibration-sensitive 

area. Sometimes this requires adjusting the location by several hundred feet and will not have a 

significant adverse impact on the operation plan for the system. Another approach is to install movable -

point or spring frogs that eliminate the gaps that occur when standard railbound frogs are used. These 

special frogs have been shown to significantly reduce vibration levels near crossovers, and they are often 

specified because of their longer life span under repetitive high-speed conditions.

Vehicle Suspension

The ideal rail vehicle, with respect to minimizing ground-borne vibration, should have a low unsprung 

weight, a soft primary suspension, a minimum of metal-to-metal contact between moving parts of the 

truck, and smooth wheels that are perfectly round. A thorough dynamic analysis, including the expected 

track parameters, should be part of the specifications for any new high-speed trainset.

Special Track Support Systems

When the vibration assessment indicates that vibration levels will be excessive, it is usually the track 

support system that is modified to reduce the vibration levels. Floating slabs, resiliently supported ties, 

high resilience fasteners, and ballast mats all have been used to reduce the levels of ground-borne 

vibration. To be effective, these measures must be optimized for the frequency spectrum of the vibration. 

These measures have been used successfully on urban transit subway projects, but applications on atgrade and elevated track are rare because: vibration problems are less common for at-grade and elevated 

track; cost of the vibration control measures is a higher percentage of the construction costs of at-grade 

and elevated track; and exposure to outdoor weather conditions requires special drainage designs.

The major vibration control measures for track support are discussed below:

• Resilient Fasteners: Resilient fasteners are used to fasten rails to concrete track slabs. Standard 

resilient fasteners are very stiff in the vertical direction, usually in the range of 200,000 lb/in., 

although they do provide some vibration reduction. On urban transit systems, special fasteners with 

vertical stiffness in the range of 40,000 to 75,000 lb/in. have reduced vibration by as much as 5 to 10 

dB at frequencies above 30 to 40 Hz. 

• Ballast Mats: A ballast mat consists of a rubber or other type of elastomer pad that is placed under 

the ballast. The mat generally must be placed on a thick concrete or asphalt pad to be effective. It 

will not be as effective if placed directly on the soil or the sub-ballast. Consequently, most ballast 
Chapter 9: Detailed Vibration Assessment 9-21

mat applications are in tunnels or bridges. Ballast mats can provide 10 to 15 dB attenuation at 

frequencies above 25 to 30 Hz. An installation of ballast mat in a tunnel in France near Vouvray in 

TGV’s Atlantique line prevents vibrations from affecting storage and ageing of wines in a nearby 

wine cave. Ballast mats are often a good retrofit measure for existing tie -and-ballast track where 

there are vibration problems.

• Resiliently Supported Ties: A resiliently supported tie system, like the one used in the Channel 

Tunnel between England and France, consists of concrete ties supported by rubber pads. The rails are 

fastened directly to the concrete ties using standard rail clips. Some measurement data suggest that 

resiliently supported ties may reduce low-frequency vibration in the 15 to 40 Hz range, which would 

make them particularly appropriate for rail systems with vibration problems in the 20 to 30 Hz range. 

The frequency range over which this type of track support system can affect levels of ground-borne 

vibration depends on the pad stiffness and the interaction between the pads, ties, and rails.

• Floating Slabs: Floating slabs can be very effective at controlling ground-borne vibration and noise. 

They basically consist of a concrete slab supported on resilient elements, usually rubber or a similar 

elastomer. A variant that was first used in Toronto and is generally referred to as the double tie 

system, consists of 5-foot slabs with four or more rubber pads under each slab. Floating slabs are 

effective at frequencie s greater than their single -degree-of-freedom vertical resonance frequency. 

The floating slabs used in the Washington DC, Atlanta, and Boston transit systems were all designed 

to have a vertical resonance in the 14 to 17 Hz range. A special London Transport floating slab that is 

under the Barbican Redevelopment uses a very heavy design with a resonance frequency in the 5 to 

10 Hz frequency range.51 The primary disadvantage of floating slabs is that they tend to be the most 

expensive of the track-related vibration control treatments.

• Other Treatments: Changing any feature of the track support system can change the levels of groundborne vibration. Approaches such as using heavier rail, thicker ballast, heavier ties, or resilient 

elements beneath the tracks can be expected to reduce the vibration levels. There also is some 

indication that vibration levels are lower with wood ties compared to concrete ties. However, there is 

little confirmation that any of these approaches will make a significant change in the vibration levels. 

This is unfortunate since modifications to the ballast, rails, or ties are virtually the only options for 

typical track systems (at-grade, ballast-and-tie) without resorting to a different type of track support 

system or widening the right-of-way to provide a buffer zone.

Building Modifications

In some circumstances, it is practical to modify an affected building to reduce the vibration levels. 

Vibration isolation of buildings basically consists of supporting the building foundation on elastomer pads 

similar to bridge bearing pads. Vibration isolation is seldom an option for existing buildings. However, 

building vibration isolation can be particularly important for shared-use facilities such as office space 

 

51P. Grootenhuis, "Floating Track Slab Isolation for Railways," Journal of Sound and Vibration, 51:3, pp 

443-448, 1977.
9-22 High-Speed Ground Transportation Noise and Vibration Impact Assessment

above a train station or terminal. When vibration-sensitive equipment such as electron microscopes will 

be affected by train vibration, specific modifications to the building structure may be the most costeffective method of controlling the impact. For example, the floor upon which the vibration-sensitive 

equipment is located could be stiffened and isolated from the remainder of the building.

Trenches

Use of trenches to control ground-borne vibration is analogous to controlling airborne noise with sound 

barriers. Although this approach has not received much attention in the U.S., a trench can be a practical 

method for controlling vibration from at-grade track. A rule -of-thumb given by Richert and Hall52 is that 

if the trench is located close to the source, the trench bottom must be at least 0.6 times the Rayleigh 

wavelength below the vibration source. For most soils, Rayleigh waves travel at around 600 ft/sec, which 

means that the wavelength at 30 Hz is 20 feet. This means that the trench would have to be 

approximately 12 feet deep to be effective at 30 Hz. 

A trench can be an effective vibration barrier if it changes the propagation characteristics of the soil. It 

can be either open or solid. The Toronto Transit Commission did a test with a trench filled with 

Styrofoam to keep it open. They reported successful performance over a period of at least one year.53 

Solid barriers can be constructed with sheet piling, rows of drilled shafts filled with either concrete or a 

mixture of soil and lime,54 or concrete poured into a trench.

Operational Changes

The most obvious operational change is to reduce the vehicle speed. Reducing the train speed by a factor 

of two will reduce vibration levels approximately 6 dB. Other operational changes that can be effective in 

special cases are:

• Use the equipment that generates the lowest vibration levels during the nighttime hours when people 

are most sensitive to vibration and noise.

• Adjust nighttime schedules to minimize train movements during the most sensitive hours.

While there are tangible benefits from reducing speed and limiting operations during the most sensitive 

time periods, these measures may not be practical from the standpoint of trip time and service frequency 

requirements. Furthermore, vibration reduction achieved through operating restrictions requires 

continuous monitoring and will be negated if the signal system does not enforce compliance with the 

speed restriction.

 

52F. E. Richert and J. R. Hall, Vibrations of Soils and Foundations, Prentice-Hall, Inc., Englewood Cliffs, 

NJ, 1970.

53S. T. Lawrence, "TTC-LRT Trackbed Studies, Ground-borne Vibration Testing, Measurement and 

Evaluation Program," American Public Transit Association Rapid Transit Conference, San Francisco, CA, 1980.

54"The Lime Column Method,” Report No. 31, Swedish Geotechnical Institute, Linkoping, Sweden, 1994.
Chapter 9: Detailed Vibration Assessment 9-23

Buffer Zones

Expanding the rail right-of-way sometimes will be the most economical method of controlling the 

vibration impact. A similar approach is to negotiate a vibration easement from the affected property 

owners.
9-24 High-Speed Ground Transportation Noise and Vibration Impact Assessment
Chapter 10: Noise and Vibration During Construction 10-1

CHAPTER 10 - NOISE AND VIBRATION DURING CONSTRUCTION

This chapter discusses the procedures for assessing the temporary noise and vibration impacts associated 

with the construction of a new high-speed rail facility. Methods for estimating noise and vibration levels 

from construction equipment using tabulated source levels, as well as procedures for assessing and 

mitigating potential noise and vibration impacts are provided. While both construction noise and 

vibration are included in this chapter, there is generally no overlap between them in the methodology and 

they are covered in separate sections.

Construction often generates community noise/vibration complaints, despite the limited time frame over 

which it takes place. Complaints typically arise when construction efforts interfere with people's 

activities, especially when the community has insufficient information about the extent or duration of the 

construction. Misunderstandings can occur when the contractor is considered insensitive by the 

community, even though the contractor believes the construction activities are in compliance with local 

ordinances. This situation underscores the need for early identification and assessment of potential 

problem areas. An assessment of the potential for complaints can be made by following procedures 

outlined in this chapter. That assessment can aid contractors in making bids by allowing changes in 

construction approach and by including mitigation costs before the construction plans are finalized. 

Publication of an assessment, including a description of the construction noise and vibration environment, 

can lead to greater understanding and tolerance in the community. 

Control of construction noise and vibration occurs in three areas:

• Assessment: The environmental impact assessment identifies the potential problem areas during the 

construction phase of a project and the environmental assessment document informs the public of the 

project's construction effects. This information is important for new major infrastructure projects 

where heavy construction can take place over a lengthy period of time. The procedure for performing 

a noise assessment is discussed in Section 10.1 and for vibration assessment is discussed in Section 

10.2.

• Construction specifications: Most large construction projects incorporate noise specifications on 

construction equipment, but sometimes they must include additional measures to minimize 

community complaints. Special mitigation measures can be written into the construction documents 

where they are identified as necessary by the environmental impact assessment. The documents 
10-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

should include realistic specifications that lessen community annoyance without unreasonably 

constraining the contractors. Typical noise limits on equipment are included in Table 10-1.

• Compliance verification: Provide clear direction to field inspectors on conducting and reporting 

measurements for compliance with noise and vibration specifications in sensitive areas. 

10.1 CONSTRUCTION NOISE

The noise levels created by operating construction equipment can vary greatly and depend on factors such 

as the type of equipment, the specific model, the operation being performed, and the condition of the 

equipment. The equivalent sound level (Leq) of the construction activity also depends on the fraction of 

time that the equipment is operated over the time period of construction. This section provides 

information on typical levels generated by various construction equipment and provides guidance on 

assessment of noise from construction activities related to rail facilities. The level of noise analysis 

should be commensurate with the type and scale of the project and with the presence of noise-sensitive 

land uses in the construction zone.

10.1.1 Noise from Typical Construction Equipment and Operations

The dominant source of noise from most construction equipment is the engine, usually a diesel, without 

sufficient muffling. In a few cases, such as impact pile driving or pavement breaking, noise generated by 

the action of the machinery dominates. 

For purposes of noise assessment, construction equipment can be considered to operate in two modes, 

stationary and mobile. Stationary equipment operates in one location for one or more days at a time, with 

either a fixed-power operation (pumps, generators, compressors) or a variable noise operation (pile 

drivers, pavement breakers). Noise is assumed to emanate from the point of operation. Mobile 

equipment moves around the construction site with power applied in cyclic fashion (bulldozers, loaders), 

or to and from the site (trucks). The movement around the site is handled in the construction noise 

prediction procedure discussed later in this chapter. Variation in power imposes additional complexity in 

characterizing the noise source level from a piece of equipment. This variation is handled by describing 

the noise at a reference distance from the equipment operating at full power and adjusting it based on the 

duty cycle of the activity to determine the Leq of the operation. Standardized procedures for measuring 

the exterior noise levels for the certification of mobile and stationary construction equipment have been 

developed by the Society of Automotive Engineers.55,56 Typical noise levels generated by representative 

pieces of equipment are listed in Table 10-1. These levels are based on EPA and Department of 

 

55Society of Automotive Engineers, "Exterior Sound Level Measurement Procedure for Powered Mobile 

Construction Equipment," SAE Recommended Practice J88a, 1976.

56Society of Automotive Engineers, "Sound Levels for Engine Powered Equipment," SAE Standard J952b, 

1976.
Chapter 10: Noise and Vibration During Construction 10-3

Transportation Reports,57,58,59 measured data from railroad construction equipment, and other measured 

data.

Construction activities are characterized by variations in the power expended by equipment, with 

resulting variation in noise levels over time. Variation in power is expressed in terms of the "usage 

factor" of the equipment, the percentage of time during the workday that the equipment operates at full 

power. Time-varying noise levels are converted to a single number (Leq) for each piece of equipment 

during the operation. Besides having daily variations in activities, major construction projects are 

accomplished in several different phases. Each phase has a specific equipment mix, depending on the 

work to be accomplished during that phase. 

Each phase also has its own noise characteristics; some will have higher continuous noise levels than 

others, and some have high-impact noise levels. The purpose of the assessment is to determine not only 

the levels, but also the duration, of the noise. The Leq of each phase is determined by combining the Leq

contributions from each piece of equipment used in that phase. The impact and the consequent noise 

mitigation approaches depend on the criteria to be used in assessing impact, as discussed in the next 

section. 

10.1.2 Construction Noise Assessment

The level of detail in a construction noise assessment depends on the scale and type of project and the 

stage of environmental review process. Where the project is a major undertaking (the construction 

duration is expected to last for more than several months, noisy equipment will be involved, and/or the 

construction is expected to take place near a noise-sensitive site), then construction noise impacts may be 

determined in considerable detail, as described in this section. For other projects, the assessment may 

simply be a description of the equipment to be used, the duration of construction, and any mitigation 

requirements that will be placed on particularly noisy operations. 

 

57U.S. Environmental Protection Agency, "Noise from Construction Equipment and Operations, Building 

Equipment and Home Appliances," NTID300.1, December 31, 1971.

58U.S. Department of Transportation, "Final Environmental Impact Statement, 4(f) Statement; Replacement 

of Shaw's Cove Bridge and Approaches," FRA-RNC-EIS-80-02-F, September 16, 1981.

59William R. Fuller and Ron Brown, "Analysis and Abatement of Highway Construction Noise," EPA 

550/9-81-314-A, U.S. Environmental Protection Agency, Office of Noise Abatement and Control and U.S. 

Department of Transportation, Federal Highway Administration, June 1981.
10-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

A construction noise assessment for a major project is 

performed by comparing the predicted noise levels with 

criteria established for that type of proje ct. The 

approach requires an appropriate descriptor, a 

standardized prediction method, and a set of recognized 

criteria for assessing the impact. 

The descriptor used for construction noise is the Leq. 

This unit is appropriate for the following reasons:

• It can be used to describe the noise level from 

operation of each piece of equipment separately and 

is easily combined to represent the noise level from 

all equipment operating during a given period.

• It can be used to describe the noise level during an 

entire phase.

• It can be used to describe the average noise over all 

phases of the construction.

The recommended method for predicting construction 

noise impact for major urban transit projects is similar to 

that suggested by the Federal Highway 

Administration (FHWA).60 The FHWA prediction 

method is used to estimate the construction noise levels 

associated with the construction of a highway, but it can 

be used for any transportation project. The method 

requires:

1. An emission model to determine the noise 

generated by the equipment at a reference 

distance.

2. A propagation model that shows how the noise 

level will vary with distance.

3. A way of summing the noise of each piece of 

equipment at locations of noise sensitivity.

The first two components of the model are related by the following equation:

 

60J. A. Reagan and C. A. Grant, "Special Report - Highway Construction Noise: Measurement, Prediction 

and Mitigation," U.S. Department of Transportation, Federal Highway Administration, 1977.

Table 10-1 Construction Equipment Noise 

Emission Levels

Equipment Typical Noise Level (dBA)

50 ft from Source

Air Compressor 81

Backhoe 80

Ballast Equalizer 82

Ballast Tamper 83

Compactor 82

Concrete Mixer 85

Concrete Pump 82

Concrete Vibrator 76

Crane, Derrick 88

Crane, Mobile 83

Dozer 85

Generator 81

Grader 85

Impact Wrench 85

Jack Hammer 88

Loader 85

Paver 89

Pile Driver (Impact) 101

Pile Driver (Sonic) 96

Pneumatic Tool 85

Pump 76

Rail Saw 90

Rock Drill 98

Roller 74

Saw 76

Scarifier 83

Scraper 89

Shovel 82

Spike Driver 77

Tie Cutter 84

Tie Handler 80

Tie Inserter 85

Truck 88
Chapter 10: Noise and Vibration During Construction 10-5

where:

Leq(equip) = Leq at a receiver resulting from the operation of a single piece of equipment over a 

specified time period,

E.L. = noise emission level of the particular piece of equipment at the reference distance of 

50 feet (taken from Table 10-1),

G = constant that accounts for topography and ground effects (taken from Chapter 6, 

Figure 6-5),

D = distance from the receiver to the piece of equipment, and 

U.F. = usage factor that accounts for the fraction of time that the equipment is in use over 

the specified time period.

The combination of noise from several pieces of equipment operating during the same time period is 

obtained from decibel addition of the Leq of each single piece of equipment calculated using this equation.

Major Construction Projects

The assessment of a major construction project can be as detailed as necessary to characterize the 

construction noise by specifying the various quantities in the equation. For projects in an early 

assessment stage, when the equipment roster and schedule are undefined, only a rough estimate of 

construction noise levels is practical.

The following assumptions are adequate for a General Assessment of each phase of construction:

Step 1. Noise Source Level. Full power operation for a time period of one hour is assumed because 

most construction equipment operates continuously for periods of one hour or more at some 

point in the construction period. Therefore, U.F. = 1, and 10 log(U.F.) = 0. The emission 

level at 50 feet, E.L., is taken from Table 10-1. The predictions include only the two noisiest 

pieces of equipment expected to be used in each construction phase.

Step 2. Noise Propagation. Free field conditions are assumed and ground effects are ignored. 

Consequently, G = 0. All pieces of equipment are assumed to operate at the center of the 

project, or centerline, in the case of a guideway or highway construction project.

A more detailed analysis can be used if warranted, such as when a known noise-sensitive site is adjacent 

to a construction project or where contractors are faced with stringent local ordinances or specifications as 

a result of public concern. In such instances, the assessment sequence includes:

Step 1. Duration of the Construction. Long-term construction project noise impact is based on a 

30-day average Ldn, the times of day of construction activity (nighttime noise is penalized by 

10 dB in residential areas), and the percentage of time the equipment is to be used during a 

L equip E L U F

D

G

D

eq ( ) = . .+ log ( . .) − log log 









 −











10 20 

50

10

50
10-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment

period of time that will affect U.F. For example, an 8-hour Leq is determined by making 

U.F. the percentage of time each individual piece of equipment operates under full power in 

that period. Similarly, the 30-day average Ldn is determined from the U.F. expressed by the 

percentage of time the equipment is used during the daytime hours (7 a.m. to 10 p.m.) and 

nighttime (10 p.m. to 7 a.m.), separately over a 30-day period. However, to account for 

increased sensitivity to nighttime noise, the nighttime percentage is multiplied by 10 before 

performing the computation.

Step 2. Site topography, natural and constructed barriers, and ground effects. These features 

will change the factor G. Use Figure 5-3 to calculate G.

Step 3. Refinement of Emission Level. Measure or certify the emission level of each piece of 

equipment according to standardized procedures.61,62 This measurement will refine E.L.

Step 4. Location of Equipment. Determine the location of each piece of equipment while it is 

working. The distance factor D is therefore specified more exactly.

Step 5. Total Noise Source Level. Include all pieces of equipment in the computation of the 8-hour 

Leq and the 30-day average Ldn. The total noise levels are determined using Table 5-5 

(Chapter 5).

Minor Construction Projects

Most minor projects need no assessment of construction noise. However, when a construction project 

over a short period of time occurs in a noise-sensitive area, a qualitative treatment is appropriate. 

Community relations will be important in this case; early information disseminated to the public about the 

kinds of equipment, expected noise levels, and durations will help to forewarn potentially affected 

neighbors about the temporary inconvenience. Helpful information would include a general description 

of the variation of noise levels during a typical construction day. The General Assessment method 

described earlier in this section will be sufficient to provide the estimated noise levels. There is no need 

for a full assessment since the criteria suggested in the following section are not applicable in these cases.

Criteria

No standardized criteria have been developed for assessing construction noise impact. Consequently, 

criteria must be developed on a project-specific basis unless local ordinances apply. Generally, local 

noise ordinances are not very useful in evaluating construction noise. They usually relate to nuisance and 

hours of allowed activity and sometimes specify limits in terms of maximum levels, but they are generally 

not practical for assessing the impact of a construction project. Project construction noise criteria should 

take into account the existing noise environment, the absolute noise levels during construction activities, 

the duration of the construction, and the adjacent land use. While it is not the purpose of this manual to 

 

61Society of Automotive Engineers, "Exterior Sound Level Measurement Procedure for Powered Mobile 

Construction Equipment," SAE Recommended Practice J88a, 1976.

62Society of Automotive Engineers, "Sound Levels for Engine Powered Equipment," SAE Standard J952b, 

1976.
Chapter 10: Noise and Vibration During Construction 10-7

specify standardized criteria for construction noise impact, the following guidelines can be used as criteria 

for assessment. They are deliberately conservative because the related assessment method tends to overpredict noise levels. If these criteria are exceeded, the project is likely to face adverse community 

reaction and steps to mitigate the impact should be evaluated and implemented as necessary. 

General Assessment: Identify land uses in the vicinity of the construction project according to 

residential, commercial, and industrial land use activities. Estimate the combined noise level in 

one hour from the two noisiest pieces of equipment, assuming they both operate at the same time. 

Then identify locations where the level exceeds the levels specified in Table 10-2:

Table 10-2 General Assessment Criteria for Construction noise

One-hour Leq (dBA) Land Use

Day Night

Residential 90 80

Commercial 100 100

Industrial 100 100

Detailed Assessment: Predict the noise level in terms of 8-hour Leq and 30-day averaged Ldn and 

compare to levels specified in Table 10-3:

Table 10-3 Detaile d Assessment Criteria for Construction Noise

8-hour Leq (dBA) Ldn (dBA) Land Use

Day Night 30-day Average

Residential 80 70 75(a)

Commercial 85 85 80(b)

Industrial 90 90 85(b)

(a) In urban areas with very high ambient noise levels (Ldn > 65 dB), Ldn from 

construction operations should not exceed existing ambient + 10 dB.

(b) Twenty-four-hour Leq, not Ldn.

10.1.3 Mitigation of Construction Noise

After using the approach presented in Section 10.1.2 to locate potential impacts from construction noise, 

the next step is to identify appropriate control measures. The design engineer can implement noise 

control through layout of the construction site, planning the order of operations, or by choosing less noisy 

operations. These categories of noise control approaches, with examples of mitigation measures, are 

given below:

1. Design considerations and project layout:

• Construct noise barriers, such as temporary walls or piles of excavated material, between noisy 

activities and noise-sensitive receivers.

• Route truck traffic away from residential streets, if possible. Select streets with the fewest homes, if 

no alternatives are available.
10-8 High-Speed Ground Transportation Noise and Vibration Impact Assessment

• Site equipment on the construction lot as far away from noise-sensitive sites as possible.

• Construct walled enclosures around especially noisy activities or around clusters of noisy equipment. 

For example, shields can be used around pavement breakers and loaded vinyl curtains can be draped 

under elevated structures.

2. Sequence of operations:

• Combine noisy operations so they occur in the same time period. The total noise level produced will 

not be significantly greater than the level produced if the operations were performed separately.

• Avoid nighttime activities. Sensitivity to noise increases during the nighttime hours in residential 

neighborhoods.

3. Alternative construction methods:

• Avoid impact pile driving where possible in noise-sensitive areas. Drilled piles or the use of a sonic 

or vibratory pile driver are quieter alternatives where the geological conditions permit their use.

• Use specially quieted equipment, such as quieted and enclosed air compressors, and mufflers on all 

engines.

• Select quieter demolition methods, where possible. For example, sawing bridge decks into sections 

that can be loaded onto trucks results in lower cumulative noise levels than impact demolition by 

pavement breakers.

• The environmental assessment should include a description of one or more mitigation approach for 

each affected location.

10.2 CONSTRUCTION VIBRATION

Construction activity can result in varying degrees of ground vibration, depending on the equipment and 

methods employed. Operation of construction equipment causes ground vibrations, which spread through 

the ground and diminish in strength with distance. Buildings founded on the soil in the vicinity of the 

construction site respond to these vibrations with varying results, ranging from no perceptible effects at 

the lowest levels, low rumbling sounds and perceptible vibrations at moderate levels, and slight damage at

the highest levels. Ground vibrations from construction activities very rarely reach the levels that can 

damage structures, but they can achieve the audible and perceptible ranges in buildings very close to the 

site. A possible exception is construction taking place near old, fragile buildings of historical significance 

where special care must be taken to avoid damage. The construction vibration criteria should include 

special consideration for fragile historical buildings. The construction activities that typically generate 

the most severe vibrations are blasting and impact pile driving. 

10.2.1 Vibration Source Levels from Construction Equipment

Various types of construction equipment have been measured operating under a wide variety of 

construction activities, with an average of source levels reported in terms of velocity levels as shown in 
Chapter 10: Noise and Vibration During Construction 10-9

Table 10-4. Although Table 10-4 gives one level for each piece of equipment, the reported ground 

vibration levels from construction activities vary considerably. The data provide a reasonable estimate 

for a wide range of soil conditions.

Since the primary concern with regard to construction vibration is building damage, construction 

vibration is generally assessed in terms of peak particle velocity (PPV), as defined in Chapter 6. Peak 

particle velocity is typically a factor of 2 to 6 times greater than root mean square (rms) vibration 

velocity; a factor of 4 has been used to calculate the approximate rms vibration velocity levels indicated 

in Table 10-4.

10.2.2 Construction Vibration Assessment 

Construction vibration should be assessed in cases where there is a significant potential for impact from 

construction activities. Such activities include blasting, pile driving, demolition, and drilling or 

excavation in close proximity to sensitive structures. The recommended procedure for estimating 

vibration impact from construction activities is as follows:

Step 1. Vibration Source Levels. Select the equipment and associated vibration source levels at the 

reference distance of 25 feet as shown in Table 10-4.

Step 2. Vibration Propagation. Make the propagation adjustment according to the following formula, 

based on point sources with normal propagation conditions:

PPV PPV

D

equip = ref ×













2 5 1.5

where: PPVequip =the peak particle velocity in in/sec of the equipment adjusted for distance

PPVref =the reference vibration level in in/sec at 25 feet from Table 10-4, and

D =the distance from the equipment to the receiver.

Step 3. Damage Criterion. Apply the PPV vibration damage threshold criterion of 0.50 in/sec 

(approximately 102 VdB) for fragile buildings, or 0.12 in/sec (approximately 90 VdB) for 

extremely fragile historic buildings.63

Step 4. Annoyance Criterion. For considerations of annoyance or interference with vibration-sensitive 

activities, estimate the RMS vibration level Lv at any distance D from the following equation:

















= −

25

( ) (25 ft) 30 log DL v D L v

Apply the vibration impact criteria in Chapter 7 for vibration-sensitive sites.

 

63Swiss Consultants for Road Construction Association, "Effects of Vibration on Facilities," VSS-SN640-

312a, Zurich, Switzerland, April 1992.
10-10 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Table 10-4 Vibration Source Levels for Construction Equipment

(From measured data.64,65,66,67)

Equipment PPV at 25 ft 

(in/sec)

Approximate

Lv

†

 at 25 ft

upper range 1.518 112 Pile Driver (impact) typical 0.644 104

upper range 0.734 105 Pile Driver (vibratory) typical 0.170 93

Clam shovel drop (slurry wall) 0.202 94

in soil 0.008 66 Hydromill (slurry wall) in rock 0.017 75

Large bulldozer 0.089 87

Caisson drilling 0.089 87

Loaded trucks 0.076 86

Jackhammer 0.035 79

Small bulldozer 0.003 58

† RMS velocity in decibels (VdB) re 1 μinch/second

10.2.3 Construction Vibration Mitigation

After using the procedure described in Section 10.2.2 to locate potential impacts (or damage) from 

construction vibrations, the next step is to identify control measures. Similar to construction noise, 

mitigation of construction vibration requires consideration of equipment location and processes, as 

follows:

1. Design considerations and project layout:

• Route heavily loaded trucks away from residential streets, if possible. Select streets with fewest 

homes, if no alternatives are available.

• Operate earthmoving equipment on the construction lot as far away from vibration-sensitive sites as 

possible.

 

64D.J. Martin, "Ground Vibrations from Impact Pile Driving during Road Construction," Supplementary 

Report 544, United Kingdom Department of the Environment, Department of Transport, Transport and Road 

Research Laboratory, 1980.

65J.F. Wiss, "Vibrations During Construction Operations," Journal of Construction Division, Proc. 

American Society of Civil Engineers, 100, No. CO3, pp. 239 - 246, September 1974.

66J.F. Wiss, "Damage Effects of Pile Driving Vibrations," Highway Research Record, No. 155, Highway 

Research Board, 1967.

67D.A. Towers, "Ground-borne Vibration from Slurry Wall Trench Excavation for the Central 

Artery/Tunnel Project Using Hydromill Technology," Proceedings of Inter-Noise 95, Newport Beach, CA, July 

1995, pp. 227 - 232.
Chapter 10: Noise and Vibration During Construction 10-11

2. Sequence of operations:

• Phase demolition, earthmoving, and ground-impacting operations so as not to occur in the same time 

period. Unlike noise, the total vibration level produced could be significantly less when each 

vibration source operates separately.

• Avoid nighttime activities. People are more aware of vibration in their homes during the nighttime 

hours.

3. Alternative construction methods:

• Avoid impact pile driving where possible in vibration-sensitive areas. Drilled piles or the use of a 

sonic or vibratory pile driver causes lower vibration levels where the geological conditions permit 

their use. 

• Select demolition methods not involving impact, where possible. For example, sawing bridge decks 

into sections that can be loaded onto trucks results in lower vibration levels than impact demolition by 

pavement breakers, and milling generates lower vibration levels than excavation using clam shell or 

chisel drops.

• Avoid vibratory rollers and packers near sensitive areas.

10.2.4 Special Note on Pile Driving

Pile driving is potentially the greatest source of vibration associated with equipment used during 

construction of a project. The source levels in Table 10-4 indicate that vibratory pile drivers may provide 

substantial reduction of vibration levels. However, the additional vibration effects of vibratory pile 

drivers may limit their use in sensitive locations. A vibratory pile driver operates by continuously 

shaking the pile at a fixed frequency, literally vibrating it into the ground. However, continuous operation 

at a fixed frequency may be more noticeable to nearby residents, even at lower vibration levels. 

Furthermore, the steady-state excitation of the ground may increase resonance response of building 

components. Resonant response may be unacceptable in cases of fragile historical buildings or vibrationsensitive manufacturing processes. Impact pile drivers, on the other hand, produce a high vibration level 

for a short time (0.2 seconds) with sufficient time between impacts to allow any resonant response to 

decay. 
10-12 High-Speed Ground Transportation Noise and Vibration Impact Assessment
Chapter 11: Documentation of Noise and Vibration Assessment 11-1

CHAPTER 11 - DOCUMENTATION OF NOISE AND VIBRATION ASSESSMENT

To be effective, noise and vibration analyses must be presented to the public in a clear, comprehensive 

manner. The mass of technical data and information necessary to withstand scrutiny in the environmental 

review process must be documented in a manner that remains intelligible to the public. Justification for 

all assumptions used in the analysis, such as selection of representative measurement sites and all baseline 

conditions, must be presented for review. For large-scale projects, the environmental document normally 

contains a condensation of essential information to maintain a reasonable size. For these projects, 

separate technical reports are usually prepared as supplements to the Environmental Impact Statement 

(EIS) or Environmental Assessment (EA). For smaller projects, or ones with minimal noise or vibration 

impact, all the technical information may be presented in the environmental document itself. This chapter 

gives guidance on how the necessary noise and vibration information should be incorporated in the 

project's environmental documentation.

11.1 THE TECHNICAL REPORT ON NOISE AND VIBRATION

A separate technical report is often prepared as a supplement to the environmental document (EIS or EA). 

A technical report is appropriate when all of the data cannot be placed in the environmental document. 

The details of the analysis are important for establishing the basis for the assessment. Consequently, all 

the details in the technical report should be contained in a well-organized format for easy access to the 

information. While the technical report is not intended to be a primer on the subject, the technical data 

and descriptions should be presented in a manner that can be understood by the general public. All the 

necessary background information should be included in the technical report, including tables, maps, 

charts, drawings, and references that may be too detailed for the environmental document, but that are 

important in helping to draw conclusions about the project's noise and vibration impacts and mitigation 

options.

11.1.1 Organization of Technical Report

The technical report on noise and vibration should contain the following major subject headings, along 

with the key information content described below. If both noise and vibration have been analyzed, it is 
11-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

generally preferable to separate the noise and vibration sections; as shown in this manual, the approaches 

to the two topics are quite different.

Overview– This section contains a brief description of the project and an overview of the noise/vibration 

concerns. It sets forth the initial considerations in framing the scope of the study.

Inventory of Noise and Vibration-Sensitive Sites – The approach for selecting noise/vibrationsensitive sites should be described in sufficient detail to demonstrate completeness. Sites and site 

descriptions are to be included.

Measurements of Existing Noise and Vibration Conditions – The basis for selecting measurement sites 

should be documented, along with tables of sites coordinated with maps showing locations of sites. 

If the measurement data are used to estimate existing conditions at other locations, the rationale 

and the method should be included. Measurement procedures should be fully described. Tables of 

measurement instruments should include manufacturer, type, serial number, and date of most 

recent calibration by authorized testing laboratory. Measurement periods, including time of day 

and length of time at each site, should be shown to demonstrate adequate representation of the 

ambient conditions. The measurement data should be presented in well-organized form in tables 

and figures. A summary and interpretation of measured data should be included.

Special Measurements Related to the Project – Some projects may require specialized measurements at 

sensitive sites, such as outdoor-to-indoor noise level reduction of homes or transmission of 

vibrations into concert halls and recording studios. Other projects may need special source level 

characterization. Full descriptions of the measurements and the results should be included.

Predictions of Noise/Vibration from the Project – The prediction model used for estimating future 

project conditions should be fully described and referenced. Any changes or extensions to the 

models recommended in this manual should be fully described so that the validity of the 

adjustments can be confirmed. Specific data used as input to the models should be listed. 

Computed levels should be tabulated and illustrated by contours, cross-sections, or shaded 

mapping. It is important to illustrate noise and vibration impacts with base maps at a scale with 

enough detail to provide location reference for the reader. 

Noise and Vibration Criteria – Impact criteria for the project should be fully described and referenced 

(refer to Chapters 3 and 8). In addition, any applicable local ordinances should be described. 

Tables specifying the criteria levels also should be included. If the project involves considerable 

construction, and a separate construction noise and vibration analysis will be included, then 

construction criteria should appear in a separate section with its own assessment.

Noise and Vibration Impact Assessment – The impact assessment should be described according to the 

procedures outlined in this manual. A resulting impact inventory should be presented for each 

alternative mode or alignment to enable ready comparison among alternatives. The inventory 

should be tabulated according to the different types of land uses affected. The results of the 

assessment may be presented both before and after mitigation.

Noise and Vibration Mitigation– The mitigation section of the report should begin with a summary of 

all treatments considered, even if some are not carried to final consideration. Final candidate 

mitigation treatments should be considered separately, with description of the features of the 
Chapter 11: Documentation of Noise and Vibration Assessment 11-3

treatment, costs, expected benefit in reducing impacts, locations where the benefit would be 

realized, and discussion of practicality of implementing alternative treatments. Enough 

information should be included to allow the project sponsor and FRA to reach decisions on 

mitigation prior to issuance of the final environmental document.

Construction Noise and Vibration Impacts – Criteria adopted for construction noise or vibration should 

be described, if appropriate. In accordance with Chapter 10, these may be adopted on a projectspecific basis. The method used for predicting construction noise or vibration should be described, 

along with inputs to the models, such as equipment roster by construction phase, equipment source 

levels, assumed usage factors, and other assumed site characteristics. The predicted levels should 

be shown for sensitive sites and short-term impacts should be identified. Feasible abatement 

methods should be discussed in enough detail such that construction contract documents could 

include mitigation measures.

References – Documentation is an important part of the validation of the technical report. References 

should be provided for all criteria, approaches and data used in the analyses, including other reports 

related to the project which may be relied on for information, e.g., geotechnical reports.

11.2 THE ENVIRONMENTAL DOCUMENT

The environmental document typically includes noise and vibration information in three places: a section 

of the chapter on the affected environment (existing conditions) and two sections in the chapter on 

environmental consequences (long-term and short-term impacts). The noise and vibration information 

presented in the environmental document is a summary of the comprehensive information from the 

technical report, with emphasis on presenting the salient points of the analysis in a format and style that 

affected property owners and other interested citizens can understand. Smaller projects may have all of 

the technical information contained within the environmental document; special care should be taken in 

summarizing technical details to convey the information adequately. 

The environmental document provides full disclosure of noise and vibration impacts, including 

identification of locations where impacts cannot be mitigated satisfactorily. An EIS describes significant 

impacts and tells what the federal agency intends to do about them. Issuing a Finding of No Significant 

Impact (FONSI) may depend on mitigation being included. The specific mitigation recommendation in 

the environmental document depends on the stage of project development and the stage of environmental 

review. For example, a Draft EIS may discuss different options to mitigate noise or vibration, deferring 

the final selection of measures to the Final EIS. It may be particularly important to present mitigation 

options at an early stage, especially if there is a benefit in receiving input from the public on the choices.

The final environmental document (Final EIS or FONSI) can take two approaches to describe any 

decisions on whether and/or how to mitigate. The document could describe the actual mitigation 

measures that will be employed, along with the reductions in noise or vibration expected to occur. In this 

case, the report should include language making it clear that the measures shall be implemented if the 

project is approved. However, in some cases, mitigation measures may still be under study in the 

environmental review and will not be selected until the final design stage. In such cases, the final 
11-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

environmental document should express a commitment to mitigate impacts that are verified during final 

design. Mitigation in these cases can be addressed in the form of a "performance standard" to be met by 

using one or more of the measures under study. 

11.2.1 Organization of Noise and Vibration Sections

Chapter on Affected Environment (Existing Conditions)

This chapter describes the pre-project setting, including the existing noise and vibration conditions, that 

will likely be affected by one or more of the alternatives. The primary function of this chapter is to 

establish the focus and baseline conditions for later chapters discussing environmental impacts. 

Consequently, this chapter is a good place to put basic information on noise and vibration descriptors and 

effects, as well as for describing the characteristics in the vicinity of the project. Again, it is preferable to 

separate the noise and vibration sections.

• Description of Noise and Vibration Descriptors, Effects and Typical Levels: Information from 

Chapters 2 and 7 of this manual can be used to provide a background for the discussions of 

noise/vibration levels and characteristics to follow. Illustrative material to guide the reader in 

understanding typical levels is helpful. 

• Criteria for Noise and Vibration Impact. Impact criteria for the project should be fully described 

and referenced (refer to Chapters 3 and 7). In addition, any applicable local ordinances should be 

described. Tables listing the criterion levels should be included.

• Inventory of Noise and Vibration-Sensitive Sites: The approach for selecting noise and vibrationsensitive sites should be described in sufficient detail to demonstrate completeness. Sites and site 

descriptions are to be included.

• Noise and Vibration Measurements: A summary of the site selection procedure should be 

included, along with tables of sites coordinated with maps showing locations of sites. The 

measurement approach should be summarized, with justification for the measurement procedures 

used. The measurement data should be presented in well-organized form in tables and figures. To 

save space, the results are often included with the table of sites described above. In some cases, 

measurements may be supplemented or replaced by collected data relevant to the noise and vibration 

characteristics of the area. For example, soils information for estimating ground-borne vibration 

propagation characteristics may be available from other projects in the area. Fundamental to this 

section are a summary and interpretation of how the collected data define the project setting. 

Chapter on Environmental Consequences.

The section on long-term impacts, the impacts due to operation of the project, should be organized 

according to the following order:

1. Overview of Approach. A summary of the assessment procedure for determining noise and 

vibration impacts is provided as a framework for the following sections.
Chapter 11: Documentation of Noise and Vibration Assessment 11-5

2. Estimated Noise and Vibration Levels. A general description of prediction models used to 

estimate project noise/vibration levels should be provided. Any distinguishing features unique to 

the project, such as source levels associated with various technologies, should be described. The 

results of the predictions for various alternatives should be described in general terms first, 

followed by a detailed accounting of predicted noise levels. This information should be 

supplemented with tables and illustrated by contours, cross-sections or shaded mapping. If 

contours are included in a technical report, then it is not necessary to repeat them here.

3. Impact Assessment. It is important to provide a description of locations where noise and vibration 

impact is expected to occur without implementation of mitigation measures, based on the predicted 

future levels, existing levels and the criteria for impact. Inventory tables of impacted land uses 

should be used to quantify the impacts for comparisons among alternatives. The comprehensive 

list of noise- and vibration-sensitive sites identified in the Affected Environment chapter should be 

included in this inventory table.

4. Noise and Vibration Mitigation. Perhaps the most significant difference between the technical 

report and the environmental document is in the area of mitigation. Whereas the technical report 

discusses options and may make recommendations, the environmental document provides the 

vehicle for reaching decisions on appropriate mitigation measures, with consideration given to 

environmental benefits, feasibility, and cost. This section should begin with a summary of all noise 

and vibration mitigation measures considered for the impacted locations. The specific measures 

selected for implementation should be fully described. However, for projects where technical 

details of the mitigation measures cannot be specified at the environmental assessment stage, a 

commitment is made to the level of abatement; the EIS must demonstrate that mitigation measures 

under consideration will achieve the necessary reduction. FRA strongly encourages noise and 

vibration abatement for projects where significant impacts are identified. Reasons for dismissing 

any abatement measures should also be clearly stated, especially if such non-implementation 

results in significant adverse effects. The expected benefits for each treatment in reducing impact 

should be given for each location. 

5. Unavoidable Adverse Environmental Effects. If it is projected that adverse noise and vibration 

impacts will result after all reasonable abatement measures have been incorporated, the impacts 

should be identified in this section.

Impacts During Construction

The environmental document may have a separate section on short-term impacts due to project 

construction, depending on the scale of the project. For a major project there may be a special section on 

construction noise and vibration impacts; this section should be organized according to the 

comprehensive outline described above. For projects with relatively minor effects, a briefer format 

should be used, with a section included in the chapter on Environmental Consequences.
11-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment
Appendix A: Background – Noise Concepts A-1

APPENDIX A - BACKGROUND – NOISE CONCEPTS

A.1 NOISE METRICS

Environmental noise generally derives from a conglomeration of distant noise sources. Such sources may 

include distant traffic, wind in trees, and distant industrial or farming activities, all part of our daily lives. 

These distant sources create a low-level "background noise" in which no particular individual source is 

identifiable. Background noise is often relatively constant from moment to moment, but varies slowly 

from hour to hour as natural forces change or as human activity follows its daily cycle. Superimposed on 

this low-level, slowly varying background noise is a succession of identifiable noisy events of relatively 

brief duration. These events may include single -vehicle passbys, aircraft flyovers, screeching of brakes, 

and other short-term events, all causing the noise level to fluctuate significantly from moment to moment.

It is possible to describe these fluctuating noises in the environment using single -number descriptors. To 

do this allows manageable measurements, computations, and impact assessment. The search for adequate 

single-number noise descriptors has encompassed hundreds of attitudinal surveys and laboratory 

experiments, plus decades of practical experience with many alternative descriptors.

A.1.1 A-weighted Level: The Basic Noise Unit

As discussed in Chapter 2, the basic noise unit for environmental noise is the A-weighted sound level. It 

describes the magnitude of noise at a receiver at any moment in time and is read directly from noisemeasuring equipment, with the "weighting switch" set on "A." Typical A-weighted sound levels from 

high-speed rail systems as well as other outdoor and indoor sources are shown in Figure 2-2.

Typical community A-weighted sound levels range from the 30s to the 90s, where 30 is very quiet and 

90 is very loud. A-weighted sound level measured in decibels is abbreviated "dBA," where the "dB" 

stands for decibels and refer to the general strength of the noise. The decibel is a unit that can be used to 

denote the ratio between any two quantities that are proportional to power. When used to describe sound 

level, the number of decibels is 10 times the logarithm (to the base 10) of the ratio (p2/pref

2

), where p is the 

sound pressure (in micropascals) and pref is a reference pressure (20 micropascals). The letter “A” 
A-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

indicates that the sound has been filtered to reduce the strength of very low and very high-frequency 

sounds, much as the human ear does. Without this A-weighting, noise-monitoring equipment would 

respond to events people cannot hear, events such as high-frequency dog whistles and low-frequency 

seismic disturbances. On the average, each A-weighted sound level increase of 10 decibels corresponds 

to an approximate doubling of subjective loudness.

A-weighted sound levels are adopted here as the basic noise unit because: (1) they can be easily 

measured, (2) they approximate the human ear's sensitivity to sounds of different frequencies, (3) they 

match attitudinal-survey tests of annoyance better than do other basic units, (4) they have been in use 

since the early 1930s, and (5) they are endorsed as the proper basic unit for environmental noise by nearly 

every agency concerned with community noise throughout the world.

This manual uses the following single -number descriptors for environmental noise measurements, 

computations, and assessment:

The A-weighted Sound Level, which describes a receiver's noise level at any moment in time.

The Maximum Level (Lmax) during a single noise event.

The Sound Exposure Level (SEL), which describes a receiver's cumulative noise exposure from a 

single noise event.

The Hourly Equivalent Sound Level (Leq(h)), which describes a receiver's cumulative noise 

exposure from all events over a one-hour period.

The Day-Night Sound Level (Ldn), which describes a receiver's cumulative noise exposure from all 

events over a full 24 hours, with events between 10 p.m. and 7 a.m. increased by 10 decibels to 

account for greater nighttime sensitivity to noise.

The following sections illustrate all of these noise descriptors, in turn, and describes their particular 

application in this manual. Graphic illustrations and mathematical definitions are provided to help the 

reader understand and see the interrelationships among descriptors.

A.1.2 Maximum Level (Lmax) During a Single Noise Event

As a train approaches, passes by, and then proceeds into the distance, the A-weighted sound level rises, 

reaches a maximum, and then fades into the background noise. The maximum A-weighted sound level 

reached during this passby is called the Maximum Level, abbreviated here as "Lmax." For noise 

compliance tests of transient sources, such as moving rail vehicles under controlled conditions with 

smooth wheel and rail conditions, Lmax is typically measured with the sound level meter's switch set on 

"fast," meaning that the sound level is averaged over a period of 0.125 seconds. Another use of Lmax

(fast), abbreviated Lmax,f, is for identifying defective components such as wheel flat spots in a passing 

train or an excessively noisy car in a long consist of freight cars. However, for tests of continuous or 

stationary sources, and for describing short-term noise events for the general assessment of noise impact, 

it is usually more appropriate to use the "slow" setting, where the sound level is averaged over a 1 second 

period. When set on "slow," sound level meters ignore some of the very-transient fluctuations, which are 
Appendix A: Background – Noise Concepts A-3

unimportant to people's overall assessment of the noise. Lmax (slow), abbreviated Lmax,s gives a better 

representation of sound energy of an event and is therefore more directly related to the sound exposure 

level (SEL) described in the next subsection.

Measurements reported as Lmax without designation of “fast” or “slow” meter response often become a 

source of confusion, which leads to errors in interpretation. Measurements of high-speed trains to obtain 

reference levels for this manual consistently showed Lmax,f to be 2 dB higher than Lmax,s. Therefore, in 

general, if it is important to document the sound level of a very short-term event, less than one second in 

duration, use the “fast” meter setting; otherwise, use “slow.” The manner in which the Lmax descriptor fits 

into the time history of environmental noise is shown in Figure A-1. 

A.1.3 SEL: The Cumulative Exposure from a Single Noise Event

The quantitative measure of the noise "dose" for single noise events is the Sound Exposure Level, 

abbreviated here as "SEL". The fact that SEL is a cumulative measure means that (1) louder events have 

higher SELs than quieter ones, and (2) events that last longer in time have higher SELs than shorter ones. 

People react to the duration of noise events, judging longer events to be more annoying than shorter ones, 

assuming equal maximum A-Levels. The Sound Exposure Level is computed as:

A more specific mathematical definition is:

where LA(t) represents the time-varying A-weighted sound level during an event. Time base is assumed 

to be one second.

• SEL is used in this manual as the measure of each single high-speed train event because unlike Lmax, 

• SEL increases with the duration of a noise event, which is important to people's reaction,

• SEL therefore allows a uniform assessment method for differing high-speed rail technologies, and

• SEL can be used to calculate the one-hour and 24-hour cumulative descriptors discussed below.

A.1.4 Hourly Equivalent Sound Level [Leq(h)]Error! Bookmark not defined.

The descriptor for cumulative one-hour exposure is the Hourly Equivalent Sound Level, abbreviated here 

as "Leq(h)." It is an hourly measure that accounts for the moment-to-moment fluctuations in A-weighted 

sound levels due to all sound sources during that hour, combined. Sound fluctuation is illustrated in the 

upper frame of Figure A-1 for a single noise event such as a train passing on nearby tracks. As the train 

approaches, passes by, and then proceeds into the distance, the A-weighted Sound Level rises, reaches a 

SEL =













10 log total sound energy

during the event

SEL dt

LAt

=









 −∞ 

∞

∫

10 10 10 log

( )
A-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

maximum, and then fades into the background noise. The area under the curve in this upper frame is the 

receiver's noise exposure over this five-minute period.

The center frame of Figure A-1 shows sound leve l fluctuations over a one-hour period that includes the 

five-minute period from the upper frame. The area under the curve represents the noise exposure for one 

hour. The Hourly Equivalent Sound Level is computed as:

or mathematically:

where the one-hour interval extends from t1 to t2, and T = t2 - t1 = 1 hour. The constant 35.6 is obtained 

from time normalization: one hour = 3600 seconds, and 10 log 3600 = 35.6.

Sound energy is totaled here over a full hour; thus, it accumulates from all noise events during that hour. 

Subtraction of 35.6 from the total sound energy during one hour in the first equation converts it into a 

time average, as does the 1/T factor shown in the second equation. In brief, if the actual fluctuating noise 

were replaced by a constant noise equal to this average value, the receiver would be exposed to the same 

total noise energy. This type of average value is "equivalent" in that sense to the actual fluctuating noise. 

A useful, alternative way of computing Leq due to a series of high speed rail noise events is:

or mathematically:

This equation concentrates on the cumulative contribution of individual noise events, and is the 

fundamental equation incorporated into Chapters 4 and 5. 

The bottom frame of Figure A-1 shows the sound level fluctuations over a full 24-hour period. It is 

discussed in Section A.1.5.

L hour eq( ) = log .











10 − 35 6 10

Total sound energy

during one hour

L hour

T

dt eq

t

t LA t

( ) log

( )

=











∫ 

10 110 10

10

1

2

Leq (hour) = log .













10 − 35 6 10

Energy Sum of

all SELs

L hour

T

eq

i

SELi

( ) = log

















10 ∑

1

10 10 10
Appendix A: Background – Noise Concepts A-5

Typical hourly Leq's, both for high-speed rail and non-high-speed rail sources, are shown in Figure A-2. 

These Leq's depend upon the number of events during the hour and also upon each event's duration, which 

is affected by speed. Doubling the number of events during the hour will increase the Leq by 3 decibels, 

as will doubling the duration of each individual event.

Figure A-1 Example A-Weighted Sound Level Time Histories
A-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Hourly Leq is adopted as the measure of cumulative noise impact for non-residential land uses (those not 

involving sleep) because: 

• Leq's correlate well with speech interference in conversation and on the telephone – as well as 

interruption of TV, radio, and music enjoyment,

• Leq's increase with the duration of events, which is important to people's reaction,

• Leq's take into account the number of events over the hour, which is also important to people's 

reaction, and

• Leq's are used by the Federal Highway Administration in assessing highway-traffic noise impact. 

Thus, this noise descriptor can be used to compare and contrast modal alternatives such as highway 

versus rail. Leq is computed for the loudest facility hour during noise-sensitive activity at each particular 

non-residential land use. 

A.1.5 Day-Night Sound Level (Ldn): The Cumulative 24-Hour Exposure from All Events

The descriptor for cumulative 24-hour exposure is the Day-Night Sound Level, abbreviated as "Ldn." It is 

a 24-hour measure that accounts for the moment-to-moment fluctuations in A-Levels due to all sound 

sources during 24 hours, combined. Such fluctuations are illustrated in the bottom frame of Figure A-1. 

The area under the curve represents the receiver's noise exposure over a full 24 hours. Some vehicle 

passbys occur at night in the figure, when the background noise is less. Mathematically, the Day-Night 

Level is computed as:

Figure A-2 Typical Hourly Leg’s

Ldn =













10 log10 − 49.4

Total sound energy

during 24 hours
Appendix A: Background – Noise Concepts A-7

where nighttime noise (10 p.m. to 7 a.m.) is increased by 10 decibels before totaling. The constant 49.4 is 

obtained from the time normalization: 24 hours = 86,400 seconds, and 10 log 86,400 = 49.4.

Sound energy is totaled over a full 24 hours; it accumulates from all noise events during that 24 hours. 

Subtraction of 49.4 from this 24-hour exposure converts it into a type of "average." If the actual 

fluctuating noise were replaced by a constant noise equal to this average value, the same total noise 

exposure would enter the receiver's ears.

An alternative way of computing Ldn from 24 hourly Leq's is:

where nighttime Leq's are increased by 10 decibels before totaling, as in the previous equation. 

This is expressed mathematically as:

where:

the 15-hour period from 7:00 am to 10:00 pm is defined as daytime (unweighted), and

the 9-hour period 10:00 pm to 7:00 am is defined as nighttime (with 10-decibel weighting).

Ldn due to a series of high-speed train events can also be computed as:

Use of this equation assumes that train noise dominates the 24-hour noise exposure. Here again, 

nighttime SELs are increased by 10 decibels before totaling. This last equation concentrates upon 

individual noise events, and is the equation incorporated into Chapters 4 and 5. 

Typical Ldn's, both for high-speed rail and conventional transit sources are shown in Figure A-3. As 

shown in the figure, typical Ldn's range from the 50s to the 70s – where 50 is a quiet 24-hour period and 

70 is an extremely noisy one. These Ldn's depend upon the number of events during day and night 

separately – and also upon each event's duration, which is affected by vehicle speed.

Ldn is adopted as the measure of cumulative noise impact for residential land uses (those involving sleep), 

because:

L

s

dn =













10 − 13 8 10 log .

Energy sum of

24 hourly Leq

Ldn

hour am

pm

hour pm

L am eq hour Leq hour

=

+





























= =

∑ ∑

+

10

10 10

24 10

7

10

10

7

10

10

10

log

( ) ( )

Ldn =













10 − 49 4 10 log .

Energy sum of

all SELs
A-8 High-Speed Ground Transportation Noise and Vibration Impact Assessment

ÿ Ldn correlates well with the results of attitudinal surveys of residential noise impact,

ÿ Ldn increases with the duration of transit events, which is important to people's reaction,

ÿ Ldn takes into account the number of transit events over the full 24 hours, which is also important to 

people's reaction,

ÿ Ldn takes into account the increased sensitivity to noise at night, when most people are asleep,

ÿ Ldn allows composite measurements to capture all sources of community noise combined,

ÿ Ldn allows quantitative comparison of transit noise with all other community noises,

ÿ Ldn is the designated metric of choice of other Federal agencies such as Federal Transit 

Administration (FTA), Department of Housing and Urban Development (HUD), Federal Aviation 

Administration (FAA), and Environmental Protection Agency (EPA), and

ÿ Ldn has wide international acceptance.

In terms of individual passbys, some characteristics of both the Leq and the Ldn are as follows:

When passby Lmax's increase: → Both Leq and Ldn increase,

When passby durations increase: → Both Leq and Ldn increase,

When the number of passbys increases: → Both Leq and Ldn increase,

When some operations shift to louder vehicles: → Both Leq and Ldn increase, and

When passbys shift from day to night: → Ldn increases.

All of these increases in Leq and Ldn correlate to increases in community annoyance.
Appendix A: Background – Noise Concepts A-9

A.1.6 Other Descriptors

As discussed in Chapter 2, there are a number of international descriptors for transportation noise seldom 

used in the U.S. The most widely encountered such descriptor, particularly in describing noise from rail 

systems, is the A-weighted "passby level," or LAeq,P.

68 This descriptor is used to quantify the noise level 

from a single vehicle passby, and is defined as the A-weighted sound level energy-averaged over the time 

of the event passby. In a sense, it is like Leq(hour), except that it is evaluated for only a single event and 

averaged over the event-specific passby time instead of a standardized time period. It is defined 

mathematically as follows:

where:

t1 is the time at the leading edge of the passby, 

t2 is the time at the trailing edge of the passby, and 

the passby duration Tp = t2 - t1.

 

68 Also sometimes abbreviated Lp,p and Lmax(mean).

Figure A-3 Typical Ldn’s

L

T

Aeq P dt

p

t

t LA

t

,

log

( )

=

















∫

10

1

10 10 10

1

2
A-10 High-Speed Ground Transportation Noise and Vibration Impact Assessment

In Japan a similar metric is used to describe the noise from train passages, LAmax, and is defined as the 

power- or energy-average of the "slow" maximum level (Lmax,s) of 20 consecutive train passbys. 

Mathematically this is expressed as:

A metric known as Sound Exposure Level, but abbreviated LAE, also is used in Japan and has a slightly 

different definition from the SEL used in this manual. It is defined as the energy-averaged value of the 

sound exposure, or energy during the event, measured within 10 dB of LAmax, sampled at a time interval of 

5/3 seconds. The mathematical expression is:

where ? t = 5/3 seconds.

A.2 RECEIVER RESPONSE TO TRANSPORTATION NOISE

An overview of receiver response to noise is presented in this section. It serves as background 

information for the noise impact criteria presented in Chapter 3 and for the criteria development process 

documented in Section A.3. 

Noise can interrupt ongoing activities and can result in community annoyance, especially in residential 

areas. In general, most residents become highly annoyed when noise interferes significantly with 

activities such as sleeping, talking, noise-sensitive work, and listening to radio or TV or music. In 

addition, some land uses, such as outdoor concert pavilions, are inherently incompatible with high noise 

levels. Annoyance to noise has been investigated and approximate exposure-response relationships have 

been quantified by the Environmental Protection Agency (EPA).69,70 The selection of noise descriptors in 

this manual is largely based upon this EPA work. Beginning in the 1970s, EPA undertook a number of 

research and synthesis studies relating to community noise of all types. Results of these studies have 

been widely published, and discussed and referenced by many professionals in acoustics. Basic 

 

69Environmental Protection Agency, "Impact Characterization of Noise Including Implications of 

Identifying and Achieving Levels of Cumulative Noise Exposure," Task group 3, Henning von Gierke, Chairman, 

Report NTID 73.4, Washington DC, 27 July 1973.

70Environmental Protection Agency, "Information on Levels of Environmental Noise Requisite to Protect 

Public Health and Welfare with an Adequate Margin of Safety," Report No. 550/9-74-004, Washington DC, March 

1974.

LAmax

i

Lmax s i

=















= 

10 ∑

1

20 10 10

1

20

10 log

( ,)

LAE t

i

LAi

= ⋅

















10 10 ∑ 10 10 log Δ
Appendix A: Background – Noise Concepts A-11

conclusions of these studies have been adopted by the Federal Interagency Committee on Noise, the 

Department of Housing and Urban Development (HUD), the American National Standards Institute, and 

even internationally. 71,72,73,74 Conclusions from this seminal EPA work remain scientifically valid to this 

day.

A synthesis of actual case studies of community reaction to newly introduced sources of noise in a 

residential urban neighborhood is shown in Figure A-4 (ref. 3). The new noise's excess above existing 

noise levels is shown in Figure A-4. Both the new and existing noise levels are expressed as Day-Night 

Sound Levels, Ldn, discussed in Section A.1.5. The community reaction to this newly introduced noise 

also is shown in Figure A-4, varying from "No Reaction" to "Vigorous Action," for newly introduced 

noises averaging from "10 decibels below existing" to "25 decibels above existing." Note that these data 

points apply only when the stated assumptions are true. For other conditions, the points shift to the right 

or left somewhat.

In a large number of community attitudinal surveys, transportation noise has been ranked among the most 

significant causes of community dissatisfaction. A synthesis of many such surveys on annoyance appears 

in Figure A-5.75,76 Different neighborhood noise exposures are plotted horizontally. The percentage of 

people who are highly annoyed by their particular level of neighborhood noise is plotted vertically. As 

shown in the figure, the percentage of high annoyance is approximately 0 at 45 decibels, 10 percent 

around 60 decibels and increases quite rapidly to approximately 70 percent around 85 decibels. The 

scatter about the synthesis line is due to variation from community to community and to some wording 

 

71Federal Interagency Committee on Urban Noise, "Guidelines for Considering Noise in Land Use 

Planning and Control," a joint publication of the Environmental Protection Agency, the Department of 

Transportation, the Department of Housing and Urban Development, the Department of Defense, and the Veterans 

Administration, Washington DC, June 1980.

72Department of Housing and Urban Development, "Environmental Criteria and Standards of the 

Department of Housing and Urban Development," 24 Code of Federal Regulations Part 51; 44 Federal Register 

40861, Washington DC, 12 July 1979.

73American National Standards Institute, "American National Standard: Compatible Land Use With 

Respect to Noise," Standard S3.23-1980, New York NY, May 1980.

74International Standards Organization, "Assessment of Noise with Respect to Community Response," 

Recommendation R-1996, Geneva, 1971.

75T.J. Schultz, "Noise Rating Criteria for Elevated Rapid Transit Structures," U.S. Department of 

Transportation Report No. UMTA-MA-06-0099-79-3, Washington DC, May 1979.

76T. J. Schultz, "Synthesis of Social Surveys on Noise Annoyance," Journal of the Acoustical Society of 

America, Vol. 63, No. 8, August 1978.
A-12 High-Speed Ground Transportation Noise and Vibration Impact Assessment

differences in the various surveys. A recent update of the original research, containing several additional 

railroad, transit and street traffic noise surveys, confirmed the shape of the original Schultz curve.77

 

77S. Fidell, D.S. Barber, and T.J. Schultz, "Updating a Dosage-Effect Relationship for the Prevalence of 

Annoyance Due to General Transportation Noise," Journal of the Acoustical Society of America, Vol. 89, No. 1, 

January 1991.

Figure A-4 Community Reaction to New Noise, Relative to Existing Noise in a Residential Urban 

Environment
Appendix A: Background – Noise Concepts A-13

As indicated by these two figures, introduction of high-speed rail noise into a community may have two 

undesirable effects. First, it may significantly increase existing noise levels in the community, levels that 

residents have mostly become accustomed to. This effect is called "relative" noise impact. Evaluation of 

this effect is "relative" to existing noise levels; relative criteria are based upon noise increases above 

existing levels. Second, newly-introduced noise may interfere with community activities, independent of 

existing noise levels; it may be simply too loud to converse or to sleep. This effect is called "absolute" 

noise impact, because it is expressed as a fixed level not to be exceeded and is independent of existing 

noise levels. Both of these effects, relative and absolute, enter into the assessment of noise impact 

discussed in Chapters 4 and 5. These two types of impact, relative and absolute, are merged into the noise 

criteria described in Chapter 3.

A.3 NOISE IMPACT CRITERIA DEVELOPMENT

The noise criteria presented in Chapter 3 of this manual have been developed based on well-documented 

criteria and research into human response to community noise. The primary goals in developing these 

noise criteria were to ensure that the impact limits be firmly founded in scientific studies, be realistically 

based on noise levels associated with high-speed rail projects, and represent a reasonable balance between 

community benefit and project costs. This section provides the background information.

Figure A-5 Community Annoyance Due to Noise

Error! Unknown switch argument.
A-14 High-Speed Ground Transportation Noise and Vibration Impact Assessment

A.3.1 Relevant Literature

An annotated list of the documents that are particularly relevant to the noise impact criteria follows:

1. US Environmental Protection Agency "Levels Document" (ref. 3): This report identifies noise 

levels consistent with the protection of public health and welfare against hearing loss, annoyance, 

and activity interference. It has been used as the basis of numerous community noise standards and 

ordinances.

2. CHABA Working Group 69, "Guidelines for Preparing Environmental Impact Statements on 

Noise":

78 This report was the result of deliberations by a group of leading acoustic al scientists with 

the goal of developing a uniform national method for noise impact assessment. Although the 

CHABA's proposed approach has not been adopted, the report serves as an excellent resource 

documenting research in noise effects. It provides a strong scientific basis for quantifying impacts 

in terms of Ldn. 

3. "Synthesis of Social Surveys on Noise Annoyance" (ref. 9): In 1978, Theodore J. Schultz, an 

internationally known acoustical scientist, synthesized the results of a large number of social 

surveys, each concerning annoyance due to transportation noise. Remarkable consistency was 

found in a group of these surveys, and the author proposed that their average results be taken as the 

best available prediction of transportation noise annoyance. This synthesis has received essentially 

unanimous acceptance by acoustical scientists and engineers. The "universal" transportation 

response curve developed by Schultz (Figure A-5) shows that the percent of the population highly 

annoyed by transportation noise increases from 0 at an Ldn of approximately 50 dBA to 100 percent 

when Ldn is about 90 dBA. Most significantly, this curve indicates that for the same increase in 

Ldn, there is a greater increase in the number of people highly annoyed at high noise levels than at 

low noise levels. In other words, a 5 dB increase at low ambient levels (40 - 50 dB) has less impact 

than at higher ambient levels (65 - 75 dB). A recent update of the original research, containing 

several railroad, transit and street traffic noise surveys, confirmed the shape of the original Schultz 

curve (ref. 10).

4. HUD Standards:

79 The U.S. Department of Housing and Urban Development (HUD) has 

developed noise standards, criteria and guidelines to ensure that housing projects supported by 

 

78National Academy of Sciences, "Guidelines for Preparing Environmental Impact Statements on Noise," 

Report fro m Committee on Bioacoustics and Biomechanics (CHABA) Working Group 69, February 1977.

79U.S. Department of Housing and Urban Development, "Environmental Criteria and Standards", 24 Code 

of Federal Regulations Part 51, 12 July 1979; amended by 49 FR 880, 6 January 1984.
Appendix A: Background – Noise Concepts A-15

HUD achieve the goal of a suitable living environment. The HUD site acceptability standards 

define 65 dB (Ldn) as the threshold for a normally unacceptable living environment and 75 dB (Ldn) 

as the threshold for an unacceptable living environment.

5. French High Speed Rail Noise Survey:

80 The first comprehensive high-speed rail noise annoyance 

survey was performed along the route of TGV Atlantique south of Paris. Surveys of residents 

along the dedicated high-speed rail line were conducted before and after operation of the trains. 

Results of the study led to recommendations that the noise assessment descriptor be modified to 

include early morning and nighttime events and that a procedure be developed for noise assessment 

of multi-modal operations. Both of these objectives are included in the development of criteria for 

this manual. 

A.3.2 Basis for Noise Impact Criteria Curves

The lower curve in Figure 3-1, representing the onset of Impact, is based on the following considerations:

• The EPA finding that a community noise level of Ldn less than or equal to 55 dBA is "requisite to 

protect public health and welfare with an adequate margin of safety" (ref. 2).

• The conclusion by EPA and others that a 5 dB increase in Ldn or Leq is the minimum required for a 

change in community reaction. 

• The research finding that there are very few people highly annoyed when the Ldn is 50 dBA, and that 

an increase in Ldn from 50 dBA to 55 dBA results in an average of 2 percent more people highly 

annoyed (see Figure A-5).

Consequently, the change in noise level from an existing ambient level of 50 dBA to a cumulative level of 

55 dBA caused by a project is assumed to be a minimal impact. Expressed another way, this is 

considered to be the lowest threshold where impact starts to occur. Moreover, the 2 percent increment 

represents the minimum measurable change in community reaction. Thus the curve's hinge point is 

placed at a project noise level of 53 dBA and an existing ambient noise level of 50 dBA, the combination 

of which yields a cumulative level of 55 dBA. The remainder of the lower curve in Figure 3-1 was 

determined from the annoyance curve (Figure A-5) by allowing a fixed 2 percent increase in annoyance at 

other levels of existing ambient noise. As cumulative noise increases, it takes a smaller and smaller 

increment to attain the same 2 percent increase in highly annoyed people. While it takes a 5 dB noise 

increase to cause a 2 percent increase in highly annoyed people at an existing ambient noise level of 50 

 

80J. Lambert, Pl Champelovier, I. Vernet, “Annoyance from high speed train noise: a social survey,” 

Journal of Sound and Vibration, 193(1), 1996.
A-16 High-Speed Ground Transportation Noise and Vibration Impact Assessment

dB, an increase of only 1 dB causes the 2 percent increase of highly annoyed people at an existing 

ambient noise level of 70 dB. 

The upper curve delineating the onset of Severe Impact was developed in a similar manner, except that it 

was based on a total noise level corresponding to a higher degree of impact. The Severe Noise Impact 

curve is based on the following considerations:

• The Department of Housing and Urban Development (HUD) in its environmental noise standards 

defines an Ldn of 65 as the onset of a normally unacceptable noise zone (ref. 7). Moreover, the 

Federal Aviation Administration (FAA) considers that residential land uses are not compatible with 

noise environments where Ldn is greater than 65 dBA 81.

• The common use of a 5 dBA increase in Ldn or Leq as the minimum required for a change in 

community reaction.

• The research finding that the foregoing step represents a 6.5 percent increase in the number of people 

highly annoyed (see Figure A-5).

Consequently, the increase in noise level from an existing ambient level of 60 dBA to a cumulative level 

of 65 dBA caused by a project represents a change from an acceptable noise environment to the threshold 

of an unacceptable noise environment. This is considered to be the level at which Severe Impact starts to 

occur. Moreover, the 6.5 percent increment represents the change in community reaction associated with 

Severe Impact. Thus the upper curve's hinge point is placed at a project noise level of 63 dBA and 

existing ambient noise level of 60 dBA, the combination of which yields a cumulative level of 65 dBA. 

The remainder of the upper curve in Figure 3-1 was determined from the annoyance curve (Figure A-5) 

by fixing the increase in annoyance for all existing ambient noise levels at 6.5 percent.

Both curves incorporate a maximum limit for the high-speed train project noise in noise-sensitive areas. 

Independent of existing noise levels, Impact for land use categories 1 and 2 is considered to occur 

whenever the high-speed rail Ldn equals or exceeds 65 dBA and Severe Impact occurs whenever the highspeed train Ldn equals or exceeds 75 dBA. These absolute limits are intended to restrict activity 

interference caused by the project alone.

Both curves also incorporate a maximum limit for cumulative noise increase at low existing noise levels 

(below about 45 dBA). This is a conservative measure that reflects the lack of social survey data on 

people's reaction to noise at such low ambient levels. Similar to the FHWA approach in assessing the 

relative impact of a highway project, the transit noise criteria include caps on noise increases of 10 dBA 

and 15 dBA for Impact and Severe Impact, respectively, relative to the existing noise level.

 

81U.S. Department of Transportation, Federal Aviation Administration, "Federal Aviation Regulations Part 

150: Airport Noise Compatibility Planning," January 1981.
Appendix A: Background – Noise Concepts A-17

Finally, due to the types of land use included in Category 3, the criteria allow the project noise for 

Category 3 sites to be 5 decibels greater than for Category 1 and Category 2 sites. This difference is 

reflected by the offset in the vertical scale on the right side of Figure 3-1. With the exception of active 

parks, which are clearly less sensitive to noise than Category 1 and 2 sites, Category 3 sites include 

primarily indoor activities and thus the criteria reflect the noise reduction provided by the building 

structure.

A.3.3 Equations for Noise Impact Criteria Curves

The noise impact criteria can be quantified through the use of mathematical equations that approximate 

the curves shown in Figure 3-1. These equations may be useful when performing the noise assessment 

methodology through the use of spreadsheets, computer programs, or other analysis tools. Otherwise, 

such mathematical detail is generally not necessary to properly implement the criteria, and direct use of 

Figure 3-1 is likely to be adequate and less time-consuming.

A total of four continuous curves are obtained from the criteria: two threshold curves ("Moderate Impact" 

and "Severe Impact") for Category 1 and 2; and two for Category 3. Note that for each level of impact, 

the overall curves for Categories 1 and 2 are offset by 5 dBA from Category 3. While each curve is 

graphically continuous, it is defined by a set of three discrete equations that represent three "regimes" of 

existing noise exposure. These equations are approximately continuous at the transition points between 

regimes.

The first equation in each set is a linear relationship, representing the portion of the curve in which the 

existing noise exposure is low and the allowable increase is capped at 10 dBA and 15 dBA for Moderate 

Impact and Severe Impact, respectively. The second equation in each set represents the impact threshold 

over the range of existing noise exposure for which a fixed percentage of increase in annoyance is 

allowed, as described in the previous section. This curve, a third-order polynomial approximation derived 

from the Schultz curve, covers the range of noise exposure encountered in most populated areas and is 

used in determining noise impact for most transit projects. Finally, the third equation in each of the four 

sets represents the absolute limit of project noise imposed by the criteria, for areas with high existing 

noise exposure. For land use categories 1 and 2, this limit is 65 dBA for Moderate Impact and 75 dBA 

for Severe Impact. For land use category 3, the limit is 70 dBA for Moderate Impact and 80 dBA for 

Severe Impact.

The four sets of equations corresponding to the curves are given below. Each curve represents a threshold 

of noise impact, with impact indicated for points on or above the curve.
A-18 High-Speed Ground Transportation Noise and Vibration Impact Assessment

where:

LE is the existing noise exposure in terms of Ldn or Leq(h), and

LP is the project noise exposure which determines impact, also in terms of Ldn or Leq(h).

A.4 STARTLE EFFECTS FROM RAPID ONSET RATES

Researchers report that sounds of approaching vehicles with rapidly rising sound signatures carry a sense 

of convergence and cause greater annoyance than receding sounds.82

A.4.1 High-Speed Rail Noise Signatures

The presence of a high-speed train system in close proximity to homes may result in a new noise unlike 

other existing sources of community noise. The sound signature at a position close to a high-speed train 

passby is characterized by sudden onset of high noise levels for a short duration. A typical example is 

shown in Figure A-6, where the sound rises rapidly at 15 dB per second and falls again within 

 

82G. Rosinger, D.W. Nixon, and H.E. vonGierke. “Quantification of the Noisiness of ‘Approaching’ and 

‘Receding’ Sounds,” J.Acoust. Soc. Am., 48, pp.843-853, October 1970.

Category 3

80 77

101 .725 1.992 3.02 10 1.043 10 44 77

22.322 0.940 44

Category 1 and 2

75 77

96 .725 1.992 3.02 10 1.043 10 44 77

17 .322 0.940 44

Category 3

70 71

76 .662 1.164 0.018 4.088 10 42 71

16 .450 0.953 42

Category 1 and 2

65 71

71 .662 1.164 0.018 4.088 10 42 71

11 .450 0.953 42

2 2 4 3

2 2 4 3

2 5 3

2 5 3





















>

− + × − × ≤ ≤

+ <

=





















>

− + × − × ≤ ≤

+ <

=





















>

− + − × ≤ ≤

+ <

=





















>

− + − × ≤ ≤

+ <

=

− −

− −

−

−

E

E E E E

E E

P

E

E E E E

E E

P

E

E E E E

E E

P

E

E E E E

E E

P

L

L L L L

L L

L

L

L L L L

L L

L

L

L L L L

L L

L

L

L L L L

L L

L

Threshold of Severe Impact :

Threshold of Moderate Impact :
Appendix A: Background – Noise Concepts A-19

approximately five seconds. Shorter trains, such as the two-car test train of the German TransRapid 

TR07, can have even faster onset rates and shorter durations. 

The onset rate is related to the rate of approach of a moving vehicle. More correctly, it is related to the 

rate at which the vector distance between the sound source and the receiver diminishes. Both speed and 

distance figure into the process. Measured onset rates from two high-speed train systems are plotted in 

Figure 2-6. 

A.4.2 Research on Startle Effects

When the onset of sound is very sudden, people tend to be startled, or surprised, especially when they are 

not expecting it. Researchers have proposed various adjustments to account for the increased annoyance 

of fast-rising sound events. The most recent study into the added annoyance from rapid onset rates has 

been conducted in three parts by the US Air Force in connection with low-altitude military test flights.83 

The initial literature review resulted in an interim metric whereby an “onset rate -adjusted SEL” was used 

 

83E. Stusnick, K. Bradley. “The Effect of Onset Rate on Aircraft Noise Annoyance.” USAF Report 

AL/OE-TR-1993-0170, October 1992.

Figure A-6 Time History of A-Weighted Sound Level of Maglev at 25 m
A-20 High-Speed Ground Transportation Noise and Vibration Impact Assessment

in noise impact analyses where such operations were conducted. The interim adjustment was an addition 

to the SEL of the passby, starting with 0 dB for onset rates up to 15 dB/sec, ramping up to a

 maximum of 5 dB for onset rates of 30 dB/sec and higher. Laboratory tests using simulated sound and 

people hired for the occasion followed, resulting in a revised adjustment. Finally, psychoacoustic tests 

were conducted in a real home environment with hired test subjects and the currently recommended 

adjustment was developed. Again, the adjustment is 0 dB up to an onset rate of 15 dB/sec, but the ramp 

extends to an addition of 11 dB at an onset rate of 150 dB/sec, with the relationship:

Adjustment to SEL = 11 log (onset rate) - 12.9, in decibels

where:

15 dB/sec < onset rate < 150 dB/sec.

A.4.3 Startle Effects Applied to High-Speed Train Impact Assessment

The interim metric adopted by US Air Force after the first stage of its study was cited as the basis for the 

suggested adjustment for noise from high-speed maglev operations in a report prepared for the Federal 

Railroad Administration-sponsored National Maglev Initiative (NMI).84 The recommended adjustment at 

that time was to add 5 dB to SEL whenever the onset rate from a maglev passby exceeded 15 dB/sec. 

Since data are available to show onset rates as a function of speed divided by distance, it was possible to 

develop a curve defining the relationship between speed and distance within which the onset rate exceeds 

15 dB/sec for a maglev train. The proposed onset rate adjustment was recommended for assessment of 

noise impact from maglev trains.

 

84C. E. Hanson, P. Abbot, and I. Dyer. “Noise from High Speed Maglev Systems,” US Department of 

Transportation, Federal Railroad Administration, Report No. DOT/FRA/NMI - 92-18, January 1993.
Appendix A: Background – Noise Concepts A-21

Figure A-7 Zones of Potential Startle Effect

Applying the same approach, but using the latest revised US Air Force onset rate adjustments starting 

with 0 dB at 15 dB/sec, results in the relationships shown in Figure A-7. The new Air Force adjustments 

of 2 dB to 5 dB are plotted along with the original NMI proposed adjustment of 5 dB. The revised 

adjustments result in the potential for startle to be confined to a much narrower region than was obtained 

using the NMI method. 

The following issues remain unresolved regarding application of the Air Force research to determine the 

startle effects of high speed rail:

1. What is the effect of scheduled events, such as train passbys, vs. "surprise" events, such as 

military training flights? Since high-speed trains always will be on the same track and on a 

schedule, it may be reasonable to expect habituation for long-term residents. Hence, an 

adjustment to every SEL from passing high-speed trains appears excessive.

2. Sound levels from train passbys are not as high, nor are onset rates as great as they are from 

low altitude military aircraft. Hence, the startle effect may not be the same. 

3. The onset rate adjustments as proposed by the Air Force when applied to high-speed rail 

systems (Figure A-6) take place in a distance close enough to be affected already by noise. 

There may be no further reason to add to the impact assessment.
A-22 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Without better definition of the application of results of noise from aircraft overflights to noise from highspeed rail passbys, it is appropriate to consider startle effects as “additional information” included in the 

impact assessment, rather than to include a penalty in the calculation of noise exposure itself. What 

remains to be determined is an onset rate that could be considered significant enough to cause startle on a

regular basis. Lacking any other direction from research, the onset rate that would cause a 3 dB 

adjustment for the Air Force has been adopted for this manual. The resulting distance vs speed 

relationship is given in Figure 4-2.

A.5 EFFECTS ON LIVESTOCK AND WILDLIFE

A.5.1 Summary

A wide range of studies have been conducted concerning noise effects on animals. For humans, 

annoyance is considered to be the primary environmental noise effect; thresholds for annoyance in terms 

of sound exposure have been determined by surveys as described in Section A.3. However, for animals, 

the effects are not easily determined. Usually the studies require introduction of a specific noise event 

like an aircraft overflight and a subsequent observation of animal response. Observations of response to 

noise exposure have ranged from no reaction or mild responses such as slight changes in body position to 

extreme responses such as panic and attempts to escape. Long-term changes in behavior tend to be 

strongly influenced by factors other than short term noise exposure, such as weather, predation, disease 

and other disturbances to animal populations. Conclusions from research conducted to date provide only 

preliminary indications of the appropriate descriptor, rough estimates of threshold levels for observed 

animal disturbance, and habituation characteristics of only a few species. Long-term effects continue to 

be a matter of speculation. Moreover, most of the noise events used in prior studies are related to aircraft 

overflights. Consequently, any criteria adopted for effects on animals by high-speed rail noise must be 

considered interim until further specific research results are known. Following are discussions of 

descriptors and levels from the literature.85,86,87,88,89 

 

85K.M. Manci, D.N. Gladwin, R. Villella, and M.G. Cavendish. “Effects of aircraft noise and sonic booms on 

domestic animals and wildlife: a literature synthesis.” U.S. Fish and Wildlife Service National Ecology Research 

Center, Ft. Collins, CO., Report NERC-88/29, 1988.

86P. Dufour, “Effects of Noise on Wildlife and Other Animals: Review of Research Since 1971.” US 

Environmental Protection Agency, Report 550/9-80100, July 1980.

87A. M. McKechnie, D.N. Gladwin. “Aircraft Overflight Effects on Wildlife Resources.” US National Park Service, 

NPOA Report No. 93-8, November 1993.

88F. Bradley, C. Book, and A.E. Bowles. “Effects of Low-Altitude Aircraft Overflights on Domestic Turkey 

Poults,” Report No. HSD-TR-90-034, US Air Force Systems Command, Noise and Sonic Boom Impact Technology 

Program, June 1990.

89 C.S.Y. Lee and G. Fleming. “General Health Effects of Transportation Noise.” U.S. Department of 

Transportation, Federal Railroad Administration, DTS-34-RR297-LRZ, June 2002
Appendix A: Background – Noise Concepts A-23

A.5.2 Noise Descriptor

A noise descriptor for noise effects on wildlife has not been universally adopted, but recent research 

indicates the sound exposure level (SEL) is the most useful predictor of responses. Characteristic of the 

bulk of research to date has been lack of systematic documentation of the source noise event. Many 

studies report “sound levels” without specifying the frequency spectrum or duration. A notable exception 

is a study sponsored by U.S. Air Force that identifies SEL as the best descriptor for response of domestic 

turkey poults to low-altitude aircraft overflights (ref. 21). Another report questions whether an Aweighted sound level used in the SEL for aircraft overflights is appropriate for animals since their hearing 

differs from humans (ref. 20). However, since no weighting has been established for representing the 

hearing characteristics of wild animals, the A-weighted sound level continues to be used.

A.5.3 Thresholds for Disturbance

Most studies have focused on identifying a noise level associated with disturbance effects, even if the 

type of noise event varied considerably from study to study. In the well-documented study that 

recommended SEL as the preferred descriptor, a threshold of response for disturbance (“100 percent rate 

of crowding”) of domestic turkeys was identified as SEL = 100 dB (ref. 21). Even if the descriptors are 

not the same, many studies report levels in the vicinity of 100 dB as associated with an observable effect, 

as shown in Table A-1. The information in this table is taken from an extensive survey on aircraft noise 

effects90. Until more definitive information on thresholds can be developed, an interim criterion of SEL = 

100 dB will be used for disturbance by high-speed train operations. 

A.5.4 Habituation

There is evidence that some animals demonstrate reduced response to noise after prior exposure, but that 

a few species never become accustomed to, or habituate, to high noise levels. Researchers found that for 

turkeys, previous exposure to sound levels below the 100 dB threshold was sufficient to eliminate panic 

responses to higher level sounds (ref. 21). On the other hand, some animals and birds, such as the grizzly 

bear, Dall sheep, and least tern, have not been observed to habituate (ref. 20). Since habituation is found 

to be species-dependent, a general criterion cannot be developed at this time.

 

90 K.M. Manci, D.N. Gladwin, R. Villella, and M.G. Cavendish. “Effects of aircraft noise and sonic booms on 

domestic animals and wildlife: a literature synthesis.” U.S. Fish and Wildlife Service National Ecology Research 

Center, Ft. Collins, CO., Report NERC-88/29, 1988.
A-24 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Table A-1 Summary of Noise Levels Associated with Effects on Animals and Birds (from ref. 20)

Animal Category Species

Noise Level and Type (if 

known) Associated with 

Effect

Effect

105 dB Reduction in milk production

97 dB Changes in blood composition

Dairy Cow

110 dB, 1 kHz Changes in blood composition

108-120 dB Hormonal changes

93 dB Hormonal changes

Swine

120-135 dB Increased heart rate

100 dB “white noise” Increased heart rate, 

respiration

90 dB”white noise” Decreased thyroid activity

Domestic Mammals

Sheep

100 dB Increase in number of lambs 

per ewe

Reindeer Sonic booms Startle

Caribou Aircraft Startle, panic running

Wild Mammals

Pronghorn antelope 77 dBA, helicopter Running

Domestic Birds Chicken 100 dB Blood composition

115 dB Interrupt brooding

Quail 80 dB Accelerated hatching

Canary 95-100 dB Hearing loss

Seabirds (general) Sonic boom Startle, flush from nest

Tern Sonic boom, frequent Reduced reproduction

California condor Blasting, drilling, etc. Flush from nest; abandon area

Wild Birds

Raptors Sonic booms Alarm
Appendix B: Determining Existing Noise B-1

APPENDIX B - DETERMINING EXISTING NOISE

This appendix provides additional detail for determining existing noise by: (1) full measurement, (2) 

computation from partial measurements, and (3) tabular look-up. The words "existing noise" and 

"ambient noise" are often used interchangeably.

The full set of options for determining existing noise at receivers of interest is as follows:

• OPTION 1: For non-residential land uses, measure a full hour's Leq at the receiver of interest, during 

a typical hour of use on two non-successive days. The hour chosen should be the one in which 

maximum project activity will occur. The Leq will be accurately represented.

• The three options for residential land uses are –

1. OPTION 2: Measure a full day's Ldn. The Ldn will be accurately represented.

2. OPTION 3: Measure the hourly Leq for three typical hours: peak traffic, midday and late 

night. Then compute the Ldn from these three hourly Leq's. The computed Ldn will be 

slightly underestimated. 

3. OPTION 4: Measure the hourly Leq for one hour of the day only, preferably during midday. 

Then compute the Ldn from this hourly Leq. The computed Ldn will be moderately 

underestimated. 

• OPTION 5: For all land uses, compute either the Leq or the Ldn from a measured value at a nearby 

receiver – one where the ambient noise is dominated by the same noise source. The computed value 

will be represented with only moderate precision. 

• OPTION 6: For all land uses, estimate either the Leq or the Ldn from a table of typical values, 

depending upon distance from major roadways or upon population density. The resulting values will 

be underestimated significantly.

Option 1: For non-residential land uses, measure the hourly L eq for the hour of interest

Full one-hour measurements are the most precise way to determine existing noise for non-residential 

receivers of interest. Such full-duration measurements are preferred over all other options. The following 

procedures apply to full-duration measurements:
B-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

• Measure a full hour's Leq at the receiver of interest on at least two non-successive days during a 

typical hour of use. This would generally be between noon Monday and noon Friday, but weekend 

days may be appropriate for places of worship. On both days, the measured hour must be the same as 

that for which proje ct noise is computed: the loudest facility hour that overlaps hours of noisesensitive activity at the receiver.

• At all sites, locate the measurement microphone as shown in Figure 5-2 (Chapter 5), depending upon 

the relative orientation of project and ambient sources. A microphone location that is shielded 

somewhat from the ambient source is preferred. At such locations, ambient noise will be measured at 

the quietest location on the property for purposes of noise impact assessment so that noise impact will 

be assessed most critically. 

• Undertake all measurements in accordance with good engineering practice (see References 1 and 2 of 

Chapter 5).

Option 2: For residential land uses, measure the L dn for a full 24 hours

Full 24-hour measurements are the most precise way to determine ambient noise for residential receivers 

of interest. Such full-duration measurements are preferred over all other options. The following 

procedures apply to full-duration measurements:

• Measure a full 24-hour's Ldn at the receiver of interest, for a single weekday (generally between noon 

Monday and noon Friday).

• At all sites, locate the measurement microphone as shown in Figure 5-2, depending upon the relative 

orientation of project and ambient sources. A microphone location that is shielded somewhat from 

the ambient source is preferred. At such locations, ambient noise will be measured at the quietest 

location on the property for purposes of noise impact assessment so that noise impact will be assessed 

most critically. 

• Undertake all measurements in accordance with good engineering practice (see References 1 and 2 of 

Chapter 5).

Option 3: For residential land uses, measure the hourly L eq for three hours and then compute L dn

An alternative way to determine Ldn, less precise than its full-duration measurement, is to measure hourly 

Leq's for three typical hours of the day and then to compute the Ldn from these three hourly Leq's. The 

following procedures apply to this partial-duration measurement option for Ldn:

• Measure the one-hour Leq during each of the following time periods: once during peak-hour roadway 

traffic, once midday between the morning and afternoon roadway-traffic peak hours, and once 

between midnight and 5 am. For locations with no significant traffic patterns, it will be sufficient to 

measure a morning hour (7 am to 9 am), a midday hour (10 am to 4 pm), and a late night hour (10 pm 

to 7 am).

• Compute Ldn with the following equation:
Appendix B: Determining Existing Noise B-3

This value of Ldn will be slightly underestimated, due to the subtraction of 2 decibels from each of the 

measured levels before their combination. As explained previously, this underestimate is intended to 

compensate for the reduced precision of the computed Ldn here, compared to its full-duration 

measurement.

• At all sites, locate the measurement microphone as shown in Figure 5-2, depending on the relative 

orientation of project and ambient sources. A microphone location that is shielded somewhat from 

the ambient source is preferred. At such locations, ambient noise will be measured at the quietest 

location on the property for purposes of noise impact assessment so that noise impact will be assessed 

most critically. 

• Undertake all measurements in accordance with good engineering practice (see References 1 and 2 of 

Chapter 5).

Option 4: For residential land uses, measure the hourly L eq for one hour and then compute L dn

The next level down in precision is to determine Ldn by measuring the hourly Leq for one hour of the day 

and then to compute Ldn from this hourly Leq. This method is useful when there are many sites in a 

General Assessment, or when checking whether a particular receiver of interest represents a cluster in a 

Detailed Analysis. The following procedures apply to this partial-duration measurement option for Ldn:

• Measure the one-hour Leq during any hour of the day. The loudest hour during the daytime period is 

preferable. If this hour is not selected, then other hours may be used with less precision.

• Convert the measured hourly Leq to Ldn with the applicable equation:

For measurements between 7am and 7pm: L ,

For measurements between 7pm and 10pm: , and

For measurements between 10pm and 7am: .

dn ≈ −

≈ +

≈ +

L

L L

L L

eq

dn eq

dn eq

2

3

8

The resulting value of Ldn will be moderately underestimated, due to the use of the adjustment 

constants in these equations. As explained previously, this underestimate is intended to 

compensate for the reduced precision of the computed Ldn here, compared to the more precise 

methods of determining Ldn.

• At all sites, locate the measurement microphone as shown in Figure 5-2, depending upon the relative 

orientation of project and existing sources. A microphone location that is shielded somewhat from 

the ambient source is preferred. At such locations, ambient noise will be measured at the quietest 

location on the property for purposes of noise impact assessment so that noise impact will be assessed 

most critically. 

Ldn

L peakhour L midday L latenight eq eq eq

≈ ⋅ + ⋅ + ⋅

















−

− − +

10 3 10 12 10 9 10 13 8

2

10

2

10

8

10 log ( ) ( ) ( ) .

( ) ( ) ( )
B-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

• Undertake all measurements in accordance with good engineering practice (see References 1 and 2 of 

Chapter 5).

Option 5: For all land uses, compute either L eq or L dn from a nearby measured value

A computation method comparable in precision to Option 4 is to determine the ambient noise, either 

Leq(h) or Ldn, from a measured value at a nearby receiver – one where the ambient noise is dominated by 

the same noise source. This method is used to characterize noise in several neighborhoods by using a 

single representative receiver. Care must be taken to ensure that the measurement site has a similar noise 

environment to all areas represented. If measurements made by others are available, and the sites are 

equivalent, they can be used to reduce the amount of project noise monitoring. The following procedures 

apply to this computation of ambient noise at the receiver of interest: 

• Choose another receiver of interest, called the "comparable receiver," at which:

ÿ The same source of ambient noise dominates.

ÿ The ambient LCompRec was measured with either OPTION 1 or OPTION 2 above.

ÿ The ambient measurement at the comparable receiver was made in direct view of the major source 

of ambient noise, unshielded from it by noise barriers, terrain, rows of buildings, or dense tree 

zones.

• From a plan or aerial photograph, determine: (1) the distance DCompRec from the comparable receiver 

to the near edge of the ambient source, and (2) the distance DThisRec from this receiver of interest to the 

near edge of the ambient source.

• Also determine N, the number of rows of buildings that intervene between the receiver of interest and 

the ambient source.

• Compute the ambient noise at this receiver of interest with the applicable equation:

If roadway sources dominate:

If other sources dominate:

The resulting value of LThisRec will be moderately underestimated. As explained previously, this 

underestimate is intended to compensate for the reduced precision of the computed Ldn, compared to the 

more precise methods of determining ambient noise levels.

L L

D

D

This c Comp c N

This c

Comp c

Re Re

Re

Re

≈ − log

















15 − 3

L L

D

D

This c Comp c N

This c

Comp c

Re Re

Re

Re

≈ − log

















25 − 3
Appendix B: Determining Existing Noise B-5

Option 6: For all land uses, estimate either L eq(h) or L dn from a table of typical values 

The least precise way to determine the ambient noise is to estimate it from a table. A tabular look-up can 

be used to establish baseline conditions for a General Noise Assessment if a noise measurement cannot be 

made. It should not be used for a Detailed Noise Analysis. For this estimate of ambient noise:

• Read the ambient noise estimate from the relevant portion of Table 4-5. These tabulated estimates 

depend upon distance from major roadways, rail lines or upon population densities. In general, these 

tabulated values are significant underestimates. As explained previously, underestimates are intended 

to compensate for the reduced precision of the estimated ambients, compared to the options that 

incorporate some degree of measurements. 
B-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment
Appendix C: Converting Between Lmax and SEL C-1

APPENDIX C - CONVERTING BETWEEN LMAX AND SEL

This appendix provides procedures for:

1) computing Lmax for a single high-speed train passby using the source reference levels in SEL and 

methods given in Chapters 4 and 5, and

2) estimating source reference levels in SEL for a General Assessment from either measured or 

specified values of the single -passby Lmax. 

The first SEL to Lmax conversion may be useful in determining whether a proposed project or type of 

equipment will meet the noise limit defined in the project specifications, almost always given in terms of 

Lmax. The second procedure, converting from Lmax to SEL, involves computing reference SELs specific to 

a certain trainset or project noise specification, which may be different from the generalized levels given 

in this manual. A General Noise Assessment can then be performed based on measurements, equipment 

specifications, or project noise limits.

A.1 COMPUTING Lmax FOR A SINGLE TRAIN PASSBY

The Lmax conversion procedure from the reference SELs given in Chapter 4 (Initial Noise Evaluation) or 

Chapter 5 (Detailed Noise Analysis) to a single Lmax value is summarized as follows:

Step 1. Select Source Reference SEL(s). Classify the project into one of the vehicle categories 

defined in Table 4-2 or Table 5-2. For General Assessment, the speed regime (I, II or III) 

also must be selected from Table 4-2, which identifies the single dominant noise source for 

the given speed and the corresponding reference SEL. For Detailed Analysis, separate 

subsource SELs are listed in Table 5-2.

Step 2. Adjust for Project Operating Conditions. Adjust the reference SEL (General Assessment) 

or each applicable subsource reference SEL (Detailed Analysis) at 50 feet for operating 

conditions for the project or for a particular corridor segment, using the methods in Section 

4.2.1 or 5.2.2. 
C-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Step 3. Adjust for Propagation with Distance. Propagate each adjusted SEL out to the specified 

distance (if other than the reference distance of 50 feet), accounting for attenuation with 

distance, shielding, and ground effect, if necessary, using the methods in Section 4.2.2 or 

5.2.3.

Step 4. Convert SEL to Lmax. Compute Lmax using the equations in Table C-1. For the Detailed 

Analysis method, choose the largest of the subsource Lmax values as the overall Lmax for the 

train passby.

Table C-1 Computation of Lmax for a High-Speed Train Passby using General Assessment or 

Detailed Analysis Method

Applicable Parameters

General Assessment Detailed Analysis SEL–to–Lmax Equation

Speed Regime I Propulsion Subsource 

use len = total length 

of power units, 

in feet

use len = length of 

one power unit, 

in feet

L SEL ( )

len

S

max = − log log .











10  + 10 2a − 3 3

Speed Regime II

Wheel/Rail or 

Guideway/Structural 

Subsource

use len = total length 

of train, in feet

use len = length of 

coaches only, in feet

L SEL [ ( )]

len

S

max = − log log sin .











10  + 10 2a + 2a − 3 3

Speed Regime III Aerodynamic 

Subsources 

use len = total length 

of leading power car, 

in feet

use len = subsource 

length as defined in 

Table 5-2, in feet

L SEL ( )

len

S

max = − log log .











10  + 10 2a − 3 3

Variables are defined as follows:

S

len

d

len

d

=

=













=

=

−

train speed, in mph,

, in radians,

length as defined above, and

receiver distance from track centerline, in feet.

a tan 1

2

A.2 COMPUTING REFERENCE SEL'S FROM LMAX FOR GENERAL ASSESSMENT 

METHOD

If Lmax for a specific trainset is available from vehicle noise measurements, manufacturer specifications, 

or a specific project limit, it is possible to estimate the equivalent reference SELs to use in the General 

Noise Assessment (Chapter 4) procedure presented in this manual. The Detailed Noise Analysis (Chapter 

5) method, however, involves the use of detailed component, or subsource, SELs that cannot be 

determined accurately from a single passby Lmax value. Determination of subsource SELs requires more 

complex measurement techniques, such as a microphone array or controlled single microphone 
Appendix C: Converting Between Lmax and SEL C-3

measurements with a low sound barrier to shield wheel/rail noise, in order to isolate certain source 

components. 

If a specific Lmax value is available for the proposed trainset and Detailed Noise Analysis procedures are 

to be followed, it is recommended that the subsource SELs provided in Chapter 5 be used to first calculate 

Lmax as described in Appendix C (Section C.1). This calculated Lmax can then be compared with the 

specified or measured Lmax and if necessary, one or more of the subsource SELs can be adjusted to 

account for the discrepancy. This may be an iterative process until the computed Lmax and the specified 

Lmax are the same. This technique should be exercised with caution, however, since judgement and 

understanding of the subsource mechanisms are required to determine which of the subsource SELs 

should be adjusted.

The procedure for converting Lmax to a reference SEL for use in the General Noise Assessment method is 

summarized as follows:

Step 1. Identify Vehicle Category. Classify the project into one of the vehicle type categories 

listed in Table 4-2. 

Step 2. Identify Major Sound Source and Parameters. Identify the appropriate speed regime I, II 

or III from Table 4-2. The speed regime establishes the dominant sound source for the given 

speed (propulsion, wheel/rail or aerodynamic). For the vehicle category, obtain noise model 

parameters such as speed coefficient, reference length, and reference speed corresponding to 

the speed regime from Table 4-2.

Step 3. Convert Lmax to SEL. Compute SEL using the equations in Table C-2. This computation 

yields the SEL for the operating conditions and distance corresponding to the Lmax

measurement or specification.

Step 4. Normalize to Reference Conditions. Adjust the resulting SEL to the reference distance 

and operating conditions of Table 4-2, using the equation in Table C-2. This adjustment 

yields a new reference SEL appropriate for comparison with the values listed in Table 4-2.
C-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Table C-2 Computation of SEL for a High-Speed Train Passby from Lmax for General Assessment

To convert from Lmax to SEL:

Speed Regime I

SEL L ( )

len

S

= +











max 10 log  − 10 log 2a + 3.3

where len = total length of power unit(s), in feet

Speed Regime II

SEL L [ ( )]

len

S

= +











max 10 log  − 10 log 2a + sin 2a + 3.3

where len = total length of train, in feet

Speed Regime III

SEL L ( )

len

S

= +











max 10 log  − 10 log 2a + 3.3

where len = total length of leading power car, in feet

To normalize back to Reference Conditions of Table 4-2:

SEL SEL K

S

S

len

len d

ref

ref ref

= +











 +











 −











log 10log 15log 

50

SEL SEL

K

S

S

len

d

len

d

ref

ref

ref

=

=

=

=

=

=

=













−

 adjusted to reference parameters of Table 4 - 2 at reference distance,

Speed coefficient (from Table 4 - 2),

Reference speed, mph (from Table 4 - 2),

Train speed, mph,

Reference length, feet (from Table 4 - 2),

receiver distance from track centerline, feet, and

a tan , radians. 1

2
Appendix D: High Speed Train Vibration Measurements D-1

APPENDIX D -HIGH SPEED TRAIN VIBRATION MEASUREMENTS

Vibration velocity measurement results for several different types of high-speed trains are shown in 

Figure D-1. Included in Figure D-1 are the results from: 1) the European measurements in May 1995; 2) 

tests with X2000 equipment on the Northeast Corridor; and 3) measurements on TGV trains in 1991. All 

of the data points have been normalized to 150 mph. The wide spread in the data is partly due to 

differences in the equipment and track conditions, and partly from the differences in geology. To clarify 

the trends, Figure D-2 shows best-fit curves for the same data.

Figure D-1 Overall Vibration Velocity Level for Different High Speed Trains

Some observations derived from the measurements presented in Figures D-1 and D-2 are:

• The TGV and Eurostar trainsets measured along the Nord (North) line in France all had very similar 

vibration levels. The TGV data measured on the Atlantique line show a distinctly different 

characteristic.
D-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

• The Pendolino trainsets measured in Italy have vibration levels similar to the TGV trainsets operating 

on the Nord line.

• The X2000 trainsets measured in Sweden show vibration levels much higher than those of the TGV or 

Pendolino trainsets. However, as discussed later, normalizing the data to a single set of soil 

conditions indicate that X2000 trainsets actually generate ground-borne vibration forces similar to the 

other high-speed trains. Consequently, the higher levels appear to be primarily due to the propagation 

conditions of the ground at the test site in Sweden.

• The test with the X2000 trainset on the Northeast Corridor show relatively high vibration levels. 

Because propagation tests were not a part of the Northeast Corridor testing, however, it is unknown 

whether these higher vibration levels were due to geology, track condition, wheel condition, or other 

factors.

A summary of the overall vibration velocity levels of the trainsets measured in Europe, calculated from 

the smoothed 1/3 octave band spectra, are shown in Figure D-3 The differences in the vibration levels 

measured with the different types of trainsets are shown clearly. The X2000 had significantly higher 

vibration at all distances, with the levels over 30 decibels higher than the TGV trainsets at 100 meters 

from the tracks.

Figure D-2 Best-Fit Curves of Vibration Velocity Level vs. Distance
Appendix D: High Speed Train Vibration Measurements D-3

Figure D-3 Vibration Velocity vs. Distance Calculated from Smoothed 1/3 Octave Bands

Figures D-1, D-2 and D-3 indicate the overall levels of ground-borne vibration as a function of distance, 

but do not indicate the dominant frequency range in the ground-borne vibration generated by each 

trainset. Knowing the dominant frequency range helps determine whether the ground-borne vibration is 

perceived as vibration or audible noise by occupants of buildings near train tracks. The measured 

vibration velocity in terms of 1/3 octave band levels for the TGV, X2000, and Pendolino trainsets 

normalized to 150 mph are shown in Figure D-4. The X2000 measured at the test site in Sweden showed 

the highest levels of low-frequency vibration below 40 Hz, with the Pendolino data falling between the 

X2000 and the TGV in this range. In fact, the X2000 vibration levels were higher over the entire 

frequency spectrum, except at 50 and 63 Hz, where TGV vibration was highest.

As discussed above, much of the difference between the trainsets is likely to be due to geology variations 

rather than differences in suspension, axle load or wheel conditions of the trainsets. The line source 

transfer mobility spectra, which indicate the frequency-dependent response characteristics of the ground, 

for the three different measurement sites are shown in Figure D-5. It is clear that the transfer mobilities 

are very different between the three primary sites in France, Italy and Sweden. For example, at 100 Hz 

the transfer mobility measured at the site in Sweden is 8 decibels higher than the site in France and about 

30 decibels higher than the site in Italy. All of the sites were in rural areas where relatively little is known 

about the specific geology at the test sites. The measurements indicated that these differences in transfer 

mobility are fairly consistent out to 100 meters from the vibration source.
D-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Figure D-4 Comparison of 1/3 Octave Band Spectra

Figure D-5 Line-Source Transfer Mobility at the Test Sites
Appendix D: High Speed Train Vibration Measurements D-5

The force density functions derived for X2000, Pendolino, TGV, and Eurostar trainsets, all normalized to 

a speed of 150 mph, are shown in Figure D-6 The force densities are also very different, but the 

differences are not as large as the measured ground vibration levels. The TGV and Eurostar force 

densities are close enough to be considered the same. The X2000 and the Pendolino are surprisingly 

similar, considering the large difference in the vibration spectra.

The four force density functions can each be combined with the transfer mobility from a single site to 

approximate what the vibration levels would be if all of the trainsets were operating on the same track at 

the same location. The resulting overall vibration levels using the transfer mobility from the primary site 

(Site D) in France are shown in Figure D-7, and the same results using the transfer mobility from the 

primary site (Site 3B) in Sweden are shown in Figure D-8 .

Both figures show that using the same transfer mobility, in effect normalizing the ground vibration from 

the trainsets to one site, substantially reduces the differences in the overall vibration levels. Using the 

transfer mobility from Sweden, the TGV, Eurostar, and X2000 are all within about 2 decibels, and the 

Pendolino is 3 to 4 decibels lower. In this case, the range of ground-borne vibration from the different 

trainsets is limited to a narrow "band" between 75 and 80 VdB at 30 meters from the track. Using the 

transfer mobility from France, the TGV and Eurostar are 2 to 3 decibels lower than the Pendolino, and the 

X2000 is about 4 decibels higher than the Pendolino. The levels range from 65 to 73 VdB at 30 meters 

from the track centerline. The overall conclusion drawn is that all of the trainsets would generate 

significantly higher ground vibration levels at the Swedish test site than at the French site.

Figure D-6 Force Density Functions Derived from Measurements
D-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Figure D-7 Projected Vibration Velocity, Transfer Mobility from Site in France

Figure D-8 Projected Vibration Velocity, Transfer Mobility from Site in Sweden

Error! Unknown switch argument.
Appendix D: High Speed Train Vibration Measurements D-7

Finally, to further illustrate the strong effects of the transfer mobility, the results of applying the X2000 

force density to the transfer mobility functions at each of the three primary sites are shown in Figure D-9, 

in terms of overall vibration level as a function of distance. This shows that close to the track centerline, 

the projected vibration levels are all relatively high. However, the levels with the transfer mobility from 

Site 3B in Sweden show considerably slower attenuation with distance than with the other two transfer 

mobilities due to geological factors.

Figure D-9 Projected Vibration Velocity, X2000 Force Density
D-8 High-Speed Ground Transportation Noise and Vibration Impact Assessment
Appendix E: Source Reference Levels for Conventional Trains E-1

APPENDIX E - SOURCE REFERENCE LEVELS FOR CONVENTIONAL TRAINS 

(FREIGHT AND PASSENGER)

Noise source reference levels for conventional freight and passenger trains in service throughout the 

United States are based on measurements of more than 315 trains during the environmental assessments 

associated with recent railroad mergers.91 The measurements were taken on a variety of road locomotives 

in freight service. The results were averaged, adjusted for speed and distance and used in the projection 

models for impact assessments by the Surface Transportation Board. Passenger train data were obtained 

from a variety of environmental assessments. 

The source reference levels are for freight and passenger locomotives, freight cars, passenger coaches, 

and horns. Locomotive, freight car, and passenger coach reference levels are expressed in a form that can 

be used directly in the computations based on Table 5-2. 

Passenger trains in regional and interstate service can be assumed to have similar characteristics, although 

it is recommended to consult the FTA guidance manual for a more detailed treatment of commuter rail 

operations.92 Horn reference levels are applicable to a separate computational model developed by FRA 

in connection with the study on the Use of Locomotive Horns at Highway-Rail Grade Crossings.93

 

91CSX/NS/Conrail merger, 1997; CN/IC merger 1998

92U.S. Department of Transportation, Federal Transit Administration. “Transit Noise and Vibration Impact 

Assessment,” DOT-T-95-16, April 1995.

93U.S. Department of Transportation, Federal Railroad Administration. “Final Environmental Impact 

Statement on Use of Locomotive Horns at Highway-Rail Grade Crossings.” 2003.
E-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Table E-1. Noise Source Reference Levels for Conventional Freight Trains (SEL at 50 feet)

Category Subsource 

Component

Length 

Definition

Height above 

rails (ft)

SELref

(dBA)

len ref (ft) S ref

(mph)

K

Freight 

locomotive

Propulsion len power 10 97 90 40 10

Freight car Wheel-rail lentrain 1 100 2000 40 20

Passenger 

locomotive

Propulsion len power 10 94 60 40 10

Passenger 

coach

Wheel-rail lentrain 1 94 500 40 20

Horn Horn N/A 13 114 N/A N/A N/A
Appendix F: Glossary of Terms F-1

APPENDIX F - GLOSSARY OF TERMS

A-weighting – A method used to alter the sensitivity of a sound level meter with respect to frequency so 

that the instrument is less sensitive at frequencies where the human ear is less sensitive. Also 

written as dBA.

Aeroacoustic – Acoustical waves generated by pressure fluctuations in moving air.

Ambient – The pre-project background noise or vibration level.

Alignment – The horizontal location of a railroad as described by curved and tangent track.

Auxiliaries – The term applied to a number of separately driven machines, operated by power from the 

main engine. They include the air compressor, radiator fan, traction motor blower, exciter for the 

main generator and the boiler blower.

Ballast Mat – A 2- to 3-inch-thick elastomer mat placed under the normal track ballast on top of a rigid 

slab.

Ballast – Selected material placed on the roadbed for the purpose of holding the track in line and at 

surface.

Cab – The space in the power unit containing the operating controls and providing shelter and seats for 

the engine crew.

Catenary – On electric railroads, the term describing the overhead conductor that is contacted by the 

pantograph or trolley, and its support structure.

Coach – A passenger-carrying rail car, usually with a center aisle and two rows of seats.

Consist – The total number and type of cars and locomotives in a trainset.
F-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Continuous Welded Rail – A number of rails welded together in lengths of 400 feet or longer.

Corrugated Rail – A rough condition on the rail head of alternate ridges and grooves, which develops in 

service.

Cross Tie – The transverse member of the track structure to which the rails are spiked or otherwise 

fastened to provide proper gage and to cushion, distribute, and transmit the stresses of traffic 

through the ballast to the roadbed.

Crossover – Two turnouts with the track between the frogs arranged to form a continuous passage 

between two nearby and generally parallel tracks.

Cut – A term used to describe a railbed at a lower level than the surrounding ground.

dB – see Decibel

dBA – see A-weighting

Decibel – A unit of level which denotes the ratio between two quantities that are proportional to power; 

the number of decibels is 10 times the logarithm of this ratio. Also written as dB.

Descriptor – A quantitative metric used to identify a specific measure of sound level.

DNL – see Ldn

DOT – The Department of Transportation. An agency of the U. S. government having jurisdiction over 

matters pertaining to all modes of transportation.

Electrification – A term used to describe the installation of overhead wire or third rail power distribution 

facilities to enable operation of trains hauled by electric locomotives.

Embankment – A bank of earth, rock or other material constructed above the natural ground surface.

Equivalent Level – The level of a steady sound which, in a stated time period and at a stated location, has 

the same A-weighted sound energy as the time-varying sound. Also written as Leq.

Flange – The vertical projection along the inner rim of a wheel that serves, together with the 

corresponding projection of the mating wheel of a wheel set, to keep the wheel set on the track. 

Flow Separation – Loss of adherence of air to parts of the train’s outer surface.
Appendix F: Glossary of Terms F-3

FRA – The Federal Railroad Administration. An agency of the U. S. Department of Transportation with 

jurisdiction over matters of railroad safety and research.

Frequency – Of a phenomenon that occurs periodically in time, the number of times that the quantity 

repeats itself in 1 second.

Frog – A track structure used at the intersection of two running rails to provide support for wheels and 

passageways for their flanges, thus permitting wheels on either rail to cross the other.

Gage (of track) – The distance between the gage lines, measured at right angles thereto.

Gage Line – A line 5/8-inch below the top of the center line of head of running rail or corresponding 

location of tread portion of other track structures along that side which is nearer the center of the 

tracks.

Gas-Turbine Electric Locomotive – A power unit in which a gas turbine drives electric generators 

supplying current to electric traction motors on the axles.

Grade Crossing – The point where a rail line and a motor vehicle road intersect.

Guideway – Supporting structure to form a track for rolling- or magnetically-levitated vehicles.

Head-End Power – A system of furnishing electric power for a complete railway train from a single 

generating plant in the power unit.

Hourly Average Sound Level – The time-averaged A-weighted sound level, over a 1-hour period, usually 

calculated between integral hours. Also known as L1h.

Idle – The speed at which an engine runs when it is not under load.

Intermodal Car – A rail car designed specifically for handling piggyback trailers or containers, or both.

Intermodal Traffic – Freight moving via at least two different modes of transport, e.g., truck-to-rail.

Jointed Rail – A system of joining rails with steel members designed to unite the abutting ends of 

contiguous rails.

L1h – see Hourly Average Sound Level

LAE – Power-averaged value of sound exposure within 10 dB of LAmax, sampled at a time interval of 5/3 

second. Used in Japan.
F-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

LAeq,P – Equivalent A-weighted sound-level, energy averaged over the time of passby (train length). Used 

in Europe.

LAeq,1h – Sound-pressure level, energy averaged over one hour. See also Hourly Average Sound Level. 

Used in Europe.

LAmax – Power-averaged “slow” maximum level (Lmax,s) of 20 consecutive train passbys. Used in Japan.

Ldn – The sound exposure level for a 24-hour day calculated by adding the sound exposure level obtained 

during the daytime (7 a.m. to 10 p.m.) to 10 times the sound exposure level obtained during the 

nighttime (10 p.m. to 7 a.m.). This unit is used throughout the U.S. for environmental impact 

assessment. Also written as DNL.

Leq – see Equivalent Level

Lmax(mean) – see LAeq,P (used in Scandinavia)

Lp,1h – see LAeq,1h

Lp,p – see Laeq,P

Locomotive – A self-propelled, non-revenue rail vehicle designed to convert electrical or mechanical 

energy into tractive effort to haul railway cars. (see also Power Unit)

Lead Unit – The first and controlling power unit in a series of locomotives pulling the same train.

Main Line – The principal line or lines of a railway.

Maglev – Magnetically-levitated vehicle; a vehicle or train of vehicles with guidance and propulsion 

provided by magnetic forces. Support can be provided by either a electrodynamic system (EDS) 

wherein a moving vehicle is lifted by magnetic forces induced in the guideway, or a 

electromagnetic system (EMS) wherein the magnetic lifting forces are actively energized in the 

guideway.

Maximum Sound Level – The highest exponential-time-average sound level, in decibels, that occurs 

during a stated time period. Also written as Lmax. The standardized time periods are 1 second for 

Lmax, slow and 0.125 second for Lmax, fast.

Multiple Unit (MU) – A term referring to the practice of coupling two or more power units or electric 

passenger cars together with provision for controlling the traction motors on all units from a single 

controller.
Appendix F: Glossary of Terms F-5

Noise – Any disagreeable or undesired sound or other audible disturbance.

Octave – The frequency interval between two sounds whose frequency ratio is 2.

Pantograph – A device for collecting current from an overhead conductor (catenary), consisting of a 

jointed frame operated by springs or compressed air and having a current collector at the top.

Peak Particle Velocity (PPV) – The peak signal value of an oscillating vibration velocity waveform. 

Usually expressed in inches/second.

Peak-to-Peak (P-P) Value – Of an oscillating quantity, the algebraic difference between the extreme 

values of the quantity.

Power Unit – A self-propelled vehicle, running on rails and having one or more electric motors that drive 

the wheels and thereby propel the locomotive and train. The motors obtain electrical energy either 

from a rail laid near to, but insulated from, the track rails, or from a wire suspended above the 

track. Contact with the wire is made by a pantograph mounted on top of the unit.

Radius of Curvature – A measure of the severity of a curve in a track structure based on the length of the 

radius of a circle that would be formed if the curve were continued.

Rail – A rolled steel shape, commonly a T-section, designed to be laid end to end in two parallel lines on 

cross ties or other suitable supports to form a track for railway rolling stock.

Receiver/Receptor – A stationary far-field position at which noise or vibration levels are specified. 

Retarder – A braking device, usually power-operated, built into a railway track to reduce the speed of cars 

by means of brake shoes which, when set in position, press against the sides of the lower portions 

of the wheels.

Right-of-Way – Lands or rights used or held for railroad operation.

Root Mean Square (RMS) – The average or "mean" level of an oscillating waveform. Obtained by 

squaring the value of amplitudes at each instant of time. The squared values are then added and 

averaged over the sample time.

SEL – see Sound Exposure Level

Siding – A track auxiliary to the main track for meeting or passing trains.
F-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Sound Exposure Level – The level of sound accumulated over a given time interval or event. 

Technically, the sound exposure level is the level of the time-integrated mean square A-weighted 

sound for a stated time interval or event, with a reference time of one second. Also written as SEL.

Sound – A physical disturbance in a medium that is capable of being detected by the human ear.

Sub-Ballast – Any material of a superior character, which is spread on the finished subgrade of the 

roadbed and below the top-ballast, to provide better drainage, prevent upheaval by frost, and better 

distribute the load over the roadbed.

Subgrade – The finished surface of the roadbed below the ballast and track.

Switch – A track structure used to divert rolling stock from one track to another.

Tangent Track – Track without curvature.

Terminal – An assemblage of facilities provided by a railway at a terminus or at an intermediate point for 

the handling of passengers or freight and the receiving, classifying, assembling and dispatching of 

trains.

Top-Ballast – Any material of a superior character spread over a sub-ballast to support the track structure, 

distribute the load to the sub-ballast, and provide a good initial drainage.

Turbulent Boundary Layer – Fluctuations in the air adjacent to the body of a vehicle moving at high 

speed.

Track Crossing – A structure, used where one track crosses another at grade, and consisting of four 

connected frogs.

Track – An assembly of rail, ties and fastenings over which cars, locomotives, and trains are moved.

Traction Motor – A specially designed direct current series-wound motor mounted on the trucks of 

locomotives and self-propelled car to drive the axles.

Trainset – A group of coupled cars including at least one power unit.

Truck – The complete assembly of parts including wheels, axles, bearings, side frames, bolster, brake 

rigging, springs and all associated connecting components, the function of which is to provide 

support, mobility and guidance to a railroad car or locomotive.

Turnout – An arrangement of a switch and a frog with closure rails, by means of which rolling stock may 

be diverted from one track to another.
Appendix F: Glossary of Terms F-7

VdB – see Vibration Velocity Level

Vibration Velocity Level – 10 times the common logarithm of the ratio of the square of the amplitude of 

the vibration velocity to the square of the amplitude of the reference velocity. Also written as VdB.

Vibration – An oscillation wherein the quantity is a parameter that defines the motion of a mechanical 

system.

Vortex Shedding – A flow separation (see definition above) wherein the air departs periodically in a 

spinning motion.

Wheel Flat – A localized flat area on a steel wheel of a rail vehicle, usually caused by skidding on steel 

rails, causing a discontinuity in the wheel radius.

Wheel Squeal – The noise produced by wheel-rail interaction, particularly on a curve where the radius of 

curvature is smaller than allowed by the separation of the axles in a wheel set.

Wye – A triangular arrangement of tracks on which locomotives, cars and trains may be turned.

Yard – A system of tracks within defined limits provided for making up trains, storing cars, and other 

purposes, over which movements not authorized by time table or by train-order may be made, 

subject to prescribed signals and rules, or special instructions.
F-8 High-Speed Ground Transportation Noise and Vibration Impact Assessment
Appendix G: Background Information for FRA Noise Screening Table G-1

APPENDIX G - BACKGROUND INFORMATION FOR FRA NOISE SCREENING 

TABLE

Screening method requires information regarding: 

1. Project setting 

a. Shared with railroad corridor (primarily freight trains)

b. Shared with highway corridor

c. New transportation corridor

2. Existing Ambient Noise Conditions

a. Urban/Noisy Suburban (U/NS) 

b. Quiet Suburban/Rural (QS/R)

3. Technology

a. Steel wheel high speed trains

b. Maglev trains

Assumptions regarding the development of screening distances:

1. Railroad Corridor has 10 daytime and 2 nighttime freight trains with an average of 1 

locomotive and 40 freight cars running at 55 mph. Using the Federal Transit Administration 

(FTA) noise spreadsheet, the Ldn for this condition would be 65 dBA at 50 feet from track 

centerline. Noise levels in the corridor are assumed to follow a soft ground propagation rate of 

4.5 dB per distance doubling, or {65–15 Log (D/50)}. 

2. Highway Corridor has a 4 lane highway with a peak hour volume of 1,450 vehicles, made up of 

95% automobiles, 2% medium trucks, and 3% heavy trucks. “TNM Lookup” gives Leq = 72 

dBA at 50 feet for this condition. FTA manual provides an estimated Ldn = PH Leq – 2 dB, or 

70 dBA for a typical highway traffic pattern. Again, a soft ground propagation rate is assumed, 

or Ldn = 70 – 15 Log (D/50).
G-2 High-Speed Ground Transportation Noise and Vibration Impact Assessment

3. New Transportation Corridor is assumed to have no existing transportation facilities other than 

local roads and streets in urban, suburban and rural areas. Noise level is the ambient noise 

associated with the land use.

4. Existing ambient noise is based on the levels identified by US Environmental Protection Agency 

(“Levels Document” p.14) where “small town and quiet suburban” noise levels are given the 

rating of 50 dB Ldn and “urban” is given the rating of 60 dB Ldn. The foregoing descriptions are 

modified and applied to the categories of “Quiet Suburban/Rural” at 50 dB Ldn, and 

“Urban/Noisy Suburban” at 60 dB Ldn. These Ldn values are the noise levels found uniformly in 

the areas, except where the noise environment is affected by the transportation corridors 

described above – railroad and highway. In the corridor cases, the railroad noise or highway 

noise is added to the ambient noise, with the result that close to the transportation noise source the 

ambient noise is determined by the transportation and far from the source the ambient is attained. 

The results are shown in the figures below.

Existing Ambient Noise in Rural Areas

40

45

50

55

60

65

70

75

0 200 400 600 800 1000

Distance from Centerline (ft)

Ldn, dBA

Railroad Corridor

Highway Corridor

New Corridor
Appendix G: Background Information for FRA Noise Screening Table G-3

Existing Ambient Noise in Urban Areas 

40

45

50

55

60

65

70

75

0 200 400 600 800 1000

Distance from Centerline (ft)

Ldn, dBA

Railroad Corridor

Highway Corridor

New Corridor

5. Project Noise is based on the technology selected for assessment – steel wheel high-speed trains 

and maglev trains, and two speed regimes for each. Noise from each technology is computed 

using the Federal Railroad Administration noise computation spreadsheet with the following 

input data based on typical conditions expected for a high speed rail project. 

a. Steel Wheel Technology is represented by trains made up of 2 power cars, 10 coaches, 

and a service of 45 daytime trains and 12 night trains. Two speed regimes are assumed, 

Regime II at 100 mph; and Regime III at 180 mph. The FRA model gives Ldn = 70 dBA 

at 50 ft. for Regime II and 75 dBA for Regime III under the foregoing conditions. 

Soft ground propagation was assumed for open terrain – 4.5 dB per distance doubling, or 

{-15 Log (D/50)}. An added condition is the propagation in built-up areas, where the 

rows of buildings provide shielding. This condition applie s in urban and densely 

populated suburban locations. Rows of buildings are assumed to occur at 200, 400, 600, 

800, and 1000 feet from track centerline in urban settings. A shielding factor of 3 dB was 

subtracted at the first row of buildings (200 ft.) and 1.5 dB subtracted for each successive 

row of buildings.
G-4 High-Speed Ground Transportation Noise and Vibration Impact Assessment

Steel Wheel HSR in Speed Regime II

30.0

35.0

40.0

45.0

50.0

55.0

60.0

65.0

70.0

75.0

0 500 1000 1500

Distance from Centerline (ft.)

Ldn, dBA

Steel Wheel -

Unobstructed 

Steel Wheel - Urban

Buildings

Steel Wheel HSR in Speed Regime III

30.0

35.0

40.0

45.0

50.0

55.0

60.0

65.0

70.0

75.0

80.0

0 500 1000 1500

Distance from Centerline (ft.)

Ldn, dBA

Steel Wheel -

Unobstructed 

Steel Wheel - Urban

Buildings

b. Maglev Technology is represented by trains made up of 10 cars, and a service of 45 

daytime trains and 12 night trains, the same as the steel wheel technology. Again, two 

speed regimes are assumed but with a higher speed in Regime III than steel wheel to 

account for the maglev’s higher speed capability: Regime II at 100 mph and Regime III 

at 200 mph. FRA spreadsheet model gives the result of Ldn = 60 dBA at 50 ft for 

Regime II and 72 dBA for Regime III under these conditions. 

Soft ground propagation was assumed for open terrain – 4.5 dB per distance doubling, or 

{-15 Log (D/50)}. An added condition is the propagation in built-up areas, where the 
Appendix G: Background Information for FRA Noise Screening Table G-5

rows of buildings provide shielding. This condition applies in urban and densely 

populated suburban locations. Rows of buildings are assumed to occur at 200, 400, 600, 

800, and 1000 feet from track centerline in urban settings. A shielding factor of 3 dB was 

subtracted at the first row of buildings (200 ft.) and 1.5 dB subtracted for each successive 

row of buildings.

Maglev in Speed Regime II

25

30

35

40

45

50

55

60

65

0 200 400 600 800 1000 1200

Distance from Centerline (ft.)

Ldn, dBA

Maglev -Unobstructed 

Maglev - Urban

Buildings

Maglev in Speed Regime III

25

30

35

40

45

50

55

60

65

70

75

0 200 400 600 800 1000 1200

Distance from Centerline (ft.)

Ldn, dBA

Maglev -Unobstructed 

Maglev - Urban

Buildings
G-6 High-Speed Ground Transportation Noise and Vibration Impact Assessment

6. Results

 The projected noise levels from the steel wheel and maglev systems are compared with FRA noise 

impact criteria in order to determine the distance within which noise impact could occur. The noise 

impact criteria are ambient-based, and impact values are tabulated in Chapter 3. Given the existing noise 

level, the project noise level is listed for impact and severe impact. For the screening process, only the 

impact level is used in order to provide an upper bound on the potential for impact. 

The results of the exercise are shown in the table below. Copies of spreadsheets with all the baseline data 

are attached.

Screening Distance in Feet for Project Type 

and Speed Regime*

Steel-Wheeled Maglev

Corridor 

Type

Existing Noise

Environment

Reg. II Reg. III Reg. II Reg. III

Railroad U/NS –unobstructed 300 ft. 700 ft. 50 ft. 400 ft.

U/NS – intervening buildings** 200 300 50 250

QS/R 500 1200 50 700

Highway U/NS –unobstructed 250 600 50 400

U/NS – intervening buildings** 200 350 50 250

QS/R 400 1100 50 600

New U/NS –unobstructed 350 700 75 450

U/NS – intervening buildings** 250 350 75 300

QS/R 600 1300 150 800

*Measured from centerline of guideway or rail corridor. 

Minimum distance is assumed to be 50 ft. 

** Rows of buildings assumed to be at 200 ft., 400 ft., 600 ft., 800 ft. and 1000 ft. 

parallel to guideway.

U = Urban; NS = Noisy Suburban; QS = Quiet Suburban; R = Rural.

.