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sss arnMrvK.rsss'.puB- NO.eS-3311 V198S C.Z NBO-ruo- ^ ^ ^ ^ inooik tfb-331

(DoT)

Guidelines for the Prevention of

Traffic Noise Problems

NBS

PUBLICATIONS

Fred F. Rudder, Jr. Simone L. Yaniv

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Physics Division

Gaithersburg, MD 20899

April 1985

Issued January 1986

QC

100

U56

Prepared for; U.S. Department of Transportation

Federal Highway Administration

of Implementation, HRT-10

er-Fairbank Research Center

) Georgetown Pike

san, Virginia 22101

86-3311

1986

C. 2

RESE^SCH INFOKMATION CENTEK

NBSIR 86-331 1 (DoT)

/ »

GUIDELINES FOR THE PREVENTION OF

TRAFFIC NOISE PROBLEMS

' r ^ /-Tv

Fred F. Rudder, Jr. Simone L Yanlv

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Physics Division

Gaithersburg, MD 20899

April 1985

Issued January 1986

Prepared for; U.S. Department of Transportation

Federal Highway Administration

Office of Implementation, HRT-10

Turner-Fairbank Research Center

6300 Georgetown Pike

McLean, Virginia 22101

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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TABLE OF CONTENTS

Page

LIST OF FIGURES vli

LIST OF TABLES xv

EXECUTIVE SUMMARY 1

1. OVERVIEW OF GUIDELINES 3

1.1 CHARACTERIZATION OF THE OUTDOOR ENVIRONEMNT 3

Notes on Sound Levels 4

Notes on Prediction and Propagation of Noise 9

1.2 CHARACTERIZATION OF THE INDOOR NOISE ENVIRONMENT 9

Notes on Indoor Noise Characteristics 10

1.3 ESTIMATION OF FUTURE CONDITIONS 10

Notes on Future Conditions 10

1.4 MITIGATION TECHNIQUES 11

Notes on Noise Mitigation 12

1.5 NOISE-COMPATIBLE LAND USE DEVELOPMMENT 15

2. THE OUTDOOR NOISE ENVIRONMENT 16

2.1 HIGHWAY TRAFFIC NOISE PREDICTION 16

Noise Prediction Procedure 17

Example 1 17

Comments on the Lookup Tables 24

Representative Traffic Flow Data 24

2.2 RAILWAY NOISE PREDICTION 28

Necessary Information 28

Characterization of the Average Train 28

Example 2 32

Noise Prediction Procedure 32

Example 3 33

Combining Sound Levels 41

Example 4 46

2.3 AIRCRAFT NOISE PREDICTION 48

iii
TABLE OF CONTENTS (Continued)

Page

The Noise Source 49

Source-Receiver Geometry 49

Noise Propagation 51

Number of Operation 51

Noise Exposure of Land Areas 52

2.4 EXISTING NOISE SOURCES 52

2.5 ESTIMATION OF FUTURE CONDITIONS 53

2.6 NOISE PREDICTION WORKSHEETS 55

Highway Traffic Noise Prediction 55

Diesel-Electric Railway Noise Prediction 56

Existing Noise Levels 57

3. MITIGATION TECHNIQUES 62

Existing Noise Levels 62

Physical Aspects of Outdoor Noise Mitigation 63

3.1 OUTDOOR NOISE MITIGATION 63

Highway Traffic Noise Barriers 67

Estimation of Barriers Mitigation Effectiveness 67

Example 5 69

Barrier Construction 71

Natural Terrain and Berms 71

Vegetation 74

Privacy Fences and Courtyards 74

Buildings as Noise Barriers 76

3.2 INDOOR NOISE MITIGATION 76

Terminology 78

A-weighted Sound Transmission Loss 80

Sound Transmission Loss of Building Construction 81

Composite Envelope Construction 91

Outdoor Sound Field 92

Indoor Sound Field 93

Sound Absorption of the Room 94

Putting It All Together 94

Estimation of the Envelope Noise Isolation 95

Example 6 97

Example 7 100

Example 8 107

Example 9 113

iv
TABLE OF CONTENTS (Continued)

Page

Degradation of Noise Isolation Performance 115

Open Window Conditions 118

Screened Balconies and Courtyards 120

3.3 INDOOR NOISE MITIGATION WORKSHEETS 122

Use of Worksheets 122

Several Noise Sources 125

4. NOISE COMPATIBLE DEVELOPMENT 132

4.1 ENVIRONMENTAL NOISE LEVELS COMPATIBLE WITH VARIOUS LAND

USES 132

4.2 TECHNIQUES FOR LAND USE CONTROL 134

Regulatory Controls of Land Use 138

Non-regulatory Controls 141

5. REFERENCES 143

Appendix A. NOISE PREDICTION MODELS 149

A.l Highway Traffic Noise Prediction Model 149

A. 2 Railway Noise Prediction Model 155

Warning Horn Noise 156

Diesel-Electric Pass-By Noise 158

Combining Sound Levels 162

Appendix B. OUTDOOR NOISE MITIGATION 163

B. l Highway Noise Barriers 163

Clear Site Condition 163

Site Conditions with Barriers Installed 163

Barrier Insertion Loss 167

Barrier Diffraction 167

Barrier Attenuation Tables 169

B.2 Shielding Provided by Buildings 169

V
TABLE OF CONTENTS (Continued)

Page

Appendix C. A-WEIGHTED NOISE ISOLATION OF BUILDINGS 173

C.l Normalized Noise Spectra 173

C.2 Normalized Sound Transmission Loss 176

C*3 A-Weighted Sound Transmission Loss 179

C.4 Evaluation of the Procedure 180

C.5 Open window Conditions 182

C.6 Formulation of Worksheets 184

Appendix D. ENVIRONMENTAL NOISE DESCRIPTORS FOR NOISE - COMPATIBLE

LAND USE PLANNING 189

Appendix’ E. AVERAGE SOUND TRANSMISSION LOSS OF EXTERIOR BUILDING

ELEMENTS 194

Vi
LIST OF FIGURES

Page

Figure 1 . Source-receiver Geometry for the Present Guidelines 7

Figure 2. Typical Site Condition for Highway Traffic Noise Prediction .. 8

Figure 3. Completed Worksheet for Highway Traffic Noise Prediction:

Hard Site Conditions 19

Figure 4. Completed Worksheet for Highway Traffic Noise Prediction:

Soft Site Conditions 20

Figure 5. Plan View of Site Describing Distances Required to Predict

Sound Levels from Railway Trains 29

Figure 6. Completed Data Sheet for Railway Noise Prediction:

Example 2 34

Figure 7. Completed Data Sheet for Railway Pass-By Noise Prediction:

Example 3 35

Figure 8. Completed Worksheet for Railway Warning Horn Noise Prediction

and Combined Railway Noise Prediction: Example 3 42

Figure 9 . Source-receiver Geometry for Estimating Total Acoustic

Energy at the Exterior Surfaces of a Building 47

Figure 10. Basic Situations for the Calculations of DNL Due to Aircraft

Operations (Ref. 22) 50

Figure 11. Propagation of Highway Noise at Receiver: Site Insertion Loss 64

Figure 12. Illustration of Diffraction, Reflection and Scattering of

Sound by Objects Next to Highway 65

Figure 13. Site Noise Exposure for Combined Noise Sources 66

Figure 14 . Source-Barrier-Receiver Relationship 68

Figure 15. Plan View of the Site Illustrating Shielding by Highway Noise

Barriers 72

Figure 16. Conceptual Examples of Privacy Fences and Courtyards 75

Figure 17. Buildings as Noise Barriers 77

Figure 18. Factors Affecting the A-Weighted Noise Level Reduction of the

. Building Envelope 79

vii
LIST OF FIGURES (Continued)

Page

Figure 19. Acoustically Identical Envelope Members (S denotes surface

area and TL denotes sound transmission loss) 96

Figure 20. Completed Worksheet for Calculating Adjusted TL values of

Elements: Example 6 98

Figure 21. Completed Worksheet for Calculating Composite TL of

Envelope Members: Example 6 99

Figure 22. Completed Worksheet for Calculating Adjusted TL values of

Elements: Example 7 101

Figure 23. Completed Worksheet for Calculating Composite TL of Envelope

Members: Example 7 102

Figure 24. Noise Source Exposure Adjustment for Building Envelope 103

Figure 25. Angle of Incidence Adjustment for Worksheet VII 104

Figure 26. Building Location for Example Problem Illustrating

Calculation of Building Envelope Noise Isolation 106

Figure 27. Completed Worksheet for Calculating Adjusted TL Values for

Each Envelope Member: Example 8, Highway Noise 109

Figure 28. Completed Worksheet for Calculating Adjusted TL Values for

Each Envelope Member: Example 8, Aircraft Noise 110

Figure 29. Completed Worksheet for Calculating Indoor Sound Level

Contribution from Each Envelope Member: Example 8,

Highway Traffic Noise Ill

Figure 30. Completed Worksheet for Calculating Indoor Sound Level

Contribution for Each Envelope Member: Example 8,

Aircraft Noise 112

Figure 31. Building Location Relative to Two Intersecting Highways:

Example 9 114

Figure 32. Purpose of Worksheets for Calculating Building Envelope

Noise Isolation 123

Figure 33. Summary of the Effects of Community Noise on People as a Function of Day-Night Average Sound Level 133

Figure 34. Pavement-Receiver Geometry for Highway Traffic Noise

Prediction 150

vili
LIST OF FIGURES (Continued)

Page

Figure 35. Source-Receiver Geometry and Single Event Definition

for Predicting Railway Warning Horn Noise Exposure 157

Figure 36. Source-Receiver Geometry for Diesel-Electric Railway Pass-By

Noise Prediction 159

Figure 37. Geometric Nomenclature for Thin Screen Barrier: Section

Through Site Perpendicular to Highway and Containing the

Receiver Location 164

Figure 38. Geometric Nomenclature Relating Noise Source Location to the

Reference Plane Perpendicular to the Highway and Containing

the Receiver Location 165

Figure 39. Geometric Nomenclature Relating the Location of an Element

of the Line Source to the Receiver Plane 166

Figure 40. Example of Barrier Insertion Loss Tabulation 170

Figure 41. Nomenclature for Insertion Loss Estimates Provided by Buildings 172

Figure 42. Normalized Spectrum for Component Noise 177

Figure 43. Normalized Spectrxam for Highway Traffic Noise 178

Figure 44. Values of the Term C^^j^ 181

Figure 45. Average and Range of Sound Transmission Loss of Metal

and Curtain Walls Consisting of 2 Sheets of Galvanized Steel

with Insulation and having an Area Weight of Less Than

6 Ibs/ft^ 195

Figure 46. Average and Range of Sound Transmission Loss of 4-7 in

Masonry Walls Consisting of Either 4x8x16 Concrete Blocks

or Mortared Bricks Without Finish 196

Figure 47. Average and Range of Transmission Loss of 4-7 in Masonry Walls

Consisting of 4x8x13 3-Cell Concrete Blocks with Resilient

Channels 24-in o.c. and 1/2-in Plaster Board 197

Figure 48. Average and Range of Sound Transmission Loss of 7/8-in Stuccoed

Wall with No. 15 Felt Building Paper and 1-in wire mesh with

2x4 Wood Studs 16-in o.c. with Fiberglas Building Insulation and

1/2-in Gypsum Board Screwed to Channel 198

Figure 49. Average and Range of Sound Transmission Loss of Dense Concrete

Walls 8-in Thick Consisting of 3-Cell Blocks with Perimeter

Sealed 199

ix
LIST OF FIGURES (Continued)

Figure 50.

Figure 51.

Figure 52.

Figure 53.

Figure 54.

Figure 55.

Figure 56.

Figure 57.

Figure 58.

Average and Range of Sound Transmission Loss of 8-in Thick

Masonry Walls Consisting of Either Bricks Mortared Together

or 3-Cell Concrete Blocks with Block Filler with 1/2-in

Plaster and Finished with Latex Paint

Average and Range of Sound Transmission Loss of Masonry

Walls 8-in Thick Consisting of 18x16x8 3-Cell Concrete Blocks

with Resilient Channels 24-in o.c. with 1/2-in Plaster Board

and Paint on Both Sides

Average and Range of Sound Transmission Loss of Double

Brick Walls Consisting of 4-1/2-in Walls Separated by 2-4-in

Cavity with Wire Ties and 1/2-ln Plasterboard on Both Sides .

Average and Range of Sound Transmission Loss of Light Frame

Wood Wall with 2x4 Wood Studs 16-in o.c., 2-3-in Insulation

and Finish with 1/2-in gypsum board

Average and Range of Sound Transmission Loss of Light Frame

Walls with Wood Siding, 2x4 Wood Studs with Insulation,

Resilient Channels 24-in o.c.. Finished with 1/2-in Gypsum

Board and Penetrated by 25-30 Percent Glass

Average and Range of Sound Transmission Loss of Light Frame

Walls with Wood Siding, 2x4 Studs 16-o.c., with Insulation,

Resilient Channels 24-in o.c.. Finished with 1/2-in Gypsum

Board and Penetrated by 25 to 30 Percent Single Glazed

Sealed Glass with Storm Sash

Average and Range of Sound Transmission Loss of Light Frame

Walls with Either Brick Veneer or Wood Siding, 2x4 Wood Studs

16-in o.c. , with Fiberglass Insulation and Penetrated by a 10-15 Percent Single Strength Glazed Sealed Window

Average and Range of Sound Transmission Loss of Light Frame

Walls with Either Wood Siding or Brick Veneer, 2x4 Wood Studs

Resilient Channels 24-in o.c. and 1/2-in Gypsum Board but no Insulation and Penetrated by 25-30 Percent Single Glazed

Sealed Glass

Average and Range of Sound Transmission Loss of Light Frame

Walls with Either Wood Siding or Brick Veneer, 2x4 Studs

with Insulation, Resilient Channels 24-in o.c., 1/2-in

Gypsum Board and Penetrated by 25-30 Percent Glazed Sealed

Glass with Storm Sash

Page

200

201

202

203

204

205

206

207

208

X
LIST OF FIGURES (Continued)

Page

Figure 59.

Figure 60.

Figure 61.

Figure 62.

Figure 63.

Figure 64.

Figure 65.

Figure 66.

Figure 67.

Figure 68.

Figure 69.

Average and Range of Sound Transmission Loss of 3/32-7/16-in

Thick Single Glazed Sealed Windows 209

Average and Range of Sound Transmission Loss of 3/32-7/16-in

Thick Single Glazed Unsealed Windows 210

Average and Range of Sound Transmission Loss of Single

Strength Panes with Storm Sashes Unsealed 211

Average and Range of Sound Transmission Loss of Single

Strength Sealed Windows with Storm Sashes 212

Average and Range of Sound Transmission Loss of Double Glazed

Sealed Windows Consisting of Parallel Panes of the Same

Thickness Contained within a Range of 3/32-3/8-in, Mounted

in one Sash with an Interpane Spacing of Less than 1/2-in ... 213

Average and Range of Sound Transmission Loss of Double Glazed

Sealed Windows Consisting of Two Panes of the Same Thickness

Contained within a Range of 3/32-1/8-ln Mounted in Parallel

in one Sash with an Interpane Spacing of Less than 1/2-in ... 214

Average and Range of Sound Transmission Loss of Double Glazed

Sealed Windows Consisting of Panes of Different Thicknesses,

1/8-1/4-in Mounted in one Sash in Parallel with an Interpane

Spacing of 1/2-3/4-in 215

Average and Range of Sound Transmission Loss of Double Glazed

Sealed Windows Consisting of Panes of Different Thicknesses,

1/8 and 1/4-in Mounted in one Sash not in Parallel with

Maximum Interpane Spacing of 3/4-in and Minimum Interpane

Spacing of 1/4-in 216

Average and Range of Sound Transmission Loss of Double Glazed

Sealed Windows Consisting of Panes of the Same Thicknesses,

Contained within a Range of 5/32-1/4-in Mounted in Parallel

in Sashes with an Interpane Spacing of 2-1/2 to 4-in 217

Average and Range of Sound Transmission Loss of Double Glazed

Sealed Windows Consisting of Panes of the Same Thicknesses,

Contained within a Range of 5/32-1/4 in Mounted in Parallel

in Sashes with an Interpane Spacing of 3-6-in 218

Average and Range of Sound Transmission Loss of Double Glazed

Sealed Windows Consisting of Parallel Panes of the Same Thicknesses, Contained within a Range of 5/32-1/4-in Mounted in 2 Sashes in Parallel with a Interpane Spacing Greater than 6-ln 219

xi
LIST OF FIGURES (Continued)

Figure 70. Average and Range of Sound Transmision Loss of Double Glazed

Sealed Windows Consisting of Panes of Different Thicknesses

each 1/8 and 1/4 -in Mounted in Parallel in Two Sashes with

an Interpane Spacing Between 1 and 1-1/2-in

Figure 71. Average and Range of Sound Transmision Loss of Double Glazed

Sealed Windows Consisting of Panes of Different Thicknesses,

each 1/8 and 1/4-in, Mounted in Parallel in 2 Sashes with

an Interpane Spacing Between 1-1/2 and 2-in

Figure 72. Average and Range of Sound Transmision Loss of Double Glazed

Sealed Windows Consisting of Panes of Different Thicknesses,

each 1/8 and 1/4-in, Mounted in Parallel in 2 Sashes with

an Interpane Spacing Between 2-1/2 and 6-in

Figure 73. Average and Range of Sound Transmision Loss of Double Glazed

Sealed Windows Consisting of Panes of Different Thicknesses

each 1/8 and 1/4-ln Mounted in 2 Sashes not Parallel with

a Maximum Interpane Spacing of 3-in and a Minimum Interpane

Spacing of 1-ln

Figure 74. Average and Range of Sound Transmission Loss of Double Glazed

Sealed Windows Consisting of Panes of Different Thicknesses

Each 1/8 and 1/4-in, Mounted in 2 Sashes not in Parallel with

a Maximum Interpane Spacing of 3-in and a Minimum Interpane

Spacing of 2-in

Figure 75. Average and Range of Sound Transmission Loss of Double Glazed

Sealed Windows Consisting of Panes of Different Thicknesses

Each 1/8 and 1/4-in, Mounted in 2 Sashes not in Parallel with

a Maximum Interpane Spacing of 6-in and Minimum Interpane

Spacing of 2-ln

Figure 76. Average and Range of Sound Transmission Loss of Double Glazed

Sealed Windows Consisting of Panes of the Thicknesses Contained

within a Range of 1/32-1/8-in, Mounted in 2 Sashes not in

Parallel with a Maximum Interpane Spacing of 3-in and Minimum

Interpane Spacing of 1-ln

Figure 77. Average and Range of Sound Transmission Loss of Double Glazed

Sealed Windows Consisting of Panes of the Same Thickness

Contained within a Range of 1/8-1/3-in, Mounted in 2 Sashes

Not in Parallel with a Maximum Interpane Spacing of 6-in

and a Minimum Interpane Spacing of 2-in

Page

220

221

222

223

224

225

226

227

xii
LIST OF FIGURES (Continued)

Page

Figure 78. Average and Range of Sound Transmission Loss of Triple Glazed

Sealed Windows Consisting of 1/8-in Panes Mounted in 1 Wood

Sash with Interpane Spacing Ranging from 1/8-13/32-in 228

Figure 79. Average and Range of Sound Transmission Loss of Triple

Glazed Sealed Windows Consisting of 2 Panes 1/8-ln thick

Mounted in 1 Wood Sash with an Interpane Spacing of 1/4-in

and a Metal Spacer and with a Third Pane 1/8-in Thick

Mounted in a Separate Sash with a 3/4-2-ln Space 229

Figure 80. Average and Range of Sound Transmission Loss of Triple

Glazed Sealed Windows Consisting of 2 Panes 1/8-in thick

Mounted in 1 Wood Sash with an Interpane Space of 1/4-in

and a Metal Spacer and with the Third Pane Consisting of

Either a 1/8 or 1/4-in Thick Glass Mounted in a Separate Sash

3/4-2-ln Away 230

Figure 81. Average and Range of Sound Transmission Loss of Triple Glazed

Sealed Windows Consisting of 2 Panes 1/8-in Thick Mounted in

1 Sash with an Interpane Spacing of 1/4-in and a Metal Spacer

and with the Third Pane Consisting of 1/4-in Glass Mounted

1-2-in Away in a Separate Sash 231

Figure 82. Average and Range of Sound Transmission Loss of Triple Glazed

Sealed Windows Consisting of 1/8-ln Thick Panes Mounted in 2

Wood Sashes with a First Interpane Spacing of 1/4-in and

a Second Interpane Spacing of 4-in 232

Figure 83. Average and Range of Sound Transmission Loss of Hollow Core

Wood Doors with Weather Stripping 233

Figure 84. Average and Range of Sound Transmission Loss of Solid Core

Wood Doors with Weather Stripping 234

Figure 85. Average and Range of Sound Transmission Loss of Weather

Stripped and Sealed Solid Core Wood Doors 23 5

Figure 86. Average and Range of Sound Transmission Loss of Weather

Stripped Glass Containing Doors 236

Figure 87. Average and Range of Sound Transmission Loss of Weather

Stripped Metal Doors 237

Figure 88. Average and Range of Sound Transmission Loss of Weather

Stripped and Sealed Solid Core Wood Doors with Aluminum Sealed

Storm Door Fitted with a Single Glazed Window 238

xiii
LIST OF FIGURES (Continued)

Page

Figure 89. Average and Range of Sound Transmission Loss of Acoustical

Doors 239

Figure 90. Average and Range of Sound Transmission Loss of Pitched

Wood Frame Domestic Roof with Sealed Perimeter but Without

Insulation or Ceiling 240

Figure 91. Average and Range of Sound Transmission Loss of Pitched

Wood Frame Domestic Roof Sealed Perimeter and Insulation

Between roof Joists Without Ceiling 241

Figure 92. Average and Range of Sound Transmission Loss of Pitched

Wood Frame Domestic Roof with Sealed Perimeter and Plaster

Celling but Without Insulation 242

Figure 93. Average and Range of Sound Transmission Loss of Pitched

Wood Frame Domestic Roof with Insulation Between Joists,

Sealed Perimeter and Plaster Ceiling 243

Figure 94. Flat Galvanized Steel Deck Domestic Roof with Plaster

Board Ceiling and Insulation 244

Figure 95. Flat Galvanized Steel Deck Domestic Roof with Plaster

Board Celling Without any Insulation 245

xiv
LIST OF TABLES

Page

Table 1. Suggested Land Use Compatibility Guidelines: Residential

Land Use 5

Table 2. Range of L^jn Decreases for Various Mitigation Techniques as Estimated Using These Guidelines 13

Table 3. Mitigation Effectiveness for Outdoor and Indoor Criteria

for Residential Land Use 14

Table 4. Traffic Flow Reference Noise Levels in dB 21

Table 5. Traffic Noise Adjustment for AADT and Nighttime Conditions

in dB 25

Table 6. Traffic Noise Adjustment for Distance: Hard Site in dB 26

Table 7. Traffic Noise Adjustment for Distance: Soft Site in dB 27

Table 8. Representative Values of Annual Average Daily Traffic, AADT,

Vehicles Per 24 Hours (1976) 30

Table 9. Representative Values of F^ and F^ as Estimated from Ref. 19

Data 31

Table 10. Reference Sound Level for Railway Pass-By Operations in dB .. 36

Table 11. Sound Level Adjustment for Railway Pass-By Operations:

Total Number of Trains Per Day 38

Table 12. Sound Level Adjustment for Railway Noise: Fraction of Total

Events During the Night 39

Table 13. Sound Level Adjustment for Railway Pass-By Noise: Distance

Away from the Track Centerline 40

Table 14. Reference Sound Level: Railway Warning Horn in dB 43

Table 15. Sound Level Adjustment for Railway Warning Horn in dB: Total

Number of Trains and Train Speed 44

Table 16. Table for Combining Sound Levels 45

Table 17. Empirical Relationships Among Population Density, DNL, and

Nighttime Measures of the Existing Noise Levels 54

Table 18. Average Barrier Insertion Loss + Adjustment in dB for Highway

Traffic Noise Source with Receiver Height at 5 ft 70

XV
LIST OF TABLES (Continued)

Page

Table 19. Materials for Use in Barrier Construction 73

Table 20. Average A-Weighted Sound Transmission Loss of Exterior Walls .. 82

Table 21 . Average A-Weighted Sound Transmission Loss of Exterior Walls

With Windows 83

Table 22 . Average A-Welghted Sound Transmission Loss of Single-Glazed

Windows 84

Table 23 . Average A-Weighted Sound Transmission Loss of Double-Glazed

Windows 85

Table 24. Average A-Weighted Sound Transmission Loss of Triple-Glazed

Windows 87

Table 25 . Average A-Weighted Sound Transmission Loss of Doors 88

Table 26. Average A-Weighted Sound Transmission Loss of Domestic Roofs .. 89

Table 27. Summary Tabulation of Calculations for Example Problem Number 9 116

Table 28. Summary of Steps for Calculating the Building Envelope Noise

Level Reduction 117

Table 29. Values of the Adjustment Ag, dB, for Worksheet V 127

Table 30. Values of the Adjustment A^,, dB, for Worksheet VI 129

Table 31 . Change in the Envelope Member TL Due to Cracks and Gaps in

the Construction 119

Table 32 . Average Values of Building Envelope Noise Isolation for

Combined Open/ Closed Window Conditions 121

Table 33. Effects of Noise on People 135

Table 34. Environmental Noise Levels Compatible with Various Land Uses .. 136

Table 35. Techniques for Local and Land Use Control 137

Table 36. Outdoor-to-Indoor Noise Isolation Requirements Contained in

the EPA Model Noise Control Code Specification 140

Table 37 . Normalized A-Weighted Spectra 175

Table 38 . Comparison Between Direct and Approximate Calculations of

A-Weighted Noise Prediction: Highway Noise Spectrum 183

xvi
EXECUTIVE SUMMARY

The purpose of these guidelines is to assist local authorities in the

identification of potential traffic noise problems and the noise-compatible

development of property adjacent to highways. The noise generated by highway traffic is the most generally pervasive environmental noise source within a

a community. However, noise-compatible land development must recognize environmental noise sources other than highway traffic noise to ensure compatibility

between the total noise environment and the expected land use. These guidelines, therefore, also include the noise generated by railway operations and

aircraft noise in the assessment process.

The guidelines are quantitative rather than qualitative in scope. Calculations are required to conduct an assessment of a specific site. The

calculations are not difficult and may be performed with a pocket calculator.

The guidelines are intended to be a complete document in that all the

necessary information is included along with step-by-step instructions and

examples illustrating the methods. Specialized training is not required to

utilize these guidelines.

The guideline format is based upon the application of local data to

evaluate present and future conditions for a proposed land development.

These data are used to predict the noise environment at a site and to

estimate the effectiveness of possible noise mitigation measures. Since

the guidelines are intended only to identify possible noise problems, the

methods used are approximate. However, these approximations are consistent

with accepted engineering practices, and the resulting estimates identify

potential problems and their severity. Once this identification has been

accomplished, the developer or local authority may perform additional estimates

using more refined methods to justify the proposed action. References to

these more refined methods are Included in the guidelines, as appropriate.

Finally, these guidelines are not intended to be a refined design tool

for evaluating alternatives, although one may use the methods for preliminary

design evaluation. Following the steps included in the guidelines, the

noise exposure of land may be estimated for the following sources and

conditions

:

• Multi-lane highway traffic for uniform traffic flow within 1500 ft

of the pavement;

• Diesel-electric railway trains, including warning horns, within

1500 ft of the railway track;

• Aircraft operational noise as provided by the local airport authority;

and

• The combination of the above noise sources with the existing

noise environment at the site.

1
The guidelines present accepted noise criteria for evaluating the

compatability of the proposed land development considering the noise

exposure of the land. These criteria are used to assess both the outdoor

land use compatibility and the indoor land use compatibility.

The mitigation of noise is also considered in the guidelines. The

following mitigation techniques are included:

0 Highway traffic noise barriers;

0 Building location and orientation relative to the noise sources;

and

0 Building envelope noise isolation including composite constructions

such as windows, walls, and doors.

It is recognized that local authorities may require guidance in the

implementation of noise control measures to achieve noise-compatible land

use. In this context, planning and zoning strategies are discussed, building

noise control codes are reviewed and referenced.

2
1. OVERVIEW OF GUIDELINES

The guidelines are presented in three main sections; Outdoor Noise

Environment, Mitigation Techniques, and Noise Compatible Development.

1.1 CHARACTERIZATION OF THE OUTDOOR NOISE ENVIRONMENT

Sound Levels

A quantitative description of the outdoor noise environment is the first

step in the assessment of noise-compatible land use. These guidelines use the

Day-Night Average Sound Level which is abbreviated DNL and is symbolized mathematically as The DNL is an accepted measure of environmental noise

that allows the noise from different sources to be combined so as to assess

the total environmental noise at a building site (Ref. 1).

The basic component of L^jn is the equivalent sound level denoted by the

symbol Lgq. The equivalent sound level, I^q, is a time average of the

A-weightea acoustic energy generated by a noise source (Ref. 2). The term

"A-welghted" denotes a standardized frequency weighting applied to the noise

(Ref. 3). The magnitude of the equivalent sound level is measured in A-weighted

decibels denoted by dBA.* The A-weighting frequency characteristic approximates the frequency sensitivity of the human ear so that the Lgq value characterizes the environmental noise in a manner similar to that or human response

to noise.

The value of L^j^ at a site is determined by the noise exposure of the site

during a "daytime" period from 7 a.m. to 10 p.m. and the noise exposure of the

site during a "nighttime" period from 10 p.m. to 7 a.m. The noise levels at

night, however, are considered to be 10 dB greater in magnitude than noise levels

of similar magnitude occurlng during the daytime period. This +10 dB nighttime

weighting is intended to account for the increased sensitivity of people to

noise that occurs during sleeping hours as a result of the drop in background

noise levels at night.

The selection of the Day-Night Average Sound Level or DNL for use in these

guidelines requires that local information or data to estimate the noise exposure be collected for both the daytime and the nighttime periods. These data

must be averaged for a typical day of the year. The details of specific

Information required, such as traffic flow data, number of trains, etc., are described in Section 2.

Levels of outdoor noise that relate the noise exposure to land use com- patibility have been established (Ref. 1). These levels are based upon several

considerations. However, the primary consideration is that noise disrupts a

All quantities used in these guidelines are A-weighted sound levels.

The notation dBA and dB will be used interchangeably.

3
person's activity and, thereby, produces a generally adverse response, and a person's expected activity may be related to the intended land use. Additional

considerations used to establish noise criteria are the degree to which the

activity may be sensitive to outdoor noise and the feasibility of mitigation

of the noise either outdoors or by the building envelope.

Table 1 has been extracted from Ref. 1 and presents suggested compatibility

guidelines for residential land use. The application of such guidelines to

local conditions is a local policy judgement. However, the purpose of presenting

Table 1 is to illustrate the practical aspects of using these guidelines to assess noise-compatible land use.

First, if the outdoor DNL is less than 55 (Ldn *^55 dB) , residential

land use is considered to be compatible with the outdoor environment without

restriction. If the DNL is greater than 75 dB (Ldn >75 dB) , residential land use

is considered to be totally incompatible with the outdoor noise.* Hence, the

20 dB range between Ldn == 55 and Ldn = 75 is important. It is equally Important

to note that intervals of 5 dB are used to establish restrictions for compatible

land use. The implication of this 5 dB interval is that a ^3 dB change in the

estimated noise environment or noise mitigation alternatives may be significant

to the final assessment of noise-compatible land use.

Notes On Sound Levels

• The equivalent sound level, Lgq , is a time average of the sound energy over

a specific time interval, T. The DNL or Ldn is a time average over a 24-hour

time period with a +10 dB weighting applied to the nighttime sound levels.

Both Leq and Ldn measured in A-weighted decibels denoted as dBA.

• Instrumentation is availalble for the direct measurement of both Lgq and

Ldn nsing standardized methods (Ref. 4).

• A 3 dB change or a 3 dB difference in sound level is generally considered

to be unnoticeable by the average person (Ref. 5); however, a 3 dB difference

is important in using these guidelines, as it represents either a doubling or halving in the amount of acoustic energy.

• A 10 dB change in sound level corresponds to a doubling of the perceived

loudness (Ref. 5).

• People respond differently to sound of the same level. As a result, the

average response of people to noise should be used to evaluate noisecompatible land use.

Section 4.2 includes a discussion of a model building code for noise

control. This model building code sets the upper limit at Ljn dB

for totally incompatible residential land use.

4
Table

1.

SUGGESTED

LAND

USE

COMPATABILITY

GUIDELINES:

RESIDENTIAL

LAND

USE

(Ref.

1,

Table

pp

6-11

and

as

noted)

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Local

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should

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in

this

DNL

range.

When

residential

use

must

be

allowed,

the

building

envelope

Noise

Level

Reduction

must

be

30

dR.
Prediction and Propagation of Noise from the Source

Section 2 of these guidelines presents noise prediction methods for highway traffic and diesel-electric trains. The predictions incorporate details

of the noise source. However, the predictions are limited to the land area within 1500 ft of either side of the highway pavement or railway track centerline .

The prediction methods assume that both the highway and the railway

alignments are straight and continue indefinitely to the left and to the

right from the receiver's location. The methods then predict the source sound

level at a reference location adjacent to the highway or railway alignment.

For highway traffic noise, the reference location is 50 ft from the pavement

edge of the near lane. For railway noise, the reference location is 100 ft

from the centerline of the railway track. The predicion methods do not apply

to receiver locations closer to the source than the reference distance for the source

.

As noise propagates away from the highway or the railway, the sound

level decreases. However, the rate at which the sound level decreases with

distance depends upon both the source and the site characteristics. The

method used to incorporate site characteristics into the propagation model

assumes that the receiver location has an unobstructed view of either the

highway- or the railway.* Figure 1 illustrates typical source-receiver geometry considered by the method.

With the geometry shown in Figure 1 , the propagation model allows the user

to select either a "hard” site or a "soft" site. A "hard" site is an idealization of either gravel or sparse vegetation between the source and the receiver.

A "soft" site is an idealization of a site covered with grass or vegetation

within 1 ft of the ground. The choice of either a hard site or a soft site

determines the sound level decrease from the source reference location to the

receiver. Soft site propagation yields a larger sound level decrease with

distance than the hard site propagation (Refs. 6, 7, and 8). Figure 2 illustrates typical site conditions for selecting either hard site or soft site

characteristics for the noise propagation.

The prediction of the DNL due to aircraft noise is quite complicated

(Ref. 9) as compared to highway and railway noise prediction. Due to this

complexity, these guidelines do not attempt to include an airport/aircraft

noise prediction method. However, these noise level predictions should be

available from the local airport authority as part of their planning process

(Refs. 10 and 11). The guidelines, however, do allow for the incorporation of

aircraft noise into both the site noise exposure estimate and the building

envelope noise isolation estimate.

Simple site topographic features such as a depressed roadway or a berm may be incorporated in the model as described for barriers in the

Section 3.

6
a) Source-receiver geometry for highway traffic noise

Proposed building location

b) Source-receiver geometry for railway noise

Figure 1. Source-Receiver Geometry for the Present Guidelines

7
1

SS)

. CPo , 1^3 i

a) Hard-site conditions

Figure 2. Typical Site Conditions for Highway Traffic Noise Prediction

8
Notes on Prediction and Propagation of Noise

• Source sound levels depend upon the source characteristics. Since the

guidelines use Ldn the measure of environmental noise, the estimation

of the source characteristics for the time period from 10 p.m. to 7 a.m.

is particularly important.

• These guidelines provide methods for predicting highway traffic noise and

diesel-electric railway noise. Aircraft noise prediction must be obtained

from the local airport authority.

• Noise propagation away from the source depends upon both the source

characteristics and the site characteristics. For highway traffic noise

either "hard" site or "soft" site noise propagation may be used. For

railway noise propagation only the "hard" site conditions are considered.

1.2 CHARACTERIZATION OF THE INDOOR NOISE ENVIRONMENT

These guidelines consider only the indoor noise environment resulting from

outdoor noise sources. The indoor noise environment is fixed in terras of a criterion level . The criterion level is based upon both the intended building

use and the occupants daily activities within the building. This approach

recognizes that outdoor noise may interfere with occupants activities, and

that the degree of interference may be associated with both the intended use of

a building and the interior building subdivisions.

People exposed to noise in their homes show a generalized adverse response

which increases with increasing noise exposure level. This generalized adverse

response is complex and involves a combination of factors including speech

interference, sleep interference, and a frustrated desire for quiet and the

ability to use telephone, radio, and T.V. satisfactorily. Among the activities

interf erred with, speech communication is the most often mentioned. A level of

100-percent sentence intelligibility is achieved if the noise level indoors is

at or below 45 dB, dropping rapidly to 90 percent if the noise level increases

to 65 dB. For this reason, a level of 45 dB indoors is considered to be an acceptable level for rooms sensitive to noise.

Since the outdoor noise environment is characterized by the DNL, the indoor

noise criterion levels must also be characterized by the DNL. As used in these

guidelines, the difference between the outdoor DNL value and the indoor DNL

criterion level is the Noise Level Reduction, NLR, that must be provided by the

building envelope. That is, if the outdoor DNL is L^jn = 65 dB and the indoor

criteria level is L^n “ dB, the required noise level reduction for the

building envelope is 20 dB.

The main objective of these guidelines is to provide a method whereby the user may evaluate building construction on a site exposed to possibly several

noise sources to determine the building noise level reduction.

9
Notes On Indoor Noise Characteristics

• For the purpose of these guidelines, only the contribution from outdoor noise

to the indoor noise environment is considered.

• The indoor noise environment is establihsed in terms of a criterion level or

a level expressed as an Indoor DNL.

• The criterion level may be based upon either a noise criterion for noise

sensitive room use within a building or as an average for the entire indoor

space

.

• Using normal construction, it is easy to achieve a building noise level

reduction of 20 dB. Very unconventional building construction must be used

to achieve a 40 dB building noise level reduction.

1.3 ESTIMATION OF FUTURE CONDITIONS

Noise-compatible land uae requires the evaluation of both the existing and

prospective noise environments at the building site. The reason for considering

future conditions is that the noise environment may change, and the effect of

the change must be evaluated. Normally, a 20-year period is used for planning

purposes (Refs. 13 and 14). However, local considerations will establish this

planning period and policy regarding noise compatibility.

For example, a proposed residential development adjacent to an existing

right-of-way for a future major highway must be judged in terms of the expected

future noise environment. Until the highway is opened, the houses may be over- designed for noise. However, the result is avoiding potential future conflicts

between the noise environment and the planned land use.

These guidelines allow the user to evaluate site noise exposure quickly.

As a result, it is easy to estimate the future noise levels. The information

required for this evaluation is the change in the noise source characteristics.

The only difficulty is obtaining future estimates of the traffic flow for a highway or the characteristics of train operations for railway noise. For aircraft noise, the local airport authority must provide the predictions. Ref. 14

provides a more complete discussion of these considerations.

Notes on Future Conditions

• When evaluating the significance of future noise levels, a change in the

noise source characteristics must result in a DNL change of 3 dB to be

significant. As described in Section 2, if all traffic flow parameters such

as speed, percentage mix of heavy trucks, and the fraction of heavy trucks

operating at night remain constant but the total daily traffic count is

allowed to vary, then the total count must double to cause a +3 dB change,

or decrease by half to cause a -3 dB change in the DNL. Hence, an extremely

accurate estimated future traffic count is not too important for evaluating

changes in the traffic noise environment.

10
1 .4 MITIGATION TECHNIQUES

The mitigation of environmental noise is an option for resolving conflicts

between the noise source and the desired land use. Mitigation techniques may

focus upon any one or all of the elements of the engineering discipline of

noise control. These elements are:

1) Source noise control - decrease noise generated by trucks, trains,

aircraft, etc.

2) Path noise control - alter the propagation of noise from the source

to the receiver location.

3) Receiver noise control - alter the immediate environment at the

receiver location.

These guidelines address only mitigation techniques related to path and receiver

noise control. The noise generated by the traffic flow, or the railway operations, is established using current noise emission characteristics of automobiles, trucks, and diesel-electric trains, and does not include provisions

for the alteration of these characteristics. However, the dependence of highway

noise on traffic flow variables such as speed and vehicle mix may be evaluated.

The guidelines allow the user to evaluate the effectiveness of the following

mitigation techniques:

0 Variation of vehicle mix and traffic flow on highways;

0 Decrease in sound level due to distance between the source

and the receiver;

0 Utilization of barriers or berms for highway traffic noise;

o Utilization of buildings and building components for partial mitigation of highway traffic and railway noise for outdoor receiver

locations; and

0 Utilization of the building envelope for mitigation of highway, railway, and aircraft noise for receivers located indoors.

These mitigation techniques may be used individually or in combination either

to avoid or to resolve conflicts between the noise environment and the desired

land use. The decision as to which technique or combination of techniques to use depends upon the specific conditions at the site. One objective is to

achieve the most cost-effective mitigation. These guidelines only address the

degree of mitigation effectiveness. The cost of alternative mitigation techniques

is a local consideration.

11
Table 2 has been prepared to provide the reader with a feeling for the

effectiveness of various mitigation techniques. The effectiveness is estimated

in terms of the change in the outdoor DNL resulting from implementation of each

mitigation technique. For the conditions listed in Table 2, it is evident

that increasing the source-receiver distance by providing a buffer zone between

the highway and receiver is not too effective, unless the highway noise levels

at 50 ft are already low, and the cost of land is not a consideration.

Similarly, changing the average speed of traffic is not as effective as prohibiting heavy trucks from the highway. However, based upon specific site

conditions, it may be reasonable and prudent to use a combination of mitigation

techniques to ensure noise-compatible land use.

It is the objective of these guidelines to provide the user with methods

suitable to evaluate alternative noise mitigation techniques. Details are provided in the following sections.

Finally, for residential land use, two criteria should be simultaneously

satisified to ensure noise compatibility: an outdoor criterion and an indoor

criterion. The outdoor criterion recognizes that noise may intrude upon normal

outdoor activities about a residence. The indoor criterion applies to normal

Indoor activities. Utilization of the building envelope construction to achieve

the indoor criterion will do nothing to mitigate the effects of outdoor noise

on outdoor activities around the residence. Table 3 illustrates the general

nature of the problem of satisfying both an outdoor criterion and an indoor

criterion to ensure noise-compatible land use. It is seen that above an outdoor

DNL of 65 dB, it is difficult or impossible to achieve acceptable outdoor

conditions, and that acoustical design considerations are required for the

building envelope. It should also be emphasized that the term "windows closed"

implies that mechanical ventilation or perhaps air conditioning is required in

addition to the acoustical design consideration.

Notes On Noise Mitigation

• Mitigation of outdoor noise by 5 to 10 dB is easily achieved using site

design techniques. Higher levels of noise mitigation are more difficult to

either implement or achieve,

• For outdoor DNL between L^n ~ 60 dB and Ljn “ 65 dB and residential land use,

both outdoor and indoor noise mitigation is required. Acceptable indoor

conditions are usually achieved with normal construction by keeping windows

closed

.

• For outdoor DNL above Ljn = 65 dB, the outdoor environment becomes unacceptable for residential land use. Acoustical design of the building envelope

is required and windows must be closed and sealed to achieve a compatible

indoor environment.

12
Table 2. Ranges of L^n Decrease for Various Mitigation Techniques as Estimated

Using These Guidelines

! Mitigation

technique

Range of L^n

decrease ,*

dB

Applicable

noise source Qualifications for application

Change vehicle mix 10 to 12 Highways Prohibition of heavy trucks from

highways

.

Lower traffic speed 5 Highways From 55 mph to 30 mph with 10-

percent heavy trucks.

Decrease traffic volume 3 Highways 50 percent decrease in 24-hour

traffic flow.

Increase the source to 20 to 23 Highways At 1500 ft and relative to

receiver distance level at 50 ft.

13 to 16 Railways At 1500 ft and relative to

level at 100 ft.

Locate a barrier or berm Receiver is shielded by the

between source and 5 to 18 Highway barrier and is within 25 ft

receiver of the barrier.

Shielding by buildings 3 to 15 Highway and Building, courtyards, screened

or building components railway yards, and shielded balconies.

Relative to level at building

location

.

Building envelope 15 to 40 Highway

,

Varies from normal construction

noise level reduction railway, with open window to a tightly

and sealed envelope utilizing

aircraft special acoustical design

i features. Relative to level

1

1

1

at the building location.

1

* Decrease relative to level prior to the implementation of the noted mitigation

technique

.

13
Table

3.

Mitigation

Effectiveness

for

Outdoor

and

Indoor

Criteria

for

Residential

Land

Use co

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14
1.5 NOISE COMPATIBLE LAND USE DEVELOPMENT

With a quantitative description of the outdoor and indoor noise environment

and the possibilities of implementation of noise mitigation techniques, the

tools are available to assess both the feasibility and practicality of achieving

noise-compatible land use development. Such considerations are, however,

dependent upon local desires and policies concerning the ranking of environmental

values among the socioeconomic and technical priorities of the community.

Land Use Control Techniques

The techniques available to communities for the implementation of noisecompatible land use are varied. It is difficult to identify any specific

technique or combination of techniques that may be applied to all communities.

Therefore, guidance can only be provided concerning general techniques that

may apply to local conditions.

At the local level of government, land use control is limited by two

factors

:

(1) The enabling legislation of the state whereby the police powers of

the state are delegated to local governments, and

(2) The level of sophistication of the local governments and their planning agencies.

Both regulatory and non-regulatory controls may be utilized to achieve

noise-compatible land use. Regulatory controls may comprise land use zoning,

subdivision regulations, building codes, health codes, and consumer protection

ordinances. Non-regulatory controls may encompass public acquisition of land

by either direct purchase or easement rights, and the application of financial

considerations using taxation or capital investment incentives. These various

techniques are discussed in Section 4.3 of these guidelines.

These guidelines provide methods for the technical evaluation of environmental noise, the mitigation of the effects of noise upon a community, and the

quantitative comparison of noise control alternatives. The application of

these methods to local conditions forms a basis for developing feasible controls

to ensure compatible land use.

15
2. THE OUTDOOR NOISE ENVIRONMENT

This section describes the methods for estimating the outdoor noise

environment at a site. These methods assume that the site is generally flat

and is free of obstructions between the noise source and the location(s) for

estimating the noise exposure. If the site provides natural shielding of the source from the receiver’s location, the noise exposure estimates must be

adjusted as described in the following section on mitigation. Figures 1 and 2 illustrate the source-receiver geometry.

The prediction methods place the receiver at a 5 ft elevation above the

ground. This elevation correponds to the ear height of a standing person or the center of the ground floor of a building envelope. The horizontal distance

between the noise source and the receiver is the primary site variable required

for these calculations. A scale map of the site indicating the locations of

the noise sources and the receivers is helpful. All horizontal distances are measured from the near edge of the highway pavement for traffic noise or the

centerline of the railway track for train noise.

2.1 HIGHWAY TRAFFIC NOISE PREDICTION

Necessary Information

The following is required to estimate the noise generated by highway

traffic:

• Number of lanes of traffic.

• Average cruise speed of traffic in miles per hour, mph.

• Annual average dally traffic, AADT, in vehicles per 24 hours.

• Percentage of AADT of each vehicle type in the traffic stream, including

- percentage of automobiles and light trucks

- percentage of medium trucks

- percentage of heavy trucks.

• Fraction of each vehicle type operating on the highway during the

nighttime period from 10 p.m. to 7 a.m.*

This list should not overwhelm the user. For an existing or a proposed highway,

the first three items are generally available from State Highway Departments.

It may be more difficult, however, to obtain information on the percentage

vehicle mix and the fraction of each vehicle type operating at night.

Representative data are provided in these guidelines for the annual average

If a 1000 heavy trucks operate each 24 hours and 200 of these operate at

night, the fraction of heavy trucks operating from 10 p.m. to 7 a.m. is 0.20.

16
daily traffic, percentage vehicle mix, and the fraction of each vehicle type

operating at night. The user, however, should obtain if at all possible more

representative estimates for the local conditions

As indicated above, the complete traffic flow is assumed to comprise three

vehicle types. These vehicle types are defined as follows:

Type 1. Automobiles and Light Trucks - all vehicles with two axles and

four wheels designed primarily for transportation of nine or fewer

passengers or for the transportation of cargo. Generally, the vehicle

weight is less than 10,000 lb.

Type 2. Medium Trucks - all vehicles having two axles and six wheels

designed for transportation of cargo. Generally, the vehicle weight

is greater than 10,000 lb but less than 26,000 lb.

Type 3. Heavy Trucks - all vehicles having three or more axles and

designed for transportation of cargo. Generally, the vehicle weight

is greater than 26,000 lb.

This vehicle classification and the noise emission characteristics used to

develop the highway traffic noise prediction method for these guidelines are identical to more refined methods (Refs. 6, 7, and 8). For the purpose of

noise prediction, a bus may be considered equivalent to a medium truck.

Noise Prediction Procedure

The highway traffic noise prediction method is performed in two stages.

First, the DNL resulting from the traffic flow is obtained at a reference

distance of 50 ft from the pavement edge of the near lane. This estimate is

based upon traffic information described above and requires an adjustment for

the site characteristics adjacent to the highway. The second stage of the

prediction method is an adjustment for site conditions that affect the rate at

which the traffic noise decreases with distance away from the highway. Either

a soft site or a hard site condition may be selected for these two adjustments.

In order to organize the step-by-step procedure, a worksheet format is

utilized in conjunction with lookup tables. The necessary worksheets and lookup

tables are grouped together in Section 2.6. Example 1 below illustrates the use of worksheet number 1

.

EXAMPLE 1. Predict the DNL at a location 300 ft from a four lane highway with

the following traffic flow information;

• Average cruise speed is 50 mph.

• Annual average dally traffic is 20,000 vehicles/day

.

• The percentage mix of vehicles is: automobiles, 92 percent; medium

trucks, 2 percent; heavy trucks, 6 percent.

17
• The fraction of vehicles operating at night: automobiles and light

trucks. 0.14; medium trucks, 0.10; and heavy trucks, 0.17,

Figure 3 is a completed worksheet for this example using the hard site noise

propagation characteristics. Figure 4 is a completed worksheet using the soft

site noise propagation characteristics. The estimated DNL values are 67 dB for

the hard site and 61 dB for the soft site. Each of the entries in Figures 3

and 4 will now be described.

The necessary information is listed at the top of the worksheet for ease

of reference. The percentage mix of vehicles and the fraction of vehicles of

each type operating at night are obtained from averages of vehicle counts on similar highways located in similar land use areas. The data listed in the

example problem would result from the following vehicle count:

Vehicle Type 24-hr count 10 p.m. to 7 a.m. count

Automobile and light 18,400 2500

trucks

Medium trucks 400 40

Heavy trucks 1,200 205

The first step in the highway noise prediction method is to estimate the traffic

flow reference noise level term. The value is obtained from Table 4 using the

cruise speed and the percentage mix of vehicles in the traffic flow. Table 4

comprises 12 subtables with each subtable corresponding to the percentage of

heavy trucks in the traffic stream. Within each subtable, the value is obtained

using the percentage mix of medium trucks and the average cruise speed of the

traffic. The range of values for percentage mix of vehicles and average cruise

speed in Table 4 includes almost any possible traffic condition.

The 58 dB value entered in Figures 3 and 4 corresponds to the 6-percent

heavy truck and 2,5-percent medium truck volumes and the 50 mph speed condition.

Although the example indicated 2 percent medium trucks, the value for 2.5

percent is used for the example problem.

In using these guidelines, the following rule should be followed when

Interpolating values form the lookup tables: if the difference between two

values in the table is 3 dB or less, use the higher value, and if the difference

is greater than 3 dB, use the average of the two values.

18
WORKSHEET I. HIGHWAY TRAFFIC NOISE PREDICTION

PROJECT: EXAMPLE 1 PREDICTION FOR HARD SITE

Prepared by: F. RUDDER Date; January 1984

Number of

TRAFFIC FLOW INFORMATION

Average cruise Annual average daily traffic

traffic lanes speed AADT

4 50 mph 20,000 Vehicle/Day

Vehicle type Percent of AADT Fraction operating at night

automobiles & light trucks 92 fn 1 ~ 0.14

medium trucks 2 fn9 = 0.10

heavy trucks 6 ~ 0.17

HIGHWAY TRAFFIC NOISE PREDICTION

Step in the prediction method Lookup Value from

Table lookup table

1 . Traffic flow reference noise level 4 58 dB

2. Adjustment for AADT and nighttime traffic 5* 47 dB

3. Adjustment for site conditions (Use - 31dB none -31 dB

for hard site; -34dB for soft site)

4. Day-night noise level at 50 ft (Add values none 74 dB

in Steps 1,2, and 3)

5. Adjustment for receiver at 300 ft 6(hard site) -6.6 dB

7(soft site)

6. Day-night noise level at receiver

(Add values in Steps 4 and 5) none 67. 4 dB

* If heavy trucks are present use the value of f ^3 to enter Table 5.

If heavy trucks are not present use the value of to enter Table 5.

If only automobiles and light trucks are present use the value of f^,]^ to enter Table 5.

Figure 3. Completed worksheet for highway traffic noise prediction:

hard site conditions

19
WORKSHEET I. HIGHWAY TRAFFIC NOISE PREDICTION

PROJECT ; EXAMPLE 1 PREDICTION FOR SOFT SITE

Prepared by; F . RUDDER Date: January 1984

Number of

traffic lanes

4

Vehicle type

TRAFFIC FLOW INFORMATION

Average cruise

speed

50 mph

Percent of AADT

Annual average daily traffic

AADT

20,000 Vehicle/Day

Fraction operating at night

automobiles & light trucks

medium trucks

heavy trucks

92

2

6

fnl - 0

»

fn2 = 0.10

fn3 = 0»17

HIGHWAY TRAFFIC NOISE PREDICTION

Step in the prediction method Lookup Value from

Table lookup table

1. Traffic flow reference noise level 4 58 dB

2. Adjustment for AADT and nighttime traffic 5* 47 dB

3. Adjustment for site conditions (Use - 31dB none -34 dB

for hard site; -34dB for soft site)

4. Day-Night Noise Level at 50 ft (Add values none 71 dB

in Steps 1,2, and 3)

5. Adjustment for receiver at 300 ft 6(hard site) dB

7 ( soft site) -9.6

6. Day-Night Noise Level at Receiver

(Add values in Steps 4 and 5) none 61.4 dB

* If heavy trucks are present use the value of fn3 to enter in Table 5.

If heavy trucks are not present use the value of f„2 to enter Table 5

.

If only automobiles and light trucks are present use the value of f^jj

to enter in Table 5.

Figure 4. Completed worksheet for highway traffic noise prediction:

soft site conditions

20
Table 4. Traffic Flow Reference Noise Levels in dB

a) 0 Percent Heavy Trucks b) 2 Percent Heavy Trucks

s

mph

Percentage med. trucks S

mph

Percentage med. trucks

0 2.5 5.0 0 2.5 5.0

30 47 48 49 30 51 51 52

35 49 50 51 35 52 53 53

40 51 52 53 40 53 54 54

45 52 53 54 45 54 55 56

50 53 54 55 50 55 56 57

55 54 55 56 55 56 57 58

60 55 56 57 60 57 58 59

c) 4 Percent Heavy Trucks d) 6 Percent Heavy Trucks

S

mph

Percentage med. trucks S

mph

Percentage med. trucks

0 2.5 5.0 0 2.5 5.0

30 53 53 53 30 54 54 55

35 54 54 55 35 55 55 56

40 55 55 56 40 56 56 57

45 56 56 57 45 57 57 58

50 57 57 58 50 58 58 59

55 58 58 59 55 59 59 60

60 58 59 59 60 59 60 60

21
Table 4. Traffic Flow Reference Noise Level in dB (continued)

e) 8 Percent Heavy Trucks f) 10 Percent Heavy Trucks

s

mph

Percentage med. trucks S

mph

Percentage med. trucks

0 2.5 5.0 0 2.5 5.0

30 55 55 55 30 56 56 56

35 56 56 57 35 57 57 57

40 57 57 58 40 58 58 58

45 58 58 59 45 59 59 59

50 59 59 59 50 60 60 60

55 60 60 60 55 60 61 61

60 60 61 61 60 61 61 62

g) 12 Percent Heavy Trucks h) 14 Percent Heavy Trucks

S

mph

Percentage med. trucks S

mph

Percentage med. trucks

0 2.5 5.0 0 2.5 5.0

30 56 57 57 30 57 57 57

35 58 58 58 35 58 58 58

40 58 59 59 40 59 59 59

45 59 60 60 45 60 60 60

50 60 60 61 50 61 61 61

55 61 61 61 55 61 62 62

60 61 62 62 60 62 62 62

ll
Table 4. Traffic Flow Reference Noise Levels in dB (continued)

i) 16 Percent Heavy Trucks j) 18 Percent Heavy Trucks

s

mph

Percentage med, trucks S

mph

Percentage med. trucks

0 2.5 5.0 0 2.5 5.0

30 58 58 58 30 58 58 58

35 59 59 59 35 59 59 59

40 60 60 60 40 60 60 60

45 60 61 61 45 61 61 61

50 61 61 62 50 62 62 63

55 62 62 62 55 62 62 63

60 62 62 63 60 63 63 63

k) 20 Percent Heavy Trucks 1) 22 Percent Heavy Trucks

S

mph

Percentage med. trucks S

mph

Percentage med. trucks

0 2.5 5.0 0 2.5 5.0

30 58 59 59 30 59 59 59

35 60 60 60 35 60 60 60

40 60 61 61 40 61 61 61

45 61 61 62 45 62 62 62

50 62 62 62 50 62 62 63

55 63 63 63 55 63 63 63

60 63 63 64 60 64 64 64

23
The second step in the worksheet is an adjustment that accounts for the

total traffic volume and the fraction of vehicles of a given type operating

during the nighttime period from 10 p.m. to 7 a.ra. The value of this adjustment

is obtained from Table 5 using the AADT and the fraction of the loudest vehicle

type operating at night (see the note at the bottom of the worksheet). For

this example, heavy trucks are present in the traffic flow; so, the value

of f^3 = 0.17 is used with the AADT = 20,000 to obtain the 47 dB adjustment.

The third step in the worksheet is an adjustment for site conditions as indicated in the worksheet. The value of the adjustment is -31 dB for a hard

site and -34 for a soft site.

The fourth step in the worksheet is the simple addition of the first three

numbers, remembering that the site adjustment is a negative number. For the

hard site example in Figure 3 the addition is: 58 + 47 + (-31) = 105 - 31 = 74.

As indicated in the worksheet, this result is the DNL at a location 50 ft from

the near edge of the pavement

.

The DNL at the receiver location is obtained by adding the distance

adjustment obtained from Table 6 for the hard site condition and Table 7 for the soft site condition in step 5 to the DNL value in step 4. This DNL

value represents the noise exposure at the receiver for unobstructed source- receiver site conditions.

Comments on the Lookup Tables

The value listed in the lookup tables are presented as integer values in

dB units. These values are the result of more involved calculations and have

been rounded to the nearest integer value. The distance attenuation presented

in Table 6 and 7 are similarly rounded to the nearest tenth of a dB. This is

done to emphasize that the distance attenuation is a smooth function of distance

and should not imply accuracy of the prediction.

For convenient reference, blank copies of the worksheets I, II and III are grouped together in Section 2.6.

Representative Traffic Flow Data

For reference, representative traffic flow data have been compiled or estimated to assist the user. These data are presented for AADT values,

percentage vehicle mix, and fraction of each vehicle type operating during the

nighttime period from 10 p.m. to 7 a.m.

For the annual average daily traffic, the value of the AADT was estimated

in Ref. 16 in relation to a population place size and the functional roadway

classification system used by FHWA (Ref. 17). The population place size is

defined by census data and corresponds to the population living in a contiguous

geographic area (Ref. 18). The representative values for AADT are presented

in Table 8 .

24
Table 5. Traffic Noise Adjustment for AADT and Nighttime Conditions in dB

AADT,

f , n fraction of vehicles travelling from 10 p.m. to 7 a.m. veh/24 hr

0 0.03 0.06 0.11 0.17 0.24 0.33 0.375*

1 ,600 32 33 34 35 36 37 38 38.4

2,000 33 34 35 36 37 38 39 39.4

2,500 34 35 36 37 38 39 40 40.4

3,200 35 36 37 38 39 40 41 41.4

4,000 36 37 38 39 40 41 42 42.4

5,000 37 38 39 40 41 42 43 43.4

6,300 38 39 40 41 42 43 44 44.4

8,000 39 40 41 42 43 44 45 45.4

10,000 40 41 42 43 44 45 46 46.4

12,500 41 42 43 44 45 46 47 47.4

16,000 42 43 44 45 46 47 48 48.4

20,000 43 44 45 46 47 48 49 49.4

25,000 44 45 46 47 48 49 50 50.4

32,000 45 46 47 48 49 50 51 51.4

40,000 46 47 48 49 50 51 52 52.4

50,000 47 48 49 50 51 52 53 53.4

63,000 48 49 50 51 52 53 54 54.4

80,000 49 50 51 52 53 54 55 55.4

* Uniform 24 hour traffic flow.

25
Table 6. Traffic Noise Adjustment for Distance; Hard Sites in dB

D, NUMBER OF TRAFFIC LANES

ft 1 2 3 4 6 8

50 0 0 0 0 0 0

75 - 1.6 - 1.5 - 1.4 - 1.3 - 1.2 - 1.1

100 - 2.8 - 2.6 - 2.5 - 2.3 - 2.2 - 2.0

150 - 4.5 - 4.2 - 4.0 - 3.8 - 3.6 - 3.4

200 - 5.7 - 5.4 - 5.1 - 4.9 - 4.6 - 4.4

250 - 6.6 - 6.3 - 6.0 - 5.8 - 5.5 - 5.2

300 - 7.4 - 7.0 - 6.8 - 6.6 - 6.2 - 5.9

350 - 8.0 - 7.7 - 7.4 - 7.2 - 6.8 - 6.5

400 - 8.6 - 8.3 - 8.0 - 7.7 - 7.3 - 7.0

450 - 9.1 - 8.8 - 8.5 - 8.2 - 7.8 - 7.4

500 - 9.6 - 9.2 - 8.9 - 8.7 - 8.2 - 7.9

750 - 11.3 - 10.9 - 10.6 - 10.3 - 9.9 - 9.5

1000 - 12.5 - 12.2 - 11.8 - 11.6 - 11.1 - 10.7

1500 - 14.3 - 13.9 - 13.6 - 13.3 - 12.8 - 12.4

26
Table 7. Traffic Noise Adjustment for Distance: Hard Sites in dB

D, NUMBER OF TRAFFIC LANES

ft. 1 2 3 4 6 8

50 0 0 0 0 0 0

75 - 2.4 - 2.2 - 2.0 - 1.9 - 1.7 - 1.6

100 - 4.2 - 3.8 - 3.6 - 3.4 - 3.0 - 2.8

150 - 6.7 - 6.2 - 5.9 - 5.6 - 5.1 - 4.7

200 - -8.5 - 8.0 - 7.5 - 7.2 - 6.6 - 6.2

250 - 9.9 - 9.3 - 8.9 - 8.5 - 7.9 - 7.4

300 -11.1 -10.5 -10.0 - 9.6 - 8.9 - 8.4

350 -12.1 -11.4 -10.9 -10.5 - 9.8 - 9.2

400 -12.9 -12.3 -11.7 -11.3 -10.6 -10.0

450 -13.7 -13.0 -12.5 -12.0 -11.3 -10.7

500 -14.3 -13.7 -13.1 -12.7 -11.9 -11.3

750 -17.0 -16.3 -15.7 -15.2 -14.4 -13.7

1000 -18.2 -18.1 -17.5 -17.0 -16.2 -15.5

1500 -23.3 -22.6 -22.0 -21.4 -20.5 -19.8

27
Similarly, representative values of both the percentage vehicle mix and

the fraction of vehicles operating during the nighttime were developed based

upon available information (Ref. 19). These data are presented in Table 9 for

urban and rural areas and the FHWA functional roadway classification.

2 .2 RAILWAY NOISE PREDICTION

These guidelines allow the user to predict the railway noise exposure for

trains powered by diesel-electric locomotives. The noise generated by electric

powered trains or rapid-rail system operations are not included.

Necessary Information

The following information is required to estimate the noise generated by

trains powered by diesel-electric locomotives and, as required, by the train

warning horns at grade ’ crossings

;

0 Average speed of the train in miles per hour.

o The average number of trains passing the site each 24 hours.

0 The average number of trains passing the site for the nighttime

period from 10 p.m. to 7 a.ra.

0 The characteristics of the "average train" as determined by the

number of diesel-electric locomotives and the number of cars in

the train. (Discussed below.)

0 The distance(s), D, measured away from the track centerline and L,

measured along the track from the site to each grade crossing requiring

an approach warning by the train. (See Figure 5.)

Characteristics of The Average Train

To estimate the DNL for railway operations it is necessary to determine

the noise exposure resulting from each passage of a train. Three considerations

make this prediction more complicated than the prediction of the noise generated

by highway traffic. First, the duration of the train noise must be considered.

The duration depends upon the train length and the speed. Next, the noise from

the locomotive must be considered in conjuction with the noise generated by the cars. (This is similar to the mix of heavy trucks and automobiles for highway

traffic noise) . Lastly, the distance attenuation of railway noise for a timeaveraged sound level such as Lgq (the basis for the DNL value) depends on the

length of the train, and to a lesser degree, upon the train speed. All of

these details, if included directly in these guidelines, would result in a cumbersome methodology unsuited for the purpose of these guidelines.

28
(U>

(U kJ

•rac3O

CO

4Jo

•H•30)

CUOu

•O

(U •H3

cr0) 0£

OJ

(Uuc

<0 4J

CO

00c

t-l CJCO

(V o

(U 4J H

CO

0)

1^3

00

29

Resulting

From

Railway

Trains
Table 8. Representative Values of Annual Average Daily Traffic, AADT,

Vehicles Per 24 Hours (1976)

Population

Place Size*

Interstate Other FWY

and Expwy

Major

Arterials

Minor

Arterials

Collectors Local

Streets

>2M 75,000 66,000 19,000 9,500 4,000 1,100

IM to 2M 60,000 32,000 17,000 7,000 3,500 700

500k to IM 47,000 34,000 16,000 8,000 3,800 700

200k to 500k 40,000 29,000 16,000 8,500 3,800 800

100k to 200k 32,000 23,000 15,000 7,300 3,300 650

50k to 100k 22,000 20,000 12,000 6,000 3,000 650

25k to 50k 23,000 17,000 11,000 5,500 2,500 600

5k to 25k 18,000 13,000 8,900 4,300 2,000 500

RURAL 14,000 4,600 2,500 900 400 100

* Place size is defined as in Ref. 18

M denotes population in millions

k denotes population in thousands

30
Table 9. Representative Values of and Fi as Estimated from Ref, 19 Data

URBAN AREAS

Highway

classification

Automobiles and

light trucks (i=l)

Medium

(i=

trucks

=2)

Heavy

(i=

trucks

=3)

Motorcyles and

buses (i=4)

f F f F f F f F

nl 1 n2 2 n3 3 n4 4

Interstate, FWY

and expwy 0.15 0.88 0.11 0.02 0.26 0.09 0.16 0.01

Other Principal

arterials 0.14 0.93 0.10 0.02 0.20 0.04 0.14 0.01

Minor arterials 0.13 0.95 0.07 0.02 0.13 0.02 0.14 0.01

Collectors 0.13 0.94 0.06 0.02 0.12 0.02 0.11 0.01

RURAL AREAS

Highway

classification

Automobiles and

light trucks (i=l)

Medium

(i=

trucks

=2)

Heavy

(i=

trucks

=3)

Motorcyles and

buses (i=4)

f F f F f F f F nl 1 n2 2 n3 3 n4 4

Interstate 0.13 0.78 0.13 0.03 0.28 0.18 0.16 0.01

Other Principal 1 arterials 0.12 0.86 0.10 0.03 0.22 0.10 0.11 0.01 '

1 Minor arterials 0.12 0.90 0.08 0.03 0.14 0.06 0.09

1 0.01 !

1 Collectors 0.14 0.87 0.10 0.04 0.14 0.08 0.11 0.01 !

1

31
To simplify the guidelines without compromising the noise exposure

estimate, an average train is defined in terms of all of the trains expected

to pass the site. To this effect, it is assumed that both the daily total

number and number of nighttime train pass-by events are equal for the "average

trains" and the actual trains.

This approach is taken since individual trains along a given track may vary in

the number of locomotives and the number of cars, and one really desires an average

.

The average train is defined in terms of the average number of dieselelectric locomotives per train and the average number of cars per locomotive.

EXAMPLE 2. For the data listed below, determine the characteristics of the

average train to use in these guidelines

.

Estimate of Actual Operations

Train Number of Number of Scheduled

number locomotives railway cars passage time Direction

1 2 60 2:00 a.m. Eastbound

2 2 45 6:00 a.m. Eastbound

3 3 80 9:30 a.m. Eastbound

4 4 120 5:00 p.m. Westbound

5 3 100 11:00 p.m. Westbound

Total 14 405

The total number of trains is five with three trains passing during the

nighttime. The number of locomotives in the average train is 14/5 or 3 locomotives per train and 405/14 or 29 railway cars per locomotive. Hence, the

average train comprises three diesel-electric locomotives and 87 railway cars.

Noise Prediction Procedure

A worksheet format is utilized to perform the railway noise prediction. A

two-part sheet is used to list the necessary information required for the

prediction. The first part is used to document the characteristics of the

average train. The second part is used to document the site location relative

to grade crossings requiring the trains to use warning horns.

Similarily, a two-part noise prediction worksheet is used: the first part

to predict the pass-by noise and the second part to predict the noise exposure

for warning horns. The noise exposures resulting from the train for pass-bys

32
and from the warning horns are then combined to determine the total site railway

noise exposure.

For convenient reference, blank copies of the data sheet and the noise

prediction worksheets are presented in Section 2.6.

EXAMPLE 3. Using the train operational data given in EXAMPLE 2, determine the

site noise exposure if the pass-by speed is 40 mph and the site is located

400 ft from the railway track centerline, and 600 ft from a grade crossing

requiring a warning horn.

A completed data sheet for this example problem is presented in Figure 6

.

Note that the fractional values for both the average number of locomotives per

train and the average number of railway cars per locomotive are rounded to the

nearest interger.

A completed worksheet for predicting the pass-by noise resulting from

the average daily railway operation is presented in Figure 7. The first step

in the prediction is to determine the reference noise level for one train

pass-by. This value is obtained from Table 10 using the average number of

locomotives per train, the average number of railway cars per locomotive, and

the train speed. Table 10 comprises four subtables each corresponding to

a different average number of locomotives per train. For example problem 3,

Table 10c is used since there are three locomotives per train.

The second step in the prediction is an adjustment for the total number of

trains per 24 hours. This adjustment is obtained from Table 11. For example

problem number 3 since there are five trains per day the value is -6.8 dB.

The third step in the prediction is another adjustment which accounts for

nighttime train pass-by events. This adjustment is obtained from Table 12

using the fraction of trains that pass the site between 10 p.m. and 7 a.m. For

this example, the fraction is 3/5 = 0.60, and the value of the adjustment is

8 dB.

Step 4 is the simple addition of the values of the reference noise level

and the two adjustments to this reference level. For the example problem, the

arithmetic is: 68 + (-6.8) + 8 = 69 .2 dB. This value is the DNL at a location

100 ft along side the railway track centerline for the five average train operations .

For locations beyond 100 ft from the track centerline, the DNL value

estimated in Step 4 must be adjusted to account for distance attenuation.

Only hard site conditions are included in these guidelines for estimating the

railway noise distance attenuation. For the example, the distance adjustment is obtained from Table 13 using the distance D = 400 ft (see Figure 5)

and the average number of railway cars per locomotive, 29. The value of the

distance adjustment for the example is -6.7 dB. This value is entered in

step 5 of Part I of the worksheet.

33
WOilKSHEET II. DIESEL-ELECTRIC RAILWAY NOISE PREDICTION DATA

Project: EXAMPLE PROBLEM 2

Prepared by: F. RUDDER Date January 1984

PART I DATA DESCRIBING THE AVERAGE TRAIN *

a) Train speed, mph: S = 40

b) Total number of trains per day: N'j = ^

c) Total number of trains operating at night: N^ = 3

d) Total number of locomotives per day: Nl = 14

e) Total number of railway cars per day: N^ = 405

(1) Calculate the average number of locomotives per train:

N = Nl/Nt = 14/15 ->• 3

(2) Calculate the average number of railway cars per locomotive:

n = Nc/Nl = 405/14 ->• 29

(3) Calculate the fraction of railway operations occurring during

the nighttime (10 p.m, to 7 a.m.)

fn = Nn/NT = 3/5 = 0.6

PART II DATA DESCRIBING THE SITE LOCATION (see Figure 5)

a) Distance from track to the site, ft: D = 400

b) If there is a warning point within 1/2 mi of

the site, determine the distance along the track

from the warning point, ft: L = 600

* The mathematical notation for the data follows the notation used in

Appendix A which describes the railway noise prediction model.

Figure 6. Completed Data Sheet for Railway Noise Prediction: Example 2
WORKSHEET III. DIESEL-ELECTRIC RAILWAY NOISE PREDICTION:

PASS-BY NOISE EXPOSURE

PART I DIESEL-ELECTRIC PASS-BY OPERATIONS

(1) From Table 10 and the data for the average train of Worksheet II

(N = 3 ; n = 29 ; and S = 40 mph)

Reference sound level for one pass-by = 68 dBA

(2) From Table 11 the sound level adjustment for

N*!- = 5 trains per day = -6.8 dB

(3) From Table 12 the sound level adjustment for

fn = 0.6 fraction of nighttime operations = +8.0 dB

(4) Adding (1), (2), and (3) above, the day-night

sound level for railway pass-by noise at a location Dq = 100 ft away from the track = 69 .2 dB

(5) From Table 13 the sound level adjustment for

the distance D = 400 ft from the track centerline = -6 .7 dB

(6) Adding (4) and (5) above, the day-night

sound level for railway pass-by noise at

a location D = 400 ft from the track

centerline = 62.5 dB

IF THERE ARE NO WARNING POINTS WITHIN 1/2 MILE OF THE

SITE, THE ABOVE RESULT, (6), IS THE DAY-NIGHT SOUND LEVEL

AT THE SITE RESULTING FROM PASS-BY NOISE OF DIESEL-ELECTRIC

TRAINS

.

IF WARNING HORN NOISE OCCURS, PROCEED TO PARTS II AND III

OF THIS WORKSHEET

Figure 7. Completed Worksheet for Railway Pass-by Noise Prediction:

Example 3

.

35
Table 10. Reference Sound Level for Railway Pass-By Operations in dB

a) One Diesel-electric Locomotive Per Train

Average

number of

railcars per

locomotive

Train Speed,

mph

20 30 40 50 60

fewer than 10 63 62 61 61 61

10 to 19 . 63 63 62 62 63

20 to 29 64 63 63 63 64

30 to 39 64 64 64 64 65

40 to 49 64 64 65 65 66

50 to 59 65 65 65 66 66

b) Two Diesel-Electric Locomotives per Train

Average

number of

railcars per

locomotive

Train Speed,

mph

20 30 40 50 60

fewer than 10 66 65 64 64 64

10 to 19 66 66 65 65 66

20 to 29 67 66 66 66 67

30 to 39 67 67 67 67 68

40 to 49 67 67 68 68 69

50 to 59 68 68 68 69 69

36
Table 10. Reference Sound Level for Railway Pass-By Operations in dB (concluded)

c) Three Diesel-electric Locomotive Per Train

Average

number of

railcars per

locomotive

Train Speed,

mph

20 30 40 50 60

fewer than 10 68 66 66 66 66

10 to 19 68 67 67 67 67

20 to 29 67 68 68 68 68

30 to 39 69 68 68 69 69

40 to 49 69 69 70 70 70

50 to 59 70 69 70 71 71

d) Four Diesel-Electric Locomotives Per Train

Average

number of

railcars per

locomotive

Train Speed,

mph

20 30 40 50 60

fewer than 10 69 68 67 67 67

10 to 19 69 69 68 68 69

20 to 29 70 69 69 69 70

30 to 39 70 70 70 70 71

40 to 49 70 70 71 71 72

50 to 59 71 71 71 72 72

37
Table 11. Sound Level Adjustment for Railway Pass-By Operations

Total Number of Trains Per Day

Number of

trains

per 24 hours

Adjustment

,

dB

1 -13.8

2 -10.8

3 - 9.0

4 - 7.8

5 - 6.8

6 - 6.0

00 - 5

9-11 - 4

12 - 3

13-17 - 2

18-21 - 1

Number of

trains

per 24 hours

Adjustment

,

dB

22-27 0

28-33 + 1

34-42 +2

43-53 +3

54-66 +4

67-84 +5

84-110 +6

111-132 +7

133-172 +8

173-210 +9

211-265 + 10

38
Table 12. Sound Level Adjustment for Railway Noise:

Fraction of Total Events During the Night

Fraction

of trains

operating

at night

Adjustment

dB

0 to 0.02 0

0.03 to 0.05 1

0.06 to 0.09 2

0.10 to 0.13 3

0.14 to 0.20 4

0.21 to 0.28 5

0.29 to 0.38 6

0.39 to 0.52 7

0.53 to 0.68 8

0.69 to 0.88 9

0.89 to 1.00 10

39
Table 13. Sound Level Adjustment for Railway Pass-By Noise;

Distance Away from the Track Centerline

Distance

away from

track,

ft

Average number of railway cars per locomotive

Fewer than

10 10 to 19 20 to 29 30 to 39 40 to 49 50 to 59

100 0.0 0.0 0.0 0.0 0.0 0.0

200 - 3.2 - 3.2 - 3.2 - 3.1 - 3.1 - 3.1

300 - 5.3 - 5.2 - 5.2 - 5.1 - 5.1 - 5.1

400 - 7.0 - 6.8 - 6.7 - 6.6 - 6.5 - 6.4

500 - 8.4 - 8.1 - 7.9 - 7.7 - 7.6 - 7.5

600 - 9.5 - 9.1 - 8.9 - 8.7 - 8.6 - 8.5

700 -10.6 -10.1 - 9.8 - 9.5 - 9.4 - 9.2

800 -11.5 -10.9 -10.6 -10.3 -10.1 - 9.9

900 -12.3 -11.6 -11.3 -10.9 -10.7 -10.5

1000 -13.0 -12.3 -11.9 -11.5 -11.3 -11.1

1100 -13.7 -12.9 -12.5 -12.0 -11.8 -11.6

1200 -14.3 -13.5 -13.0 -12.5 -12.2 -12.0

1300 -14.9 -14.0 -13.5 -12.8 -12.7 -12.4

1400 -15.5 -14.5 -13.9 -13.0 -13.1 -12.8

1500 -16.0 15.0 -14.4 -13.8 -13.5 -13.2

40
The sixth and final step in the pass-by noise perdiction is the addition

of the distance adjustment of step 5 to the DNL value obtained in Step 4. The

arithmetic for the example is 69.2 + (-6.7) = 69.2 - 6.7 = 62.5 or 63 dB.

This is the DNL at the receiver location for the pass-by noise exposure.

Since problem example 3 includes warning horn noise exposure, we must proceed to Part II of Worksheet III. Figure 8 is the completed worksheet for

warning horn noise prediction of the example problem. The prediction method

requires the user to obtain a reference level and to adjust this reference

level to obtain the DNL.

The first step in predicting warning horn noise exposure is to obtain the

reference level the receiver location . This reference level assumes that

trains approach the warning point from either direction, and that the warning is

initiated 1/4 mi along the track before the leading locomotive crosses the

warning point. The reference level for warning horn noise is obtained from

Table 14 using the receiver location as indicated in Figure 5. For the

example problem with the receiver 400 ft away from the track centerline and 600

ft along the track away from the warning point, the reference level is 48 dB.

The second step is to adjust the reference level for the total number of

events and for duration of each event. This adjustment is obtained from Table

15 and, for the example problem, is +8 dB.

The third step is to adjust the reference level for the fraction of

nighttime occurences of warning horn noise. This adjustment is obtained from

Table 12 and is +8 dB.

Step 4 is the simple addition of the reference level in step 1 and the

adjustments in steps 2 and 3. For the example problem the arithmetic is;

48 + 8 + 8 = 64 dB. This is the DNL at the receiver location for warning horn

noise.

One final calculation is required to complete the example. We have

estimated the train pass-by DNL to be 63 dB and the train warning-horn DNL to

be 64 dB. At this site, however, the pass-by and warning horn noise occur

simultaneously for each train moving along the track. We must now determine

the combination of these simultaneous noise events. (The answer is NOT

63 + 64 = 127 dB!)

Part III of the railway noise prediction indicates the method for

combining two simultaneous noises to obtain the total noise at a location.

The data for the example problem are entered as indicated in Figure 8.

The answer is obtained using Table 16 and, for the example problem, is 67 dB.

This is the total DNL at the receiver due to railway noise at the site.

Combining Sound Levels

The last example illustrated the method for combining two simultaneous

sound levels to determine the total sound level. The combination of these two

41
WORKSHEET III. DIESEL-ELECTRIC RAILWAY NOISE PREDICTION;

PASS-BY NOISE EXPOSURE

PART II WARNING HORN NOISE PREDICTION

(1) From Table 14 or Figure 5 a the location

L = 600 ft along the track from the

warning point and D = 400 ft from the

track,

Reference should level for one warning

(2) From Table 15 the sound level adjustment

for N'T = _5 trains per day passing the

site at S = ^ mph is

(3) From Table 12 the sound level adjustment

for fn = 0 .6 fraction of nighttime

operations is

(4) Adding (1), (2), and (3) above, the daynight sound level for railway warning

horn noise at the location L = 600 ft

and D = 400 ft is

= 48 dBA

= + 8 dBA

= + 8 dBA

= 64 dBA

PART III COMBINED PASS-BY AND WARNING HORN NOISE PREDICTION

The pass-by sound level and the warning sound level must be combined

to obtain the total noise prediction at the location,

(1) From Part I; step (6) the Pass-By Day-Night Sound Level is = 63 dB

(2) From Part II; step (4) the Warning Horn Day-Night Sound

Level is = 64 dB

(3) Using (1) and (2) above, the sound level difference is:

higher level - lower level = 64 - 63 = 1

(4) Using the sound level difference from step (3) and from

Table 16, the combined Day-Night Sound Level is;

higher level + adjustment = 64 + 2.5 = 66,5 = 67 dB

THE RESULT (4) ABOVE IS THE COMBINED DAY-NIGHT SOUND

LEVEL AT THE SITE FOR RAILWAY NOISE

Figure 8. Completed Worksheet for Railway Warning Horn Noise Prediction

and Combined Railway Noise Prediction; Example 3

42
Table 14. Reference Sound Level: Railway Warning Horns is dB

(See Figure 5)

Distance

away from

L, Distance along track mesured from the warning point, ft

track,

ft 0 to 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600

100 55 55 55 55 54 50 45 43 41 40 38 37

200 52 52 52 51 50 48 45 42 41 40 38 37

300 50 50 49 49 48 46 44 42 41 39 38 37

400 48 48 48 47 47 45 43 42 40 39 38 37

500 47 47 47 46 45 44 43 41 40 39 38 37

600 46 46 46 45 44 43 42 41 40 39 38 37

700 45 45 45 44 44 43 42 41 40 39 38 37

800 44 44 44 43 43 42 41 40 39 38 37 37

900 44 43 43 43 42 41 41 40 39 38 37 37

1000 43 43 42 42 41 41 40 39 39 38 37 36

1100 42 42 42 41 41 40 40 39 38 38 37 36

1200 42 41 41 41 40 40 39 39 38 37 37 36

1300 41 41 41 40 40 39 39 38 38 37 36 36

1400 41 40 40 40 39 39 38 38 37 37 36 36

1500 40 40 40 39 39 39 38 38 37 37 36 36

43
Table 15. Sound Level Adjustment for Railway Warning Horns in dB

Total Number of Trains and Train Speed

number

of trains/

24-hr

Train speed

mph

20 30 40 50 60

1 4 2 1 0 -1

2 7 5 4 3 2

3 9 7 6 5 4

4 10 8 7 6 5

5 11 9 8 7 6

6 12 10 9 8 7

7-8 13 11 10 9 8

9-10 14 12 11 10 9

11-13 15 13 12 11 10

14-17 16 14 13 12 11

18-22 17 15 14 13 12

23-28 18 16 15 14 13

29-35 19 17 16 15 14

36-45 20 18 17 16 15

46-56 21 19 18 17 16

57-71 22 20 19 18 17

72-90 23 21 20 19 18

91-110 24 22 21 20 19

111-142 25 23 22 21 20

143-180 26 24 23 22 21

130-225 27 25 24 23 22

A4
Table 16. Table for Combining Sound Levels

Example

:

Combined Level = Higher Sound Level + Adjustment

Sound Level Difference = Higher Sound Level

- Lower Sound Level

Sound level

difference, Adjustment,

dB dB

0 3.0

1 2.5

2 2.1

3 1.8

4 1.5

5 1.2

6 1.0

7 0.8

8 0.6

9 0.5

10 0.4

>10 0.0

Determine the combined sound level for three sound levels of 65, 60,

and 58 dB.

65 - 60 = 5: Combined level = 65 + 1.2 = 66.2 dB

66.2 - 58 = 8.2: combined level = 66.2 + 0.6 = 66.8 dB

Combined sound level is 66.8 or 67 dB.

45
sound levels is not the simple addition of the two sound levels as indicated

by both the example and the values listed in Table 16. Indeed, the values in

Table 16 indicate that the combined level of two sounds of equal level is a level that is 3 dB greater than the two equal levels. That is, the combination

of two simultaneous sounds each at a level of 50 dB is 53 dB, or the combination

of two levels, one of 60 dB and one of 50 dB is 60 dB (see Table 16).

Now, we return to our example problem of the train pass-by noise and the

warning horn noise. The pass-by DNL was estimated to be 63 dB, and the warning

horn noise was estimated to be 64 dB resulting in a total level of 67 dB.

Nothing was said about noise from the roadway at the grade crossing. Suppose

that the noise from the roadway at the grade crossing was estimated to be

Ldn ” 55 dB at the receiver. Then, the combination of the three sound levels

is calculated according to the rules Indicated in Table 16. Since the difference

67-55 = 12 dB, and is greater than 10, the adjustment for traffic noise is 0

dB. Thus, the combination yields 67 + 0 = 67 dB.

Since the present guidelines require the user to perform calculations, it

is worthwhile explaining the physics that determine when the user should add

two numbers using ordinary arithmetic and when the two numbers should be combined

using Table 16. The key to this is the understanding of the combination of

acoustic energy at a single location. When the receiver is exposed to two or more simultaneous noise sources, he receives a total amount of acoustic energy.

This total or combined energy may be expressed as a level in dB units, just as the energy from each noise source may be expressed as a level in dB units.

The acoustic energies from each source add together (in the sense of

2+2=4) and the combination are then expressed as a level in dB units. As

a result, the adjustments given in Table 16 indicate that combining the energy

from two identical noise sources doubles the total energy and increases the

level by 3 dB. Similarly, if the energy output from a noise source was decreased

by half, the level would decrease by 3 dB relative to the original level.

EXAMPLE 4. Consider a receiver exposed to noise generated by highway traffic

at a site with a single building. The guidelines assume that the highway

extends indefinitely in both directions from the building location. It is

desired to estimate the total acoustic energy received at each exterior wall of

the building. The geometry is as indicated in Figure 9a.

First, consider the wall facing the highway. The total acoustic energy

received at this wall is the total predicted by the guidelines, since a person

standing along this wall and facing the highway can see the entire highway.

Next, consider a person standing at either end of the building and facing

the highway. At either location, the receiver can see only half of the highway.

Hence, one could expect that these locations receive only half of the total

energy or half of the energy received at the wall facing the highway.

Finally, for a person standing along the side of the building facing away

from the highway, the building totally obstructs the person’s view of the

highway, and no acoustic energy is received.

46
I

Highway

Wr = Wf/2

W| =Wf/2

Wo ~ Wf/32

a) Building with walls parallel and perpendicular to highway

Highway

b) Building with walls at oblique orientation relative to the

highway

Figure 9. Source-Receiver Geometry for Estimating Total Acoustic Energy

at the Exterior Surfaces of a Building

47
This is a simplified consideration, but it is surprisingly close to reality.

In reality, sound waves diffract or bend around physical objects so that just

because one cannot see a noise source visually, it does not mean that one will

not receive any acoustic energy. As a result, denoting Wf as the total energy

at the building facade facing the highway, one would estimate = W£=Wf/2

and Wq = 0 for ideal conditions or the more nearly correct results:

Wj. = Ng= Wf/(iT/2) and Wo=Wf/32 (Refs. 20 and 21). (The notations are as follows: Wf is the total energy incident upon the building facade facing the

highway; Wj. and W^is the total energy incident upon the facades at the right

and left end of the building; and Wq is the total energy incident upon the

building facade on the side opposite of the highway.)

Continuing the example, if the incident sound level at the location of the

building facade facing the highway is denoted as Lf, then the sound level at

either end of the building is Lj- = Lji= Lf -3 dB since the total energy is

decreased by a factor of 1/2. Using the other approximations one would

estimate: = Lg=Lf -2 dB and Lq = Lf -15 dB.

Finally, Figure 9(b) illustrates the effect of orientation of the building

relative to the highway. In this case, each of the facades is exposed to a different view of the highway, and one cannot simply state that a definite

relationship is apparent as it is for the geometry illustrated in Figure 9(a).

To evaluate conditions such as illustrated in Figure 9(b), it is necessary to

conduct additional analyses (Ref. 20).

The above example illustrates one form of noise mitigation at a site.

That is, the presence of the_ building altered the sound field at the site

relative to the sound field estimated for the flat site free of obstructions.

However, before discussing mitigation of noise, we must incorporate of aircraft

noise, if it is appropriate, and the existing noise levels at the site to

determine the total site noise exposure.

2.3 AIRCRAFT NOISE PREDICTION

Aircraft noise is an extremely important consideration for developing

noise-compatible land use both within the vicinity of the airport property and

along corridors underneath the flight paths serving the airport. The reason

for this importance is the extent of land area exposed to noise levels exceeding

Ldn = 65 dB due to aircraft operations. Whereas highway and railway noise is a consideration for land parcels located within a few hundred feet adjacent to

these sources, it is difficult to assign with confidence a comparable distance

for aircraft noise. The difficulty arises from the many factors that influence

noise generated by aircraft operations, and the noise exposure of the land area

To do this one must calculate levels in decibel units. See appendix B for a discussion of this. Also, it is important to note the words "incident

upon" since we are really interested in energy at a location in the physical

absence of the building.

48
surrounding the airport. A land located 2,000 to 3,000 ft adjacent to a runway

may be exposed to noise levels below Ldn = 65 dB, while another land parcel

located 2 to 3 miles from the end of a runway but underneath a flight path may be

exposed to noise levels exceeding Ldn “ 65 dB. As compared to either highway

or railway noise, the prediction of aircraft noise is a very complex process.

It is beyond the scope of the present guidelines to provide a noise prediction method for aircraft noise. However, a brief discussion of the com- plexities of the problem is worthwhile. The user should understand that both

accepted noise prediction methods and criteria are available to estimate the

nature of the problem (Refs. 9 and 10). The noise predictions are available

in terms of the DNL values, and can be obtained either for specif c locations

about the airport or as contours of constant Ldn values plotted to scale for

the land area surrounding the airport.

The Noise Source

Referring to the highway noise prediction method, it is sufficient to use

three types of vehicles to describe the noise generated by highway traffic (see

Table A). For railway noise prediction, it is sufficient to consider only

diesel-electric locomotive noise and railcar noise (see Table 10). However,

prediction of aircraft noise involves many factors. The Integrated Noise

Model (INM), developed by the Federal Aviation Administration ( FAA) , utilizes

over 40 aircraft types. Moreover, computed noise exposures are related to the

takeoff and landing conditions for each aircraft type. In particular, the

takeoff noise emissions are determined by the thrust required or the aircraft

takeoff weight. The takeoff weight will depend mainly upon the distance of the

flight (fuel load variations). Further considerations include the average

number of takeoff and landing operations in each direction for each runway

(local prevailing wind conditions), and the anticipated incorporation

of new technology in the design of commercial aircraft.

The picture is further complicated by the fact that not all aircraft

types operate at all airports. Yet, it is necessary to incorporate all the

details described above into an aircraft noise prediction model to estimate

specific local conditions.

Source-Receiver Geometry

In the case of highway and railway noise, the source-receiver geometry is

established by a single distance (see Figure 1) or by two distances in the case

of the railway warning horns (see Figure 5). In both instances, a straight

roadway or railway track alignment could be assumed and the results used for a majority of local conditions. This is not possible for aircraft noise prediction,

since aircraft may takeoff and land using various flight paths relative to the

end of a runway. Figure 10 illustrates one form of the source-receiver geometry

for aircraft noise prediction (Ref. 22).

49
Aircraft flight path

a) Aircraft takeoff operation

Figure 10. Basic Situations for the Calculation of DNL Due to Aircraft

Operations (Ref. 22)

50
Figure 10 also indicates that the aircraft flight paths may vary depending

upon whether the aircraft is taking-off or landing, and the air traffic control

patterns established for each airport. For any particular runway and heading,

multiple flight paths are possible. This means that for a fixed receiver

location on the ground, the source-receiver distance is variable as is the

noise emission of the source (aircraft type and operating conditions) . These

considerations complicate the prediction of aircraft noise exposure about

airports

.

Noise Propagation

Considering the source noise levels and the fact that the noise propagation

path is relatively close to the ground, both highway traffic and railway noises

attenuate rapidly with distance to sound levels below the outdoor criterion of

Ldn 55 dB.

However, due to the high noise levels associated with aircraft operations

(especially takeoff) and the direct line-of-sight propagation path between the

aircraft and the receiver, aircraft noise must propagate several thousand feet

to attenuate to levels comparable to other environmental noise sources.

The high-frequency components of the noise attenuate more rapidly with

distance than the low-frequency components. For a frequency-weighted noise

measure (such as the A-weighted sound level) averaged over an exposure time

(such as the equivalent sound level), the significant changes in the noise

spectrum shape with distance introduce an additional level of detail that must

be incorporated into the noise prediction method.

Ref. 22 is a manual method for estimating DNL values about an airport. In

order to incorporate some of the above considerations into the noise prediction

method, plots relating aircraft type, takeoff weight, and source-receiver distance

to the noise emission of a single aircraft operation are presented. To cover

all of the combinations, 271 plots are required!

Number of Operations

Perhaps the most easily understood aspect of noise prediction of airport

operations is the number of operations per day. As discussed above, the total

number of operations must be distributed among the various possible flight

paths and among the types of operation (i.e., takeoff and landing) for each

aircraft type. Further, for the DNL estimate, the operations must be accumulted

for both daytime and nighttime periods. In particular, the DNL considers

1 nighttime aircraft operation to be equivalent to 10 daytime operations. This

is identical to the adjustments applied to noise from traffic flow (Table 15)

and to noise from railway operations (Table 12) .

51
Noise Exposure of Land Areas

Given the many factors influencing the prediction of aircraft noise at a specific location, it is beyond the scope of these guidelines to describe a method. The above discussion is not intended to give the reader the impression

that prediction of aircraft noise is too complicated a problem to be analyzed.

On the contrary, the degree of complexity only means that the predictions must

be based upon a computer model that can incorporate the necessary details.

Approximate methods have been developed (Refs, 15 and 22), However, the user is

advised to obtain predictions from the local airport authority as these are based

upon accepted techniques (Ref, 9), The Integrated Noise Model ( INM) developed

by the Federal Aviation Administration provides the necessary prediction and

presents the results in both tabular and plotted formats. The L^n predictions

may be obtained for a specific land parcel or for the entire land area exposed

to specified levels of noise exposure. In the latter case, the prediction is

in the form of a plot of noise contours enclosing the exposed land area. Additional information provided includes the total land area exposed to noise

exceeding a specified level, and the cumulative exposure time above specified

threshold A-weighted sound levels by time of day,

2,4 EXISTING NOISE SOURCES

The present guidelines focus upon the noise generated by highway, railway,

and aircraft sources and the mitigation of this noise to evaluate noisecompatible land use. However, at any location, noise is always present and

may not always be identifiable with a specific noise source. These noises are called "existing noise sources" and they establish the "existing noise levels"

at the location. The existing noise levels are an important consideration for

determining the effect of increasing the total noise environment when introducing

an additional noise source.

Generally, it is necessary to establish the existing noise levels at a location by direct measurement (Ref, 4), However, analysis of existing noise

levels from measurements at over 100 locations within urban areas of the United

States has resulted in an approximate relationship between the existing DNL at

a location and the population density of the area surrounding the location

(Refs, 25 and 26), Before presenting these empirical results, it is worthwhile

to describe the basis for assuming that such a relationship exists.

Transportation noise studies indicate that surface transportation noise is

generally the greatest contributor to environmental noise. Highway traffic

noise is the predominant component of surface transportation noise. However,

traffic flow and conditions on a single local street may not independently

represent a significant source of noise. Within an urban area, many local

streets carry traffic serving the population residing within the area. The

number of automobiles per person is a constant value as is the ratio of trucks

to automobiles (see Tables 8 and 9), Although a single local street may not

represent a significant noise source, the noise propagating to a location

from several local streets combine to establish the total existing noise level.

Since the total traffic flow is approximately related to the local population,

52
It Is reasonable to assume that the total existing noise level may be related

to the local population or population density.

Table 17 presents empirical relationships between existing DNL at locations

in an urban area and the population densities within the surrounding urban

areas (Ref. 25). These results are based upon noise measurements conducted

in residential urban locations not directly attributable to any major noise

source such as major highways, railway, airports, or construction sites. In

the absence of direct measurements, the results in Table 17 may be used to assess the existing noise levels at a site located away from major noise sources

Table 17 also presents estimates of the equivalent sound level, Lgq,

for three time periods during the 24-hour period. These time periods are:

® early morning (2 a.ra. to 4 a.m.) (Ref. 26);

• nighttime (10 p.m. to 7 a.m.) (Ref. 26); and,

• daytime (7 a.m. to 10 p.m.).

The Lgq value for the daytime period is calculated using the DNL value and the

nighttime Lgq value for each population density. It should be noted that the

DNL value is 10 dB above the early morning Lgq value for each population density

This 10 dB difference emphasizes the 10 dB nighttime weighting utilized in the

definition of DNL.

2.5 ESTIMATION OF FUTURE CONDITIONS

Noise-compatible land use decisions are based on the evaluation of the

long-term noise impact that will result from the proposed action. Accordingly,

both the future noise environment that would result from a proposed action and

the future use of the noise exposed land areas must be evaluated. From yearto-year, the only factors that would normally remain constant are the noise

criteria and the methods used to establish the compatibility between the noise

environment and the expected land use.

The methods presented in Sections 2.1 through 2.4 provide a basis for

estimating the future noise environment. For example, if it is anticipated

that a highway will be expanded from two lanes to four lanes within the next

few years, then it is appropriate to estimate the noise environment based upon

both the existing conditions and the conditions that will prevail upon the

completion of the highway expansion. This predition would require estimates of

the future traffic flow characteristics and may require different distance

attenuation adjustments than those Indicated by Tables 6 or 7 . Similarly, an airport expansion may result in altered flight paths and aircraft mix, with

noise exposure changes for land areas surrounding the airport

.

In conducting these future estimates, it may be assumed that the highway

and railway noise source characteristics will not change significantly (see

Tables 4 and 10) in the foreseeable future. However, due to the introduction of new aircraft types into the fleet, it may be appropriate to account for this

53
Table

17.

Empirical

Relationships

Among

Population

Density,

DNL,

and

Nighttime

Measures

of

the

Existing

Noise

Level

(Refs.

25

and

26)

e E

•

Cl. o

(U I PQ J • T3 6

• CO

e

.

D- I <

01 • PQ

ij e T)

•a

o

^CNf0<rLTiv0t^00CT\O mioioiOLOiTimirim'.c

CN cO "H

•H e o o o o o o C C o c 4-J 4-J o o o o o o o O o o tC "H 0) iH CO rH o m o c o m c c o o

D c a c CM so c m 1-H o o m o

D. <U O

o -O 0) CL, ex

CM CM on m so 00

hJ c<

z xim CM n lO so CO <?s o

O I-J T3 so so so so sO so so so SO

cr • <1

0) CQ PC

hJ T3

I tN

o^mo

so so

CMsO

Ml- SO m

so

soso soocso o

fOm

'3' m

m

m

som

som m00m

osm

o

so cso

54

NOTE:

Two

L

0

q

values

for

the

nighttime

periods

are

estimated

from

Ref.

26.

The

L

0

q

value

for

the

daytime

period

is

calculated

using

the

DNL

value

and

the

Lgg

value

for

the

10p.m.

-7a.m.

time

period.
change when estimating aircraft noise exposure. As a result, the methods for

estimating highway and railway noise exposures described in Sections 2,1 and

2.2 should remain valid for the foreseeable future.

The tabular format used for the highway and railway noise prediction

methods is especially useful in estimating changes in the noise environment.

For example, Table A can be used to estimate DNL changes related to both

vehicle mix and traffic speed. Table 5 applies to changes in AADT and the

nighttime traffic flow, and Tables 6 and 7 apply to the number of traffic lanes

(consistent with the AADT estimate). Similar comments apply to the railway

noise prediction method. As a result, the expected change in the noise

environment may usually be evaluated simply by evaluating the change as indicated by a single table.

Depending upon the value of the future DNL, it remains a local policy

judgement as to the steps necessary to ensure future noise-compatible land use. The noise exposure estimates may indicate present-day compatibility but a future conflict. If the conflict is to be avoided, then mitigation measures

must be implemented. Since it cannot be assumed that the noise generated by

automobiles, trucks, or diesel-electric trains will dramatically decrease in

the future, mitigation techniques will generally be applied to the site

adjacent to the source.

The particular mitigation techniques to utilize are site specific. The

main considerations are the desirability to provide acceptable outdoor and

indoor environments and the practicality of achieving the required degree of

noise mitigation. The timing of- the implementation, however, may well depend

upon the choice of mitigation technique. If, for example, noise barriers are

to be utilized as a mitigation technique, and the barriers are to be constructed

with public funds on the right-of-way, then the noise barrier construction may

be scheduled at the time at which the noise environment is expected to exceed

the noise criterion. If, however, the migigation technique applies to private

property and involves the building noise insulation, it may be necessary to

implement zoning requirements and changes in the building code several years

prior to an anticipated noise conflict. The remaining sections of these

guidelines focus upon noise mitigation techniques and the noise-compatible

development of land.

2.6 NOISE PREDICTION WORKSHEETS

Within this section, blank worksheets are grouped together for convenience.

Worksheets are provided for predicting highway traffic and diesel-electric

railway noise. The worksheets reference, at each step, the appropriate lookup

table providing the required value or adjustment.

Highway Traffic Noise Prediction

Worksheet I is used. to estimate the noise generated by traffic flow on highways. Tables 4 through 7 provide the necessary data for this prediction

based upon the local traffic flow information. Tables 8 and 9 provide

55
representative values for annual average daily traffic (AADT) and values for

percent vehicle mix and nighttime vehicle operations.

Worksheet I is divided into three sections. The first section is simply a heading for inserting the project description, the person performing the

calculations and the date. The second section lists the local traffic information required to conduct the noise prediction. The user should obtain this

information from the State Highway Department. Data describing the distribution

of the annual average daily traffic (AADT) and nighttime distribution of traffic

by vehicle type may not be readily available. Representative values are presented in Tables 8 and 9 and may be used if local data are not available.

The third section of Worksheet I is for the actual noise prediction

calculation. The first two entries are values from the indicated lookup tables

using the traffic flow data in section two of the worksheet. The third entry

is an adjustment constant for either hard site or soft site conditions (see

Figure 2) . The value entered in step 4 is the simple addition of the values

in the first three steps, and represents the DNL at a location 50 ft from

the edge of the near lane of the highway. This is the reference value of DNL

for the highway traffic flow conditions.

Step 5 is the sound level adjustment added to the reference DNL value

to obtain the DNL value at the receiver location. The entry in step 5 is

obtained from Table 6 for hard sites and Table 7 for soft sites. The table

selected must correspond to the site condition as entered in step 3 and the

number of traffic lanes for the highway. The entry in step 6 is obtained by

adding the adjustment value in step 5 to the reference DNL value in step 4.

The DNL value obtained in step 6 is the DNL value at the receiver location

adjacent to the highway. The receiver location is measured from the edge of

the near lane of the highway (see Figure 1).

Section 2.1 presents examples illustrating the prediction of highway

traffic noise. Figure 3 and 4 are examples of completed worksheets.

Diesel-Electric Railway Noise Prediction

Worksheets II and III are used to predict noise from diesel-electric

trains. Worksheet II has two parts. The first part documents the basic data

required to estimate the characteristics of the "average train" used for the

noise prediction method. The second part documents the receiver location

measured away from track centerline and, if there is a warning point within

1/2 mi of the receiver, the receiver location measured along the track from

the warning point. These distances are illustrated in Figure 5.

Worksheet III is used to conduct the step-by-step calculations for the

noise prediction. There are three parts to this worksheet. Part I is used to

predict the DNL due to pass-by noise without warning horn. Part II is used to

predict the DNL due to warning horn noise, and Part III is used to combine the

pass-by DNL and the warning horn DNL to obtain the total DNL value due to

56
railway noise. If warning horn noise is not a consideration, Parts II and III

of this worksheet are not completed.

Tables 10 through 13 are used for the pass-by noise prediction and Tables

14 and 15 are used for the warning horn noise prediction. The data on Worksheet

II are transferred to Worksheet III and are used to obtain the appropriate

values from the lookup tables. Each step in Worksheet III indicates the lookup

table used to obtain a value or an addition to obtain a result.

If warning horn noise is a consideration, the DNL value is estimated in

Part II of Worksheet III. The pass-by noise and the warning horn noise must be

combined to obtain the total DNL at the site due to railway noise. The required

calculations are indicated in Part III and require the adjustments presented

in Table 16.

If highway traffic noise and railway noise are combined at a site to

obtain the total site exposure, the procedure is identical to that indicated

in Part III of Worksheet III. Figures 6 through 8 illustrate a completed set

of worksheets for the prediction of railway noise exposure at a site.

Existing Noise Levels

The determination of existing noise levels at a site should be based upon

empirical data. However, if measurements are not appropriate, the existing

noise levels may be estimated using the data presented in Table 17 if the

population density at the site is known.

57
WORKSHEET I. HIGHWAY TRAFFIC NOISE PREDICTTION

PROJECT:

Prepared by: Date:

Number of

traffic lanes

TRAFFIC FLOW INFORMATION

Average cruise

speed

Annual average daily traffic

AADT

mph vehicle/day

Vehicle type Percent of AADT Fraction operating at night

automobile & light trucks

medium trucks

heavy trucks

^nl

^n2

^n3

HIGHWAY TRAFFIC NOISE PREDICTION

Step in the prediction method Lookup Value from

Table lookup table

1. Traffic flow reference noise level A dB

2. Adjustment for AADT and nighttime traffic 5* dB

3. Adjustment for site conditions (Use -31dB none dB

for hard site; -3AdB for soft site)

A. Day-night noise level at 50 ft none dB

(Add values in Steps 1,2, and 3)

5. Adjustment for receiver at ft 6(hard site) dB

7(soft site) dB

6. Day-night noise level at receiver

(Add values in Steps A and 5) none dB

* If heavy trucks are present use fn3 in Table 5 If heavy trucks are not present use f.^2 Table 5.

If only automobiles and light trucks are present use fpj in Table 5.

58
WORKSHEET II. DIESEL-ELECTRIC RAILWAY NOISE PREDICTION DATA

PROJECT:

Prepared by: Date:

PART I DATA DESCRIBING THE AVERAGE TRAIN *

a) Train speed, S

b) Total number of trains per day: Nt

c) Total number of trains operating at night; Nj^

d) Total number of locomotives per day: Nl

e) Total number of railway cars per day: N,,

mph

(1) Calculate the average number of locomotives per train;

N = Nl/Nt =

(2) Calculate the average number of railway cars per locomotive;

n = Nc/Nl =

(3) Calculate the fraction of railway operations occurring during the

nighttime (10 p.m, to 7 a.m.)

fn - Nn/Nx =

PART II DATA DESCRIBING THE SITE LOCATION (see Figure 5)

a) Distance from track to site: D = ft

b) If there is a warning point within 1/2 mi of

the site, determine the distance along the track L = ft

from the warning point:

* The mathematical notation for the data follows the notation used

in Appendix A where the railway noise prediction model is described.

59
WORKSHEET III. DIESEL-ELECTRIC RAILWAY NOISE PREDICTION;

PASS-BY NOISE EXPOSURE

PART I DIESEL-ELECTRIC PASS-BY OPERATIONS

(1) From Table 10 and the data for the average train on Worksheet II

(N = ; n = ; and S = mph)

Reference sound level for one pass-by _ dBA

(2) From Table 11 the sound level adjustment for

N-p = trains per day dB

(3) From Table 12 the sound level adjustment for

fn = fraction of nighttime operations dB

dB

dB

dB

(4) Adding (1), (2), and (3) above, the day-night

sound level for railway pass-by noise at a location Dq = 100 ft away from the track

(5) From Table 13 the sound level adjustment for

the distance D = ft away from the

track centerline

(6) Adding (4) and (5) above, the day-night

sound level for railway pass-by noise at

a location D = ft away from the

track centerline

IF THERE ARE NO WARNING POINTS WITHIN 1/2 MILE OF

THE SITE, THE ABOVE RESULT (6) IS THE DAY-NIGHT

SOUND LEVEL AT THE SITE RESULTING FROM PASS-BY

NOISE OF DIESEL-ELECTRIC TRAINS.

IF WARNING HORN NOISE OCCURS, PROCEED TO PARTS II

AND III OF THIS WORKSHEET

60
WORKSHEET III. DIESEL-ELECTRIC RAILWAY NOISE PREDICTION

PASS-BY NOISE EXPOSURE

PART II WARNING HORN NOISE PREDICTION

(1) From Table 14 or Figure 5 at the location L = ft

along the track from the warning point and D = ft

from the track,

Reference sound level for one warning

(2) From Table 15 the sound level adjustment for

N-p = trains per day passing the site

at S = mph is

(3) From Table 12 the sound level adjustment for

f^ = fraction of nighttime operations is

(4) Adding (1), (2), and (3) above, the day-night

sound level for railway pass-by noise at a the location L = ft and D = ft is

PART III COMBINED PASS-BY AND WARNING HORN NOISE PREDICTION

The pass-by sound level and the warning sound leave must be

combined to obtain the total noise prediction at the location.

(1) From Part I; step (6) the pass-by day-nigth sound level is

(2) From Part II, step (4) the warning horn day-night sound

level is

(3) Using (1) and (2) above, the sound level difference is:

higher level - lower level =

(4) Using the sound level difference from step (3) and from

Table 16, the combined day-night sound level is:

higher level + adjustment =

THE RESULT (4) ABOVE IS THE COMBINED DAY-NIGHT SOUND

LEVEL AT THE SITE FOR RAILWAY NOISE
3. MITIGATION TECHNIQUES

By utilizing the methods described in Section 2, the total noise environment at a location may be estimated for the expected combination of noise

sources. This combination always includes the existing noise level and one or more of the transportation noise sources. The next step in the evaluation is

a comparison of the estimated noise levels with the noise compatibility criteria.

The compatibility of the intended land use is then determined based upon the

level of outdoor noise and indoor noise due to the outdoor noise. Since activities related to residential land use are generally the most noise-sensitive

activities, the noise criteria for residential land use are the most restrictive

criteria.

As indicated in Table 3, ideal criteria for residential land use are:

outdoor DNL less than or equal to 55 dB and indoor DNL (due to outdoor noise)

less than or equal to 45 dB. For outdoor DNL between 55 dB and 60 dB, residential land use is acceptable for outdoor activities and compatible for indoor

activities with normal construction and window open . However, if the outdoor

DNL exceeds 60 dB, additional steps or measures are required to achieve noisecompatible land use. The methods or techniques employed to achieve noisecompatible land use by controlling site conditions are called mitigation techniques and are discussed in this section. The mitigation techniques are classified in these guidelines according to their application to either outdoor

conditions or indoor conditions. Generally, the mitigation of outdoor noise

may result in a decrease in indoor noise levels. However, the reduction

of indoor noise levels caused by outdoor noise sources will do nothing to

improve the outdoor noise environment.

Before presenting the details of specific noise mitigation techniques, it

is worthwhile to illustrate the significance of the problem, and to present a brief discussion of the physical principles that determine mitigation effectiveness ,

Existing Noise Levels

Table 17 is an empirical relationship between existing noise levels and

population density for residential urban areas. These results indicate that

the outdoor DNL will exceed 55 dB for areas with a population density greater

than 2,500 people/mi^ and will exceed 60 dB for areas with a population density

greater than 8,000 people/mi^. Since these DNL values are associated with

noise from unidentified sources, it is impossible to specify an appropriate

mitigation technique for the outdoor environment. Fortunately, at these levels,

noise exposure is not usually significant. However, mitigation of noise indoors

due to the outdoor existing noise environment is possible. These mitigation

techniques require that windows be closed and that the building envelope provide

an adequate degree of noise isolation . As an indication of the significance of

the existing noise levels and the possible need for mitigation, the Ref. 25

study estimated that in 1974, approximately 80 percent of the United States

urban population resided in areas exposed to DNL exceeding 50 dB and 40 percent

were exposed to DNL exceeding 60 dB.

62
Physical Aspects of Outdoor Noise Mitigation

These guidelines provide quantitative estimates of the effectiveness of

various noise mitigation techniques. The effectiveness is stated in terms of a level reduction value expressed in A-weighted dB units. For example, if the

outdoor DNL at a receiver location is estimated to be Ljn 67 dB and the

introduction of a noise barrier between the source and receiver provides a level reduction of 12 dB, then the DNL at the location of the receiver with the

barrier in place is Ljn “ 55 dB.

Figure 11 illustrates the concept of determining a level reduction for an outdoor location in the presence of several different source-receiver paths

typical of a residential development. To estimate the A-weighted level reduction, one must use lengthy calculations based upon a knowledge of the frequency

content of the source, the specific site geometry, the acoustic characteristics

of reflecting surfaces, and average these effects over time. Such an approach,

however, is too cumbersome for the purposes of these guidelines.

The approach used to estimate the A-weighted level reduction for various

mitigation techniques is to provide lookup tables and empirical results that

apply to typical source-receiver conditions. These results may then be applied

to estimate the mitigation effectiveness. If the actual site conditions do not

correspond to the typical source-receiver conditions, it then becomes necessary to employ more refined calculations if the situation warrants the effort.

Technical appendices to the present guidelines are provided for this purpose.

Two physical aspects of outdoor noise mitigation are the diffraction or bending of sound waves around an object and the scattering or reflection of

sound waves from an object. Figure 12 illustrates these two physical aspects

of noise mitigation. In general, the diffraction of sound results in a positive degree of noise mitigation if the receiver is in the "shadow zone" behind

a barrier. Scattering of sound may result in either a positive or negative

degree of noise mitigation. If sound is scattered so that the total energy at

the receiver decreases, the mitigation effectiveness is positive. If the

sound is scattered or reflected toward the receiver so that the total energy

reaching the receiver is increased, the mitigation effectiveness is negative.

Except for extreme conditions, the effects of scattering or reflection may be

ignored without introducing significant error in estimating the mitigation

effectiveness. For the purpose of these guidelines, rules of thumb and examples

of poor site design are presented to avoid problems related to reflections.

3.1 OUTDOOR NOISE MITIGATION

The mitigation of outdoor noise depends upon the noise sources causing the

site noise exposure. The degree of mitigation effectiveness required to achieve

a desired criterion depends upon the distance between the noise source and the

receiver. Figure 13 presents the basic considerations using a rather extreme

example of site noise exposure. Unless the aircraft noise exposure is below

the criterion for total noise exposure, very little may be accomplished to

achieve any degree of outdoor noise mitigation other than increasing the distance between the aircraft flight path and the receiver. For the railway

63
a) Clear site conditions

All sound is received

directly from the source

Combined sound level

is Lciear

Received sound

direct, diffracted,

and reflected

Combined sound level is L built-up

Receiver insertion loss = Lciear “ l-built-up» cl^

b) Built-up site conditions

figure 11. Propagation of Highway Noise to Receiver: Site Insertion Loss.

64
Reflected sound

Diffracted sound

'Shadow zone'

(below line-of-sight)

M _ i_\

a) Direct, reflected, and diffracted sound for thin screen barrier

b) Reflected sound reaching receiver decreasing barrier effectiveness

c) Sound scattered by dense vegetation

Figure 12» Illustration of Diffraction, Reflection and Scattering of

Sound by Objects next to Highway

65
66
pass-by noise exposure and the highway traffic noise exposure, it may be

practical to introduce a barrier between the receiver and these sources to

achieve the desired degree of mitigation effectiveness. These guidelines

describe the necessary considerations, and present a quantitative method for

estimating highway noise mitigation effectiveness using barriers.

Highway Traffic Noise Barriers

The mitigation effectiveness of highway traffic noise barriers is determined

by the geometry relating the highway noise source location relative to both the

top of the barrier and the receiver location. To be effective, the receiver

location must be such that the receiver is totally shielded by the barrier

(i.e., the barrier blocks the direct line of sight between the source and receiver).

This shielding must consider all possible lines of sight between the source and

receiver both in elevation and in the horizontal direction. Figure 14 illustrates

the concepts of the relative source-receiver geometry and the degree of shielding

provided by a barrier.

A specific barrier design considers alternative configurations of sourcereceiver geometry. First, the source height is established for the traffic flow.

This is achieved by assigning a source height for each vehicle type in the

traffic flow as follows; automobiles and light trucks, source height is 0 ft; for

medium trucks, source height is 2.3 ft; and for heavy trucks, source height is

8 ft. These heights are measured relative to the pavement elevation and have

been established from noise emission characteristics of vehicles. The above

values for the source heights are accepted values used in barrier design

(Refs. 6, 7, and 8). Since heavy trucks generate the highest noise levels and

the source height is 8 ft above the pavement (i.e., exhaust noise dominates), the

barrier height must generally be greater for a condition with trucks present in

the traffic flow than for a condition without heavy trucks present.

Next, the barrier length must be established so that the receivers are adequately shielded from noise generated by vehicles moving along the highway

alignment. As indicated in Figure 14, the distances between the source and the

barrier and the source and the receiver are also important geometric variables . This leads one to realize that for a barrier located at a fixed distance from

the near edge of the pavement, the barrier effectiveness may depend upon the

number of traffic lanes and will certainly depend upon the receiver locations

away from the highway and each receiver elevation relative to the highway and

the top of the barrier. Established methods are available to estimate the

barrier effectiveness as a mitigation technique for highway noise (Refs. 6, 7 and 8) and to provide an optimized design considering all receiver locations

behind the barrier (Ref. 27). However, these design-oriented methods are too

combersome for these guidelines.

Estimation of Barrier Mitigation Effectiveness

For the purpose of these guidelines, it is appropriate to utilize a somewhat restricted approach to estimating barrier effectiveness as a mitigation

67
-T— • Noise source

{source height

1

\

r

Barrier n -r—

height ^ t Receiver

f A I height

Sourcer-barrier

distance ^ ^SoiLTce-recelver distance »

a) Source-barrier-receiver geometry

^

1

1

1

O =O^ 1 11 II

No shielding

of receiver

Shielded

receiver

b) Source-receiver relationship in elevation

Figure 14 . Source-Barrier-Receiver Relationship

68
technique for highway traffic noise. The restrictions generally apply to the

geometry relating the source and receiver locations relative to the barrier.

Consistent with the highway traffic noise prediction method, it is assumed

that the highway is comprised of several traffic lanes, has a straight alignment,

and that the entire site is flat. The barrier is located at a fixed distance

from the pavement edge next to the site. The barrier is of constant height and

also extends indefinitely in both directions parallel to the highway. (The

barrier may be considered to be of Infinite length if it extends to either side

of the receiver a distance equal to four times the receiver distance behind the

barrier.) The receiver is located behind the barrier at various distances

measured from the barrier. The receiver height is assumed to be 5 ft above

ground elevation . (This is an average ear height for people standing.)

With these restrictions. Table 18 has been prepared for use in estimating

the highway traffic noise mitigation that would result from building a barrier

between the highway and various receiver locations. The values listed in

Table 18 are "barrier insertion loss" values and represent the approximate

A-weighted level reduction for traffic noise. Table 18 comprises three subtables with each subtable corresponding to different vehicle mixes in the

traffic flow. This accounts for vehicle source height differences. For each

subtable, the barrier geometry is defined in terms of barrier height and the

distance from the edge of the pavement to the barrier. The receiver elevation

is 5 ft above the ground elevation.

For a given barrier geometry and traffic flow, the barrier insetion loss

is estimated from Table 18 as an average value and a positive or negative

adjustment. This average value and the magnitude of the adjustment are based

upon more extensive calculations incorporating both receiver location behind

the barrier and from one to eight traffic lanes for the source locations.

Since the near traffic lanes essentially establish the barrier insertion loss,

the notes to Table 18 indicate that the value of the barrrier insertion loss

are obtained only on the basis of the receiver location. The average value

applies to receiver locations from 100 ft to 500 ft behind the barrier . If the

receiver is within 100 ft of the barrier the insertion loss is the average

value plus the adjustment. If the receiver is located beyond 500 ft behind the

barrier , the insertion loss is estimated as the average value less the adjustment. An example will illustrate the use of Table 18.

EXAMPLE 5. We had previously estimated highway traffic noise at a site exposed

to noise from all vehicle types for a receiver located 300 ft from the near

edge of the pavement. The highway traffic noise was estimated to be

Ldn = 67 dB for a hard site and 61 dB for a soft site.

We desire to estimate the at the receiver for a 10-ft high barrier

located 25 ft from the edge of the pavement. Since the barrier is 25 ft from

the pavement and the receiver is 300 ft from the pavement, the receiver is

located 275 feet behind the barrier. From Table 18(c), with a barrier height

of 10 ft and a barrier distance of 25 ft, the value listed is 7.5 i 2.0 dB.

Since the receiver is located between 100 ft and 500 ft behind the barrier, the

estimated barrier Insertion loss is 7.5 dB. Then, the estimated DNL value with

69
Table 18, AVERAGE BARRIER INSERTION LOSS ± ADJUSTMENT IN dB FOR HIGHWAY

TRAFFIC NOISE SOURCE WITH RECEIVER HEIGHT AT 5 ft

Average value is for locations from 100 ft to 500 ft behind barrier; use a positi^

adjustment for locations within 100 ft and a negative adjustment beyond 500 ft

a) Automobiles and light trucks only

Barrier Distance from edge of pavement to barrier, ft

height, ft

25 50 75 100

8 11.0 ± 1.5 9.5 ± 0.5 8.5 ± 0.5 7.5 ± 0.5

10 14.0 ± 1.5 12.5 ± 1.5 11.0 ± 2.0 9.5 ± 0.5

12 15.5 ± 1.0 14.5 ± 1.5 13.5 ±2.0 12.0 ±2.0

16 17.5 ± 1.0 16.5 ± 1.0 16.0 ± 1.5 15.0 ± 1 .5

b) Automobiles, light trucks, and medium trucks only

Barrier Distance from edge of pavement to barrier, ft

height, ft

25 50 75 100

8 9.0 ± 0.5 8.0 ± 0.5 7.5 ± 0.5 7.0 ± 0.5

10 12.5 ±2.0 11 .0 ± 2 .0 10.0 ±2.0 8.5 ± 1.0

12 14.5 ±2.0 13.0 ±2.0 12.0 ±3.0 11 .0 ± 2 .0

16 17.0 ± 1.0 16.0 ±2.0 15.0 ±2.0 14.0 ±2.0

) Automobiles, light trucks medium trucks, and heavy trucks

Barrier Distance from edge of pavement to barrier, ft

height, ft

25 50 75 100

8 6.0 ± 0.5 6.0 ± 1.0 6.5 ± 1.0 5.5 ± 0.5

10 7.5 ± 2.0 7.5 ± 2.0 7.5 ± 2.0 6 .5 ± 1 .5

12 10.5 ±3.5 10.2 ±3.5 10.0 ±4.0 8.0 ± 2.0

16 14.5 ±3.0 13.0 ±4.0 12.5 ±4.0 11 .5 ± 3.5

70
the barrier is 67 ,0 - 7 ,5 = 59 ,5 = 60 dB for a hard site and 61 .0 - 7 .5 = 53.5 = 54 dB for a soft site.

Due to the nature of the approximation and averaging used to develop Table

18, the question arises as to how close the estimate is to the more detailed

calculation. For the receiver location in the above example, the more detailed

evaluation would estimate the barrier insertion loss to be 6 dB rather than

7.5 dB. As a result, the more detailed calculation would yield estimated DNL

values of 61 dB for a hard site and 55 dB for a soft site. This 1 dB difference

in DNL with the barrier in place is reasonable given the approximate nature of

the barrier insertion loss values tabulated in Table 18.

When using the values presented in Table 18, the approximations used should

be recognized. The differences between the tabulated values and the estimates

obtained by the more detailed calculation procedure will be greatest for receiver

locations within 100 ft of the barrier. The reason for this is that the barrier

insertion loss decreases significantly from its highest values close to the

barrier to a lower value at 100 ft from the barrier.

Finally, it must always be remembered that the values listed in Table 18 are for a barrier of constant height that extends along the entire highway

alignment. In practice, barriers will not extend the entire length of the

highway but will only shield a site from the highway directly adjacent to the

site. Unless the barrier incorporates corner segments at its ends, sound will

diffract or bend around the ends of the barrier as well as over its top, and the

barrier performance may be decreased for the source-receiver location. Figure

15 illustrates an example of barrier design that may be used to Increase the

mitigation effectiveness to the levels indicated in Table 18.

Barrier Construction

Highway traffic noise barriers may be constructed using various materials

and techniques. The selection of materials or techniques is based upon local

construction practices, cost, and aesthetics. As related to acoustic performance, however, the barrier material should exhibit sound transmission loss

characteristics (this term will be described below in the subsection concerning

the building envelope) sufficient to attenuate sound passing through the barrier,

and the construction methods should ensure that no gaps or cracks are present

that allow noise to pass through the barrier unattenuated. Specific considerations are design details beyond the scope of these guidelines (Refs. 28 and

29). As a general guide, the sound transmission loss of the barrier material

should be at least 10 dB greater than the value for the barrier insertion

loss. Table 19 is a partial listing of the A-weighted sound transmission loss

values for materials that may be used for barrier construction (Ref. 28).

Natural Terrain and Berms

Often, natural terrain will obstruct the direct line of sight between

the source and the receiver or berms will be constructed to block the line of

71
Highway

72

b)

Site

shielded

by

finite

length

barrier

with

comer

segments

to

increase

mitigation

effectiveness
Table

19

Materials

for

Use

In

Barrier

Construction

(Ref.

28) ES

Uiu

c;a

03

0)03 •Hocu9 co

•H <;

CD OQ

CD “O

CO 03 c

CO

O

H

0)c^ c

CJ ' £H

•t3y

C o u 4J •3

to * CO 3 CO CO c •3 bc

y

Ui •3 *3 AJ

a

yy c CO

Oj 0) CD •H o o; CJ CO c CD CO bo E u •H 3 3 > *3 C4-I • o y u a bc 1 4J AJ .c

bCO Ui 0) » 3 c > y « 3 y c 0 (0 u C TJ '3 y o CO •o AJ y O’ CO o ^ o o •H 0) C y o u 1-1 c c 1-1 y iH y H bO -O M-l a M CO V3 a y CO < 4-t u 3

•9oo

"DOo

T3

o;

CQ T5

0)

•9Oo

to CO *0 bC fiC tC

0) ^

4J CO

01 >

O. CD E CD O O U *H

0)CO

OE «

CD

CO ^E

CD CO

CJC

•D CO <H U > 4-» Ou *o a o; GO X

CN bc

0> I ft: <

73
sight as a noise-mitigation measure. The values in Table 18 may be used, with

an adjustment, to evaluate the insertion loss for these conditions provided

that the terrain or berm is generally parallel to the highway, and that it is at

a constant elevation relative to the highway-receiver locations. The values of

insertion loss for berms of this geometry are obtained by adding 3 dB to the

insetion loss values determined by using Table 18 for a barrier of the same geometry (Ref. 6).

Vegetation

As indicated in Figure 12, vegetation can result in a scattering effect on highway traffic noise propagation with a resulting decrease in sound level in excess of the levels predicted for the clear site. However, the effect is

significant only for very dense vegetation from ground level to heights exceeding

10 ft, and for a minimum distance of 100 ft between the source and the receiver.

Furthermore, the foliage must remain on a year-round basis. As a guide, one may attribute excess attenuation due to vegetation on the basis of 5 dB per

100 ft of dense vegetation between the highway and the receiver (Ref. 8).

However, it is good practice to assume that vegetation does not provide

additional or excess noise attenuation unless site-specific field measurements

are available. Indeed, planting trees on top of berms for aesthetic purposes

may degrade the noise mitigation effectiveness of the berm due to the noise

scattering effect of the foliage (Refs. 30 and 31).

Privacy Fences and Courtyards

Figure 16 illustrates the concept of utilizing privacy fences and courtyards as an outdoor noise mitigation technique. Both the privacy fence and the

courtyard are really just another form of noise barrier placed between the noise

source and the outdoor receiver location. Their effectiveness as a noise

mitigation technique depends upon the relative geometry of the source and the

receiver. In contrast to the highway noise barrier, the sheilded area is rather

small, and the fences or courtyards must be incorporated into the building

design. Since the shielded area is adjacent to the building, the consideration

of reflections from the building exterior surfaces must be incorporated into

the estimate of the mitigation effectiveness (see Figure 12).

The available design methods for estimating the noise-mitigation effectiveness or insertion loss are limited to acoustic scale model measurements or field measurements (Refs. 32 and 36). These results, however, must be applied

with careful judgement since the insertion loss estimates are expressed in

terms of various noise descriptors not totally compatible with the Ljn descriptor

used in these guidelines.

As a general guide, a privacy fence could provide an insertion loss of

3 dB and a courtyard a maximum of 6 to 10 dB in the Ljn value for the clear

site if properly designed. These approximate values apply to the area enclosed

by the fence or the courtyard and the building.

74
a) Privacy fence (solid wall, note fence height relative to receiver height)

Figure 16. Conceptual Examples of Privacy Fences and Courtyards
Buildings as Noise Barriers

A house or building will provide shielding from a highway or railway source.

As described above for privacy fences and courtyards, the land area shielded

from the source and the magnitude of the mitigation effectivness are site

specific. The geometric factors are the distance between the building and

highway, the orientation of the building relative to the highway, the building

length and width, the sound absorption characteristics of the building surfaces,

and the proximity of other building surfaces that may reflect sound toward the

shielded receiver location. Figure 17 illustrates the geometric concepts.

The degree of shielding or insertion loss provided by a building varies

from point to point about the building. The calculations required to estimate

the insertion loss are very complex in a strict technical sense. However,

simplified approximations, suitable for preliminary estimates, are possible

(Refs. 36 and 37). These approximations are based upon the concept of

"geometric" or "ray acoustics" and do not incorporate diffraction of sound

around the ends or over the top of buildings. Since the significant shielding

occurs on the side of the building opposite the highway and rather close to

the building surface, ignoring the sound diffraction over the top of the building

is not a bad approximation even for single-story houses.

The estimation of the insertion loss provided by a building cannot be

formulated in a convenient lookup table format. Appendix B.2 is provided in

these guidelines for estimating the insertion loss of a single building in the

absence of reflections of sound. These calculations allow the user to estimate

the insertion loss on a point-by-point basis or to estimate contours of constant

insertion loss for the area behind the building. The only general conclusion

from these estimates is that the contour of 3 dB insertion loss is a semicirle

with diameter equal to the building dimension parallel to the highway. This

contour is illustrated in Figure 17. For any location within the semicirlce,

the insertion loss is greater than 3 dB.

3 .2 INDOOR NOISE MITIGATION

Section 3.1 addressed the mitigation of outdoor noise for locations on a site exposed to transportation noise sources. The outdoor noise mitigation

techniques apply only to highway or railway sources and are limited in

effectiveness to 15 dB or less. This section of the guidelines addresses the

mitigation of noise received indoors due to outdoor noise sources. The term

"indoor noise mitigation" applies only to the noise transmitted through the

building envelope that is generated by the highway, railway, or aircraft sources described in Section 2 .

The ability of the building envelope to attenuate outdoor noise is only

one aspect of the overall envelope design criteria. Other design considerations

focus upon the thermal performance, daylighting requirements, accessibility,

and aesthetic values. As a result, the architect must develop an integrated

envelope design that satisfies all criteria. These guidelines address the

acoustic performance of the building envelope, and describe the implications of

achieving the acoustic performance as related to other envelope design criteria.

76
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Before describing the method for estimating the acoustic performance, it is

necessary to introduce some terminology and to give the user an understanding

of the physical aspects of the problem.

Terminology

These guidelines utilize the A-weighted sound level difference as the

measure of the effectiveness of the indoor noise mitigation. If the outdoor

noise level is 70 dBA and the indoor noise level in a room due to the outdoor

noise is 50 dBA, the A-weighted sound level difference of 20 dBA characterizes

the acoustic performance of the portions of the envelope surrounding the room. By using the A-weighted sound level difference, it is generally not possible to

associate a single number with the acoustic performance of a dwelling and expect

the single number to characterize all combinations of outdoor noise sources. For example, a field measurement program may establish that a given building

exhibits a 23 dBA sound level difference for traffic noise and a 28 dBA sound

level difference for aircraft noise. There is nothing wrong with the field

measurements. The apparent discrepancy (which is a true characterization of

the acoustic performance of the envelope) is mainly attributable to the difference in the spectral shapes between the two noise sources and source location relative to the building surface, rather than either a faulty field

measurement or the physical characteristics of the building construction.

Figure 18 summarizes some of the considerations.

The A-weighted sound level difference is an example of a noise isolation

rating of the building. In fact, the noise isolation depends upon the noise

source characteristics, the site conditions (such as building orientation

relative to the noise source), the building envelope construction, and the

sound absorptive characteristics of the room in which the indoor sound level

is received or measured.

The building envelope construction does not uniquely define the Aweighted noise isolation provided by the building envelope. However, the

construction details do play the most significant part in determining the Aweighted noise isolation performance of the envelope.

Obviously, to characterize uniquely the noise attenuation of a building

envelope, one needs a description that is independent of all factors other than

the construction details. Such a description is called a noise insulation

rating. For these guidelines, the A-weighted sound transmission loss or A-weighted TL is utilized as a noise insulation rating as described below.

This terminology may appear, at first, to be just a play on words.

However, it is very important to understand the difference between a noise

isolation rating and a noise insulation rating. A noise isolation rating

(such as the A-weighted sound level difference) incorporates all factors

particular to the noise-source receiver relationship that effect a change in

the acoustic environment at the receiver. A noise insulation rating incorporates only the details of the building envelope construction and is

independent of all other factors. Knowing the noise source characteristics.

78
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the building site conditions, and the acoustic characteristics of the receiving

room, the building envelope noise isolation may be estimated from the noise

insulation characteristics of the envelope construction.

A-Weighted Sound Transmission Loss

The noise insulation of building construction* is determined using

standardized laboratory measurements (Refs. 38 and 39). The laboratory measurements are conducted to ensure that the noise insulation data are independent of

the acoustic conditions on each side of the construction. The resulting data

are called sound transmission loss data and are determined for a wide range of

test frequencies. These data may then be used to estimate the noise isolation

performance of the building construction.

The procedure for relating the noise isolation in the built environment

to the laboratory noise insulation performance of building construction is a complicated process. The complications arise from the complexity in describing

the outdoor noise environment which strictly, should include the frequencydependence of the noise sources, the noise propagation, and the scattering of

the sound field at the exterior surfaces of the building. Such a procedure is

totally unsuited for the purposes of these guidelines as it is too cumbersome.

In order to simplify the procedure for relating the noise insulation of

building construction to the noise isolation performance of the building

envelope, the first step is to develop an appropriate single number rating

that accounts for the frequency dependence. Several rating schemes have been

developed in the past just for this purpose (Refs. 40,41 and 42). Each of

these ratings combine the frequency dependence of the outdoor noise source with

the frequency dependence of the sound transmission loss characterisitcs of the

construction to establish the single number rating. In each case, the objective

of the rating is to estimate the indoor A-weighted sound level using the outdoor

A-weighted sound level and the single number rating.

In developing these rating schemes, the frequency dependence or spectrum

shape of the outdoor noise must be taken into account. This has been accomplished by utilizing outdoor noise spectra representative of transportation

noise sources. The result is then an average rating representing an expected

performance for each type of building construction. The effect of the outdoor

noise spectrum shape in establishing the single number rating is embedded in

the averaging process.

Based upon the above considerations, these guidelines also utilize a single

number rating scheme for estimating the A-weighted sound level difference

achieved by the building construction. However, the approach taken is to

establish the rating by considering the outdoor noise spectrum shape and the

The construction may be either a single component (such as a light

frame wall) or a composite construction (such as a wall with windows and doors)

80
sound transmission loss characteristics of the construction to be independent.

Details of the procedure are presented in Appendix C. The method characterizes

the outdoor noise spectra using representative data for aircraft, railway, and

highway traffic noise just as the previous methods (Refs, 40,41 and 42). The

highway traffic noise spectra are based upon the vehicle noise emission

characteristics of the FHWA STAMINA model (Ref. 8), and the aircraft and railway

spectrum shape is taken as the average developed by the National Research

Council of Canada (Ref, 42).

Accordingly, the rating scheme used in these guidelines comprises two

numbers: one for highway traffic noise and another for aircraft and railway

noise. Strictly speaking, these ratings are noise isolation ratings since

they combine an average outdoor noise spectrum shape with the sound transmission

loss characteristics of the construction. However, since the rating attempts

to preserve the independence of the outdoor noise spectrum shape and the sound

transmission loss characteristics of the construction, the ratings in these

guidelines are called the A-weighted sound transmission loss values of the

construction

.

Tables 20 through 26 provide a listing of A-weighted sound transmission

loss values of typical building construction. Each table corresponds to a specific component of the building envelope such as exterior walls, windows,

doors, and roofs. For windows, single-glazed, double-glazed, and triple-glazed

data are provided. In each table a description of the construction and two

values for the A-weighted sound transmission loss is given. The value corresponding to the "composite transportation noise” applies to aircraft and

railway noise and is based upon the reference spectrum shape developed by the

National Research Council of Canada (Ref. 42). The value corresponding to the

"traffic noise" is based upon the FHWA spectrum as described in the Appendix C.

The data contained in Table 20 through 26 are noise insulation data. The

necessary steps to estimate the noise isolation of a building envelope are described below. The data in Tables 20 through 26 are used for this purpose.

Sound Transmission Loss of Building Construction

Before describing the method for estimating the building envelope noise

isolation , it is worthwhile explaining the physical aspects of the problem.

Since the discussion will touch on several different topics before they are all

related, it must be remembered that the objective is to relate the sound

transmission loss characteristics (noise insulation value) of the construction

to the building envelope noise isolation characteristics. With this objective in

mind, the first aspect to be considered is the definition of sound transmission

loss .

81
Table 20. Average A-weighted Sound Transmission Loss of Exterior Walls*

Description A-Weighted Transmission Loss

Composite transportation

noise

Traffic

noise

Metal and curtain walls with insulation

between 2 sheets of galvanized steel; area weight less than 6 Ibs/ft^,

28 25

4 - 7 in masonry wall: either 4x8x16 concrete

blocks or mortared bricks without finish. 36 35

4 - 7 in masonry wall: 4x8x13 3-cell concrete

block; resilient channels 24 in o.c.; 1/2 in

plaster board. 40 39

7/8 in stuccoed wall: No. 15 felt building

paper and 1 in wire mesh; 2x4 wood studs

16 in o.c. with fiberglas building insulation; 1/2 in gypsum board screwed to channel.

43 40

8 in dense concrete wall: 3-cell concrete

block; perimeter sealed.

41 40

8 in masonry wall: either bricks mortared

together or 3-cell concrete blocks with

block filler; 1/2 in plaster; finished

with latex paint.

45 43

8 in masonry wall: 18x16x8 3-cell concrete

blocks; resilient channels 24 in o.c.; 1/2 in

gypsum board screwed to channels; painted

both sides.

46 47

8 in double brick wall: 4-1/2 in each

separated by 2 to 4 in cavity; wire

ties; 1/2 in plaster on exposed sides.

48 47

Light frame wood wall with 2x4 wood studs 31 29

16 in O.C.; 2 to 3 in insulation; 1/2 in

gypsum board.

* The data shown here were compiled from many sources and represent the average

performance for the type of construction described.

82
Table 21. Average A-weighted Sound Transmission Loss of Exterior Walls

with Windows*

Description A-Weighted Transmission Loss

Composite transportation Traffic

noise noise

Light frame wall with wood siding: 2x4 wood 27

studs with insulation; resilient channels

24 in O.C.; 1/2 in gypsum board; penetrated

by 25 to 30-percent single-glazed sealed

glass

.

Light frame wall with wood siding: 2x4 wood 30

studs with insulation; resilient channels

24 in O.C.; 1/2 in gypsum board; penetrated

by 25 to 30-percent single-glazed sealed

glass with storm sash.

Light frame wall with brick veneer or wood 30

siding: 2x4 wood studs 16 in o.c. with

fiberglas insulation; penetrated by 10 to

15-percent single-strength glazed sealed

glass

.

Light frame wall with wood siding or brick 31

veneer: 2x4 studs with insulation; resilient

channels 24 in o.c.; 1/2 in gypsum board;

penetrated by 25 to 30-percent single-glazed

sealed glass with storm sash.

26

28

29

29

* The data shown here were compiled from many sources and represent the average

performance for the type of construction described.

83
Table 22. Average A-weighted Sound Transmission Loss of Single-Glazed

Windows*

Description A-Weighted Transmission Loss

Composite transportation

noise

Traffic

noise

3/32 to 7/16 in thick glass pane:

0 unsealed 18 17

0 sealed 23 22

Single-strength pane with storm sash:

0 unsealed 24 22

0 sealed 28 26

* The data shown here were compiled from many sources and represent the average

performance for the type of construction described.

84
Table 23. Average A-weighted Sound Transmission Loss of Double-Glazed

Windows*

Description A-Weighted Transmission Loss

Composite transportation Traffic

noise noise

Parallel panes of same thickness

(range: 3/32 to 1/8 in) mounted in

1 sash and sealed. Interpane spacing:

° < 1/2 in 25 24

° > 1/2 in 26 25

Panes of different thickness (1/8

and 1/4 in) mounted in 1 sash and

sealed

:

° in parallel with spacing of

1/2 to 3/4 in 28 27

“ not in parallel with maximum

spacing 3/4 in and minimum

spacing 1/4 in

28 27

Parallel panes of same thickness

(range: 5/32 to 1/4 in) mounted in

2 sash in parallel and sealed.

Interpane spacing:

° 2 1/2 - 4 in 35 31

° 3 - 6 in 36 32

° > 6 in 38 33

Panes of different thickness (1/8 and

1/4 in) mounted in parallel in 2 sash

and sealed. Interpane spacing:

° 1 to 1-1/2 in 30 29

° 1-1/2 to 2 in 33 30

° 2-1/2 to 6 in 37 33

* The data shown here were compiled from many sources and represent the

average performance for the construction described.

85
Table 23. Average A-weighted Sound Transmission Loss of double-Glazed Windows*

(Continued)

Description A-Weighted Transmission Loss

Composite transportation Traffic

noise noise

Panes of different thickness (1/8 and

1/4 in) mounted in 2 sash not in

parallel and sealed. Interpane spacing:

Maximum, in Minimum, in

3 1 33 31

3 2 34 31

3 2 36 31

Panes of

1/32 in)

sash and

same thickness (1/8 or mounted in 2 non parallel

sealed. Interpane spacing:

Maximum, in Minimum, in

3 1 34 30

6 2 36 31

86
Table 24. Average A-weighted Sound Transmission Loss of Triple-Glazed Windows*

Description A-Weighted Transmission Loss

Composite transportation Traffic

noise noise

1/8 in thick panes mounted in 1 wood sash with interpane spacings

ranging from 1/8 to 13/32 in.

Sealed

.

2 panes 1/8 in thick mounted in

1 wood sash with an interpane

spacing of 1/4 in and metal

spacer. Third pane 1/8 in

in separate wood pane 3/4 to

2 in apart. Sealed.

2 panes 1/8 in thick mounted in

1 sash with an interpane spacing

of 1/4 in and metal spacer. Third

pane either 1/8 or 1/4 in thick

mounted in separate wood sash

3/4 - 2 in apart. Sealed.

2 panes 1/8 in thick mounted in

1 wood sash with interpane spacing

of 1/4 in and metal spacer. Third

pane 1/4 in separate wood sash

1 - 2 in apart. Sealed.

1/8 in panes mounted in 2 wood sash.

First interpane spacing 1/4 in,

second 4 in. Metal spacer. Sealed

25 24

30 28

32 30

34 32

37 33

* The data shown here were compiled from several sources and represent the

average performance for the construction described.

87
Table 25. Average A-weighted Sound Transmission Loss of Doors*

Description A-Weighted Transmission Loss

Composite transportation Traffic

noise noise

Hollow core wood door with weather

stripping.

15 14

Solid core wood door with weather

stripping.

21 20

Solid core wood door, weather stripped,

and fully sealed.

25 24

Glass containing doors (French and

sliding) weather stripped.

23 23

Metal door weather stripped. 23 23

Solid core wood door, weather stripped

and with aluminum storm door fitted

with single glazed window. Both

sealed.

31 30

Acoustical doors. 43 42

* The data shown here were compiled from several sources and represent the

average performance for the construction described.

88
Table 26. Average A-welghted Sound Transmission Loss of Domestic Roofs*

Description A-Weighted Transmission Loss

Composite transportation

noise

Traffic

noise

Domestic roof: pitched wood frame

sealed perimeter but without

insulation or ceiling.

9 9

Domestic roofing: pitched wood frame

insulation between roof joints; sealed

perimeter but without ceiling.

23 20

Domestic roofing: pitched wood frame

perimeter sealed; plaster ceiling

but without insulation.

24 23

Domestic roofing: pitched wood frame

insulation between roof joints; sealed

perimeter; plaster ceiling.

34 31

Flat Domestic Roof: steel deck; plaster

celling but without insulation.

25 23

Flat domestic roof: steel deck; plaster

ceiling and 2 - 3 in insulation.

32 30

* The data shown here were averaged from several mostly foreign sources as data for construction typical of U.S. practice are scarce.

89
Sound transmission loss values are measured in decibels or dB units. The

decibel or dB unit is the term used to identify 10 times the common logarithm

of the ratio of two like quantities proportional to power or energy (Ref. 43).*

The important part of the definition of the dB unit is that the quantities are proportional to power or energy. The sound transmission loss is defined in dB

units using the ratio of the sound power on the noise source side of the con- struction to the power transmitted through the construction to the receiver

side.

Sound power, like all forms of power, cannot be directly measured.

However, sound power can be mathematically related to sound pressure and sound

pressure can be directly measured using a microphone. The mathematical

relationship between sound pressure and sound power depends upon both the

noise source and the propagation characteristics of the sound field. These

relationships are different for outdoor noise incident upon the building

envelope and for sound fields within rooms. For either situation, however, a sound power to sound pressure relationship may be formulated, and the sound

pressure (as measured by a microphone) can be expressed as a sound pressure

level in dB units.

Since both the sound transmission loss and the sound pressure level are defined in terms of sound power, they are both measured in dB units and may be

related mathematically . In this manner, the sound pressure level on the noise

source side, the sound pressure level on the receiver side of the construction, and the sound transmission loss are related. Under laboratory conditions,

a test specimen of building construction is built into a common wall between

two special chambers or rooms. This type of facility is of special construction

such that noise in the source chamber can only transmit through the specimen to

the receiving chamber. Since both the source chamber and the receiving chamber

are designed to possess well-defined acoustic characteristics, the mathematical

relationship between sound power and sound pressure is also well-defined for

these conditions. In this manner, laboratory measurement of the sound transmission loss based upon sound pressure level data is conducted using standard

test methods (Refs. 38 and 39).

For the same building construction used as part of the building envelope,

the noise exposure conditions for the construction are more complex than the

laboratory conditions. However, using the same approach of mathematically

relating sound power and sound pressure on either side of the construction, the

sound pressure levels on either side of the construction and the sound transmission loss are also related. Since the noise exposure conditions are more complex for field conditions, other physical aspects of the problem must be

incorporated into the sound power-sound pressure relationship (Ref. 20).

Unfortunately, it is very difficult to mathematically incorporate all of these

physical aspects, the result being a higher degree of uncertainty of the

A logarithm is a mathematical operation on a number and it is not

necessary to know how to use logarithms in order to use these guidelines.

90
sound power-sound pressure relationship as compared to the laboratory conditions.

This uncertainty affects both the prediction and the measurement of sound

transmission loss in the built environment.

It is now appropriate to discuss the other main physical aspects of relating

noise insulation characteristics of the construction to the noise isolation

characteristics of the building envelope.

Composite Envelope Construction

The building envelope is usually of mixed or composite construction such

as masonry or frame walls containing windows and doors. Each component of the

composite construction (masonry wall, frame wall, window, or door) exhibits

different sound transmission loss characteristics. The question that now arises

is how to estimate the sound transmission loss of the composite construction

knowing the sound transmission loss characteristics of the components. To do

this we also need to know the percentage distribution of the surface areas of

each component. Rather than introducing the mathematics at this point, an example will be used to illustrate this physical aspect of the problem.

Consider a wall with a total area of 100 ft^ composed of 90 ft^ of masonry

wall and 10 ft^ of glass windowpane. This construction is 90-percent masonry

wall and 10-percent glass window. Now consider a wall built of the same materials but using 50 ft^ of masonry wall and 50 ft^ of glass windowpane.

Since the masonry wall has a higher value of sound transmission loss than the

glass window pane (see Tables 20 through 26), the construction with 90-percent

masonry wall would be expected to exhibit a higher sound transmission loss than

the construction composed of 50-percent masonry wall. The method of estimating

the composite sound transmission loss will now be explained using the definition

of sound transmission loss.

Since the sound transmission loss is defined in terms of the ratio of the

outside or incident sound power to the transmitted sound power, we must determine

this ratio. Further, since the composite wall has components of different areas,

it is necessary to estimate the average outside sound power per unit area over the

total wall area. (For the above example, this average value is Wq/IOO where Wq

is the total sound power on the outside.)"^ For the composite wall with 10-percent

glass, the outside sound power for the masonry construction is 90Wo/l00 and for

the glass is IOWq/ 100. For the composite wall with 50 percent glass, the

outside sound power for the masonry construction is 50Wq/ 100 and for the glass

it is also 50Wq/100.

The mathematics are Included in appendix C.

Sound power per unit area has the dimensions of acoustic Intensity,

watts/m2 and since intensity also incorporates the direction of sound

propagation this approach is essential for defining outdoor-to-indoor sound

transmission loss (Ref. 20).

91
For the masonry wall construction, suppose that the transmitted sound

power per unit incident sound power is Wtm and for the glass is W-pG where

the subscript T denotes transmitted sound power. (The numbers and W-pg are determined from the sound transmission loss of the masonry construction and

the glass, respectively.) For the wall with 10-percent glass, the total

transmitted sound power, denoted by (W^o^Tj the sum of the transmitted sound

power values for the two components and is

:

(Wio)t ~ (90Wo/100)W-pi4 + ( 10Wo/100)W<pG

and for the wall with 50-percent glass is given by:

(W5q)t “ (50Wo/100)W-pM + (50Wo/100)W-pG

•

The composite sound transmission loss is then determined by dividing each of

the above values by the total outside sound power, Wq, and doing some arithmetic

using logarithms. What is important, however, is the ratio (Wjq)p/Wq and

(W5o)t/Wo*

For example we have:

(W]^o)t/^o ” ( 90/ 100) Wp'}^ + (10/100)WpG

(W5q)t/Wo = (50/100)Wp{kj + (50/100)WpQ.

Since Wpj^ is a number less than WpG (the masonry transmits less sound power

than the glass), then we see that (Wj^Q)p is a number less than (W5 Q)p. That

is, the wall with 10-percent glass transmits less sound power than the wall

with 50-percent glass. This completes the example. The user should appreciate

that the above procedure can be extended to any number of components of the

composite wall.

So far, we have defined sound transmission loss and have indicated how

this definition may be applied to estimating the sound transmission loss of a composite construction. We now consider how the details of the outdoor sound

field may also be incorporated into the definition of sound transmission loss.

Outdoor Sound Field

The characterization of the outdoor sound field is an extremely difficult

task. The many details that should be considered are the noise source characteristics, the noise propagation to the building envelope, source-receiver

geometry, and time-varying sound levels. Due to the difficulty of incorporating

all of these interrelated details, simplified models are used to develop designoriented results (Ref. 20). These results indicate that the many variables

may be incorporated (in an elementary fashion) as a single adjustment term for

the incident outdoor sound power. This sort of adjustment may be called an "angle of incidence" adjustment. Although this terminology implies that

92
source-receiver geometry is the main consideration, the adjustment also includes

noise source characteristics, noise propagation, and time-varying characteristics.

For a flat surface exposed to noise representative of highway, railway, and

aircraft sources, an "angle of incidence" adjustment of -2 to -3.5 dB to the

sound transmission loss appears appropriate for a wide range of angles (Ref.

20). (The angle of the incidence is measured normal to the plane of the building

surface.

)

For building surfaces that contain balconies or other projections, other

adjustments must be applied. These adjustments are described later in these

guidelines, and are based upon laboratory acoustic scale model measurements

since the problem is too difficult to analyze mathematically.

We now turn to the consideration of the indoor sound field within the room

and relate this physical aspect to the estimation of the noise isolation of the

building envelope.

Indoor Sound Field

The outdoor sound power and the sound transmission loss of the exterior

wall allow one to estimate only the average sound power transmitted at the

inside surface of the wall. It now is required to determine how this transmitted sound power or acoustic energy is converted into the sound pressure

field within the room. This is the topic of "room acoustics" where we are concerned with estimating an average indoor sound level that characterizes any

point within the room volume.

First, the transmitted sound power or energy is partly dissipated and

partly converted into acoustic pressure within the room volume. The energy

dissipation results from the sound waves striking either the room boundaries

and, if the room is furnished, the room contents. Carpets, sofas, draperies,

people, and even sheetrock walls and ceilings all absorb a percentage of the

sound (energy) striking their surfaces. As the sound waves propagate about the room (striking surfaces with part of the energy absorbed and part of the energy

reflected), an indoor sound field is created. The occupant’s ear is located in

this sound field, and, if a microphone is placed within the sound field, a sound pressure level is measured. This sound pressure level is proportional

only to the energy of the indoor sound field.

The total energy entering the room via the exterior wall equals the energy

absorbed by the room contents and the energy of the sound field within the room. Since we are Interested only with the indoor sound level, we must know the

sound transmission loss characteristics of the exterior wall to determine the

total energy entering the room and the total sound energy absorbed by the room

contents. Then, the energy of the sound field is just the difference between

the total energy and the absorbed energy.

In summary, the indoor sound field, as characterized by the indoor sound

level, depends upon both the sound transmission loss of the exterior walls and

the sound absorption characteristics of the room contents.

93
Sound Absorption of the Room

The total sound absorption of the room incorporates the effect of all the

interior surface finishes and the room contents. For materials that are purchased or installed on the basis of area (such as sheetrock, carpet, or acoustical tiles), the sound absorption characteristics of the material are usually provided in terras of the sound absorption coefficient. In general,

the sound absorption coefficient represents the fraction of the sound

power absorbed by the material and is determined by laboratory measurement

(Ref. 44). The sound absorption coefficient for any material varies with

frequency, the manner in which the material is attached to the wall, ceiling, or floor, and also with the disposition of the material within the room. The total sound absorption provided by the material is the product of the

absorption coefficient and the total area of the material. It also varies

with frequency. The unit of total sound absorption is called the "sabin"

(after a famous acoustical engineer) and the physical dimension for total

sound absorption is area (ft^ or ra^).

A physical object, such as a sofa, also absorbs sound. However, it is

impossible to assign a definite surface area to the object. In this case, the

total sound absorption may also be measured in the laboratory and is used to

define the sound absorbing characteristics of the object. The total absorption

of the object is measured in physical units of area and varies with frequency.

Representative values for the total sound absorption of typical room contents

are available (Ref. 44).

Since we are interested in knowing the sound absorption in terras of Aweighted frequency characteristics, the frequency dependence of the total sound

absorption of the room must be considered. Fortunately, however, we can avoid

complicated calculations. The above discussion on sound absorption was simply

a method for establishing the basis for this approximation. The key to the

physical understanding of this approximation is that the total sound absorption

is expressed in units of area (ft^ or ra^).

After many measurements and calculations for several different combinations of room surface finishes and typical room contents, acoustical engineers

realized that the total sound absorption of a room is often proportional to

the floor area of the room and essentially frequency independent (Refs. 40,41

and 42) . The average value of this constant of proportionality appears to be

80-percent of the floor area of the room (Ref. 42).

Putting It All Together

Now, we can put all of the physics together to relate the building

envelope noise isolation to site conditions, the noise insulation properties

of the envelope construction, and the indoor conditions. The steps are as follows

:

94
( 1 ) Calculate the composite noise insulation of the building

construction using the noise insulation properties

and the surface areas of the components. The noise

insulation properties may be estimated using the

data contained in Tables 20 through 26 or as described in

appendix C.

(2) Adjust the composite noise insulation for the total

sound absorption of the room adjacent to the exterior

walls and/or roof.

(3) Adjust the composite noise insulation for angle of

incidence of the outside sound field.

Actually, it is convenient to combine steps (1) and (2) above so that the

required information is then a description of the building construction and the

ratio of the area of each envelope component to the floor area of the room. (This is a result of approximating the total room absorption as a constant

times the floor area.) The adjustment for angle of incidence may be obtained

using the detailed procedure of Ref. 20 or simply as a constant ranging from

-2.0 to -3.5 dB as judged best for the site conditions.

The main consideration is the estimate of the composite noise Insulation

of the building components. An example will illustrate the step-by-step

calculation method.

Estimation of the Envelope Noise Isolation

We now present the method for estimating the A-welghted noise Isolation of

the building envelope. First, a room or rooms with exterior walls are selected

for analysis. Usually, a bedroom will be selected for residential construction,

since sleep is a very noise-sensitive activity. Next, the outside walls of the room are designated, for the purpose of these guidelines, as "envelope members."

An "envelope member" is characterized by two attributes: 1) it separates a room from the outside, and 2) the outdoor noise level is essentially uniform over

the surface area of the member. For residential construction, the dimensions

of the exterior walls of a room relative to the distance between the wall area

and the source location are such that the second attribute is satisfied. Each

envelope member, however, may be exposed to a different level of outdoor noise.

As described below, the consideration of different levels of exterior noise on the envelope members is only a refinement needed for corner rooms exposed to

highway traffic noise. Depending upon the room location within the building,

it may be necessary to consider from one to five envelope members in order to

estimate the noise isolation.

Each envelope member may comprise several individual components such as

the basic wall construction, the windows, and doors. Each component is

characterized by its A-weighted sound transmission loss value and its total

surface area. Figure 19 illustrates two envelope members that are "acoustically

95
a) Envelope members: 3 windows with area

Si each and TLi, one door with area S2

and TL2, wall with area S3 and TL3

b) Envelope members: 2 windows of area 2 Si

and Si and TLi each, one door with area

S2 and TL2, wall with area S3 and TL3

Figure 19, Acoustically Identical Envelope Members (S denotes surface area

and XL denotes sound transmission loss)

96
equivalent" since the component sound transmission loss values are identical

and the total surface areas of the components are identical. The room sound

absorption is characterized by the floor area of the room.

To estimate the composite noise isolation of the envelope member comprising

two or more components, the following information is necessary:

- The A-weighted sound transmission loss of each component

(see Tables 20 through 26 or appendix C).

- The total surface area of each component.

The total floor area of the room.

The calculation is conducted utilizing a worksheet format similar to that

described for the noise prediction models. A few examples will illustrate the use of the worksheets.

EXAMPLE 6. An exterior wall comprising the basic wall structure and some windows

has the following characteristics:

Wall: area = 90 ft2 TL = 34 dB*

Windows: area = 30 ft^ TL = 22 dB*

The room dimensions are as follows: height, 8 ft; width, 15 ft; length 20 ft.

First, the values for the sound transmission loss must be adjusted for the

component areas relative to the floor area of the room. Figure 20 illustrates

a completed copy of Worksheet V indicating the necessary calculations. A

blank copy of this worksheet is provided in Section 3.3 along with necessary

lookup table. As indicated in Figure 20, one simply inserts the appropriate

data and follows the step-by-step directions. The result is an adjusted value

of the sound transmission loss for each component of the envelope member.

The user should note that the TL values must correspond to the noise

source type as Indicated in the worksheet and that the worksheet allows up to

five components to be used in the next step of the calculation.

Figure 21 illustrates the next step utilizing worksheet VI. The adjusted

TL values from Figure 20 are entered at the heading of Figure 21 as indicated. The step-by-step instructions are followed to obtain the composite

TL of the envelope member. A blank copy of Worksheet VI is provided in

Section 3.3. together with the necessary lookup table.

These are A-weighted values. See Tables 20 through 26 for values

representative of typical construction.

97
WORKSHEET V CALCULATION OF ADJUSTED TL VALUES FOR ENVELOPE MEMBER ELEMENT

Envelope member description; EXAMPLE 6 , Window-Wall Combination

Noise source

;

Highway Traffic Room dimensions

:

Height 8 ; Width 15 ft; Length 20 ft

Total member area: 120 ft^ Room floor area, Sf<^: 300 ft2

Envelop member

element

description

Element

area, S^

ft2

Si/Sfji

Element TL* Adjustment ,Ag

from

Table 29

Adjusted Element TL

TL+Ag

1 . Wall 90 0.30 34 + 5.0 = 39

2 . Window 30 0.10 22 + 10.0 = 32

3. +

_

4. +

_

5 . + =

* See Tables 20 through 26 for representative values.

Figure 20. Completed Worksheet for Calculating Adjusted TL Values of

Elements: Example 6

98
WORKSHEET

VI.

CALCULATION

OF

COMPOSITE

TL

OF

ENVELOPE

MEMBER

99

Completed

Worksheet

for

Calculating

Composite

TL

of

Envelope

Member:

Example
As indicated in Figure 21, the composite TL of the example envelope member is

31 dBA.

Another example will illustrate a slightly more complicated problem.

EXAMPLE 7. We now estimate the effect of an open window upon the com- posite TL value. To do this, we use the same data as in the previous example.

However, in this case the "window" is considered as two components: a "closed

area" and an "open area." Assume that the windows are double hung so that,

when they are open, 50% of the total glazed area is covered and 50% is open.

We further assume that the covered portion of the window exhibits the TL value

of the closed window and that the open portion transmits all of the energy

incident upon its area directly into the room.* That is, the A-weighted sound

transmission loss of the open portion is assumed to be 0 dB.

«l Figures 22 and 23 are the completed worksheets for this example. In Figures;

23, it is seen that the composite A-weighted sound transmission loss for the

windows fully open is 13 dBA as compared with 31 dBA for the windows closed.

Admittedly, this is a dramatic example. However, the purpose is to emphasize

the importance of keeping the envelope sealed to preserve the noise isolation _ performance. | Worksheets V and VI allow one to estimate the composite sound transmission

loss of an envelope member comprising up to five components. It now remains to

combine the sound transmission loss values of each envelope member to estimate

the noise isolation of the room. To do this, we must now consider the outdoor

sound levels over each envelope member, and possibly an angle of incidence

correction.

Figure 24 and 25 illustrates building locations relative to the types of

noise sources considered in these guidelines. For highway and railway noise

sources, it is assumed that the building is generally rectangular in plan shape

and that the envelope surfaces are either parallel (front and rear surfaces) or perpendicular (side surfaces) to the highway alignment. As indicated in Figure

24, adjustments to the outdoor DNL are listed for each of the building surfaces.

The outdoor DNL adjustments are expressed in terms of dB relative to the outdoor

DNL for the clear site at the location of the envelope member . (A corner room will have a member on the front envelope surface and a member on the side

envelope surface.) The angle of incidence adjustments are listed in Figure 25

and are based upon the results of Ref. 20.

Unless the dimension of the side surface is equal to or greater than the

setback distance, D, as indicated in Figure 25a, it is not necessary to estimate;

the outdoor DNL at each surface. A single estimate for the geometric center of )

We assume the covered portion of the window to exhibit the same TL ; value as the closed window since the "double pane" configuration will result i in gaps and cracks around its perimeter. Whatever value of TL one desires

to assume does not alter the final answer since the open area is so large.

100
WORKSHEET V. CALCULATION OF ADJUSTED TL VALUES FOR ENVELOPE MEMBER ELEMENT

Envelope member description: EXAMPLE 6 » Wall-Open Window Combination

Noise source: Highway Traffic Room dimensions: Height 8_; Width ft; Length 2£ ft

Total member area: 120 ft-^ Room floor area, 300 ft"^

Envelop member Element Element TL* Adjustment ,Ag Adjusted Element TL

element

description

area, S-s ft2

Si/Sfji from

Table 29

TL+Ag

1. Wall 90 0.30 34 + 5.0 = 39

2. Window (Covered) 15 0.05 22 + 13.0 35

3, Window (Open) 15 0.05 0 + 13.0 _

13

14. +

—

5. +

* See Tables 20 through 26 for representative values.

Figure 22. Completed Worksheet for Calculating Adjusted TL Values of

Elements: Example 7
WORKSHEET

VI.

CALCULATION

OF

COMPOSITE

TL

OF

ENVELOPE

MEMBER

102

Figure

23.

Completed

Worksheet

for

Calculating

Composite

TL

of

Envelope

Member:

Example
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103

Figure

24,

Noise

Source

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104
the building is sufficient to characterize the outdoor noise. However, the DNL

adjustments listed in Figure 2A must still be used. For highway noise, with

the highway at ground elevation, it is usually not necessary to consider the

roof surface for rooms located on the top floor of the building. Also, if the

set-back distance, D, is greater than 50 ft and the total building height is

less than 4 stories (50 ft or less), then the angle of incidence correction for

the front surface is constant at -2 dB.

Figure 25b illustrates the aircraft-building relationship. In this case,

the outdoor DNL and angle of incidence adjustments depend upon the average

lateral distance, D2 , between the building location and the ground track (see

Figure 10) and the aircraft altitude, h. If the relative location of the

aircraft is such that it appears close to the horizon to an observer at the

building location, then the angle of incidence adjustments used for highway

noise apply.* If the aircraft location is such that it appears high above the

horizon or overhead, a -3.5 dB angle of incidence adjustment should be used.

In either case, no adjustment to the outdoor DNL for shielding of aircraft

noise by the building is used.

Two examples will now be presented to illustrate the steps required to

estimate the indoor sound level in buildings. In the first example, the building site is exposed to both highway noise and aircraft noise. For the second

example, the building is exposed to noise from two intersecting highways. The

examples are constructed to illustrate the method for calculating the envelope

noise isolation for differing source-receiver locations. Since it would be

impossible to cover all conditions that may arise, the examples are discussed

to emphasize the calculation procedures.

EXAMPLE 8. A multi-unit three-story apartment building is to be located

at a site exposed to noise from one highway and noise from aircraft operations.

Using the method of Section 2, the highway traffic noise exposure is estimated

to be L(jn = 63 dB, and the estimate of the aircraft noise exposure is

Ldn = 65 dB. The combined outdoor DNL is obtained using Table 16 and found

to be Ljji = 67 dB. From Table 3, it is seen that the site is marginally

acceptable based upon the outdoor noise criterion of L^j^ “ 55 dB and, to

achieve the indoor criterion of L(jn “ ^5 dB, windows must be assumed to be

closed, and the building envelope noise level reduction should be 25 dB.

Figure 26 illustrates the proposed building location relative to the highway

along with the highway DNL values at the front and rear surfaces of the building.

The average DNL value of 63 dB for the highway noise will be used for this

example. These DNL values are for the clear site without the building present . We now estimate the envelope noise level reduction.

This does not imply that aircraft noise and highway noise are similar

in this case. The adjustment for aircraft noise is based upon time averaging for a single flyover. The adjustment for highway noise is based solely

upon geometry. However, the magnitudes of the adjustments are approximately

the same for the aircraft relative location as described.

105
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106

Figure

26.

Building

Location

for

Example

Problem

Illustrating

Calculation

of

Building

Envelope

Noise

Isolation
The first step is to identify the envelope members for each typical room in

the apartment unit. The ground floor and first floor rooms will have only one exterior wall if they are located in the building center, and two exterior walls

if they are corner rooms. The top floor units will also have the roof as an envelope member. For the present example, we shall concentrate on the top floor

corner rooms, since these room represent the more complicated source-receiver

geometry. Two conditions then arise: a front corner room with a wall facing

the highway and a rear corner room with a wall facing away from the highway.

The next step is to estimate the composite TL for each envelope member for

each room. Assume, for this example, that the exterior walls on the front and

rear of the building are identical for each room (similar apartment units) and

comprise windows, a wall, etc. We shall call these walls the entrance walls to

distinguish them from the side walls. Also, assume that the side walls are identical for each room, but different from the entrance walls (perhaps the

window area varies). Whatever the details, the envelope member TL values are obtained using Worksheets V and VI based upon the architectural features

and the specific construction.

For this example, the following envelope member TL values are given for

windows closed as:

Envelope Member Composite TL

Room and Noise Source Entrance Side Roof

Front highway noise . 31 34 —

Front aircraft noise 34 37 30

Rear highway noise 31 34 —

Rear aircraft noise 34 37 30

At this point, it must be emphasized that the above values are A-weighted

transmission loss values and not noise isolation values.

It is now necessary to estimate the envelope noise isolation. Since the

envelope member noise isolation and even the important envelope members to

Include* both depend upon the noise source, the envelope noise isolation must

be estimated separately for each source and then the combined performance

determined. Once again, a worksheet format is utilized to perform the

calculations. Worksheet VII is used to calculate the adjusted TL for each

envelope member. The adjustments incorporated in using Worksheet VII are angle

of incidence of the outdoor noise and the room sound absorption adjustment.

The roof may be excluded for highway traffic noise if the highway Is

located at the ground floor elevation of the building.

107
(Once these adjustments have been incorporated, the envelope TL value is,

strictly speaking, transformed into a noise isolation type of value. That is,

the term "adjusted TL" used in Worksheet VII is more properly called a noise

isolation value. However, before the complete noise isolation value can be

determined, we must incorporate a third adjustment for the exposure of the

envelope member to the noise source).

Worksheet VIII is used to adjust the outdoor noise level at the envelope

member and to compute the indoor noise level contribution due to noise propagating through the envelope member. Both the outdoor noise level at the

envelope member and the adjusted TL values from Worksheet VII are entered in

Worksheet VIII.

Figure 27 illustrates the steps required to calculate the adjusted TL

values for the envelope members exposed to highway traffic noise. The composite

TL values Indicated in Figure 27 are the values listed above for this example.

Figure 28 is the corresponding calculation for the aircraft noise. In both

cases, the room absorption has been assumed to be "average" and the -1 dB

adjustment used. For the angle of incidence adjustment, the values indicated

in Figure 25a are used for highway noise, and the -3.5 dB average for aircraft

noise is assumed, for this example, as suggested in Figure 26b.

The next step is to complete Worksheet VIII. The necessary information is

the outdoor DNL, and adjustment for the envelope member exposure to the noise

source, and the adjusted envelope member TL values from the Worksheet VII.

Figure 29 illustrates the completed worksheet for the highway traffic noise,

and Figure 30 illustrates the complete worksheet for the aircraft noise. The

adjustments for the envelope member noise source exposure are from Figure 24

and are now discussed.

For highway traffic noise, the building will block or screen a portion of

the roadway from an observer location behind the building. Similarly, a building

surface will be exposed to only one portion of the highway-generated noise once

the building is constructed. The "exposure adjustment" incorporates this

consideration into the analysis, and constitutes a separate consideration from

the angle of incidence adjustment. The use of the member TL values requires

the incident sound power on the envelope members. For an envelope member

exposed to only a portion of the highway, the outdoor DNL value must be adjusted

to account for this partial noise exposure to estimate the indoor DNL contribution. For the building front, parallel to the highway, the adjustment is 0 dB

since this surface is exposed to all of the acoustic energy generated by the

highway. For the building sides, perpendicular to the highway, the adjustment

is -3 dB since the building shields the side surface from half the incident

energy generated by the highway. For the rear surface of the building, the

adjustment is -15 dB due to the building shielding the entire roadway. These

adjustments apply to the building orientation as indicated in Figures 25 and

26, an infinitely long highway as used for the noise prediction method of

Section 2, and ignore reflections from other buildings. (See Example 4.)

We are now in a position to estimate the outdoor-to-lndoor noise isolation

due to the highway noise, the aircraft noise, and the total noise environment.

108
WORKSHEET

VII.

CALCULATION

OF

ADJUSTED

TL

VALUES

FOR

EACH

ENVELOPE

MEMBER

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Figure

27.

Completed

Worksheet

for

Calculating

Adjusted

TL

Values

for

Each

Envelope

Member:

Example

8,

Highway

Noise
WORKSHEET

VII.

CALCULATION

OF

ADJUSTED

TL

VALUES

FOR

EACH

ENVLOPE

MEMBER

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110

Figure

28,

Completed

Worksheet

for

Calculating

Adjusted

TL

Values

for

Each

Envelope

Member:

Example

8,

Aircraft

Noise
WORKSHEET

VIII.

CALCULATION

OF

INDOOR

SOUND

LEVEL

CONTRIBUTION

FROM

EACH

ENVEI.OPE

MEMBER

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29.

Completed

Worksheet

for

Calculating

Indoor

Sound

Level

Contribution

from

Fach

Envelope

Member:

Example

8,

Highway

Traffic

Noise
WORKSHEET

VIII.

CALCULATION

OF

INDOOR

SOUND

LEVEL

CONTRIBUTION

FROM

EACH

ENVELOPE

MEMBER I

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112

Figure

30.

Completed

Worksheet

for

Calculating

Indoor

Sound

Level

Contribution

for

Each

Envelope

Member;

Example

8,

Aircraft

Noise
The numbers in the right-hand column of Figures 29 and 30 represent the indoor

DNL contribution due to each noise source-envelope member combination. It only

remains to combine these levels to determine the total indoor level. To do this,

we use Table 16 and the results in Figures 29 ad 30 as follows;

Front corner room/highway: Combine 35 and 29 to obtain 36 dBA indoor DNL

Rear corner room/highway: Combine 29 and 18 to obtain 29 dBA indoor DNL

Front corner room top f loor/aircraf t ; Combine 35.5, 32.5, and 39.5 to

obtain 42 dBA indoor DNL

Rear corner room top floor/aircraft : Combine 35.5, 32.5, and 39,5 to

obtain 42 dBA indoor DNL

Front corner room top floor/highway and aircraft: Combine 36 and 42 to

obtain 43 dBA indoor DNL

Rear corner room top floor/highway and aircraft: Combine 29 and 42 to

obtain 42 dBA indoor DNL

From the combination of the indoor DNL contributions, it is seen that the

total indoor DNL is estimated to be 42 to 43 dBA and would be considered, therefore, acceptable using the criterion indicated in Table 3. This estimate may

be expected to vary by ^ 3 dB due to the assumed room sound absorption (see

note to Worksheet VII), It is obvious that aircraft noise dominates the indoor

environment, in this example.

Before completing the example, we estimate the building envelope noise

isolation expressed in terms of the outdoor-to-indoor DNL difference. For the

combined highway and aircraft environment, the outdoor DNL is 67 dB and the

indoor DNL is 43 dB for the front corner room on the top floor. The envelope

noise isolation for this case is 67 - 43 = 24 dB. For the same room considering

highway traffic noise only, the noise isolation is 63 - 36 = 27 dB and, for

aircraft noise only, the noise isolation is 65 - 42 = 23 dB, For the rear

corner room, the noise isolation is 25 dB for the combined highway and aircraft

noise only. Hence, when the noise isolation of the building envelope is

specified, it is necessary to incorporate all considerations of the source and

the room location relative to the source if the noise isolation value is to

have meaning . The reader may also appreciate that by considering a few typical

combinations of envelope members and noise sources, the analysis may be used to

evaluate an entire development utilizing similar construction without completely

repeating the calculations for each and every room of every building.

EXAMPLE 9, We now consider a building site exposed to noise from two

intersectng highways. The site geometry and the noise levels of each highway

are illustrated in Figure 31. To simplify the presentation of the example,

assume that the building dimensions relative to the setback distances from each

highway allow one to consider the clear site sound levels to be essentially

uniform over the building surfaces. Further, assume that the composite TL of

113
114

Figure

31.

Building

Location

Relative

to

Two

Intersecting

Highways:

KXAMPLF

9
all building surfaces is constant at 22 dB for highway traffic noise.* This

example will emphasize the significance of the various adjustments when estimating the envelope noise isolation. The four corner rooms are used, with each

room exhibiting a different exposure level from the noise sources.

The calculations are performed for each room using Worksheets VII and VIII

for each combination of envelope member and highway. Worksheet VII is used to

obtain the adjusted TL values of each envelope member and highway. Worksheet

VIII is used to adjust the outdoor levels for each envelope member and highway.

Table 27 summarizes the calculations, and illustrates the relative significance

of each of the adjustment terms. For each room, the combined indoor DNL is

also indicated. It is seen that although each envelope member has the same A-welghted noise insulation value (TL = 22 dB) , each of the four rooms is

estimated to exhibit a different A-weighted noise isolation value. Since the

total outdoor noise level is 64 dB, the A-weighted noise isolation values for

each room are:

Room 1

:

64 - 47 = 17 dBA

Room 2: 64 - 46 = 18 dBA

Room 3: 64 - 44 = 20 dBA

Room 4: 64 - 42 = 22 dBA

These noise isolation values are relative to the clear site condition.

The above examples were presented to illustrate the steps required to

determine the building envelope noise isolation. Table 28 provides a summary

of the worksheets utilized to conduct this step-by-step calculation procedure

with a brief description of the purpose of each worksheet. Tables 29 and 30 are presented in Section 3.3 together with worksheets VII and VIII for ease of

reference.

Degradation of Noise Isolation Performance

The calculation of the envelope noise isolation requires the use of Aweighted values of the sound transmission loss for each component of an envelope

member. The description of components listed in Tables 20 through 26 contain

the words "sealed" and "unsealed" to denote that possible gaps and cracks may

exist in the construction. These gaps or cracks result in degradation of the

sound transmission loss performance of the construction since the noise will

propagate through the gaps with very little loss of acoustic energy. The

* This is done to simplify the example. In practice, it is necessary to base

the envelope member TL upon its construction details and never use an average value for the entire envelope.

115
Table

27.

SUMMARY

TABULATION

OP

CALCULATIONS

FOR

EXAMPLE

PROBLEM

NUMBER

9

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116
Table

28.

Summary

of

Steps

for

Calculating

the

Building

Envelope

Noise

Level

Reduction

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117
details of the physics describing noise propagation through gaps and cracks is

extremely complicated and beyond the scope of these guidelines. However, it

is important to recognize the degree of degradation that may result if gaps or cracks exist in an otherwise adequate design. Reviewing the data presented in

Tables 20 through 26, it is seen that differences of 3 to 5 dB between sealed

and unsealed conditions are possible. Due to the complexities of the problem,

the degradation associated with any specific gap or crack geometry must be

determined by laboratory testing (Ref, 45), However, approximations to the

theory do provide an indication of the degradation.

As a guide to estimating the degradation of the sound transmission loss

due to gaps and cracks. Table 31 was prepared based on data presented in

Ref, 41, The gap or crack, characterized in Table 31, are based upon air

leakage tests and are expressed in terms of "air openings" in units of in2 of

opening/ 100 ft^ of the envelope member. As seen in Table 31, if only 1/10

of 1 percent (12 in^ of opening/100 ft^) of the envelope member area is

open, the TL value of the member may be drastically reduced. Below Table 31,

a range of "air opening" values is indicated for several different types of

construction with the range corresponding to "good workmanship" or "average

workmanship." This range of values is suggested by Ref, 41 and should be

suitable for prediction purposes.

Table 31 should be used for guidance only. Detailed calculations should

be based upon laboratory data such as provided by Tables 20 through 26 . That

is, if an estimate of the effect of using sealed rather than unsealed windows

is desired, use should be made of the corresponding data in Table 22.

Table 31 is provided for general guidance only in that it indicates the

importance of "sealing" the structure, especially if higher TL values are important to the design. It should be noted that for a given opening, the

degradation is less important for the lower values of the envelope member sound

transmission loss. What this means in practice is that well designed construction will perform poorly if the inplace construction results in a "leaky"

structure. Further, a "leaky" structure may be realized if less than one percent of its surface area is open. To achieve noise Isolation in practice,

quality control during construction is an absolute necessity .

Open Window Conditions

The previous sections have dealt with procedures for estimating the envelope

noise isolation under various conditions. Example 7 included the details of

estimating the envelope member sound transmission loss for an open window. In

that example, it was determined that the sound transmission loss changed 31 dRA

for the closed condition to 13 dBA for the open condition. This change represents

an 18 dBA degradation of the sound transmission loss for closed or sealed

construction. As a rule of thumb, an envelope noise isolation value in the

range of 10 to 15 dBA for open windows representing 10 to 20 percent of the

total wall area may be used irrespective of the noise isolation value of the

construction with the windows closed (Refs, 2, 14, and 46).

118
Table 31. Change In the envelope Member TL Due to Cracks and Gaps in the

Construction (summarized from Ref. 41)

Envelope

member

TL

Design value

Air Leakage Openings in^/100 ft^

<0.5 0.75 1.5 3.0 4.5 6.0 7.5 9.0 12.0

50 to 55 r -10 -12 -15 -17 -18 -19 -20 -21

45 to 50 -3 - 5 - 8 -10 -12 -13 -14 -15 -16

40 to 45 -2 - 3 - 4 - 6 - 8 - 9 -10 -10 -11

35 to 40 -1 - 1 - 2 - 3 - 4 - 5 - 5 - 6 - 7

30 to 35 0 0 - 1 - 1 - 2 - 2 - 3 - 3 - 4

25 to 30 0 0 0 0 - 1 - 1 - 1 - 1 - 1

Good* monolithic

walls with operable windows

and non-weatherstripped

Average* —I f construction — Good* —I (walls with

Average* —J \ fixed windows

I Good* — J

L Average*

(

I— Good*

(

walls with operable

windows and weather

- stripping

L Average*

* Indicates range of air leakage corresponding to either good

workmanship or average workmanship.

119
Since closing windows impiles a requirement for either mechanical ventilation

or air conditioning during warmer months, noise isolation requirements become

directly related to both energy consumption and building operating costs.

These considerations become significant for areas of the United States where

climatic conditions do not require extended periods of heating or closed

window conditions during the year.

The question then arises as to the time average of the envelope noise

isolation if the envelope is assumed to be closed during part of the year and

open during the remainder of the year. It must be remembered that the noise

predictions used to estimate the outdoor DNL are annual averages. To be

consistent, it is necessary to use an annual average value for the envelope

noise isolation to estimate the annual average indoor DNL. Table 32 has been

prepared to provide guidance for estimating an annual average value of the

envelope noise isolation.

As an example, suppose that local climatic conditions indicate the following

average number of days per year to provide indoor heating or cooling:

average days for heating = 180

average days for cooling = 65

average days heating/ cooling not required = 120

For these conditions, it would be assumed that windows could be open 120 days

per year and still achieve an adequate indoor themal environment. Hence, the

windows could be open 33 percent of the time during the year based upon thermal

conmfort. The question now is: How does this affect the average noise isolation

of the building envelope?

From Table 32 under the column heading of "windows open 30 percent of the

time," it is seen that the average annual noise isolation would be 14 to 18 dB.

If the building were designed to achieve a noise isolation of 30 dB with windows

closed, the occupants would realize only an annual average value of 18 dB noise

isolation if they opened their windows during periods when neither heating or cooling is required for thermal comfort.

Tables 31 and 32 convey the same basic message: to achieve the design

noise isolation, gaps and cracks must be sealed and windows must remain closed

on essentially an annual basis . If an economic penalty is to be assigned to

requiring windows closed, the penalty is the cost of mechanical ventilation

(not necessarily air conditioning) during the time period for which windows

could be open to achieve indoor thermal comfort.

Screen Balconies and Courtyards

The open-window conditions described in the previous section apply to

conventional windows that occupy from 10 to 20 percent of the area of an

120
Table 32. Average values of Building Envelope Noise Isolation for Combined

Open/Closed Window Conditions

Closed

Windows

Noise

Percentage of time windows are open Open

Windows

Noise

Isolation,

dB 10 20 30 40 50 60 70 80 90

Isolation,*

dB

15 15 15 14 14 14 14 14 13 13 13

20 19 17 17 16 15 15 14 14 13 13

25 21 19 18 17 16 15 14 14 13 13

30 22 20 18 17 16 15 15 14 13 13

35 23 20 18 17 16 15 15 14 14 13

40 23 20 18 17 16 15 15 14 14 13

45 23 20 18 .17 16 15 15 14 14 13

* The open window noise isolation is assumed to be 13 dBA.

121
envelope member. Often, it is desired to provide sliding glass doors opening

on to a balcony or courtyard as a design feature of the building. When closed,

single pane sliding glass doors may exhibit an 18 to 23 dBA value of sound

transmission loss (see Table 22). When open, however, the noise isolation of

the envelope member is very low due to the large open area typical of sliding

glass doors.

In order to provide some degree of noise isolation with either windows or sliding glass doors open, the use of screens or partially enclosed balconies

has been recommended (Refs. 32-35), These referenced studies provide designoriented methods for estimating the indoor noise level for a screened balcony

or courtyard. These methods are based upon acoustic scale model studies and

require detailed source-receiver geometric data to estimate the noise isolation

achieved. Further, the noise measures used to develop these empirical results

are not consistent with the Ldn measure used in the present guidelines.

However, the reader should be aware of these techniques which may be

applied to specific building design features. As an approximation, a 3 to 6 dB

outdoor-to-indoor noise isolation may be attributed to using screened balconies

or courtyards with windows open in the absence of a more detailed acoustical

analysis of the specific conditions.

3.3 INDOOR NOISE MITIGATION WORKSHEETS

This section provides an overview of the calculation procedure, and the

necessary worksheets and look up tables for estimating the building envelope

noise isolation. This information is assembled within this section for ease

of future use. If the user desires, the examples presented in Section 3.2 may

be reviewed. However, each worksheet indicates the necessary step-by-step

calculation procedure and, as required, the appropriate lookup table.

Use of Worksheets

The calculation procedure utilizes four worksheets to estimate the

envelope noise isolation for each noise source . As used in these guidelines,

a noise source is each highway, each railway track, and each aircraft flight

path. For highway noise, each highway may comprise several lanes; but, for

intersecting highways, the worksheets must be completed for each highway with

the final indoor sound level obtained by combining the indoor sound level

attributable to each source (see Example 9, Figure 31, and Table 27).

The four worksheets are distinct steps in the calculation procedure.

Figure 32 illustrates these steps and indicates the purpose of each worksheet.

Table 28, which was presented in the previous subsection, summarized the purpose

of each worksheet and the result of the calculations of each worksheet. It is

important to note that the heading "Noise Source: ” appears at the

top of each worksheet. The purpose of this heading is to emphasize that each

noise source must be considered Individually when estimating the envelope noise

isolation

.

122
6. Calculate noise isolation: outdoor DNL - indoor DNL

5. Use Table 16 to combine indoor DNL values for each envelope

member to obtain total indoor DNL value

3. Use Worksheet VII to adjust envelope member TL values for

angle of incidence and room sound absorption

1. Use Worksheet V to obtain

the adjusted component TL

values of the envelope member

adjusted component TL values of

the envelope member

For each noise source

Figure 32. Purpose of Worksheets for Calculating Building Envelope

Noise Isolation

123
The numbering of the worksheets is consecutive with the numbering of the

noise prediction worksheets described in Section 2 of the present guidelines .

Worksheet V ; The purpose of this worksheet is to obtain an "adjusted TL" value

for each element or component of each envelope member (see Figure 32.) The

"adjustment" accounts for the element surface area relative to the floor area

of the room. The data required for this worksheet are the element surface

areas, the room floor area (or room dimensions), and the element A-weighted TL

values. The element A-weighted TL values may be obtained from Tables 20 through

26 or as described in the Appendix C. The adjustment is determined from Table 29,

These TL values depend upon the noise source. The results are entered in

Worksheet VI

.

Worksheet VI ; The purpose of this worksheet is to combine the element TL values

to estimate the A-weighted TL values of the envelope member. The data input to

this worksheet are the adjusted TL values from Worksheet V, These values are entered across the top of the worksheet along with the element description.

The adjusted element TL values are combined in sequence until all elements

have been combined. The method for combining values is indicated in the worksheet with the adjustment obtained from Table 30. Figures 21 and 23 illustrate

completed examples of this worksheet. The final combined TL value is the

A-weighted TL value of the envelope member. This worksheet must be completed

for each envelope member and noise soruce. The values obtained for the envelope

members surrounding a room are entered on Worksheet VII.

Worksheet VII ; The purpose of Worksheet VII is to adjust the TL values for

each envelope member for angle of incidence correction and room sound absorption.

The angle of incidence correction is obtained from Figure 25 and depends upon

both the noise source and the orientation of the noise source relative to the

envelope member. The room sound absorption adjustment is estimated as indicated

at the bottom of the worksheet. The same adjustment is applied to each envelope

member enclosing the room. The -1.0 dB adjustment for an "average" furnished

room correponds to the assumption that the total room sound absorption is

numerically equal to 80 percent of the room floor area (see Section 3.2). The

adjusted TL values are entered in Worksheet VIII,

Worksheet VIII . The purpose of Worksheet VIII is to estimate the indoor DNL

value attributable to outdoor noise transmitted through each envelope member.

The input data are the total outdoor DNL value, an adjustment to the DNL for

envelope member noise exposure (Figure 24), and the adjusted TL values for the

envelope members from Worksheet VII, The result of the calculation is the

indoor DNL value for the outdoor noise incident upon the envelope member for

the noise source under consideration. To obtain the total indoor DNL value,

the individual contributions are combined using the calculation procedure

indicated in Table 16.

124
Several Noise Sources

If the building envelope is exposed to noise from several sources, Worksheets V through VIII must be completed to obtain the total indoor DNL for

each source. These total source DNL values are then combined to obtain the

grand total indoor DNL values using Table 16.

The outdoor DNL is also composed of contributions from each noise source

with the total DNL combined using Table 16. Knowing both the outdoor and

indoor DNL for each noise source and the total outdoor and total indoor DNL,

one is now in a position to estimate the envelope noise isolation either for

each noise source, any combination of noise sources, or for the total noise

environment

.

Usually, one is interested only in the building envelope noise isolation

for the total noise environment. However, the consideration of the envelope

noise isolation on a source-by-source basis may be important especially when

evaluating alternative mitigation measures. For example, a highway noise

barrier may result in a lower indoor DNL when used in conjunction with the

envelope noise isolation for highway noise. However, if the site is also

exposed to aircraft noise, the highway noise barrier will provide no indoor DNL

change due to the aircraft noise. The worksheet format utilized in these

guidelines allows the user to evaluate these important considerations if

required. One has only to follow the step-by-step procedures for each noise

source and combine and compare the final results to evaluate the various

alternatives.

125
WORKSHEET V CALCULATION OF ADJUSTED TL VALUES FOR ENVELOPE

MEMBER ELEMENT

Envelope member description:

Noise source: Room dimensions: Height ^ft; Width ft;

Length ft

2 2 Total member area: ^ft Room floor area, Sf^: ft

Envelope member

element

Description

Element

area, Si Si/Sf£

ft2

Element TL* Adjustment ,Ag

from

Table 29

Adjusted

element TL

TL+A^

1 . +

2 .

3.

4. +

5. +

* See Tables 20 through 26 for representative values

126
Table 29. Values of the Adjustment Ag, dB, for Worksheet V

is the surface area of the member element

Sf£ is the floor area of the room

Si/Sfi*

PCT

^s

»

dB

Si/Sf£

PCT

^s»

dB

Si/ Sfjj,

PCT

^s

»

dB

.5 +23.0 4 +14.0 32 +5.0

.63 +22.0 5 + 13.0 ‘ 40 +4.0

.8 +21.0 6.3 +12.0 50 +3.0

1.0 +20.0 8 +11.0 63 +2.0

1.25 +19.0 10 +10.0 80 +1.0

1.6 + 18.0 12.5 + 9.0 100 0.0

2.0 +17.0 16 + 8.0 125 -1.0

2.5 +16.0 20 + 7.0 160 -2.0

3.2 + 15.0 25 + 6.0 200 -3.0

* These values are included to cover the range appropriate to open

windows and vents.

127
WORKSHEET

VI.

CALCULATION

OF

COMPOSITE

TL

OF

ENVELOPE

MEMBER

128

TL

difference:

TL^.^

~

TL5
Table 30. Values of the Adjustment A^, dB, for Worksheet VI

TL Difference TL Difference A^,

dB dB dB dB

-9.0 -0.5 + 1.0 - 3.5

-8.0 -0.6 + 2.0 - 4.1

-7.0 -0.8 + 3.0 - 4.8

-6.0 -1.0 + 4.0 - 5.5

-5.0 -1.2 + 5.0 - 6.2

-4.0 -1.5 + 6.0 - 7.0

-3.0 -1.8 + 7.0 - 7.8

-2.0 -2.1 + 8.0 - 8.6

-1.0 -2.5 + 9.0 - 9.5

0.0 -3.0 +10.0 -10.4

For TL Difference < - 9.0 A^ = 0

For TL Difference > +10.0 Ac = - TL Difference

129
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130
WORKSHEET

VIII.

CALCULATION

OF

ADJUSTED

TL

VALUES

FOR

EACH

ENVELOPE

MEMBER I O -H C Ui 3 4J CM <U O c o a

M

CO o o <u u c rH X M o (U B O i-H •H > 01 o (U 4J c e

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II II II II II

T3 <U

(U E (U

4-1 o x:

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U CO 3 CM

•»“) >-l -o O < 3 J • Z vO Q — U bd X J H tt< O Eh M o z z

T3

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II II II II II

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T3 E O 3

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a bo

B

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J o;

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oa Vi 2 Z C

CJ Vi

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131
4. NOISE COMPATIBLE DEVLOPMENT

4.1 ENVIRONMENT NOISE LEVELS COMPATIBLE WITH VARIOUS LAND USES

Planning with respect to environmental noise involves the separation of

noise sensitive land uses from exposure to high noise levels, and in cases where this is not possible, the develoraent of provisions for noise mitigation.

These measures are taken because of the adverse effects of noise on people.

The cumulative evidence from research indicates that exposure to day-night

average sound levels in excess of 75 dB over prolonged periods of time may

result in noise-induced hearing loss (Ref. 2). A number of investigations

combining social surveys and physical noise measurements have revealed that

people exposed to noise in their homes show a generalized adverse response

which increases with increasing noise exposure level. This generalized adverse

response is complex and involves a combination of factors including speech

interference, sleep interference and a frustrated desire for quiet and the

ability to use telephone, radio, and television satisfactorily (Refs, 2, 47,

48, 49, 51 and 52).

In the aggregate, the average adverse response of groups of people has

been found to be stable and related to the cumulative noise exposure as expressed

in a measure such as the DNL. Moreover, if the human response is stated in

terms of the percentage of people who express a high degree of annoyance due to

the activity interference produced by the noise, the relationship between noise

exposure and the adverse response is accurately described by the function shown

in Figure 33 (Refs. 48, 49 and 51).

Inspection of Figure 33 indicates that, for noise exposure at levels below

55 dB the percent of people highly annoyed by noise is insignificant, rising

very slowly from less than 1 percent to 4 percent over the range of 45 to 55 dB.

When the noise exposure level reaches 75 dB (the level where noise constitutes

a potential hearing hazard), the number of people highly annoyed rises to

about 40 percent. Above this exposure level, further Increases in the noise

exposure level give rise to sharp increases in the number of people highly

annoyed. Within the 55 to 75 dB range, the relationship between the number of

highly annoyed people and the exposure level can be approximated by a linear

relationship (Ref. 48). Data on the overt community reaction to noise reveal

that, on the average, the expected community reaction to an identifiable source

of intruding noise changes from none to vigorous when the DNL increases from

55 to 75 dB (Refs. 2 and 49),

As mentioned previously, noise-induced annoyance arises from the activity

interference produced by the noise exposure. Among the activities interferred

with, speech interference is the most often mentioned (Ref. 2). The extent to

which noise affects speech communication is dependent upon whether the speaker

and listener are located indoors or outdoors and the vocal effort of the speaker.

For many indoor situations, if the speaker and the listener are separated

by a distance greater than 3 ft (one meter), the speech level is more or less

constant throughout the room because the speech sounds are reflected from the

walls and other room boundaries. In such cases, for a normal voice communication

132
PERCENT

PEOPLE

HIGHLY

ANNOYED

DAY-NIGHT AVERAGE SOUND LEVEL (dB)

Figure 33. Summary of the Effects of Community Noise on People as a of Day-Night Average Sound Level.

Function

133

SOUND

LEVEL

WEIGHTED

FUNCTION

FOR

IMPACT
level, a 100 percent sentence intelligibility is achieved if the indoor noise

level is at or below 45 dB. The sentence intelligibility drops to 90 percent

if the noise level raises to 65 dB and to 50 percent at 72 dB (Ref. 2).

Outdoors, the speech level at the receiver drops with increasing distance

between the speaker and the listener because of the lack of reverberance

resulting from the absence of reflecting walls. Thus, outdoors, the interference produced by noise depends upon the distance between the speaker and

the listener. The noise levels for a 95 percent sentence intelligibility

outdoors as a function of the distance between the speaker and the listener

are shown in Table 33 for both normal and raised voice.

The major effects of noise on people for various levels of noise exposure

are also summarized in Table 33. This table shows that, if the outdoor noise

exposure level is below 55 dB, no serious adverse effects are likely to result,

whereas, at 75 dB or above, serious effects occur, including a potential hearing

damage. Based upon these findings, environmental noise levels compatible with

various land uses are derived. These relationships are shown in Table 34.

(Table 3 of section 1 of the report presents a specialized version of Table

34.) In assessing the data presented in Table 34, it is important to remember

that the levels shown are based only upon consideration of human response to

noise and do not include any considerations of either economics or feasibility.

Thus, when decisions are made about land use, other factors such as economics

and feasibility must be balanced against the levels shown in Table 34 as these

levels provide a basis only for evaluating community response to noise (Refs. 1,

2, 10 and 48).

4.2 TECHNIQUES FOR LAND USE CONTROL

As the history of airport noise litigation shows, serious noise impact

problems arise when either a noise source is introduced or modified in such

a way as to result in a noise impact or when the land use pattern around a noise source changes in such a way as to result in excessive noise exposure

levels for the new land uses, and its associated human activities (Refs. 61

and 62). In the latter case, the noise does not become a problem until the

land around the noise source shifts from one type of land use to another (e.g.,

from agricultural to residential use).

The objective of a noise control and mitigation program is to prevent or decrease the noise impact on the land adjacent to a major noise source. Typically, such a program would include provisions both for controlling the

noise at the source and or controlling land use patterns in the neighborhood

of the source. The present section is concerned with the tools available to

local authorities for the control of land use patterns. However, before these

tools are discussed, it is important to note that land use control is often

achieved at the local level where it is limited by two factors; 1) the existing

enabling legislation of the state whereby the police powers of the state are delegated to the local governments; and, 2) the level of sophistication of the

local government and the planning agency (Refs. 10 and 63). A summary of the

major tools available for land use control is given in Table 35.

134
Table 33. Effects of Noise on People

DNL

Outdoors, dB

Physilogical

effects

Maximum Distance

for percent

sentence

intelligibility

outdoors

ft (m)

Percent of

population highly

annoyed

Community

reaction

55 none 1.5 (3.5) 4 none

60 none 6.5 (2.0) 9 minimal

65 none 5.0 (1.5) 15 moderate

70 unlikely 3.0 (0.9) 25 signf leant

75 potential for

noise induced

hearing loss

1.5 (0.5) 37 severe

135
Table

34.

Environment

Noise

Levels

Compatible

with

Various

Land

Uses

136
Table 35. Techniques for Local of Land Use Control

Regulatory Controls

Zoning

:

oto require exclusion of

noncompatible land use

»^to require path discontinuity

»to require outdoor-toindoor noise isolation

Subdivision regulations:

®to require noise re- duction in site design

Building codes:

•to require noise

isolation in new

construction and/or

in rehabilitation

Health codes:

•to define noise as health hazard

•to require noise

isolation in con- struction

Disclosure of noise

levels:

•to inform purchaser

of renter of noise

problem

Public Acquisition

Municipal land

acquisition:

•to create buffer zones

•to prevent incompatible

land use

•to maintain present land use

•to develop compatible

land uses for resale

•to hold for future:

- land banking

Partial municipal

land acquisition:

•easement to allow

limited land uses

Financial Incentives

Tax incentives:

•to prevent incompatible land use development

•to provide increased

noise control

Capital improvements:

•restrict munici-'

pal developments

to quiet areas

137
Regulatory Controls of Land Use .

Zoning is one of the most powerful tools used to direct land use in

accordance with a comprehensive master plan for the orderly growth of a whole

community. It is the means by which many factors of concern are controlled

including health, safety, pollution, density, lot size, building height, ratio

of open space to developed land, and others. The zoning ordinance usually

consists of a text and a map (or a series of maps). The text gives the substance

of the standards applicable to each zoning district, and the procedure governing

proposals for change of either the text or the map. The map allows residents

and other interested parties to identify where various districts are, and what

section of the ordinance applies to a given land area. Since the regulations

governing each zoning district differ from each other, there exists a potential

for preferential treatment of some districts. Accordingly, states often take

special care to limit the local legislative power so as to insure fair and

reasonable treatment for all.

While the preparation and administration of zoning ordinances vary from

municipality to municipality, usually several bodies are involved, each with

its own responsibilities. For example, a zoning commission may be responsible

for preparing the original zoning ordinance; a board of appeals may be charged

with granting variances in hardship cases and may hear appeals in cases involving

disputes over the interpretation of the ordinance; the local legislature may

enact amendments to either the text or the map in accordance with the

recommendations it may receiver from a planning commission which itself may

need to proceed only after holding public hearings on the matter under

consideration (Ref. 64).

Traditionally, enforcement of zoning provisions are accomplished through

the granting of approval to proceed with a proposed project prior to its

construction. However, since some problems may not be anticipated until after

the fact, many municipalities are now issuing occupancy permits. In the case

of noise, this enforcement procedure is particularly useful since noise isolation

of the building envelope cannot be measured until the building is completed.

To control noise at a site, zoning may be used in several ways. Land within a noise Impacted area can be zoned for noise compatible uses such as commercial, industrial, or agricultural. However, this technique works

successfully only if the community has a noncumulative type of zoning law which

prohibits, for example, residences from being built in industrial zones. Under

cumulative zoning, zones are ranked in some low to high use sequence such as heavy industrial, light industrial, commercial, multi-family residential, and

single family residential. Any use permitted in a high use zone, such as single

family residential zone, is also allowed in lower use zones such as commercial,

light industrial or heavy Industrial; however, the reverse is not true (Ref. 63).

The exclusion of certain land uses in noise impacted areas must be done

with caution since overexclusion can result in certain areas being underutilized,

with the attendant loss of revenues. In addition, overexclusion can interfere

with the orderly development of surrounding districts, and/or the region as a whole.

138
Zoning regulations may require specific site design details or construction practices in designated areas where the noise levels exceed a specific

DNL. These noise provisions may involve the construction of noise barriers,

for example along a highway adjacent to a residential area, or specification

of additional noise attenuation provisions beyond those specified in a building

code.

While zoning is one of the most often used tool in land use control, its

effectiveness is limited by the facts that: 1) it is not permanent, so the

current legislative body is not bound by prior zoning actions which can be

changed; 2) it is not retroactive so it may not be possible to prohibit a particular land use in noise impacted areas if the use already exists on the

land; and, 3) it applies to the land within the boundaries of a particular

jurisdiction; however, noise problems often span more than one jurisdiction,

each with its own regulations. This is why in addition to zoning local

authorities will often rely on more than one control technque.

The severity of the noise impact on the building occupants can be controlled

to some extent through the local building codes. Unlike zoning ordinances, the

building codes do not restrict land use but rather insure that specified criteria

and conditions inside buildings are met. The key to the effectiveness of a building code is the issuance of occupancy permits since these can be made

contingent upon the builder meeting well-defined criteria upon completion of

the project. If the zoning ordinance and the building code are well coordinated

so that, for example, the zoning ordinance specifies the areas where particular

sections of the building code requirements must be met, the effectiveness of

both can be greatly enhanced.

Most of the acoustical provisions contained in building codes are presented

in the form of fixed acoustical performance requiremens as, for example, in the

Appendix of the Uniform Building Code (Ref. 65). These requirements may be

expressed in terms of: 1) specific construction techniques such as doubleglazed windows or double-studded walls; 2) in terms of mandatory noise attenuation characteristics, such as a specified sound transmission class*; or 3) in

terms of a defined sound level in a type of space, such as the maximum A-weighted

sound level in a bedroom at night (Ref, 13).

Recently, a Model Noise Control Code (Ref, 13) was developed under the

sponsorship of the U.S. Environmental Protection Agency which, in contrast to

present practices, specifies variable performance requirements for residential

and educational buildings based upon the prevailing day-night average sound

level, DNL, on a site. The outdoor-to-indoor noise isolation requirements of

this proposed code are shown in Table 36. The techniques for predicting and

implementing the sound attenuation through the building envelope were given in

Section 3 of the present guidelines.

The Sound Transmission Class, or STC rating, is a single number rating us. for partitions separating indoors rooms. The STC rating should never be

used to rate the outdoor-to-indoor noise isolation of building construction.

139
Table 36. Outdoor-to- Indoor Noise Isolation Requirements Contained in the

EPA Model Noise Control Code Specification (Ref. 13)

Outdoor day-night

average sound level,

in dB

Outdoor-to-indoor

A-weighted level

difference, dB

50 - 55 none

55 - 60 none

60 - 65 20

65 - 70 25

70 - 75 30

75 - 80 35

> 80 construction prohibited

140
Subdivision control ordinances represent another type of regulatory action

that can be effectively used in land use planning. It is very closely related

to zoning. However, while zoning usually applies to individual lots, subdivision

regulations apply to larger units. Subdivision ordinances can be effectively

used to create buffer zones between noise sources and noise sensitive areas.

In communities that neither have nor wish to use zoning or subdivision

control laws, an alternatie may be to include noise as a health hazard in

health codes. If the noise provisions of the health codes are quantitatively

expressed, the developer may have to include noise control measures to obtain

an occupancy permit for buildings located in noise-impacted lands. An alternative approach for controlling noise through land use control may consist of

requiring that local real estate agents inform prospective buyers of all noise

impacted areas or, that noise contours be drawn on a deed or on municipal

maps, subdivision plats, or zoning and land use maps. In and of itself, disclosure of noise exposure levels will not prevent inappropriate land use, but

through disclosure the forces of the market place may keep noise-impacted

areas from being inappropriately developed (Ref. 68).

Non-Regulatory Controls

The most effective way to prevent incompatible land use development in the

vicinity of major noise sources is the direct acquisition of the land surrounding the noise source. Once the land has been acquired, the community may

keep the land as it is, develop it for noise compatible uses, or sell it with

restrictions on the deed to insure that only compatible uses will be developed

by the new owner.

An alternative approach may be restrictive easement. An easement is a right held by one person to make use for compensation of the land of another

for a limited purpose. Thus, an easement does not involve a change in ownership, but, rather, the right for noise to intrude on a tract of land for price

and the impositions of restrictions on the land use options available to the owner. Unlike zoning, once an easement has been obtained it is final.

Moreover, since noise easements do not involve an outright acquisition of

land, the easements usually can be obtained at a fraction of the total value

of the land. Since the tract does not change hands, the land remains part of

the community tax base. In fact, with compatible noise development, the tax

assessment may even increase relative to the value prior to the easement.

Accordingly, noise easements are usually considered to be less expensive than

full purchase alternatives.

In undeveloped areas, another approach to the control of noise through

land use can involve the purchasing of large tracts of undeveloped lands by the

local authorities prior to any development on that land. The land can then be

held in trust for future use in accordance with a comprehensive plan and with

local land policies. This technique, known as land banking, can be inexpensive

since the land is bought prior to its being needed; however, clearly it is

practical only in scarcely developed areas (Ref. 67).

141
Land use controls can be enhanced through financial incentives. These

can take many forms. If the area around a major noise source is used as agricultural land it may be taxed as such, rather than as future developable

land. This may create an incentive to keep the land as it is. Alternatively,

the owner might be given a tax credit if, and only if, the land is developed

into a noise-compatible use. Financial incentives designed to keep noise

impacted lands from incompatible development must be carefully implemented

since there can be debate over the fairness of applying preferential tax

assessment or credits to some lands and not to others. Further, lowering the

assessed value of property may mean a narrowing of the tax base. Another

financial approach may consist of selective extension of municipal services.

For example, water and sewer lines may be extended to quiet areas but not to

noise impacted lands since, in general, developers are likely to locate new developments where capital improvements are located as it saves them both time

and money.

142
5.

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143
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145
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in Buildings, ANSl/ASTM E336-77, American Society for Testing and

Materials, 1916 Race Street Philadelphia, PA 19103.

40. Mange, G. E., Skale, S. R. , and Sutherland, L. C., Background Report on Outdoor-Indoor Noise Reduction Calculation Procedures Employing the

Exterior Wall Noise Rating (EWNR) Method, U.S. Department of Transportation, Federal Highway Administration, Report FHWA-TS-7 7-220 , March 1978.

41. Pallett, D. S., Wehrli, R. , Kilmer, R. D., and Quindry, T. L., Design

Guide for Reducing Transportation Noise In and Around Buildings,

U.S. Department of Commerce, National Bureau of Standards, Report BBS 84,

April 1978.

42. Quirt, J. D., Acoustic Insulation Factor; A Rating for the Insulation

of Buildings Against Outdoor Noise; Building Research Note No. 148,

National Research Council of Canada, Division of Building Research,

Ottawa, Canada, June 1979.

43. Standard Definitions of Terms Relating to Environmental Acoustics;

ANSI/ASTM C634-792, American Society for Testing and Materials, 1916 Race

Street, Philadelphia, PA 19103.

44. Sabine, H. J. and Moulder, R. , Sound Absorptive Materials; Chapter 21 in

Handbook of Noise Control , C. M. Harris (Ed.), Second Edition, McGraw-Hill

Book Co. , 1979

.

45. Sabine, M. J., Lacher, M. B., Flynn, D. R. , and Quindry, T. L., Acoustical

and Thermal Performance of Exterior Walls, Doors and Windows U.S. Department

of Commerce, National Bureau of Standards, Report BSS-77, November, 1975.

46. Sutherland, L. C. , Indoor Noise Environments Due to Outdoor Noise Sources,

Noise Control Engineering, J^, (3), November-December 1978.

47. Von Gierke, H. E., Yaniv, S. L., Blackwood, L. B., Environmental Impact

Statements, Chapter 45 in Handbook of Noise Control , C. H. Harris (Ed.),

Second Edition, McGraw-Hill Book Co., 1979.

48. Guidelines for Preparing Environmental Impact Statement on Noise, Report

of Working Group 69 on Evaluation of Environmental Impact of Noise, Committee on Hearing, Bioacoustics and Biomechanics, National Academy of

Sciences, National Research Council, Washington, D.C., 1977.

49. Schultz, T. J., Community Noise Rating, Second Edition, Applied Science

Publishers, 1982.

50. Galloway, W. V., and Schultz, T. J., Interim Noise Assessment Guidelines,

U.S. Department of Housing and Urban Development, Office of Policy Deve-.

lopment and Research, Report HUD-CPD-586 (2), December 1980.

146
51. Schultz, T. J., S 3mthesis of Social Surveys on Noise Annoyance, J. Acoust.

Soc. Am., pp, 377-405, 1978.

52. Alexandre, A., Decision Criteria Based on Spatio-Temporal Comparisons of

Surveys on Aircraft Noise in Proceedings of the International Congress on Noise as a Public Health Problem, Dubrovnik, Yugoslavia, U.S. Environmental

Protection Agency, Office of Noise Abatement and Control, Report 550/9-73-008

pp. 619-626, 1973.

53. Stevens, K. N. , Rosenblith, W. A., and Bolt, R. H., A Community's Reaction

to Noise: Can it be Forecast?, Noise Control, J^, pp. 63-71, 1955.

54. Galloway, W. J., and Bishop, D. E., Noise Exposure Forecasts: Evolution,

Evaluation, Extensions and Land Use Interpretations, U.S. Department of

Transportation, Federal Aviation Administration, Report No. 70-9, 1970.

55. Airport - Land Use Compatibility Planning, Advisory Circular 150/5050-6,

U.S. Department of Transportation, Federal Aviation Administration,

December 1977.

56. Bishop, D. E. and Horonjeff, R. D., Noise Exposure Forecast Contours for

Aircraft Noise Tradeoff Studies at Three Major Airports, U.S. Department

of Transportation, Federal Aviation Administration, Report No. 70-7,

1980.

57. California Department of Aeronautics, Noise Standards, California Administrative Code, Register 70, No. 48, 28 Chapter 9, Title 4, November 1970.

58. Policy and Procedure Memorandum 90-2, U.S. Department of Transportation,

Federal Highway Administration, Volume 7, Chapter 7, Section 3, 1973,

(revised in 1976 as Federal Aid Highway Program Manual).

59. Noise Abatement and Control: Department Policy, Implementation Responsibilities and Standards, U.S. Department of Housing and Urban Development

Circular 1390.2, August 1971.

60. Guidelines for Noise Impact Analysis, U.S. Environmental Protection Agency

Office of Noise Abatement and Control, Report PB82-219205, April 1982.

61. Caudra, E. D., Aircraf t/Airport Noise and the Courts, Chapter 38 in Handbook

of Noise Control , C. M. Harris (Ed.), Second Edition, McGraw-Hill Book Co.,

1979.

62. Rosenthal, A. J., Noise and the Law, Chapter 37 in Handbook of Noise Control , C. M. Harris (Ed.), Second Edition, McGraw-Hill Book Co., 1979.

63. The Audible Lanscape: A Manual for Highway Noise and Land Use, U.S. Department of Transportation, Federal Highway Administration, Office of Research

and Development, November 1974, reprinted August 1976.

147
64. So, F. S., Stollman, I., Bari, F,, and Arnold, D. S., The Practice of

Local Government Planning, International City Management Association, 1979

65. Internal Conference of Building Officials, Uniform Building Code, Whittier

Ca. 1979, Appendix, Chapter 35, Sound Transmission Control,

66. Schultz, T. J., Miller, N. P., and Miller, R. L,, Interim Report Task 1:

Development of Noise Control Requirements for Model Building Code, Bolt,

Beranek and Newman Report 3547, prepared for the U.S. Environmental Protection Agency, 1977.

67. Strong, A., Land Banking; European Reality, American Prospect, Johns

Hopkin's University Press, 1979.

68. Taylor, S. M. , Breston, B. E., and Hall, F, L, The Effect of Road Traffic

Noise on House Prices, J. of Sound and Vibration, (4), pp. .523-541 , 1982.

148
Appendix A. NOISE PREDICTION MODELS

This appendix presents the details of the noise prediction models described

in Section 2 of the main text. Using these results, the tabulated values

presented in the various lookup tables may be calculated directly.

A.l Highway Traffic Noise Prediction Model

The basis for the highway traffic noise prediction model is the formulation

presented in Appendix J of Ref. 6 . The site geometry is illustrated in

Figure 34. The highway pavement comprises several adjacent lanes and is con- sidered to be acoustically hard. The land between the near pavement edge and

the receiver is flat and free of obstructions. This land area may be either

acoustically hard or soft.

Using the nomenclature of Ref. 6 and the distances illustrated in

Figure 34. the equivalent sound level at the receiver for the i^^ vehicle type

on the r^" lane is given by:

(Leq)ir “ (Lo)£ir "*

+ 10

+ 10

+ 10

+ 10

log ( ttN^j-Do/

ir)

log (Dq/Dj.)

log (Do/DiP^^l

log (Dir/Dr)*^2

log

1 (A-1)

where Nir is the number of vehicles of the i^^ type on the

rtti lane

Dq is the _reference distance for the vehicle emission

level (Lo>Eir

is the speed of the i^^ vehicle type on the r^^ lane

D^ = D

2 + distance between the r^'^ lane and the

receiver

(4>l, <J> 2 ) = 7

tcos (|)] d(|). 1 <Pl

For an acoustically hard pavement, aj = 0, and for a straight infinite-length

roadway, the above expression may be simplified to obtain

149
Pavement

is

acoustically

hard

\

o

150

Fissure

34

Pavement

~

Receiver

Geometry

for

Highway

Traffic

Noise

Prediction
(A-2)

(>-eq>lr " <‘-o)Elr + ‘0 'Nlr/Sir) + 10 1°« <«2/K)

“2 - 10 log (D

2

) + 10 log [P^ /(1+Pj.)^'^“2]

where Pj. = (W/D2

) (r-1/2)

K is a constant for maintaining consistent units among the

several variables.

For multi-lane traffic flows, the eqivalent sound level is simply the

summation of Equation (A-2) over all lanes and vehicle types on each lane.

The next simplification results from assuming that the traffic flow is uniformly

distributed over all lanes and, that the average cruise speed is constant for

all vehicles on all lanes. With these assumptions the expression for the

equivalent sound level of the traffic flow becomes: _ I 3 (L )Ei/10

Lgq = 10 log

I i (N^/N) 10 ° /S

- 10 log (D2

) + 10 log (uD^/K)

!

n a 1+a

j ^ I Pr^/(1 + Pr)

r=l

where N is the total vehicle count for

S is the average cruise speed

n is the number of traffic lanes

subscript i denotes vehicle type

subscipt r denotes lane.

This result represents the equivalent sound level for the time period during

which N vehicles pass by the receiver.

The expression for the day-night sound level is obtained by summing, on an energy basis, the expression given by Equation (A-3) for each hour of the day

and introducing a + 10 dB weighting for the nighttime period from 10 p.m. to

7 a.m. and dividing the summation by 24-hr. However, data for traffic flows

will not typically be available on an hourly basis. Therefore, it is assumed

that only the total count during the daytime and the nighttime are available .

+ 10 log (N)

(A-3)

the highway

151
Further, it is asumed that during an average day the traffic speed does not

vary, and remains constant for each hour.

With these assumptions, the expression for the day-night sound level at the

receiver location may be expressed as:

3 . L^n = 10 log

I

I (fdi ^ni^^i ’ lO^^o^Ei/ 10/?

j + 10 log (N)

- 10 log (D2

) + 10 log (ttD^/24K)

n a 1 + a + 10 log U I Pr ^/(1 + Pr) (A-4)

r=l

where N is the AADT of the traffic flow, vehicles/ 24-hr

S is the average 24-hr cruise speed

fdi = N^^/N, fraction of i'"!^ vehicle type in the traffic flow

during the day

fni ’ N^i /N, fraction of i*"!^ vehicle type in the traffic flow

during the night

Fi Nj^/N, fraction of the i^^ vehicle type in the 24-hr

traffic flow.

The relationships between the various vehicle count parameters are as follows: _ _ 3 _

Ndi • I Ni; N„1 = I

Nj.: Ni = Ndi + N„1 ; N - JNj.

day night i=l

where ^ is a summation over the 15-hr period from 7 a.m. to 10 p.m.

day

y is a summation over the 9-hr period from 10 a.m. to 7 a.m. night

In the above development, three vehicle types have been assumed. The speeddependent A-weighted noise emission levels for the vehicle types are obtained

from Ref. 6 as:

152
Automobiles

;

(Lo)ei = 5.5+38.1 log(S) dBA

Medium Trucks

;

(Lq)e2 = 23.4 + 33.9 log(S) dBA (A-4)

Heavy Trucks

;

(Lq)e3 ^2.6 + 24.6 log(S) dBA

where S is the cruise speed in mph .

Equation (A-4) may be used to calculate the day-night sound level.

However, the formulation is inconvenient for a simplified lookup table format.

Accordingly, the following approximation is used.

3 (L ) /lO 3 (L ) /lO

I <*di + 10 “ ” (l+9fnMAx) I fl 1° ° lA-5)

i-1 i=l

where fnMAX is the fraction of nighttime traffic flow corresponding

to the vehicle type with the highest sound level.

For example, if all vehicle types are present in the traffic flow, then

fnMAX * in3 since heavy trucks represent the vehicle type generating the highest

sound level. If medium trucks and automobiles are present in the traffic flow,

then fnMAX “ in2* only one vehicle type is present in the traffic flow,

the above result is exact.

We now define a reference distance, Dj-gf , for the highway system measured from

the near edge of the pavement and away from the highway. This reference location

I is used to define the value for the highway system. The day-night sound

I level at this location is denoted as (L^n^ref • expression is obtained by

! substituting D2 = Dj-gf and Equation (A-5) into Equation (A-3). This result is

j formally subtracted from Equation (A-3) to obtain the normalized expression for

I the day-night sound level for receiver locations D Dref* result may be

expressed as:

! Ldn (D) = (Ldn)ref + ^ (D) for D > D^ef (A-6)

where (Ldn)ref ” ^dn (^ref)» (A-3) with (A-5)

I A(D) is the distance attenuation function.

The expression for L^n (f>ref)

2

' ^dn (Dj-gf) = 10 log

j

5; Fi 10(Lo)ei/10/S

I (i=l

+ 10 log {(l+9fni^x) • N}

+ Argf

153

(A-7)
The first term in this expression is used to obtain the traffic flow reference

noise levels presented in Table 4, The second term in the expression is used

to obtain the adjustment presented in Table 5. The last term is the hard site/

soft site adjustment entered in step number 3 of the highway traffic noise

prediction worksheet.

The complete expression for A^gf is:

ref - ^

' r=l

ref

(A-8)

where the notation in the last term implies Pj. is evaluated at D = D^^gf a is the hard/soft site parameter for the land adjacent to the highway.

The value for the constant K depends upon the units used to measure distance,

traffic flow speed and time. For the present development, distance is expressed

in ft, speed in mph and time in hr; so, the value of K is 5280 ft/mph. For

metric units utilizing m, km/hr and hr, K = 1000 m/km/hr.

The distance attenuation function, A(D), is given by the expression:

A(D) = 10 log (Dref/D2)

+ 10 log (G(D2 )/G(Dj.gf)), (A-9)

where G(D) - I [P“/(1+Pj.)

r“l

Pr = (W/D)(r-l/2)

W is the lane width

r is the lane number (r=l denotes the near lane).

Equation (A-9) is used to obtain the distance adjustment values presented in

Table 6 for hard sites (a*0) and in Table 7 for soft sites (a*0.5).

The explicit numerical values given in Tables 4 through 9 were obtained using

the constants:

Dq = 50 ft

Dref = 50 ft

154
K = 5280 ft/mph

W = 12 ft

The numerical evaluation of any of the above expressions is straightforward.

The only required comment concerns the expression for Aj-gf given by Equation

(A-8). As seen in Equation (A-8), the second term depends upon both the site

condition (as characterized by a) and the number of traffic lanes. Numerically,

the difference between ot=0 and a=0.5 results in a 3 dB difference in the value of

Aref* The numerical result of incorporating the number of traffic lanes

represents a difference of less than 0.5 dB for either a=0 or a=0.5. Hence, the

^ref term is incorporated as a "site constant" based upon a=0 or a=0.5, and

the +0.5 dB variation corresponding to the number of traffic lanes is ignored.

A. 2 Railway Noise Prediction Model

The prediction of the day-night sound level resulting from railway operations

Incorporates two distinct types of events: warning horn noise and locomotive

pass-by noise. For either type of event, the following procedure is used:

® Define the equivalent sound level for a single event with the duration

of the noise corresponding to the 20 dB down points of the noise time

history.

® Calculate the day-night sound level by summing the contribution of each

single event equivalent sound level and by weighting the nighttime events

by + 10 dB.

Denoting the single event level by Lg^L, the expression for the day-night sound

level is:

Ldn = Lsel + 10 log (N/24) + 10 log (l+9fn) (A-10)

where Lg^L = Leq 10 log (Tq)

Lgq is the equivalent sound level for the single event of

duration Tq

N is the number of events per day

fn is the fraction of the daily events that occur between

10 p.m. and 7 a.m.

Equation (A-10) is the basic relationship used to predict the value of Ljn

railway-operations. Hence, we may concentrate upon obtaining the expressions for

Lsel warning horn noise and for pass-by noise. The reader may also note

that Equation (A-10) also applies to aircraft noise prediction where LggL

corresponds to an aircraft noise event (see Ref. 22).

155
Warning Horn Noise

For warning horn noise, the site geometry is illustarted in Figure 35. To

simplify the analysis, it is assumed that any two single warning horn noise

events may be combined into one event comprising the train pass-by with the

warning horn operating continuously between the two horn initiation points

indicated in Figure 35. This assumption is equivalent to assuming that, on an average day, an equal number of trains approach the warning point from either

direction.

For the purpose of developing a tabulation format for computing the noise

exposure, it is convenient to define a reference distance, Dj.gf, and a reference

speed for the train, S^-gf. Then, considering the warning horn to be a continuous

point source generating a maximum sound level L^om ^ distance D^gf, and,

assuming "hard site" noise propagation (i.e., geometrical spreading), the

expression for the single event level is:

^SEL = (LsEL)ref ^Lsel(L,D) (A-11)

where (LsEl)ref = L^orn log (L/KSj^ _

+ 10 log [H(0,ili.ef )/^ref

]

ALsel(L.D) = 10 log [(Dref/D) H(I,I)/H(0,Irgf )

]

H(x,y) = tan"l [(x+y)] - tan~l [(x-y)]

it * L/D jit * L/D j ^ref ~ ^^Dref •

Remembering that LggL defined by Equation (A-11) comprises two "actual"

events, we substitute Equation (A-11) into Equation (A-10) to obtain the

expression for the day-night sound level for warning horns. The result is

‘dn

= 1-hom + 1° )/24K] +

+ 10 log ISrgfN/S] + 10 log (l+9fn). (A-12)

By defining the values for the nine parameters (Li^om» D, S, N, f„, L, D^-gf,

and S^gf) numerical results are obtained. The numerical values in Table 12 were obtained using the last term of Equation (A-12). The numerical values in

Table 14 were obtained using the first three terms of Equation (A-12) with the

nume_rical values: L^iorn ~ dBA, D^-gf = 100 ft, Sj-ef = ^0 CK = 5280 ft/mph)

and L = 1/4 mi = 1320 ft. The numerical values in Table 15 were obtained

using the next-to-last term of Equation (A-12).

156
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w

m

Is

J= Q. -5; CO Q. £ ^ ^.9 C (0

*“ 5.5 E ® CO O

CQ ^ ^ C ^ ® CO ® O) ® O) >

CD

C

O ^ CO c ®> ^^ -sCO

ffi

® £ ^ CO

i-i» O)

ftS’ t O £ ^ ii

iso o o a — O) a .E

CO c ® « © ^ o . U- CO - II S o

O) .2 S

EgCO > ^ ®

<D

® £ g © ® © © i © -c £ — o - © O

•“ c

(j) o2 o D E -D

w ^ ® c

•Z o E ^ o © ^ ^ o c « ®M© © © g

O) «

.£

©

CO ^ ©

S-c o - o co“ ®© ^ — © © © £ o- ^ ©

60c

•Hc

id«3

Ss

CO

:»

CO ai

60c

T3

0)id OU

iJo

a; ocV

60e

•Hw

•oc

CO

t>^ Id dj

(Ve0s

Id

01>

•dH0)u

01 0^I01

CJ

Id3

c^ : m

ro

01

Id3

60

157

Noise

Exposure
The value of Lhom “ from the track centerline is an approximation. This level is selected to be 10 dB higher than the reference

diesel-electric locomotive noise level described below. Since the value is

directly proportional to the value of the values in Table 14 may be

corrected for variations in L^orn desired. For example, if local data indicate

that L^om values in Table 14 would all be

increased by 4 dB.

Diesel-Electric Pass-By Noise

The prediction of the pass-by noise day-night sound level for a diesel-electric

locomotive and a number of railway cars is more complicated than either the

prediction of highway traffic or Che warning horn noise exposures described

previously. The complication arises from the details of the noise emission

characteristics of the locomotive, the cars, and the train. Otherwise, the

prediction models are similar in that the following method is used:

1) Define the single event level for an average event in terms of a level

at a reference distance and a distance attenuation function; and,

2) Define the day-night sound level in terms of the single event level and

the day-night distribution of the noise events.

Figure 36 illustrates the train as a finite length line source moving at constant

speed along a straight railway track. The locomotive noise is assumed to be

characterized as a point noise source whose sound power output is independent

of Che train speed. The railway cars -generate noise that varies linearly with

the logarithm of the train speed and exhibits a dipole directivity with the

dipole axis perpendicular to the track alignment. The sound power distribution

of the cars is assumed to be constant along the length of the cars. These

noise emission characteristics are representative of diesel-electric locomotives

and railway rolling stock (Ref. 23).

Since we are concerned with the total energy at the receiver, we can calculate

the energy received from each locomotive and from the line source of railway

cars for an average train pass-by comprising N locomotives and n railway cars. With this approach, the total train length is denoted by I and is expressed as:

Z TM ^^loco ^^car (A— 13)

where ^-loco average length of a locomotive = 70 ft

X-car average length of a car = 70 ft.

The single event levels are obtained by integrating the time-dependent sound

level at the reference distance between the 20 dB down points measured from the

maximum pass-by level.

158
Train

speed

is

S

i

159

Figure

36.

Source-Receiver

Geometry

for

Diesel-Electric

Railway

Pass-by

Noise

Prediction.
Denoting the maximum locomotive pass-by level by Lj , referenced to the distance

Dref» bhe single event level for a locomotive pass-by is expressed as

(Lsel^ = Li + 10 log (Dref/3S) + 10 log [gjOx) + g2(3x)] (A-14)

where S is the pass-by speed

X = Dref/D ^^d 6Dfef/S is the duration of the event

gj(Z) = Z tan"l(Z); g 2 (Z) = Z^/Cl+Z^)

Denoting the maximum pass-by level of the railway cars by L2 , referenced to the

distance Dj.ef» the single event level for the line source of length I is obtained

by a double integration. The first integration is over the length of the line source for a fixed instant of time, and the second integration is over the time

interval between the 20 dB down points of the pass-by time history, (It should

be noted that by considering the cars to be distributed over the total train

length, the wheel noise of the locomotive is included in the analysis,)

Performing the details of the integration, the single event level for the

railway car pass-by is obtained as:

(Lsel)2 = L 2 + 10 log{i[gi((2i+3)x) - gi( 3x) ] / [gi( it) + g2(^)]} (A-15)

where H = i/2 Dref» 2(ii+3)Di;ef /S is the duration of the event.

Based upon the data of Ref, 23, the following noise emission characteristics

for Dref = 100 ft are introduced:

Locomotive: L^ = 91 dBA

1-cars 1^2 ~ 84,5 + 20 log (S/55); S, mph.

If there are N locomotives per train, the train length is then given by the

expression:

I = (N^i oco ^^cars^ ~ ^^loco ^^cars)

where n is the number of cars per locomotive.

Introducing the dimensionless train length:

^ (^loco '^^cars^/21^ ref

160
the expression for the total equivalent sound level at the receiver is obtained

by adding, on an energy basis, N times the contribution of a single locomotive.

Equation (A-14) and the contribution of the railway cars. Equation (A-15). The

resulting expression is substituted into Equation (A-10) to obtain the

relationship for predicting the day-night sound level.

In order to develop a format suitable for tabulation, the resulting expression

is normalized to the reference distance, Dj.gf. The result is the estimated

at the reference distance and a distance attenuation term. The detailed

expression is:

where = (Ltrain^ref ^^train^^^^

+ 10 log (l+9fn)

^^train^ref ~ CN D^-gf/S)

+ 10 log [G(l, s, n, N)]

^Ltrain “ 10 log [G(x, S, n, N)/G(l, S, n, N)]

G(x, S, n, N) = [gi(x) + g2<x)]/3

Jl(S/55c)^ [g^((2NZ+3)x) - g^(3x)]

Ldn ” (l'dn)ref ^^train (A-16)

[gl(Nil) + g2 (M)]

Ntrain 1-® total number of trains per day

fn is the fraction of trains operating at night

N is the average number of locomotives per train

n is the average number of cars per locomotive

S is the train speed in mph

c 10 (1*1 — 84.5)/20 and.

all other terms are as defined previously.

161
The numerical values in Table 10 were obtained using the above expression for

(^-train^ref • The adjustment in Table 11 were evaluated using the second term in

the above expression for (Ldn)ref values in Table 12 were obtained using

the last term. The values for the distance attenuation listed in Table 13 were

based upon the above expression for ^Ltrain*

In order to develop a similar model for soft site noise propagation, the

procedure must be evaluated numerically rather than using the simple lookup

table format possible for the hard site condition.

Combining Sound Levels

For a site exposed to railway noise generated by warning horns, diesel-electric

locomotives and by railway cars, during a single event it is necessary to

combine the two sound levels to deteinnine the total noise exposure. Similarly,

if a site is exposed to both highway and railway noise, it is necessary to

combine the two simultaneous noise events to determine the total noise exposure.

Indeed, if any two sound levels are simultaneously received, their combined

level may be obtained using the following expression;

^combined = 1-1 + 10 log [1 + 10-<'-r'-2>/'0l (A-17)

where and L2 are the two sound levels.

If Lj is always taken as the higher of the two sound levels. Equation (A-17)

may be easily tabulated since the second term will be between 0 and 3 dB. This

result is the basis for the procedure given in Table 16 for combining the sound

levels

.

162
Appendix B. OUTDOOR NOISE MITIGATION

This appendix presents the technical background necessary to document to

procedures used to obtain the barrier insertion loss values listed in Table 18.

It also contains an approximate method for determining the insertion loss values

for locations about buildings exposed to highway traffic noise.

B.l. Highway Traffic Noise Barriers

The insertion loss of a barrier depends upon the relative geometry of the noise

source location, the top edge of the barrier, and the receiver location. The

geometric nonclature for the barrier insertion loss prediction is illustrated

in Figures 37, 38, and 39. The methodology utilized is based upon the development presented in Appendix B of ref. 6. However, two important differences

are introduced for the purposes of the present guidelines. First, the present

results are developed for the special case of an infinite-length barrier parallel

to the highway. Second, the small angle approximation used in Ref. 6 to relate

the maximum path length difference of a point on the line source is replaced

by the exact expression. Except for these two differences the present

methodology is identical to that contained in the Ref. 6.

Clear Site Conditions

For the clear site in the absence of the barrier, the expression for the

equivalent sound level at the receiver for the i^^ vehicle type on the j

lane of the roadway is given by:

The result is identical to Equation (A-2).

Site Conditions with Barrier Installed

When a barrier is installed between the source and the receiver, the acoustic

energy at the location of the receiver is decreased if the receiver is within

the "shadow zone" of the barrier. The net attentuation provided by the barrier

is called the barrier insertion loss and is defined as the equivalent sound

level at the receiver location before the barrier is installed less the equivalent

sound level after the barrier is installed. Equation (B-1) represents the

"before" conditions.

2 — ttD N

(Leq)i = (Lo>Ei + 10 log ( o i ) + 10 log

K Dj.Si (B-1)

where Pj- = (W/Dr)(j - 1/2); = D 2 + Dij

K is a constant for maintaining consistent units

among the several variables.

163
WJV//

Source

Thin

screen

barrier

Receiver

4“t

hr

vJ/M/

a) Definition of source, barrier, and receiver heights

b) Definition of distances relating source, top of barrier, and

receiver

c) Definition of angles relating source, top of barrier, and

receiver

Figure 37, Geometric Nomenclature for Thin Screen Barrier: Section

Through Site Perpendicular to Highway and Containing

the Receiver Location.

16A
Point

on

the

line

source165

Figure

38.

Geometric

Nomenclature

Relating

Noise

Source

Location

to

the

Reference

Plane

Perpendicular

to

the

Highway

and

Containing

the

Receiver

Location

(See

Figure

37)
Element

of

line

source

166

Figure

39.

Geometric

Nomenclature

Relating

the

Location

of

an

Element

of

the

Line

Source

to

the

Receiver

Plane

(See

Figures

37

and

38)
Following the same argument as presented in Ref. 6 and assumptions used to

develop Equation (A-2) and (B-1), the equivalent sound level after the barrier

is installed is given by the expression:

2

.ttD N

(Leq)i = (Lo)ei + 10 log^C o i )^+ 10 log J J, I ^2

Aij/10

,dB (B-2)

K Dj. Si n j=l (1+Pi)

where defines the barrier noise attenuation for the i

vehicle type of the lane of the highway.

,-th

Barrier Insertion Loss

The expression for the barrier insertion loss for the i^l^ vehicle type on the

highway is obtained by subtracting Equation (B-2) from Equation (B-1). The

result is:

/ n p“2 ) ( ^ ) (IL)i = 10 log ) I j > - 10 log ) I 10

( ,dB (B-3)

(j=l (1+Pj) ^^^2 )

( j=l (1+Pj)

) This result asssumes that the vehicle distribution is uniform over all lanes

and that the travel speed is constant. The parameters that determine the value

of the barrier insertion loss are the geometric variables illustrated in Figures

37 through 39 and the site constant a. The only remaining problem is

establishing the functional form of j

.

Barrier Diffraction

The attenuation provided by the barrier is characterized by the Fresnel Number,

N, and is defined by the relationship:

N = 26/X = 2f5/c (B-4)

where X is the wave length of the sound wave

f is the frequency of the sound

c is the speed of sound

The parameter 5 is called the path length difference and is defined as:

S = + (A+B-C) (B-5)

where the + sign is used if the receiver is in the shadow zone and

the - sign is used if the receiver has a direct line of sight to

the noise source.

167
With this background, the function A^j is defined as:

“a /lO tt/2 -a /lO

10 = 2 j 10 d(j) (B-6)

IT O

where <|> is the angle illustrated in Figure 39 and the integration limits are established by the assumption that the highway and the barrier are both of

infinite length.

The only complication is that the integral in Equation (B-6) must be numerically

evaluated since A^j is a complicated function of the angle (j>.

The Attenuation Function Aj^j(c{))

Using the diffraction theory of Ref. 6, the attenuation function is given by

the relationships;

-Aii/10

10 = J

1 for

-d+0.6e)/2 2

10 tan /2tt | | for

-d-K).6e)/3 2

10 tanh /2irN;j^j for

-2(1+0. 15e)

. 10

for

Nij< -0.1916 -0.0635e

-0.191 6-0. 0635e<Nij_<0

(B-7)

0£Nij<5.03

Nij25«03

where Nij(<J)) = (2f /c)6ij (ij))

Again, following Ref. 6, the amount of numerical effort is vastly reduced by

assuming a frequency of 550 Hz rather than conducting the calculations for a specific source spectrum. With this approximation, the expression for the

Fresnel Number is:

Nij(4,) = 3.21 6ij((})) with distance measured in m

0.982 6j^j(({() with distance measured in ft.

Referring to Figure 38, it now remains to determine the functional relationship

between the site geometry as described in Figure 37 for the reference plane

and Figure 39 for an element of the line source located by the angular

coordinate (}>.

168
We now introduce the following notation;

6q - 6((t>-0) = +(Aq + Bo - Cq)

(B-8)

6((J>) “ +(A((J)) + B((J)) - C((})))

With the geometry as defined in Figures 37 through 39, the following functional

relationships are obtained:

A( ({)) = AqF( r , 4>)

B(<|)) = BoF(y2,«J>) (B-9)

C(<t>) - CoF(yi,<J))

where F(9,(J)) = (l+cos^e tan2(j>)”l/2

,

For small values of 9, F(9,tj>) = cos 9, and the relationships (B-8) and (B-9)

result in the approximation:

5(<{>) =

<5o cos (j).

In many practical barrier design problems this approximation connot be used,

and the more complicated functions obtained by substituting Equations (B-8)

and (B-9) into (B-7) and, by integrating according to Equation (B-6), are required. To simplify the notation, the subscripts i and j have been dropped

in Equations (B-8) and (B-9).

Barrier Attenuation Tables

In order to develop numerical values suitable for the present guidelines, an extensive tabulation of barrier insertion loss values was developed. Figure

40 is a self-explanatory example of one of these tabulations. The values in

Figure 40 may be compared to the value of 6.0 dB + 1.0 dB given in Table 18c)

for an 8 ft high barrier located 25 ft from the pavement. The distance D

given in Figure 40 is the distance from the near edge of the pavement to the

receiver.

B.2 Shielding Provided by Buildings

Figure 17 of the main text is a qualitative illustration of the noise shielding

provided by buildings. The topic of sheilding provided by "barriers” of the

form of buildings is complicated and perhaps still a research topic. However,

using the approach described by Wittner in Ref. 37, an approximate result may

be obtained. This approximation ignores sound diffraction completely and assumes that geometric or "ray" acoustics describes the physics of the problem.

From a practical standpoint, these assumptions mean that the building should

be high, wide and deep. The insertion loss values that are predicted can be

expected to be slightly higher than what one might measure under field

169
MAXIMUM BARRIER INSERTION LOSS, dB

BARRIER HEIGHT; 8.0 ft

DISTANCE FROM PAVEMENT TO BARRIER 25 ft

RECEIVER HEIGHT: 5.0 ft

HEAVY TRUCKS

D

ft 1 Number of

2 3

Traffic Lanes

4 6 8

50 6.3 6.4 6.4 6.5 6.6 6.6

75 5.5 5.5 5.6 5.6 5.7 5.7

100 5.3 5.3 5.3 . 5.3 5.4 5.4

150 5.1 5.1 5.1 5.1 5.2 5.2

200 5.1 5.1 5.1 5.1 5.1 5.1

250 5.0 5.0 5.0 5.1 5.1 5.1

300 5.0 5.0 5.0 5.0 5.1 5.1

350 5.0 5.0 5.0 5.0 5.0 5.0

400 5.0 5.0 5.0 5.0 5.0 5.0

450 5.0 5.0 5.0 5.0 5.0 5.0

500 5.0 5.0 5.0 5.0 5.0 5.0

750 5.0 5.0 5.0 5.0 5.0 5.0

1000 5.0 5.0 5.0 5.0 5.0 5.0

1500 5.0 5.0 5.0 5.0 5.0 5.0

Figure 40. Example of Barrier Insertion Loss Tabulation

170
conditions. To simplify the analysis, it is further assumed that no other

building is located near by and that no sound is reflected toward the receiver.

Figure A1 illustrates the site geometry for estimating the shielding provided

by buildings. In terras of the dimensionless coordinates (Cjil) illustrated in

Figure 41, the insertion loss is given by the expression:

IL(C,n) = - 10 log ('J'CC ,n)/TT) , dB for n >o and + a. (B-10)

The function 4(^,0) is given by the expression

^(C,n) = IT - [<})i(C,ri) + <{>2(5,0)] (B-11)

where <{)2(5,n) = tan“^(l+C)/n)]

<|)2(5,n) = tan~^ [(l-C)/o)]

C = x/a; n = [y-(D+b)]/a.

Since the highway is of infinite length, the y-axis is a center line of symmety

for the insertion loss value. It may be shown that the contour of IL = 3 dB is

a circle of radius a (half the building width) centered at (C,o) = (0,0).

Sirailarily for IL > 3 dB, the contours are elliptical in shape with the major

axis centered at n = 0 (i.e., the rear face of the building). The expression

for a contour of constant insertion loss is given by the equation:

n = -k + /k^ + 1 - (B-12)

where k = 1/tan B

3 = TT • 10~IL/10 for IL >_ 3 dB.

By setting ? = 0 in Equation (B-12), one obtains an estimate of the distance

away from the rear surface of the building to the contour of constant insertion

loss. Further, Equation (B-12) may be integrated to obtain the area enclosed

between the contour insertion loss and the rear surface of the building. The

resulting expression for the area is:

A = a2 [3 -sln3 cosBj/sin^B (B-13)

where 3 = * 10“!^/ 10 for IL 3 dB.

The above results may be useful in estimating the maximum values of insertion

loss provided by buildings.

For rows of buildings and the inclusion of reflections, the user should consult

the following paper: Yeow, K.W. , Popplewell, N. , and Mackay, J.F.W., Shielding

of noise from statistically stationary traffic flows by simple obstacles,

Journal of Sound and Vibration, Vol. 57 No. 2, 22 March 1978.

171
Infinite length highway

y

1

•

Building

I

I

I ^Receiver location'll

I between limits I

a) Geometric nomenclature

Eqn (B-12)

b) Nomenclature for contours of constant Insertion loss

Figure 41. Nomenclature for Insertion Loss Estimate Provided by Buildings

172
Appendix C. A-WEIGHTED NOISE ISOLATION OF BUILDINGS

This appendix describes the details of the calculations required to estimate

the A-weighted sound transmission loss values described in Section 3.2 of the

main report, and the noise isolation of building envelopes.

C. 1 Normalized Noise Spectra

The first step in estimating the A-weighted sound transmission loss is the

determination of the normalized noise spectrum characterizing the outdoor noise.

Two normalized spectra are described in this appendix: a highway traffic noise

spectrum and a "composite” spectrum. The method used to normalize the data,

however, may be applied to any other spectrum shape desired.

The noise spectrum is defined by a set of values for the band center frequencies,

fj., and the corresponding band pressure levels, Lj-. It is assumed that the data

comprise a total of N values: {fr»^r} r=l,...,N. The spectrum is then

defined between the band center frequency limits f^ and ffj»

The band center frequencies, fj-, are related to the index r by the expression:

fj. = • 10^, Hz (C-1)

where c = 1 for octave band data

c = 1/3 for one third-octave band data

q = 1 + [3 - log (fp)]/c log (2).

It is assumed that the spectrum may be approximated as a continuous function

of frequency as:

L(f) = La + AL (f), dB (C-2)

where La is the overall A-weighted sound level

^

1^( 2 )

fref = 1000 Hz.

Substituting Equation (C-1) into Equation (C-2), the approximation for the band

pressure level at the r*-^ center frequency is:

Lr = La + ALr, dB (C-3)

173
where ALr = A - c(r-q)m

r = 1 , . , . ,N •

Denoting the actual band pressure levels as L^, the overall A-weighted sound

leve is expressed as:

N [Lr+Wr]/10

La = 10 log { I 10 } ,dB (C-4)

r=l

where is the A-weighted relative response value for the r^^ center frequency.

We can now define a normalized spectrum by the set of sound levels:

Lj. = Lj. - La, dB (C-5)

r = 1 , . . . ,N •

In Equations (C-2) and (C-3), the constants A and m are determined by a leastsquare data fit by considering the error between the normalized data, Lf, and

the approximation, AL^* The total mean-square error is then expressed as:

N ~

= I (L - AL^)2 • . (C-6)

r=l

The values of A and m are determined by minimizing the total mean-square error.

The resulting expressions are:

A = 6 1(N+1) [(2N+D/3 - q] 2 Lr

+ [2q - (N+1)] lr«L^}/N(N^-l) (C-7a)

m = (6/c) {(N+1) Z L^ - 2 Er-L^j/NCN^-l ) (C-7b)

where the summations are over r = 1, ...,N.

Table 37 presents the normalized one-third-octave band data used in the present

guidelines. The traffic noise spectrum is based upon the FHWA STAMINA 1.0

model (Ref, 8) and the "composite" spectrum is based upon the spectrum used to

develop the AIF rating (Ref. 21).

For the data in Table 37, the least square procedure described above yields

the following results:

174
TABLE 37. Normalized A-weighted Spectra

f c» HzComposite

spectrum

Traffic Noise

spectrum

f c

»

Hz

Composite

spectrum

Traffic Noise

spectrum

Lr * dB(re L^)Lf

»

dB(re L^)

^r

»

dB(re L^) dB(re L^.)

50 -28.1 - 800 - 9.5 - 8.4

63 -23.1 -3.3 1000 -10.3 - 8.8

80 -17.8 -4.0 1250 -10.9 -10.2

100 -14.2 -4.2 1600 -11.3 -11.4

125 -11.2 -4.6 2000 -11.5 -12.8

160 - 8.9 -6.1 2500 -11.6 -14.9

200 - 8.4 -7.2 3150 -12.5 -17.0

250 - 8.7 -8.5 4000 -13.3 -18.7

315 - 8.7 -8.3 5000 -14.8 -21.2

400 - 8.5 -8.1 6300 -16.2 -23.2

500 - 9.1 -8.0 8000 -20.2 -25.9

630 - 9.4 -8.2 10000 -25.8 -

175
composite spectrum: N = 24; A = -13.5; m = 0.05 (C-8a)

traffic noise spectrum: N = 22; A = -12.4; m = 2.8 (C-8b)

The above values of A and m may be substituted into Equation (C-2) to obtain

the explicit functional form for AL(f). Figure 42 is a plot of both and

A(f) for the composite noise spectrum. Figure 43 is the corresponding result

for the highway traffic noise spectrum. The slope, m, given by Equation (C-7b)

is used to characterize the outdoor noise used in calculating the A-weighted

sound transmission loss of a structure.

C.2 Normalized Sound Transmission Loss

The normalized sound transmission loss is defined in an identical manner as described above for the noise spectrum. The sound transmission data defined by

the set of values {fr,TLr} are used to estimate an expression for the sound

transmission loss as follows:

TL(f) = TLref +

]^Qg(2) (f/^ref) (C-9)

where TLref ~ TL(fref)

fref = 1000 Hz.

For the band center frequencies given by Equation (C-1) and using the least

square error procedure described in Section C. 1 , the estimates of TL^ef and n are given by the expressions:

l^ref = 0 {(N+1) [(2N+D/3 - q] E TL^

+ [2q - (N+1)] Er-TL^}/N(N2-1) (C-lOa)

n = (6/c) {2 Er*TL^ - (N+1) I TLj.} /N( n2-1 ) . (C-lOb)

The summations denoted by E are over the band center frequency index r * 1,...,N

(see Equation (C-1)). Equation (C-10) may be compared with Equation (C-7). It is also mentioned that m is the average slope of the outdoor noise spectrum in

dB/octave and n is the average slope of the sound transmission loss data. As

defined by Equations (C-2) and (C-9), the m is positive if the outdoor noise

spectrum decreases with increasing frequency, and, n is positive if the TL data

exhibit a trend of increasing with increasing frequency.

176
THIRD-OCTAVE

BAND

LEVEL

IN

dB

RE

A-Wt

LEVEL

100 1000 10000

FREQUENCY (Hz)

Figure 42. Normalized Spectrum for Composite Noise

177
10

0

10

20

30

40

50

60

T

100 1000 10000

FREQUENCY (Hz)

Figure 43. Normalized Spectrum for Highway Traffic Noise
C.3 A-Weighted Sound Transmission Loss

This section defines the A-weighted sound transmission loss untilizing the

above approximations for the outdoor noise spectrum and the sound transmision

loss of the structure. Properly, the terminology should be "A-weighted noise

isolation" as described in the main text. However, it will be seen that the

method, in fact, results in a characterization of the noise insulation of the

construction that is adjusted to incorporate the effect of the outdoor noise

spectrum shape in a systematic manner. The objective, of course, is to

estimate the A-weighted noise isolation of the construction.

For outdoor-to-indoor sound transmission, the relationship between the indoor

band sound pressure level, Ljr* and the outdoor band sound pressure level, L^,

for the r^^ band center frequency is;

Lir = Lj. - TLi- + 10 log [(S^/A) coselj. + 6, dB (C-11)

Introducing the A-weighted relative response for the r^^ band and summing over

all bands, the expression for the overall indoor A-weighted sound level is:

Lir = La + 10 log [(S^/A) c^] + 6

N

+ 10 log { j;. lOtLr + Wr -TLj.]/10

J (C-12)

r=l

where L^ is the outdoor overall A-weighted sound level:

Lr = Lj. - La (see Eqn. (C-5)).

In Equation (C-12), it is assumed that the normalization for the receiving room

sound adsorption and the angle-of-incidence correction is essentially independent

of frequency. Considering this term to be a constant, the A-weighted sound

transmission loss is defined as:

TL^ = - 10 log { I lot^r ^r -TL^]/10

[ (C-13)

r=l

For each band center frequency, f^., the normalized outdoor level, Lj., and the

sound transmission loss, TL^., may be approximated using Equations (C-1), (C-3),

and (C-9). The results are:

L^ = ALp = A - c(r-q)m (C-1 4a)

179
TL^ = TLref “ c(q-r)n (C-14b)

Substituting these values into Equation (C-13), the A-weighted sound transmission

loss is approximated by the expression:

TL^ = TLj-ef - A - c(m+n)q

N

- 10 log { I iotWr-c(m+n)r]/10j (C-15)

r=l

Similarily, the A-weighted noise reduction, denoted by NR^, may be estimated by

noting that the outdoor sound level is approximated by the expression:

N

+ A + mcq + 10 log { ^ 10

r=l

[Wj.-cmr

to obtain: ^

NR^ = TL^ef - 10 log [(S^^/A) cos0] - 6 + C^un

(C-16)

(C-17)

where Cnm = "cnq + - B(n-hn)

N

= 10 log { 5; . r=l

The importance of these results is that the approximations to the A-weighted

sound transmission loss and the A-weighted noise reduction indicate relationships

whereby the outdoor noise spectrum shape and the sound transmission loss of the

construction may be characterized independently of each other. This may be seen by realizing that the summations appearing in Equations (C-15) through

(C-17) may be calculated independently of either the specific noise spectrum or the sound transmission loss data.

Since one is mainly interested in estimating the A-weighted noise reduction

(i.e., the difference between the outdoor and indoor A-weighted sound levels),

the values of C^^ required for Equation (C-17) are presented in Figure 44.

Since the products cm and cn are independent of the bandwidth, the value of C^n

is also independent of bandwidth. This means that the above results apply

equally to both octave band and one-third-octave band data.

C.4 Evaluation of the Procedure

A numerical evaluation of the above procedure was conducted to estimate the error between using the direct calculation indicated by Equation (C-12) and the

approximate calculation indicated by Equation (C-17). Since the normalization

terms for sound absorption and angle of incidence are the same in both expressions,

180
Figure 44. Values of the Term

181
the comparison was based upon the following;

(C-18a)

(NRa) approximate ~ ^^ref "* ^n ~6 , dB • (C-18b)

Using the A-weighted traffic noise spectrum given in Table 37 and the average

slope m = 2.8 dB/octave (see Equation (C-8b)), the results indicated in

Table 38 were obtained. These results indicate that, the approximate technique

underpredicts the A-weighted noise reduction by approximately 2 dB, with a sample standard deviation of approximately 1 dB over a range of noise reduction

values between 25 and 35 dBA.

The values presented in Tables 20 through 26 of the main text, were based upon

the direct calculation of the A-weighted noise reduction rather than predicted

values as described above.

C.5 Open Window Conditions

This section presents the basis for the calculation of the average annual

envelope noise level reduction for conditions requiring open windows during

part of the year. The main text emphasizes the importance of maintaining a completely sealed envelope to insure that the design noise level reduction is

achieved. During the cold months of the year, windows will remain closed to

maintain indoor thermal comfort. Similarly, during the warm months air

conditioning may be utilized to maintain indoor thermal comfort. Depending

upon the local climate, however, there is a period during the year when

windows could remain open to achieve the desired Indoor thermal environment.

The question then arises as to the estimation of the annual average value of

the envelope noise isolation if windows are open during a portion of the year

and closed during the remainder of the year.

We begin by defining two values of the envelope noise isolation; one value

corresponding to the closed window condition and the other value corresponding

to the open window condition. These two values represent the extreme conditions,

and we are concerned with calculating a value between these extremes. Example 6

in the main text illustrates how one estimates the envelope A-weighted noise

level reduction for closed window conditions. Example 7 illustrates the steps

for estimating the noise isolation for open windows. Both of these values

depend upon the percentage of glazing area of the envelope surrounding the room

and the open area of the window.

We define the closed and open envelope noise isolation as follows;

(^La) closed the A-weighted noise isolation with windows closed

(ALA)open the A-weighted noise isolation with the window open

182
Table

38.

Comparison

Between

Direct

and

Approximate

Calculation

of

A-Weighted

Noise

Reduction:

Highway

Traffic

Noise

Spectrum

CO

U-l <u vO '3- m u-i O D '3- m '3' m

(U CO < O o O 0

bc > oc u

c

CO o:

TJ <

CX c o c c z CN

c

o

CO

<-• >

a. a; E TJ

CO

c/2 "03

COc

CO

CO

(U u

CU CO O E

C -H

<U X U o

0) u

u-i a. CM a <: «3- OC sf o •H CO PQ • . . • 73 73

1 (N CN m

C

1 + + + +

(U CJ T. CU

73

(U rM o; O. N 00 E -H PO

CO CD ^4

CO

c

o

•HU

u

3 o bo M bO c M (U •H cn CO CO

CO u N M CM c CO CO o O

o o •-H <c o O a Q DO

183
The average annual outdoor value is denoted as

With these definitions, we then obtain the average indoor day-night sound

levels

:

(^dnl) open ~ ^dnO ” (ALy^) open windows open all day (C-19a)

(Ldnl) closed = L^nO " closed for windows closed all day (^-195)

From the definition of the equivalent sound level, the average annual indoor

sound level for the windows open and the windows closed is expressed as;

I-dnl = 10 log

I (Topen/Tyear) ' lO^l-dnl) open/10

+ (^closed/Var^ * closed

[ ,dB (C-20)

where TQpg^ and T(.]^Qggd represent the average number of days that the windows

are open or closed per year, respectively, and

fyear “ ^ay per yar = ^closed *

We now define the percentage of time that the windows are open as:

^open “ 100 (Topen/fyear

)

and note that

^closed “ ~ ^open

Substituting these definitions into Equation (C-20), we obtain the expression

for the average annual envelope noise isolation as:

IdnO -I-dnl = - 10 log) (Popen/100) • IQ-ll'l-Alopen/lO

+ (d-P^pgjj)/100 • lO'l^l-Alclosed/lO

j ,dB (C-21)

This result was used to calculate the values shown in Table 32 using

(ALA^)open “ and the range of values for (ALy^)Qiosed and Popen*

C.6 Formulation or Worksheets

This section describes the mathematical basis for the worksheets and lookup

tables used to calculate the noise reduction of the building envelope.

Figure 32 illustrates the physical aspects of each worksheet and the nomenclature

184
utilized in the present guidelines. Table 28 of the main text lists the

purpose of each worksheet. The present discussion focuses upon the formulation

of each worksheet, and is provided because the steps utilized may not appear

”a priori" to correspond to the steps one might use in a direct calculation.

Worksheets V through VIII are used to calculate the indoor DNL contribution for

each envelope member and each outdoor noise source. The results obtained in

Worksheet VIII must be combined using Table 16 for each outdoor noise source.

The indoor DNL values for all noise sources must then be combined using Table 16

to determine the total indoor DNL at the site. Since the worksheets are used

to calculate the indoor DNL contribution for each envelope member, the discussion will assume that the outdoor noise source is fixed and the corresponding

outdoor DNL is used to estimate the indoor DNL.

The envelope member is composed of several elements, with each element exhibiting

an A-weighted TL value corresponding to the noise source being considered. The

noise reduction provided by the envelope member is denoted by NR and depends

upon the following:

TL - the composite A-weighted sound transmission loss of the envelope

member

,

- the total surface area of the envelope member,

A - the total room sound absorption,

6 - the constant difference between the non-diffuse outdoor sound field

and the diffuse indoor sound field, and

cos 9 - the angle of incidence correction (site condition).

The mathematical relationship is (see Equation (C-17)):

We now proceed to rearrange this relationship into a form convenient for

presentation in a worksheet format. Since we want to estimate the indoor DNL,

denoted by (Ljj^j)];, we must relate NR to the outdoor DNL and the indoor DNL.

Further, we remember that the TL value is based upon the outdoor sound field

incident upon the envelope member. Our relationship is then of the form:

NR = TL - 10 log [(S^/ A) cose] -6 , dB (C-22)

" (^dn)o + ^I (Ljin)l (C-23)

where Aj

to

is an adjustment to the outdoor DNL value for the noise source account for the sound energy incident upon the element.

185
Denoting the right hand side of Equation (C-22) as TLa<jjugted» substitute

equation (C-23) into equation (C-22) and solve for The result is:

(^dn^I “ (^dn)o + “ ^adjusted > (C-24)

and is the basis for the calculations contained in Worksheet VIII. Note that

in Worksheet VIII, Aj is the DNL adjustment for the exposure of the member to

the noise source and is obtained as indicated in Figure 24. The value of

TLadjusted obtained from Worksheet VII.

With the above steps, the expression for is:

TLadjusted = TL - 10 log [(S^/ A) cos 9] -6 , dB • (C-25)

Worksheet V through VII are used to calculate this expression. However, the

explicit relationship for obtaining the value of the TL from the values of TL^

for the various elements of the envelope member must now be incorporated.

Doing this we obtain:

- TL /lO

n i

TLadiusted = " 10 (Sj^/S^)10 ] - 10 log[ (S^/A)cos9 ] -6 (C-26)

i=l

t" Vi where TL^^ is the A-weighted sound transmission loss value of the i*^"

member element

is the surface area of the i^l' member element.

Equation (C-26), however, is not in a form convenient for a worksheet format.

We now proceed to cast our expression in an appropriate format. To do this we wish to separate terms into simple expressions that may be added together in

dB units. Further, we approximate the room sound adsorption. A, using the

relationship A=cSfj^, where c is a constant and Sf£ is the floor area of the

room. The average value of c is 0.80 as explained in the main text. Doing

this, we obtain the result

TLadjusted “ TLg - 10 log[cos9] + 10 log(c) (C-27)

where

n -TLi/10

TLg - 10 log [j; (Si/Sf£)10 ] -6

i=l

The calculations indicated by Equation (C-27) are conducted using Worksheet VII.

The term - 10 log[cos9] is the angle of incidence correction from Figure 25

appropriate to the noise source, and the room sound absorption adjustment,

- 10 log(c), is obtained as described by the footnote to Worksheet VII

("10 log(0.8) = - 1.0 dB).

It is now necessary to calculate the value of the composite sound transmission

loss, TLg. This is accomplished by using Worksheets V and VI. First, however,

it is best, once again, to rearrange the expression for TLg into a form convenient

for a worksheet format. This is done by defining the following two quantities:

186
Agj^ = - 10 log (Sj[/Sfjj),

TLi = TLi -6 •

(C-28a)

(C-28b)

With these definitions, the expression for TL^, becomes:

n -(TLi+ Agi)/10

TLc - - 10 log[Z 10 ] , dB • (C-29)

i=l

The calculation indicated by Equation (C-29) is performed using Worksheet VI

and will be explained momentarily.

First , we consider the calculations for Worksheet V which evaluates the quantity

TLi ^si* value TLj^ is obtained from Tables 20 through 26 or as described in section C.3 of this appendix (see equation (C-17)). As described

in Section C.3, TL^ = T^ref ^mn* adjustment, Ag^, is defined

by Equation (C-28a) and is given in Table 29. We now focus upon the calculations in Worksheet VI.

To explain the calculation procedure we express Equation (C-29) as follows:

n -t^/lO

TLc * - 10 log[Z 10 ] (C-30)

i=l

where t^ * TL^ + Agi and is obtained from Worksheet V.

Now, we use examples to illustrate the calculations for Worksheet VI. Consider

an envelope member with two elements. We can then obtain values of tj^ and t2

using Worksheet V and we need to evaluate

-ti/10 -t2/10

TLc = ~ 10 log[10 + 10 ] (C-31)

-ti/10 -t2/10

without directly calculating either 10 , 10 or using logarithms.

We now express Equation (C-31) as follows:

TLc = ti + Ac (C-32)

(ti-t2)/10

where Ac = ~ 10«log(l +10 )

•

We note that Ac depends only upon the difference between the two values t i and

t 2

. For large positive values of this difference (i.e., (t^-t 2 ) ^c ” ^2 “ ^1 ^c ^ ^2 bhe combined TL value is close to the TL value

of the "weaker" component). For large negative values of this difference

(i.e., t]^ « t2) then Ac ® 0 and TLc t^ (i.e., the combined TL value is

187
approximately equal to the value of the "weaker" component). Further, we note

that the value of TLq does not depend upon which element is assigned the value

ti or t 2

» Values for A^, are presented in Table 30 of the main text.

Consider now a three-element wall where:

-ti /10 -t 2/10 -t 3/10

TLc = - 10 log[10 +10 +10 ] ,dB • (C-33)

We combine the first two elements as described above to obtain TL(,2 “ + A^, which yields the result

-TLc2/10 -(ti+Ac )/10 -ti /10 -t 2/10

10 =10 » 10 + 10

Then, the expression for TL^ of the three-element wall becomes:

-TLc2/10 -t3/10

TLc = - 10 logtlO +10 ] , dB (C-34a)

, dB

TLc3 = TLc2 + Ac (C-34b)

(TLc2 - t3)/10

where Ac = ” 10 log[l +10 ] •

The calculations indicated by Equation (C-34a) are identical to the calculations

for the two-element wall, except that we use TLc2 ^3 to evaluate Ac. One

may repeat the above argument for an envelope member with four or more elements

and realize that we combine the t^ values using two "elements" at each stage.

After the first combination, however, one of the elements is the combination

resulting from the previous step. Worksheet VI is formatted to accomodate up

to five elements; however, the same format could be used for any number of

elements.

188
D. ENVIRONMENTAL NOISE DESCRIPTORS FOR NOISE-COMPATIBLE LAND USE PLANNING

Obtaining environmental noise information that is meaningful for land use planning efforts is predicated upon the choice of a noise measure (or measures)

which accurately describes the noise environment in terms that are relevant to

human response to noise.

The accumulated evidence of research on human response to sound indicates

that the magnitude of sound as a function of time and frequency is the major

basic indicator of human response. The dominant characteristic of community

noise is that it is not steady — at any particular location the noise fluctuates

considerably from quiet at one instant to loud the next. Over the last few

years, two very closely related noise measures that capture both the characteristics of environmental noise and human response have emerged as particularly

useful for land use planning. These measures are the equivalent sound level

(Leq) and the yearly day night sound level (Ldn» DNL) in decibels.

[Refs. 1,2,10,47,48,49 and 50]

The equivalent sound level (Leq) is used primarily to describe and assess

the noise environment, present or prospective, at those sites where the concern

is for the effects of noise over a short period of time (e.g. 1-hr. , 8-hr.),

rather than over the entire 24-hour period as, for example, in commerical and

industrial areas. The equivalent sound level is the A-weighted sound level of

the steady-state noise which has the same energy content, in a specified period

of time, as the time-varying noise. Thus, two sounds, one of which contains

twice as much energy as the other but lasts only half as long as the other,

would be characterized by the same equivalent level. The mathematical definition of Lgq is;

T L(t)/10

Leq = 10 log

1 ^

J 10 dt}, dB. (D-1)

The yearly day night sound level (Ljn or DNL) is used to describe the

average noise environment, present or prospective, at those sites where the

concern is for the effects of noise over the entire 24-hour period, such as in

residential areas and hospital zones where a primary consideration is the needs

of residents for rest and quiet. The DNL is the average A-weighted equivalent

sound level for the entire 24-hour period with a nighttime penalty of 10 dB

added to the Leq between 10 p.m. and 7 a.m. The penalty is intended to account

for the increased sensitivity of people to noises that occur during sleeping

hours relative to waking hours. During the night, interior background noise

levels in most residential areas generally drop far below their daytime levels.

Moreover, the activities of most households at night also decrease during

sleeping hours thereby lowering internally generated noise levels. Thus, noise

events occurring at night are more intrusive since the increase in the noise

level of the noise event over the background is greater at night than it is

during the day.

189
Mathematical definition of DNL is:

L^n = 10 log

{ ^

if / (p_23)

day night

or, if L(t) is based upon average conditions so that it is characterized by an average hourly value, is:

L /lO L /lO

Ldn = 10 log 10 24 ^

where l^day “ ^ ^ 10^^

average

daytime

hour

where ^ight ^ ^ ^ 10^^^^/^^dt}

average

nighttime

hour

While the yearly day night sound level and the equivalent sound level have

emerged as the most useful and widely used noise measures for land use planning

efforts other schemes are still encountered. These include the community noise

rating (CNR), the noise exposure forecast (NEF), the community noise equivalent

level (CNEL), and the statistical descriptors, in particular the level exceeded

10 percent of the time (Liq)* this reason a brief description of these

noise measures and of their relationships follow.

Both CNR and NEF were primarily developed for evaluating noise-compatible

land use around airports. CNR was the direct outcome of the experience gained

by consultants in their practice and their Interpretation of the limited research

data that was available in the 50's when CNR was proposed [Ref. 53). Originally,

CNR was merely a scheme for interpreting community reactions to noise exposure

in a number of case studies involving different noise sources.

The orginal CNR specified that the noise was to be measured and plotted as octave-band levels. The resulting graph was then to be compared to a set of

other curves which resembled the loudness contours. The curves were plotted at

5 dB intervals in the mid-frequency region. On the basis of these comparisons,

a noise rank level was assigned to the noise, corresponding to the highest

rating curve into which a measured spectrum Intruded. The values obtained were

then adjusted by a series of noise corrections based on noise spectra, ambient

levels in the community, the "intrusiveness” of the noise, and whether or not

It had an impulsive character and was repetitious. A correction was also

190
applied to account for the previous experience of the community with the

particular type of noise exposure being evaluated. In addition, adjustments

were provided for the time of day and the period of the year during which the

noise occurred. Each adjustment factor had the effect of either raising or lowering the rank level originally obtained. A range of discrete community

responses as a function of CNR was provided to assist in the interpretation of

the data. These community responses included no reaction, sporadic complaints,

widespread complaints, threat of legal action, and vigorous community reaction.

Since its proposal in 1955, CNR has undergone changes. One of the major

changes was the substitution of the preceived noise level as a means of determining the noise level rank, thus shifting the emphasis from consideration

of loudness to consideration of annoyance as a major attribute of community

response to noise [Ref. 54). As more research data became available more

refinements were incorporated into the noise measure. For example, adjustments

for the duration of individual aircraft flyovers and for the presence of discrete

frequency components were developed as these were found to influence human

response. Finally, a computational scheme for assessing the cumulative effects

at various points around airports of the noise produced by different aircraft

types flying along different flight paths was proposed. The procedure eventually

evolved into the noise exposure forecast (NEF) which allowed NEF to be plotted

on a map of the neighborhood surrounding an airport. Thus, areas experiencing

similar noise exposures could be enclosed in contours drawn on a map of the

land around an airport.

The NEF methodology was adopted by the Federal Administration (FAA) in its

efforts to assess land uses around civilian airports and for determining the

effects of changes in aircraft operating procedures, the introduction of new

types of aircraft in the fleet, or changes in the aircraft mix at a particular

airport [Refs. 54 and 55] . It was also used by the department of Housing and

Urban Development (HUD) until recently to assess the eligibility for assistance

for construction of residential developments around airports.

When used for land use planning purposes, the NEF values were interpreted

as follows. In areas located in zones where the NEF values were equal or less

than 20 no complaints were expected from the community; accordingly, such areas were considered suitable for residential development. In areas where the NEF

values ranged from 20 to 30 some activities, expecially those involving speech

communication, might be interferred with; thus, noise consideration was called

for when the area was proposed for residential development. Areas where the

NEF values were between 30 and 40 were usually considered to be suitable for

commercial development and for office buildings, provided these latter buildings

included some form of soundproofing if speech communication was an important

consideration. Residential and school development by and large were not found

compatible for these areas as the noise exposure levels were severe enough to

elict complaints and possibly group action. Finally, in areas where NEF values

were equal or greater than 40, activities demanding of speech communication

were found undesirable, and all buildings were considered to reauire soundproofing

treatment to protect occupants from undue noise exposure.

191
The community noise equivalent level (CNEL), used primarily in California

to monitor land use planning around airports [Ref. 57], is an A-weighted energy

average level for the 24-hr period with 5 dB weighting factor for the noise

levels occurring in the evening between 7 a.m. and 10 p.m. increased to 10 dB

for night events occurring between 10 p.m. and 7 a.m. CNEL is essentially

identical to DNL except for the evening penalty. For most distributions of

noise levels around airports, the numerical difference between DNL and CNEL is

insignificant in most instances, amounting to less than 1 dB.

There does not exist a fixed relationship between DNL, CNEL, CNR and NEF

because not all of these schemes handle frequency weighting in the same manner,

nor consider the duration of individual events or the presence of discrete

frequency components, nor apply the night penalty in an identical fashion. For

example, DNL and CNEL account for the differential sensitivity of people to

various frequencies by means of the A-weighting while CNR and NEF use the

perceived noise level. Similarly, while CNEL, DNL, CNR and NEF all penalize

noise events occurring between 10 p.m. and 7 a.m, by 10 dB, the details concerning the manner in which the penalty is applied differ. In the case of CNR and

NEF, it is the nighttime exposure that is weighted, where as in the case of

DNL, the penalty is applied to the level directly rather than to the exposure.

Nevertheless, one may translate one noise measure into another by using the

following relationship, which for most instances, yield approximations that are valid within a ^3 dB tolerance.

LDN = CNEL = NEF + 35 = CNR - 35 (D.3)

Until several years ago the Federal Highway Administration (FHWA) specified

the upper limit of acceptable highway traffic noise for different types of land uses around highways in terms of the A-weighted sound level exceeded 10 percent

of the time (Ljo) [Ref. 58]. Since assitance from the FHWA in the form of

highway construction or reconstruction grants is contingent upon the assessment

of traffic noise impacts and consideration of noise abatement measures, many

state highway departments throughout the country performed noise analyses in

terms of L^o*

Most free-flowing traffic gives rises to a normal (i.e., Gaussian)

distribution of noise levels. In such cases the relationship between Leq and

Liq is given by:

Leq = Ljq - 1.28 s + 0.115 s^, dB (D.4)

where s is the standard deviation of the noise level distribution. For values

of s ranging from 1 to 10 dB, the relationship between Leq and L^o '”^7 approximated by:

Leq - Lio “2, dB. (D.5)

For most highways the standard deviation is on the order of 2 to 5 dB. In

such cases Equation (D.5) above is correct to within +1 dB.

192
The Department of Housing and Urban Development (HUD) provides minimum

national standards designed to protect residents from excessive noise exposure

In their homes and communities through assistance for new construction and/or

rehabilitation of older buildings. Until 1979, HUD noise standards for all

environments other than those of airports were expressed in terms of the amount

of time in a 24-hr period during which the A-weighted sound levels could not

exceed defined values. Four categories of land uses — unacceptable, normally

unacceptable, normally acceptable, and acceptable were defined as a function of

noise levels. For example, areas impacted for 10 minutes out of the 24-hr

period by A-weighted noise levels of 80 dB or exceeding 7-5 dB for 8 hr were

considered totally "unacceptable" for residential use, while areas where the

A-weighted sound levels did not exceed 65 dB for more than 8 hr per 24-hr were

considered to be "normally acceptable."

There does not exist a well-defined relationship between these former HUD

noise standards and other noise measures. For example, values of Lgq up to 95

dB could be in compliance with the former HUD standards depending upon the time

distribution of the noise levels considered. However, as mentioned previously,

HUD has revised its interim noise standard which are now expressed in terms of

the day-night average sound level. [Ref. 50]

.

193
APPENDIX E. AVERAGE SOUND TRANSMISSION LOSS OF EXTERIOR BUILDING ELEMENTS

In this appendix the average sound transmission loss values of each type of

building element described in Tables 20-26 of Section 3.2 of the main report

are presented. These values were obtained by averaging, at each 1 /3-octave

band, the sound transmission loss data compiled from many sources. Also

Included in this appendix are plots of these average sound transmission loss

values, the minimum and maximum values observed for each construction type,

and the standard deviation of these data.

194
^

0 r .... I 1 > . . ..J . 1 1 » *--3

in 50 100 200 500 1000 2000 5000 10000

FREQUEINCY, Hz.

Hz dB Hz dB

125 16 800 39

160 18 1000 41

200 22 1250 43

250 25 1600 44

315 28 2000 45

400 31 2500 43

500 34 3150 43

630 37 4000 45

Figure 45. Average and range of sound transmission loss of metal

and curtain walls consisting of 2 sheets of galvanized steel with

insulation and having an area weight of less than 6 Ibs/ft^.

195
Hz dB Hz dB

125 33 800 43

160 32 1000 45

200 34 1250 47

250 34 1600 49

315 35 2000 50

400 36 2500 52

500 39 3150 54

630 41 4000 55

Figure 46. Average and range of sound transmission loss of 4-7-in

masonry walls consisting of either 4x8x16 concrete blocks or mortared bricks without finish.

196
>y

i3

Hz dB Hz dB

125 34 800 54

160 35 1000 55

200 37 1250 57

250 37 1600 58

315 39 2000 60

400 40 2500 60

500 45 3150 58

630 50 4000 61

Figure47. Average and range of transmission loss of 4-7-in

masonry walls consisting of 4x8x13 3-cell concrete blocks with

resilient channels 24-in o.c. and 1/2-in plaster board.

197

dB
in 5B IBB 200 5B0 IBBO 200B 5000 18000

FREIQUEINCY, Hz.

Hz dB Hz dB

125 29 800 51

160 34 1000 51

200 42 1250 53

250 42 1600 54

315 46 2000 56

400 48 2500 54

500 51 3150 54

' 630 51 4000 58

Figure 48. Average and range of sound transmission loss of 7/8-in stuccoed wall with No. 15 felt building paper and 1-in wire mesh with

2x4 wood studs 16-in o.c. with fiberglas building insulation and 1/2-in

gypsum board screwed to channel.

198
LO 50 100 200 500 1000 2000 5000 10000

FREIGUENCY, He.

Hz dB Hz dB

125 36 800 49

160 37 1000 51

200 39 1250 53

250 39 1600 56

315 41 2000 58

AOO 42 2500 57

500 44 3150 58

630 47 4000 62

Figure ^9. Average and range of sound transmission loss of dense

concrete walls 8-in thick consisting of 3-cell blocks with perimeter

sealed.

199
IfJ 50 100 200 5B0 1000 2000 5000 10000

FREIQUEINCY, Hz.

>u

Q

. (9 D H

h

11

Hz dB Hz dB

125 37 800 53

160 39 1000 55

200 40 1250 58

250 43 1600 61

315 44 2000 63

400 46 2500 64

500 48 3150 65

630 51 4000 67

Figure 50. Average and range of sound transmission loss of 8-in thick

masonry walls consisting of either bricks mortared together or 3-cell

concrete blocks with block filler with 1/2-in plaster and finished

with latex paint.

200
>

^

1 0 b- l. 1..1. L I 1 1 1 1 1 1 . t I 1 1 1 1 1 1 1.

in 50 100 200 5B0 10B0 200B 5000 10000

FREQUENCY, Hz.

Hz dB Hz dB

125 37 800 58

160 38 1000 61

200 40 1250 64

250 43 1600 66

315 46 2000 67

400 48 2500 66

500 51 3150 66

630 55 4000 67

Figure 51. Average and range of sound transmission loss of masonry

walls 8-in thick consisting of 18x16x8 3-cell concrete blocks with

resilient channels 24-in o.c. with 1/2-in plaster board and painted

on both sides.

201
L/J 50 100 200 5B0 1000 2000 5000 10000

rPEGUEINCY, Hz.

Hz dB Hz dB

125 41 800 59

160 43 1000 60

200 44 1250 62

250 44 1600 63

315 46 2000 64

400 48 2500 65

500 51 3150 67

630 55 4000 66

Figure 52. Average and range of sound transmission loss of double

brick walls consisting of 4—1/2—in walls separated by 2—4— in cavity

with wire ties and 1/2-in plasterboard on both sides.

202

DEV
SOUND

TRHN5MI55ION

LOSS.

dB

>

50 100 300 5B0 10B0 200B 5000 10000

rREQUEINCY, l-lz .

Hz dB Hz

125 800

160 1000

200 1250

250 1600

315 2000

400 2500

500 3150

630 4000

Figure 53. Average and range of sound transmission loss of light

frame wood wall with 2x4 wood studs 16-in o.c., 2-3-in insulation

and finished with 1/2-in gypsum board.

203
Hz dB Hz dB

125 20 800 34

160 22 1000 35

200 25 1250 36

250 26 1600 37

315 28 2000 37

400 28 2500 38

500 30 3150 38

630 33 4000 38

Figure 54. Average and range of sound transmission loss of light

frame walls with wood siding, 2x4 wood studs with insulation, resilient

channels 24-in o.c., finished with 1/2-in gypsum board and penetrated

by 25-30 percent glass.

204
1 Hz dB Hz dB

125 21 800 38

160 23 1000 39

200 26 1250 40

250 28 1600 42

315 31 2000 41

400 32 2500 42

500 33 3150 42

630 36 4000 43

Figure 55. Average and range of sound transmission loss of light frame

walls with wood siding, 2x4 wood studs 16-in o.c. with insulation,

resilient channels 24—in o.c., finished with 1/2-in gypsum board and

penetrated by 25 to 30 percent single glazed sealed glass with storm sash.

205
FREIQUENCY, Hz.

Hz dB Hz dB

125 22 800 38

160 24 1000 39

200 27 1250 40

250 29 1600 41

315 31 2000 43

400 31 2500 43

500 34 3150 43

630 36 4000 44

Figure 56. Average and range of sound transmission loss of light

frame walls with either brick veneer or wood siding, 2x4 wood studs

16- in o.c. with fiberglass insulation and penetrated by a 10-15 percent

single strength glazed sealed window.

206
in 50 100 200 5B0 10B0 206B 5000 10000

TREQUENCY, hiz .

Hz dB Hz dB

125 21 800 36

160 23 1000 37

200 26 1250 38

250 28 1600 39

315 29 2000 40

400 30 2500 41

500 32 3150 40

630 35 4000 41

Figure 57 . Average and range of sound transmission loss of light

frame walls with either wood siding or brick veneer, 2x4 wood studs,

resilient channels 24-in o.c. and 1/2-in gypsum board but no insulation

and penetrated by 25-30 percent single glazed sealed glass.

207
Q

0 F . . 1 I 1 1 1 1 . . .. 1 I i__j 1 1 1—I—i_i_*d

in 5B 10EI 200 SB0 1000 2000 5000 10000

F”R^QLJENC^Y , Ws .

Hz dB Hz dB

125 20 800 39

160 23 1000 40

200 26 1250 41

250 29 1600 43

315 32 2000 42

400 33 2500 43

500 35 3150 43

630 37 4000 44

Figure • Average and range- of sound transmission loss of light

frame walls with either wood siding or brick veneer, 2x4 studs with

insulation, resilient channels 24-in o.c.

,

1/2-in gypsum board and penetrated by 25-30 percent single glazed sealed glass with storm sash.

208
SOUND

TRRI

J5MI5SION

LOSS.

dB

Hz dB Hz dB

125 22 800 29

160 21 1000 30

200 22 1250 32

250 23 1600 32

315 24 2000 33

400 25 2500 33

500 26 3150 33

630 27 4000 33

Figure 59. Average and range of sound transmission loss of 3/82-7/16-in

thick single glazed sealed windows.

209
SOUND

TRRNSMISSrON

LOSS,

dB

10 IC ;

2f ‘ >

I 1 .i-.i I 1 . —I III,* 50 100 200 500 1000 2000 5000 10000

FREIQUEINCY, Hz.

Hz dB Hz dB

125 22 800 23

160 20 1000 25

200 21 1250 24

250 21 1600 27

315 20 2000 29

AOO 20 2500 30

500 20 3150 30

630 21 4000 31

Figure ^0. Average and range of sound transmission loss of 3/32-7 /16-in

thick single glazed unsealed windows.

210
SOUND

rKHrsISMISSrON

LOSS.

dB

50 100 200 500 1000 2000 5000 10000

FREQUENCY, Hz.

Hz dB Hz dB

125 19 800 32

160 17 1000 33

200 20 1250 37

250 22 1600 36

315 23 2000 38

400 24 2500 37

500 28 3150 39

630 29 4000 39

Figure 61. Average and range of sound transmission loss of single

strength panes with storm sashes unsealed.

211

dB
SOUND

TRRNSMISSrON

LOSS,

1 0

0

. <a Q "O

I-4)

50 100 200 5B0 1000 2000 5000 10000

FREZQUEINCY, Hz.

Hz dB Hz dB

125 23 800 38

160 21 1000 39

200 23 1250 42

250 25 1600 43

315 26 2000 44

400 29 2500 45

500 32 3150 47

630 4000 46

Figure 62. Average and range of sound transmission loss of single

strength sealed windows with storm sashes.

212

DtV
Hz dB Hz dB

125 26 800 33

160 22 1000 36

200 23 1250 38

250 25 1600 39

315 24 2000 41

400 24 2500 41

500 28 3150 39

630 30 4000 35

Figure Average and range of sound transmission loss of double

glazed sealed windows consisting of parallel panes of the same thickness

contained within a range of 3/32-3/8-in, mounted in one sash with an interpane spacing of less than 1/2-in.

213
>

in 50 190 ?ee 500 1000 2000 5000 10000

FREIQUEINCY, Hz.

Hz dB Hz dB

125 25 800 40

160 17 1000 42

200 21 1250 43

250 22 1600 43

315 26 2000 43

400 30 2500 43

500 35 3150 40

630 38 4000 38

Figure 64. Average and range of sound transmission loss of double

glazed sealed windows consisting of two panes of the same thickness

contained within a range of 3/32-1/8-in mounted in parallel in one

sash with an interpane spacing greater than 1/2 in.

214
m

•0 ?0

in

ino

j

z

G

B0

50

in ‘0

Lfj r ?0

inz

IT 20

u

O

in

Hz dB Hz dB

125 28 800 40

160 19 1000 41

200 24 1250 42

250 26 1600 43

315 26 2000 41

400 29 2500 40

500 33 3150 42

630 37 4000 40

Figure 65. Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of different thicknesses,

1/8 and 1/4-in mounted in one sash in parallel with an interpane spacing

of 1/2-3/4-in.

215
Hz dB Hz dB

125 28 800 40

160 20 1000 42

200 22 1250 43

250 25 1600 43

315 25 2000 42

400 32 2500 41

500 34 3150 39

630 37 4000 38

Figure Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of different thicknesses,

1/8 and 1/4-in mounted in one sash not in parallel with maximum

interpane spacing of 3/4-in and minimum interpane spacing of 1/4-in.

216
m

T3 ?0

in

ino

j

B0

O

50

in 40

inr 30

in

in 20

dL

in

Hz dB Hz dB

125 26 800 45

160 32 1000 45

200 32 1250 47

250 32 1600 47

315 34 2000 47

400 38 2500 46

500 41 3150 45

630 43 4000 43

Figure 67. Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of the same thickness, contained

within a range of 5/32-1/4-in mounted in parallel in 2 sashes with an interpane spacing of 2-1/2 to 4-in.

217
IP 50 100 200 500 1000 2000 5000 10000

FREIQUEINCY, Hz.

Hz dB Hz dB

125 26 800 46

160 33 1000 46

200 33 1250 48

250 34 1600 49

315 36 2000 49

400 39 2500 48

500 42 3150 45

630 44 4000 44

Figure Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of the same thickness, contained

within a range of 5/32—1/4 in mounted in parallel in 2 sashes with an interpane spacing of 3-6-in.

218
>u

2

CQ

•D 70

in

Z

50

0

in 40

in

i-i r 30

in^ 20

[t

1 0

0

n 50 100 200 500 1000 2000

FREQUEINCY, . 5000 10000

. s

Q 0

I-iJ

Hz dB Hz dB

125 27 800 47

160 34 1000 48

200 35 1250 49

250 36 1600 50

315 38 2000 51

400 40 2500 49

500 44 3150 46

630 46 4000 46

Figure 69. Average and range of sound transmission loss of double

glazed sealed windows consisting of parallel panes of the same thickness

contained within a range of 5/32-1/4-in mounted in 2 sashes in parallel

with a interpane spacing greater than 6-in.

219
>

in 50 100 200 500 1000 2000 5000 10000

FREIQUEINCY, Hz.

Hz dB Hz dB

125 25 800 41

160 24 1000 42

200 26 1250 43

250 26 1600 43

315 29 2000 42

400 31 2500 42

500 36 3150 43

630 39 4000 43

Figure 70. Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of different thicknesses

each 1/8 and 1/4-in mounted in parallel in two sashes with an interpane

spacing between 1 and 1-1/2-in.

220
m 50 100 200 580 1000 2000 5000 10000

FREIQUENCY , Hs .

Hz dB Hz dB

125 28 800 43

160 29 1000 44

200 29 1250 45

250 30 1600 45

315 32 2000 45

400 34 2500 44

500 39 3150 43

630 41 4000 44

Figure 71. Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of different thicknesses,

each 1/8 and 1/4-in, mounted in parallel in 2 sashes with an interpane

spacing between 1-1/2 and 2-in.

221
in 50 100 200 5B0 1000 220B 5006 10006

FREQUENCY, Hz.

Hz dB Hz dB

125 28 800 46

160 34 1000 47

200 34 1250 48

250 36 1600 48

315 36 2000 48

400 39 2500 48

500 42 3150 49

630 44 4000 50

Figure 72. Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of different thicknesses,

each 1/8 and 1/4-in, mounted in parallel in 2 sashes with an interpane

spacing between 2-1/2 and 6-ln.

222
>

1/1 50 100 200 500 1000 2000 5000 10000

FREQUEINCY, Hz.

Hz dB Hz dB

125 26 800 44

160 29 1000 45

200 29 1250 46

250 30 1600 46

315 32 2000 46

400 35 2500 46

500 39 3150 46

630 41 4000 44

Figure 73. Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of different thicknesses

each 1/8 and 1/4-in mounted in 2 sashes not in parallel with a maximum

interpane spacing of 3-in and a minimum interpane spacing of 1-in.

223
Hz dB Hz dB

125 27 800 45

160 30 1000 45

200 30 1250 46

250 32 1600 47

315 33 2000 47

400 35 2500 48

500 39 3150 49

630 41 4000 48

Figure 74. Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of different thicknesses

each 1/8 and 1/4-in, mounted in 2 sashes not in parallel with a maximum

interpane spacing of 3-in and a minimum interpane spacing of 2-in.

224
Hz dB Hz dB

125 28 800 46

160 34 1000 46

200 33 1250 48

250 33 1600 48

315 35 2000 48

400 39 2500 48

500 42 3150 47

630 44 4000 46

Figure 75. Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of different thicknesses

each 1/8 and 1/4-in, mounted in 2 sashes not in parallel with interpane

spacing of 6-in and minimum interpane spacing of 2-in.

225
Hz dB Hz dB

125 26 800 44

160 29 1000 45

200 29 1250 46

250 29 1600 47

315 33 2000 47

400 36 2500 47

500 40 3150 46

630 41 4000 43

Figure 76. Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of the same thickness contained within a range of 1/32-1/8-in, mounted in 2 sashes not in parallel

with a maximum interpane spacing of 3-in and minimum interpane spacing

of 1-in.

226
>

3b

100 200 5ae 10B0 2000 5000

FREIQUEINCY , Hz .

Hz dB Hz dB

125 28 800 46

160 33 1000 46

200 33 1250 48

250 33 1600 48

315 35 2000 48

400 39 2500 48

500 42 3150 46

630 43 4000 45

Figure 77. Average and range of sound transmission loss of double

glazed sealed windows consisting of panes of the same thickness contained

within a range of 1/8-1/ 3-in, mounted in 2 sashes not in parallel with

a maximum interpane spacing of 6—in and a minimum interpane spacing

of 2-in.

227
Hz dB Hz dB

125 26 800 36

160 21 1000 39

200 25 1250 41

250 21 1600 43

315 22 2000 45

400 24 2500 45

500 27 3150 43

630 33 4000 36

Figure 78. Average and range of sound transmission loss of triple

glazed sealed windows consisting of 1/8-in panes mounted in 1 wood

sash with interpane spacing ranging from 1/8-13/32-in.

228
yQ

ITJ 5B 10B 200 5B0 10B0 200B

FREQUEINCY, Hz

5000 10000

. (n D 15

I-0

Hz dB Hz dB

125 25 800 42

160 24 1000 44

200 24 1250 45

250 26 1600 46

315 30 2000 48

400 31 2500 48

500 36 3150 48

630 39 4000 48

Figure ^9. Average and range of sound transmission loss of triple

glazed sealed windows consisting of 2 panes 1/8-in thick, mounted in

1 wood sash with an interpane spacing of 1/4-in and a metal spacer and

with a third pane 1/8-in thick mounted in a separate sash with a 3/4-2- in

space.

229
m

0

F2

in

ino

J

z

o

60

50

If) 'e

10M

Z 30

in

IE 20

[Kh

z

O

in

10

0

Hz dB Hz dB

125 27 800 42

160 26 1000 44

200 27 1250 45

250 29 1600 46

315 31 2000 46

400 32 2500 48

500 37 3150 48

630 40 4000 46

Figure 80. Average and range of sound transmission loss of triple

glazed sealed windows consisting of 2 panes 1/8— in thick, mounted in

1 wood sash with an interpane space of 1/4—in and a metal spacer and

^Eth the third pane consisting of either a 1/8 or 1/4—in thick glass

mounted in a separate sash 3/4-2-in away.

230
B ^ c L

P0 rin

j

Ss0 iZ50

in e Ein p I 30

in

(E 20 ^

Ql t

, C „ 10 ^

3

-P§

3

3

1 o

>

kia

. m

Q -0

5® "

in 50 100 200 530 1000 0000

F”R E QLJ ^ I'lC V , Hz

5000 10000

•*•

Hz dB Hz dB

125 30 800 43

160 29 1000 44

200 31 1250 45

250 32 1600 45

315 33 2000 45

400 33 2500 47

500 39 3150 49

630 41 4000 49

Figure 81. Average and range of sound transmission loss of triple

glazed sealed windows consisting of 2 panes 1/8-in thick mounted in

1 sash with an interpane spacing of 1/4-in and a metal spacer and with

the third pane consisting of 1/4-in glass mounted 1-2-in away in a separate sash.

231
10 ^

. sa Q T3 0 h

in 50 100 200 500 1000 2000

FREQUENCY, Hz

5000 10000

Hz dB Hz dB

125 28 800 47

160 34 1000 47

200 34 1250 48

250 36 1600 49

315 36 2000 50

400 40 2500 52

500 44 3150 52

630 45 4000 50

Figure 82. Average and range of sound transmission loss of triple

glazed sealed windows consisting of 1/8-in thick panes mounted in 2

wood sashes with a first interpane spacing of 1/4-in and a second

interpane spacing of 4-in.

232
SOUND

TRHNSMISSIOrJ

l_055,

dB 70

60

50

40

30

20

10

1 0

0

. CQ Q TS h

ID

Hz dB Hz dB

125 14 800 19

160 14 1000 20

200 16 1250 22

250 17 1600 22

315 18 2000 22

400 18 2500 22

500 18 3150 23

630 20 4000 24

Figure 83. Average and range of sound transmission loss of hollow

core wood doors with weather stripping.

233

DEV
SOUND

TRHNSMISSrON

LOSS.

dB

50 100 200 500 1000 2000

FREIQUEINCY, . 5000 10000

Hz dB Hz dB

125 21 800 26

160 23 1000 25

200 24 1250 26

250 26 1600 26

315 26 2000 27

400 27 2500 28

500 26 3150 28

630 27 4000 30

Figure 8^* Average and range of sound transmission loss of solid

core wood doors with weather stripping.

23A

DEV
SOUND

TWBNSMISSrON

LOSS.

d

B

Hz dB Hz dB

125 23

160 22

200 25

250 26

315 27

400 28

500 28

630 29

800 30

1000 31

1250 32

1600 32

2000 33

2500 35

3150 35

4000 36

Figure 85. Average and range of sound transmission loss of weather stripped and sealed solid core wood doors.

235

dB
SOUND

TNHN5MIS5ION

LOSS.

dB

Hz dB Hz dB

125 23 800 30

160 22 1000 30

200 24 1250 30

250 25 1600 30

315 25 2000 29

400 25 2500 28

500 28 3150 30

630 29 4000 31

Figure 86. Average and range of sound transmission loss of weather

stripped glass containing doors.

236

DEV
SOUND

TRRN5MI55ION

LOSS.',

dB

50 100 200 5B0 10B0 200B 5000 10000

P”RcIv<UENC_.Y, i—12.

Hz dB Hz dB

125 24 800 31

160 22 1000 31

200 26 1250 31

250 26 1600 26

315 27 2000 25

400 28 2500 33

500 29 3150 36

630 30 4000 38

Figure 87. Average and range of sound transmission loss of weather

stripped metal doors.

237

DEV
in 50 100 200 5B0 10B0 200B 5000 10000

FREIGUE.NCY, Hz.

Hz dB Hz dB

125 22 800 27

160 23 1000 26

200 24 1250 27

250 26 1600 28

315 26 2000 29

400 27 2500 30

500 26 3150 30

630 27 4000 32

Figure 88 » Average and range of sound transmission loss of weather

and sealed solid core wood doors with aluminum sealed storm

door fitted with a single glazed window.

238

©TD.

DEV
SOUND

TRRN5MI55ION

LOSS,

dB

0 - - ‘ ‘ ,__j -< 50 100 200 5S0 10B0 200B 5000 10000

FREQUENCY, Hz.

Hz dB Hz dB

125 36 800 49

160 38 1000 51

200 40 1250 52

250 43 1600 53

315 46 2000 53

400 47 2500 53

500 48 3150 52

630 49 4000 52

Figure 89. Average and range of sound transmission loss of acoustical

doors

.

239

Dev
I/) 50 100 200 500 1000 2000 5000 10000

FREIQUEINCY, Hir .

Hz dB Hz dB

125 13 800 16

160 13 1000 14

200 12 1250 14

250 12 1600 15

315 13 2000 15

400 14 2500 16

500 15 3150 17

630 15 4000 17

Figure 90. Average and range of sound transmission loss of pitched

wood frame domestic roof with sealed perimeter but without insulation

or ceiling.

240

DEV
Hz dB Hz dB

125 13 800 34

160 15 1000 36

200 17 1250 39

250 19 1600 40

315 22 2000 41

400 25 2500 43

500 28 3150 44

630 31 4000 43

Figure 91. Average and range of sound transmission loss of pitched

wood frame domestic roof with sealed perimeter and insulation between

roof joists but without ceiling.

241
>y

Q

. 01 Q "a H

D

Hz dB Hz dB

125 19 800 31

160 20 1000 32

200 22 1250 32

250 23 1600 35

315 25 2000 35

400 26 2500 37

500 28 3150 35

630 29 4000 33

Figure 92. Average and range of sound transmission loss of pitched

wood frame domestic roof with sealed perimeter and plaster ceiling but

without insulation.

242