AlllOD TT^TSt.

NATL INST OF STANDARDS & TECH R.I.C. IDE

A1 11 00992956

/NBS building science series TA435 .U58 V84;1978 C.I NBS-PUB-C 1974

Building Science Series 84

for Reducing Transportation Noise

in and Around Buildings

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

SEP 2 0 «78

Design Guide

For Reducing Transportation Noise

in and Around Buildings

David S. Pallett

Robert Wehrii ' Roger D. Kilmer

'

Thomas L. Quindry

National Bureau of Standards

Washington, D.C. 20234

'NBS Institute for Basic Standards

^NBS Institute for Applied Technology

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Arinbler, Director

"^2

Issued April 1978
Library of Congress Cataloging in Publication Data

United States. National Bureau of Standards. Design guide for reducing transportation noise in and around

buildings.

(National Bureau of Standards building science series; 84) Supt. of Docs, no.: C13.29/2:84.

1. Transportation noise. 2. Noise control. I. Pallett, David S.

II. Title. III. Series: United States. National Bureau of Standards.

Building science series; 84. TA435.U58 no. 84 [TD893.6.T7] 690'.021s [729] 76-58340

National Bureau of Standards Building Science Series 84

Nat. Bur. Stand. (U.S.), BIdg. Sci. Ser. 84, 176 pages (Apr. 1978)

CODEN: BSSNBV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1978

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $3.50

Stock No. 003-003-01687-0
iii ACKNOWLEDGMENTS

The authors of this design guide have re- ceived the interest and support of many in- dividuals affiliated with the National Bureau

of Standards. While the contributions of all these persons cannot be specified, the authors explicitly thank the following:

. . . William Allen, for promoting the preparation of a design guide by NBS, and

for sharing with us many thoughts derived from his extensive experience in noise control and architecture

Randall L. Lasky, for providing invalu- able insight into the communication

of acoustical concepts and information

to building designers

Daniel R. Flynn, for supporting the design guide concept and for valuable

editorial assistance in revisions of several drafts of this document

Kenneth DeCorte and John Holton,

for their careful editorial reviews of the manuscript.
TABLE OF CONTENTS

Page

ABSTRACT vi

1. How to Use this Design Guide 1

2. What You Need to Know Before You Begin to Design 7

3. How to Select Noise Criteria 13

4. How to Select a Point on Your Site for Estimating Transportation System Noise 23

5. How to Estimate Building Site Noise 29

1. Sound Propagation and Barriers 29

2. How to Estimate Highway Noise 45

3. How to Estimate Railway Noise 59

4. How to Estimate Aircraft Noise 78

5. Illustrative Example of How to Estimate Building Site Noise 87

6. How to Make An Analysis of Outdoor Activity Areas and Indoor Sound 105

7. Design Alternatives 125

APPENDIX A SIR Data for Building Shell Members 135

APPENDIX B Technical Basis of the SIR Method 147

APPENDIX C Sample Worksheets 159
Conversion Table to SI Units

This publication uses customary English units for the convenience of engineers and

others who use them habitually. The table below is for the reader interested in conversion to SI units. For additional information see:

(1) NBS LC1078, Dec, 1976, "The Metric System of Measurement".

(2) Z210.1-1976, "ASTM/IEEE Standard Metric Practice".

Quantity To convert from To Multiply by

Length inch m (meter) 2.540 X 10-2

X .... X foot m 3.048 X lO^

mi lp m1 1

1

1 .\J\J\J /\ 1 \J Area In^ 6.452 X 10

ft2 111 9 290 V 1 0-2 Volume ii-i3 in

H COO \y i n-5 \ .boy X T u

ft3 2 832 X 1 0-2 gallon 3.785 X 10-3 Temperature ° F ° C toc = (top-32)/1.8

T. difference At Op K ATk= Atop/ 1.8

Mass pound kg 4.536 X 10-1 ounce kg 2.835 X 10-2 Pressure psi Pa 6.895 X 10^

in H2O Pa 2.488 X 102

in Hg Pa 3.386 X 10^

mmHg Pa 1.333 X 102

Energy Btu J 1.055 X 10^

MBtu J 1.055 X 105

kWh J 3.600 X 10^

ft • Ibf J 1.356 X 10°

kilocalorie J 4.187 X 10^

Power Btu/h W 2.931 X 10-1 hp W 7.457 X 102

Flow gal/min m^/s 6.309 X 10-^

ft^/min m^/s 4.719 X 10-^ Density Ib/ft3 kg/m^ 1.602 X 101 lb/gal kg/m^ 1.198 X 102

Heat Capacity Btu/(lb • ° F) J/(kg • K) 4.187 X 10^

Btu/(ft3' ° F) J/(m3- K) 6.707 X 10^
vi ABSTRACT

This design guide presents a unified procedure for the selection of noise criteria in and around buildings, for the prediction of exterior and interior noise levels arising as

a consequence of transportation systems

operations, and for the evaluation of the

adequacy of building designs with regard

to environmental noise. Noise criterion levels are suggested in terms of equivalent

sound levels (Leq). Simplified predictive

methods enable the estimation of noise

levels arising as a consequence of highway, railway, and aircraft operations. The

sound isolation provided by the building

shell is estimated by means of a new

single-figure rating system. Finally, design

manipulations which may make possible

the improvement of the acoustic conditions

in and around buildings are suggested.

Key words: Acoustics; architectural acoustics; building acoustics; environmental noise;

noise; noise control; sound; transportation

system noise.
1 Chapter 1 How to Use This Design Guide

Sound surrounds us everywhere—the song

of a meadowlark, the laughter of children,

and the rustle of autumn leaves. Unfortunately, the march of technology and the

trend toward higher living densities have

meant that these desired sounds of birds,

children, and nature are often masked by

the roar of automobiles, trucks, locomotives, and airplanes. The purpose of this design guide is to quantitatively estimate

the magnitude of noise, or unwanted sound,

at a building site in order to choose the

most appropriate building occupancy for that site, or to design features into new or

existing buildings that will reduce or control noise.

In the design of new buildings, architects,

builders, designers, developers, and engi- neers make decisions which affect future acoustic conditions in and around the

buildings. When the decisions are wrong,

acoustic comfort may be lost causing build- ing occupants annoyance and stress. Such

discomfort can often be averted by changes

in the building's location or orientation or

in its construction materials and workmanship.

In dealing with noise problems, the material in this guide can be used ... to solve

simple problems due to noise from highways, railways, and aircraft, and ... to cast up a warning flag when a serious noise

problem is encountered. Seeing such a red

flag, the designer should seek the professional consultation of expert acousticians.

This noise design guide was written by

acousticians, architects, and psychologists

at the National Bureau of Standards working to a strict timetable, it was agreed at the outset of the project that the guide's

methods of calculation and the data supporting them would have to be drawn from

state-of-the-art materials. This has had the disadvantage of a loss of potential detail and precision, but the advantage of simplification, which the user of this guide will no doubt appreciate.

The guide has one salient advantage over most other guides in that it is quantitative,

offering you a method of calculating not

just how transportation noise affects your

building, but how much. Furthermore, the

guide is arranged in a sequence of chapters

which parallel your design sequence. The

guide is meant to accompany you as a

drafting board companion in a design voy- age as you depart from first concepts that are vague and tentative until you arrive at a finished building scheme that is robust,

rich in detail, and well-reasoned—especially

insofar as the analysis of transportation

system noise is concerned.

The design guide aims to get right to the

point in attacking your urgent noise problems in building or site design. Hence, it aims neither to nag you about fundamentals

of acoustics nor overburden you with esoteric details. If you need fundamentals, you

can get them from one of the many excellent textbooks available (the references

at the end of this chapter [1-22] include

references to the literature on general

acoustics [1-5], noise and vibration control

[6-10], basic acoustical measurements [11, 12], and acoustics and architectual design

[13-22]); if you want to penetrate the rele- vant details on acoustics (and we hope you

will) specific references are listed at the

end of each chapter.

What type of person should use this design

guide? We think it can be anyone who has

a technical background and a fundamental

knowledge of building design and construction. We refer to the guide's user as a

designer, but we think of this designer as any architect, builder, building designer,

contractor, developer, engineer, landscape

architect, or student who is faced with a

noise problem in building or site design.

If this shoe fits, welcome! You're the designer we're seeking to help.

Of course, as a designer you have a re- sponsibility, too, that of creating a scheme.

A building scheme is essential since this
design guide is based on analysis; and it cannot worl< without a schenne to analyze.

In designing your building or site scheme,

you will be juggling a myriad of design

variables: building codes, available financing, and costs; structural, enclosure, mechanical, electrical, and communications

systems; color, texture, massing, shape,

size, and arrangement; and not just acoustics, but also aesthetics, comfort, health,

privacy, safety, and security. Many of these

other design variables relate to or interface

with acoustics, but some will be in conflict. As a designer you must use judgment to make tradeoffs in achieving a happy

blend of needed features in your scheme.

We, of course, assist you only in noise

prediction and control. We think you will welcome this assistance.

Managing all these design variables is like herding frogs. Just as you approach one, it leaps away in an unexpected direction. Still, this guide is meant to do what it says

give you guidance about acoustics as you

design. To do so, the guide makes a number of assumptions about design, which

will now be discussed in conjunction with

the contents of the guide.

As it progresses, design is expressed as a

set of pictures describing a scheme. The

scheme is the conversation piece; that is, the focal point and basis of all communications about the building project. The designer, consulting engineer—all of these

get their heads together over the scheme

to assess it, evaluate it, revise it, or discard

it and start afresh. This design guide, too, requires a scheme against which you are

to examine noise conditions.

The scheme is customarily drawn to scale

in plan, elevation, section, perspective—as many two-dimensional drawings as are needed to visually explain the scheme as it will eventually be when built in three dimensions. The acoustics design guide analyses

may require small scale drawings in plan

(maps and site plans), and for some proj- ects drawings in section to illustrate, in a

vertical plane, the path of the sound as it moves from its source across the terrain (including barriers) to a building or other

"receiver." The design guide analysis will require large scale drawings to show the

general layout and details of the proposed

building sufficient for its calculations and

evaluations.

Before the scheme is started, design communications do not exist as pictures, but

mostly as words—the conversations of owner and designer, and the narrative of an architectural program. This may be just a few notes on a restaurant placemat or a

lengthy, formal exposition of the objectives,

scope, criteria, desired spaces, features,

and functions of the proposed project. An

ideal architectural program would contain

the full set of explicit constraints which

apply to the project. By constraint is meant

anything which limits the degrees of free- dom in the design. Constraints are not necessarily bad, only facts of life for a

designer. In truth, constraints are desirable

because they impose some limit, some re- striction on the number of possible schemes.

Since this number is infinite, the constraints can be a blessing, setting a boundary on

unfettered, hence intolerable, design free- dom.

Very few architectural programs approach

the ideal in containing all constraints—in- stead most constraints are implicitly held

in the designer's mind rather than explicitly

printed in the program.

Some constraints are physical; for example,

the configuration of the site and its sur- rounding environment, the characteristics

of sound, the changes of weather. For pur- poses of this design guide, physical constraints critical for acoustic calculations

develop from information which is to be

obtained as directed in the first part of the next chapter (Chapter 2).

Other constraints are man-made, or "artifi- cial", and are referred to here as rules. Rules include the provisions of building

codes, as well as standards, requirements,

and design criteria. Like other types of constraints, rules limit the number of possibilities in design; but rules also serve as

objectives, as a way of measuring a scheme

and evaluating it. If the rules are truly predictive of satisfactory buildings, then a scheme on paper which complies with the

rules should describe a future building that

will turn out to be satisfactory.

This design guide employs a noise criterion as the type of rule which is to govern your

acoustic design and evaluation. The term

"noise criterion" is used to denote a noise

(sound pressure) level to be used as a design goal for your building project. Chapter

3 tells you how to select noise criteria appropriate for your building and its outdoor

activity areas. The set of noise criteria you

select then serves as a target to achieve

for your building scheme. We hope that you

will not only be able to achieve the design
goal specified by the criteria you select, but even lower sound levels.

Earlier we mentioned physical constraints, the constraints arising from the physical nature of the site and from the physics of acoustic and other natural phenomena. As

a designer, you cannot deal, or interact,

with these physical constraints directly, just as you do not initially deal with a real building, only the scheme for a future

building. Hence, you must have a method

for modeling, for representing the site and

acoustic phenomena in the same language

of words, numbers, and pictures as you

use for your scheme. Chapter 5 explains

this concept, showing how you can quantitatively estimate the magnitude of sound

coming from such transportation sources as

highways, railways and aircraft, as it reaches your site or building.

Physical constraints and rules have been

discussed. There is still a third, and final, type of constraint, namely the scheme constraint, which is simply a constraint arising

from a decision that has been made about

your scheme. If you decide that your build- ing is to be a school, you have constrained

it against becoming a home, a hospital, or an office building. If you decide it is to be

built of brick, then you have constrained it against being built of concrete or cinder

block. As more and more design decisions

are made, the range of possibilities for your

scheme is constantly narrowed. The most

general of these scheme constraints are

usually made quite early in the design

process, and are uppermost in the architectural program, or problem statement. Such general scheme constraints are the type of building occupancy (commercial,

industrial, institutional, or residential, etc.), the overall capital budget and in turn the general size of the building, the general

level of quality for the building, the type of

fire construction, etc. Since these general

constraints are important to acoustical design, they must be stated (as set forth in Chapter 2) in advance of design.

As building design proceeds, decisions descend from the general to the particular,

and constrain more and more the eventual

outcome. In fact, design may be thought

of as a process of scheme constraint set- ting—a process which moves from diagrammatic drawings to detailed drawings; and

from abstractions like safety and security

to concrete representations of walls, floors, and roofs. As it moves along, design relies upon a variety of plan, section, elevation,

and perspective drawings to represent the

scheme in a way that it can be studied.

Through the visualization of the scheme,

the designer educates himself about the

future building, and is able, even if imperfectly, to imagine what the building will be

like and how it will operate when occupied.

A good deal of the designer's attention is drawn to the building shell, that skin of walls and openings, roofs, and exposed

floors which will separate the building from

its outdoor environment. Design may pro- ceed from the inside out, considering first the occupants, their needs and activities; then the rooms and spaces suitable for these activities; then the building shelkto

contain the rooms and spaces; and, finally,

the relationship of this shell to the site. Or

alternatively, design may proceed from the outside in, thinking first about the outdoor

environment, the forces of climate, and

relationships to neighboring buildings; then

concentrating upon the building shell; and

finally upon the building's rooms, occupants,

and functions.

To be realistic, the designer must surely

follow both routes, from the inside-out, and

from the outside-in. This two-way approach

is certainly needed for acoustical design,

and is a concept embodied in this design

guide. Inside-out design commences with the selection of an indoor noise criterion in Chapter 3, and then aims at the selection

of representative rooms for acoustic analysis in Chapter 6. Outside-in design com- mences with the gathering of physical site data in Chapter 2, and the estimation of

site noise from separate sources in Chapter 5. The sound from these various sources can be summed, and is that which is ex- pected to impinge upon the rooms for which noise is to be predicted in Chapter 6.

Of course, inside-out design decisions are entangled with outside-in decisions. For ex- ample, in Chapter 6, you will probably want

to limit your analyses, since they are timeconsuming, to a small number of rooms,

including only those critical rooms which

are fairly susceptible to noise and which

are exposed to the loudest sound conditions. But here you will be caught up in conflict—for if you design from the inside- out and identify your critical rooms early

on, you will no doubt begin immediately

to revise your scheme to fortify these rooms

rendering them no longer critical; likewise,

if you design from the outside-in, you will tend to sum transportation sounds at some

arbitrary point, or points, on your site where

you anticipate a critical room to appear in your scheme, but having identified the
potentially noisy points on the site, you will want to begin immediately to ameliorate

the noise level at those points. For example,

you might choose to let the proposed

building itself serve as a barrier, turning its back to the sources of sound, and locate rooms having special needs for quiet on the

protected side of the building. In this fashion, progress in both inside-out and outsidein design is constantly interrupted by re- visions in your scheme, and by the tendency

to reverse your design direction.

Designers manage such mutually entangled

decision chains through iterations of a scheme simply by working first from the

outside-in and then from the inside-out.

Moreover, designers can generate alternative schemes which appear promising, and

then compare the various schemes. By pro- viding a method of analysis applicable for nearly any scheme, this design guide aids

in such comparisons. Time spent in scheme

generation, analysis, and comparisons will be rewarded with increasing insight into your building's noise conditions and their solution. Chapter 7 contains some explicit

and much implicit advice to aid you in generating design alternatives.

Designing either from the inside out or from

the outside in, you arrive inevitably at the

building shell, your main line of defense

against transportation noise. The room-by- room calculations of Chapter 6 are essentially calculations of the sound isolation afforded such rooms by that portion of the

shell which constitutes the exterior faces of the rooms. To make these calculations, you

will rely upon single-figure ratings for vari- ous types of exterior walls and wall openings, roofs, and exposed floors. A special

single-figure shell isolation rating (SIR) sys- tem was devised for this purpose, and

Chapter 6 describes the procedures for implementing this system. Appendix A pre- sents SIRs for a variety of building shell materials and constructions.

In summary, this design guide is intended

to aid you in making acoustic decisions for a building problem which confronts you. The guide's chapters are arranged in a sequence compatible with the overall design process for buildings. If you are using

the guide for the first time or need to re- fresh your memory on its use, you will want to study the general discussion which

is contained in this chapter. Then you

will collect background information about

your project site and make the early decisions about your building scheme called for

in Chapter 2. Then, formulate noise criteria for the types of building occupancies or room functions you have in mind as described in Chapter 3. Then using the strate- gies described in Chapter 4, you will select a point or points on your site for estimating

sound levels. Chapter 5 will then assist

you in estimating the sound coming to your

site from highway, railway and aircraft sources. For the first two sources. Chapter

5 will also show you how to estimate the attenuation of sound as it crosses various

types of barriers. If your site or building is exposed to more than one source of sound,

the contributions of these various sources can be summed as described early in Chapter 6.

By this time, it is presumed, you will have

completed a schematic design for your

building which can be analyzed for its noise

transmission properties and interior noise

levels by means of the strategies and methods of Chapter 6. The analysis is made on

a room-by-room basis.

If the room sound levels are greater than

the noise criteria you formulated in Chapter

3, you will want to revise your scheme. If the noise criteria are not met in just a few

rooms, you may wish to make detailed

scheme adjustments for only those rooms

affected. If your scheme's noise troubles are more general, however, you will look for more extensive changes in your scheme. In either case, you will be helped by the suggestions in Chapter 7.

In this guide, interior noise sources are not

estimated. Because of the great diversity of sources, including heating, cooling, and

ventilating systems; office equipment; conversation; etc., such estimates would be

cumbersome. Instead, interior sources are accounted for by assuming they contribute

to the sound coming from exterior trans- portation sources. If you want more precise

estimates, you should refer to the public

texts on noise and vibration control, and on

acoustics and architectural design listed at the end of this chapter, (also reference [22]); or you should obtain the services of an

acoustical consultant.

This design guide has its main emphasis

upon problems of transportation noise in the design of new buildings, since this is a common noise problem. It is also a complicated problem because there are many

unknowns in building schemes during their formative stages. The design problem can

be stated thus: given an architectural pro- gram and a scheme for a proposed build-
ing, predict acoustical conditions in the rooms of ttie building, or in the outdoor

activity areas of the building, and bring all spaces to pre-established noise criterion

levels.

The guide can be helpful in other types of problems as well; problems like those listed below:

Site Selection: given a desired building

occupancy, such as a school or apartment

building, select a site which will have

acoustic conditions within specified noise

criteria. Analysis of a Building Site: given a site, analyze its acoustic conditions, or the conditions to be expected in a proposed

building of a selected type of occupancy.

Environmental Impact Statements: given a proposed building scheme, predict the impact of transportation noise upon the rooms of the building.

Building Re-design: given a completed building, improve the acoustic conditions of

its rooms or outdoor activity areas to satisfy noise criteria.

In using the guide to address such additional problems as the ones listed above,

you will select among the offerings of its various chapters. This should be easy to do once you have familiarized yourself

with the guide in connection with problems

of building design.

General Acoustics

[1] Beranek, L. L., Acoustics (McGraw-Hill

Book Company, Inc., New York, New

York, 1954).

[2] Ford, R. D., Introduction to Acoustics

(Elsevier Publishing Company, Ltd., Barking, Essex, England, 1970).

[3] Kinsler, L. E., and Frey, A. R., Fundamentals of Acoustics (John Wiley and

Sons, Inc., New York, New York, 2nd

ed., 1962).

[4] Morse, P. M., Vibration and Sound

(McGraw-Hill Book Company, Inc., New

York, New York, 1948).

[5] Smith, B. J., Acoustics (Longmans

Group Ltd., London, England, 1971).

Noise and Vibration Control

[6] Beranek, L. L., Noise and Vibration

Control (McGraw-Hill Book Company,

Inc., New York, New York, 1971).

[7] Harris, C. M. (ed.), Handbook of Noise

Control (McGraw-Hill Book Company,

Inc., New York, New York, 1957).

[8] Lyon, R. H., Lectures in Transportation

Noise (Grozier Publishing, Cambridge,

Massachusetts, 1973).

[9] Taylor, R., Noise (Penguin Books Ltd., Harmondsworth, Middlesex, England,

1970).

[10] Yerges, L. F., Sound, Noise and Vibration Control (Van Nostrand Reinhold

Company, New York, New York, 1969).

Basic Acoustical Measurements

[11] Brock, J. T., Acoustic Noise Measurements (Bruel and Kjaer, Denmark, 2d

ed., 1971).

[12] Peterson, A. P. G., and Gross, E. E., Jr., Handbook of Noise Measurement (General Radio Company, Concord, Massachusetts, 7th ed., 1972).

Acoustics and Architectural Design

[13] Beranek, L. L., Music, Acoustics and

Architecture (John Wiley and Sons,

Inc., New York, New York, 1962).

[14] Day, B. F., Ford, R. D., and Lord, P., (eds.). Building Acoustics (Elsevier

Publishing Company, Ltd., Barking,

Essex, England, 1969).

[15] Doelle, L. L., Acoustics in Architectural

Design (Division of Building Research,

National Research Council, Ottawa,

Canada, 1965).

[16] Doelle, L. L., Environmental Acoustics

(McGraw-Hill Book Company, New

York, New York, 1972).

[17] Egan, M. D., Concepts in Architectural

Acoustics (McGraw-Hill Book Company, Inc., New York, New York, 1972).

[18] Knudsen, V. O., and Harris, C. M., Acoustical Designing in Architecture

(John Wiley and Sons, Inc., New York,

New York, 1950).

[19] Lawrence, A., Architectural Acoustics

(Elsevier Publishing Company, Ltd., Barking, Essex, England, 1970).

[20] Parkin, P. H., and Humphreys, H. R., Acoustics, Noise and Buildings (Faber

and Faber Ltd., London, England, 1958).

[21] Rettinger, M., Acoustic Design and

Noise Control (Chemical Publishing

Co., Inc., New York, New York, 1973).

[22] Berendt, R. D., Winzer, G. E., and Burroughs, C. B., A Guide to Airborne,

Impact, and Structureborne Noise Control in Multifamily Dwellings, U.S. De- partment of Housing and Urban Development Report No. HUD-TS-24 (National Bureau of Standards, Washington, D.C., September 1967).
6
7 Chapter 2

What You Need to Know Before

You Begin to Design

Chapter 1 described the general philosophy

and structure of this design guide and how

it can be used to solve building design

problems resulting fronn transportation sys- tem noise. Here in Chapter 2, we will specify

the information you will need to address

these problems. Much of the information

you gather for transportation system noise

analysis will also be essential for other design purposes.

In addition to data collection, Chapter 2 has a second goal; namely, to identify the procedure to estimate the severity of the noise problem at your site and proposed

building. If you have a dire problem beyond

the reach of this guide, you should get

assistance from an expert acoustician. If it appears that you have no potential problem,

desist . . . your time will be better spent in other spheres. But, if your problem lies within these two extremes, carry on, this design guide can be of help to you.

Direct measurements of noise and the

equipment for making these measurements

are expensive. This guide calls for making

estimates of the sound level of transportation noise from statistics such as counts of aircraft flyovers, highway traffic, and railway passbys, and does not require or rely

upon direct measurements of noise levels.

If a designer has the required measurement

equipment and the expertise to operate the

equipment, he is also likely to have access

to good ways of quantitatively estimating

and predicting acoustic conditions, and per- haps these ways are more detailed than

those found in this guide.

You should realize that the scope of this design guide has been deliberately re- stricted to exclude some potentially serious

noise problems. Your attention is principally

directed toward consideration of highway,

railway (including rail rapid transit) and air- craft noise. However, it is not possible to include detailed consideration of complicated highway intersections (including such

factors as stoplights or severe grades), rail- road yard operations, or airport operation

noise problems due to airports located

closer to your site than the distances listed

in Table 2-1.* These problems are too complex to be solved by this design guide.

* In order to make the results more immediately

useful to American architects and designers, cus- tomary engineering units are used rather than the (metric) International System of Units (SI) nor- mally used in NBS publications.

Table 2-1. Minimum Distances between Airports and Building Sites [1,2].*

International Airport ** Commercial or

Military Airport

General

Airport

Aviation

Distance Distance Distance Distance Distance Distance

to Side to End to Side to End to Side to End

of Runway of Runway of Runway of Runway of Runway of Runway

3000 feet 4 miles 2000 feet 2V2 miles 1000 feet 1 mile

* // your building or site Is within the distances of Table 2-1, you will have noise problems beyond the scope of this design guide, and you should secure the services of an expert acoustician. " Airports are classified as International, Commercial or Military, and General Aviation according to the

effective number of let aircraft operations (takeoffs and landings) daily [NJeft]. To account tor the extra annoyance of nighttime operations, their number is multiplied by seventeen when added to the number

of daytime operations. Hence, NJeff —17 NJnight -|- NJday. For International Airports, NJeff is greater than 1300. For Commercial or Military Airports, NJeff is between 501 and 1300. For General Aviation Airports, NJeff is less than 500.
Similarly, consideration of noise problems

due to fixed or temporary noise sources such as noisy industrial plants, or highway

or building construction is beyond the scope

of this design guide because of the diverse

range of potential problems.

Two classes of information will be needed:

(1) information about the building site and

the surrounding area and information about

the operational characteristics of the vari- ous transportation systems (information

which we have referred to as physical constraints); and (2) information about the pro- posed building (information we have called scheme constraints).

Building site data consist of geographical

and topographical information about the site and the lands adjacent to the site. The in- formation should be sufficient to prepare a noise source map of the area to scale, and

to cut vertical sections through this map in order to show transportation noise sources

in relationship to the surrounding terrain (including any man-made structures) and

your proposed building. Of special interest are any barriers (natural or man-made), in- tervening rows of buildings, or extensive

growths of vegetation which might divert,

reflect, or absorb a portion of the sound

before it reaches your site and building.

Usually, the noise source map can be drawn

from city, county, highway and other maps

which are inexpensive and easy to obtain.

The third (vertical) dimension is lacking in many of these maps but can be determined

from topographical maps issued by the Coast and Geodetic Survey. If these maps

do not provide the information needed,

you may have to run surveys with a hand

level or a transit. But before you perform

these surveys be sure to exhaust all ave- nues of existing information such as: city,

county, and regional planning commissions;

public utility companies for electric power,

natural gas, sewer and water, or telephone

services; city, county, and state departments

of streets, roads and highways; irrigation

and weed and pest control districts; port

authorities; departments of building regulation; city, county, or state engineers or sur- veyors; and, the Bureau of Reclamation,

National Park Service, or Army Corps of Engineers. These agencies may not have

the information you need, or may not be

able to release it; but if they do have it and can release it, your job will be lessened.

The main purposes of the noise source map

are to identify the locations of all potential

transportation system noise sources, and to

determine which areas on your site have

the lowest noise levels resulting from these

transportation systems. Ideally, the noise source map might contain sound contours

of equal noise level covering the entire site. This could aid in the identification and

selection of a preferred building location. But the development of such a contour map is difficult and is likely to be beyond

your resources. Another factor is that this technique of selecting a preferred building

location requires that your site be large

enough to permit relocating the building.

This is not always possible and, thus, special design strategies, as outlined in this guide, are needed.

In addition to the geographical and topographical information discussed above,

there is also a need for information about

the transportation system operational characteristics. The specific information that is needed depends on the type of transportation system being analyzed. The complete

list of required data are given in Chapter 5, which should be reviewed thoroughly before

you attempt to acquire the necessary in- formation. The possible sources of this information are discussed below.

For information on highways, you should

contact the city or county director of traffic;

city, county or state department of streets, roads and highways (or department of transportation); or the city, county, or state engineer. Federal agencies such as the Department of Transportation, Federal Highway

Administration, or Highway Research Board

may also be able to provide the needed

information.

For information on railways you should

contact the supervisor of customer rela- tions for the railway. The city, county, or

state department of transportation may also

be of some help, as well as the city, county

or state engineer. The Association of Ameri- can Railroads may be able to put you in touch with the relevant offices or agencies.

Information on airports can be obtained

from the Federal Aviation Administration

(FAA) area office for commercial airports, or from the Military Agency in charge for

military airports. You might also contact

the FAA District Office, (or airport operator), or the airport manager to get the re- quired information.

Keep in mind that transportation systems

can change dramatically with time. Also,

land use patterns are not fixed, but vary over

the years. For example, the future abandon-
ment of a nearby airport or railway line could erase a presently crucial noise problem. Likewise, higliway noise could be alle- viated by tile development of quieter tires or more silent engines. On the other hand,

noise conditions could eventually worsen

because of increased traffic on existing free- ways or the construction of new highways.

Naturally, you should try to anticipate future changes. In making your predictions, you

can consult the data; review the plans and

projections; and seek the assistance of departments of streets and roads, highway

departments, planning agencies, railway

companies, and the like. We have thus delineated some of the re- quired physical data on the site and neighboring land, and sources of information on

transportation system operational characteristics. Now let us review the second main

class of needed information; information

about your proposed building which is necessary for interior noise level calculations. We have referred to this type of in- formation as scheme constraints, and have

indicated that only the most general scheme

constraints must be spelled out here.

Scheme constraints needed are: the type

of building occupancy—be it commercial,

educational, industrial, institutional, or resi- dential, etc.; the building size in terms of

floor area, or in terms of beds for general

hospitals, classrooms for schools, etc.; the

overall building budget, which together with

the proposed building size, will yield some

notion about building quality; the general

type of construction, whether heavily fire- resistant or not, and the general type of construction material, whether heavy or lightweight. Knowing these scheme constraints

is essential for anticipating the typical room

size, amount of exterior shell exposure, and

typical room furnishings, whether sound absorptive or not, for the room-by-room calculations of Chapter 6. Knowing the general

degree of building quality and workmanship

is also needed for estimates of room sound

levels. Finally, the type of occupancy for the building as a whole and the functions

of special rooms within the building are scheme constraints needed for selecting

noise criteria in Chapter 3. The decision

about these noise criteria is especially criti- cal to the people who will occupy the building, people whom you will want to satisfy

in terms of acoustic comfort.

As you come face to face with the problem

of satisfying these future occupants, keep

in mind that in recent times their peace and

comfort have been increasingly intruded

upon by loud noises. They are constantly

bombarded by noise from all kinds of sources — namely, automobiles, trucks,

trains, airplanes, but also construction machinery and industrial equipment, to name

just a few. Regretably, the only refuge they

may have from these disruptive noises is inside their homes and offices. Thus, it is no wonder that people become upset and

dissatisfied when they are disturbed even

there.

Of course, the best answer would be to reduce noise at its source. But this option

Is frequently not one over which the designer has control. Therefore, the designer

must concentrate upon minimizing the effect

of noise at the "receiver", namely inside

homes, offices, churches, schools, etc. To

effectively isolate people from these noises

the designer needs to know beforehand the

characteristics of the noise source. For many types of sources this information is either not available or would be too voluminous, therefore difficult and expensive to gather.

Construction noise and industrial noise are two such cases. Estimation and prediction

of the noise from these sources is difficult because there are many different equipment types and functions to be described.

That these sources operate intermittently on a variable time schedule only further complicates the problem, and requires

elaborate measurements of the sound pro- duced.

This is not the case for highway, railway

and aircraft noise. Although there obviously

are different types of autos, trucks, trains,

and airplanes, in general, many of these

vehicles operate in the same manner, per- forming the same function. This allows certain assumptions to be made about how

the noise is generated, which in turn makes

it possible for you to predict the noise levels produced by each type of vehicle. This is the basis for the predictive methods described in Chapter 5. We may be able to spare you the trouble

of performing these complete calculations.

We mentioned earlier in this chapter that two situations would make these calculations unnecessary or inappropriate. The

first situation is a building site having severe

noise problems, which would direct you

toward the services of an expert noise control engineer or acoustical consultant; the second situation, the one to be discussed

next, is a building site which probably has no severe noise problem whatever. Let's examine this possibility now.
Table 2-2 provides a list of minimum dis- tances which you can use as rules of thumb

for eliminating transportation system sound

sources as matters of concern. The values

in Table 2-2 are the distances necessary

for the noise generated by "typical" highway and railway operations to decrease to an A-weighted day-night sound level of 55

dB (these units are explained more fully

in Chapter 3) at the exterior of the building

under consideration. As is indicated in Chapter 3, this corresponds to the noise

level in a typical suburban neighborhood,

and is not generally regarded as excessive

noise. In Table 2-2, the decrease of sound

level with distance is assumed to be a function only of geometrical spreading, or diver- gence, and does not include decreases due

to barriers or other forms of shielding which

would further reduce the sound levels and

render Table 2-2 values more conservative.

The values in Table 2-2 for airports are the distances required for the noise generated

by "typical" aircraft operations to decrease

to a sound level that is "clearly acceptable."

This is based on the information given in reference [1], which evaluates a building

site as "clearly acceptable" if the "noise

exposure is such that both the indoor and

outdoor environments are pleasant."

If your site or building is located at dis- tances greater than those shown in Table

2-2, the probability is low that noise would

exceed an A-weighted day-night sound level of 55 dB. Thus, there would be no need

to perform the predictive computations of

this design guide. This, of course, is contingent upon whether or not your situation

is truly "typical." For example, these refer- ence distances would not apply where there are extremely high vehicular traffic volumes —more than 10,000 automobiles per hour, or more than 300 trucks per hour.

On the other hand, if your building site is closer than the distances specified in Table

2-2 to one or more of the three transportation systems noise sources, the noise levels

for your building should be determined by

the predictive methods of Chapter 5.

The use of Table 2-2 is an informal procedure, which may not be adequate for your

needs. Thus, a more formal procedure for the preliminary elimination of non-intrusive

noise sources from further consideration is outlined in the following steps. Complete

these steps using the Preliminary Source

Evaluation Worksheet shown in Figure 2-1.

Instructions for the Use of the Preliminary

Source Evaluation Worksheet

STEP 1 INPUT DATA

You must first determine the distances

from all major highways, railway lines,

and airports to the building site or pro- posed building location. For aid in selecting the most appropriate building location on your site, refer to Chapter 4. Distances can be obtained from area maps. For highways and railways, the distance

should be measured along the shortest

perpendicular line from the centerline of

Table 2-2. Distance Criteria for Elimination of Non-intrusive Transportation System Noise

Sources [1].

Noise There is a possibility of excessive noise due to this Source source if the building site is:

Highway within 1000 feet of any major roadway *

Railroad within 3000 feet of any railway line

Aircraft within the distances given below;

1. International

Airport**

2. Commercial

or Military

Airport**

3. General Aviation

Airport**

Distance Distance Distance Distance Distance Distance

to Side of to End of to Side of to End of to Side of to End of Runway Runway Runway Runway Runway Runway

3V2 miles 16 miles 2V2 miles 91/2 miles 1 mile 5 miles

* A major roadway is one with traffic of more tfian 50 autos per hour or more than 5 trucks per hour.

** See the footnotes of Table 2-1 for definitions for the three types of airports.
PRELIMINARY SOURCE EVALUATION WORKSHEET

1 2 3 4

Noise Building- Might there If the answer If the answer

Sourrp WW LI1 rpp 1 ic nn in ^11 lo 1 lU III dl 1 io yco lur una

Distance noise? (yes cases, or more of the

or no) [See for highways, sources, Table 2-2] railways, or

airports *

Highway #1 feet umit oeciion Obtain the data

of Chapter 5 and perform the #2 feet C/Ornpuiaiions UUUIIIcU III OcO. #3 feet 2 of Chapter 5

for each high-

#4 feet way with a yes

answer.

Railway #1 feet Omit Section 3 Obtain the data

of Chapter 5 and perform the

foot pnmni itpfinnQ

outlined in Sec. #3 feet 3 of Chapter 5

for each railway

#4 feet with a yes answer.

Airport #1 miles Omit Section 4 Obtain the data

of Chapter 5 and perform the

m i Igs romnutation*?

outlined in Sec. #3 miles 4 of Chapter 5

for each airport

#4 miles with a yes answer.

* // the answer is no for all three types of transportation system noise source, this design guide evaluation is not necessary.

Figure 2-1. Preliminary Source Evaluation Worksheet.

the highway or railway to the building or

site; and, for airports from the nearest runway. Also to accurately estimate the

noise generated by aircraft, you should

determine if the building is to be near

the side of a runway or in line with the

end of a runway. Moreover, you should

classify the airport in one of three cate- gories [2]:

1. International Airport or airport serving a greater metropolitan area

2. Airport serving commercial carriers or military airport

3. General Aviation—propeller aircraft Record this information on the worksheet

which provides spaces for as many as

four highways, four railways, and four air- ports for your building site. Distances

should be in feet except for airport data,

which should be in miles.

Using the distances of Table 2-2 as refer- ences, determine if any of the sources may possibly generate excessive noise

at the building site. To determine the

appropriate distance to use as a refer- ence for the airport noise estimation,

look in Table 2-2 under the airport cate- gory and then choose the distance corre- sponding to the building location, to the

side of the runway or in line with the end of the runway. Record the results in Column 2 as either yes or no answers. Then, depending upon the answer in Column 2, proceed to either Column 3

(a no answer) or Column 4 (a yes answer).

If any highway (or other type of source)

has a yes answer, the noise prediction

computations should be performed for each such source.

STEP 2 NOISE SOURCE EVALUATION

Now you can evaluate each of the sources

listed in Column 1 of the worksheet.

A word of warning should be given here.

All of the reference distances listed in Table 2-2 are approximate. You must exer-
12

cise some judgment in deciding which

potential noise sources can be neglected

and which ones can't. Unfortunately, this

will be difficult until you gain some experi- ence in making these decisions. In general,

it is always a good idea to analyze any

source about which you are uncertain. That

way there will be little chance of omitting a source which could generate excessive

noise at the building site.

Clearly, there are many noise problems that require the expert advice of an acoustical

consultant or noise control engineer.

Although this guide equips you to make

quantitative estimates of noise levels, and

suggests design alternatives to ameliorate

difficult design problems, you would be

wise to obtain the services of a consultant

in the following circumstances:

(a) If your building occupancy is one that requires unusually low noise criteria

(for example, a recording studio or

library), and the anticipated site noise

levels are expected to be high due to the immediate proximity of an airport,

industrial plant, etc. Here, your building's construction will have to be

unusual, incorporating special noise

control provisions.

(b) If the procedures of this design guide

yield estimates of interior noise well

in excess (15-20 dB) of the noise

criteria, your building design should

be changed. It may be best to do this with the assistance of a consultant.

(c) If your building site falls into the

"clearly unacceptable" category as defined by Schultz and McMahon in "Noise Assessment Guidelines" [1], you should obtain the services of a consultant to consider the advisibility of construction on or rejection of the

site, or of the special adaptations

which may be required. Schultz and

McMahon define "clearly unacceptable" as ... a noise exposure at the

site so severe that the construction

costs to make the indoor environment

acceptable would be prohibitive and

the outdoor environment would still be

intolerable.

References:

Chapter 2

Information

Collection

[1] Schultz, T. J., and McMahon, N. M., Noise Assessment Guidelines, U.S. Department of Housing and Urban Development Report No. TE/NA 171 (Bolt

Beranek and Newman, Inc., Cambridge,

Massachusetts, August 1971).

[2] Jensen, P., and Sweitzer, G., How You

Can Soundproof Your Home, (Lexington

Publishing Co., Lexington, Massachusetts, 1974).
13 Chapter 3

How to Select Noise Criteria

From reading Chapter 2, you have determined whether or not your site or building

noise problem is one which can be analyzed

by using this design guide. This chapter

tells how to select noise criteria,* maximum

acceptable sound levels appropriate for your site and building occupancy, when the

origin of the sound is due to external trans- portation systems.

Once you have selected noise criteria . . . your design goals . . . you can proceed to estimate the amount of sound coming to your site from highway, railway, and air- craft sources; reduce this estimate of the

amount of sound to account for the effects

of dense vegetation or other barriers (see

Chapter 5), and then make an initial noise

analysis for your building's interior and its outdoor activity areas. If the sound levels you estimate (in Chapter 6) are greater than

the noise criteria you have selected, you

will probably want to pursue implementation of suggested design alternatives (in Chapter 7) to bring estimated sound levels

to within selected noise criterion levels.

This chapter will offer two approaches to selecting noise criteria ... an approach

using the simplified Table 3-1, or an ap- proach using the more comprehensive Table

3-2. Before selecting the criteria, however,

you should study and understand the fol- lowing principles of sound, how it is measured, and how noise criteria can be based

upon sound measurements.

The response of your future building's occupants to noise depends upon the physical

characteristics of the noise, the acoustic

properties of the building, the activity in which occupants are engaged, and their

sensitivity to noise along with a complex

• In this design guide, the word criterion denotes

a noise (sound pressure) level which you, the designer, will select as a design target, or goal for your building project. The Environmental Protection Agency uses criteria in a different sense; namely as standards reflecting available knowl- edge as to the health and welfare effects of such

environmental pollutants as noise.

set of other psychological, physiological,

social, and cultural factors. Obviously, it is essential that you, the building designer,

make a number of simplifying assumptions

about noise and the human perception of noise, in order to deal with acoustic phe- nomena quantitatively. Using this guide, you

will be able to predict the sound conditions in and around your proposed building, and you will have some idea of the

degree to which your building's occupants

will be satisfied with its acoustic environ- ment.

Experts generally agree upon the definition

of noise as unwanted sound; and sound,

for our purposes, is a propagating pressure

disturbance in air. Many properties of this pressure disturbance can be described

quantitatively, but the most important properties are the magnitude, or amplitude, of the pressure changes about atmospheric

pressure; the time-variation of the pressure

changes (frequency); and the distribution

of sound energy across bands of frequency.

People can hear sound within the range of pressure amplitudes extending from approximately 20 ij.Pa (Micropascals) at the thres- hold of audibility to 20,000,000 ^^Pa at the

threshold of feeling. The lift-off noise of a Saturn rocket is about 20,000,000.000 ^Pa, an even greater pressure amplitude, well above the threshold of feeling. Because this

is an enormous range of magnitudes, and

because acousticians need to observe the

effects of small changes at both extremes,

they have eschewed a linear scale and

adopted a logarithmic scale (to the base

ten). This scale compresses a range of one

to a billion to a range of 0 to 9.

The numbers 0 to 9 represent relative quantities, and the quantity measured on such

a scale is referred to as a level. Scientists

and engineers usually work with energy

quantities that would be proportional to the square of the sound pressure rather than to the sound pressure itself. This pre- sents no difficulty, since the logarithm of a squared number is two times the logarithm
of the original number; therefore, instead

of a range of levels from 0 to 9, the range

runs from 0 to 18 for sound pressure

squared. The unit on this scale is called a

bel. The bel has been divided into 10

smaller units known as decibels, so that the range of sound pressures, from the

approximate threshold of hearing to Saturn

rocket noise, runs from 0 to 180 decibels.

Decibel scales thus provide a convenient

way to describe the large range of sound

pressures to which your building occupants

will be exposed. The sound pressure level (SPL) is defined as:

SPL = 20Iogio—

,

Pref where p is the magnitude of the amplitude

of the sound pressure (measured over some

appropriate averaging time), and p,^^ is a

reference pressure, taken as 20 ^Pa. The

units of SPL are decibels, abbreviated dB.

The level near the threshold of audibility is 0 dB, and at the threshold of feeling is approximately 120 dB.

The logarithmic decibel scale is extremely

useful; however, it can be puzzling. On a

linear scale, the total sound pressure due

to two identical noise sources would be

twice that of one of the sources operating

alone. However on a logarithmic scale, the

total sound pressure level resulting from

two identical noise sources is 3 dB higher

than the level produced by either source

alone. (If you double a number, its logarithm

will always increase by 0.3; hence, 0.3 bels, or 3 decibels). Also, if two sound sources whose levels differ by more than 10 dB

are added together, the resultant level will be less than 0.5 dB higher than the level produced by the greater source operating

alone.

The above paragraphs have concentrated

upon sound magnitude, or amplitude; but as mentioned earlier, subjective responses

to noise are also based upon frequency.

The frequency range of hearing extends

from approximately 20 hertz to 20,000 hertz. The unit hertz, abbreviated Hz, has been

adopted to avoid possible confusion between the previously used term "cycles per second" and other "cycles" of machinery

or natural phenomena. The 20 to 20,000 Hz

range is referred to as the audio region as

distinguished from the infrasonic range (20

Hz and below) and the ultrasonic range

(20,000 Hz and above).

The perceived loudness of a sound depends

primarily upon sound pressure, but is also

influenced by frequency. Likewise, one's

subjective response of pitch is highly dependent upon frequency, but is also somewhat affected by sound pressure. Moreover,

sounds subjectively characterized as "low

pitched" have energy content principally in the low frequency range, and vice versa.

People are most sensitive to sounds in the mid-band or high frequencies. People

are less annoyed or distracted by sound

frequencies in the lower frequency ranges. To compensate for this, sound levels to be

used for noise criteria are customarily

weighted, as shown in Figure 3-1, to deemphasize the importance of low frequency

sound while emphasizing mid-band and high

frequency sound.

+ 5

0 — 5

COm -10 m

oS -15

1 UJ _20

O

S -25

OC

UlS -30 H

<^ -35

-40

-45

-50

Ill

1

1

20 50 100 200 500 1000 2000 5000 10,000 FREQUENCY-Hz

Figure 3-1. Frequency Response Curve

for A-weighting [1, 2, 3].

There are various weightings or "scales,"

but in this design guide, we will consider

only the one termed the "A-weighting" scale

(to distinguish it from others, e.g., B, C, D,

etc.). It has the advantage of standardization

both nationally [1] and internationally [2, 3] and is the most commonly accepted weighting scale. Special filters are built into sound

level meters so that they measure and indi- cate A-weighted sound levels.

Figure 3-2 illustrates the A-weighted levels

of sounds encountered in daily life [4]. The

range of A-weighted SPLs found in building

spaces varies from approximately 20 dB for studios for sound recording to 90 dB for
boiler rooms. Clearly, these two types of building room occupancies are highly specialized, and the range of SPLs for ordinary

occupancies extends from approximately 35

to 60 dB.

DECIBELS

50 HP Siren (100')

Jet Takeoff {200')

140

I 130

I 120

I

Cut Off Saw

Pneumatic Peen Hammer

Riveting Machine HQ Casting Shal<eout Area

I 100 Electric Furnace Area

I 90

I Pneumatic Drill (50') 80

I

Textile Weaving Plant q_ Boiler Room

Subway Train (20') , Printing Press Plant

Tabulating Room

Inside Sport Car (50 MPH)

Freigfit Train (100') Vacuum Cleaner (IC) ^0

Speecti (V) I Near Freeway (Auto Traflic) 60

I 50

1 40 Mm. Levels—Residential

I Areas In Chicago At Nigfit

Large Transformer (200')

Large Store Accounting Office

Private Business Office Light Traffic (100') Average Residence

Soft Whisper (5')

Threshold of Hearing Youths 1000 - 4000 Hz

30

I 20

I 10

I0

studio (Speech)

Studio for Sound Pictures

Figure 3-2. Typical A-weighted Sound

Pressure Levels [4].

Sounds vary over time. As an example of the variation of noise level with time, consider a train—its sound will increase as

the train approaches and then subside

as the train moves away. The maximum

sound pressure level as the train rushes

by would be much greater than the sound

pressure level measured as the train dis- appears in the distance. However, the variation in the train's sound level can be ac- counted for by averaging the sound energy

over the time of the train's passage, and

thereby determining an "equivalent" steady

sound level.

Moreover, since transportation sounds vary from hour to hour as traffic ebbs and flows,

another type of long term time averaging

is needed. It is based upon time periods

related to the intended time of building

occupancy, or use ... 1, 8, or 24 hours.

During such a long time period, a great

many trains could pass, and the sound

level meter indication would typically have

varied over an extremely wide range. This can be accounted for by obtaining measurements in terms of (A-weighted) equivalent sound pressure levels. Such equivalent

A-weighted sound pressure levels, then, are constant sound levels which, in a given

situation and over a given time period,

convey the same sound energy as the

actual, measured sound.

The nature of the averaging of sounds in equivalent sound levels is such that two

sounds, one of which contains twice as much energy but lasts only half as long as

the second, is characterized by the same

equivalent level; so is a third sound with four times as much energy but lasting only one fourth as long. Thus, equivalent sound

levels tend to average out sounds of very

high level but short duration. For example, an equivalent sound level of 60 dB over a twenty-four hour day would permit sound

pressure levels of 110 dB, but these would

be limited to a total duration of less than one second in the course of the twenty-four

hour period [4].

The concept of equivalent sound level was

used in United States Air Force studies of noise from aircraft as early as 1957 [4, 5], and was introduced in Germany in 1965 to evaluate the impact of aircraft noise upon

the neighbors of airports [6]. It was soon

recognized in Austria as appropriate for evaluating the impact of street traffic noise

in dwellings and schoolrooms [7, 8]. It is now the rating used in both East Germany

and West Germany standard guidelines for

city planning [9, 10], and it has been widely

accepted in Sweden for use in traffic noise

surveys [11, 12].

Our use of the equivalent A-weighted sound

level conforms to the policy of the Environmental Protection Agency which selected

it as the one consistent measurement scale

"based upon existing scientific and practiced experience and methodology" which

satisfies the following guidelines:

"1. The measure should be applicable to the evaluation of pervasive long-term noise

in various defined areas and under various

conditions over long periods of time.

2. The measure should correlate well with

known effects of the noise environment on

the individual and the public.

3. The measure should be simple, practical

and accurate. In principle, it should be

useful for planning as well as for enforcement or monitoring purposes.
4. The required measurement equipment,

with standardized characteristics, should be

commercially available.

5. The measure should be closely related

to existing methods currently in use.

6. The single measure of noise at a given

location should be predictable, within an

acceptable tolerance, from knowledge of the physical events producing the noise.

7. The measure should lend itself to small,

simple monitors which can be left un- attended in public areas for long periods

of time." [4]

Of course, the equivalent A-weighted sound

level is not v/ithout its deficiencies. Still, these deficiencies do not preclude the use

of this measurement scale based upon present knowledge until more is known about

the frequency-weighting and time-averaging

of acoustical data.

Four types of equivalent A-weighted sound

levels are suggested in this design guide as

noise criteria for various building types:

Leq(1),* the "one-hour" Leq for short-term

occupancies such as churches and

theatres,

Leq(8), the "eight-hour" Leq for offices and commercial buildings used during an 8-hour working day,

Leq(24), the "twenty-four hour" Leq for educational occupancies,* and,

Ldn, the day-night equivalent A-weighted

sound level, for residential occupancies.** Ldn, like the Leq(24), has a 24- hour averaging period, but in addition

has a built-in penalty for night-time

noise.

Examples of outdoor day-night equivalent

sound levels in various locations are shown

in Figure 3-3. Note in particular that a level of Ldn = 55 dB is characteristic of suburban locations, and that levels in excess

of this are characteristic of urban, noisy

urban, or city (major metropolis) noise

levels.

There are several, general ways in which

your building's occupants could be ad-

* Leq is pronounced in accordance with its three letters "L"-"e"-"q"; and Leq(1) is called the "one-hour"- "L"-"e"-"q".

** The use of Leq (24) for educational occupancies, as sug- gested by reference [3], was adopted in this design guide because it was felt that this was the most appropriate

metric for this type of building occupancy. Since schools

are often used in the early evening hours, Leq(8) would

not be appropriate because it would exclude the noise exposure during those hours. On the other hand, Ldn would

not be appropriate either, because imoosing a nighttime

penalty would be unnecessarily severe. Ideally, a measure

based on fourteen to sixteen hours would be best suited

for education occupancy. But since such a measure is .not customary, Leq(24) was chosen.

versely affected by noise ... it could cause

a loss of hearing, activity interference or annoyance, and possible consequent stress.

In this design guide, noise criteria are re- lated solely to annoyance or activity inter- ference. Hearing impairment is not considered herein since it only tends to occur

in factories and similar locations where very

loud noise is experienced over long periods

of time. Stress per se is not considered

herein since its causes are often multi- faceted and its effects difficult to diagnose.

In selecting noise criteria, then, you are aiming at noise levels that will not be so

high as to create annoyance, or to interfere with activities, particularly those requiring

verbal communication.

The total noise environment within a building originates from two principal sources

. . . indoor and outdoor. The procedures of

this design guide provide quantitative esti- mates only for that portion of the total interior noise due to transportation-systemrelated external sources. The procedures

do not include detailed calculations for the

possibly larger contribution of use-related

internal sources such as mechanical sys- tems and occupant activities, or to nontransportation system related exterior

sounds. However, the guide permits you to account for noise generated indoors by an

adjustment to your selected noise criteria. The explanation which follows provides the

underlying basis for such an adjustment.

When all interior sources have been totally

silenced, such as when the HVAC (heating,

ventilating, and air-conditioning) system

has been shut down, and when building

occupants are quiet or asleep, total indoor

noise environment may approach the levels due to the external sources. Under these

circumstances, the interior and exterior

sound pressure levels will differ by a constant amount; and if the exterior noise in- creases due to some change such as in- creased traffic volume, then the interior noise level will increase accordingly. The

exact amount of difference between interior and exterior noise levels would be related

to the building shell's noise isolation properties, the types of interior furnishings, the nature of the energy-frequency distribution

(or "spectrum") of the exterior noise, and

the degree to which windows are open or closed. Such factors as these are dealt with in Chapter 6 of this design guide.

Activity within the building presents a complication, however, since use-related and

mechanical equipment noise can vary

widely. Hence, there are no general rules
DAY-NIGHT

SOUND LEVEL

DECIBELS

QUALITATIVE

DESCRIPTIONS

City Noise (Downtown Major

Metropolis)

Very Noisy

Noisy Urban

—70-

Urban

Suburban

Small Town &

Quiet Suburban

—60-

OUTDOOR LOCATIONS

Los Angeles—3rd Floor Apartment Next To Freeway

Los Angeles

Vt Mile From Touch Dov/n At Major Airport

Los Angeles—Downtown Witli Some Construction Activity Harlem—2nd Floor Apartment

Boston—Row Housing On Major Avenue

Watts—8 Miles From Touch Down At Major Airport Newport—3.5 Miles From Takeoff At Small Airport Los Angeles—Old Residential Area

Fillmorfe —Small Town Cul-de-Sac San Diego— Wooded Residential

California—Tomato Field On Farm

—40—

Figure 3-3. Examples of Outdoor Day-Night Equivalent Sound Levels

Measured at Various Locations [4].

for estimating indoor, use-related noises.

Rather, if precise calculations are needed,

they ought to be performed by the mechanical systems engineer responsible for HVAC

systems or by acousticians knowledgeable

about potentially noisy equipment such as

office machinery or data processing equip- ment.

When indoor-generated sound levels are known, the rules for logarithmic addition are applicable for combining interior userelated noise and interior transportationsystem related noise (of exterior origin). For example, these rules are such that when

two equal components are combined, the

level corresponding to the total is 3 dB

larger than either individual component.

A number of recent publications issued by

the U.S. Environmental Protection Agency

summarize current knowledge regarding

human response to noise. Several of these

discuss equivalent sound levels in some

detail.

In the document "Information on Levels of Environmental Noise Requisite to Protect

Public Health and Welfare With an Adequate

Margin of Safety" (the "levels document")

levels are identified to protect public

health in a large number of situations [4].

Some of these levels are specifically sug- gested with the understanding that "health

and welfare" includes personal comfort and

well-being as well as the absence of noiserelated mental anguish and annoyance, or

activity interference. In particular, speech

interference was one important basis upon

which some of these levels were identified. The levels identified in the "levels document" for interior spaces correspond to overall equivalent sound levels in the building, regardless of whether the noise is due

to interior or exterior sources. Some means

is therefore needed to adjust the EPA

recommended levels to allow for interior noise sources.

In addition to complications introduced by

the variable acoustical properties of the

building shell and furnishings and by the

variability of internal use-related noise

sources, there is very little knowledge avail- able concerning the most satisfactory bal- ance between noises of interior and exterior

origin for specific building occupancies.

Under some circumstances, and particularly

when there is an adverse psychological re- action to noise of external origin, building

occupants may prefer that any noise of external origin be dominated and heavily

masked by internal noises, even at the cost

of a significantly increased overall noise
level. Under other circumstances, when the

noises of external origin are approximately

comparable to the use-related interior noises, there can be a subjective response

indicating a satisfactory balance. An acoustical consultant may be able to advise you

about systems which provide helpful masking sounds.

There are no data to justify a generally applicable statement of preference.

Lacking quantitative knowledge concerning

people's preference for any specific imbal- ance between two components of an overall noise level, we therefore postulate that the

two components are equal. This postulate

implies that each of the two components in- dividually be 3 dB less than the overall level.

In reference [4], a noise criterion of 45 dB

was suggested as the maximum total level above which activity interference and result- ant annoyance would be at risk. If this noise

criterion is adjusted downward by 3 dB to account for indoor-generated noise, it takes

the value 42 dB. An additional margin of conservatism would result in a level of 40

dB.

This value, Leq = 40 dB, is suggested as

the noise criterion for interior noise of exterior origin. The value of 40 dB is the value

which appears in Table 3-1.

Indoor-generated noises may be individually as much as 3 dB higher than noises of out- door origin with the outdoor noise at the

upper limiting level for the external contribution. For example, if your indoor noise

criterion is 45 dB, it will be satisfied if the

interior noise level due to external sources

is no greater than 40 dB, and the noises of internal origin are no greater than 43 dB.

The 3 dB difference reflects a barely per- ceptible difference in subjective loudness

to the two contributions.

There are numerous ways of satisfying any

suggested criterion level (such as 45 dB)

with differing combinations of indoor and

outdoor generated noise. For example, if the indoor component is essentially at the

limiting level, then the external origin component must be at least 10 dB less than

the limiting value.

If you anticipate especially adverse exterior

noise conditions, or building occupants

who are especially sensitive to noise, you

may wish to mask, or dominate, external noise by internal noises even at the cost

of a substantially increased overall noise

level. In other cases, you may wish to bring

internal noise to a level just equal to external noise, with the expectation that your building's occupants will perceive this as a satisfactory balance. However, such

design decisions as these are probably best

left to acoustical experts whom you should

consult.

Some recent laboratory studies have dealt with identification of the levels at which

various highway traffic noises start to inter- fere with the ability to relax and enjoy

listening to the spoken word [13]. In one

particular study the recommended indoor

noise level for intruding traffic noise for subjects listening to the spoken word was comparable to the value of 40 dB suggested in this design guide. Whereas the aforementioned study gives tentative support to this recommendation, additional research will be

needed for confirmation.

Based upon the above explanations, it is then recommended that you select noise

criteria from the simplified Table 3-1 whenever it is applicable.

Table 3-1. Noise Criteria for Simplified

Selection.

Area Level

Indoor Rooms

Residential areas, including hospitals Ldn ^ 40 dB

Areas with activities such as schools,

offices, conference

rooms, etc. Leq{24) ^ 40 dB

Outdoor Activity Areas

Residential areas for which quiet is a basis

for use, etc. Ldn ^ 55 dB

Areas in which people

spend limited amounts

of time such as school

yards, playgrounds,

etc. Leq(24) ^ 55 dB

If your building project is to house a highly

specialized occupancy, or if outdoor activity areas are to be an important element in your design, however, you may select your

noise criteria from Table 3-2 (which is a comprehensive listing of recommendations

of other authors [14-31]) or from a consideration of the maximum distances over which
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conversation is satisfactorily intelligible.

Many of the Table 3-2 recommended levels are A-weighted, but few are equivalent

sound pressure levels; however, the provisions presented here allow you to account

approximately for this difference. Moreover,

Table 3-2 levels are not accompanied by

any recommendations as to the acceptable

component of interior noise which may be

due to exterior sources.

If you do select from Table 3-2, be aware

of these four provisos:

(1) For most occupancies, a range of levels, rather than a single number, is suggested in Table 3-2. This reflects the

variability in the needs of building clients and occupants, as well as the fact that these levels pertain to data conventionally measured with sound level meters averaging over, at most, several

seconds. Since the typical time period over which the Leq measures are aver- aged is appreciably longer ... 1 to 24

hours . . . the levels obtained from a sound level meter will naturally fall in a range of values.

(2) The noise criteria you select should fall within the recommended ranges of Table

3-2. For buildings like theatres and

churches which have short-term occupancies, Leq(1) is suggested as the measure. For offices and commercial

buildings having an eight-hour workday

occupancy, the Leq(8) is suggested; for other nonresidential buildings, the

2 4 6 8 10 20 40 Communicating Distance, feet

Figure 3-4. Maximum Distances Outdoors

Over Which Conversation is Considered

to be Satisfactorily Intelligible in Steady

Noise [4].

Leq(24) is suggested; and, for all resi- dential buildings, the Ldn is suggested.

(3) All of the suggested criteria for acceptable interior sound levels should be

decreased by approximately 5 dB to account for sound generated inside the

building.

(4) Perhaps most importantly, the designer

must exercise judgment to account for the special needs of the building client,

occupants, and occupancy with regard

to the relevant noise sources and noise

criteria.

Obviously, Table 3-1 is simpler than Table

3-2, but circumstances may dictate that Table 3-2 be used. In order to develop the

ability to judge which option is appropriate,

you may wish to consider whether the two

approaches actually lead to widely disparate values. Note that a value of 45 dB for indoor rooms, as suggested by the EPA,

falls within the suggested range for many

building occupancies; and, that interior A-weighted noise levels due to external sources in the range 40-42 dB will usually

be acceptable.

For example, a mid-range total noise level of 40 dB for assembly halls is consistent

with the suggestions of Table 3-2. Therefore, 35 dB is the corresponding suggested

noise criterion level for indoor noises of external origin. Consistent with (2) above,

the appropriate metric for assembly halls

is Leq(1). This suggested noise criterion (Leq(1) ^ 35 dB) should next be adjusted

to the client's special requirements if they

appear to be unusual. Finally, most of the

Table 3-2 noise criteria for assembly halls recommend a range of approximately 10

dB. Thus, your Leq(1) noise criterion level should be chosen from the range 30 dB to 40 dB, depending upon your judgment and

the client's special requirements.

In selecting design criteria for outdoor

areas, the information in Figure 3-4 is a

useful supplement to Table 3-1. This figure

indicates that the recommended value of 55 dB will permit a relaxed conversation,

with 99% sentence intelligibility, at a dis- tance of up to about four feet.

This figure can be used to develop other

criteria for outdoor activity areas. For ex- ample, if you believe that relaxed conversations with 99% sentence intelligibility must

be possible at distances up to 20 feet, then

the appropriate criterion would be an equivalent level of 30 dB, clearly an unusual and

stringent criterion for outdoor activity areas.
[1] standard Specifications for Sound Level

IVleters, S1. 4-1971 (American National

Standards Institute, New York, 1971).

[2] Precision Sound Level Meters, lEC

Publication 179 (International Electro- technical Commission, Geneva, Switzerland, 1965).

[3] Recommendations for Sound Level

Meters, lEC Publication 123 (Inter- national Electrotechnical Commission,

Geneva, Switzerland, 1961).

[4] Anon., Information on levels of environmental noise requisite to protect public

health and welfare with an adequate

margin of safety, EPA Report No. 550/9-74-004 (U.S. Environmental Protection Agency, Washington, D.C., March 1974).

[5] Stevens, K. N., and Pietrasanta, A. C,

Procedures for estimating noise exposure and resulting community reactions

from air base operations, WADC Technical Note 57-10, (Wright-Air Development Center, Wright-Patterson Air Force Base, Ohio, 1957).

[6] Burck, W., Grutzmacher, M., Meister,

F. J., Muller, E. A., and Matschat, K., Fluglarm, Gutachten erstattet im Auftrag des Bundesministers fur Gesundheitswesen (Aircraft Noise: Expert

Recommendations Submitted under

Commission from the German Federal

Ministry for Public Health), Gottingen,

1965.

[7] Bruckmayer, F., and Lang, J., Storung

der Bevolkerung durch Verkehrslarm

(Disturbance of the Population by Traffic Noise) Oesterreichische IngenieurZeitschrift, 8, 302-306; 9, 338-344; and

10, 376-385 (1967).

[8] Bruckmayer, F., and Lang, J., Storung

durch Verkehrslarm in Unterrichstraume

(Disturbance Due to Traffic Noise in Schoolrooms), Oesterreichische Ingenieur-Zeitschrift, 11 (3), 73-77 (1968).

[9] Schallschutz: Begriffe (Noise Control:

Definitions), TGL 10 687, Blatt 1 (Draft), Deutsche Bauinformation, East Berlin,

November 1970.

[10] Mittelung zeitlich schwankender Schallpegel (Aquivalenter Dauerschallpegal)

(Evaluation of Fluctuating Sound Levels: The Equivalent Continuous Sound

Level), DIN 54 641, (Draft), Deutsche

Normen, Beuth-Vertrieb GmbH, Berlin

30, April 1971.

[11] Ingemansson, S., and Ljunggren, S., Bullerproblem vid trafikleder. Report

R20 (Statens institut for byggnadsforskning, Stockholm, Sweden, 1970).

[12] Ljunggren, S., A design guide for road

traffic noise. Document D (The National

Swedish Institute for Building Research,

Stockholm, Sweden, 1972).

[13] Rice, C. G., Sullivan, B. M„ Charles,

J. G., and Gordon, C. G., A laboratory

study of nuisance due to traffic noise

in a speech environment, J. Sound and

Vib. 37 (1), 87-96 (1974).

[14] Knudsen, E. O., and Harris, C. M., Acoustical Designing in Architecture

(John Wiley and Sons, Inc., New York,

N.Y., 1950).

[15] Beranek, L., Reynolds, J. L., and Wilson,

K. E., Apparatus and procedures for predicting ventilation system noise,

J. Acoust. Soc. Am. 25 (2) 313 (1953).

[16] Beranek, L., Revised criteria for noise

in buildings. Noise Control 3 (1) (1957).

[17] Lawrence, A., Acoustics in buildings,

Australian Building Science Series 1, 70 (1962).

[18] Kosten, C. W., and van Os., G. J., Community Reaction Criteria for External

Noises, National Physical Laboratory

Symposium No. 12, (National Physical

Laboratory, London 1962).

[19] ASHRAE: Guide and Data Book, Systems and Equipment, p. 379 (American

Society of Heating, Refrigerating and

Air Conditioning Engineers, New York,

N.Y., 1967).

[20] Denisov, E. I., New health norms on

noise", Institut Gigiyeny Truda i Prof- zabolevaniy AMN SSSR, Moscow, 14

(5) 47 (1970).

[21] Kryter, L., The Effects of Noise on Man,

p. 459, Academic Press, New York, N.Y.

1970).

[22] Noises in Tokyo, Report on the Tokyo

Conference on Environmental Protection, November 8-11, 1971.

[23] Sanitary norms for permissible noise

in living quarters and public buildings

and in residential construction areas. Main Sanitary-Epidemiological Administration, USSR, 1971.

[24] Beranek, L., Noise and Vibration Control, p. 585 (McGraw-Hill Book Company, Inc., New York, N.Y. 1971).

[25] Doelle, L., Environmental Acoustics, p. 186 (McGraw-Hill Book Company Inc., New York, N.Y. 1972).

[26] Woods, R. I., Noise Control in Mechanical Services, Published jointly by Sound

Attenuators Ltd. and Sound Research

Laboratories Ltd., 1972.

[27] Rettinger, M., Acoustic Design and

Noise Control, p. 158 (Chemical Publishing Co., Inc., New York, N.Y. 1971).
[28] Sweden National Board of Urban Planing, Samhallspiannering och Vagtrafikbuller, Stockholm (1971).

[29] Schweizerischer Ingenieur—und Architekten—Verein, Empfehlung fuer Schallschutz im Wohnungsbau, SIA No. 181,

Zuerich, (1970).

[30] The Czech Ministry of Health; Richtiinien fuer Gesundheitsschutz gegen

unguenstige Wirkung von Laerm; Vorschriften der Hygiene, Band 28 (1967),

Prague: Staatsverlag fuer Medizinische

Literatur 1967.

[31] Der Bundesminister des innen, Inventar der in der Bundesrepublik Deutschland

geltenden oder geplanten Rechts-und

Verwaltungsvorschriften ueber die

Laermbekaempfung, Bonn, April 30,

1973.
Chapter 4

How to Select a Point on Your Site

for Estimating Transportation

System Noise

In Chapter 3 you selected one or more noise

criterion levels for your proposed building

occupancy. In Chapter 5, you will calculate

the sound level at your site due to highway,

railway, and aircraft noise sources. It is these sound levels that will be used in Chapter 6 to determine the total exterior

sound level in your outdoor activity areas, and the interior sound level in your building's rooms. Also in Chapter 6, you will compare the predicted sound levels to the noise criterion levels that you selected, to determine whether or not your outdoor activiity areas and building's rooms will be too

noisy.

Since sound is attenuated as it propagates

away from its source, the sound levels will vary from one geographical point to another

over your site; and, indeed, each of the computations in Chapter 5 is for the sound level at one particular point. Since each of these

computations takes time, you will want some

strategy for keeping the number of cal- culations at a minimum. Such strategies are

elusive since the construction of your pro- posed building and its site development

may change the acoustical conditions on

the site. Moreover, there are a large number

of variables which will affect your selection

of a site location for estimating transportation system generated sound levels. Thus, we can offer no one specific algorithm for keeping the number of Chapter 5 calculations at a minimum. However, we will in this chapter give you some crude strategies

which should be of assistance in keeping

the number of calculations reasonable.

To take advantage of these strategies for

limiting the number of required calculations, you should already be somewhat

familiar with the contents of Chapters 5 and

6. For example, you should know that there are three major stages in predicting the

noise from transportation system sources

for each activity area or room in your pro- posed building. In Chapter 5 you will complete the first stage by determining the

sound level at some selected point due to a

single transportation system noise source, be it a highway, railway or airport. This

sound level is estimated by performing the

calculations necessary to fill out one or at most two worksheets for each source.

The result of completion of each worksheet

is the sound level at one particular point on

your site due to a single transportation sys- tem noise source.

If there is more than one transportation

system noise source affecting your site, you

must proceed to the second stage, and fill out the additional worksheet(s) as required.

If for example, your site is affected by three

highways (one of which has a sound barrier), a railway, and an airport, you would

end up with seven completed worksheets

when you finish the instructions of Chapter

5. Again, it is emphasized that the sound

levels predicted using these worksheets will be for one particular point on the site.

In the tliird stage, the sound level at a

single site location for any combination of the different types of transportation system

noise cited above will be determined. Henceforth, we will use the terms "site point" and

"receiver" to refer to the location on your

site for which design guide calculations are

to be made. This site point could be an arbitrary location you have selected, or it could

be a proposed outdoor activity area as ex- plained in the first part of Chapter 6, or the

interior of some selected room in your build- ing as explained later on in Chapter 6.

Note that Chapter 6 also offers some strate- gies; namely, strategies for selecting repre- sentative rooms so as to minimize the number of Chapter 6 room-by-room calculations. The gist of these strategies is, whenever possible, to select trial rooms which

have potentially troublesome, or critical, sound conditions. These are strategies

which, ideally, should dovetail with strate- gies for selecting a point or points on your

site for Chapter 5 computations.
24 Given the complexities involved, you can now see that the selection of trial site locations for Chapter 5 calculations will be

based upon both (a) an early familiarity

with your site so as to anticipate where

critically high or low sound levels will likely occur, and (b) an advanced understanding

of your proposed building so as to antici- pate which of its rooms require quiet acoustic conditions, and which are less sensitive

to noise . . . you could then plan to locate

noise-sensitive rooms at quiet site locations, and rooms that are less sensitive to noise at noisy site locations.

To explore the matter further, let's discuss

two typical building design problems. First, let's consider the design of an eight-room

dwelling on a relatively small site, say a

residential lot 75 ft wide and 120 ft deep.

RAILROAD

REAR LOT LINE

POSSIBLE BUILDING

SETBACK LINES

I I

FRONT LOT LINE

75 FT.

Figure 4-1. Dwelling Design Problem Site.

subjected to noise from a railway 500 ft from the lot's rear property line (see Figure

4-1). On such a site there is little choice

in the dwelling's location, especially if building setback distances are required for the lot. However, even if setbacks are not

required and the dwelling could be aligned

with the front lot line to keep it as far away

from the railway as possible, little benefit

would be achieved; because the sound level at the front of the lot would be only one or two decibels lower than at the rear. This is

in accordance with the rule of thumb that the equivalent sound level decreases by

approximately 4 to 6 decibels for every

doubling of distance from a source. What

does this mean? It means that as you get

farther and farther from the railway, small

changes in distance do not change the

sound level appreciably. If the sound level has been determined at the rear property

line 500 ft from the railway, the sound

level at 1,000 ft from the railway is approximately 4 to 6 decibels less. To realize an

additional attenuation of 4 to 6 decibels,

the distance must be increased to 2,000 ft; then 4,000 ft, 8,000 ft, and 16,000 ft, etc., for each additional 4 to 6 decibels of attenuation.

For this design problem, the best strategy

is simply to calculate the sound level at the centroid of the area bounded by setback

lines; or, if there are no setback requirements, at the centroid of the site itself. Then

you may assume that this sound level is approximately correct for any outdoor activity areas on your site, or for any of the

exterior rooms in your proposed building.

A good approximation of the noise levels throughout a site, based on the distance

from the noise source, can be estimated by

calculations for just a few locations. If the

distances from the source to the chosen

location are selected so that they vary by

less than ±15 percent, then generally the

calculations already performed for one

distance will suffice. Within these limits, the sound level will not vary by more

than ±1 decibel among locations. For ex- ample, if your chosen location is 500 ft from the noise source and a sound level of 60 decibels has been determined at that location for a given source, a location 435

ft from the source will have a sound level of approximately 61 decibels and a location

575 ft from the source will have a sound

level of approximately 59 decibels. Barriers,

of course, will alter these sound levels in the manner discussed in Chapter 5, so this part of the calculation must still be made.

Unless the noise source is very close to the
site, or unless the site is very large compared to its distance from the source, quite

possibly only a single sound level estimation will be necessary—one corresponding

to the center of the site.

Now, let's consider a more complex problem involving the design of an eight-room

elementary school for a large, level site near a major roadway as in Figure 4-2.

The roadway is partially shielded from the

site by a 10 ft-high and 800 ft-long, concrete

wail that is located 160 ft from the centerline of the highway. This wall acts as a sound barrier and reduces the noise from

the highway to varying degrees at different locations on the site. The site is large

enough (2,000 ft long by 1,000 ft wide) to allow some freedom in the location of the

school.

The school is to be a one-story building

containing eight classrooms, each of which

is 30 ft wide by 30 ft long by 9 ft high. For

simplification, we will assume that these

are to be the only rooms, aside from corri- dors, in the school. The building scheme,

shown in Figure 4-2, provides four rooms

on each side of a double-loaded corridor. Since this, or any other probable building

scheme, is small in floor area relative to the site area, there are many alternatives

for locating the school on the site.

What strategy should be used to choose one

or more points on the site for trial calcula- tions? The northern portion of the site, farthest from the highway, will probably

be a quiet area of the site. Still, part of the southern portion of the site is shielded

by the concrete wall, which could effectively

shield a one-story building from the auto- mobile and truck noise on this highway.

Thus, let's consider two points . . . point

(a) near the concrete wall and point (b) near the northern boundary of the site, as shown in Figure 4-2.

The sound level at point (a), close to the concrete wall, depends on the distance

between this point and the centerline of the highway, and on the amount of noise

reduction provided by the concrete wall.

If we neglect the effect of the concrete wall,

the sound level at point (a), call it L, would

be affected by the distance attenuation of the sound as it propagates from the highway to this point 280 ft away. But the sound

level at point (a) is less than L because of the shielding effect provided by the wall. The amount of noise reduction is a function of the wall's effective height relative

to the highway and the school, and also a

function of the length of the wall relative to the length of the roadway, hence relative

to the "included angle," as shown in Fig- ure 4-2. The effect of these factors, which

are discussed in detail in Chapter 5, can
be most simply stated as . . . the higher

the wall and the larger the included angle

(long wall), the more noise reduction pro- vided. Thus, point (a) was chosen as near to the wall as possible (to maximize the effective wall height), and midway along the

wall's length (to maximize the included

angle). For the geometry shown in Figure

4-2, a noise reduction due to the shielding

effect of about 5 decibels could be ex- pected. The sound level at point (a) is thus

(L — 5) decibels.

The sound level at point (b), close to the

northern boundary of the site, also depends

on the distance between this point and the

centerline of the highway, and on the

amount of noise reduction provided by the concrete wall. Point (b) is chosen midway

along the wall (to maximize the included

angle) and at a distance of 1000 ft from the

centerline of the highway. Again neglecting

the effect of the concrete wall, the sound

level at point (b) is equal to the sound level at point (a) (L for no concrete wall) minus

a correction to account for the additional

distance attenuation between points (a) and

(b). This additional distance attenuation,

which follows the rule of thumb that the

equivalent sound level decreases by approximately 4 to 6 decibles for every doubling of distance away from the source, amounts to about 8 decibels for this case. Thus, the sound level at point (b), neglecting the

effect of the concrete wall, is approximately

(L — 8) decibels.

The shielding effect of the wall at point (b)

is less pronounced than at point (a) because

both the effective wall height and the in- cluded angle are decreased. For the geometry shown in Figure 4-2, a noise reduction

due to the shielding effect of only 1 decibel

could be expected. The sound level at point

(b) is thus (L — 8 — 1), or (L — 9) decibels,

which is approximately 4 decibels less than

the sound level at point (a). Hence, point

(b) should be chosen as the quietest point

to locate the school and to estimate the transportation system noise. Actually, since

most of the reduction in sound level at point

(b) is due to distance attenuation (8 decibels), any point along the northern boundary

of the site (1000 ft from the centerline of the highway) has a sound level of approximately (L — 8) decibels. Since the calculated noise reduction of 1 decibel provided

by the concrete wall at point (b) is insignifi- cant you may choose any point along the northern boundary.

Either of these two building design problems could be further complicated by the

presence of two, three, or more transportation system noise sources. In this case, the selection of a point for estimating the site noise level can be very difficult. The best

strategy, for such a case with several noise

sources, is to pick a point as far away

from the noisiest source as possible; but

if this is not possible or if you suspect air- craft noise to be a problem, select the centroid of the site for initial calculations.

You may want to consider other alternative

building locations using intuition in the selection of points for estimating sound levels.

Until you develop this intuition, you can

use the following simple site-related guidelines.

Site-Related Guidelines

No siting options . . . Choose the centroid of the building if the noise sources are far away; but if the noise sources are close-by choose points

where critical building rooms are to be

located.

Siting options available:

Single source (no barrier) ... Choose a point as far away as possible

from the source if it will result in a de- crease in sound level; i.e., the distance

between the source and your proposed

building is at least doubled by moving

farther away. If the source is far away

from your site, or if aircraft is the noise

source, the choice of a site point is noncritical.

Single source (with barrier) . . .

If possible, choose a point which satisfies the guidelines above for a single source

with no barrier and is located as close as

possible to the barrier and midway along

its length. This point benefits from both

distance attenuation and barrier noise

reduction. If the selection of such a point

is not feasible, choose an intermediate

point for which a trade-off between dis- tance attenuation and barrier noise reduction may be made.

Multiple Sources . . . Choose a point as far away as possible

from the noisiest source, if it will result

in a decrease in sound level, i.e., the distance between the source and your

proposed building is at least doubled by

moving farther away. If you can't guess

which source is noisiest or if all sources

are equally noisy, choose the centroid

of your site as the point for estimating

the transportation system noise.
Now that we have discussed site-related guidelines, let us now turn to buildingrelated guidelines. These guidelines refer

to positioning the building at a point on

your site that you have chosen. If we refer

to the previous example of the construction

of a school, the overall dimensions of the building scheme are small relative to the

size of the site, and in comparison with

the probable distance between the building

and the highway. It is doubtful that the sound levels will vary much from one end

of the building to the other; and thus, there

is no need to calculate the sound levels for various points along the building.

Now let's consider the case of a large building located close to a highway as in Figure

4-3. The distance from the highway to the

far end of the building is twice as long as

the distance to the near end of the build- ing (200 ft as compared to 100 ft). Thus,

you can expect the sound level to vary by

4 to 6 decibels from one end of the building to the other. The best strategy for such

a case is to calculate the sound level for each point of interest, be it an outdoor

activity area or one of the rooms of the

building.

Again, as with site-related guidelines, you

must use intuition in selecting the number

of points for estimating the sound level. Until you develop this intuition, you can use

the following simple building-related guidelines.

Building-Related Guidelines

Building is small and is located far from

the source . . . Choose a point corresponding to the centroid of the building and follow the appropriate site-related guidelines listed previously. Using only one point for your

calculations is valid if the two ends of the building are within ±15 percent of the distance from the source to the build- ing . . .

Building is large and is located close to the source . . . Choose several points corresponding to the location of outdoor activity areas and rooms of interest. You can limit the total number of points using the rule of thumb

that the sound level will only vary by ±1

decibel for locations within ±15 percent

of the distance from the source to the point of calculation . . .

Figure 4-3. Building Located Close to a Highway.

Chapter 5

How to Estimate Building

Site Noise

Section 1 Sound

Propagation and

Barriers

When dealing with sound and its effects on

the occupants of your proposed building,

three components need to be considered:

the source of the sound, the path along

which the sound travels, and the receiver or

individual who hears the sound. Various

effects of sound on the receiver have been

discussed in Chapter 3. In this section the sources of sound and how sound propagates

from the source to the receiver are described.

Sound can be generated by the vibration of a solid body in contact with the air; forces

acting directly on the air, such as a fan; or by the violent motion of the air itself as from a jet. Consider for example, what

happens when the sheet metal panels of a

truck hood are set into vibration by the

truck's engine. The vibrating panels move

in and out. As they move outward, they push

against the air nearest them; as they move

inward they produce a partial vacuum, or

rarefaction, in the nearby air. The alternate compression and expansion of the air adja- cent to the panels results in small local fluctuations in the atmospheric pressure. These fluctuations in turn cause a portion

of the air farther away from the panel also

to fluctuate in pressure. This local disturb- ance is thus propagated through the air as sound waves that reach our ears. The same

general principles apply to other mechanisms of sound generation in that small local fluctuations in the atmospheric pressure are created and propagated through the air as sound waves.

The sound waves that are generated by

these two mechanisms are known as elastic waves, which are characterized by the fact that a disturbance initiated at one point is propagated to other points in a predictable manner determined by the physical properties of the medium of propagation. The

sound heard by a receiver depends upon the type of sound wave, the medium (usually

air), the type of wave divergence taking

place, and the excess attenuation.

Two common types of sound waves are

spherical sound waves and cylindrical sound

waves. Spherical sound waves are usually

generated by a source whose overall dimensions are small compared with the wavelength of the sound produced. This type of sound source is called a point source. In contrast, cylindrical sound waves are generated by a source whose radial dimensions

are small compared to the wavelength of the sound produced, but axial dimensions

are infinite or extremely large. This type of sound source is called a line source*.

Wave divergence refers to the spreading

out of the sound wave from a source into the surrounding atmosphere. The effect of

this spreading is to decrease the sound

level at the receiver as he moves farther away from the source. Wave divergence is different for point and line sources—for an

idealized point source, the sound level de- creases by 6 dB for each doubling of dis- tance away from the source; for an ideal- ized line source, the sound level decreases

by 3 dB for each doubling of distance

away from the source. These values of wave divergence are for ideal sources which

radiate sound uniformly into a homogeneous loss-free atmosphere, free of barriers.

Excess attenuation is the added decrease

of sound level beyond that caused by simple

*

It should be pointed out that since this design

guide uses the Leq mertic, which is based on

averaging the variations of the sound level over some specified time period to obtain an equivalent sound level, to make a distinction between

point and line sources is not quite accurate. If a point source such as an auto or trucl< moves

past a stationary receiver, the instantaneous sound level will first increase as the source ap- proaches, reach a maximum, and then decrease

as the source moves away. In using the Leq

metric, this time varying sound level is averaged

to give constant equivalent sound level of equal

energy. Thus, the net effect is to approximate

the moving point source as a stationary, infinite line source generating a sound level equal to Leq

at the receiver. This fact is mentioned only for the sake of technical accuracy. It has no effect on how you will pedorm the calculations in later sections because it has been implicitly incorporated

into the transportation system noise models.
wave divergence, and includes attenuation

by absorption in the air; attenuation by en- vironmental conditions (rain, sleet, snow

or fog); attenuation by grass, shrubbery and

trees; attenuation and fluctuation due to wind and temperature gradients, atmospheric turbulence and the characteristics

of the ground; and, attenuation due to barriers or other types of shielding [1]. Thus,

by including excess attenuation you can

correct the ideal, loss-free case to account

for atmospheric and environmental ele- ments that reduce sound levels.

In this design guide, the sound level generated by each type of transportation system

noise source will be predicted assuming

"typical" values of attenuation due to wave

divergence and environmental conditions.

Then account will be taken for additional

attenuation effects of any barriers, rows of intervening buildings or heavy vegetation.

The remainder of this section contains a general discussion of sound barriers and

how to predict the attenuation they provide.

Also, the barrier effect of buildings and the attenuation due to vegetation are discussed.

These shielding effects are essential for predicting highway and railway noise in Sections 5.2 and 5.3 of this chapter.

Barriers

A sound barrier can be any obstruction

which shields, or partially shields, the sound

source from the receiver. The effect of this shielding is to reduce the level of the sound

heard by a receiver by an amount dependent

upon, among other things, the location and

configuration of the obstruction. Based on

this definition, walls, earth berms, the sides

of depressed highways or railways, the

edges of elevated highways and railways,

and any other obstruction of sufficient size can act as sound barriers. Examples of these

types of shielding are shown in Figures

5.1-1 through 5.1-4.

The attenuation provided by a barrier depends upon how much of the total sound

energy is blocked from the receiver. Obviously, if some of the sound energy can pass

by the barrier, its effectiveness is lessened.

There are basically four paths which sound

can follow from the source, past (or through)

the barrier, to the receiver [2]. These paths,

discussed in the next few paragraphs, are shown in Figure 5.1-5.

The direct path refers to the sound that passes over or around the barrier without

being affected i.e., there is no diffraction.

r

W

Figure 5.1-1. Shielding by a Wall.n

c

Figure 5.1-3. Shielding by a Depressed

Highway or Railway.

Figure 5.1-2. Shielding by an Earth Berm.

Figure 5.1-4. Shielding by an Elevated

Highway or Railway.

SHADOW ZONE

Figure 5.1-5. Paths along which sound en- ergy can travel from the source to the

receiver [2]. Also shown is the shadow

zone and the angle of diffraction associated with the source-barrier-receiver

geometry.
31 For this path, the barrier does not block the

line-of-sight between the source and re- ceiver and therefore provides little or no

attenuation. The direct path can be affected

only by increasing the height of the barrier so that the line-of-sight between the source and receiver is blocked.

Sound energy that passes just over the top

edge of the barrier is bent down into the apparent shadow zone, which is the area

visually shielded from the source as shown

in Figure 5.1-5. This path is the diffracted

path, analogous to the optical diffraction of

light. The sound waves that are diffracted are attenuated, and the larger the angle of diffraction (defined in Figure 5.1-5), the more

the sound wave is attenuated in this shadow

zone. The amount of sound energy reaching the receiver via the diffraction path is dependent upon the barrier height and the

location of the source and receiver relative to the barrier. If either the source or receiver

is placed close to the barrier, the angle of

diffraction and hence the attenuation is in- creased. The amount of attenuation due to diffraction of the sound wave is dependent

on the shape of the barrier. In general, most

theories of diffraction that have been developed for predicting barrier attenuation treat

only infinitely long walls with a thickness

much less then the wavelength of the dif- fracted sound (rigid-screen barriers). Theoretical and experimental investigations [3] have shown that the attenuation by wedgeshaped or wide barriers is somewhat differ- ent from that predicted by rigid-screen theories. However, predicting the attenuation

by these other barrier shapes is difficult and

only a small improvement in the accuracy can be achieved. Hence, this design guide

applies the theory developed for an infinitely

long rigid-screen for all barrier shapes and

sizes.

Another path is one directly through the

barrier. Sound traveling this path is reduced

by an amount related to the so-called trans- mission loss of the barrier, a measure of the reduction in level of the sound that passes

through the barrier. The transmission loss depends most importantly upon the weight

per unit area of the barrier—the heavier the

barrier the less sound transmitted. As a general rule, if the surface weight density, which

is the weight density (Ib/ff) multiplied by

the barrier thickness (ft), is greater than 4

lb/ft ', the transmission of sound through the

barrier will be negligible relative to the sound energy diffracted over or around the

barrier [4].

Figure 5.1-6. Two cases where reflected waves effectively reduce barrier attenuation.
The last path shown in Figure 5.1-5 is the

reflected path. Reflected sound is usually

of concern only to a receiver on the same

side of the barrier as the sound source. Two

special cases where reflected sound waves may be important are shown in Figure 5.1-6.

In both cases, part of the sound energy

radiated by the source is reflected from a nearby surface and then propagated to the

receiver. Depending upon the location of the reflecting surface and barrier relative

to the source and receiver, the barrier at- tenuation may effectively be reduced to zero

(i.e., the sound level at the receiver is the same with or without the barrier). It should

be noted that in most practical cases, the

reflected noise does not play an important

role in the treatment of barriers [5]. If you

encounter a serious situation of reflected

noise, you may need the services of an

acoustical consultant.

If the barrier provides a substantial amount

of attenuation, the sound diffracted over or around the barrier into the shadow zone

usually represents the most important path

between the source and receiver. Hence,

estimating the amount of attenuation due to diffraction is the primary calculation in- volved in determining barrier attenuation in Sections 5.2 and 5.3. However, there are two

other considerations in determining barrier

attenuation. These are the overall length of the barrier relative to the source length, and

the presence of holes or openings in the

barrier. A short barrier permits sound to propagate around its ends, and a barrier

with holes permits sound to be transmitted

directly through the barrier.

Line Source

Receiver

Figure 5.1-7. Paths for Sound Energy to Travel Around the Ends of a Barrier.

For sources, such as highways and railways,

which are conceptually represented as line sources, the length of the barrier is particularly important. For example in Figure 5.1-7,

the noise diffracted over the top of the

barrier is reduced; however, the sound

propagating from the part of the roadway

extending beyond the ends of the barrier

is not affected by the barrier. As a result,

the actual reduction of sound due to the

barrier is less than that predicted for the

diffraction of the sound wave. To be effective, barriers must not only break the line- of-sight between the receiver and the nearest

section of roadway, but also between the

receiver and sections far up and down the

roadway. To decide when predicted barrier

attenuation must be adjusted to account for sound coming around its ends, refer to the

barrier "included angle," denoted "a", and

defined in Figure 5.1-8. If the included

angle, "a", is greater than 170°, the barrier can be considered infinitely long. This means

that the attenuation depends only upon

sound diffraction across the top of the barrier. But if the included angle, "a", is 170°

or less, the barrier length is considered

finite, and adjustments must be made to account for sound coming around the ends

of the barrier. These adjustments are in- cluded in the predictive procedures of Sections 5.2 and 5.3. —-Line Source — — —

Receiver

Figure 5.1-8. Barrier Geometry Showing

the Included Angle, a. Holes or openings substantially increase

the sound transmission of a barrier, thus

reducing its effectiveness. This is best illus- trated by the data shown in Table 5.1-1. If, for example, a barrier has openings which

amount to ten percent of its total area, its overall attenuation would not be greater

than an A-weighted sound level difference of 4 dB, considering attenuation due to both

transmission and diffraction. For a barrier

with openings greater than ten percent of

its area, the attenuation will probably be

negligible.

Maximum

Percent of Barrier Transmission

Area that is Open Loss Possible, dB

50% 0

10% 4 5% 7 1% 14

0.5% 17

0.1% 24

Table 5.1-1. Transmission Loss for Barriers

with Holes [2].
Before continuing this discussion, let's re- view a few general principles of barrier attenuation; specifically, tine relationship

between sound attenuation expressed in decibels and in energy terms as shown in Table 5.1-2. The nneaning of these numbers

can be explained by considering, as an

example, a barrier which attenuates the noise from a highway by an A-weighted

sound level difference of 10 dB. Referring

to Table 5.1-2, it can be seen that this atten- uation of 10 dB is equivalent to eliminating

90 percent of the energy initially propagated

towards the receiver. This drastic reduction

in energy relative to the sound level attenuation can be understood in view of the logarithmic nature of the measure. Table 5.1-3

provides general rules for the feasibility of obtaining various levels of attenuation from

barriers [5]. Table 5.1-2. Attenuation in Terms of Decibels and Energy [2].

Attenuation

dB Reduction

Remove % of Energy

3 50%

6 . 75%

10 90%

20 99%

30 99.9%

40 99.99%

Table 5.1-3. Feasibility of Obtaining

Attenuation from Barriers [5].

Barrier Attenuation* Feasibility

5 dB Simple

10 dB Attainable

15 dB Very Difficult 20 dB Nearly Impossible

A-weighted sound level attenuation in decibels

The method used in this design guide for calculating the attenuation provided by a

barrier is based on the work of Kugler and

Piersol [6]. Their model, which assumes

that highway traffic can be treated as a line source parallel to an infintely long screen

barrier, relates the attenuation to the path

length difference, L. Given the sourcebarrier-receiver geometry shown in Figure

5.1-9, the path length difference is defined

as, L = A + B — C. The distance (A -|- B) is the shortest path over the barrier's edge from the source to the receiver; C is the direct path distance

from the source to the receiver through the

barrier.

The relationship between the path length

difference and the attenuation provided by

a barrier is a function of the frequency

spectrum of the sound source. Kugler and

Piersol found that the reduction of highway noise by a barrier could be estimated

with sufficient accuracy by assuming a frequency of 500 Hz [6]. The dashed

curve of Figure 5.1-10 shows the relation- ship between path length difference and the attenuation provided by an infinitely long

barrier screening a line source radiating

sound at a frequency of 500 Hz. As a more

conservative estimate of the noise reduction,

Kugler and Piersol proposed a simplified

linear curve shown dotted in Figure 5.1-10. However, this design guide employs the

solid curve shown in this figure, which is even more conservative because the atten- uation for small values of L goes to zero in- stead of asymptotically approaching a value

of 5 dB as for the general line source model;

and because the maximum attenuation is limited to an A-weighted sound level differ- ence of 12 dB for large values of L due to environmental effects.

L = A + B — C

A ^^^"^^^^-^ B

%-=^ fflr

Source Barrier Receiver

Figure 5.1-9. Barrier Path Length Difference.
34

25

0.01 0.1 1.0 10.0 100.0 Path Length Difference, L, feet

Figure 5.1-10. The A-weighted attenuation models [6]. The assumed frequency of the

provided by an infinitely long barrier source is 500 Hz. versus path length difference for various

When sound is attenuated by a barrier, it

is not uniformly reduced in level across its entire frequency range. Instead, its high

frequencies are reduced more than its low

frequencies. The result is a change in the

spectrum shape of the sound at the building

site. This is of little or no consequence in calculating the sound level in outdoor activity areas, but it is important in estimating

the sound level inside a room since the spectrum shape of the sound can be critical

in determining the sound isolation properties

of the building shell. Low frequency sound

energy passing over the barrier is easily

transmitted through the external shell of the

building. Based on a detailed study of this problem, discussed in Appendix B, it was

found that the building shell isolation rating

must be degraded by about 3 dB for exterior

noise dominated by sound propagating over

a barrier. Alternatively, the estimates of barrier attenuation can be reduced by a corre- sponding amount. This correction in incor- porated in the solid curve of Figure 5.1-10.

To predict the attenuation of a barrier you

must determine the path length difference

L. You can do this graphically by an accurately scaled section cutting through the ter- rain between the transportation system sound

source and your proposed building. Such

a drawing will show the height of the source and receiver relative to the top edge of the

barrier. Since any real transportation system

sound source is composed of several sub- sources (e.g., heavy truck noise is a combination of sounds radiated from the engine, fan, intake, exhaust, and tires), an

effective source height based upon all the

subsources must be used. The effective source height is dependent upon the type

of transportation system sound source—it

is assumed to be located at the roadway

surface for automobiles; at track level for railway cars; at eight feet above the surface

for heavy trucks: and fifteen feet above the

surface for diesel-electric locomotives (more

will be said about effective source height

in Sections 5.2 and 5.3).

The receiver location will be in some out- door activity area on your site or some room

in your building. The following examples

discuss the effect of receiver location on

the resulting attenuation.

1. Rules for calculating L

if the building you are designing is to be

many stories high, the attenuation provided

by a barrier can vary substantially between

the ground and upper floors. This variation

is dependent upon the height and location of the barrier and sound source relative to your building. The way to check this is to calculate the value of L for several repre- senative story heights, and then using these

values, determine the barrier attenuation

from Figure 5.1-10. Two examples are shown in Figures 5.1-11a and 5.1-11b.
Relative Mtenualions, dB Building showing "receivers" at each floor

(a) Example of a building located close to a

barrier, showing the change in attenuation for receiver locations at each floor.

Relative Attenuations, dB

Li = A + Bi - Ci; 14

L4 = A -;- B4 — C4; 14

Source

Barrier (b) Example of a building located far from

a barrier, showing that the effect of re- ceiver height on the attenuation is minimal.

Figure 5.1-11. Examples of Determining

the Path Length Difference for Various

Receiver Locations.
In Figure 5.1-11a, the building is close to the barrier, and the attenuation varies between two extremes. For the ground floor the attenuation is high, but it continuously

decreases so that for the upper floors there

is no barrier attenuation at all because the

line-of-sight with the source is not blocked.

The second example, shown in Figure 5.1-

11-b, does not have these extremes of attenuation. Since the building is farther away

from the barrier than in Figure 5.1-11a, the value of L does not vary much between the

top and bottom floors.

Selections of representative building rooms

for noise prediction are discussed in Chapter 6. Essentially, the selection is left to you, the user of this design guide. When in doubt, you should estimate the barrier atten- uation at each outdoor activity area and

room that you analyze in Chapter 6.

An alternative to graphically measuring the

dimensions of A, B and C from a drawing

is to calculate A, B and C from vertical di- mensions of the source, barrier, and re- ceiver. This method, shown in Figure 5.1-12,

has the advantage that the effective source

height is included in the equations for A,

B and C. This method, discussed in Sections

5.2 and 5.3, is preferred for determining the

path length difference. Horizontal and vertical dimensions should be measured as

precisely as possible so that an accurate

estimate of the attenuation can be cal- culated.

For most barriers, determining the attenuation is relatively simple. To deal with special cases, however, you should be familiar with

the general rules discussed below.

Effective Source Location • Heavy Trucks (8") Barrier

A = l/hB2 + (DC - DB)2

B = \/ (HB + hB)2 -f DB2

'

C = l/ hB2 + DC2

'

Automobiles

A = i/(HB - 8)2 + (DC - DB)2

'

B = 1/ (HB + hB)2 + DB2

'

C = l/(hB + 8)2 + DC2

'

Heavy Trucl<s

8' Effective Source

Height

Figure 5.1-12. Example Showing Horizontal

and Vertical Dimensions of Source, Barrier, and Receiver Geometry and Equations for A, B and C.
37 2. Barriers in series

There may be sites having more than one

barrier between the source and receiver, as shown in Figure 5.1-13. Whereas, both barriers attenuate noise, and might be considered "in series", such an additional complication is not worth the slight improvement in accuracy; instead, only the "domine^nt" barrier—the one which provides the most atten- uation—should be considered. To determine

which barrier is "dominant", calculate the

path length difference for both, and choose

the barrier with the larger value of L. This,

of course, presumes that both barriers are

long enough to block all of the source; if not, you must also consider the length of each barrier.

Barrier Barrier

Figure 5.1-13. Example of Two Barriers in Series, Showing How to Determine Which

Barrier is Dominant.

3. Receiver located beyond the end of the

barrier

When a receiver is located just at the end

of the barrier, the receiver is not shielded

from one end of the line source. For this case, the maximum attenuation is an A-weighted

sound level difference of 3 dB. For receivers

beyond the end of the barrier, as in Figure

5.1-14, the attenuation is negligible.

Line Source

Receiver

No Attenuation

Figure 5.1-14. Receiver Located Beyond

the End of a Barrier.
4. Elevated and depressed highways and

railways

Some general comments can be made concerning the attenuation of depressed and

elevated highways and railways as a function of receiver location. As shown in Fig- ure 5.1-15, as the receiver position is pro- gressively moved farther away from a sound

source located on an elevated configuration, the path length difference (hence the

attenuation) decreases. Conversely, for a sound source located in a depressed configuration (Figure 5.1-16), the path length

difference (hence the attenuation) increases

for more remote receiver locations. Thus, to obtain optimal attenuation for a given ele- vation or depression the receiver should be

located close to the elevated highway or

railway, but as far away as possible from a depressed highway or railway.

Relative Attenuations, dB Source

Relative Attenuations, dB

Li = Line- of • sight not blocked; No Attenuation

L2 = A + B2 - C2; 9

L3 = A + 83 - C3; 12

Ci; 15

Figure 5.1-15. Example Showing How At- tenuation Decreases as the Receiver Location is Moved Farther from an Elevated

Highway or Railway.

Source

Figure 5.1-16. Example Showing How At- tenuation Increases as the Receiver Location is Moved Farther from a Depressed

Highway or Railway.
39

5. Combination of elevated or depressed

configurations plus a barrier

For a barrier combined with an elevated or depressed configuration, the path length

difference is determined as shown in Figures

5.1-1 7a and 5.1-1 7b, respectively. For these

and other similar combinations, the important thing is the barrier height relative to the source and receiver, which is measured

in term's of path length difference.

Barrier

Source

Receiver

(a) Elevated highway or railway and barrier.

Figure 5.1-17. Method of Determining the

Path Length Difference for Combinations

of Different Types of Shielding.
40 6. Path length distance for elevated and

depressed configurations and earth

berms

Determining the distances necessary to cal- culate the path length difference for ele- vated and depressed configurations and

earth berms can be difficult since they are

likely to be irregular in height or width.

Figures 5.1-18a and 5.1-18b show how to estimate roughly the height and length for one example of an earth berm. The same

general method should be used for elevated

and depressed configurations. Since, such

methods provide only approximate dis- tances, they should be applied conservatively. Moreover, if any of these configurations are questionable because they are

either short in length or not very high, their attenuation should be disregarded.

1

1

I

I ^^^^^^ ^^^^^^^^^^J^j^^^^

(a) Section through earth berm showing

assumed height, H. and length. L.

Receiver

n Highway

(b) Top view of berm showing the assumed

included angle, a.

Figure 5.1-18. Technique for Estimating Dimensions of an Earth Berm.
41 7. Barrier turned at the end or top

If a barrier is not straight but angled, either

at the end or at the top, the path length

difference is still determined by how much

of the source is blocked from the sight of the receiver as shown in Figures 5.1-19a

and 5.1-19b. Note that this angling of a barrier is one way to increase its performance

without making it excessively long or high.

n cm Line Source IT"

Barrier

Receiver

(a) Plan view of barrier turned at the end

A .

Source 1 C - " EE

ffln

Receiver

(b) Plan view of barrier turned at the top

Figure 5.1-19. Included Angle and Path Length Difference for Barriers With Turns.

8. Summary

In summary, the following can be said about

noise barriers.

1. If a barrier does not block the line-of- sight between the source and receiver,

the barrier will provide little or no attenuation.

2. If a barrier is constructed of a material

with a surface weight density greater

than 4 Ib/ff and there are no openings

through the barrier, transmitted sound

will usually be negligible.

3. If there are openings over 10 percent

or more of the barrier area, barrier attenuation will be negligible.

4. Diffracted sound is usually the most
important aspect in estimating barrier

attenuation.

5. Reflected sound can be important for receivers on the source side of a barrier,

but it normally is not a factor for re- ceivers on the side opposite from the source. Hence reflected sound is usually not important to your building and site.

6. Transmission of sound around the ends

of the barrier can be critical if the barrier included angle is less than 170°.

7. Barrier attenuations greater than an A-weighted sound level difference of 10

dB are difficult to obtain.

8. For two or more barriers "in series",

consider only the "dominant" barrier.

9. Assume no attenuation for a receiver

located beyond the end of a barrier.

9. Buildings as Barriers

Let us now discuss the shielding provided

by rows of buildings located between a sound source and your building site. The

excess attenuation of such buildings acting as barriers can be as high as 10 dB, but

special procedures are needed to predict

the attenuation based on the size, shape and

spacing of the intervening buildings.

One way of handling such shielding would

be to deal with each building acting as a

barrier. A simpler but more approximate

method is that given in reference [6]. This

technique, the one used in this design guide,

assigns a value of 4.5 dB attenuation for the

first row of buildings and an additional 1.5 dB for every subsequent row, up to a maximum of 10 dB. (For example, four rows of buildings between the source and building

site would provide a total attenuation of 9

dB.) To obtain these values of attenuation

the following conditions must exist:

1. The open area between the buildings

must be less than 40 percent of the total open area, so that the buildings form an effective visual barrier between the source and your building or site.

2. The average height of the first row of buildings should equal or exceed the average height of your proposed building. (For example, a row of one-story

buildings on a level terrain, may pro- vide little or no attenuation for the

second floor of a building located behind the row of one-story buildings.)

3. The row of buildings acting as a barrier should visually block most of the

length of the source from your building or site.

For buildings acting as barriers that are less densely packed than 60 percent a lower

noise attenuation could be estimated. If

the buildings acting as a barrier occupy

only 10 to 20 percent of the area paralleling

the source, each building might produce a

small localized amount of shielding, but the

combined effect of such sparsely spaced

buildings would be negligible. On the other

hand, a long, continuous, solid building

occupying most of the area along a source can be treated as a barrier, and its attenuation estimated by methods previously dis- cussed using path length difference and

included angle. In general, however, judgments concerning the barrier effects of buildings should be made conservatively.

10. Vegetation as a Barrier

Let us now describe a last form of excess

attenuation due to vegetation. To provide

significant attenuation, the vegetation should

consist of large belts of trees or shrubs more than 50 feet in depth, more than 10

feet in height and dense enough to visually

block the source from the receiver. The ex- cess attenuation due to such belts can be

as high as 5 to 10 dB, but its accurate esti- mation is difficult. Research has shown that diffusion or scattering of the sound waves

off the leaves, stems and trunks, rather than

absorption, is the principal mechanism for attenuating the sound [7, 8, 9]. The

amount of diffusion, hence attenuation, is dependent upon the height, width and overall density of the belt. The density depends

upon the species of vegetation, planting

patterns, and the foliage distribution from

the ground to the top of the tree or shrub.

(Obviously, deciduous trees provide little attenuation when dormant.) Prediction of excess attenuation based on these factors

is not practical for this design guide;

instead, you should simply allow an A-weighted attenuation of 5 dB per 100

foot depth of woods up to a 10 dB maximum [10]. For these values of attenuation,

the following conditions must exist:

1. The woods must be of sufficient density

to block all visual paths between the source and receiver.

2. The underbrush or ground cover should

also be of sufficient density and height

to block all visual paths between the source and receiver.

3. The woods should extend at least 15

feet above any line-of-sight between

the source and all portions of your build- ing or site.

4. The woods should be long enough to visually block most of the length of the source from the receiver.

5. To be effective year-around there should

be a reasonable mixture of both decidu- ous and evergreen trees, or all should

be evergreen.
For low density growth a token amount of attenuation sucti as 2 or 3 dB per 100 feet, up to a 10 dB maximum, might be per- missible [10]. It is also pointed out that the reason for the 10 dB maximum is that the

effectiveness of the vegetation belt can be

compromised when sound propagating over

the tops of the trees is bent down to earth beyond the growth by various mixtures of wind and temperature gradients.

Thus, the 10 dB limitation is imposed so

that the excess attenuation is not over- estimated.

Another aspect of vegetation shielding is that although a single tree or even a few

widely scattered trees do not appreciably

reduce the noise, they do have aesthetic

and psychological value by visually screening the source from the receiver. Thus,

during construction of your building an

effort should be made to preserve any

existing trees, hedges or other shrubbery.

Or, new landscaping could be planned, to help shield the source from the building.

Cook and Van Haverbeke [7], give the fol- lowing recommendations concerning planting and types of vegetation:

1. "To reduce noise from high-speed car and truck traffic in rural areas, plant

65- to 100-foot wide belts of trees and

shrubs, with the edge of the belt within

50 to 80 feet of the center of the nearest

Table 5.1-4. Evergreen Trees and Shrubs That Should Be Suitable for Year-Round Noise

Screening and That Have a Relatively Wide Range of Adaptability [7].

Common name Regions of best adaptability

Tall

Firwhite

Veitcti's silver, Nikko balsam

corkbark

Fraser

California red Spanish Cedar

atlas deodar, Cedar of Lebanon

Port-Orford cedar

Arizona cypress Spruce

Norway, white Serbian,

Oriental, blue Pinewestern white ponderosa

Scotch

red

Austrian, eastern white Monterey

Douglas fir Giant sequoia. Redwood

Western redcedar Hemlock

eastern Carolina western Medium

Juniper (upright) eastern redcedar and varieties Rocky f^ountain and varieties Chinese and varieties Grecian

Irish Swedish Yew

Japanese and varieties English Arborvitae American and varieties Oriental and varieties

Short

Juniper Chinese (Pfitzer) and others l^ugo pine

Arborvitae American and varieties Oriental and varieties Yew

Japanese and varieties Some Broad-leaved Evergreens

Pyracantha Euonymus

Privet

Nationwide

East Midwest, North, Northeast Midwest, Southwest, Southeast

East, Southeast West

West Coast

West Coast West Coast, South, Gulf Coast West Coast, South, Southeast Southwest, South, Southeast

Nationwide (best in north) Nationwide (best in north)

West

West, Midwest

Nationwide (best in north)

East, North Midwest, East

California Coast

Nationwide (except South) West Coast West

East, Southeast

East Coast, Southeast, South West Coast

East of Rocky Mountains West of Rocky Mountains, Midwest

Nationwide

Nationwide

Nationwide (best in north) Nationwide (best in north)

Nationwide

Nationwide (best in east)

Nationwide (best in north, northeast) South

Nationwide

Nationwide

Nationwide

Nationwide

Nationwide

Nationwide (best in south half) Nationwide

South
traffic lane. Center tree rows should be

at least 45 feet tall (See Table 5.1-4 for species recommendations). Where rightof-way width is large, as on certain sections of Interstate highways, several rows of trees and shrubs may be planted,

to reduce noise levels at adjacent

property.

2. "To reduce noise from moderate-speed

car traffic in urban areas, when tire-road- way interaction is the principal cause of noise, plant 20- to 50-foot-wide belts of trees and shrubs, with the edge of the

belt from 20 to 50 feet from the center

of the nearest traffic lane. Use shrubs

6 to 8 feet tall next to the traffic lane,

with backup rows of trees 15 to 30 feet

tall (see Table 5.1-4 for species recommendations).

3. "Trees and shrubs should be planted

close to the noise source, as opposed to close to the protected area, for optimum

results.

4. "Where possible, use taller varieties of trees which have dense foliage and

relatively uniform vertical foliage dis- tribution (or combinations of shorter

shrubs and taller trees to give this

effect). Where the use of tall trees is restricted, use combinations of shorter

shrubs and tall grass, or similar soft ground cover, as opposed to paving,

crushed rocl< or gravel surfaces.

5. "Trees and shrubs should be planted as

close together as practical, to form a

continuous, dense barrier. The spacing

should conform to established local practices for each species.

6. "Where year-round noise screening is desired, evergreens, or deciduous varieties which retain their leaves throughout

most of the year, are recommended.

7. "The belt should be approximately twice as long as the distance from the noise source to the receiver and when used

as a noise screen parallel to a roadway,

should extend equal distances along the

roadway on both sides of the protected

area."

This concludes the discussion of sound

propagation and barriers. The remaining

sections of this chapter deal with the three

major noise sources: highways, railways and

aircraft. Proceed to these sections as di- rected in Chapter 2.

References

Chapter 5

Section 1 Sound Propagation

and Barriers

[1] Beranek, L. L. (ed.). Noise and Vibration Control (McGraw-Hill Book Co.,

Inc., New York, N. Y., 1971).

[2] Anderson, G. S., Miller, L. N., and Shadley, J. R., Fundamentals and abatement

of highway traffic noise (Federal Highway Administration, Washington, D.C,

1973) . Available from the National

Technical Information Service, Springfield, Virginia, Accession No. PB 222-

703.

[3] Kurze, U. J., Noise reduction by barriers, J. Acoust. Soc. Am. 55 (3), 504-

518 (March 1974).

[4] Kurze, U. J., and Anderson, G. S., Sound attenuation by barriers. Applied

Acoustics 4 (1), 35-53 (January 1971).

[5] Kugier, B. A., Commins, D. E., and

Galloway, W. J., Establishment of standards for highway noise levels: Volume

1 —Design guide for highway noise

prediction and control, BBN Report No. 2739 (Bolt Beranek and Newman Inc., Los Angeles, California, February

1974) .

[6] Kugier, B. A., and Piersol, A. G., Highway noise: A field evaluation of traffic noise reduction measures, NCHRP Report 144 (Bolt Beranek and Newman,

Inc., Canoga Park, California, 1973).

Available from the Highway Research

Board, 2101 Constitution Ave., Washington, D.C. 20418.

[7] Cook, D. I., and Van Haverbeke, D. P., Trees and shrubs for noise abatement.

Research Bulletin 246 (The Agricultural

Experiment Station, University of Nebraska College of Agriculture, Lincoln,

Nebraska, July 1971).

[8] Aylor, D., Noise reduction by vegetation and ground, J. Acoust. Soc. Am.

51 (1), 197-205 (January 1972).

[9] Cook, D. I., and Van Haverbeke, D. P., Tree-covered land-forms for noise control. Research Bulletin 263 (The Agricultural Experiment Station, Institute of Agriculture and Natural Resources,

University of Nebraska, Lincoln, Nebraska, July 1974).

[10] Gordon, C. G., Galloway, W. J., Kugier,

B. A., and Nelson, D. L., Highway noise —a design guide for highway engineers, NCHRP Report 117 (Bolt Ber- anek and Newman Inc., Los Angeles,

California, 1971). Available from the

Highvi^ay Research Board, 2101 Constitution Ave., Washington, D.C. 20418.
Chapter 5 Section 2 How to Estimate

Highway Noise

Highway traffic, probably the most common

and widespread source of noise, is ex- tremely variable—different vehicles travel- ing at different speeds through continuously

changing highway configuraions and sur- rounding terrains. Obviously, to estimate

highway noise, many simplifying assumptions must be made concerning how the noise is generated and how it propagates

from the highway to the building site. Even

after these assumptions have been applied,

the problem of predicting highway noise is

still complex.

Researchers have developed predictive

models of complex highway traffic systems,

but the models are either long and detailed, or rely upon computers for numerical re- sults [1, 2, 3]. For our purposes we would

like a method of estimating highway noise

that is as simple as possible to use. One

of the simplest tools for estimating highway

noise is a nomogram developed by Bolt Beranel< and Newman, Inc.* [3], which is easy to use and gives results that are conservative (i.e., the predicted levels are higher

than would actually occur) in all but a few

* This work, which was undertaken by Bolt Beranek and Newman, Inc., was sponsored by the American

Association of State Highway and Transportation Officials, in cooperation with the Federal Highway Administration, and was conducted by the National Cooperative Highway Research Program which is administered by the Transportation Research Board of the National Academy of Sciences-National Research

Council.

Pivot

Point

20 30 40

+

20

Heavy

Trucks

50 + + + ' 60 70

SPEED: IVIPH

30 40 50 Automobiles and Medium Trucl<s

60 7° + +

HNL

dB

100

90

80

70

60

50

40

Predicted Noise Level

DC

FT

30

40 -

50 -

70 -

100-

150-

200

300

400 -

500

700

1000-

1500

2000 —

Distance To

Observer

Figure 5.2-1. Highway Noise Prediction Nomogram [3].
very special cases. A nomogram is simply

a graph containing three or more scales

graduated for different variables so that when a straight line connects the values on any two scales, the related value may be

read directly from the third scale at the

point intersected by the line (See Figure

5.2-1). The graphical procedures for using

this nomogram are given later in this chapter in STEPS H3 to H5.

The analytical model upon which the highway nomogram is based is highly idealized. For example, the model assumes that the

different vehicle types can be categorized

in three groups based upon the vehicles'

noise generating characteristics. The groups —automobiles, medium trucks and heavy

trucks [3] —have basic differences both

physical and acoustical.

Automobiles are vehicles with two axles

and four wheels. This group includes, in addition to passenger cars, light pick-up

and panel trucks. Under normal operating

conditions, automobile noise is composed

primarily of engine-exhaust noise and tire- roadway interaction noise, which are both

concentrated near the pavement surface. Hence, the effective source height is taken

at this surface.

Medium trucks refer generally to gasolinepowered two-axle, six-wheel vehicles such

as local delivery or short-haul trucks. One

distinction between this group and heavy

trucks, other than just physical size, is that medium trucks do not have a vertical ex- haust stack. Like automobiles, medium truck

noise is primarily engine-exhaust and tire noise, which again are concentrated near

the pavement surface; and although the

exhaust outlet may be slightly higher for medium trucks than for automobiles, the

effective source location is still assumed to be at the pavement surface [3]. In general,

the sound levels generated by medium

trucks are similar, but are higher than auto- mobiles for the same operating conditions.

Approximately 80 percent of heavy trucks

are diesel-powered vehicles with three or more axles. Long-haul tractor-trailer vehicles constitute the majority of this group

which also includes dump trucks, cement

mixers, etc. Heavy truck noise is a combination of engine, fan, intake, exhaust, and

tire noises. However, extensive measure- ments of actual traffic conditions have

shown that heavy truck noise can be adequately simulated using only the exhaust

noise source and neglecting other sources

[3]. Based on this, the effective source location is assumed to be 8 feet above the pavement surface.* Thus, the major differences

between the sound generated by automobiles and medium trucks, and the sound

generated by heavy trucks are the magnitude and spatial location of the sound

source.

Geographically, the model assumes that the real highway configuration can be

approximated by a single "equivalent" lane

that is straight and infinitely long. It also assumes that this equivalent lane lies at grade on a level trerrain, which means that there is no shielding. The vehicles in each

group (automobiles, medium trucks and

heavy trucks) are considered to be traveling

at a constant speed characteristic of the

vehicle group. The model further assumes

that the noise generated by each of the vehicle groups can be characterized by the

traffic volume flow (vehicles/hour) and the

average speed (miles/hour) for that group.

Analysis of this idealized model shows that the noise of automobiles and medium trucks

increases with traffic volume and average

speed; and that the noise of heavy trucks

under the same conditions (for both the tire and exhaust sources) increases with traffic volume, but decreases slightly with an in- crease in average speed.

As far as propagation of the noise is concerned, the model assumes that the equivalent lane is an infinitely long line source

radiating uniformly into a half-plane (actually as many as three infinitely long, line sources, corresponding to automobiles, medium trucks and heavy trucks). The equivalent level of the noise propagated from

the highway decreases by an A-weighted

sound level of 4.5 dB for every doubling of distance from the roadway [3]. This value

of attenuation has been determined empirically, and includes losses due to air absorption and excess ground attenuation,

in addition to the usual cylindrical diver- gence associated with a line source. As was previously mentioned, the predicted

sound levels are conservately high in all but a few special cases, such as when the

ground plane is very reflective and no

shielding is present, or when the highway

is highly curved as shown in Figure 5.2-2.

In this latter case, the highway differs considerably from the model's assumption of an

infinitely long straight highway, and could be

treated as two separate highways. Assuming

* Exhaust stacks for heavy duty trucks are typi- cally about thirteen feet above the roadway. It is presumed that the authors of reference [3], in as- suming an eight-foot height for the noise source

of heavy trucks, were attempting to account for both tire noise (source near the roadway surface)

and exhaust noise (source approximately thirteen

feet above the roadway).
Figure 5.2-2. Example of a Highly Curved Higliway.

tine traffic volumes and average speeds are

the same for both portions of this highway,

the sound level at a receiver located inside

the curve vi^ould be at most 3 dB higher than

that predicted by the model. Hence, you can

conservatively estimate the sound level at the building site by adding 3 dB to the no- mogram value for a single highway. For a re- ceiver located outside the curved position of the highway, the model would overestimate

the sound level by an amount dependent on

the degree of curvature and the location of the receiver.

For cases other than the special case just

discussed, the nomogram will over-predict

the actual sound level by a few decibels depending upon the complexity of the real highway and the surrounding terrain rela- tive to the model's assumptions. Over-prediction may be excessive when there is a

vertical translation of the roadway to an

elevated or depressed position with respect

to the surrounding terrain. The effect of

this translation, as discussed in Section 1 of this chapter, is to shield the highway from

the building site in the same manner as a

barrier. Such effects are accounted for by subtracting the attenuation due to the

shielding from the predicted level. These

shielding adjustments are made in STEPS

H9, H10 and H11 of the highway noise pre- diction method which follows.

Before proceeding, you should briefly study

the flow diagram of Figure 5.2-3 which outlines the steps necessary to estimate highway noise. Starting at the top of the chart

and moving downward, you first obtain the required traffic, highway and roadway

shielding input data (STEPS H1 and H2).

Then using these data, calculate the sound

levels of automobiles, medium trucks, and

heavy trucks (STEPS H3 to H8); and the corrections for any barriers (STEPS H9 to H13). Following this, determine the total noise level due to this one highway by combining the contributions from the three vehicle groups (STEP H14). If there is more

than one highway near your site, repeat the previous steps for each of these highways

(STEPS H1 to H14). Finally, combine the

sound level contributions from all of the highways to get the total highway noise level

at your chosen building location (STEP

H15). All steps should be recorded on Highway Worksheets 1 and 2 shown in Figures

5.2-4 and 5.2-5. A detailed example showing

these step-by-step calculations is given in Section 5.5.
48

Highway Noise Prediction

I

Traffic Data

• Average Speed: SA, SM, SH

• Vefiicle Volume: VA, VM, VH

a) Leq(1): VA(1), VM(1), VH(1)

b) Leq{8): VA(8), VM(8), VH(8)

c) Leq(24): VA(24), VM(24), VH(24)

d) Ldn: DVA, DVM, DVH, NVA, NVM, NVH

STEPS H2.1 and H2.2

I

I

Highway Data

• Roadway—Building

Site Distance: DC

STEP H1.1

Highway Noise Nomogram

Leq(1), Leq(8), Leq(24), Ldn

• Autos

• Medium Trucks

• Heavy Trucks STEPS H3 to H8

1

Highway Shielding Data

• Barrier: DB, HB, hB, a

• Elevated Highway: DE, HE, a

• Depressed

Highway: DD, HD, hD, a

» Building Barriers: nr

• Vegetation: dw STEPS H1.2 and H1.3

Shielding Corrections

• Autos and Medium Trucks : CSA/M

• Heavy Trucks : CSH

STEPS H9 to H13

I

Railway Noise

Section 5.3

Highway Noise Level

• Leq(1) • Leq(24)

• Le<j(8) • Ldn STEP H14

Total Building I Site Noise Due to Several Highways STEP H15 ITotal Building

Site Noise Level Chapter 6

Aircraft Noise

Section 5.4

Figure 5.2-3. Highway Noise Prediction Flow Diagram.
Highway Worksheet 1

Building Project Highway Number

Location

Owner

Site point or building room for which sound pressure

levels are being estimated

Designer Date Revised

Roadway—Building Site Distance: DC (Feet)

Medium Trucks Heavy Trucks

Average Vehicle Speed, mph SA SH

Total Number of Vehicles

a) Leq(1)

Leq(1) No Shielding

Total Shielding Correction (Highway Worksheet 2)

Leq(1) Corrected for Shielding

Leq(8) No Shielding

b) Leq(8)

Total Shielding Correction (Highway Worksheet 2)

Leq(8) Corrected for Shielding

Leq(24) No Shielding

c) Leq(24)

Total Shielding Correction (Highway Worksheet 2)

Leq(24) Corrected for Shielding

HNL

RDN

CDN

d) Ldn

Ldn No Shielding

Total Shielding Correction (Highway Worksheet 2)

Ldn Corrected for Shielding

Total Highway Noise

Building Site Noise Due To Several Highways

Figure 5.2-4. Highway Worksheet 1.
Highway Worksheet 2

Building Project

Owner

Highway Number _

Site point or building room for which sound pressure

levels are being estimated

Designer

Date Revised

Roadway—Building Site Distance- DC (Feet)

Shielding Geometry

Path Length

Difference

Barrier

Elevated Roadway

Depressed

Roadway

DB HB hB a DE HE a DD HD hD a

Autos And Medium

Trucks

Heavy

Trucks

'a/m La/n

Figure 5.2-5. Highway Worksheet 2.
Highway Noise Prediction Method

STEP H1 PHYSICAL SITE DATA

The information that is required on the

highway geometry and the building site location can be obtained from local maps

as indicated in Chapter 2. The data should

be determined for each highway that you

have listed on the Preliminary Source

Evaluation Worksheet with a yes answer

in Column 2. The required data are:

1. Nearest perpendicular distance between the center of the roadway and

the selected location on the building

site, DC, in feet. See Figure 5.2-6 for an example of how DC is determined. Record this value on Highway Worksheet 1.

2. Location and geometry of any obstruction that visually shields the highway

from the building, in feet.

Median

Figure 5.2-6. Determination of Roadway

Building Site Distance, DC.

(a) Barrier linear dimensions. Be sure to note the sign convention for

tiB; positive below the plane of the road- way and neagtive above.

Highway

(b) Barrier included angle.

Figure 5.2-7. Highway Barrier Dimensions.
(a) Elevated highway linear dimensions.

Highway

AngI

Building

(b) Elevated highway included angle

Figure 5.2-8. Elevated Highway Dimensions.

(a) Depressed highway linear dimensions. Be sure to note the sign convention for hD;

negative below the top of the depression and positive above (different from barrier

notation).

Highway

End of Depressed

Highway

End of Depressed

Highway

(b) Depressed highway included angle

Figure 5.2-9. Depressed Highway Dimensions.
Determine if any barriers, elevated

roadways and depressed roadways are present and then obtain the appropriate distances as shown in Figures

5.2-7, 5.2-8 and 5.2-9, and listed below. Distances should be deter- mined as accurately as possible. If there is no shielding, omit this part of STEP H3 and all of STEPS H9, H10,

and H11.

Barrier: DC, DB, HB, hB, a

Elevated Roadway: DC, DE, HE, a Depressed Roadway: DC, DD, HD,

hD, a Note that the distances hB and hD

can be positive or negative; be sure

to record the appropriate sign on Highway Worksheet 2.

3. Presence of any rows of buildings or

belts of vegetation that shield thf building site from the roadway.

Refer to the discussion of Section 1 of this chapter to determine if there

is any significant shielding due to buildings or belts of vegetation. If there is, gather the appropriate data

listed below.

a) Buildings as Barriers: nr—number

of rows of buildings

b) Vegetation: dw—depth of woods

Record the value on Highway Worksheet 2.

STEP H2 HIGHWAY TRAFFIC DATA

The information that is required on highway vehicle traffic can be obtained from

the agencies listed in Chapter 2. These

data should be determined for each highway that you listed on the Preliminary

Source Evaluation Worksheet with a yes answer in Column 2. The values should

be the total for all lanes of the highway

and should be based on typical operating

conditions. Calculations are based upon

existing traffic volumes; but if you antici- pate changes, use future traffic volumes.

If you are unable to obtain information on medium trucks, neglect them and consider

only autos and heavy trucks. The required

data to be recorded on Highway Worksheet 1 are:

1. Average vehicle speed in miles per

hour: SA-auto; SM-medium truck; SH-heavy truck.

2. Average vehicle traffic volume In vehicles per hour: VA-auto; VMmedium truck; VH-heavy truck. The method of calculating the aver- age vehicle traffic volume depends

upon the noise criterion, or metric,

being used for your proposed building

be it Leqd), Leq(8), Leqf24), or Ldn.

Use the appropriate averaging method

listed below and obtain any additional

data necessary to make the calculations for the metric you are using.

• Leq(1), 1-hour energy equivalent

sound level Determine the total number of vehicles in each group that passes

by during the one selected hour of

critical building use; VA(1), VM(1),

VH(1). Since these values are al- ready on an hourly basis, no aver- aging is needed. Merely use these

traffic volumes directly in the nomogram prediction.

VA=VA{1); VM=VM(1);

VH=VH(1)

• Leq(8), 8-hour energy equivalent

sound level Determine the total number of vehicles in each group that passes

by during the eight hours of build- ing use; VA(8), VM(8), VH(8). The

average traffic volumes to be used

for the nomogram predictions are calculated by dividing the number

of passbys in eight hours by 8 to get the average number of vehicles

per hour.

VA=

VA(8)

VM=-

VM(8)

VH(8)

8

• Leq(24), 24-hour energy equivalent

sound level Determine the total number of vehicles in each group that passes

by on a typical day; VA(24), VM(24)

VH(24). The average traffic vol- umes to be used for the nomogram

predictions are calculated by divid- ing the total number of daily pass- bys by 24 to get the average number of vehicles per hour. VA=

VA(24)

24

VH=

VM =

VH(24)

24

VM(24)

24

'

• Ldn, Day-night sound level Determine the total number of vehicles in each group that passes

by during the "daytime" (7 A.M.

to 10 P.M.) and the "nighttime"
(10 P.M. to 7 A.M.); DVA, DVM,

DVH and NVA, NVM, NVH, respectively. The average traffic volumes

to be used for the nomogram

prediction are calculated by divid- ing the number of "daytime" pass- bys by 15 to get the average number of vehicles per hour.

DVM

VA=

DVA

15

VM=-

15

VH=-

DVH

l5~

Now you have the necessary input data for the prediction of highway noise. The complete graphical procedure for using the

Highway Noise Nomogram (shown in Figure

5.2-1) is outlined in the following steps. The

procedure must be performed three times, once for each vehicle group. Starting with

automobiles, the necessary input para- meters (for Highway Worksheet 1) are the

vehicle speed (SA), vehicle volume (VA) and

the roadway-building site distance (DC). Referring to Figure 5.2-1, the steps are:

STEP H3 NOMOGRAM PROCEDURE

Draw a straight line from the left pivot

point through the point corresponding to the vehicle speed (the bottom scale for autos and medium trucks and the upper

scale for heavy trucks). Extend this line

until it intersects with line A.

STEP H4 NOMOGRAM PROCEDURE

Draw another straight line from this point

of intersection on line A to the point on

the far right scale corresponding to the

vehicle traffic volume. This line inter- sects line B.

STEP H5 NOMOGRAM PROCEDURE

Draw a third straight line from the inter- section on line B to the point on the DC

scale corresponding to the distance from

the selected location on the building site to the center of the roadway. This line intersects the scale marked HNL. The

value of HNL at this point of intersection

is the predicted noise level if the metric

being used to evaluate the building is Leq(1), Leq(8) or Leq(24).

Leq(1) = HNL; Leq(8) = HNL;

Leq(24) = HNL

Record this value on Highway Worksheet

1 and continue the prediction procedures

omitting STEP H6. But if the day-night

sound level is being used, record HNL in the appropriate space on Highway Worksheet 1 and complete STEP H6.

STEP H6 DAY-NIGHT SOUND LEVEL

Compute the factor CDN, which is a correction for the relative number of "daytime" (7 A.M. to 10 P.M.) and "nighttime" (10 P.M. to 7 A.M.) vehicle passbys. It is determined from the ratio of the "daytime" vehicle traffic volume to the "nighttime" vehicle traffic volume,

RDN. (Data on vehicle traffic volumes are from Highway Worksheet 1.)

Vehicle Volume Ratio, RDN

Figure 5.2-10. Vehicle Volume Correction

Factor, CDN.

CDN is determined by locating on the

horizontal axis of Figure 5.2-10 the value

of RDN. Read up until intersecting the

curve. The value of CDN can be read off the vertical axis directly left of the inter- section. Using this value of CDN and the

value of HNL from STEP H5, calculate

Ldn from the following equation:

Ldn = HNL + CDN

Record this value on Highway Worksheet 1.

As mentioned previously, medium trucks are noisier than automobiles. If this differ- ence in noise level is taken into account,

the same scales that were used on the

Highway Noise Nomogram for the auto- mobile noise prediction can also be used

to predict medium truck noise. A method

of correcting for this difference in noise

level is given in STEP H7. After completing

STEP H7, proceed to STEP H8 and per- form the heavy truck noise prediction.
STEP H7 MEDIUM TRUCKS

To account for the difference in noise

level between automobiles and medium

trucl<s, a corrected medium trucl< volume

is used. This corrected vehicle traffic volume, VMC, is equal to the actual volume, VM, multiplied by ten. VMC = 10VM

Record this value on Highway Worksheet

1. Now repeat STEPS H3, H4 and H5

(also STEP H6 if Ldn is the metric being

used) using the values SM, VMC, and

DC. In repeating the nomogram proce- dure remember to use the lower scale of vehicle speeds for medium trucks.

STEP H8 HEAVY TRUCKS

Heavy truck noise is determined by re- peating STEPS H3, H4 and H5 (also STEP

H6 if Ldn is the metric being used) using

the values SH, VH and DC from Highway

Worksheet 1. In repeating the nomogram

procedure remember to use the upper

scale of vehicle speeds for heavy trucks. *****

STEPS H1 through H8 assumed that there was no obstruction, or shielding, between

the highway and the building site. If there is any shielding due to a barrier, elevated roadway, depressed roadway, rows of buildings or a belt of vegetation, it should be taken

into account. This is done in STEPS H9 to H13.

The corrections for Shielding due to barriers and elevated or depressed highways

are related to the effective sound source

heights for the three vehicle groups. The

effective sources are assumed to be near

the roadway surface for autos and medium

trucks, and eight feet above the roadway

surface for heavy trucks. Thus, there are two corrections; one for autos and medium

trucks, CSA/M, and one for heavy trucks,

CSH. These corrections are determined by

calculating the path length differences from

the equations listed in STEP H9 for the type

of shielding that is present. Using these

values of L, CSA/M and CSH are determined

in STEP H10 for an "infinite" shielding ele- ment or in STEP H11 for a finite shielding

element.

The shielding corrections for rows of build- ings which act as barriers and for vegetation are related to the physical layout of the highway, the site, and building. The

correction for the shielding due to rows of buildings which act as barriers, CSB, is computed in STEP HI 2. The correction for the shielding due to vegetation, CSV, is computed in STEP HIS. Note that the attenuation

due to rows of buildings which act as barriers, and to vegetation is added to any at- tenuation due to barriers and elevated or depressed highways. For example, if the A-weighted sound level attenuations of a barrier, two rows of buildings, and 100 feet of dense woods are 5, 6, and 5 dB, respectively,

the total A-weighted sound level attenuation is 16 dB.

After these shielding corrections are applied, the individual component sound lev- els are calculated. Then, these are combined to get the total highway noise in STEP H14.

If there is no shielding present, the noise

levels calculated in the previous steps are

the values to be used to predict noise levels

in your building and on the site. Omit STEPS

H9 to HIS and proceed to STEP H14 to get

the total noise due to the highway.

STEP H9 PATH LENGTH DIFFERENCE

Compute the path length difference for autos and medium trucks, La/m, and

for heavy trucks, Lh, for the type of shielding present. Be sure the obstruction blocks the line-of-sight between the source and receiver, in particu'ar for heavy trucks which have the source

located eight feet above the road surface.

If the line-of-sight is not blocked, the

correction is zero.

1. Barrier: Aa/m = y/HB^ + (DC - DB)'

Ah = V(HB - 8)' + (DC - DB)^

Ba/m = Bh = y'{HB + hSy + DB'

Ca/m = VhB' + DC'

Ch = V(hB + 8)' + DC

2. Elevated Highway:

Aa/m = [DC - DE]

Ah = V64 + (DC - DE)'

Ba/m =r Bh = V HE' + DE' Ca/m = \/HE' -f DC

Ch = V(HE + 8)' + DC

S. Depressed Highway:

Aa/m = VHD' + (DC - DD)'

Ah = V(HD - 8)' + (DC - DD)'

Ba/m = Bh = ^hD' + DD' ~ Ca/m = V(HD + hD)' -f DC'

Ch = V(HD + hD - 8)' + DC

From these values the path length differ- ences are calculated from the following

equations.

La/m = Aa/m -I- Ba/m — Ca/m

Lh = Ah + Bh - Ch

Record these values on Highway Worksheet 2 and proceed to the next step.
STEP H10 SHIELDING CORRECTION—

"INFINITELY" LONG

BARRIER

Compute the shielding corrections CSA/M

and CSH. These values are determined

from the path length differences cal- culated in the previous step [4]. If the

path length difference is less than 0.1 ft or is negative, there is no significant

shielding and the correction is zero. But

if the path length difference is positive

and greater than 0.1 ft, the shielding correction is determined by locating on the

horizontal axis of Figure 5.2-11 the value

of the path length difference. Read up

until intersecting the curve. The value of the shielding correction can be read off the vertical axis directly left of the inter- section. This procedure is followed using

La/m to determine CSA/M and Lh to determine CSH. Record these values on Highway Worksheet 2. If the included

angle, a, is less than 170° the shielding

element is of "finite" length, and you must

proceed to STEP H11. But if the included

angle, a, is greater than 170°, no adjustment to the shielding corrections is needed. Omit STEP H11 and continue the

design guide analysis.

I T > I I I TTJ 1 1 1 1 1 III

1

1—1 1 1 1 II

1 1 1 1 1 1 1 1 ITDesign Guide

Approximation

1 f ) 1 1

1

.. 1 1 1 1 1 M 1 1

1 1 1 1 Ml 1 1 1 t 1 J.JJJI

20

<O 15

? 10

0.01 0.1 1.0 10.0 100.0

Path Length Difference, L, Feet

Figure 5.2-1 1 . A-weighted Shielding Correction for Barriers.
57 STEP H11 SHIELDING CORRECTION—

"FINITE" BARRIER

Compute the adjusted values of CSA/M

and CSH to account for shielding ele- ments of "finite" length. These adjusted

shielding corrections are determined from

the factor RA, which is calculated from

the included angle, a (in degrees), using

the following equation:

Now go to Table 5.2-1 and enter the first column at the value of CSA/M and read across that row to the column corre- sponding to the value of RA. This is the

adjusted value of CSA/M. Repeat this procedure using the value of CSH to get

the finite shielding correction for heavy

trucks. Record these adjusted shielding

corrections on Highway Worksheet 2 and

continue the design guide analysis.

Table 5.2-1. Shielding Corrections for a Finite Barrier.

"Infinite" Barrier Shielding Correction CSA/M or CSH

RA = a/180°

0 .1 .2 .3 .4 .5 .6 .7 .8 .9 1.0

1 0 0 0 0 0 0 1 1 1 1 1

2 0 0 0 1 1 1 1 1 2 2 2

3 0 0 0 1 1 1 2 2 2 3 3

4 0 0 1 1 1 2 2 2 3 3 4

5 0 0 1 1 1 2 2 3 3 4 5

6 0 0 1 1 2 2 3 3 4 5 6

7 0 0 1 1 2 2 3 4 4 6 7

8 0 0 1 1 2 2 3 4 5 6 8

9 0 0 1 1 2 3 3 4 5 7 9

10 0 0 1 1 2 3 3 4 6 7 10

11 0 0 1 1 2 3 3 4 6 8 11

12 0 0 1 1 2 3 4 5 6 8 12
STEP H12 SHIELDING CORRECTIONBUILDINGS ACTING AS

BARRIERS

Calculate the correction, CSB, for rows

of buildings which shield the highway

from your building site. This correction

depends on the number of rows of inter- vening buildings, nr, and is determined

from Table 5.2-2. Record this correction on Highway Worksheet 2 and continue the design guide analysis.

Table 5.2-2. Shielding Corrections for Buildings Acting as Barriers [4].

Table 5.2-3. Level Adjustment for Summing Noise Levels.

Difference Level Adjustment

Between (To Be Added To

Two Noise The Larger of The

Levels, dB Two Values)

10 or more 0

4-9 1 2-3 2

0-1 3

Number of Rows

Shielding

Correction, CSB

12

3

4

5 or more

4.5

6.0

7.5

9.0 10.0

to the larger of the two original noise

levels. Now repeat this procedure with

this adjusted level and the noise level

for heavy trucks. The result of this combination is the total noise at the building

site due to this (one) highway. For ex- ample, if the A-weighted sound levels for autos, medium trucks and heavy trucks

are 55, 55, and 60 dB respectively, the

total noise due to this highway is,

STEP H13 SHIELDING CORRECTIONVEGETATION

Calculate the correction, CSV, for a belt

of vegetation of depth dw, which shields

the highway from your building. This

correction is simply an A-weighted sound

level attenuation of 5 dB for the first 100

feet of woods and 10 dB for woods over 200 feet in depth. Interpolation between

these values is left to your discretion.

Record the correction on Highway Worksheet 2 and continue the design guide

analysis.

STEP H14 TOTAL HIGHWAY NOISE

Compute the total noise at the building

site due to the highway. First, sum

the shielding corrections on highway

Worksheet 2 for each vehicle group and

record these values on Highway Worksheet 1. Subtract these total shielding

corrections from the unshielded noise

levels to get the individual components

at the building site. Since these levels are

logarithmic in nature, they cannot be simply added together or averaged to get the

total noise level. Instead, they are combined, two values at a time, with the use

of Table 5.2-3. Starting with the auto and

medium truck noise levels, subtract one

from the other to get the difference. With

this value go to Table 5.2-3 and determine

the level adjustment which is to be added

55^

55'

60-

diff. ==0

add 3

58

diff. = 2 add 2 62 dB.

Record the total noise level on Highway

Worksheet 1.

This completes the prediction of highway

noise. These procedures should be repeated

for each highway that is listed on the Preliminary Source Evaluation Worksheet with a yes answer in Column 2. The total noise at the building site due to all highways is the

logarithmic summation of the noise contri- butions from each highway. This computation is performed in STEP H15.
59 STEP H15 TOTAL NOISE LEVEL DUE

TO SEVERAL HIGHWAYS

The total noise level at the building site you have selected is determined by summing the components from all highways

affecting your site. Summing is done two

values at a time, by the same method as used in STEP H14. (Refer to this step for the procedure of summing noise levels.)

Record this value on Highway Worksheet 1.

Now proceed to Sections 5.3 and 5.4 to predict the noise levels due to railways and

aircraft. If these two transportation system

noise sources do not affect your building

site, proceed directly to Chapter 6.

References

Chapter 5 Section 2 Highway Noise

[1] Gordon, C. G., Galloway, W. J., Kugler,

B. A., and Nelson, D. L., Highway noise

a design guide for highway engineers,

NCHRP Report 117 (Bolt Beranek and

Newman Inc., Los Angeles, California

1971). Available from the Highway Re- search Board, 2101 Constitution Ave., Washington, D.C. 20418.

[2] Wesler, J. W., Manual for highway noise

prediction, U.S. Department of Transportation Report No. DOT-TSC-FHWA-72-1

(Department of Transportation, Transportation Systems Center, Cambridge,

Mass., March 1972). Available from the National Technical Information Service,

Springfield, Virginia, Accession Nos. PB

226-086, PB 226-087 and PB 226-088.

[3] Kugler, B. A., Commins, D. E., and Gallo- way, W. J., Establishment of standards

for highway noise levels: Volume 1 —Design guide for highway noise prediction

and control, BBN Report No. 2739 (Bolt

Beranek and Newman Inc., Los Angeles,

California, February 1974).

[4] Kugler, B. A., and Piersoi, A. G„ Highway noise: a field evaluation of traffic noise reduction measures, NCHRP Report 144 (Bolt Beranek and Newman Inc., Canoga Park, California, 1973). Avail- able from the Highway Research Board,

2101 Constitution Ave., Washington, D.C. 20418.

Chapter 5

Section 3

How to Estimate

Railway

Passby Noise

Railroad operations can be classified as

either line operations or yard operations.

Line operations are movements of trains of various types over main line and local track; yard operations are the various

activities concentrated in a railway ter- minal. Railroad yard operations generate

noise through the disassembling and

recoupling of cars to form new trains,

and the maintenance and repair of cars and locomotives. Although a limited amount

of research has been devoted to the modeling of noise phenomena in railroad yards, the models are complex since there are so many different types of sound sources operating for various lengths of time on an inter- mittent basis [1, 2], thus making it very

difficult to predict the noise that is generated. For this reason railroad yard noise

will not be treated in this design guide.

Railway line operations are a much more common source of railroad noise than yard

operations. The noise generated by train passbys is a function of the type of vehicle

in use, how it is operated, and the configuration of the trackbed relative to the sur- rounding terrain. Although there has been

a fair amount of research devoted to the modeling of railway line passbys [1-5], there

is still much to be learned. Unlike highways,

which have been the subject of a great deal more research than railways, no simple

nomogram method for predicting passby

noise has been developed.

The analytical model * which is used in this design guide for predicting railway noise

considers four general types of vehicles as

noise sources: locomotives, freight cars, passenger coaches, and rapid transit vehicles. These vehicles, either in combination with one of the other types or by themselves, form three general train categories.

These are freight trains, conventional pas- senger trains, and rapid transit trains. A

freight train consists of one or more locomotives, usually diesel-electric, pulling a combination of various types of freight cars. A conventional passenger train is similar to a freight train in that it consists of one or more locomotives pulling several coaches,

but one important difference is that the loco-

* The railway noise model is based on work per- formed by Wyle Laboratories. El Segundo. California, under the sponsorship of the Association

of American Railroads, Washington, D.C. [1]. The

design guide's technique for predicting the generated noise levels is modified slightly to include more recently published data and to simplify the necessary calculations.
motive may either be diesel-electric or all electric* The third type, rapid transit trains, differs from the other two types in that there

is not a centralized source of propulsion

pulling a series of cars, but rather electric motors on the axles of each car. There is a wide variety of different types of vehicles

which can be classified as rapid transit

trains. As a result, some of the newer vehicles may be quieter than predicted by the

methods of this design guide. Also, the prediction procedures are not applicable to underground subway operations or "classic"

street cars.

A diesel-electric locomotive utilizes a diesel

engine driving an electrical alternator or generator which in turn drives electric traction motors on the wheels. An all-electric locomotive, on the other hand, obtains its electrical power from an external source, normally an overhead line or third rail, to drive its traction motors. The vast majority

of trains in the United States are hauled by

diesel-electric locomotives—as of 1971,

99% of the 27,000 locomotives in service were diesel-electric, with most of the re- mainder being all-electric [6].

For noise propagation, the model assumes

locomotive is a combination of sounds

radiated from the exhaust outlet, the engine

casing, the cooling fans, the transmission,

the electrical equipment, and the interaction

of the wheels and rails—the predominant

source of noise is the exhaust outlet. Hence,

ail-electric locomotives, which have no

diesel engine and thus no exhaust, are generally quieter than diesel-electric locomotives.

Having no propulsion system, freight cars and passenger coaches generate noise

mainly by the rolling of the wheels on the

rails. The magnitude of the noise depends

heavily on the condition of the wheels and

track, and on the type of vehicle suspension. Modern passenger coaches with

auxiliary hydraulic suspension systems in addition to normal springs can be about

10 dB quieter than older passenger coaches

or freight cars which have only springs.

The noise of rapid transit trains, even

though there are electric motors on each

axle that are sources of noise, is also pre- dominantly generated by the interaction of the wheels upon the rails. In fact, because

rapid transit vehicles are usually newer and

have better suspension systems, they are

• There are also gas turbine locomotives, but

these are few in number and will not be con- sidered herein.

generally quieter than freight cars or pas- senger coaches.

Geographically, the predictive model as- sumes that the real railway configuration can be approximated by a single "equivalent" track that is straight and infinitely long.

It also assumes that this "equivalent" track

lies at grade on a level terrain, which means

that there is no shielding. The model fur- ther assumes that the trains that use this track can be grouped into one of the three

general categories (freight, conventional

passenger, or rapid transit) and that each

of these categories can be characterized

by an average speed, an average train length, and an average number of passbys

for normal operating conditions.

Freight train noise is analyzed by considering two distinct sources: the diesel-electric

locomotive and the freight cars; but conventional passenger trains and rapid transit trains are considered to generate noise primarily through wheel-rail interaction. This means that for conventional passenger trains the locomotive is assumed to be all-electric. Hence, if the conventional passenger train locomotives are diesel-electric a locomotive

noise component must be added.

For noise propagation, the model assumes

that diesel-electric locomotive equivalent

sound level decreases by an A-weighted

value of 5.3 dB for every doubling of distance from the railway. The equivalent

sound level from freight cars, passenger

coaches, and rapid transit vehicles is as- sumed to decrease by an A-weighted sound

level difference of 6.2 dB for every doubling

of distance from the railway. These two

values of attenuation are applicable only for distances greater than 150 feet from the rail- way, but it is not anticipated that your

building or site would be 150 feet or closer

to a railway. The values were determined

empirically and include corrections for attenuation due to spreading of the sound waves (divergence), increased duration of the noise at points farther away from the

railway, air absorption, and excess ground

attenuation [1].

As mentioned previously, the model as- sumes that the railway lies at grade on a

level terrain. If the railway is either elevated

or depressed relative to the surrounding

terrain, the effect may be to shield the rail- way from the building site in the same

manner as a barrier. Such effects are taken

into account by substracting the attenuation due to the shielding from the predicted

level. These shielding adjustments are made

in STEPS R11, R12 and R13.
61

Railway Noise Prediction

Train Data

• Types of Trains: Freight, Conventional Passenger, Rapid Transit

• Type of Locomotive:

Diesel-Electric, All-Electric

• Average Speed: S

> Average Lenglfi: LT

• Average Number of Passbys:

a) Leq(1): N1

b) Leq(8): N8

c) Leq(24): N24

d) Ldn: ND, NN

STEP R2

I

Track Data

• Railway-Building

Site Distance: D

• Track Cfiaracteristics STEPS R1.1 and R1.2

I

Predict Diesel-Electric Locomotive Noise Reference Level : LS

. Distance Atteniiation: DAL

• Unsfiielopd fJO'Se Level STEPS R3, ,ind R5

Predict Railway Car

Noise

• Reference Level: CL

• Duration Factor: CD

, Track Characteristics: CT

. Distance Attenuation: DAC

• Unshielded Noise Level STEPS R6 to RIO

Railway Shielding Data

. Barrier: DB. HE, hS, ; • Elevated

Railway: DE, HE, a

. Depressed

Railway: DD, HD, hD^

• Building

Barriers: nr

• Vegetation : dw STEPS R1.3 and R1.4

Shielding Corrections

• Railway Cars : CSC

> Diesel-Electric Locomotive : CSL STEPS R11 to R15

Total Railway Noise

At Buildmg Site Leq(1), Leq(8), Leq(24), Ldn STEP R16

Highway Aircraft Noise Total Building Site Noise Noise

Section 5.2 Chapter 6 Section 5.4

Figure 5.3-1 . Railway Noise Prediction Flow Diagram.
Railway Worksheet 1

y//////////////^

Building Project

Location

Owner

Railway Number

Site point or building room for which sound pressure

levels are being estimated

Designer Date Revised

Railway—Building Site Distance: D (Feet).

Freight Trains

Conventional Passenger Trains Rapid Transit Trains Does this type of train use

the tracl< being analyzed?

Diesel-Electric ,or All-Electric Locomotive

NL NL

Average Train Speed, S, mph

Average number of cars, nc

Average train length, LT, feet

Average Number of Passbys

a) Leq(1) : N1

b) Leq(8) : N8

c) Leq(24) : N24

Railway Cars

Reference Level, CL

Duration Factor, CD

Track Characteristics, CT

Distance Attenuation, DAC

Predicted Noise Levels

Diesel-Electric Locomotive

Railway

Cars

Diesel-Electric LocomotiveRailway

Cars Railway Cars

a) Leq(1)

CI

Leq(1) No Shielding

Total Shielding Correction (Railway Worksheet 2)

Leq(1) Corrected for Shielding CN8

cs

b) Leq(8) Leq(8) No Shielding

Total Shielding Correction (Railway Worksheet 2)

Leq(8) Corrected for Shielding CN24

024

c) Leq(24) Leq(24) No Shielding

Total Shielding Correction (Railway Worksheet 2) Leq(24) Corrected for Shielding CNCDN

d) Ldn

Ldn No Shielding

Total Shielding Correction (Railway Worksheet 2) Ldn Corrected for Shielding

Total Railway Noise V/////////////////////////A

Figure 5.3-2. Railway Worksheet 1
Railway Worksheet 2

Railway hjumber

Building Pro|ect

Site point or building room for which sound pressure

levels are being estimated

Location Designer Owner Date Revised

Shielding Geometry

Barrier Elevated

Railvi/ay

Depressed

Railway

DB HB tiB a DE HE a DD HD hD a

Railway—Building Site Distance: D (Feet),

Path Length

Difference

Railway

Cars

Ac

DieselElectric Locomotive

A/

Be

8/

Cc

CI

Lc

Railway Cars Diesel-Electric Loc.

Correction For

"Infinite" Shielding Element CSC CSL

Included Angle Ratio, RA

Correction Foi "Finite" Shielding Element

Railway Cars

CSC

Building Barrier

Diesel-Electric Loc.

CSL

CSB

Vegetation CSV

Railway Cars Diesel-Electric Loc.

Total Shielding Correction CSC + CSB + CSV CSL + CSB + CSV

Track Characteristics

a b c d

Presence of Switching Frog

or Grade

Crossing

Radius of Bridgework Welded

Track

Jointed Track

Tight Curve « 900 Feet)

in Feet

Concrete

Structure

Steel Girder

with Concrete

or Open Tie Deck

Steel Girder

with Steel Plate Deck

Figure 5.3-3. Railway Worksheet 2.
Before proceeding, you should briefly study

the flow diagram of Figure 5.3-1 which outlines the steps necessary to estimate railway

noise. Starting at the top of the chart and

moving downward, you will first obtain the

required train, track and railway shielding

input data (STEPS R1 and R2). Then using

these data, you will calculate the sound

levels corresponding to the diesel-eiectric

locomotive and railway car components of the three types of trains affecting your site (STEPS R3 to R10). Then you will make

shielding corrections (R11 to R15) for any

barriers. Following this you will determine

the total noise level due to this railway by

combining the contributions from its various

components (STEP R16). All steps should be

recorded on Railway Worksheets 1 and 2 shown in Figures 5.3-2 and 5.3-3. A detailed

example showing the step-by-step calculations is given in Section 5.5. Railway Noise Prediction Method

STEP R1 PHYSICAL SITE AND TRACK

DATA

Information on railway geometry and track

characteristics can usually be obtained

from area maps and the appropriate department of the railway company as dis- cussed in Chapter 2. The data should be

obtained for each railway that is listed on the Preliminary Source Evaluation

Worksheet with a yes answer in Column

2. The required data are:

1. Nearest perpendicular distance between the centerline of the railway

and the point you have chosen for analysis on the building site, D, in feet. See Figure 5.3-4 for an example of how D is determined, and record this value on Railway Worksheets 1 and 2.

2. The physical characteristics of the

track:

a. Type of track: welded or jointed

b. Presence of switches or grade

crossing

c. Radius of tight (less than 900 feet) curve in feet

d. Presence of a bridge

• concrete structure

• steel girder with either concrete

or open tie deck

• steel girder with steel plate deck

A switch, grade crossing, tight radius

curve, or bridge should only be considered when it is located within a

distance of 2D on either side of the

point of intersection of the railway

with the nearest perpendicular dis- tance. See Figure 5.3-4 for an illus- tration of this distance requirement.

Record this information on Railway

Worksheet 2.

3. Location and geometry of any obstruction that visually shields the railway

from the building, in feet Determine if any barriers, elevated

railways, or depressed railways are

present, and then obtain the appropriate distances as shown on Figures

5.3-5, 5.3-6 and 5.3-7 and listed below.

Distances should be determined as accurately as possible. If there is no

shielding, omit this part of STEP R1

and all of STEPS R11, R12 and R13.

Barrier: D, DB, HB, hB, a Elevated Railway: D, DE, HE, a Depressed Railway: D, DD, HD, hD, a Note that the distances hB and hD

can be positive or negative; be sure

to record the appropriate sign on

Railway Worksheet 2.

Figure 5.3-4. Railway-Building Site

Distance, D.
65 4. Presence of any rows of buildings or

belts of vegetation that shield your

building site from the railway

Use the criteria discussed in Section

5.1 to determine if there is any sig- nificant shielding due to buildings or

belts of vegetation. If there is, gather

the data listed below.

a) Buildings as Barriers: nr—number

of rows of buildings

b) Vegetation: dw—depth of woods

Record these values on Railway Worksheet 2.

Barrier [sign

I ^ DB ^

!

I

1^ D ^

(a) Barrier linear dimensions. Be sure to note the sign convention for hB; positive

below the plane of the railway and negative above

.

Railway 1—1 I—II—II—II—II—IT—ir-il—II—If—II—If—1|—II—

I

——hfH-i-H-4+i-M -^--l-^l-+^l-+^H--^^-M^-^^^ —I I 1—1—c^i

I I i_j 1—I i_i—en—CZI—L_J l_I I I i_i

CD—

Barrier

Building

(b) Barrier included angle.

Figure 5.3-5. Dimensions for Shielding by a Railway Barrier.
66

—l-H^I+[+4-H-^h+H-h+f+fM + l-l-l+l4i4H+H—

LJ 1 I O—LJ LJ—LJLJLJl ILJLJLJ L_J—L_J L_J LJ L_l LH

dJ

(b) Elevated railway included angle.

Figure 5.3-6. Dimensions for Shielding By an Elevated Railway.
67

(a) Depressed railway linear dimensions. Be sure to note the sign convention for hD;

negative below the top of the depression and positive above—different from barrier

notation.

Figure 5.3-7. Dimensions for Shielding By a Depressed Railway.
STEP R2 TRAIN DATA

The information that is required on trains can be obtained from the agencies listed

in Chapter 2. These data should be

gathered for each railway listed on the

Preliminary Source Evaluation Worksheet

with a yes answer in Column 2. The

values should be the average for all tracks and should be based on typical

operating conditions. The required data

to be recorded on Railway Worksheet 1 are:

1. Types of trains which normally use the

track.

If there are no freight trains, or no

conventional passenger trains, or no

rapid transit trains write "NONE" in the appropriate space on Railway

Worksheet 1 for that train type.

2. Type of locomotive which normally

is used to pull the train: diesel-electric or all-electric. This information on

locomotions is only needed for freight

trains or conventional passenger trains.

If this information is not readily avail- able, assume the locomotive to be

diesel-electric since this is the pre- dominant type, and the worst case

acoustically. Also determine the aver- age number of diesel-electric locomotives, NL, used to pull the train.

3. Average train speed, S, in miles per hour for each type of train.

4. Average train length, LT, in feet for each type of train.

If the average length is not available,

determine the average number of cars,

nc, in the train. The length is then

obtained by multiplying nc by 55 feet

for freight cars and by 75 feet for passenger coaches and rapid transit vehicles [7].

5. Average number of passbys for each

type of train. The time period for which the typical

number of operations is determined

depends upon the metric being used

for the noise criterion for your pro- posed building: Leq(1), Leq(8), Leq

(24), or Ldn. Obtain only the data

required to calculate the metric you

are using.

• Leq(1)

Determine the average number of passbys during the one selected

hour of critical building (or outdoor

activity area) use, N1.

• Leq(8)

Determine the average number of passbys during the eight hours of building use, N8.

• Leq(24)

Determine the average number of passbys during a typical twentyfour hour day, N24.

• Ldn

Determine the number of passbys

during the "daytime" (7 A.M. to 10 P.M. and the "night time" (10 P.M. to 7 A.M.), ND and NN, re- spectively.

Now you have the necessary input data for the prediction of railway noise. This prediction, outlined in the following steps,

consists of determining various factors

which are combined to give the estimated

noise level. The factors are based on the railway model discussed previously and are normalized to a reference distance of one- hundred feet. Noise levels for the idealized

model are then corrected to account for actual conditions. Computations are simplified as much as possible by graphs, charts,

and tables.

The remainder of this section is divided

into four separate subsections. Subsection

A contains the directions for estimating the unshielded noise level of freight trains, conventional passenger trains and rapid transit

trains. Subsection B contains the predictive

steps for calculating diesel-electric locomotive noise and railway car noise. Shielding

adjustments are made in subsection C; and

in subsection D, separate noise contributions are combined to get the total railway

noise.

Your approach should be to use Subsection

A to determine which steps of the noise

production computations you must perform.

Estimate the unshielded noise level for diesel-electric locomotives and cars in B. Then

in C, estimate the shielding corrections, if any, and finally, in D combine the noise

levels generated by each type of train to get

the total railway noise at your building site. Record the calculated values on Railway

Worksheets 1 and 2 as directed.
A. Steps for Predicting Railway

Noise

Freight Trains

Freight train noise has two distinct components: diesel-electric locomotive noise and

freight car noise. These two components

must be treated separately. Follow STEPS

R3, R4 and R5 to get the locomotive component, and STEPS R6 through R10 to get

the car component. Use the appropriate

input data from Railway Worksheet 1 for freight trains.

Conventional Passenger Trains

Conventional passenger train noise depends

upon the type of locomotive. If it is all- electric, treat the locomotive as another

passenger coach and perform STEP R7

through RIO.

if diesel-electric locomotives are the pre- dominant type, a locomotive component

must be included. Perform STEPS R3, R4

and R5 to get the locomotive component,

and STEPS R6 through RIO to get the car component. Use the appropriate input data

from Railway Worksheet 1.

Rapid Transit Trains

Rapid transit train noise is predominantly

wheel-rail noise, with no locomotive component. Perform STEPS R6 through RIO

using appropriate input data from Railway

Worksheet 1.

B. Noise Prediction Calculations

STEP R3 DIESEL-ELECTRIC LOCOMOTIVES—REFERENCE LEVEL

Compute the factor LS for the dieselelectric locomotives at the reference dis- tance of 100 feet from the centerline of the railway. LS is determined by locating on the horizontal axis of Figure 5.3-8, the speed, S, for this type of train. Read up

until intersecting the curve. The value of LS can be read off the vertical axis di- rectly left of the intersection.

Figure 5.3-8. Diesel-Electric Locomotive Reference Level, LS, at 100 feet [1].
70 STEP R4 DIESEL-ELECTRIC LOCOMO- DAL is determined by locating on the

TIVES—DISTANCE ATTEN- horizontal axis of Figure 5.3-9 the dis- UATION tance, D. Read up until intersecting the curve for the locomotive correction. The

Compute the distance attenuation factor, value of DAL can be read off the vertical DAL for diesel-electric locomotive noise. axis directly left of the intersection.

Railway —Building Site Distance, D(feet)

Figure 5.3-9. Railway Noise Attenuation With Distance [1].

STEP R5 DIESEL-ELECTRIC LOCOMOTIVES—UNSHIELDED

NOISE LEVEL

Perform the calculations appropriate for the noise criterion, or metric, for your pro- posed building. Record all values on Rail- way Worksheet 1. Leq(1)

Compute CI, which is a correction for the

number of passbys during the selected

hour of critical building use. CI is deter- mined from the total number of passbys,

CN1, defined as, CN1 = N1 X NL,

where N1 is the average number of pass- bys for this type of train during the se- lected hour, and NL is the average number of diesel-electric locomotives pulling the train. On the horizontal axis of Figure

5.3-10 locate the value of CN1 for this type of train. Read up until intersecting

the curve. Read the value of CI from the

vertical axis directly left of the intersection. Using this value and the values of LS and DAL, calculate Leq(1) from the

following equation:

Leq(1) = LS + C1 - DAL - 36. Leq(8)

Compute C8, which is a correction for the

number of passbys during the eight hours

of building use. It is determined from the

total number of passbys, CN8, defined as, CN8 = N8 X NL. where N8 is the average number of pass- bys by this type of train during the eight

hours, and NL is the average number of diesel-electric locomotives pulling the

train. Locate on the horizontal axis of Figure 5.3-10, the value of CN8 for this type of train. Read up until intersecting

the curve. Read the value of C8 from the

vertical axis directly left of the intersection. Using this value and the values of LS

and DAL, calculate Leq(8) from the fol- lowing equation:

Leq(8) = LS + C8 - DAL - 45.
1 10 Number of Passbvs N(1), N(8), N(24) or CN

100

Figure 5.3-10. Correction for the Number of Passbys.

Leq(24)

Compute C24, which Is a correction for the number of passbys during a twentyfour hour day. It is determined from the

total number of passbys, CN24, defined as, CN24 = N24 X NL,

where N24 is the average number of pass- bys by this type of train during the twentyfour hours, and NL is the average number

of diesel-electric locomotives pulling the

train. Locate on the horizontal axis of Figure 5.3-10 the value of CN24 for this type of train. Read up until intersecting

the curve. Read the value of C24 from

the vertical axis directly left of the inter- section. Using this value and the values

of LS and DAL, calculate Leq(24) from the

following equation:

Leq(24) = LS + C24 - DAL - 49. Ldn

Compute CDN, which is a correction for the number of "daytime" and "nighttime"

passbys. It is determined from the cor- rected number of passbys, CN, defined as CN = (ND + 6NN) NL

where ND is the number of "daytime", and

NN is the number of "nighttime" passbys

for this type of train, and NL is the aver- age number of diesel-electric locomotives

pulling the train. Locate on the horizontal

axis of Figure 5.3-10 the value of CN.

Read up until intersecting the curve. Read

the value of CDN from the vertical axis

directly left of the intersection. Using this value and the values of LS and DAL, cal- culate Ldn from the following equation:

Ldn = LS + CDN - DAL - 49.

STEP R6 RAILWAY CARSREFERENCE LEVEL

Compute the factor CL at the reference

distance of 100 feet from the centerline of the railway. CL is determined by locating on the horizontal axis of Figure 5.3-11 the

speed, S, for this type of train. Read up

until intersecting the appropriate curve

for this type of railway car. The value of CL can be read off the vertical axis di- rectly left of the intersection.

STEP R7 RAILWAY CARS—PASSBY

DURATION

Compute the passby duration factor CD.

CD is determined by locating on the hori- zontal axis of Figure 5.3-12 the train length, LT, for this type of train. Read up

until intersecting the curve corresponding

to the speed, S, for this train category.

The value of CD can be read off the verti- cal axis directly left of the intersection.
7" \ 1 1

\—I I I I I I I I I I

C I I I \ \ I I I I I I I I I 1 I 11

10 20 30 40 50 60 70 80 90 100

Average Train Speed, S (MPH)

Figure 5.3-11. Railway Car Reference Level at 100 feet [2].

100 1000 10,000 Average Train Length, LT, feet

Figure 5.3-12. Duration Correction for Train Passbys.
STEP Rd RAILWAY CARS—TRACK

CHARACTERISTICS

Compute the track adjustment factor, CT.

This factor accounts for track characteristics other than the standard, straight,

mainline, welded track [1, 4, 8]. This adjustment should be made only if the track

variation occurs within a distance of 2D

on either side of the point of Intersection

of the railway with the nearest perpendicular distance. See Figure 5.3-4 for an

illustration of this distance requirement.

From Table 5.3-1 select the appropriate

value of CT corresponding to the physical

characteristics of the track segment under

investigation. In case of simultaneous oc- currence of these variations the single

largest correction should be used.

STEP R9 RAILWAY CARS—DISTANCE

ATTENUATION

Compute the distance attenuation factor,

DAC, for railway car noise. DAC is deter- mined by locating on the horizontal axis

of Figure 5.3-9 the distance D. Read up

until intersecting the appropriate curve

for railway cars. The value of DAC can be

read off the vertical axis directly left of the intersection.

Table 5.3-1. Adjustment Factors for Track

Characteristics [1, 4, 8].

TRACK CHARACTERISTICS CT

1 Straight, Mainline, Welded 0

Track

2 Straight, Jointed Track 4

3 Presence of Switches or 4

Grade Crossing

4 Tight Radius Curve

Radius < 600 Ft. 4

Radius 600 Ft. to 900 Ft. 1

Radius > 900 Ft. 0

5 Presence of a Bridge

Concrete 0

Steel Girder with Either Con- 5

Crete or Open Tie Deck

Steel Girder with Steel Plate 14

Deck

STEP RIO RAILWAY CARSUNSHIELDED NOISE LEVEL

Depending upon the type of noise cri- terion, or metric, for your proposed building, perform the calculations listed below.

Leq(1)

Compute the factor CI, which is a correction for the number of passbys during the one selected hour of critical building use. CI is determined by locating on the hori- zontal axis of Figure 5.3-10 the value of N1 for this type of train. Read up until intersecting the curve. The value of C1 can be read off the vertical axis directly

left of the intersection. Using this value

and the values of CL, CD, CT, and DAC

calculate Leq(1) from the following equation: Leq(l) =

CL + CD + CT + CI - DAC - 36. Leq{8)

Compute the factor C8, which is a correction for the number of passbys during the eight hours of building use. C8 is deter- mined of Figure 5.3-10 by locating on the

horizontal axis the value of N8 for this type of train. Read up until Intersecting

the curve. The value of C8 can be read

off the vertical axis directly left of the

Intersection. Using this value and the

values of CL, CD, CT and DAC, calculate

Leq(8) from the following equation:

Leq(8) =

CL + CD + CT + C8 - DAC - 45. Leq(24)

Compute the factor C24, which is a correction for the number of passbys during a typical twenty-four hour day. C24 is determined by locating on the horizontal

axis of Figure 5.3-10 the value of N24 for

this type of train. Read up until inter- secting the curve. The value of C24 can

be read off the vertical axis directly left of the Intersection. Using this factor and

the values of CL, CD, CT, and DAC. cal- culate Leq(24) from the following equation: Leq(24) =

CL -I- CD + CT + C24 - DAC - 49. Ldn

Compute the factor CDN, which is a correction for the number of "daytime" and

"nighttime" passbys. it Is determined

from the corrected number of passbys,

CN, defined as CN = ND + 6NN,

where ND Is the number of "daytime",

and NN is the number of "nighttime"

passbys for this type of train. CDN is determined by locating on the horizontal

axis of Figure 5.3-10 the value of CN.
Read up until intersecting the curve. Tfie value of CDN can be read off the vertical axis directly left of the intersection. Using

this value and the values of CL, CD, CT,

and DAC, calculate Ldn from the following

equation:

Ldn =

CL -f CD + CT -f CDN - DAC - 49.

C. Shielding Adjustments

The previous steps assumed that there was

no shielding between the railway and the

building site. If there is any shielding due

to a barrier, elevated railway, depressed

railway, rows of buildings or a belt of vegetation, it must be taken into account. This is done in STEPS R11 through R15.

The corrections for shielding due to barriers, elevated railways and depressed rail- ways are a function of the railway vehicle

type, because of the different locations of the major noise sources. For freight cars, conventional passenger coaches, and rapid

transit vehicles, the predominant noise source is the wheel-rail interaction located

close to the ground; while for diesel-eiectric

locomotives, the major source of noise is the exhaust outlet located approximately

fifteen feet above the rails. Thus, there are two shielding corrections; one for railway

cars, CSC, and one for diesel-eiectric loco- motives, CSL. These corrections are deter- mined by calculating the path length differ- ences for railway cars and for diesel-eiectric

locomotives using STEP R11 for the type of shielding present. For these calculations,

this design guide assumes that the fre- quency spectrum for railway car (wheel-rail)

noise is similar to highway traffic noise, and

employs 500 Hz as the frequency. However,

a frequency of 125 Hz is used for dieseleiectric locomotive noise. To account for these frequencies being different, a factor

of (125 ~ 500) is used in calculating

path length difference, U. Using these

values of L, CSC and CSL are determined

for an "infinitely" long barrier in STEP R12.

If the barrier is "finite" in length, the necessary adjustments are made in STEP R13.

The shielding corrections for rows of build- ings which act as barriers and for vegetation are related to the physical layout of the

railway and the location of your proposed

building. The correction for shielding due

to rows of buildings which act as barriers,

CSB, is computed in STEP R13. The correction for shielding due to vegetation, CSV, is computed in STEP R14. Note that the atten- uation due to rows of buildings which act as barriers, and to vegetation is added to

the attenuation due to barriers and elevated

or depressed railways. For example, if the

A-weighted sound level attenuations of a

barrier, two rows of buildings and a 100

feet of dense woods are 5, 6, and 5 dB,

respectively, the total A-weighted sound

level attenuation is 16 dB.

After these shielding corrections are deter- mined, the individual noise contributions are

calculated and combined to get the total railway noise in STEP R16.

If there are no barriers, the noise levels cal- culated in the previous steps are the values

to be used to predict noise levels in your

building and on its site. Omit STEPS R11

through R15 and proceed to STEP R16 to get

the total noise due to railways.

STEP R11 PATH LENGTH DIFFERENCE

Compute the path length difference for railway cars, LC, and for diesel-eiectric

locomotives, LI, for the type of barrier

present. Be sure the obstruction blocks

the line-of-sight between the source and

receiver, being careful about diesel-eiectric locomotives which have the noise source located fifteen feet above the rail- way. If the line-of-sight is not blocked,

there will be no attenuation.

1. Barrier: Ac = VHB' + (D - DB)^

A/ = V(HB - 15)^ + (D - DB)^

Be = B/ = V(HB + hB)^ + DB^

Cc = VhB' + D^ C/ = vOtbTWTd^

2. Elevated Railway:

Ac = [D - DE]

A/ = V225 + (D - DE)^

Be = B/ = VHE^ + DE^

Cc = ViHEM^

CI = V(HE ^ "lO)^ + D^

3. Depressed Ftailway:

Ac = \/HD^ + (D - DD)^

A/ = V(HD - 15)^ + (D - DD)^

Be = B/ = VhD' + DD'

Cc = V(HD + hD)^ + D^ CI = V(HD + hD - 15)^ + D^

From these values the path length differ- ences are calculated from the following

equations:

Le = Ac -I- Be - Cc

LI = .25 [A/ + B/ - CI]. Record these values on Railway Worksheet 2 and proceed to the next step.
STEP R12 SHIELDING CORRECTION—

"INFINITE" BARRIER

Compute the shielding corrections CSC

and CSL. These values are determined

from the path length differences calculated in the previous step [9]. If the path

length difference is negative or less than

0.01 ft, there is no appreciable shielding

and the correction is zero; if the path

length difference is positive and greater

than 0.01 ft, the shielding correction is determined by locating on the horizontal

axis of Figure 5.3-13 the value of the path

length difference. Read up until intersecting the curve. The value of the shielding

correction can be read off the vertical axis directly left of the intersection. This

procedure is followed using Lc to deter- mine CSC, and LI to determine CSL.

Record these values on Railway Worksheet 2. If the included angle, a, is less than 170, the barrier is of "finite" length,

and you must proceed to STEP R13. But if the included angle, a, is greater than 170, no adjustment to the shielding corrections

is needed. Omit STEP R13 and continue

the design guide analysis.

Figure 5.3-13. A-weighted Shielding Correction Versus Path Length Difference for Barriers.

Table 5.3-2. Shielding Corrections for a Finite Barrier.

Infinite Barrier Shielding Correction CSC or CSL 0 .1 .2 .3 RA =

.4

a/180°

.5 .6 .7 .8 .9 1.0

1 0 0 0 0 0 0 1 1 1 1 1 2 0 0 0 1 1 1 1 2 2 2

3 0 0 0 1 1 2 2 2 3 3

4 0 0 1 2 2 2 3 3 4

5 0 0 1 2 2 3 3 4 5 6 0 0 2 2 3 3 4 5 6

7 0 0 2 2 3 4 4 6 7 8 0 0 2 2 3 4 5 6 8

9 0 0 2 3 3 4 5 7 9

10 0 0 2 3 3 4 6 7 10

11 0 0 2 3 3 4 6 8 11 12 0 0 2 3 4 5 6 8 12
STEP R13 SHIELDING CORRECTION—

"FINITE" BARRIER

Compute the adjusted values of CSC and

CSL to account for shielding elements of

finite length. These adjusted corrections are determined from the factor RA, which

is calculated from the included angle, a

(in degrees), by using the following equation: a°

Now go to Table 5.3-2 and enter the first column at the value of CSC and read across that row to the column corresponding to the value of RA. This is the adjusted value of CSC. Repeat this procedure using the value of CSL to get the

finite shielding correction for dieselelectric locomotives. Record these adjusted shielding corrections on Railway

Worksheet 2, and continue the design

guide analysis.

STEP R14 SHIELDING CORRECTIONBUILDINGS ACTING AS

BARRIERS

Calculate the correction, CSB, for rows

of buildings which shield the railway

from your building. This correction depends on the number of rows of inter- vening buildings, nr, and is determined

from Table 5.3-3. Record this correction on Railway Worksheet 2, and continue the

design guide analysis.

Table 5.3-3. Shielding Corrections for Buildings Acting as Barriers [8].

Number of RowsShielding

Correction, CSB

1 4.5 2 6.0 3 7.5 4 9.0 5 or more 10.0

STEP R15 SHIELDING CORRECTIONVEGETATION

Calculate the correction, CSV, for a belt of vegetation of depth, dw, which shields

the railway from your building. This correction is simply an A-weighted sound

level attenuation of 5 dB for the first 100

feet of woods and 10 dB for woods over 200 feet in depth. Interpolation between

these values is left to the discretion of the user of this design guide. Record

this correction on Railway Worksheet 2 and continue the design guide analysis.

STEP R16 TOTAL RAILWAY NOISE

Compute the total noise at the building

site due to the railway. First sum the

shielding corrections on Railway Worksheet 2. Subtract these total shielding cor- rections from the unshielded noise levels

to get the individual components of the

total railroad noise at the building site. Since these levels are logarithmic, they

cannot be simply added together or aver- aged to get the total noise level. Instead,

they must be combined, two values at a

time, with the use of Table 5.3-4. Start with the two smallest levels, and subtract one from the other to get the difference.

Table 5.3-4. Level Adjustment for Summing Noise Levels.

Level Adjustment

Difference of (To be Added to Two Noise the Larger of Levels, dB the Two Values)

10 or more 0

4-9 1 2-3 2

0-1 3

With this value go to Table 5.3-4 and

determine the level adjustment which is to be added to the larger of the two original noise levels. Now repeat this procedure with this adjusted level and another

of the railway noise components. Continue this computation until all components have been combined into one value. For example, if the A-weighted levels of the diesel-electric locomotives and rail- way cars for freight trains are 50 and

52 dB respectively, and the A-weighted

sound levels of the diesel-electric loco- motives and passenger coaches for conventional passenger trains are 51 and 50

dB respectively, the total noise is,
77 50—,

50—

51-

diff. - 0 add 3

53

diff. - 2

add 2 55

diff. add 2 57 dB

52-

Record this total noise leve! on Railway

Worksheet 1.

* « * * * This completes the prediction of railway

noise. These procedures should be re- peated for each railway that is listed on the Preliminary Source Evaluation Worksheet

with a yes answer in Column 2, and for each

point on the site or building room that you

analyze. The total noise at any point on the building site due to all railways is the summation of the noise contributions from each

railway. This summation is accomplished by

the same method as used in STEP R16.

Refer to this step for the procedure of summing noise levels. Record the total noise

level cn Railway Worksheet 1.

Now proceed to Section 5.4 and predict

the noise level due to aircraft. If aircraft do

not affect your building site proceed directly

to Chapter 6.

References

Chapter 5

Section 3

Railway

Passby Noise

[1] Swing, J. W., and Pies, D. B., Assess- ment of noise environments around rail- road operations, Wyle Laboratories Report WCR73-5 (Wyle Laboratories, El Segundo, California, July 1973).

[2] Bender, E. K., Ely, R. A., Remington,

P. J., and Rudd, M. J., Railroad environmental noise: A state of the art assess- ment, BBN Report No. 2709 (Bolt Ber- anek and Newman Inc., Cambridge,

Massachusetts, January 1974).

[3] Anon., A study of the magnitude of trans- portation noise generation and potential

abatement: Volume V — train system

noise, U.S. Department of Transportation Report OST-ONA-71-1 (Serendipity,

Inc., Arlington, Virginia, November

1970). Available from the National

Technical Information Service, Springfield, Virginia, Accession No. PB-203-

186.

[4] Manning, J. E., Cann, R. G., and Fredberg, J. J., Prediction and control of

rail transit noise and vibration—a state- of-the-art assessment, CC Report No.

74-1 (Cambridge Collaborative, Inc., Cambridge, Massachusetts, March

1974).

[5] Peters, S., Predictions of rail-wheel

noise from high speed trains, Acustica,

28 (6), 318-321 (June 1973).

[6] Anon., Transportation noise and noise

from equipment powered by internal combustion engines, U.S. Environmental

Protection Agency Report No. NTID

300.03 (Wyle Laboratories, El Segundo,

California, December 1971). Available

from the U.S. Environmental Protection

Agency, Washington, D.C. 20460.

[7] Anon., Background document for rail- road noise emission standards. EPA Report No. EPA-550/9-76-005 (U.S. Environmental Protection Agency, Washington, D.C, December 1975).

[8] Swing, J. W., Simplified procedure for developing railroad noise exposure contours, S/V Sound and Vibration, 9 (2), 22-23 (February 1975).

[9] Kugler, B. A., and Piersol, A. G., Highway noise: a field evaluation of traffic noise reduction measures, NCHRP Report 144 (Bolt Beranek and Newman

Inc., Canoga Park, California, 1973).

Available from the Highway Research

Board, 2101 Constitution Ave., Washington, D.C. 20418.

[10] Path, J. M., Blomquist, D. S., Heinen,

J. M., and Tarica, M., Measurements of railroad noise—line operations, yard

boundaries and retarders. EPA Report

No. 550/9-74-007 (National Bureau of Standards, Washington, D.C, December 1974).
Chapter 5

Section 4

How to Estimate

Aircraft Noise

The noise at the building or site due to air- craft flyovers depends upon such variables

as: the distance between the building site and the aircraft; type and size of the air- craft and its operating characteristics (primarily its thrust level); and, atmospheric

conditions. Unlike automobiles, trucks, and

trains, aircraft are not confined to a specific route—even at airports there m\\ be a number of runways, hence a number of possible

paths for takeoffs and landings. Also, depending on the type of aircraft, loading

weights, the volume of air traffic, and

weather conditions, approach and takeoff

profiles can vary widely. To handle these

variables, the models of aircraft noise, like those for highways, usually depend upon

computers for numerical results. Whereas

computers can manage these complexities,

they are obviously beyond the scope of this design guide.

Instead, the design guide analysis* relies either upon—(a) existing measures of the noise near the airport such as NEF or CNR

ratings, which are the most common measures of aircraft noise in the United States, or—(b) a few simple estimates of the noise

level based on the airport type and level of activity.

The CNR, or Composite Noise Rating, was

one of the first methods developed to as- sess the effect of aircraft operations on air- port communities. The CNR is obtained by

making corrections to the noise levels of the

various aircraft expressed in terms of the "perceived noise level" (PNL), which is a measure of the relative acceptability of air- craft sounds. The PNL is a quantity, calculated from measured noise levels (it cannot

be read directly from a meter), that correlates well with subjective responses to vari- ous kinds of aircraft noise [1]. The corrections to the PNL account for the number of

aircraft flights, the time of day, and seasons

of the year. These corrections are needed

since human tolerance of aircraft noise depends not only upon the noise level for each

noise event, but also the number of events. Thus, an aircraft noise problem may result from a small number of very loud aircraft or from a much larger number of quieter air- craft [2]. Since CNR accounts for numerous

noise events over an extended time period, it is essentially an integrated descriptor of

total noise exposure. Unlike Leq or Lmax,

which can be measured, CNR is always cal- culated from other acoustic descriptors.

Sites with a CNR value of 100 or less will normally be acceptable for your proposed

buildings [3].

* The design guide analysis of aircraft noise is based on work performed by Bolt Beranek and Newman, Inc. for tfie U.S. Department of Housing and Urban Development [10].

The NEF, or Noise Exposure Forecast, sys- tem of rating aircraft noise is rapidly superceding the CNR method. The NEF single

number rating is similar to the CNR except

that the perceived noise level is replaced

by the effective perceived noise level, which

is equal to the perceived noise level plus

corrections for the duration of the noise event and for the presence of pure tone components which are not included in the CNR. This latter correction has been

included because it has been found that discrete frequency components, such as jet

engine whine, are the principal cause of annoyance to persons living near airports

[2]. The NEF numerical values differ considerably from the corresponding CNR

values; e.g., an NEF of 30 corresponds ap- proximately to a CNR of 100. This difference was introduced intentionally so that the two

ratings would not be confused. Like CNR,

NEF is an integrated descriptor of total noise

exposure, and is calculated from other

quantities rather than being directly measured. Sites with a NEF value of 30 or less

will normally be acceptable for your pro- posed building [3].

The total noise exposure due to aircraft operations has been determined for many

communities on the basis of the CNR

or NEF indices, and the results mapped

as contours of equal CNR or NEF val- ues. For an example of such a contour map, see Figure 5.4-1 [4]. If these contour maps exist for the airport near the site for your proposed building, the maps can be

used to estimate noise due to aircraft fly- overs. These procedures are given in STEPS A2 and A4. NEF contours for many

airports are available in reports cited in this design guide [5-10].

If these contour maps do not exist, the air- craft noise at your building site can be

estimated by an alternative technique. First, the airport is classified into one of four general categories based on the "effective"

number of jet operatons, NJeff, which is defined as NJday—the number of "daytime"

(7 A.M. to 10 P.M.) jet operations, plus seventeen times NJnight—the number of "nighttime" (10 P.M. to 7 A.M.) jet operations [3]. The airport categories are then defined as: Category 1 : 0 to 50 "effective" jet operations;

Category 2: 51 to 500 "effective" jet operations; Category 3: 501 to 1300 "effective" jet

operations; and Category 4: over 1300 "ef- fective" jet operations. If there are no jet

operations, the airport is placed in Category

1. (Placing all airports without jet operations

in Category 1 may be too severe, particularly

for very small aiports which have only a Mm-
Figure 5.4-1. Rating Contours Superimposed on a iVlap of tlie Local Area [4].
Table 5.4-1. Effective Number of Jet Aircraft Operations for Various U.S. Airports [3].

Airport Number Of Jet Aircraft Operations Category City and State NJday NJnight NJaft. Wisconsin Rapids, Wis. 1 0 1 Ithaca, N.Y. 0

1 Concord, Calif. 6 0 6 Columbia, Mo, 3 Vi 11

Atlanta, Ga. (Fulton) 13 0 13 Van Nuys, Calif. 22 0 22

Huntsville, Ala. 98 0 08

Erie, Pa. 40 4 108 Colorado Springs, Colo. 80 5 166 2 Little Rock, Ark. 108 7 227

Melbourne, Fla. 87 20 427

Raleigfi/Durham, N.C. 130 19 453

Tulsa, Okla. 199 16 471

Nastiville, Tenn, 164 27 623

Hartford, Conn. 115 32 659 3 El Paso, Tex. 130 36 742

Milwaukee, Wis. 210 38 856 San Diego, Calif. 267 46 1049

Portland, Ore. 360 64 1448

Wastiinglon, D.C. (National) 614 64 1702 Washington, D.C. (Dulles) 332 82 1726 Kansas City, Mo. 302 86 1764 4 Seattle/Tacoma, Wash. 280 88 1776 Tampa, Fla. 366 120 2406

Detroit, Mich. 544 114 2482

Dallas/Ft. Worth, Tex. 704 131 2931

Boston, Mass. 680 136 2992 New York, N.Y. (Kennedy) 1020 171 3927

Los Angeles, Calif. 1089 185 4234

Chicago, III. 1636 315 6991

Table 5.4-2. Approximate Distances to NEF 40 and NEF 30 Contours [3].

Effective Distances to NEF 40 Contour Distances to NEF 30 Contour

Airport Number of From Side of From End of From Side of From End of Category Jet Operations Runway Runway Runway Runway

NJeff. DS-40 DE-40 DS-30 DE-30

1 0-50 0 0 1000 Feet 1 Mile 2 51-500 1000 Feet 1 Mile 0.5 Mile 3 Miles

3 501-1300 2000 Feet 2.5 Miles 1.5 Miles 6 Miles

4 More Than 3000 Feet 4 Miles 2 Miles 10 Miles 1300

ited number of operations. You can visit the for typical U.S. airports [3]. With this

site and judge for yourself the magnitude of approximate contour map you can estimate

the aircraft noise, then decide if the airport the noise level at your site due to aircraft should be considered.) Examples of U.S. flyovers. These procedures are given in airports v\/hich fall into these four categories STEPS A3 and A4.

are given in Table 5.4-1 [3]. Before proceeding, study briefly the flow

After the airport has been classified into diagram of Figure 5.4-3 which outlines the one of the four categories, approximate steps necessary to estimate aircraft noise. NEF 40 and NEF 30 contours can be con- First obtain the required airport input data

structed on a local map showing your build- (STEP A1), which are then used to calculate

ing site (Figure 5.4-2) using the distances the CNR or NEF value at your proposed

of Table 5.4-2, which are average values building location (either STEP A2 or STEP
Figure 5.4-2. Layout of Approximate NEF Contours. Dimensions

XI and X2 should be measured on a line perpendicular to the runway for building sites located at the side

of the runway; and on a line parallel to the runway lor building sites located beyond the end of the runway.

A3). Finally, calculate the noise level due

to aircraft operations from this airport (STEP

A4). An example of the step-by-step calculations is given in Section 5.5.

Before you can estimate the noise levels,

you will need to obtain certain information

about the airport near your building site. The information, described in STEP A1,

should be recorded in Aircraft Worksheet 1, shown in Figure 5.4-4.

Aircraft Noise Prediction IVIethod STEP A1 AIRPORT DATA

The information that is required on air- ports may be obtained from the Federal

Aviation Administration (FAA) Area Office

for commercial airports; or, when the in- formation can be released, from the mili- tary agency in charge for military airports.

The data should be gathered for each air- port (if more than one) that is listed on

the Preliminary Source Evaluation Worksheet with a yes answer in Column 2.

1. First you should determine if either

CNR or NEF contours have been

mapped for the airport. If contour maps are available complete substeps

2 and 4; but, if not, complete substeps

3 and 4.

2. CNR or NEF Contour Maps Available.

Lay out your building site on the contour map and examine its position

relative to the CNR or NEF contours.

If located on or very near one of the contours, the only information to be

entered in Aircraft Worksheet 1 is the CNR or NEF value for that contour. If the building site falls between two contours, enter the CNR or NEF values for both, and the distances from each contour to the building as shown in Figure

5.4-5.

If your site is located inside the NEF

40 (CNR 100) contour, you will probably have a serious noise problem. You

should obtain the services of a consultant to consider in detail the continued advisability of construction on

or rejection of the site, or the special

adaptations which may be required.

If your site is located outside the last contour that is mapped, your use of the predictive schemes of this design

guide will be limited. It is a rule of thumb that if the building site is far- ther outside the NEF 30 (CNR 100) contour than the distance between the

NEF 30 and 40 (CNR 100 and 110)

contours, there probably will be no problem with aircraft noise [3]. Aside

from this your only alternative is to employ an acoustical consultant.
82

Aircraft Noise Prediction

CNR or NEF Contours

Available

• CNR or NEF Values

• Building Location

Relative to Contours

XI. X2 STEP A1.2

CNR or NEF Contours

Not Available

• Number of Jet Operations: NJday,

• Runw/ay Locations STEP A1.3

NJnight

Number of Operations

• One Hour: N(1)

• Eigtit Hour: N(8)

• "Daytime" (7 AfVI to 10 PM): NJday

• "Nigtitime" (10 PM to 7 AM):

NJnigtit STEP A1.4

CNR or NEF Value at Building Site

• Building On or Near

A Contour: Use Ttiat Value

• Building Between

Contours: Interpolate STEP A2 I

NEF Value at Building

Site

t Classify Airport Construct Approximate

• NEF Contours

• Building On or Near A Contour: Use Tfiat Value

• Building Between

Contours: Interpolate STEP A3 J

Aircraft Noise Level

• Leq(1)

• Leq(8) STEP A4

Leq(24) Ldn

Higtiway Noise

Section 5,2

Total IBuilding

Site Noise Level

Ctiapter 6

Railway Noise

Section 5.3

Figure 5.4-3. Aircraft Noise Prediction Flow/ Diagram.
Aircraft Worksheet 1

RiiiiHinn Prniort Site Doint Or bulldino room (or which sound pressure

lauQlQ nro hoing onllmntBri

1 nr^atinn DfiRignBr

Ownfir natn Rnv/inBri

Contour Maps Available V/////////////A

1

If Building is on or very near Contour #1 or .#-2, Record that value on Line 11,

If not, obtain the data of Lines 2 and 3

2 Contour Values CNR or NEF #1 CNR or NEF #2

3

Building Location Between Contours #1 and #2

XI X2 R C5 CIO

4 CNR or NEF Value At The Building Site Also Record on

Line 11

Contour Maps Not Available

5 Number of Jet Operations

NJday NJnight NJetf

6

Airport Category (Check One)

1 2 3 4

7

If building is on or very near the NEF 30 or NEF 40 Contour, record that value on Line 11.

If not, obtain the data on Line 8.

8

Building Location Between NEF 30 and NEF 40 Contours

XI X2 R 010

9 NEF Value At The Building Site Also Record on

Line 11

10 Number of Operations NJday NJnight N(8) N(1)

11 CNR or NEF Value

At The Building Site

12 NEF

ConvertValueCNR to siiiiei 13 Aircraft Noise Level At The Building Site

Leq(1)

R1 01 Leq(1)

i

Leq(8) R8 C8 Leq(8)

//

Leq(24) R24 C24 Leq(24)

Ldn

Ldn

Figure 5.4-4. Aircraft Worksheet 1.
CNR or NEF

Contour #1

CNR or NEF

Contour #2

Building

Site

Figure 5.4-5. Geometry for Estimating CNR or NEF rating at \he Building Site.

Dimensions x1 and x2 should be measured on a line perpendicular to the runway for building sites located to the side of the runway and on a line parallel to the runway for building sites located beyond

the end of the runway.

3. CNR or NEF Contour IVIaps Not Available. You should determine the average number of "daytime" (7 A.M. to 10 P.M.)

jet operations, NJday; and the average

number of "nighttime" (10 P.M. to 7

A.M.) jet operations, NJnight. If there are no jet operations note this on

Aircraft Worksheet 1. You must also

determine the location and direction of major runways of the airport, and show

these on a map of the local area which

includes your building site.

4. Number of Operations.

Depending upon the metric being used

to estimate noise for your building and

site, information on the number of

flight operations may also be required.

Obtain only those data necessary to make calculations for the metric you

have selected. The data should be for average airport operations.

• Leq(1)—NJday, NJnight, and N(1),

which is the total number of operations in the one selected hour of

critical building use.

• Leq(8)—NJday, NJnight and N(8),

which is the total number of operations in the eight-hour period of building use.

• Leq(24)—NJday, NJnight

• Ldn—no further data needed

* * * * * The procedures for predicting noise levels

at the building site due to aircraft are

given in the following steps. If CNR or NEF

contour maps are available, use STEP A2;

if not, use STEP A3. The results for either

step is an approximate CNR or NEF value

at the building site, which can then be

used to estimate noise levels for the metric

you have chosen: Leq(1), Leq(8), Leq(24)

or Ldn. The relationships between these

various metrics and the CNR or NEF values

are given in STEP A4 [11, 12].

STEP A2 CNR OR NEF VALUE AT THE

BUILDING SITE—CONTOUR

MAPS AVAILABLE

If the building is located on or very near a

contour, you can use its value and pro- ceed directly to STEP A4. But if the building falls between two contours, you must

calculate an approximate CNR or NEF

value for that location. First, determine

the distance ratio, R, as defined in Figure

5.4-5. With this value go either to Table

5.4-3 and determine the factor C5 (if contours are mapped in increments of 5), or

to Table 5.4-4 and determine the factor
85 C10 (if contours are mapped in incre- ments of 10). The rating at tlie building

site is then estimated by one of the following equations. For contours in increments

of 5, CNR (or NEF) - CNR (or NEF) value of contour #1 — C5. For contours in increments of 10,

CNR (or NEF) = CNR (or NEF) value of contour #1 — CIO. Record this value on Aircraft Worksheet 1.

STEP A3 NEF RATING AT BUILDING

SITE—CONTOUR MAPS NOT

AVAILABLE

Using the data obtained in STEP A1.3,

classify the airport near your site in one

of the four categories defined in Table

5.4-2. The airport classification is based

on the "effective" number of jet operations, which is defined as the number of "daytime" jet operations plus seventeen

times the number of "nighttime" jet operations. NJeff = NJday + 17 NJnight

With this value determine the airport cate- gory from Table 5.4-2. If there are no jet

operations, the airport is placed in Cate- gory 1. Now with the airport classified in one of the four categories, you can construct approximate NEF contours. On a map of the area which shows the principal run- ways, mark the location of the building

and site, and determine which runway is most likely to affect the site. Then using

the distances of Table 5.4-2 construct approximate NEF 40 and NEF 30 contours as shown in Figure 5.4-2. Note that

for airports in Category 1, NEF 40 corre- sponds to the runway itself. If the build- ing site is located on or very near one

of these contours, use that value and

proceed directly to STEP A4. If your building or site is located inside the NEF 40

contour or outside the NEF 30 contour,

follow the instructions of STEP A2.2

(above). But if the building or site falls between

two contours, you must calculate an approximate NEF value for that location.

First, calculate the distance ratio, R, as

defined in Figure 5.4-2. Then determine

the factor CIO from Table 5.4-4. The

rating at the building site is given by

NEF = 40 -CIO.

STEP A4 AIRCRAFT NOISE LEVEL

With the CNR or NEF value at the build- ing site determined in either STEP A2 or STEP A3, you can now calculate aircraft

noise in terms of the metric you have selected. First, convert any CNR value to a corresponding NEF value. This conversion

is made by the equation [1 1 ] NEF CNR 70.

Table 5.4-3. Factor, C5, for Interpolating

Between CNR or NEF Contours in Incre- ments of 5.

Distance Ratio

x2

Factor C5 to be

subtracted from larger ~

^.j CNR or NEF value.

>12.3 0

3.21 — 12.3 1

1.41 —3.2 2

0.61 —1.4 3

0.21 —0.6 4

<0.2 5

Table 5.4-4. Factor C10 for Interpolating

Between CNR or NEF Contours in Incre- ments of 10.

Distance Ratio

x2

R =

x1

Factor CIO to be

subtracted from larger

CNR or NEF value

>35.0

10.41-35.0

5.51-10.4

3.31-5.5

2.21-3.3

1.51-2.2

0.91-1.5

0.61-0.9

0.31-0.6

0.11-0.3

<0.1

0

1

2

3

4

5

6

7

8

9

10
Figure 5.4-6. Correction For Number of Operations.

Now perform the appropriate calculation

given in the list below for the metric you

selected.

• Leq(l) [12]

Compute the factor C1, which is a correction for the number of operations based

on the one selected hour of critical build- ing use. It is determined from the number

of operations ratio, R1, defined as, NJday + 17 NJnight

R1 = . N(1)

To determine CI, locate along the hori- zontal axis of Figure 5.4-6 the point

corresponding to the value of R1. Read

up until intersecting the curve. The value

of C1 can be read off the vertical axis

directly left of the intersection. Using this value and the NEF value at your site, calculate Leq(1) from the following equation: Leq(1) = NEF + 41 - CI.

• Leq(8) [12]

Compute the factor C8, which is a correction for the number of operations based

on the eight hours of building use. It is determined from the number of operations ratio, R8, defined as, 8(NJday + 17 NJnight)

R8 = . N(8)

To determine C8 locate along the hori- zontal axis of Figure 5.4-6 the point cor- responding to the value of R8. Read up

until intersecting the curve. The value of C8 can be read off the vertical axis

directly left of the intersection. Using this value and the NEF value at your site,

calculate Leq(8) from the following equation: Leq(8) = NEF + 41 - C8.

• Leq(24) [12] Compute the factor C24, which is a correction for the number of operations

based on a twenty-four hour average.

It is determined from the number of operations ratio, R24, defined as, 24 (NJday + 17 NJnight)

R24 = . (NJday + NJnight)

To determine C24, locate along the hori- zontal axis of Figure 5.4-6 the point cor- responding to the value of R24. Read up

until intersecting the curve. The value of C24 can be read off the vertical axis di- rectly left of the intersection. Using this value and the NEF value at your site, calculate Leq(24) from the following equation: Leq(24) = NEF +41 - C24.

• Ldn [11] Using the NEF value at your site, calculate Ldn from the following equation:

Ldn = NEF + 25.

This completes the prediction of aircraft noise. These procedures should be repeated

for each airport (if more than one) that is listed on the Preliminary Source Evaluation

Worksheet with a yes answer in Column 2.

This also completes the prediction of trans- portation system noise. Now proceed to Chapter 6 and compute the total sound level

in the outdoor activity area or room of your

proposed building.
References

Chapter 5 Section 4

Aircraft Noise

[1] Anon., A study—insulating houses from

aircraft noise, U.S. Department of Housing and Urban Development Report No. HUD TS-19 (Bolt Beranek and

Newman Inc., Los Angeles, California,

November 1966). Available from the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402, Stock No. 0-266-293.

[2] Anon., A study of the magnitude of transportation noise generation and

potential abatement: volume III —air- port/aircraft system noise, U.S. De- partment of Transportation Report No. OST-ONA-71-1 (Serendipity, Inc., Arlington, Virginia, November 1970).

Available from the National Technical

Information Service, Springfield, Virginia, Accession No. PB-203-184.

[3] Schultz, T. J., Noise assessment guidelines technical background, U.S. De- partment of Housing and Urban Development Report No. HUD TE/NA 172

(Bolt Beranek and Newman Inc., Cambridge, Massachusetts, 1971). Available

from the Superintendent of Documents,

U.S. Government Printing Office,

Washington, D.C. 20402, Stock No.

2300-0190.

[4] Jensen, P., and Sweitzer, G., How you

can soundproof your home (Lexington

Publishing Co., Lexington, Mass., 1974).

[5] Bishop, D. E., and Horonjeff, R. D., 1965, 1970 and 1975 noise exposure

forecast areas for John F. Kennedy

Airport, New York, U.S. Department of Transportation Report No. FAA DS-67-

11 (Bolt Beranek and Newman Inc., Van Nuys, California, August 1967).

[6] Bishop, D. E., and Horonjeff, R. D., 1965, 1970 and 1975 noise exposure

forecast areas for Chicago O'Hare In- ternational Airport, U.S. Department of Transportation Report No. FAA DS-67-

12 (Bolt Beranek and Newman Inc., Van Nuys, California, August 1967).

[7] Bishop, D. E., and Horonjeff, R. D., 1965, 1970 and 1975 noise exposure

forecast areas for Los Angeles Inter- national Airport, U.S. Department of

Transportation Report No. FAA DS-67-

13 (Bolt Beranek and Newman Inc., Van Nuys, California, August 1967).

[8] Franken, P. A., and Standley, D., Air- craft noise and airport neighbors: a study of Logan International Airport, U.S. Department of Transportation and

Department of Housing and Urban De- velopment Report No. DOT/HUD

IANAP-70-1 (Bolt Beranek and Newman

Inc., Cambridge, Mass., March 1970).

[9] Anon., Noise exposure forecast contours for expected 1985 and 1990 operations at seven U.S. airports, BBN

Report No. 2076 (Bolt Beranek and

Newman Inc., Cambridge, Mass., January 1971). Available from the National

Technical information Service, Springfield, Virginia, Accession No. AD-722-

365.

[10] Anon., Metropolitan aircraft noise

abatement policy study. Bradley Inter- national Airport, Windsor Locks, Connecticut, U.S. Department of Transportation and Department of Housing and

Urban Development Report No. HUD/

DOT 72-1 (Capital Region Planning

Agency, Hartford, Conn., May 1972).

Available from the National Technical

Information Service, Springfield, Vir- ginia, Accession No. PB-219-100.

[11] Anon., Information on levels of environmental noise requisite to protect public health and welfare with an adequate

margin of safety, U.S. Environmental

Protection Agency Report No. 550/9-

74-004 (Environmental Protection

Agency, Office of Noise Abatement

and Control, Arlington, Virginia, March

1974). Available from the Superintendent of Documents, U.S. Government

Printing Office, Washington, D.C. 20402,

Stock No. 546-318/366.

[12] Copley, L. G., Translation between Dif- ferent Community Noise Exposure

Measures, Report to U.S. Department

of Transportation, Transportation System Center, Cambridge, Mass. under

Order No. TS-5150, April 1973.

Chapter 5

Section 5

Illustrative Example of How

to Estimate

Building Site Noise

Consider the hypothetical example shown

in Figure 5.5-1. The building being considered is 70 feet wide by 150 feet long, and is 10 stories or approximately 100 feet high.

As an apartment, it is classified as a resi- dential occupancy. Thus, based on the dis- cussion of Chapter 3, the appropriate metric

for evaluating the building is Ldn. The total outdoor noise at this building site is a combination of sounds from two highways, a

railway and an airport. The prediction of the noise generated by each of these sources is outlined below.

Highway Noise Prediction

As seen from the map of the area, Figure

5.5-2, there are two highways which affect the building site. Highway -1 consists of two lanes in each direction, separated by a

Figure 5.5-2. Local Map Showing Details of Highways.
Highway Worksheet 1

Juilding Proiect Highway Number

Owner Designer ^

Site poini or building room

levels are being estimated

Dnie

for wtiirji sound pressure

Revised

Roadway —Building Site Distance DC (Feet) 700'

Medium Trucks Heavy Trucks

Average Vehicle Speed, mpti 50 50 SH 50

Total Number of Vehicles

3) Leq(l)

b) Leq(8)

c) Leq(24)

d) Ldn

Leq(1 ) No Shield ing

Total Shielding Correction (Highway Worksheet 2)

Leq(1) Corrected tor Shielding

Leq(8) No Shielding

Total Shielding Correction (Highway Worksheet 2)

Leq(8) Corrected tor Shielding

Leq{24) No Shielding

Total Shielding Correction (Highway Worksheet 2)

Leq(24) Corrected for Shielding

HNL 55 5Z bl

RON 0.51 0.5/ 0.51

CON

Ldn No Shielding 5^ 5b lo5

Total Shielding Correction (Highway Worksheet 2) 0

Ldn Corrected for Shielding 53 50

Total Highway Noise 65dd

Building Site Noise Due To Several Highways

Figure 5.5-3. Highway Worl<sheet 1 For Higliway #1 of Example.
Highway Worksheet 1

uilding Proiecl /g> ' Stof-Qj Af> 3rT/^ T

Designer C- 'S^g^ ^

Hiqhwny Nurnbor

Location

Owner Reg H

/^t^^r ^'^fi \/%/ 9CA S / ^1 2 °^ buikJing room (or v/hir.h -.ourKl ijii::-,nri: .

: ««^ «2 levels are being estimated 'T'op f-laaf /v Irsy

Revised

Roadway—Building Site Distance: DC (Feet)

Autos Mertium Trucks Heavy Trucks

Average Vehicle Speed, mpti ¥0

Total Number ol Vetiicles ^^^^^^^^^^^^^^

a) Leq(1)

Leq(1) No Stiielding

Total Shielding Correction (Highway Worksheet 2)

Leq(1) Corrected tor Shielding

Leq(8) No Shielding

b) Leq(8)

Total Shielding Correction (Highway Worksheet 2)

Leq(8) Corrected tor Shielding

Leq(24) No Shielding

c) Leq(24)

Total Shielding Correction (Highway Worksheet 2)

Leq(24) Corrected for Shielding

HNL SI

RDN 0.2^ O.ZS

CDN

d) Ldn

Ldn No Shielding 53 5?

Total Shielding Correction (Highway Worksheet 2)

Ldn Corrected lor Shielding

Building Site Noise Due To Several Highways

Figure 5.5-4. Highway Worksheet 1 for Highway #2 of Example
92

Figure 5.5-5. Cross-section Showing Higfiway #1 and Eartii Berm,

median. Tliis liighway is siiielded from tine building by an earth berm. Highway #2 is a

two-lane roadway that lies at grade with re- spect to the building site.

STEP H1.1 HIGHWAY TO BUILDING

OR SITE DISTANCE

First, the highway to building site dis- tances are determined from a map of the

local area (Figure 5.5-2). These values,

700 feet for Highway #1 and 400 feet for Highway #2, are recorded on separate

copies of Highway Worksheet 1, Figures

5.5-3 and 5.5-4, respectively.

STEP H1.2 BARRIER DATA

Only Highway #1 is shielded from the

building site. The necessary distances for evaluating an earth berm are determined

from a cross-sectional diagram of the

highway (Figure 5.5-5). These distances,

which are determined for the top floor (worst case as far as shielding is concerned), are: DC = 700 ft. HB = 19 ft. a = 180°

DB = 620ft. hB = -95 ft. These values are recorded on Highway

Worksheet 2 (Figure 5.5-6).

STEP H1.3 VEGETATION AND

BUILDINGS AS BARRIERS

There are no intervening rows of build- ings and no vegetation which would effectively shield the roadway from a room on

the top floor. Thus, for this case, these

types of shielding are neglected.

However, if a room on the ground floor were analyzed, shielding due to vegetation or intervening rows of buildings would

have to be taken into account. Also, the

shielding due to the earth berm is differ- ent for the ground floor. The distance hB

changes from -95 feet to about -5 feet

for a ground floor room. This changes the

•path length difference and hence the at- tenuation. This illustrates that the attenuation should be recalculated for rooms on

different floors.

STEP H2 TRAFFIC DATA

FOR HIGHWAY #1

For Highway #1 the average speed is 50

mph for all vehicle classifications. The

"daytime" and "nighttime" traffic volumes

are,DVA = 46,500 vehicles,

DVM =: 2550 vehicles,

DVH = 4350 vehicles

NVA = 23,710 vehicles,

NVM = 1300 vehicles,

NVH = 2220 vehicles.

From these values the average daytime

hourly vehicle volumes are calculated to be,

46,500

VA = —— = 3100 veh/hr;

1

2550

VM = —- = 170 veh/hr;

1

4350

VH = —— = 290 veh/hr.

15

These values are recorded on Highway

Worksheet 1 for Highway #1 (Figure

5.5-3).

STEP H2 TRAFFIC DATA

FOR HIGHWAY #2

For Highway #2, data are available only

in terms of automobiles and trucks. The

average speed for autos is 45 mph and

for heavy trucks is 40 mph. The "daytime"

and "nighttime" traffic volumes are, DVA = 10,650 vehicles,

NVA = 2660 vehicles,

DVH = 465 vehicles,

NVH = 120 vehicles.

From these values the hourly average daytime vehicle volumes are calculated to be,
Highway Worksheet 2

Building Project

Owne

Highway Number . ..

Site point or building room tor whuch sound pressure

levels are being estimated ^loo^ /VtV'

Sct^^ 5

/ Ju/ij 77 Revised

Designer

Roadway—Building Site Distance: DC (Feet) 700'

Stiielding Geometry

Barrier

Elevaled Roadway

Depressed

Roadv/ay

DB MB hB a DE HE a DD HD hD a

Path Length

Difference

Autos And Medium

Trucks

Aa/ m Ba/m Ca/m La/m

0. ^^5'

Heavy

Trucl<s \

Correction For

"Infinite" Shielding

Element

Auto Medium Truck Heavy Truck

CSA/M CSA/M CSH

G 0

Correction For

"Finite" Shielding Element

Included Angle Ratio, RA

Auto Medium Trucl< Heavy Truck

CSA/M CSA/M CSH

Building Barrier nr CSB

Vegetation dw CSV 'mm.

Total

Shielding

Correction

Auto Medium Trucl< Heavy Truck

CSA/M + CSS + CSV CSA/M + CSB + CSV CSH + CSB + CSV

(? 0

Figure 5.5-6 Highway Worksheet 2 for Highway #1 of Example,
10,650

VA =—-=710veh/hr;

1

465

VH = = 31 veh/hr

15

These values are recorded on Highway

Worksheet 1 for Highway #2 (Figure

5.5-4).

STEPS H3-H6 AUTOMOBILE NOISE

LEVEL FOR HIGHWAY #1

Predict the noise generated by each of the three vehicle classifications. Using the

values SA = 50 mph, VA = 3100 veh/hr

and DC = 700 ft, STEPS H3, H4 and H5

are performed to predict the noise level of automobiles (see the nomogram of Figure

5.5-7). The value of HNL is determined to be an A-weighted sound level of 55 dB.

Since the metric being used is Ldn, STEP

H6 is performed. First, the ratio RDN is calculated for automobiles,

NVA 23,710 vehicles

RDN = = = 0.51. DVA 46,500 vehicles

With this value, CDN is determined from

Figure 5.2-10 to be 4 dB, when rounded

to the nearest integer. The unshielded,

A-weighted day-night sound level for auto- mobiles on Highway No. 1 is then calculated to be:

Ldn = HNL + CDN = 55+4 = 59 dB.

Pivot

Point

20

Heavy

Trucks

30 40 50

+ i 60

SPEED: MPH

+ + +

20 30 40 50

Automobiles and

Medium Trucks

KEY:

Automobiles, HNL = 55clB — Medium Trucks, HNL = 52dB —- Heavy Trucks, HNL _ 61dB

70

60 70

+

B HNL

dB

XI

100

90

80

70

60

DC

FT

30 -

40 -

50 -

70 -

— 40

Predicted

Noise

Level

150 —

200 —

300

^OOH

700

1000-

1500 —

2000

Distance

To

Observer

V

VEH/HR

15000

Figure 5.5-7. Highway Noise Nomogram for Highway #1 of Example.
STEP H7 MEDIUM TRUCK NOISE

LEVEL FOR HIGHWAY #1

This general procedure is repeated for medium trucks using a corrected veliicle volume, VMC, calculated as: VMC = 10 VM = 10 X 170 = 1700 veh/hr,

and using the values SM = 50 mph and

DC = 700 ft. The predicted value of Ldn

is an A-weighted sound level of 56 dB.

STEP H8 HEAVY TRUCK NOISE

LEVEL FOR HIGHWAY #1

For heavy trucks the procedure is again

repeated (using the top scale of vehicle

speeds) with the values SH = 50 mph,

VH = 290 veh/hr and DC = 700 ft. The

predicted value of Ldn is an A-weighted

sound level of 65 dB.

STEP H9 PATH LENGTH DIFFERENCE

Next, the shielding adjustments are deter- mined for the earth berm of Highway #1.

The path length difference for autos and

medium trucks is, Aa/m = VHB' + (DC - DB)' =

V19' + (700 - 610)'^ = 82.23 ft, Ba/m = V(HB + hB)' + DB'

V(19 + (- 95))' + 620' = 624.64 ft, Ca/m = VhB' + DC' = V(- 95)' + 700' = 706.42 ft, La/m = Aa/m -|- Ba/m - Ca/m = 0.45 ft. STEP H10 SHIELDING CORRECTION—

"INFINITE" BARRIER

The A-weighted shielding correction,

CSA/M, is determined from Figure 5.2-11

to be approximately 6 dB. [Note that this value of attenuation is for the top floor, which for this example is the worst case.

If some other floor is of interest, the value

of CSA/M should be recalculated.] This

value is recorded on Highway Worksheet

2 (Figure 5.5-6). Since the included angle

is approximately 180°, the earth berm can be considered infinite and no further adjustment is needed.

As shown in Figure 5.5-5, the line-of-sight

between the top floor and the effective source height for heavy trucks is not broken. Thus, there is no shielding for the upper floors for the noise from heavy

trucks and the value of CSH for the top

floor is zero.

STEP H14 TOTAL NOISE LEVEL

FOR HIGHWAY #1

The total noise from Highway #1 is computed by logarithmic combination of the

levels of the three types of vehicles after shielding corrections have been subtracted from unshielded levels. Then, the

levels (automobiles—53 dB; medium

trucks—50 dB; and heavy trucks—65 dB)

are summed to give,

50 ) diff. = 3

53) add 2 55 | diff. - 10

65 5 addO

These calculations indicate that heavy

truck traffic is the predominant source of noise from Highway ii-1, even though

heavy trucks comprise only 7 percent of the total daily traffic volume. The total noise due to Highway *1 could be lowered if the height of the earth berm were

increased (hence, the attenuation), or if the truck traffic volume were reduced.

STEPS H3-H6, H14 TOTAL NOISE LEVEL

FOR HIGHWAY -2

Similar results are obtained for Highway

#2 by performing these same calculations, except there is no medium truck

component and no shielding corrections.

The A-weighted day-night sound levels are 52 and 58 dB for autos and heavy

trucks, respectively. The total noise due

to Highway #2 at the building site is an A-weighted day-night sound level of 59

dB.

Heavy truck noise is also the predominant

source of noise from Highway #2. The

total noise due Highway #2 could be lowered if the heavy truck traffic volume were

reduced or if a barrier of sufficient height were constructed.

STEP H15 TOTAL NOISE LEVEL FROM

HIGHWAYS #1 AND #2

The levels from the two highways are combined to obtain the total level at the building site due to all highways. This combination gives a total A-weighted day-night

sound level of 66 dB. From these values,

it is seen that the total noise at the building site from the two highways is pre- dominantly due to the heavy truck component of Highway #1.

Railway Noise Prediction

As seen from the map of the area, Figure

5.5-8, there is also a railway which affects

this hypothetical building site. This railway

consists of two tracks and is shielded from

the building by an earth berm.

STEP R1.1 RAILWAY TO BUILDING

SITE DISTANCE

First, the railway-building site distance is
Figure 5.5-8. Local Map Showing Details of Railway.
Railway Worksheet 1

Building Project

Location A/^sr /f/akwaus /S, g

Owner /l^^ Designer 0# UU^^

S

Railway Number

Site poinl or building room tor whicfi soun*1 pre^-i^ff; levels are being eslimaied

Dale Revi5er1

Railway—Building Site Distance: D (Feet) S70

Freight Trains

Conventional

P.issenger Trains Rapid Trdn'.il Train-i Does this type of train use

the track being analyzed? yes

Diesel-Electric or All-Electric Locomotive OB

NL DE

NL

Average Train Speed, s mph SO ?0

Average number of cars, nc /OO /o

Average train length, LT, feet ssoo 7^0

Average Number ol Passbys

a) Leq(1) : Nl

b) Leq(8) : N8

c) Leq(24) ; N24

d) Ldn 30 10

Diesel-Electric Locomotive v////////z^//////zzzzzz^. Reference Level, LS 9^ 97

Distance Attenuation, DAL /5'

Railway Cars

Reference Level. CL 90

Duration Factor, CD /9

Track Characteristics, CT s s

Distance Attenuation, DAC /7 17

Predicted Noise Levels

Diesel-Electric Locomotive

Railway

Cars

Diesel-Electric Locomotive V77///////ARailway Cars Railway Cars

a) Leq(1)

CN1

CI

Leq(1) No Shielding

Total Shielding Correction (Railway Worksheet 2)

Leq(1) Corrected for Shielding CN8 ///////////a

C8

b) Leq(8)

Leq(8) No Shielding

Total Shielding Correction (Railway Worksheet 2)

Leq(8) Corrected for Shielding CN24 y/T?'////////

C24

c) Leq(24) Leq(24) No Shielding

Total Shielding Correction (Railway Worksheet 2) Leq(24) Corrected lor Shielding CN 90 90 90

20 /7 20 20

d) Ldn

Ldn No Shielding 5S S9 53 57

Total Shielding Correction (Railway Worksheet 2) Ldn Corrected for Shielding

Total Railway Noise 59 v///////^^///A/////////^^

Figure 5.5-9. Railway Worksheet 1 for Railway of Example.
98

Railway Worksheet 2

Building Project

Location

Owner Modern Reaf'^cj

Railway Number

Site point or building room for which, sound pressure • levels are being estimated "T^ft ^ItiOtr fs/\A/

Designer C 2o^^ S

Date / Ja/y 77 Revised

Railway—Building Site Distance: D (Feet)

Shielding Geometry DB HB

32:

hB

no'

Elevated Railway

DE

Depressed

Railway

HD hD

Path Length

Difference

Ac

Railway Cars

DieselElectric Locomotive 62.36'

Be Cc

CI

Lc

Railway Cars Diesel-Electric LocCorrection For

"Infinite" Shielding Element CSC CSL

Included Angle Ratio, RA

Correction For

"Finite" Shielding Element

Railway Cars

CSC

Building Barrier

Vegeiation dw

Diesel-Electric Loc.

CSL

2

CSB

CSV

Railway Cars Diesel-Electric Loc

Total Shielding Correction CSC CSB - CSV CSL - CSB - CSV

Track Characteristics

a b c d

Welded

Track

Jointed Track

Presence .of Switching Frog

or Grade

Crossing

Radius of Tight Curve « 900 Feet)

in Feet

Bridgework

Concrete

Structure

Steel Girder

with Concrete

or Open Tie Deck

Steel Girder

with Steel

Plate Deck 1^

Figure 5.5-10. Railway Worksheet 2 for Railway Example.
99

Proposed

Building

hB ^ 65' I

Railway

I

Earth Berm \^

HB 32' T

DB = 810' D = 870'

Figure 5.5-11. Cross-Section Showing Railway Earth Berm.

determined from a map of the local area

(Figure 5.5-8). This distance is approximately 870 feet. This value is recorded on both Railway Worksheets 1 and 2, Figures 5.5-9 and 5.5-10, respectively.

STEP R1.2 TRACK CHARACTERISTICS

The track is welded and there is a steel girder bridge with a concrete deck within

2D (1740 feet) of the intersection of the railway with the nearest perpendicular

distance (see Figure 5.5-8).

STEP R1.3 BARRIER DATA

The necessary distances for evaluating

the shielding provided by the earth berm

are determined from a cross-sectional

drawing of the railway (Figure 5.5-11).

These distances, which are determined

for the top floor (worst case as far as

shielding is concerned), are:

D = 870 ft HB = 32ft a = 110°

DB = 810ft hB=-65ft

These values are recorded on Railway

Worksheet 2 (Figure 5.5-10).

STEP R1.4 VEGETATION AND

BUILDINGS AS BARRIERS

There is no vegetation or intervening rows

of buildings that would effectively shield

the roadway from a room on the top floor.

As mentioned previously in the highway

noise predictions, if a room on the ground

floor were analyzed, shielding due to vegetation or intervening rows of buildings

might have to be taken into account. Also,

the shielding due to the earth berm would

be different for the ground floor.

STEP R2 TRAIN DATA

It is determined that only freight trains and

conventional passenger trains use the track and that they are normally pulled by

diesel-electric locomotives—on average, two locomotives for freight trains and one

for passenger trains. Average train speeds

are 50 mph for freight trains and 80 mph

for conventional passenger trains. The

average train length is not available, but the average number of cars is estimated

to be 100 for freight trains and 10 for conventional passenger trains. The train lengths are then estimated to be

LT = 55 X nc = 55 X 100 = 5500 feet

(freight trains),

LT = 75 X nc = 75 X 10 = 750 feet (conventional passenger trains).

The average number of passbys is ND = 15, NN = 5 (freight trains),

ND = 30, NN = 10 (conventional

passenger trains).

These values are recorded on Railway

Worksheet 1 (Figure 5.5-9).

STEPS R3-R5 DIESEL-ELECTRIC

LOCOMOTIVE NOISE

LEVEL FOR FREIGHT

TRAINS

Using the average speed, S = 50 mph, the reference level is determined from Fig- ure 5.3-8, LS = 99 dB (STEP R3). From

Figure 5.3-9 (STEP R4) the distance atten- uation is determined to be,

DAL = 15 dB. The factor CN (STEP R5.4)

is calculated as: CN = (ND + 6NN) NL =

(15 4- 6 X 5)2 = 90

With this value, CDN is determined from

Figure 5.3-10 to be approximately 20 dB.

The unshielded A-weighted day-night

sound level is then calculated,

Ldn = LS + CDN - DAL - 49 =

99-1-20 - 15 - 49 = 55 dB.
100 STEPS R6-R10 RAILWAY CAR NOISE

LEVEL FOR FREIGHT

TRAINS

Using the average speed of 50 mph, the

reference level is determined from Figure

5.3-11, CL = 84 dB (STEP R6). The

passby duration factor (STEP R7) is deter- mined from Figure 5.3-12 to be, CD = 19

dB. For welded track and a steel girder

bridge with a concrete deck within 2D

(1740 ft), the track adjustment factor (STEP R8) is 5 dB (Table 5.3-1). The dis- tance attenuation for railway cars (STEP

R9) is determined from Figure 5.3-9,

DAC = 17 dB. The factor CN (STEP

RIO.4) is calculated as, CN = ND + 6NN = 15 + 6X5 = 45

With this value for CN, CDN is determined

from Figure 5.3-10 to be approximately

17 dB. The unshielded A-weighted daynight sound level is then calculated,

Ldn = CL + CD + CT

4- CDN - DAC- 49,

Ldn = 84 + 19 + 5 + 17 - 17 - 49 = 59 dB.

STEPS R3-R10 CONVENTIONAL

PASSENGER TRAIN

NOISE LEVEL

These procedures are repeated for conventional passenger trains using the appropriate speed, train length, and number

of passbys listed on Railway Worksheet 1 (Figure 5.5-9). The calculated results,

excluding shielding, are, Ldn = 53 dB for the diesel-eiectric locomotives and Ldn = 57 dB, for the passenger coaches.

STEP R11 PATH LENGTH DIFFERENCE

Next, the shielding adjustments are determined for the earth berm. The path

length difference for railway cars is, Ac = VHB' + (D - DB)^ =

V32^ + (870 - 810)^ =: 68.0 ft. Be = V(HB + hB)^ + DB'

V(32 + (- 65))' + 810' = 810.67 ft, Cc = VhB' + D' =

V(- 65)' + 870' = 872.67 ft, Lc = Ac + Be - Cc = 6.25 ft. Similarly the path length difference for diesel-eiectric locomotives is, A/= V(HB - 15)' + (D - DB)' =

V(32 - 15)' + (870 - 810)' = 62.36 ft, B/ = Be = 810.67 ft, CI = V(hB + 15)' + D' =

STEP R12 SHIELDING CORRECTION—

"INFINITE" BARRIER

The A-weighted shielding corrections are determined from Figure 5.3-13 to be,

CSC = 12 dB (railway cars),

CSL = 5 dB (diesel-eiectric locomotives).

[Note that these values of attenuation are

for a room on the building's top floor, which for this example is the worst ease.

If a room on some other floor is of interest,

the values of CSC and CSL should be re- calculated.] These values of CSC and

CSL are recorded on Railway Worksheet

2 (Figure 5.5-10).

STEP R13 SHIELDING CORRECTION—

"FINITE" BARRIER

For this case the included angle (a =

110)° is less than 170°, and the shielding

corrections must be adjusted to account

for this. The factor RA is calculated to be, a 110°

RA = = = 0.61. 180° 180°

With this value the adjusted shielding cor- rections are determined from Table 5.3-2,

CSC = 4dB;CSL = 2dB.

These values are recorded on Railway

Worksheet 2 (Figure 5.5-10). Note the

large reduction in barrier attenuation, particularly for railway cars (12 dB to 4 dB),

because of the barrier's finite length

(a < 170°). This illustrates the importance

of maximizing a barrier's length, hence its included angle so that sound cannot prop- agate around the ends.

Now skip to Step R16, since Steps R14

and R15 are not needed for this example.

STEP R16 TOTAL RAILWAY NOISE

LEVEL

The total railway noise level is computed

by combining the Individual components

calculated in the previous steps. First, the shielding corrections from Railway

Worksheet 2 (Figure 5.5-10) are subtracted from the unshielded levels. Then

the levels are combined using Table

5.3-4 to give the total A-weighted day-night

sound level for railways to be used in Chapter 6.

51 ^ diff. = 2

V((- 65) + 15)' + 870' = 871.44 ft, U = 0.25 (A/ + 8/ — CI) 0.40 ft.

53

53.

55

add 2 55

diff. = 2 add 2

-57

[diff. = 2

add 2

-59 dB.
Aircraft Worksheet 1

Building Projerl 'O' «JC-0^C< fDaKTrVtC^\r pomi O' uuiiuiny luuni lur «iu.n .^jn, |ji..,,ur.. ^ ' levels are being eslimalet) JIfyp^ ^J^V

Location vVe^/" ///^/iUj3£^S np.irjnpr C Suj^ ^

Contour Maps Available

1

If Building ;s on or very near Contour iti or ^f2. Record that value on Line 11

If not. obtain the data of Lines 2 and 3»

2 Contour Values CNR or NEF #1 CNR or NEF #2

3 Building Location Between Contours Stl and ir2

XI X2 R C5 CIO

-4 CNR or NEF Value At The Building Site Also Record on

Line 11

Contour Maps Not Available

5 Number of Jet Operations

NJday NJnight NJefl

10

6 Airport Category (Check One)

2 3 4 \^

7

1' building is on or very near the NEF 30 or NEF 40 Contour, record that value on Line 11.

It not, obtain the data on Line 8.

8 Building Location Between NEF 30 and NEF 40 Contours

XI X2 R CIO 3,000 /./ b

9 NEF Value At The Building Site 3^ Also Record on

Line 11

10 Number of Operations

NJday NJnight N(8) N(1)

1 t CNR or NEF Value

At The Building Site

12 Convert CNR to NEF Value

13 Aircraft Noise Level At The Building Site

1) 1-Hour Energy Equivalent Sound Level, Leq(1)

R1 Leq(1)

2) 8-Hour Energy Equivalent Sound Level, Leq(8)

R8 C8 Leq(8)

3) 24-Hour Energy Equivalent Sound Level, Leq(24)

R24 C24 Leq(24) i

4) Day-Night Sound Level, Ldn

Ldn

Figure 5.5-12. Aircraft Worksheet 1 for Airport of Example.
Figure 5.5-13. Mapping of Approximate NEF Contours for Runway #1.
"103 Since the four component noise levels are about the same value, there is no dominant component as there is for highway

noise (heavy trucks). Comparing the total highway noise level to the total railway

noise level (about 66 dB versus 59 dB),

it is obvious that highway traffic is the predominant source of noise for the building site (without considering aircraft noise). Hence, even though the railway

noise level could be lowered by increasing the height or the length of the barrier, the total site noise would not significantly

change.

Aircraft Noise Prediction

As seen from the map of the area, Figure

5.5-1, there is an airport which affects this hypothetical building site. This commercial

airport consists of two major runways which

handle a variety of air traffic including jet aircraft. The end of Runway #1 is about one mile from the building site.

STEP A1 AIRPORT DATA

First, it is determined that noise rating contour maps have not been constructed.

Since there are no contour maps, STEP

A1.3 must be performed. The number of "daytime" jet operations is, NJday = 25; and the number of "nighttime" jet operations is NJnight = 10. Since the metric

being used is Ldn, no further information

is needed on the number of operations

(STEP A1.4). These values are recorded on Aircraft Worksheet 1, (Figure 5.5-12).

Now skip to Step A3, since Step A2 is not needed for this example.

STEP A3 NEF RATING AT BUILDING

SITE—CONTOUR MAPS

NOT AVAILABLE

The "level of activity" of the airport is based on the effective number of jet operations given by,

NJeff = NJday -f 17 NJnight =

25 + 10X17 = 195.

From the data of Table 5.4-2, this corre- sponds to airport category 2. Approximate

NEF contours are mapped as shown on

Figure 5.5-13 for Runway #1, because

this is the runway nearest to the building

site and hence the one most likely to af- fect the proposed building. Since the

building is located between the NEF 30

and NEF 40 contours, an interpolated

value must be calculated. First, the dis- tance ratio, R, is calculated as follows: X2 5000

R = — = = 1.1. XI 4500

With this value, the factor CIO is deter- mined from Table 5.4-4 to be CIO 6. The rating at the building site is then ap- proximated as, NEF = 40 - CIO - 40 - 6 = 34. STEP A4 AIRCRAFT NOISE LEVEL

The A-weighted day-night sound level is then calculated to be,

Ldn = NEF + 35 = 34 + 35 = 69 dB.

Thus, the A-weighted day-night sound

level for aircraft to be used in Chapter 6

is 69 dB.

Total Building Site Noise Level

The A-weighted day-night sound level contributions from the two highways, railway

and airport are. Highway Traffic 66 dB,

Railway 59 dB,

Aircraft 69 dB.

The total exterior noise level at the building

site, which is the summation of these four contributions, is an A-weighted day-night

sound level of 71 dB. The two predominant

sources of noise at the site are aircraft and

heavy truck traffic on Highway #1. The

highway traffic noise could be reduced by

increasing the height of the earth berm

along Highway #1, but this would have no

effect on aircraft noise. The aircraft noise

level could be lowered by reducing the

number of operations, in particular the number of "nighttime" operations, but to effectively lower the total exterior noise level at the site, the contributions from both sources would have to be reduced.

Chapter 6

How to Make an Analysis of

Outdoor Activity Area and

Indoor Sound

You have now identified potentially trouble- some source's of higiiway, railway, and/or

aircraft noise near your building site; in Chapter 4 you selected a point, or points, on your site for estimating the summed

effects of sound from more than one trans- portation system source; and in Chapter

5, you estimated these separate source

levels. Here in Chapter 6 you will make an

estimate of the sound levels. Here in Chapter 6 you will make an estimate of the sound

levels in outdoor activity areas and an initial analysis of the rooms in your building

scheme to see if the indoor sound levels will exceed the noise criterion levels you se- lected in Chapter 3. If the sound levels in your outdoor activity areas or building's

interior rooms do not exceed the selected

noise criterion levels, you have a building

scheme which should be satisfactorily quiet

for its occupants. If, however, the sound

levels exceed the selected noise criterion

levels, you will probably want to reduce

the sound levels in the rooms by employing some of the design alternatives discussed in Chapter 7.

Outdoor Activity Areas

On your proposed site you may have certain areas designated for outdoor activities. The

particular use of these outdoor areas depends on the type of building you are designing, and could be the yard around a family dwelling, a park or walking mall adjacent to an office building, a courtyard

for an apartment building, a schoolyard, a playground, etc. Since these areas are designed mainly for recreational use over extended periods of time, you must be con- cerned with their outdoor noise levels, and

you will recall from Chapter 3, that the sug- gested noise criterion for outdoor noise

(especially for residential occupancies) is an Leq or Ldn of 55dB.

The total outdoor noise level is obtained

by combining the noise levels generated

by each of the transportation systems, as

calculated in Chapter 5. Since these lev- els are logarithmic in nature, they cannot

be simply added together or averaged

to get the total noise level. Instead, they

are combined, two values at a time, with

the use of Table 6-1 (same procedure as STEPS H14 and R16 for combining indi- vidual components to get the total highway and railway noise level respectively).

Starting with the two smallest levels, subtract one from the other to get the differ- ence. With this value go to Table 6-1 and

determine the level adjustment which is to be added to the larger of the two original

noise levels. Now repeat this procedure

with this adjusted level and another of the transportation system noise levels. Continue

this computation until all components have

been combined into one value. For example,

consider the hypothetical case given in Section 5.5, where there are two highways,

a railway, and an airport which generate

noise heard at the building site. The A- weighted day-night sound levels are: highway 66 dB

railway 59 dB

aircraft 69 dB.

The total outdoor day-night sound level is.

59 \ diff. = 7

} 67

66) ^^^^ diff. = 2 71dB.

add 2 69 J

Table 6-1. Transmission and Level Adjustments for Shell Isolation Ratings

and Noise Levels.

Absolute Difference Transmission and

Between SIRs or Level Adjustment

Noise Levels

>10 0

4-9 1 2-3 2

0-1 3
After you have determined the total sound

levels for the outdoor activity areas on your

site, compare their values with the noise

criterion levels for such areas as discussed

In Chapter 3. If the estimated sound levels are less than the noise criterion levels there

will probably be no noise problems; but

if the noise criterion levels are exceeded,

these areas may not be fit for outdoor use.

if noise problems are due to aircraft fly- overs, there is no simple solution aside from

choosing a new site. If noise problems are due to ground transportation (highways

and/or railways) you may be able to construct sound barriers which can reduce

the outdoor noise levels below the noise

criterion levels. Also, you may be able to orient the building in such a way that the

building itself will act as a barrier and

shield the outdoor areas. This, of course,

will depend on the size and location of the

outdoor areas relative to your proposed

building. These and other design alternatives are discussed in Chapter 7.

Interior Sound Level

The prediction of interior sound levels due to exterior transportation system noise sources will be determined by combining

information obtained in preceding chapters on exterior noise levels with estimates of the noise isolation that will be afforded by

the building shell, consisting of walls, roofs,

and floors exposed to exterior noise. This

guide's method is to perform an analysis,

which presumes that you now have completed a building scheme in sufficient detail to perform such an analysis. It is fur- ther presumed that your building scheme

is somewhat fixed, but still sufficiently flexi- ble to permit room-by-room design revisions

to reduce sound levels in these rooms below

the noise criterion levels. The acoustic analysis of your building is to be made on a room-by-room basis. This

approach respects the physics of sound

propagation . . . the sound travels from

its source to the proposed building shell, and then is partially transmitted to the in- terior through the shell itself, or penetrates

the shell through any openings. Once in- side a room, the sound is absorbed by the

surfaces of the room and its furnishings.

The guide's method presumes that interior room walls prevent the spread of sound

to adjacent rooms.

it is presumed that you will want to estimate

the maximum protection against external

noise that your building can provide. Obviously, protection is reduced by such ele- ments as open windows and doors, or by

ventilation ducts or apertures leading directly to the exterior through which sound

energy can enter the building. For this rea- son, the design guide's procedures assume

that all ventilation is forced, that the ventilation openings to the exterior are well muffled, and that ali windows and doors are

closed. Brief indications are given tovi^ard the end of this chapter of a procedure

which may be used to estimate the amount

of protection provided by the building shell when the windows or doors are open, al- though you will ordinarily not be concerned

with the (reduced) protection provided in this circumstance.

Design Strategies

Although this design guide simplifies the

calculations, these computations take time,

and you will probably not want to make a

calculation for each room ... at least, not

at the outset. Instead, you will want to select representative rooms, determine whether

or not their sound levels will exceed the

noise criterion levels, and then extrapolate

these findings to other rooms. Moreover, you will probably want to adopt

in advance some strategy for dealing with

the results of your room-by-room calculations to keep the number of computations

to a minimum. If you could be sure that the sound level for each room in your

building scheme would just meet its selected noise criterion level, such a stra- tegy would not be needed; but, such an

ideal situation is unlikely. Here are some

suggested strategies to reduce the number

of room calculations. Figure 6-1 illustrates three strategies.

Strategy 1. No room shall have a sound

level which exceeds its selected noise cri- terion level. To pursue this strategy, choose

the room in your building which has the

lowest noise criterion level, and the greatest exposure to exterior transportation sys- tem noise. This room presents a potentially

difficult design challenge and is called a "worst case" room. Run a calculation on

this trial room, if the sound level within

this room is at or below the selected noise

criterion level, you have satisfied the stra- tegy's objective for this room, and perhaps

for all rooms in the building. If, however,

there is excessive noise in this room . . . interior sound level greater than the noise

criterion level . . . you should improve the

room's acoustical properties and run the

calculations again. This should be repeated

until the noise criterion is satisfied for this

first trial room. Then, select the next "worse

case" room, and proceed in the same manner until its noise criterion is satisfied. Then select the third "worst case" room,
107

strategy 1

I t *

"Noisy" Rooms Above

Criterion Level Improved

Noise Crilerion Level

Strategy 2

Rooms at or Below

Criterion Level Are

Not Ctianged

"Noisy" Rooms Above

Criterion Level Improved

I rNoise Criterion Level

I .

strategy 3

Rooms at Criterion Level Not Ctianged Rooms Below Criterion Level Are Degraded for Cost Savings

"Noisy" Rooms Above

Criterion Level Improved

Noise Criterion Level

1 ,

Exceptionally "Quiet" Rooms

May Be Degraded to Make

Cost Savings

Figure 6-1 . Suggested Strategies for Dealing with Noise Criteria. and so on, until you come to the room

which just satisfies its noise criterion. Then

stop. At this point you can presume that

all other rooms satisfy their noise criteria. Hence, you have satisfied the objective of

this strategy.

Strategy 2. The sound level for every room

shall just meet its indoor noise criterion

level. The disadvantage of Strategy 1, is that it may be overly expensive, since there

will be rooms, perhaps many rooms, which

might have sound levels lower than their noise criterion levels. Strategy 2 requires

first that Strategy 1 be followed for all rooms with noise problems, improving them

one by one until each room just satisfies

its noise criterion. Strategy 2 then adds a second stage, that of degrading the acoustical properties of all rooms which have

sound levels less than the noise criterion

levels. Of course, judgment must be exer- cised to ensure that cost savings would

result from the design degradation of these

"over-designed" rooms, if there would be no savings, it is obvious that the rooms

should not be degraded.

Strategy 3. The average sound level for the building's rooms shall not exceed their respective noise criterion levels. The essence

of this strategy is that by averaging the difference between the selected noise cri- — terion levels and the interior sound levels,

and by requiring that the average difference

be zero, the average noise level of the rooms of the building will not be greater

than the noise criterion level. The risk here

is that a solution satisfying an average

sound level could be achieved by virtue of a large number of rooms which have sound

levels far above their noise criterion levels, balanced by rooms with sound levels well below their noise criterion levels. The occupants of noisy rooms would suffer from

these noise conditions, and would hardly

be comforted by the knowledge that other

occupants had highly favorable sound conditions. To overcome this, you could set an upper limit, say 5 decibels above the noise criterion level, which would be the maximum sound level for any room. You

will want to adopt some special version of

this strategy to account for variations in room-by-room noise criterion levels and

noise exposures.

The above are three strategies which you

may wish to adopt to reduce the number

of room calculations, and to deal with the

results of your calculations. Perhaps you

can adopt other strategies which are

equally useful. In any event, you should

probably begin by running two trial rooms

. . . your "worst case", the room with the lowest noise criterion level and the greatest

exposure to transportation system noise,

and . . . your "best case", namely, the room with the highest noise criterion level and the least exposure, but still some exposure, to exterior transportation system noise. The results of these two room calculations

will give you the expected range of indoor

sound levels which you can then compare

with noise criterion levels.

How to Choose "Worst Case" and "Best Case" Rooms for Trial Calculations

Choosing "worst case" and "best case" rooms depends upon ... (1) the location of the sources of transportation noise as dis- cussed in Chapter 4, (2) the type of building or room occupancy and its occupants, and

(3) the physical characteristics of the building shell and the room whose sound level is to be calculated. These building shell and room characteristis are as follows:

• Shell construction . . . "monolithic" or composite

• Shell porosity, or air leakage, particularly

that associated with "cracks" around

doors and operable windows, and the

joints of curtain walls, etc. • The area of shell members enclosing a room ... a shell member is defined as a portion of the exterior walls, roofs, or exposed exterior floors of a building
"108 which separate a room from the out-of- doors. A component is a portion of a

shell member having a construction or materials different from the parent shell member; for example, a window is a component of a wall.

• Room geometry . . . includes the area of the shell member(s) transmitting sound

from the exterior, and the total surface area of the room.

• Room absorption . . . based upon the total area of all walls, floors, and ceilings of the room together with the combined

surfaces of equipment and furnishings in the room, and the sound absorptivity of these various surfaces.

The above characteristics permit the cal- culation of the sound isolation of each shell member transmitting exterior sound to a room. The sound isolation for each shell member is then combined with that for all other room shell members to yield the total sound isolation for the room. We noted previously that you won't want to make any more room calculations than

necessary. If, however, you have a build- ing scheme with rooms that vary widely

in floor area, room geometry, room sound

absorption, and room occupancy (hence

noise criterion levels) . . . and if the rooms

also have varying exposures and differing

shell member constructions . . . then no one room is representative, and you will need to make separate calculations for each

room. On the other hand, many proposed

buildings will have rooms that are similar

in floor area, geometry, sound absorption,

occupancy, exterior noise exposure, shell construction, and so forth. For these build- ings you can choose representative rooms

for interior sound level calculations, and

spare yourself a good deal of time and

effort. One option is to make calculations for a

single room which you think has "average"

design features and "average" exposure

to transportation system noise. Hopefully,

such a single set of room calculations would

yield the "average" indoor sound level for your building scheme. More likely, however,

you will remain in doubt as to whether or not the selected room was truly representative of average conditions.

A better option is to run calculations on the "worst case" and "best case" rooms. This

adds only one set of calculations and tends

to establish not only the range of high

and low indoor sound levels, but also per- mits you to make a better estimate of "average" conditions midway within this range.

Examples of Choice of Representative

Rooms

Now let us discuss how to choose repre- sentative rooms for a detached, singlefamily dwelling, a school, and a ten-story

apartment building.

For the single-family dwelling, especially a small or medium-sized one, the building

itself would not provide much shielding as

a noise barrier; and thus in many cases the

exterior sound level can be assumed to be

equal on-all four sides of the dwelling. Hence,

the room selections could disregard the relative locations of the transportation system

sound sources, and be based solely upon room configurations and room noise cri- teria. If one noise criterion level were

selected for all rooms, then the room

having the greatest external surface area

. . . probably the living room . . . should

constitute the "worst case", and per- haps the kitchen should constitute the

"best case". If different noise criterion levels were selected for different rooms, the lowest noise criterion levels would probably

be for the bedrooms . . . thus, the bedroom

having the greatest external surface area should be taken as the "worst case"; conversely, a large room with the smallest

external exposure and the highest noise

criterion level should become the "best

case".

Now consider the selection of representative rooms for a school like the one shown

in Figure 6-2. Since the building is only

three stories high, and the transportation

system sound source is a few feet above

grade, the distance from source to receiver,

hence the resultant sound pressure level would vary little from one story to the next.

Figure 6-2. "Worst Case" Room for School.
109 A top story room would receive almost the same sound level as a \ower story room,

but would have roof exposure in addition to wall exposure. Hence, a top story room near

the transportation source should be selected as a "worst case" representative room. However, since the building is very long and

wide, the horizontal distances from the sound source could be an important consideration and may cause sound levels to drop appreciably from a near corner of the school to a distant corner. Naturally, this variance is increased when the sound

source is quite near the building. Moreover, the type of room occupancy will vary

greatly in a school, and this variance may

be reflected in different noise criteria, say,

for an auto mechanics shop or a library.

The shop could have a noise criterion level of 60 dB, whereas the level for the library

could be as low as 30 dB. In addition if the

principal source of noise is located on one

side of the building, the building itself may

provide beneficial shielding for rooms facing

away from the sound source. An allowance

of 3 dB may be made for this shielding

effect. You will need to consider all these

factors in choosing the "worst case" and

"best case" rooms. As a third example, consider the ten-story

apartment building shown in Figure 6-3. Assume that this simple tower has two

windowed facades and two flanking walls.

In such a building it has been customary to charge a higher rent for higher floors than

for lower floors. Accordingly, the designer

may wish to provide a relatively quieter

environment on the upper floors and select

for them a lower noise criterion level. Aside

from this sort of consideration, however,

you can treat all stories equal, and let the

location of the transportation system sound

source and the building characteristics control your selection of representative rooms

for trial calculations.

The apartment tower we are considering is a good example for our purposes since it

is representative of many buildings having

heavy end-walls and windowed facade walls. We will discuss the building with respect

to the three types of transportation system

noise as it might come from several source

locations.

Usually, if a building is exposed solely

to aircraft noise, the building's orientation will make little difference, particularly

if air traffic patterns vary. When averaged

over many flyovers, sound pressures will not be consistently lower at any one side

of the building shell. Thus, the selection

of a trial room can be based upon the

room's exterior shell area, and upon critical

Facade

(6-3a) Highway or Railway Noise Impinging

Upon a Flanking Wall.

Flanking Wal

(6-3b) Highway or Railway Noise Impinging

Upon a Facade Wall.

Figure 6-3. "Worst Case" Room for a Ten-Story Apartment Building.

noise criteria. Moreover, since apartment

buildings will usually have a single noise

criterion for all outside rooms, the trial room can be selected solely on the basis

of exterior shell area. Hence, a large, topstory, corner room should be chosen as

the "worst case" for trial calculations. A

lower floor, small, non-corner, outside room

should be taken for the "best case." Note

that this recommended "best case" room

is still an outside room, and consequently

will have some exposure to aircraft noise. As such, this "best case" room could obviously not be as quiet as an interior room

. . . one having no exterior shell exposure

to aircraft noise. Following the above ap- proach, the sound levels in the "worst case" and "best case" rooms will thus be

representative of the range of sound levels

in the rooms exposed to aircraft noise. Now consider highway and railway noise

sources. For these, the selection of trial rooms will depend heavily upon the location of the source, keeping in mind that highways and railways constitute line sources. If the sound propagates toward a

flanking wall, as in drawing "a" of Figure
6-3, then the distribution of sound levels over the two facade walls will be similar

with higher sound levels at the end of the facade wall near the source, diminishing

to lower levels away from the source. Thus,

representative trial rooms can be selected

from either of the two facade walls because

it is probable that the flanking walls of heavy construction and with no windows

would not transmit as much sound energy

as either of the facade walls. The "worst case" should be selected from rooms near

the source which have low noise criteria and large exterior shell areas; the "best

case" should be chosen from rooms far from

The source which have high noise criteria and small exterior shell areas.

If the highway or railway sound propagates

toward a facade wall, as in drawing "b" of Figure 6-3, not one but two pairs of repre- sentative rooms will be needed. The reason

for this is that the building itself acts as a

barrier which shields rooms on the facade

wall away from the source. Hence "worst case" and "best case" rooms should be

chosen from both the near and the distant

facade walls.

The distribution of sound levels across the

facade wall near the source is often fairly

uniform. The prediction of interior sound

levels for rooms with exterior walls on this facade can be handled readily by the pro- cedures in this design guide. However, this does not hold for the facade wall facing

away from the source. Here, the sound level distribution is not regular . . . sound will be

diffracted around the corners of the building

possibly making the end, outside rooms

noisier than central, outside rooms. The same phenomenon may cause sound levels

to be higher for top-story rooms than

ground-floor rooms. To estimate room sound levels on the far facade. The sound levels at the far facade

shielding effect of the building itself be dis- regarded, which is a conservative approach,

or that a maximum reduction of 3 dB be

made at the central portion of the shielded

facade. The sound levels at the far facade

wall will, of course, be somewhat lower due

to the greater distance of this facade from

the source (without consideration of the

shielding effect). These levels can be esti- mated by a set of Chapter 5 calculations separate from those for the facade wall near the

sound source; or, these latter calculations can simply be reduced by the very crude

rule of thumb that sound levels decrease

by about 4 to 6 dB for every doubling of the distance from the source.

With respect to exterior transportation

sources, all the other outside rooms of each facade of the building should have

sound conditions falling between your "best

case" and "worst case" rooms. However,

don't hesitate to make additional trial cal- culations if needed to positively identify

your "best case" and "worst case".

If the sound source is nearby and low,

choose a first-story, outside, corner room

from the facade facing the noise source as your "worst case"; and from the same

facade a top story, outside, central room

as your "best case". It is common practice

in such buildings to design the ground level story for non-residential uses and to construct this first story differently from upper

stories. If you have followed this practice,

choose your "worst case" apartment room

from the second story. Note that in all these

selections, the "best case" is not one

which would receive the least exposure

to exterior, transportation system sound, be- cause both basement rooms and inside rooms would receive less exposure to sound

than the "best cases" selected above.

Instead, it is the "best case" selected from rooms having a reasonable amount of ex- posure to the sound source. How to Predict the Sound Level in a

Trial Room

Once you select the trial rooms, you can proceed to predict their sound levels using

the special procedure developed for this design guide. Your calculations will be

aided by the use of two worksheets for each

trial room. One worksheet provides a pro- cedure for computing the cumulative Shell

Isolation Rating (SIR) for the room in question, and is caMed the SIR Worksheet (See

Figure 6-4). The second worksheet uses this room SIR together with the sound levels at the building estimated in Chapter 5, to predict the sound level inside the trial room. The second worksheet is called the Room

Noise Worksheet (See Figure 6-5).

The purposes of the following explanation

are twofold . . . one, to familiarize you with some of the principles of sound transmission through a building's shell; and . . . two,

to guide you through the calculations using

the worksheets. A detailed example of the calculations is presented in the concluding portion of this chapter, and you

may find it helpful to refer both to the ex- ample and to the following instructions as you make your own worksheet calculations.

The amount by which the exterior sound

levels are reduced by the building shell is determined by several factors . . .

(1) the area of the room's exterior shell
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Component

Description

Arrange

components

ot

shell

members

in

order

of

decreasing

SIR

for

each

shell

member.

Order

ot

shell

members

is

optional.

*

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Figure 6-4. SIR Worksheet.
Figure 6-5. Room Noise Worl<sheet.

estimation of the isolation provided by the

exterior building shell, a single-figure rating

system, the Shell Isolation Rating (SIR), has

been especially devised for this guide. The

SIR number is a measure of the A-weighted

sound level reduction that can be expected

when certain building shell materials are

used. This rating number is determined

from available laboratory measurements of acoustic transmission loss data versus fre- quency. Selected shell assemblies and components are tabulated with their SIR values

in Appendix A. The technical basis for the

SIR method and a technique for determining this rating for shell assemblies not

listed in Appendix A is explained in Appendix B.

To account specifically for the above effects

of the building shell in reducing exterior

sound levels, you will be using one SIR

Worksheet for each room in your proposed

building for which interior sound level esti- mates are needed. Let's scan the SIR Worksheet in Figure 6-4 and the flow chart of Figure 6-6 to become familiar with the

necessary calculations. The SIR Worksheet

can account for one room having as many

as five shell members, enumerated in Column (a) of the worksheet. Thus, the SIR

Worksheet can handle a free-standing room

such that four walls and the roof are ex- posed to sound energy, or a room canti- levered from the face of a building such

that three walls and the floor and roof of the room are exposed. If you have a room

with more than five shell members, you can

disregard one or two shell members which

acting by themselves would transmit the

exposed to sound ... the greater the

exposed area the more the acoustical

energy (sound) transmitted;

(2) the mass, or weight, per square foot of area of such room shell members as

exterior walls, roofs, and (possibly)

floors which may be cantilevered, supported on piles, or otherwise exposed

to exterior noise . . . heavy shell members, such as concrete or masonry walls,

transmit less sound than lightweight

shell members, such as curtain walls;

(3) air leakage . . . sound energy can readily enter a building even through very small

openings. Thus quality of construction

is important to seal small pores and

cracks. Componentized construction can

transmit noise because of such leakage

through joints between the components;

(4) the room geometry (the ratio of exterior

shell members to room floor area) . . . important in determining the relationship

between the amount of energy entering

the room and its sound level;

(5) the average acoustical absorptivity of the room's interior surfaces . . . carpeted

floors absorb more sound than hard

floors; acoustic ceilings absorb more

than smooth plaster or gypsum board

ceilings; and over-stuffed or heavily upholstered furniture, drapes, and other

sound absorptive elements reduce room

sound levels.

A precise estimate of the sound isolation of the shell would involve an analysis by dis- crete frequency bands using transmission

coefficient data. However, to simplify the
least amount of sound; or, you can combine

pairs of adjacent, similar slieli members,

treating each pair as if it were a single

shell member having the size and componentization of the two shell members put

together. For most rooms, however, the SIR

Worksheet's accommodation for five shell members should suffice.

Since many shell members (such as walls) are made up of more than one component

(such as windows, doors, subpanels, etc.), the SIR Worksheet is arranged to account

for as many as four components within each

shell member; the four being labeled A, B, C, and D down Column (d) of the worksheet.

If you have shell members with more than

STEPS WORKSHEET COLUMNS

POSSIBLY REQUIRED

Step One: Enter room data and data up to 5 shell members, each with up

to 4 components.

Step Two: Compute composite SIRs

for all shell members.

Step Three: Make air leakage adjust- ment for shell members.

Step Four: Make room geometry

correction for sheii members.

Step Five: Make room absorption

correction and compute adjusted

shell member SIR.

Step Six: Combine shell member SIR

values to obtain room SIR.

Step Seven: Tabulate exterior noise

levels.

step Eight: Combine exterior sound

level.

Step Nine: Determine interior sound

level.

Step Ten Compare interior sound

K

level with noise criterion level.

a, b, c, d, e, f, g, h,

i, j, k, i. m. aa

n, o, p, q, r,

V, w, x, y

hh, ii, jj, kk, II, mm,

nn, 00, pp, qq, rr, ss

C, D, E, F, G, H

Figure 6-6. Flow Chart for Steps of the

SIR and Room Noise Worksheets.

four components, you will have to extend

the step-wise procedure for combining SIR

values to yield the appropriate composite

SIR value. The step-wise procedure is straightforward enough that you will have

little difficulty in extending the procedure;

although you may want to make your own

specialized SIR Worksheet for this unusual

case.

In summary, then, the SIR Worksheet can

readily provide the shell isolation rating

for a single room in your building, when

the room has a maximum of five shell members, and when the shell members have a maximum of four components. If these

maxima are exceeded, the special procedures described above can fit your room

into the SIR Worksheet. Now, let's glance

further at the provisions of the worksheet.

Columns (a, b, c, d, and e, g, h, i, J, k, I, and m) are used to enter descriptive and

dimensional data from your building

scheme, as is Column (aa) which provides an estimate of the air leakage based on the

level of workmanship for each shell member. Column (f) receives one SIR for each

monolithic shell member or one SIR for each component of componentized shell members.

The twelve columns after Column (m) are used in groups of four to calculate composite SIRs for consecutive pairs of shell members components. Thus, Columns (n, o, p, and q) are used for the composite SIR

of the two components having the highest

component SIR values (Components A and

B); Columns (r, s, t, and u) are used for the composite SIR for Composite A-B and Component C; and, Columns (v, w, x. and y) are used for the composite SIR for Composite A-B-C and Component D. Monolithic

shell members having a single type of construction require none of the Column (n) through (y) calculations ... the shell member SIR is simply used for calculations

beyond Column (y). Componentized shell members having two types of construction

require the calculations of Columns (n, o, p. and q); shell members with three components require the calculations of the latter columns plus those of Columns (r, s, t, and

u); and shell members with four components

require the calculations of all twelve col- umns . . . (n) through (y).

After the composite SIR (if a composite

SIR is needed) has been calculated for Shell Member Number 1, the other composite SIRs are calculated in turn for all other shell members, as required.
Then all composite (or shell member) SIRs

are corrected for air leakage, room geometry, and room surface absorptivity in Columns (aa) through (gg).

Finally, these corrected SIRs for the shell members are accumulated pairwise to ulti- mately yield the room SIR. These calculations are made in Columns (hh, ii, and jj; kk, II, and mm; nn, oo, and pp; and qq, rr, and ss) using three columns for each pair

of shell members. The cumulative SIR for the last pair of shell members is the Room

SIR, vjh\ch is to be used as the entry in the Room Noise Worksheet to compute the room sound level; and in turn, to compare

these sound levels with your pre-selected

noise criteria. Having described the SIR Worksheet in general terms, let us nov^^ follow its procedures step by step:

Shell Isolation Rating Prediction Method

STEP ONE: ENTER ROOM AND SHELL

MEMBER DATA

Enter shell member data in Columns (b, c, and aa); and enter room data in Columns

(g, h, i, and j). Note that rooms having sus- pended lightweight ceilings can receive exterior sound through portions of shell members extending up through the dead space

of the suspended ceiling. Hence, the room

"height" for noise calculations is not from

the floor to the suspended ceiling, but from

the floor to the underside of the floor or roof slab above the ceiling space.

In using the worksheets all values should

be rounded off to the nearest whole number

in feet or decibels (or decibel equivalents).

The only exceptions are the interpolation

factors, and the fractional area ratios which

should be computed to two places to the

right of the decimal point.

If the shell member is monolithic ... all of brick veneer, or all wood frame construction, or all cinder block . . . then it is a single

component shell member; Columns (k through x) can be left blank; and the shell member SIR from Column (f) can be copied

into Column (y) for the monolithic shell member SIR value. On the other hand, if the shell member has more than one component, then Columns

(k, I, and m) must have entered data. Note

that the components must be arranged in the order of decreasing SIR values. This

will often mean that Component A for a

shell member will overlay the shell member, and will have the SIR value, area, and

overall face dimensions of the shell member itself. However, some care must be

taken in this, for it presumes that the overall shell member will have a SIR value

higher than any other components of the

shell member. Naturally, this would be true

for a masonry shell member (Component

A) pierced by a window (Component B) . . . the masonry has a higher SIR value than

the window. However, consider a lightweight

curtain wall containing several granite

panels. The stone panels, having the higher

SIR value, would in this case constitute

Component A, and the curtain wall would

constitute Component B. The computational procedure requires the area of each component in a componentized shell member, with the exception of the area of the component with the largest

SIR number. In the case of a masonry shell pierced by a window, the area of the overall shell member is entered in Column (c), but is not required in line A of Column (m);

while the area of the window is required

and would be entered in line B of Column

(m). For the case of the curtain wall with

several granite panels, the area of the overall shell member is once again to be

entered in Column (c). The total area of the several granite panels is not required;

while the area of the remaining portion of the curtain wall is required and would be

entered in line B of Column (m).

When a shell member has more than one

component, the shell member's composite

SIR may take a value only slightly higher

than that of the component having the lowest SIR value.

STEP TWO: COMPUTE COMPOSITE SIR

VALUES

For a shell member having two components

(the shell member itself plus one other

component), complete the procedures and

entries of Columns (n, o, p, and q). The

component fractional area of Column (n)

is the ratio of the area of the component

with the lower SIR value to the area of the

shell member itself. The component fractional area is expressed as a decimal fraction and carried to two places to the right of the decimal point.

The difference between SIR A (for Component A) and SIR B (for Component B) is entered as a whole number in Column (o). Column (n and o) values are then used to determine a composite correction factor from Table 6-2, which is entered in column

(P). This composite correction factor is then

added to SIR B to yield the composite SIR

A-B to be entered in Column (q). This value

is also entered in Column (y) to serve as

the composite SIR for the two-component

shell member.
Q >

Z O

< m

< o o t- o o ^

o o ^ o o ^ O O r- O O ^ O O T- O O ^

O O 1-

o o ^ o o ^ O O T- o o 1- O O 1^ O O 1- O O t- O O T- O O T- o o ^ O O 1- o o ^

O O 1- O O 1- O O T- O O 1- O O 1- O O 1- O O TO O 1- o o »- O O T- O O 1- O O

csj CM CO ^ in to hcvj eg CO Tj- Lo CD 1^

C\J CM CO rj- to (D hCM CM CO ^ l/> CD

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CM CM CO Tj- in (D hCM CM CO in (O NCM CM CO ^ in

CM CM CO ^ m to

CM eg CO ^ m CD

CM eg CO ^ m to

CM CM CO in to

CM CM CO in to t-^

CM CM CO in CO NCM CM CO in CD

CM CM CO in CD

CVJ CM CO ^ in CD hCM CM CO in CO

CM CM CO ^ in CD

eg CM CO in to 1^

CM CM CO ^ in CD

CM eg CO in to

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CM eg CO in CD ^-

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T- CM CO in CD to

T- CM CO m in CD

T- CM CO in in CD

T- CM CO CO in CD

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r^h-ootocoo>0)cj)Ooor-cMCMco^inmcDr-.

r--r^cococoCT)cj>0)OooT-CMCMco«*inintDr-.

h-h-.coa3ooo)CJ)<3»oooi-cMCMcO'<rinintohr^r^cococoo)CJ>0)Oooi-CMCMco-*inintDt^

r^r^cooocooicTJcnooo'-cMCMcoTrinmcDr^

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r^h-cococo<35C7>cnooo'-c\jCMcO"*t^in(or^

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r^r*-oooocococj)t3)oooT- r-cgco^'^into

r^t^oococoooo)CJ>0)ooT- i-CMco^^mto

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r^r^oooocooot3)CJ>C7)oo^T- cMcoco^mm

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h-h-r^r--cocococoa)CT5CTOo^i-CMCMcoco'<t h*h-r>-r^COCOCOC001C730>000'^CMCMCMCOCO

s.h^h*r^r^cocoooooo)cj)a>oO'-'-i-CMc\jcM

tDh-r^h-N.h-C0C0C000050>CT>OO^T-i-T-CM

tOCOh-h-I^N-I^COCOOOCOOlOlOOOOO^'-

CDtOCDCOh-h-l^t^r^OOOOCX)COO)0>CJ)0000

CDCOCDtOCDtDh-N.r^h*r-0O00COCO(31OlCD<7)Cr) intntDtotococDtot^h-r^t^i^r^oocococococo

ininininintotocototocDcoh-N-h^^-r^N-i^co intnininininininintDcDtDtDcotococDr^r^h- •^^Tr^Tj-^inmininininLninincototocDcD

^^•^'^^^^^^^^^^^inininintnin

COCOCOCOCOCOCOCOCOCOCO^^'^'^^^^''*"'*

CMCMCMCMCMCMCMCOCOCOCOCOCOCOCOeOCOCOCOCO

CMCMCMCMCMCMCMCMCMCMCMCMCMCMCMCMCMCMCMCM oooooooooooooooooooo

OCO^-COinTt-COCMi— 001COI--tDLn'^COCOCNJCM

T-r-1— 1— v-t-i— i—OOOOOOOOpO

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C7) 0> O Q ?>J CM

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r-- CO 00 CO 00

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cDtocDtDtor^r^r-r^r-cococooa)

inintotDCDCDCDi^r-r^t^r-oococo 0)05 0 0)0)0)0) inininintDcototo(Dtoh-r--h-.f^co ininininininintotDcDCDtotDh-h^

C0C0C0C0C0G000C0tQ0)0)Oa)OO

f^t^r»-N-r>-cofflcocococofficoa3co ^^^ Tj-inLominininintDtotocD CDtotDtos.r^h-r*h>-r^r^r-r^r~>.r^ ^^TT^^-^Tr-^Tj-mLoinintnin inincDtotototototococDtDtototD COCOCOCOCOCO't'^^'^'^'^'^^"^ ^LnininininminLnLnLninminLO

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cocococococococotococococoncn

CMCMCMCMCMCMCMCMCMCgCMOJCMCMOJ

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COCOO)C)0)00)0)0)0)0)0)0'iO)C)

COOOCOCOCOCOQOCOCOOOCOCOCOCOCO

tDCDtOtOtOCDCDCOtOtOCOCDCOtOtD ininminininininininLninininin

COCOCOCOCOCOCOCOCOCOCOCOCOCOCO

CMCMCMCMCMegCMCMCMCMCMCMCMCMCM

ooooooooooooooo

CT)O)O)C)O)O>CJ)O)0)0)O)O)0)O)0) COCOCOOOCOCOCOCOmcDCOCOffiCOCO

(DtDCDtOCOtOtOtOtDCDtDtDCOtDCO

inininininininininLOinmininin

cocococococococococococoococo

cmcmcmcmcmcmcmcmcmcmcmcmcmcmcm ooooooooooooooo

OOoOOOOOOOOOOOO c3)cor^tuLo^cocgi— ocnoor^tom

OOOOOOOOOOOOOOO

l-T-^l--.-l-l-T-T- ,--00000 C3qpp(3pppoppcDc:5(pp

V3aV nVNOllOVUd INiNOdlAlOO

Table 6-2. Composite SIR correction factors.
For a shell member having three components (the shell member itself plus two

other components), complete the above pro- cedures and entries for Columns (n, o, p, and q) and then go on to repeat similar

procedures and entries for Columns (r, s,

t, and u). In this process, the composite

SIR A-B is combined with the SIR C (for Component C). The resultant SIR A-B-C

in Column (u) is also entered in Column (y) as the composite SIR for the three-component shell member.

For a shell member having four components

still another series of similar procedures

and entries are completed, those for Col- umns (v, w, X, and y). Here, the composite

SIR for the four-component shell member

is the SIR A-B-C-D which appears in Column (y).

The SIR value for each shell member must

next be adjusted to account for air leakage.

The SIR values of Appendix A assume

superior workmanship which virtually elimi- nates air leakage. Merely "good" or "aver- age" workmanship will result in holes or cracks which reduce the sound isolation

of the building shell. In addition to holes,

cracks at doors and windows, permanently

open ventilators, and even open fireplace

flues can reduce sound isolation. STEP THREE: MAKE AIR LEAKAGE

ADJUSTMENT

If the workmanship for any shell member Is to be "excellent," you need no adjustment

for air leakage (aa): simply enter the SIR

from Column (y) in Column (bb). If, however,

the workmanship is to be "good" or "aver- age," refer to Table 6-3 to obtain an adjusted

SIR value accounting for air leakage based

upon an estimate of the opening in square

inches per 100 square feet for the shell member in question entered in Column (aa). You may be able to make a good estimate of

air openings in square inches per 100 square

feet from project drawings and specifications. If not you can use as a guide the

estimates of air leakage given below for good and average workmanship and various

types of shell member construction. To esti- mate air leakage corresponding to good

workmanship, use one of the following esti- mates:

a) monolithic

walls 0.75 to 1.5 inVlOO ft^

Table 6-3. Adjusted SIR of Composite Shell Member Dependent Upon

Air Leakage Through Member

SIR of Composite Air Openings in^/lOO ft^ Partition

0.1 0.25 0.50 0.75 1.5 .0 4.5 6.0 7.5 9.0 12.0

62 52 48 45 43 40 37 35 34 33 32 31 61 51 48 45 43 40 37 35 34 33 32 31 60 51 48 45 43 40 37 35 34 33 32 31 59 51 48 45 43 40 37 35 34 33 32 31 58 51 48 45 43 40 37 35 34 33 32 31 57 51 47 45 43 40 37 35 34 33 32 31 56 51 47 45 43 40 37 35 34 33 32 31 55 50 47 45 43 40 37 35 34 33 32 31 54 50 47 44 43 40 37 35 34 33 32 31 53 49 47 44 43 40 37 35 34 33 32 31 52 49 47 44 42 40 37 35 34 33 32 31 51 48 46 44 42 40 37 35 34 33 32 31 50 48 46 44 42 40 37 35 34 33 32 31 49 47 45 44 42 39 37 35 34 33 32 31 48 47 45 43 42 39 37 35 34 33 32 31 47 46 44 43 42 39 37 35 34 33 32 31 46 45 44 42 41 39 36 35 34 33 32 31 45 44 43 42 41 39 36 35 34 33 32 31 44 43 43 41 40 39 36 34 33 33 32 31 43 42 42 41 40 38 36 34 33 33 32 31 42 42 41 40 39 38 36 34 33 32 32 31 41 41 40 40 39 37 36 34 33 32 31 31 40 40 39 39 38 37 35 34 33 32 31 30 39 39 38 38 38 38 35 34 33 32 31 30 38 38 38 37 37 36 34 33 33 32 31 30 37 37 37 36 36 35 34 33 32 32 31 30 36 36 36 35 35 35 33 32 32 31 31 30

35 35 35 35 34 34 33 32 31 31 30 30 34 34 34 34 33 33 32 31 31 30 30 29 33 33 33 33 33 32 32 31 30 30 29 29 32 32 32 32 32 31 31 30 30 29 29 28

31 31 31 31 31 30 30 30 29 29 28 28 30 30 30 30 30 30 29 29 29 28 28 27

29 29 29 29 29 29 28 28 28 28 27 27

28 28 28 28 28 28 27 27 27 27 27 26 27 27 27 27 27 27 27 26 26 26 26 26 26 26 26 26 26 26 26 25 25 25 25 25

25 25 25 25 25 25 25 23 24 24 24 24
b) walls with fixed windows or other

panels 1.5 to 3.0 inVlOO ft', c) walls with weather

stripped operable

windows 3.0 to 4.5 inVlOO ff

,

d) walls with non- weather stripped

operable

windows 4.5 to 6.0 inVlOO ft'. To estimate air leakage corresponding to average workmanship, use one of the fol- lowing estimates:

a) monolithic

walls 1.5to3.0inV100ff,

b) walls with fixed windows or other

panels 3.0 to 4.5 in7100 ff

,

c) Walls with weather

stripped operable

windows 4.5 to 6.0inV100 ff

,

d) walls with non- weather stripped

operable

windows 6.0 to 7.5 inVlOO ff

.

Enter the appropriate value of "Adjusted

SIR based on Air Leakage" in Column (bb)

of the SIR Worksheet.

STEP FOUR: MAKE ROOM GEOMETRY

CORRECTION

For each shell member, enter in Column

(cc) of the SIR Worksheet the ratio of the

shell member area (from Column (c)) to the room floor area (from Column (j)). Refer to Table 6-4 for the value of the room geometry correction factor, and enter it in Col- umn (dd). Note that for all roofs, whether

flat or pitched, the value of the correction

factor is —2.

Table 6-4. Room Geometry Correction

Factors.

Exterior Shell Member Area

Room Floor Area

Correction Factor *

0.94 to 1 -2

0.67 to 0.93 -1

0.50 to 0.66 0

0.37 to 0.49 +1

0.28 to 0.36 +2

0.22 to 0.27 +3

0.17 to 0.21 +4

0.13 to 0.16 +5

0.10 to 0.12 +6

* For all roofs regardless of pitch, use a correction factor of —2.

A portion of the sound energy transmitted

through the shell members is absorbed in- side the room. This absorption is proportional to the total surface area of the interior of the room and the absorptivity of these surfaces. The information of Column

(cc) is based upon an approximation of the

total interior surface area. The Column

(dd) value then enables you to estimate the correction required for the total surface

area, and hence, absorption. This factor,

taken from Table 6-4, is based upon consideration of the room depth as related to

its height and length in terms of the ratio of shell member area to floor area. The computations by which the SIR method was derived were initially based upon the

assumption that the ratio of exterior parti- tion area to floor area would be between

0.28 to 0.36. (For a rectilinear room having an eight-foot ceiling, this corresponds to a room depth from the shell member to the

interior opposite the shell member of 22 to 28 feet.) If the ratio is larger, as is the case when the room depth is smaller,

the room surface area and absorption will be smaller, and the sound level larger. To

account for these geometrical considerations, the SIR value must be adjusted ac- cording to Step Four. Table 6-4 presents

values of the "Room Geometry Correction Factor" to account for the room surface area.

The data of Table 6-4 are for carpeted rooms without an acoustical ceiling and

without heavy drapes. Such a room is pre- sumed to have "medium" reverberation

properties. Rooms having additional acoustical absorption such as an acoustical ceil- ing or drapes covering 50% or more of the

wall area will have lower sound levels. Conversely, rooms without carpet will have

higher sound levels. These differences in room absorption require adjustments in the

shell member SIRs as calculated in Step

Five.

STEP FIVE: MAKE ROOM ABSORPTION

CORRECTION AND COMPUTE ADJUSTED

SHELL MEMBER SIR

For each shell member of your trial room

determine whether an adjustment should be

made for acoustical absorption other than

"medium".

If the room has an acoustic tile ceiling, or 50% or more of the wall area is covered

with draperies, enter a -4-2 in Column (ee).

If there is no carpet on the floor, no acoustic

tile on the ceiling, and no heavy draperies, enter —4 as the absorption correction in Column (ff). These corrections, taken jointly, imply that a room with wall-to-wall carpeting and
acoustical tile ceiling will be approximately

6 dB quieter than an otherwise comparable room with hard ceiling and floors. Now compute the value of the adjusted SIR

which is the algebraic sum of the adjusted

SIR from Column (bb) plus or minus cor- rections for room geometry and absorption. Enter this value in Column (gg) of the SIR

Worksheet. Column (gg) values are the adjusted SIRs for each shell member.

*****

The next step consists of determining a

total room SIR by combining the SIR values

for each of the room's shell members. If there happens to be only one shell member,

the room SIR value is merely the SIR value

for this shell member. If, however, there is more than one shell member, you will have

to combine their SIR values in a manner

similar to the method you used in Chapter 5

to combine noise levels. STEP SIX: COMBINE SHELL MEMBER

SIRs TO OBTAIN ROOM SIR

If there is only one shell member, copy its adjusted SIR value from Column (gg) in Column (ss) ... it is your Room SIR.

If there is more than one shell member, you

must complete a pairwise process of logarithmic addition, as you have done pre- viously when combining noise levels. The

SIR values in Column (gg) indicate the reduction in sound which would occur for otherwise similar rooms, each of which

has only one shell member transmitting

sound energy. When there are several shell members transmitting sound, the room SIR

must be less than the SIR for any one shell member because of the additional energy

transmitted through the other shell members.

Thus, enter in Column (hh) the absolute

difference between SIR 1 (for Shell Member

Number 1) and SIR 2 (for Shell Member

Number 2). Refer to Table 6-1 to obtain

the value of the transmission adjustment

to be entered in Column (ii). Note that when there is little difference

(0 to 1) between the SIR values, the correction factor is largest, amounting to 3 dB.

Correspondingly, if the difference is large

(> 10), the transmission adjustment is zero. Now compute the value of SIR 1,2 for the

two shell members by subtracting the trans- mission adjustment from the smaller of the

two SIR values, SIR 1 or SIR 2. The new

quantity, termed SIR 1,2, is the SIR which

should be entered in Column (jj).

If there is a third shell member, now combine its SIR value, SIR 3, with the value of SIR 1,2 to obtain the value for the effective three shell member combination, termed

SIR 1,2,3, and entered in Column (mm).

Repeat this pairwise combination process

until you have considered all shell members

and have arrived at a Room SIR value, to be

entered in Column (ss) of the SIR Worksheet. Then proceed to the next worksheet,

the Room Noise Worksheet.

*****

The basic procedure is indicated in the flow

chart of Figure 6-6, and requires the tabulation of the exterior sound level(s) for the three types of noise sources listed in Col- umn A of the Room Noise Worksheet: highway noise, railway line operation noise, and

aircraft noise. The sound levels calculated

in Chapter 5 are to be entered in Column B

for any of the transportation noise sources

affecting your building site. These sound

levels are combined to yield the total exterior sound level at the selected trial room. The Room SIR value is then used to obtain

the interior sound levels which would exist due to the external sources. These values

are then compared with the desired noise

criterion level. This procedure is detailed

in the following steps Seven through Ten.

Room Noise Prediction Method

STEP SEVEN: TABULATE EXTERIOR

NOISE LEVELS

Refer to the computations of Chapter 5 to obtain the values of sound level at the

trial room for the three possible types of noise sources. In the event that there is more than one source of highway, railway

or aircraft noise, you will have to sum them

for each type of source as shown in Chapter 5. These values should be entered in Col- umn B.

STEP EIGHT: COMBINE EXTERIOR NOISE

LEVELS

If there are both highway and railway noise

components, determine the absolute differ- ence between the two, and enter this in Column C. Refer to Table 6-1 to obtain the appropriate

level adjustments corresponding to the dif- ference in sound levels. Enter this in Col- umn D. Add this level adjustment to the larger of the two sound levels to obtain the total exterior highway and railway sound level at the trial room. Enter this in Column E. Next, determine the difference between the

total highway-railway sound level and the

aricraft sound level, if any, and enter this

in Column F. Once again, combine the

sound levels by obtaining from Table 6-1

the appropriate level adjustment to be entered in Column G.
Add this level adjustment to the larger of the two sound levels, to obtain the total exterior sound level. Enter this in Column

H.You have now completed the prediction of the exterior sound level due to external transportation system noise sources at the

trial room.

STEP NINE: DETERMINE THE INTERIOR

SOUND LEVEL

Enter in Column I the Room SIR value from

Column (ss) of the SIR Worlcsheet.

Subtract the Room SIR value from the Total Exterior Sound Level to obtain the Interior Sound Level, and enter it in Column J. You have now completed the prediction of the trial room sound level due to external transportation system noise sources.

STEP TEN: COMPARE THE INTERIOR

SOUND LEVEL WITH THE NOISE CRITERIA

LEVEL

In Column K of the Room Noise Worksheet,

enter the interior noise criterion level you

selected in Chapter 3. Compare the value of the interior sound

level which you have predicted with the noise criterion level. If you have selected

Strategy 1 described earlier in this chapter,

and if the interior sound level is less than

or equal to the- noise criterion level, you

have an acceptable design, and the sources

of exterior noise will probably not be

troublesome in your trial room. However,

if the interior sound level is larger than the noise criterion level, it is probable that external noise will be troublesome, and you

will want to modify your design by implementing some of the design alternatives

suggested in the next chapter.

How to Account for Open Windows,

Doors, and Through-the-Wall Ventilators

Open doors and windows offer almost no sound isolation. When doors and windows

can be expected to be open, they should

be listed along with any other shell member components and assigned a SIR of zero. Obviously, this will result in a severe degradation of the shell member SIR if the

door or window has even a moderately large

area. Operable louvres offer little sound

isolation whether open or closed, and should

be assigned a SIR of zero. Through-the-wall

ventilators and unit ventilators with throughthe-wall ducts pose a difficult problem since

they may have sound baffles or insulating

duct linings and may or may not lead directly from the exterior to the room. If acoustic transmission loss data are avail- able from ventilator manufacturers, you may

be able to calculate ventilator SlRs using

the procedures of Appendix B. If not, it's best to be conservative and assign ventila- tors a SIR of zero.

Illustrative Example

Let us now demonstrate these noise cal- culations for a typical room. Consider a ten-story apartment building similar to the one described earlier in this chapter. It is to be located at the building site considered

in the illustrative example of Chapter 5. The building consists of a simple tower

with two windowed facades and two flank- ing walls (See Figure 6-3). The site is ex- posed to all three types of transportation

noise, but aircraft noise was found to be

the major source with a sound level of 69

dB. We will choose an outside corner room

on the top floor as a "worst case" for

initial consideration. Although the possibility of a premium rent for a prime site location

might warrant a lower noise criterion level, we will select an indoor noise criterion level of 40 dB and an outdoor level of 55 dB.

Moreover, since the metric should be appropriate for residential buildings, we will adopt the Ldn metric. Our room design

will therefore be adequate if its interior sound level is less than Ldn == 40 dB. If the predicted interior sound level is higher,

it will be too noisy and we must consider

design alternatives.

The Chapter 5 example yielded the following estimates of the individual exterior Ldn

sound levels. Highway 66 dB

Railway 59 dB

Aircraft 69 dB

Since each of these noise levels is individ- ually in excess of 55 dB, it is clear that any outdoor activity spaces will not be

acceptable for recreational purposes for which speech intelligibility is critical, Furthermore, there is a difficult design

challenge for indoor spaces as well, inas- much as the site is within one mile of a moderate (category 2) airport, and is close

to two highways.

With these factors in mind, let us consider

the sound levels within our typical "worst case" room. We will assume that the dimensions of the trial room are 12 feet wide by

16 feet deep by 8 feet high, and that the room is to be carpeted, but not draped and

not supplied with an acoustical ceiling.
Remember that rooms having suspended

lightweight ceilings can receive exterior

sound through portions of shell members

(walls) extending up through the dead space

of the suspended ceilings. Hence, for such rooms the height to be used for noise cal- culations is not from the floor to the sus- pended ceiling, but from the floor to the

underside of the floor or roof slab above

the ceiling space. For our example, there

is no suspended ceiling space; thus, the room and shell member heights are both

taken as 8 feet. The shell construction of the building consists of 8-inch hollow core concrete block

masonry flanking walls plastered inside. The flanking wall has a 5-foot high by 12-

foot long fixed window glazed with heavy

plate glass opening to the "worst case"

room. The facade walls are of metal frame,

insulated, brick veneer construction with a 4-foot high by 10-foot long fixed window

glazed with heavy plate glass, and a 2-foot high by 8-foot long decorative spandrel

panel. This panel is of 20-gauge steel, in- sulated with glass fiber 2y2-inches thick. The roof consists of a 3-inch steel deck

with rigid fiberglass insulation and built-up

roofing.

Step One

Refer now to the SIR Worksheet (Figure

6-7) and enter the room's flanking wall,

facade wall, and roof as the three shell members of the room. For the flanking wall there are two components, and for the

facade wall, there are three components

which must be listed in sequence of their SIR values, with the highest one first. Refer

to Appendix A to obtain the SIR values. For

the flanking wall, the hollow core block has

the higher SIR number (50) and the glass

windows the lower (28). For the facade wall,

the brick veneer construction has the highest SIR number (51), the glass window sec- ond (28), and the steel panel has the lowest

(26). Enter the SIR values on the worksheet

in Column (f).

• The shell member number is indicated in Column (a) . . . only 2 of the 5 shell member spaces will be needed for the flanking

wall and only 3 of the 5 shell member

spaces for the facade wall. • The shell member name appears in Col- umn (b), and its area appears in Column

(c). • For Column (d), the flanking wall has two

components—A and B; the facade wall has three components—A, B, and C; and,

the roof has only one component—A.

• The shell member's component descriptions are listed in Column (e). • The SIRs are listed in Column (f).

• The room dimensions are listed in Col- umns (g, h, and i) and the room floor area

is entered in Column (j). • The two dimensions of the shell member

components are listed in Columns (k and

I).

Using these data, the component areas are computed and are listed in Column (m).

Note that these Columns (k, I, and m) are

not needed for shell members with only one

component, nor are they needed for Component A of componentized shell members.

Now, since the flanking wall and the facade

wall have several components, we must cal- culate their composite SIRs.

Step Two

Compute the Component B fractional area;

that is, the ratio of component area to the

total wall (shell member) area. For the flank- ing wall, this value is 60 128 = 0.47 which

is entered in Column (n). Now determine

the difference between the two highest SIR

numbers; i.e., the difference between the

SIR for block masonry and the window . . . 50 — 28 = 22. Enter this value in Column

(o). Now refer to Table 6-2 to determine the

composite SIR correction factor corresponding to the fractional area of 0.47 and a SIR

difference of 22. This value is 4 and is entered in Column (p). Now add this value

(4) to the lower SIR number (28) and enter

the result (32) in Column (q). This is the

composite SIR for the flanking wall.

For the facade wall, the Component B fractional area is 40 ^ 96 = 0.42, which is entered in Column (n). Now determine the dif- ference between the two highest SIR numbers; i.e., the difference between the SIR for brick veneer and the window ... 51 — 28 =

23. Enter this value in Column (o). Now

refer to Table 6-2 to determine the composite SIR correction factor corresponding

to the fractional area of 0.42 and a SIR dif- ference of 23. This value is 4 and is entered

in Column (p). Now add this value (4) to the lower SIR number (28) and enter the

result (32) in Column (q). This SIR number

describes the properties of an 8 ft x 12 ft brick wall with a 10 ft by 4 ft glass window.

Now consider the effect of the steel panel

with a fractional area of 0.17 to be entered

in Column (r). The difference between the

SIR value for the brick and window wall

(32) and the steel panel (26) is 6. Enter this value in Column (s). Now from Table 6-2

find the composite SIR correction factor corresponding to the values 0.17 and 6. This

value (4) is entered in Column (t) and is added to the lower SIR value, 26. The sum,

30, is entered in Column (u).
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Component

Description

Arrange

components

of

shell

members

in

order

of

decreasing

SIR

for

each

shell

member.

Order

of

shell

members

is

optional.

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122

Building Proiect A/gar Ht^hi^acjS / £k "2.

Sile point or building room tor which sound pres^iure

levels are being estimated T^Of* F^G^IT /S/(^

Designer ^ SuCj^S

External Noise Source 5 n.

O X

cc ^

Is the Total Indoor Sound Level Due to External Sources Create Than the Noise Criterion Level?

Yes A Noise Problem Exists

The Design is Satisfactory

Figure 6-8. Room Noise Worksheet for Example.

To simplify their visualization in the SIR

Worksheet, the SIRs for the flanking wall

(32) for the facade wall (30) and for the

roof (43) are carried forward to Column

(y) before making further computations.

Now you must perform air leakage adjust- ments.

Step Three

Since the roof is essentially monolithic

without penetrations, and assuming average

workmanship the area of openings can be

taken as equivalent to 3.0 inVlOO ft^ For

the componentized flanking and facade

walls, there will be somewhat more air leak- age, and 4.5 inVlOO ft^ is appropriate as- suming average workmanship. These values

should be entered in Column (aa).

For a 4.5 inVlOO ft' leakage and a SIR of

32, Table 6-3 indicates an adjusted SIR

of 30. Enter this as the adjusted SIR for the

flanking wall in Column (bb). The values for the facade wall and roof are determined in a similar manner. These values are 29 and

36, respectively. Enter these values in Col- umn (bb).

Step Four

In Column (cc), enter the ratios of the shell member areas to the floor area of the room. These values are 128 ^ 192 = 0.67 for the

flanking wall and 96 ^ 192 = 0.5 for the

facade wall.

Now refer to Table 6-4 to obtain the room

geometry correction factors and enter them

in Column (dd). These values are — 1 for the flanking wall, 0 for the facade wall, and — 2 for the roof.

Step Five

Since the room is to be carpeted but not

heavily draped, you do not enter additional

values for the absorption corrections in Columns (ee) and (ff).

Now add the adjusted SIR value from Col- umn (bb) to the room geometry correction

for each shell member and enter in Column

(gg). These SIRs (29, 29, and 34) describe

the sound isolation properties of the flanking wall, facade wall, and roof, respectively.

Now you must make the room geometry

correction.

These shell member SIRs must now be combined to get the room SIR.
step Six

Consider the combination of SIR values for the flanking and facade walls. The differ- ence between these two nun^ibers is 0

(29 — 29 = 0). Enter this value in Column

(hh). Referring to Table 6-1, enter the trans- mission adjustment of 3 in Column (ii). Now

subtract this from the smaller of the two

exterior wall SIR values (29 — 3 = 26), and

enter the value of 26 in Column (jj). This

describes the sound isolation properties of the two walls.

Now combine the two walls with the roof. The difference between the two SIRs is 8

(34 ~ 26 = 8) entered in Column (kk), and

the corresponding transmission adjustment

is 1, entered in Column (II). Subtract this transmission adjustment from the smaller of the two SIRs yielding a Room SIR of 25

entered in Column (mm). For future refer- ence also enter this value in Column (ss).

Now we need to complete the Room Noise

Worksheet, Figure 6-8.

Step Seven

Transfer the exterior noise levels due to the

three types of exterior noise source cited

at the beginning of this example to Column

B of the Room Noise Worksheet.

Now begin the step-wise process of computing the total outdoor noise by determining that the difference between the highway

noise (66 dB) and railway noise (59 dB) is 7 dB, and entering this in Column C. The

corresponding level adjustment is 1 dB, en- tered in Column D. The total of all highway

and railway noise would be obtained by

adding the level adjustment (1 dB) to the higher of the two component levels (66 dB);

here 67 dB is entered in Column E. The

difference between this total and the air- craft noise (69 dB) is 2 dB, entered in Col- umn F; yielding a level adjustment of 2 dB,

entered in Column G. The total of ail out- door noise is thus 71 dB, obtained by adding

the level adjustment (2 dB) to the larger of the two component levels (here that due to aircraft, 69 dB) and entered in Column H.

Now enter the Room SIR as determined in the previous SIR Worksheet in Column I, and subtract the Room SIR (25 dB) from

the total outdoor noise (71 dB) to estimate

the Indoor Sound Level (46 dB), entered in Column J. This is 6dB higher than the noise

criterion level established at the outset of

this example. There is therefore a noise

problem in the "worst case" trial room. Needed design changes to remedy this problem are indicated in the next chapter.

Realize, however, that this "worst case"

trial room has exterior exposure on three

surfaces (facade and flanking walls and

roof). Rooms on the first through ninth

floors, not on the ends, will have only the

facade wall exposed to the exterior sound

energy. For these rooms, the adjusted fa- cade wall SIR will be equivalent to the room

SIR, in this case 29, 4 dB larger than the room SIR for the "worst case" room. So the

level in such rooms will be 42 dB (72 — 29 = 42), which is relatively close to the desired criterion.

Chapter 7

Design Alternatives

If your Chapter 6 calculations predict noise

levels for indoor rooms or outdoor activity areas greater than noise criterion levels, you

will be seeking design alternatives to over- come your noise problems. Possible design

alternatives will be discussed in this chapter.

In addition to design alternatives, it may be

feasible to control noise at its source by

making operational changes to reduce noise

generated by transportation systems. Rerouting truck traffic, the imposition of cur- fews, etc. can substantially reduce noise

levels. If such operational changes can be

worked out through local elected officials or planning authorities, the predictive models of Chapter 5 will be useful in assessing

possible noise level reductions.

There are four types of design approaches

to reduce noise. Two of these types of ap- proaches can prevent noise from becoming

an annoyance for outdoor activities. These

are (1) to locate, orient, or configure the

building to reduce noise at the chosen building site, and (2) to provide additional exterior

barriers such as walls or berms. These two

approaches are also useful in protecting

the building's interior from unwanted sound,

and for this purpose are joined by two other

approaches which are (3) to fortify the building shell, and finally, (4) to vary the interior sound absorption.

One thing is certain . . . anything you do to rearrange the building site or to build upon

it will change its acoustic climate. Probably

the building itself will cause the most drastic changes. Hence, you should deploy the

building creatively to secure the best results. The building can be used to shield

selected outdoor activity areas from noise,

and barriers put up to protect outdoor activity areas from noise or wind can also

shield portions of the building.

Let us discuss in turn the four methods of providing design alternatives: (1) siting, (2)

barriers, (3) building shell, and (4) furnishings.

Siting Alternatives

For siting there are three options . . . site selection . . . building location and orientation, and . . . building configuration. These

options could be pursued independently in design and will be discussed separately,

recognizing however, that in a design

process which truly involves synthesis, the three options would be carried on simultaneously.

Site Selection: The best way to control noise

is to avoid it. This can most effectively be

done if the first design task is that of selecting the building site, because careful selection can steer the proposed building away

from noise problems. Likewise, for some

projects it may be cheaper to abandon a

site already selected and relocate to a

quieter area, than to make extensive revi- sions to an acoustically unacceptable

scheme. For many projects, however, other

considerations than sound may preclude

the selection of a quiet site or relocation

to a quiet site.

Keep in mind that acoustic conditions are

rarely stagnant and you should consult

zoning and planning authorities to deter- mine future plans for the surrounding area. A seemingly suitable site can later be sur- rounded by industrial areas or traffic arteries, or subjected to aircraft overflights

greatly increasing on-site levels. Therefore,

it would be wise to attempt to predict future noise levels at your site to determine the impact of plans for the surrounding area.

In selecting a quiet site, refer to Table

2-2 in Chapter 2 which gives desirable

minima for the distances from transportation system sound sources to a building

or site. Also, look for existing natural and

man-made sound barriers, examples of which are shown in the figures of Section 1
126

1 1 1 1 0 V ''''' 0 e

1 1 1 1

1 1 1

1 1 1 1 7

Figure 7-1 . Use of Various Noise Barriers.

Figure 7-2. Use of Natural Noise Figure 7-3. Selection of Building Sites

Barriers. Relative to Wind Direction.

Figure 7-4. Building Sites near Figure 7-5. Building Sites near

Hilly Traffic Areas. Traffic Junctions.
of Chapter 5 and in Figures 7-1 and 7-2. Sites on rolling terrain separated from rail- ways and highways by heavy, wide stands

of trees are generally quieter than sites lo- cated in hollows or on flat, open ground.

Give preference to sites which are pre- dominantly upwind of noise sources. At

large distances the upwind side is generally

quieter than the downwind side of a noise

source. The wind tends to bend the sound

path upwards, as shown in Figure 7-3,

thereby reducing the sound energy that impinges on an upwind site.

Sites near hills or traffic intersections are generally unfavorable due to the acceleration, deceleration and bral<ing of vehicles,

especially if the traffic includes heavy truck

traffic like that in Figure 7-4. Most of all, congested areas of heavy traffic should be

avoided as shown in Figure 7-5.

Building Location and Orientation: The

thoughtful location and orientation of build- ings on a site can aid in controlling noise.

In order to determine whether or not there

is apt to be a preferred "quiet" location on a site, it is generally necessary to consider several locations, and to perform several detailed calculations as outlined in Chapters 5 and 6. A recommended pro- cedure is to choose a trial building location on the site and to perform the detailed cal- culations . . . then compare the estimated

sound levels propagated from any nearby

transportation noise sources to determine if any one of these sources is predominant at the trial location. If one is, then consider

whether or not the distance to that source can be substantially increased by moving

the building to another location on your

site. For each doubling of the distance away

from a highway you can expect a reduction

of about 4 dB; for each doubling of the distance away from a railway you can

expect a reduction of about 6 dB (there is no simple rule of thumb for aircraft noise).

Buildings can be located in the quiet areas

of a site with windowed facades facing the

quiet areas, and with heavy, windowless

walls facing the sources of sound. In general, the noise level near the facade of a

building facing away from the predominant

source of sound will be 3 dB less than near

a facade facing the source. Acoustical

shielding can be provided by the existing

terrain, natural landscaping, or wooded

areas.

If the building site is relatively close to a major highway or railway, and if the build- ing is to be fairly long, two design concepts

can be employed. One is to orient the

building's major axis perpendicular to the

direction of the highway or railway, and then

to locate the noise-sensitive exterior rooms

at the end of the building farthest from the roadway or track. A second design concept

is to orient the building's axis parallel to the highway or railway and to provide materials having an extremely high SIR on the facade facing the noise source, while

placing noise-sensitive rooms on the fa- cade shielded by the building itself.

it is especially important that buildings not be parallel when located on both sides of an expressway in order to avoid multiple

reflections of sound waves which increase

sound levels. A random or staggered building layout or a cluster of buildings with no

parallel building faces will avoid this problem of multiple reflections of sound waves

between opposite buildings. Slightly curved

buildings can be beneficial when the cur- vature is convex relative to the direction of the greatest noise source. U-shaped build- ings or semi-enclosed courtyards provide areas for multiple reflections and should not be used as outdoor activity areas, because

they tend to be quite reverberant and noisy.

These layouts are shown in Figure 7-6.

Building Configuration: Buildings can be

arranged with noisy and quiet sides as

previously mentioned, if the principal noise source is relatively near. Try to have rooms

with low noise level criteria located on the

quiet side, and rooms with high criteria located on the noisy side. For example, the mechanical rooms and shops of secondary

schools can be gathered together and ar- ranged on the noisy side (particularly since

these rooms also are noise sources) while

libraries, auditoria, and classrooms are deployed on the quiet side.

The facade treatment of the building pre- sents more difficult choices. The total amount of sound penetrating a building is proportional to the area of exterior shell of the building. Hence, a highly compact

building is desired. Ideally the building

would approach a spherical shape so as

to enclose the greatest volume within the smallest shell area. Spheres are impractical shapes for buildings, however, and

a more practical compact shape is the cube. On the other hand, a ground-hugging,

rambling building having a relatively high

shell area to enclosed volume might benefit

from noise attenuation barriers which are too low to benefit a tall building.

There is one such effect that can actually

increase interior sound levels ... it oc-
curs when projections or depressions such

as wing walls and balconies create a number of reverberant enclosures or cavities. These are especially troublesome when

located at a curtain wall or windowed wail,

since the reverberant cavities will tend to raise sound levels at the wall line, and give

rise to increased interior sound levels as a consequence. Caution should be exercised

to ensure that no such reverberant cavities are established. Also, it is wise to prevent

roadway sound from being reflected from

the under side of a balcony toward a wall having windows or doors. The underside of such balconies can sometimes be treated with absorptive materials to partially control such sound reflections.

Barriers

The designer usually has no control of transportation noise at its source, but the designer can provide some form of shielding between the source and the receiver, or

building. This shielding can be in the form

of wails, natural barriers such as earth

berms, rows of intervening buildings, vegetation, etc., as discussed previously in Section 5.1 and reviewed here.

There are economic limits to providing

sound barriers since it is costly to construct

barriers which block all paths along which

sound can travel from a transportation

system noise source to a building and site; but, if any worthwhile barrier attenuation

is to be achieved, the barrier must block

all or most of these paths. In order to block the direct path of sound over the top

of a wall or earth berm, it must be high

enough to block the line-of-sight between

the transportation system noise source, which is estimated to be 8 ft high for heavy

trucks and 15 ft high for diesel-electric loco- motives. Also, noise propagating in a direct

path around the ends of the barrier can se- verely limit its attenuation. The barrier in- cluded angle should be made as large as

possible by extending the ends of a barrier as shown in Figure 5.1-19.

To prevent sound transmission directly

through the sound barrier, it should be constructed of a material whose surface weight

density is greater than 4 lb/ft. ^ Table 7-1 gives approximate surface weight densities

for a variety of materials which may be suit- able for barrier construction. When choosing a material you must also consider the

cost, ease of construction, and durability

with respect to weather conditions. (Refer- ence [1] lists some types of existing and

proposed barriers in the United States and

describes the details of construction and

the materials used. This reference may be

helpful to you in designing a barrier.)

Also important in preventing sound trans- mission directly through a barrier is the

elimination of any holes or openings in the

barrier. The area of any openings in the

barrier must be kept well below 10 percent

of the total barrier area, or better yet, completely eliminated to give a solid continuous barrier with no direct paths to your

building.

The location of a barrier is important in determining its attenuation. The barrier should

be located either close to the source or close to your building so that the angle of

diffraction, hence the attenuation, is maximized. If your proposed building is to be

several stories high, you will probably want

to locate the barrier as close to the source

as possible, since a barrier close to the

building would not shield its upper floors. On the other hand, if your proposed building

is to be only one-story high, the barrier could be located close to the building, thus

reducing the needed length of barrier. There are situations when it is better

to locate the barrier at some intermediate

point. For example, a considerable savings

might be achieved by locating the barrier on a hill or embankment lying between the

Table 7-1. Approximate Surface Weight Densities for Various Materials.

Surface Weight Density,

Material lb/ft'

Timber, Fir (IVa inch thick) 5.0 Timber, Fir (2 inch thick) 6.7 Plywood (iy4 inch thick) 4.2 Cinder Block Hollow Core (6 inch thick) 25.0 Concrete Block Hollow Core (4 inch thick) 23.3 Concrete Block Hollow Core (6 inch thick) 35.0 Brick (4 inch thick) 43.3 Concrete, Dense (4 inch thick) 50.0 Plaster on Metal Lath [Vz inch thick) 4.5
source and your site. Keep In mind that the angle of diffraction (or in other words the path length difference), and the barrier in- cluded angle are crucial in controlling barrier attenuation. You can choose several

alternative barrier locations and then deter- mine the required barrier size needed to provide the desired attenuation for your

building and site. Rely upon your ow/n ingenuity in the use of barriers. An existing earth berm should be

left undisturbed or augmented. Through

careful planning, you can utilize non-critical buildings such as warehouses, garages, and

storage sheds as barriers for occupancies

having more critical noise criteria. Or, you

can provide heavy sound isolation on the

facade of a building facing a noise source, and then use this building as a barrier for other buildings. When extensive right-ofways are available, vegetation shielding

may be an available solution. Vegetation,

however, takes a considerable amount of time to grow, and its noise reduction potential is limited. Moreover, shielding from

deciduous trees is greatly reduced when the

trees lose their leaves.

Obviously cost and aesthetics are important. Costs vary considerably depending

in general upon the barrier height required

and the construction materials. The cheapest barrier is usually the earth berm, which

on some projects can be built from excess

fill at very low cost. The appearance of earth berms is usually good, since land- scaping can virtually hide them from sight, or disguise them as natural hills.

In summary, barriers can be useful in re- ducing the noise levels at your site, but

there are limits to their effectiveness. It is possible to obtain a barrier attenuation of 10 decibels without too much difficulty, but

it may be wise to have the barrier designed

by an acoustical consultant or noise control engineer to ensure that the barrier will achieve this attenuation and solve your

noise problem.

Building Shell

The building shell is the last line of defense against noise, and a line of defense

decidedly under the control of the designer.

As you have seen, the noise isolation pro- vided by the building shell can be seriously

degraded by a single weak link ... a fundamental you must fully grasp if you

are to effectively control sound transmission. The weak link principle states simply

that the sound isolation of any shell member

is reduced substantially by shell member

components having low sound isolation

ratings. This vjas demonstrated by the ex- ample of Chapter 6 where the brick veneer

facade member having a SIR of 51 was re- duced first by the fixed single glazed window

(SIR of 28) to a composite SIR of 32, and

then by a decorative 20-gauge steel panel

(SIR of 26) to a composite facade SIR of 30. Whereas the final composite SIR was not

quite as low as the SIR of the steel panel, it was substantially reduced from 51 to 30. Obviously, the steel panel, constituting only 17 percent of the facade wall's area, was

accountable for much of the sound trans- mitted through the facade wall.

In the same fashion, the cumulative SIR

for the trial room in the example of Chapter

6 was reduced from a SIR number of 34 for the roof to the room SIR value 25, when adjusted for the weaker flanking and facade

wall members.

The sound transmission contributed by any

component to its shell member is, of course,

not only affected by its materials, but also by the area of the component relative to both the area of the shell member, and to the materials and areas of other components. Thus, a small window will not be as weak a link as a large window.

Likewise, the sound transmission contrib- uted by any shell member to a building room depends upon the area and materials of the

shell member in relationship to areas and

materials of the other shell members of the room.

To improve the sound isolation of a shell member, then, it is more important to im- prove the weaker components than the

stronger ones; for example, double glazing a window may prove to be more cost effective than building up the wall that receives

the window. Of course, the higher the SIR,

the less sound transmited through the shell. From this type of information you will gain an understanding of the weak link principle;

open windows and doors can destroy the sound isolation of a wall no matter how

massive.

The overall sound isolation of a shell member is related to its mass, stiffness, continuity of construction, sound absorbency of interior wall coverings, and freedom from

cracks or holes (usually achieved by high

quality construction). All of these shell member characteristics resist the penetration of sound through the member and

resist member vibration in response to in- cident sound. The greater the mass, the less a shell member will be excited into vibration

by incident souds, assuming the shell member's stiffness is held constant.
Holes and cracks are the worst offenders in admitting sound. A hole occupying only

0.01 percent of a total shell member's area,

limits its sound isolation to 40 dB. Thus, a

highly sound-resistant shell member, such

as one of a hundred square feet with a SIR of 60, would be reduced to a SIR of 40 by a hole ^V2 square inches. A shell member of the same size but having a SIR of 40 would be dropped by the same

size hole to a SIR of 37. For the former

shell member, at least 90 percent of the

sound energy entering the building would

pass through the hole; for the latter shell member, 50 percent of the energy would

be transmitted via the hole. Clearly, it is an

acoustic error to specify heavy construction if the heavy construction has penetrations which are not well-sealed.

Similarly, open windows can destroy the sound isolation of a building. The recent

interest in energy conservation has caused

a reexamination of the trend toward year- round air conditioning with sealed windows

(especially for office buildings). Some experts believe that a return to buildings with

operable sash and natural ventilation can

save energy used for cooling in spring and

fall in most parts of the country. Other

experts argue that any such energy savings

are lost through air infiltration around operable sash in winter and summer, which are peak periods for heat loss and heat gain.

In any event, sealed, fixed windows provide

better noise attenuation than comparable

operable windows. Even a reasonably tightfitting operable window is apt to have a crack width of 0.03 inches [2]. If the window is only 2-feet wide by 3-feet high, it will have ten feet of crack equivalent in area

to a hole of 3.6 square inches. Some fifty percent of the sound impinging upon the

window may enter the building through the

crack. Weather-stripping can improve the

window's acoustical and thermal performance, and double glazing is superior to single glazing. In general, those principles

which provide desirable thermal insulation

will also provide sound isolation.

How much sound isolation does a "typical"

building provide? The Environmental Protection Agency (EPA) has published this type of information for dwellings subjected

to aircraft noise [3]. The EPA categorized

houses as "warm climate" and "cold cli- mate," and reported findings for openwindow and closed-window conditions for both categories of house. The "openwindow condition" corresponded to an opening of 2 square feet, and a room absorption typical of bedrooms and living rooms. Based upon this "open window condition," and aiming at conservative values

of the sound levels inside dwellings, the

EPA published the values of Table 7-2.

The sound level reductions provided by the

exterior shells of buildings in a given community have a wide range due to differ- ences in the use of materials, building

techniques, and individual building plans.

Nevertheless, for general planning pur- poses, the Table 7-2 reductions in sound

level from outside to inside a house can

be used. However, their use in connection

with this guide is limited since they reflect average sound level reductions, and are, therefore, not completely compatible with

this design guide's room-by-room shell iso- lation rating method of calculation.

To fortify the Shell against sound, one

should—(1) use heavy, monolithic materials (concrete, brick, and block are more

sound resistant than wood or steel frame

construction or curtain walls),—(2) reduce

the area of cracks and holes penetrating

the shell by careful architectural detailing

and through quality construction,—(3) design for sealed windows with year-round

air conditioning where noise conditions

are serious, —(4) reduce the size of windows and provide them with double glazing keeping the size of operable sash,

hence crack length, to a minimum,—(5) avoid weak links by ensuring that SIRs for

shell member components are comparable

and as large as possible. Naturally, the

designer must use judgment in applying

these sound control guidelines to particular

building projects, which will surely have

many other concerns competing against

acoustic considerations.

Table 7-2. Sound Level Reduction Due to Houses* in Warm and

Cold Climates, with Windows Open and Closed.

Windows Windows

Open Closed

Warm climate 12 dB 24 dB

Cold climate 17 dB 27 dB

Approx. national average 15 dB 25 dB

* Attenuation of outdoor noise by exterior shell of the house.
Furnishings

Do not overlook the possibilities of acoustically absorptive materials for floor, wail,

and ceiling coverings and for interior fur- nishings. The calculations of Chapter 6

indicate a nnaxinrium sound level difference

of approximately 6 dB between a bare room

with a hard ceiling and no carpet, and a room that has an acoustic ceiling and is fully carpeted. Moderately absorptive decorations and furnishings in an office or class- room would reduce noise levels by, say, 2 dB below that for a bare, reflective room. A difference of a few decibels, while modest,

may have a favorable psychological impact

upon building occupants, especially when

made aware by the presence of these ap- pointments, that attempts have been made

to reduce noise levels.

It may be possible to further reduce noise

levels, through the use of acoustically absorptive interior partitions. Also, interior furnishings such as chairs, sofas, etc., which

are relatively heavily padded and covered

with soft fabrics can achieve another noise

level reduction amounting to 1 or 2 dB.

Illustrative Example

To illustrate some of these design alternatives, let us once again consider the ex- ample cited in Chapters 5 and 6. Recall that

for this example, the site is located near two major highways, a railway, and an air- port; and the '"worst case" room selected

for calculations was a corner, top-floor room

in the ten-story apartment building.

Because the noise from the airport and

highway is dominant, it is impossible to make effective use of any of the suggested

siting alternatives short of a completely new

site selection. If one could disregard the

air traffic as a noise source, it would be

beneficial to re-position the building a little closer to the railway line, since its noise

component is smaller than that of the highway. But since the building is subjected principally to aircraft noise, it would

not be very helpful to make use of building

location and orientation options.

Building configuration will not be an important factor either, since nearly all of the noise sources are at a considerable dis- tance and arranged around the site so that the building will have no quiet side.

Barriers will not be feasible as design

alternatives because the dominant source

of noise is aircraft.

Thus, the building shell offers the principal

opportunities for design alternatives. In re- view of the SIR worksheet (Figure 6-7), you

can quickly realize that there are three

"weak links" in the building design for the "worst case" room—the window in the flank- ing wall, and the window and decorative

steel panel in the facade wall. To increase

the total room SIR, these "weak links" must

be strengthened by reducing the areas of the "weak link" components or replacing

them with components having higher SIRs.

Or, the quality of workmanship could be

improved to reduce air leakage.

If (a) the steel panel is replaced with an

identically dimensioned stucco panel (SIR

of 41), (b) the single glass fixed windows

are replaced with double glazed fixed windows (two panes of inch glass plus a 2V'i inch air space—SIR of 37) in both the flank- ing and facade walls, and (c) average workmanship is assumed, the total room SIR can be increased to 29, an increase of 4. If in addition to these modifications the workmanship is improved from average to good, the

total room SIR can be increased to 30. Moreover by adding an acoustic tile ceiling, the room SIR would be increased by 2 to a value of 32. The predicted total sound

level in the "worst case" room would then

be 71 - 32 = 39 dB, which is below the noise criterion level of 40 dB. As another

alternative, eliminating the window in the

flanking wall would increase the total room

SIR to 32 without using acoustic tile ceiling.

Noise predictions for this last alternative

no flanking wall window, stucco panel and

double glazed window in the facade wail,

and good workmanship—are illustrated in the SIR Worksheet of Figure 7-7 and the Room Noise Worksheet of Figure 7-8.
132

I

0

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issj 9JBnbs UI eajv luauodiuoo E

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199] Uj I ON U0ISU3UJIQ dOBJ lUdUOduJOQ

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Componeni

Description

Arrange

componenis

of

shell

members

in

order

of

decreasing

SIR

for

each

shell

member

Order

of

shell

members

is

optional

0

if

"1

to

1

|s

f

1

1

N

Is

S)ueuodujoo jaquja^ iRi^S < OQ 0 a < m < 0 0 < at 0 0 < m 0 0

leat ejBnbs u| b9jv jaquja^ [|9qs J?/ Zbi

9UJ6N J3qujaK< IISMS

jaqiunN jaqujg^v iiauS Cvj CO in

Figure 7-7. SIR Worksheet for Revised Example.
133

Building Proiect level* are being eslimattil _7jO»^_F/cor_Jf^rJ^

7 JuJoj 77

External Noise Source

O iT H o

f, <

3 "h

Is Ihe Total Indoor Sound Level Due to External Sources Greater Than the Noise Criterion Level?

Yes A Noise Problem Exists

No ^ The Design is Satisfactory

Figure 7-8. Room Noise Worksheet for

Recall, further, that the room chosen was

a "worst case" corner room with two walls

and a roof exposed to sound pressures. Other rooms having only one facade wall exposed would have noise levels reduced

by 3 dB relative to the noise levels for comparable rooms with roof and flanking wall exposure. The sound level within such a

"typical" non-corner, exterior room using a stucco panel would be 36 dB, which is well

Revised Example.

below the selected noise criterion for this apartment building. An additional increment

of 2 dB would be achieved if an acoustic

tile ceiling were employed, in this case the sound level would be 34 dB. Table 7-3

summarizes these alternative designs and

the resulting interior sound levels in the "worst case" corner room and in other non- corner rooms.
134 Table 7-3. Summary of room SIR and interior sound level calculations for "worst cases"

top-floor corner room and comparable interior rooms for the original and two alternative

building designs.

Design

Description

"Worst Case" Top-floor Corner Room

Flanking Wall—8" X 8" X 16" Hollow Core Concrete Block

12' X 5' Heavy Glass Fixed Window

Facade Wall—Metal Frame Frame Insulated Brick Veneer

10' X 4' Heavy Glass Fixed Window

8' X 2' Steel Panel Roof—Insulated 3" Steel Deck

Workmanstiip—Average

Interior Furnishings—Carpet, No Acoustic Tile Ceilings or Heavy

Drapes

Non-corner Room

Oirginal Conftguratiott

Alternative No. 1

Flanking Wall —8" X 8" X 16" Hollow Core Concrete Block

12' X 5' Heavy Double Glazed Fixed Window

Facade Wall —Metal Frame Insulated Brick Veneer

10' X 4' Heavy Double Glazed Fixed Window

8' X 2' Stucco Panel Roof— Insulated 3" Steel Deck Workmanship—Good

Interior Furnishings—Carpet and Acoustic Tile Celling, No Heavy

Drapes

Alternative No. 2

Flanking Wall —8" X 8" X 16" Hollow Core Concrete Block No window

Facade Wall —Metal Frame Insulated Brick Veneer

10' X 4' Heavy Double Glazed Fixed Window

8' X 2' Stucco Panel Roof—Insulated 3" Steel Deck Workmanship—Good

Interior Furnishings—Carpet, No Acoustic Tile Ceiling or Heavy

Drapes

References

Chapter 7 Design Alternatives

[1] Anderson, G. S., Miller, L. N., and Shadley, J. R., "Fundamentals and abatement

of highway traffic noise: Volume Two

noise barriers design and example

abatement measures" (Federal Highway

Administration, Washington, D.C., 1973).

Available from National Technical Infor- mation Service, Springfield, Virginia,

Accession No. PB 222-703.

[2] ASHRAE Handbook of Fundamentals,

Infiltration and Natural Ventilation,

Chapter 19 (American Society of Heating, Refrigerating, and Air Conditioning

Engineers, New York, 1972).

[3] Anon. Information on levels of environmental noise requisite to protect public

health and welfare with an adequate

margin of safety. EPA Report No. 550/9-

74-004 (U.S. Environmental Protection

Agency, Washington, D.C., March 1974).
135 Appendix A

SIR Values for Building Shell

Members and Components

Introduction

The SIR values for walls, roofs, windows,

and doors presented in this appendix have

been obtained, together with descriptions of the construction details, from published

literature [1-13] on the sound isolation, or transmission loss properties of building

shell members and their components.

Effort has been expended to include in this

list only those building constructions which

have adequate descriptions of construction

details, and those which appear to be technically consistent and accurate. Unfortunately, the literature on this topic is not

well organized; and the data should be more

thoroughly and accurately compiled in the

future. The data of references [1], [3] and

[4] are perhaps the most comprehensive.

Should you require the SIR value for some

building shell member or component not

listed in Appendix A, and if you have the necessary transmission loss data, you can

derive the SIR value using the procedure

outlined in Appendix B ("Determination of the Shell Isolation Rating"). Alternatively,

you can estimate a SIR value by comparing

the shell member or component you have in mind with ones of similar construction listed herein.

For some constructions, more details can

be obtained from references [1-13], al- though pertinent details have been included

herein insofar as possible.

In some cases, manufacturer's names or designations are indicated in the "Remarks"

portion of the listing. This information is based upon available published literature,

and may not represent currently available

products or product performance. The

reader is encouraged to seek out specifications pertaining to currently available

products, to determine the relevant SIR

values, and to up-date and supplement these

listings as appropriate. The inclusion of these manufacturers names and proprietary

designations, or the omission of others, does

not constitute any endorsement or criticism

of product performance on the part of the National Bureau of Standards. Rather, the data are given to provide a limited sample of available building components for the users of this design guide.
136 Walls

Description

Concrete Walls

4 in. thick dense poured concrete, or solid blocl< 4 in. dense poured concrete

6 in. tiiicl< dense poured concrete, or solid blocl< 8 in. thick dense poured concrete, or solid block

8 in. dense poured concrete

12 in. thick dense poured concrete, or solid block

16 in. thick dense poured concrete, or solid block

Brick, Block, and Tile Walls

4 in. lightweight concrete block

4 in. lightweight concrete block

6 in. thick hollow concrete block, 6 in. x 8 in. x 16 In. 6 in. thick hollow concrete block, 6 in. x 8 in. x 16 in. 6 in. thick hollow concrete block, 6 in. x 8 in. x 16 in., V2 in. gypsum wallboard fastened on furring strips

inside

8 in. thick hollow concrete block, 8 in. x 8 in. x 16 in. 8 in. thick hollow concrete block, 8 in. x 8 in. x 16 in. 8 in. thick hollow concrete block, 8 in. x 8 in. x 16 in., gypsum wallboard fastened on furring strips inside

12 in. thick solid concrete block, 12 in. x 8 in. x 15

in., % in. gypsum wallboard fastened on furring strips

inside

12 in. thick combination wall, 8 in. x 8 In. x 12 in., and 8 in. X 4 in. x 16 in., hollow concrete blocks

slotted lightweight concrete block, 8 in. x 8 in. x 16

in.

8 in. dense concrete block

8 in. dense concrete block

12 in. thick brick wall perforated glazed tile, 3% in. x 7% in. x 15% in., fiberglass core

acoustic ceramic glazed structural facing tile, 3%

in. X 5Vi6 in. x 1 1 % in. 3V2 in. thick (approx.), 18 ga. steel panels filled with 6-8 Ib/cu ft insulation

Brick Veneered Frame Walls

face brick veneer, Vz in. air space with metal ties, % in. insulation board sheathing, 2 in. x 4 in. wood

studs, 16 in. o.c, resilient channel, Vi in. gypsum

wallboard screwed to channel

face brick veneer, Vz in. air space with metal ties, % in. insulation board sheathing, 2 in. x 4 in. wood

studs, 16 in. o.c, fiberglass building insulation, V2 in. gypsum wallboard screwed to studs

Weight Remarks

Ibs/ft2

Ref. SIR

50

50

73

95

100

145

190

24

24

2134

27

30

30

43

124

79

(estimate)

(estimate)

(estimate)

(estimate)

(estimate)

unpainted

sealed with 2 coats of paint

1 wall painted

exterior wall painted

painted both sides

exterior wall painted

— 2 coats of bondex ce- ment base paint on one

side, Soundblox Type

"A" The Proudfoot Co.,

Inc. 50 sealed with 2 coats of paint

50 unpainted

121— Arketex Ceramic Corp. — SCR Acoustile

Stark Ceramics, Inc. — joints and edges sealed

(estimate)

[5]

[2]

[5]

[5]

[2]

[5]

[5]

[2]

[2]

[13]

[4]

[13]

[13]

[13]

[13]

[13]

[2]

[2]

[4]

[3]

[3]

[5]

4147

43

46

52

49

51

27

43

4145

48

43

43

46

54

[4] 49

[3] 44

52

52

54

44

48

38

[1] 48

[1] 51
137 face brick veneer, Vz in. air space with metal ties, %

in. insulation board shieathing, 2 in. x 4 in. wood

studs, 16 in. o.c, fiberglass building insulation, resil- ient channel, Vz in. gypsum wallboard screwed to channel

Stuccoed Frame Walls

% in. stucco, no. 15 felt building paper and 1 in. wire mesh, 2 in. x 4 in. wood studs, 16 in. o.c, Ve in. gypsum wallboard fastened to studs

% in. stucco, no. 15 felt building paper and 1 in. wire mesh, 2 in. x 4 in. staggered wood studs, 16 in. o.c, % in. gypsum wallboard fastened to studs

% in. stucco, no. 15 felt building paper and 1 in. wire mesh, 2 in. x 4 in. wood studs, 16 in. o.c,

fiberglass building insulation, in. gypsum wall- board screwed to stud

% in. stucco, no. 15 felt building paper and 1 in. wire mesh, 2 in. x 4 in. wood studs, 16 in. o. c,

resilient channel, Vi in. gypsum wallboard screwed

to channel

% in. stucco, no. 15 felt building paper and 1 in. wire mesh, 2 in. x 4 in. wood studs, 16 in. o. c, fiber- glass building insulation, resilient channel, Vi in. gypsum wallboard screwed to channel

Frame Walls With Wood Siding

% in. X 10 in. redwood siding, Vi in. insulation board

sheathing, 2 in. x 4 in. wood studs, 16 in. o. c, fiber- glass building insulation, Vi in. gypsum wallboard

screwed to studs

% in. X 10 in. redwood siding, Vi in. insulation board

sheathing, 2 in. x 4 in. wood studs, 16 in. o. c, V2 in. gypsum wallboard screwed to studs

% in. x 10 in. redwood siding, Va in. insulation board

sheathing, 2 in. x 4 in. wood studs, 16 in. o. c,

resilient channel, Vi in. gypsum wallboard screwed

to channel

% in. X 10 In. redwood siding, Vi in. insulation board

sheathing, 2 in. x 4 in. wood studs, 16 in. 0. c, fiber- glass building insulation, resilient channel, Vz in. gypsum wallboard screwed to channel

Metal Walls, Curtainwalls

fluted 18 ga. sheet metal

21/2 in. thick panel, 20 ga. galvanized steel channel

wall, perforated 18 ga. galvanized steel B-iiner, fiber- glass sealed in polyethylene bags

2V2 in. thick panel, 20 ga. galvanized steel channel

wall, perforated 18 ga. galvanized steel C-liner, fiber- glass sealed in polyethylene bags

common curtainwall spandrel panel, 16 ga. sheet

metal exterior, insulation and % in. gypsum wall- board interior

21/4 in. thick panel, welded steel ribs, vertical 1 ga.

steel stiffeners, rockwool insulation between 20 ga.

steel sheets

2V4 in. thick panel stiffeners, rockwool insulation between 20 ga. steel sheets

[1] 53

[2]

[2]

[1]

[1]

[1]

34

41

43

43

52

[1]

[1]

[1]

11]

33

34

37

40

4.4 prefabricated building [2] 25

component

4.5 Elwin G. Smith Div. [3] 26 — Elwin G. Smith Div.

7.8

5.13 Corporate MS-454

Virginia Metal Products

Div. 4.46 f^onoline wall partition

Virginia Metal Products

Div.

[3]

[2]

[3]

[3]

29

38

34

37
138 2y2 in. thick panel, 20 ga. galvanized steel channel

wall, perforated 18 ga. galvanized steel C-liner, fiber- glass sealed in polyethylene bags

20 ga. galvanized steel channel wall, perforated 18

ga. galvanized steel C-liner, fiberglass, % in. gypsum

waliboard *

Shadowal!

Elwin G. Smith Div.

Shadowall

Elwin G. Smith Div.

[3] 39

[3] 41

* Some of the metal partitions listed here are not principally intended for use as exterior partitions. However, the description and inclusion of SIR values are included to provide a basis for estimation of the shell isolation properties of comparable metal exterior wall systems.

Roofs

Description

Wood Roofs

built-up, insulated roof over 2 in. tongue and groove

wood planking

shingle roof with attic, V2 in. gypsum waliboard ceiling, framed independently of roof

built-up, insulated roof over 2 in. tongue and groove

wood planking, V2 in. gypsum waliboard with cavity

insulation

Steel Roofs

built-up insulated roof over 18 ga. metal decking

IV'2 in. thick roof, 22 ga. steel roof decking

11/2 in. thick roof, 20 ga. steel roof decking

3 in. thick roof, 20 ga. steel roof decking

IV2 in. thick roof, 18 ga. steel roof decking

AVz in. thick roof, 20 ga. steel roof decking

15/8 in. thick roof, 18-18 ga. steel roof decking

4V2 in. thick roof, 20-18 ga. steel roof decking

1% in. thick roof, 18-18 ga. steel roof decking

4V2 in. thick roof, 20 ga. steel roof decking

6 in. thick roof, 18 ga. steel roof decking

4V2 in. thick roof, 16 ga. steel roof decking

7V2 in. thick roof, 18 ga. steel roof decking

Weight Remarks

Ibs/ft2

13

10

15

10

exposed planking and

beams

attic ventilation

Ref. SIR

[2] 37

[2] 40

[2] 42

[2] 36

Type S Acoustideck [3] 42

Inland Ryerson Co. Type S and B [3] 43

Acoustideck

Inland Ryerson Co.

Type 3 in. H & N [3] 43

Acoustideck

Inland Ryerson Co.

Type S and B [3] 44

Acoustideck

Inland Ryerson Co. Type 41/2 in. H [3] 44

Acoustideck

Inland Ryerson Co. Type 1% in. NF [3] 46

Inland Ryerson Co. Type 41/2 in. H [3] 46

Acoustideck

Inland Ryerson Co.

Type 15/8 in. NF [3] 47

Inland Ryerson Co. Type 41/2 in. HF [3] 47

Acoustideck Inland Ryerson Co. Type 6 in. H Acoustideck [3] 47

Inland Ryerson Co. Type H Acoustideck [3] 48

Inland Ryerson Co.

Type 71/2 in. N [3] 48

Acoustideck

Inland Ryerson Co.
139 1% in. thick roof, 16-18 ga. steel roof decking — Type 1 % in. NF [3] 49

Inland Ryerson Co. 3 in. thick roof, 18-18 ga. steel roof decking — Type 3 in. NF [3] 49

Acoustideck

Inland Ryerson Co.

6 in. thick roof, 16 ga. steel roof decking — Type 6 in. H Acoustideck [3] 49

inland Ryerson Co.

41/2 in. thick roof, 18-18 ga. steel roof decking — Type 4V2 in. HF [3] 49

Acoustideck

Inland Ryerson Co.

4V'2 in. thick roof, 16-18 ga. steel roof decking — Type 41/2 in. HF [3] 50

Acoustideck

Inland Ryerson Co. 6 in. thick roof, 16-16 ga. steel roof decking Type 6 in. HF 16-16 ga. [3] 51 Acoustideck

Inland Ryerson Co.

built-up, insulated roof over 4 in. concrete slab 50 [2] 49

Windows

Description Weight Remarks Ref. SIR

lbs/ft^

Fixed Windows, Single Glazed

single strength glass (^2 in.) — four lights [12] 22

single strength glass (%2 in.) 1.3 fixed window, divided [1] 25

linhto "1R r> o n Qo 3/, ^ i

n

liyrilS, lO pdllcS, 716 in. glass, % in. airspace

double strength glass 1.63 single light [11 26

2 mm glass — wood frame [12] 26

3 mm glass single light [12] 26

4 mm glass plastic frame, 3 lights [12] 26

Va in. glass wood frame, 3 lights [12] 26

4 mm glass wood frame [121 28

V4 in. glass 3.2 sealed

Vie in. glass \ktr\r\r\ WUUU dllU GnH cfool olc;t:;l fromo lidlllc PR

9.5 mm glass rt^otol ffOmQ ^loco meidi Trdiiic, yidss stji in ferromastic putty

5.5 mm glass two lights [12] 29

% in. glass wood and steel frame [12] 29

Vz in. glass ri2i I ' '•J 30

10 mm glass O 1

laminated glass [Me in. glass, 0.045 in. interlayer. [12] 31 %6 in. glass]

laminated glass 3 plies, 10 mm thick [12] 31 glass with 2 damping

Idyci o

9.5 mm glass glass mounted in neo- TO prene gasket

15.9 mm glass [12] 32

laminated glass double Vs in. sheets [1] 32

laminated to inner

clear damping layer,

sealed in heavy wood

frame
140 1/i /4 inIII. jioniiQtip dUvJUoLIU nlacQ ^Icioo T 2 OC^dlCLI 00

% in. glass wood frame [12J

0000

laminated glass [Va in. glass, 0.045 in. intGrlayer, [12] 0000

Va in. glass]

15 mm glass [12] 34

% in. glass f12] 34

7/q /OlII.UIClOO in nlj^QQ OH

1 in. glass wood frame [12] OAo4

laminated glass [Vs in. glass, 0.045 in. interlayer, [12] 35

% in. glass]

Vz in. acoustic glass 6.4 sealed [2] 36

laminated glass — 4 plies, Ve in. thick

glass with 3 interlayers

of 0.045 in.

[12] 36

laminated glass [% in. glass, 0.045 in. interlayer. — [12] 37

% in. glass]

V2 in. acoustic safety glass — Soundtropane 40

Dearborn Glass Co.

[10] 37

V2 in. laminated glass — Series 324

Starline, Inc.

[3] 38

laminated glass 3 plies, Va in. thick

glass with 2 inter- layers of 0.045 in.

[12] 38

laminated glass — 6 plies, Ve in. thick glass with 5 inter- layers of 0.045 in.

[12] 39

Fixed Windows Double Glazed

3 mm glass, 4.8 mm airspace, 3 mm glass meiai irame, weainerstripped, 6 lights

0c.

2.9 mm glass, 4.9 mm airspace, 2.9 mm glass sealed, 2 lights [12] 22

3 mm glass, 12 mm airspace, 3 mm glass [12] 25

6 mm glass, 12 mm airspace, 6 mm glass [12] 27

6.2 mm glass, 11 mm airspace, 6.2 mm glass — sealed unit [12] 27

Va in. glass, V2 in. airspace, Va in. glass wood frame, 3 lights ri 01

3 mm glass, 51 mm airspace, 3 mm glass separate wood frames,

20 lights

[I'^J

3 mm glass, 32 mm airspace, 3 mm glass wood frame [12] 30

4.9 mm glass, 18 mm airspace, 7.6 mm glass sealed unit [12] 30

6 mm glass, 12 mm airspace, 8 mm glass [12] 30

12 mm glass, 12 mm airspace, 12 mm glass [12] 30

Vb in. plate glass, 2V4 in. airspace, Va in. plate glass [3] 32

6.1 mm glass, 21.5 mm airspace, 9.4 mm glass sealed unit [12] 32

6 mm glass, 13.3 mm airspace, 8 mm glass sealed unit [12] 32

7.7 mm glass, 13.5 mm airspace, 9.5 mm glass sealed unit [12] 32

8 mm glass, 12 mm airspace, 10 mm glass [12] 31

6.1 mm glass, 27 mm airspace, 9.1 mm glass sealed unit [12] 33

Va in. glass, 1 in. airspace, Va in. glass figured glass, 3 lights [12] 33

Va in. glass, 1 in. airspace, % in. glass figured glass, 3 lights [12] 33

3 mm glass, 75 mm airspace, 3 mm glass — [12] 34

3 mm glass, 10 cm airspace, 3 mm glass [9] 34

4 mm inner glass, 56 mm airspace, 10 mm outer glass — wood plastic composite window, 1 lip sealed

[8] 34

% in. glass, 1 in. airspace, % in. glass figured glass, 3 lights [12] 34
141 8 mm glass, 13.3 mm airspace, 10 mm glass Q p a 1 p 1 1 n i t n 91 4 mm glass, 8.5 cm airspace, 4 mm glass i^j 35

V4 in. glass, 2 in. airspace, Va in. glass separate wood frames,

20 lights

[121 35

6 mm glass, 10 cm airspace, 6 mm glass — [9] 36

%6 in. glass, 2 in. airspace, Va in. glass — [12] 36

% in. glass, 2 in. airspace, % in. glass — figured glass, 3 lights [12] 36

3 mm glass, 10 cm airspace, 6 mm glass — [9] 37

4 mm glass, 10 cm airspace, 4 mm glass [9] 37

V4 in. glass, 2 in. airspace, Vz in. glass — [12] 37

/4 m. piaie giass, ii'M m. airspace, 74 m. plate glass aluminum frame,

DeVac, Inc.

[3] 37

3 mm glass, 10 cm airspace, 3 mm glass 10 cm X 10 cm deep

absorbing material in

[9] 38

3w mm•II Qla"?S ^uoo, 10I cmWill airtinarp CI 11 o l-f CI , R\J mmIMIII nlacc MlCtoo frame channelIQI

19J 4 mm glass, 10 cm airspace, 4 mm glass — 10 cm X 2.5 cm deep

absorbing material in frame channel

[9] 38

4 mm glass, 10 cm airspace, 4 mm glass — 10 cm X 5 cm deep

absorbing material in frame channel

[9] 38

/15 III. yidbo, /2 111. airspace, /4 in. glass 0./ neoprene gasketed

aluminum frame

[2] 38

V4 in. plate glass, 2V2 in. airspace, Vie in. plate glass [31 38

vA/f inIII. nlfl^^ ^icioo, PinIII. fli cuio^ctoc, rQnpr*P 3/j /o inIII. niacc yicioo OO

4 mm glass, 10 cm airspace, 4 mm glass 10 cm X 10 cm deep

absorbing material in irame cnannei

[9] 39

6 mm glass, 10 cm airspace, 6 mm glass 10 cm X 2.5 cm deep

absorbing material in frame channel

[9] 39

6 mm glass, 10 cm airspace, 6 mm glass 10 cm X 5 cm deep

absorbing material in frame channel

[9] 39

6.25 mm glass, 70 mm airspace, 19 mm glass [12] 39

%6 in. glass, 2 in. airspace, % in. glass [12] 40

%2 in. glass, 2V2 in. airspace, Va in. glass [2] 40

/4 in. pidlc yidSS, ^ /4 in. airopdOc, /4 111. pidlo yidoo An

6 mm glass, 10 cm airspace, 6 mm glass 10 cm X 10 cm deep

absorbing material in irdme cndnnei

[9] 41

3 mm glass, 10 cm airspace, 6 mm glass 10 cm X 10 cm deep

absorbing material in frame channel

[9] 42

3 mm glass, 10 cm airspace, 8 mm glass 10 cm X 10 cm deep

absorbing material in frame channel

[9] 42

%6 in. glass, 4 in. airspace, Va in. glass aluminum frame,

O 1 Id 1 1 iCO) IIIU.

[11] 45

%6 in. plate glass, 43/4 in. airspace, Va in. plate glass [3] 45

%2 in. glass, 3% in. airspace, Va in. glass 6.1 neoprene gasketed

aluminum frame

[2] 45

%2 in. glass, 33/4 in. airspace, Va in. glass [121 45
142 %2 in. plate glass, 3% in. airspace, ¥4 in. plate glass

Va in. plate glass, 4 in. airspace. Vie in. plate glass

Single Hung Windows, Single and Double Glazed

double glazed (%6 in.)

V4 In. plate glass

Double Hung Windows, Single Glazed

single strength glass (%2 in.) single strength glass (%2 in.) single strength glass (%2 in.)

Double Hung Windows, Double Glazed

%2 in. single strength glass, Vie in. airspace,

%2 in. single strength glass, % in. airspace

%2 in. single strength glass, in. airspace,

%2 in. single strength glass with storm sash

3/8 in. glass with ^2 in. single strength glass storm sash

Casement Windows, Single Glazed

single strength glass (%2 in.) double strength glass (Vb in.) double strength glass (Va in.) double strength glass (Ve in.)

Horizontal Sliding Windows

single strength glass (%2 in.)

single strength glass {Vsi in.)

Miller BIdg. Supply [3] 45

Co.

[3] 48

aluminum frame, [1] 26

locked

[3] 28 — wood frame [2] 20

1.3 single light [1] 22

1.3 single light, [1] 24

locked — wood frame [7] 20

2.6 single light, locked [1] 25

wood frame [7] 28 — single lights, locked [1] 29

— steel frame [7] 19

1.63 aluminum frame, locked [1] 20

1.63 operable locked [1] 28

1.63 single light [1] 29

aluminum frame [2] 16 — aluminum frame, locked [1] 24

Va in. glass

Pivoted Windows, Single and Double Glazed

Va in. plate glass

double glazed, ^/le in. plate glass, 2 in. airspace,

V4 in. plate glass

Miscellaneous Windows, Various Glazing

3 mm glass

V4 in. glass

2.9 mm glass

double glazed, Va in. plate glass, Vz in. airspace,

Va in. plate glass

aluminum frame [7] 24

vertical pivoted [3] 29

window

pivoted window with [3] 38

thermal and sun

control Kawneer Co., Inc.

operable window, [12] 21 aluminum frame,

20 lights

operable window, [12] 22

aluminum frame,

20 lights

operable window, [12] 23

wood frame, glass

set in mastic, 2 lights

Venetian blind window [3] 31 Ameico Window Corp.
"143 double glazed, Va in. plate glass, 1% in. airspace, 1/4 in. plate glass

•A in. glass

single strength glass (3/32 in.) with single strength

glass (%2 in.) storm sash with 21/4 in. separation

between upper pane and 3% in. separation between

lower pane and storm sash

single strength glass (3/32 in.) with double strength

glass (%2 in.) storm sash with 3% in. separation

between storm sash and glass

glass block window, 3% in. thick

Construction

Glass Doors

safety glass, sliding door

wood, French door, singlestrength glass

Wood Hollow Core Doors

Weatherstripping

brass

yes

yes

bronze

brass

Wood Solid Core Doors

extruded

plastic

brass

extruded

plastic

Miscellaneous Wood Doors

paneled

solid panel

hardwood, acoustical door

acoustical door

flush

bronze

Doors

Weight ThickIbs/fi' ness

2.6 2.85

2.5

1.4

2.5

1.4 1.25

5.1

4.5

3.9

5.0

2.9 4

4

8.1

Ms in.

13/4 in.

13/4 in.

13/4 in.

13/4 In.

13/4 in.

13/4 in.

13/4 in.

13/4 in.

13/4 in.

3.9 13/4 in. — 13/4 in.

13/4 In.

21/8 in.

17/8 in.

13/4 in.

Venetian blind window

Alpara Aluminum Prod.

Inc. jalousie window, 41/2

in. wide louvers with

Vz in. overlap, cranked

tight

locked

fixed window, divided

lights, 16 panes, storm sash with single light fixed window

Remarks

6 X 7 ft. 12 lights

Me in. crack at threshold

Me in. crack at threshold

Perma Strait Midwest Woodworking

Co.

^16 in. crack at threshold

includes 1 in aluminum

frame storm door with

single-strength glass

Vie in. crack at threshold

l\/Iiinchhausen Soundproofing Co. Inc. Munchhausen Soundproofing Co. Inc. STC 38 sound door

Republic Steel Corp.

[3]

[1]

[1]

[2]

[1]

[1]

[2]

[7]

[2]

[7]

[1]

[3]

[7]

[1]

[1]

[1]

[2]

[7]

[3]

[3]

[3]

42

18

27

33

39

Ref. SIR

24

24

14

15

17

17

19

26

16

24

25

30

18

2126

26

36
144

Construction

hardwood surfaces, high density core, sound retardant door

Plywood Doors

acoustical door

Weatherstripping

Steel Doors

20 ga. steel facing, fiberglass core

steel facing, polyurethane

foam core

16 ga. steel facing

hollow core

18 or 16 ga. CRS surface, kraft El 1-99-1 AS honeycomb

paper core

16 ga. steel facing, flush hol- low metal, single-glazed, in- ternally reinforced acoustical

door

16 ga. steel facing, acoustical

door

hollow metal

18 ga. steel facing, singleglazed acoustical door

18 ga. steel facing, flush hol- low metal, louver, acoustical

door

hollow metal

16 ga. steel facing, acoustical

door, double glazed

16 ga. steel facing, acoustical

fire door

masonry core with steel facing

masonry core with metal

facing

metal facing, concrete core

12 ga. steel facing, acoustical

door

magnetic

Weight Thicklbs/ft' ness

21/4 in.

6.7 13/4 in.

6.7 13/4 in.

9.2 13/4 in.

3.9

5.4

1.25

6.7

21

11.3

7.9

8.1

6.8

7.4

9.3 11.3

13/4 In.

13/4 in.

13/4 In.

13/4 In.

13/4 in.

13/4 in.

13/4 in.

13/4 In.

13/4 in.

13/4 in.

13/4 in.

13/4 in.

13/4 in.

9.5 13/4 in.

7.5 21/2 In.

7.1 13/4 In.

14.8 4 in.

21.9 21/2 in.

Remarl(s

Timebiend core Weyerhauser Co.

STC 36 door sys. Republic Steel Corp.

STC 40 door

U.S. Plywood

STC 49 door

U.S. Plywood

Tearma-Tru entry

System, Lal<eshore

Industries, Inc. Fenestra F6 C4072-

M, Fenestra Door

Products

3500 series

Amweld Build. Prod.

Sound Sentry Door

Emerson Engin. Co.

Overly Manu. Co.

Overly Manu. Co.

sound door

Bob Lench Co.

Overly Manu. Co.

Overly Manu. Co.

Hol-O-Met Corp.

Overly Manu. Co.

Overly Manu. Co.

cam-sea! door

Industrial Acous.

Co., Inc.

industrial door

Industrial Acous.

Co., Inc.

industrial door

Industrial Acous.

Co., inc. Overly Manu. Co.

Ref. SIR

[3] 39

[3] 34

[3] 39

[3] 47

[3]

[3]

[3]

[1]

[3]

[3]

[3]

[3]

[3]

[3]

[3]

[3]

[3]

[3]

[3]

[3]

[3]

[3]

21

27

29

29

34

38

38

38

39

39

40

40

41

44

45

46

47

47
145 16 ga. steel facing, acoustical

door

18 ga. steel facing

16 ga. steel facing, internally

reinforced acoustical door

Composite Doors

flush, wood, plastic laminate

concrete block core, acoustical door

fiberglass reinforced plastic

panel

extruded

plastic

8.6 13/4 in.

14.9 3 in.

23 4 in.

3.4 1% in.

4.1 13/4 in. — 2% in.

2.35 13/4 in.

Overly Manu. Co. [3] 47

industrial door [3] 48

Industrial Acous.

Co., Inc. Overly Manu. Co. [3] 50

Amweid 1500 Series [3] 30

Amweld Build. Prod.

Perma Strait Midw/est [3] 17

Woodworking Co. #873 acous. door [3] 37

Hupp Corp.

rigid polyurethane [1] 26

core

References

Appendix A

SIR Values

[1] Sabine, H. J., Laciier, M. B., Flynn,

D. R., and Quindry, T. L., Acoustical

and thermal performance of exterior

residential wails, doors, and windows,

NBS BBS 77 (Owens Corning Fiberglas,

Granville, Ohio and National Bureau

of Standards, Washington, D.C., 1975).

[2] Veneklassen, P. S., Noise exposure

and control in the city of Inglewood,

California (Paul S. Veneklassen and

Associates, Santa IVlonica, California,

1968).

[3] Purcell, W. E., and Lempert, B., Compendium of materials for noise control,

HEW Publication No. (NIOSH) 75-165

(Illinois Institute of Technology Re- search Institute, Chicago, III., 1975).

[4] Berendt, R. D., Winzer, G. E., and Bur- roughs, C. B., A guide to airborne, impact, and structure borne noise-control

in muitifamily dwellings, U.S. Department of Housing and Urban Development Report No. HUD-TS-24 (National

Bureau of Standards, Washington, D.C., 1967).

[5] IVIiller, L. N., Lecture notes on noise

and vibration control for mechanical

and electrical equipment in buildings

and noise in manufacturing plants (Bolt

Beranek and Newman Inc., Cambridge,

Mass.).

[6] Taylor, M. A., The airborne sound trans- mission loss of a sliding window with

V4 in. glazing, Technical Record, 44/

153/394, Department of Works Commonwealth, Experimental Building Station, Australia (1970).

[7] Bishop, D. E., and Hirtle, P. W., Notes on the sound transmission loss of resi- dential-type windows and doors, J. Acoust. Soc. Am. 43, 880-882 (1968).

[8] Holtz, F., and Verhoven, M., Development of composite windows with high

sound insulation (Proceedings of Inter- Noise 73, Technical University, Copenhagen, Denmark, 1973).

[9] Ingemansson, S., Sound insulating window constructions, Report No. 3:1968, Statens institut for byggnadsforskning,

Stockholm, Sweden (1968).

[10] Manufacturer's literature, Glas-wich

architectural laminated glass. Publication 8.26/DE, Dearborn Glass Company, Bedford Park, Illinois.

[11] Manufacturer's literature, Acousta

glaze. Publication 8, Sitelines, Inc., Van Nuys, California (1969).

[12] Anon., The airborne sound insulation of glass. Environmental Advisory Service

Report No. 4, Pilkington Brothers Limited, Lancashire, England (1970).

[13] Anon., A guide to selecting concrete masonry walls for noise reduction, National Concrete Masonry Association,

Arlington, Virginia (1970).
146
147 Appendix B

Technical Basis of the SIR Method

Objective

The objective of the study that led to the evolution of the SIR method was to derive a simple system to predict the attenuation

of A-weighted sound provided by building

shells from information about the construction of the exterior partitions. It appeared

that such a system would ideally be based

upon some single-figure rating of the acoustical transmission properties of the partition, would simply account for the exterior

surface area and interior furnishings, and

would be relatively insensitive to the details

of the external noise. This appendix briefly

describes the evolution of the system which

appears to satisfy these objectives, and

which is used in this report.

Physical Parameters

In a typical measurement of the noise isola- tion between two adjacent rooms, measure- ments of the space and time averaged mean

sound pressure levels are obtained in the

two rooms, and the difference in levels is obtained. Mathematically, if the sound level

in the first room (chosen as the one with

the higher noise level, because it is assumed

to contain the major source of noise) is denoted by SPL1, and the sound level in the second room is denoted by SPL2, then the term (SPL1 — SPL2) is termed the "noise

reduction" [1], denoted NR,

NR = SPL1 - SPL2.

Throughout this design guide, all sound

levels are actually A-weighted sound pres- sure levels, and SPL1 and SPL2 would each

be measured with the use of the A-weighting

network.

The noise reduction is a physical quantity of great interest, because it tells us about the magnitude of the isolation between

the rooms. This isolation is provided by

the noise insulation properties of the separating partition. But although the noise re- duction accounts for some of the noise in- sulation properties of the partition, it is also

dependent upon details of the furnishings

and dimensions of the second ("receiving")

room as well as the workmanship in the in- stallation of the partition.

In particular, the total amount of absorptive

material in the second room is an important

factor which must be taken into account.

This absorption is measured in terms of the equivalent area of an opening through which

the sound may be totally absorbed or leave

the room, as through an open doorway. The

absorption of the receiving room is thus

given by a term A2 (in square meters, or "metric sabines").

The area of the partition separating the two rooms is also an important factor. Since

all of the sound energy is assumed to pass through the partition, more sound

energy will pass through a large partition

than through a small one, and (all other

factors being equal) a (receiving) room with a large partition will be noisier than would

be the case for a small partition. The area

of the partition separating two adjacent rooms is termed Sw.

In order to eliminate these complicating

factors when considering the relative noise

isolating properties of alternative partitions, a physical parameter related to the (measured) noise reduction is used. This is the "transmission loss", termed TL. Mathematically [1, 2], TL = NR + 10 log,o (Sw) - 10 log o (A2). The transmission loss is the ratio, expressed

in decibels, of the incident sound power per

unit area (incident intensity) to that trans- mitted through and radiated by a unit area

of the partition, independent of the properties of the receiving room. Laboratory

data for the transmission loss properties of partitions are frequently measured and can be found in the literature. These data are generally measured and reported upon in octave-band or one-third-octave bands,

when the acoustic fields in the two adjacent rooms are diffuse as in a reverberant room. The reverberant room environment makes it possible to accurately measure the spaceaveraged sound levels mentioned earlier,

and also makes it possible to assume that
the acoustic field incident upon tine parti- tion in tlie first (source) room is sucli tliat sound energy is incident witli equal probability fronn all directions.

The exterior facade of a building should

provide adequate attenuation of sound arriving from a number of directions. For design purposes, it is often appropriate to make use of sound transmission loss data

which correspond to an average over many

angles of incidence. For some situations,

such as the upper floors of a high rise building very near a highway, the traffic noise

will arrive at near grazing incidence and

data for the transmission loss at this angle

would ideally be selected if available. However, the majority of circumstances are such

that sound can be expected to arrive from

essentially all angles with equal probability. For this design guide, the "random inci- dence" transmission loss data were used in developing the SIR method. These data are appropriate when there is equal probability

of sound arriving from any direction. For design purposes, these data are conservative for sound arriving at the partition from

0° (normal) to beyond 45°. Unless it is known that sound will usually impinge at near grazing incidence, the use of data obtained under random incidence conditions

should be suitable for exterior walls. Published transmission loss data are fre- quently obtained making use of laboratory

measurement procedure; however, procedures for determining the airborne sound

insulation in building elements are also

available [3]. The recommended practice

cited in [3] is specifically directed toward

the problems involved in measurement of the performance of a partition element when

installed as a part of a building, whatever

the configuration, as opposed to a controlled

laboratory environment.

Neglecting the fact that exterior facades are

not usually used to separate two acoustically reverberant systems, for this design

guide we are interested in differences in sound levels on the two sides of the facade

(interior and exterior) of buildings. A slight

complication is introduced if we actually at- tempt to measure the sound levels in the

immediate vicinity of the partition on the

exterior side; the sound level there may be

as much as 6 dB higher than a little further away. This stems from a pressure doubling

effect due to reflections or the presence of the rigid partition, but it is restricted to the region close to the wall and is not a source

of complication when we wish to consider

the difference in diffuse field or random

incidence and reverberant field space aver- aged sound levels. These differences are given by the noise reduction, NR.

Thus to estimate the noise reduction due to a given exterior partition, we need to know

the TL data (from the literature), the area

of the partition Sw, and the total acoustical

absorption of the room, A2. Rearranging the

previous expression for transmission loss,

NR = TL - 10 log,o (Sw) + 10 log,o (A2).

For many architectural acoustics problems,

the majority of the acoustical absorption is provided by materials used as either floor or ceiling coverings (e.g., carpets and acoustical ceilings) or as furniture. A smaller

amount is provided by wall coverings such

as drapes. The total absorption (A2) is therefore often crudely proportional to the

floor area. As we shall see, this observation is used in developing the SIR method,

and corresoonds to practical rules of thumb

frequently used by architectural acousticians. The term (A2), like the term TL, is a function of frequency. Typically, an absorptive

material such as acoustical tile may have

a much higher absorptivity for high fre- quencies than for low. Thus, an evaluation

of "the" noise reduction provided by a partition or enclosure must be conducted on

a narrow band basis, and separate estimates

of the noise reduction for each octave or one-third octave band are generated.

To thoroughly evaluate the difference in A-weighted levels on two sides of a partition from published data, several steps are

required. First one obtains narrow band

spectral information describing the nature

of the sound produced by the noise source

located on the exterior side, applies the A-weighting characteristic, and then deter- mines the overall A-weighted exterior sound

pressure level. Secondly, one evalutes the

partition used in conjunction with the re- ceiving room, using the expression for NR

to generate a table or chart showing the

noise reduction provided by the enclosure

for each narrow frequency band. These

values are then subtracted from Ihe spec- trum level data characterizing the noise

source, to yield the spectrum levels which

characterize the noise within the interior room. The A-weighting characteristic is then

applied, and the overall A-weighted interior sound pressure level is then determined.

The difference in the two overall A-weighted

levels can then be obtained, and will be a measure of the protection from external noise provided by the building shell. Obviously this can be a rather complicated

process. To simplify the computational process, reliance is sometimes placed upon

single figure ratings.

Single-figure rating systems are frequently
used in the evaluation of tlie elements of complex systems. Architectural acoustics

is a field in which several such systems are

found. The American Society for Testing and

Materials has published the details of a

single-figure rating system appropriate for rating the sound transmission properties of interior partitions by the appropriate sound

transmission class (STC) number [4]. Other

single-figure rating systems found in this

field include the impact isolation class (IIC) system for rating the impact noise properties of floor-ceiling assemblies [5], and the

shell isolation rating (SIR) system devised

for this report.

The technical basis for the SIR system used

in this report is similar in many respects to that for the STC system. Both of these sys- tems rely upon test data which characterize

the acoustic transmission loss properties

of test assemblies.

One significant difference between the two

systems (STC and SIR) lies in the fact that the STC single figure rating is a rating describing the noise insulation properties of a partition itself, whereas the SIR is a single

figure rating which is used both to describe

the noise insulation properties of a partition

element ("member SIR") and to describe

the noise isolation properties of an en- closure ("room SIR") which has partitions as its members. It might have been preferable to consistently distinguish between the

SIR numbers appropriate to the shell members or components in contrast with that

for the total enclosure or room but no real confusion should exist as one becomes fa- miliar with the important concept that ulti- mately the room SIR number is used to estimate the difference in A-weighted (equivalent) sound levels between interior and

exterior of the room, corresponding to the

attenuation (noise isolation) provided by

the building shell or the noise reduction.

STC Rating System

For the STC rating system [4] partition trans- mission loss data are compared with a

reference contour in a series of 16 onethird-octave bands ranging from 125 Hz to 4000 Hz. The sound transmission class (for the partition) may be determined by comparison of the transmission losses for the

test specimen plotted on a graph with a transparent overlay on which the STC refer- ence contour is drawn. Figure B-1 illus- trates an STC reference contour. The STC

contour is shifted vertically relative to the

test curve until some of the measured TL

values for the test specimen fall below those

of the STC contour, and the following conditions are fulfilled: (a) the sum of the deficiencies (i.e., the

deviations below the STC contour)

shall not be greater than two times

the total number of frequency bands

for which data are available, and

(b) the maximum deficiency at a single

test point shall not exceed 8 dB.

When the contour is adjusted to the highest

value (in integer decibels) that meets these

requirements, the sound transmission class

for the specimen is the TL value corresponding to the intersection of the reference contour at 500 Hz and the ordinate of the TL

data plot [4]. Note that the reference contour is an essential element in this rating

system.

Basis for Evaluation of Alternative Single

Figure Rating Curves

At the outset of the study which led to the SIR method it was realized that any rating contour chosen for evaluation of the exterior partitions ought to properly account

for the different frequency spectra of the external noise sources. Thus, it was agreed

that the study should include use of several spectra for each of several types of external noise sources; e.g., highway, railway and

aircraft. Because several alternative rating curves were included in the study, it was decided

to use simple (although extensive) statistical studies for choice of the most suitable rating curve. The basis of the process of evaluation consisted of repeated comparison of the single

figure rating number (obtained for a given

exterior partition member or component,

using a specific rating curve and curve

fitting rule applied to the corresponding

partition transmission loss data) with the average shell isolation computed by explicit

detailed evaluation of the differences in

I I I I I I

S 50

I I I I I I 125 250 500 1000 2000 4000 Band Center Frequency, Hz

Figure B-1. An example of the application

of the STC contour to transmission loss data.
150 A-weighted levels which would exist for several given noise source spectra, parti- tion elements, and trial room configurations.

Because all sound levels to be used in this design guide were to be A-weighted, the

single figure method was to correlate with

the difference in A-weighted levels, rather than with other differences of weighted

levels. More explicitly, realize that the use of the

rating curve and curve fitting procedure

yields a single figure indirectly corresponding to the noise reduction properties, since

the noise reduction is a consequence of the transmission loss provided by the partition. For comparison purposes, explicit

evaluation of the difference in A-weighted

noise levels (by the detailed method of calculation) also yields estimates of the

shell isolation or noise reduction properties.

We sought to choose a rating curve yielding a predictable systematic mean difference

between: (1) the single numbers derived

from consideration of the partition itself, and (2) the achieved detailed estimates of the enclosure's (room's) noise reduction.

Furthermore we sought to select a curve

for which the standard deviation of the dif- ferences between the systematic mean dif- ference and the achieved noise reductions was small. Smallness of the standard deviation was considered to indicate that, for the statistical set in consideration, the derived single figure and the differences in A-weighted sound levels were reasonably

well correlated, and that, further, the single

figure numbers characterizing the properties of the partition could be used as the basis of simple estimates of the noise re- duction properties of the enclosure, by ac- counting for the mean difference appropriately.

Thus, the choice of an appropriate rating curve became an exercise in statistical consideration of the available data. For this study, spectral data were obtained

from the literature, for eleven examples of highway noise, eleven examples of railway

noise, and five examples of aircraft noise

[6-18]. Figures B-2 through B-4 illustrate the general characteristics of these spectra,

when normalized to equal A-weighted levels.

D)

<

a>

ffi •a

>

_joc

to

ffi>S

oO

100 1000

Frequency, Hz

10000

Figure B-2. Eleven highway spectra

normalized to equivalent A-weighted

sound pressure levels.
100 1000 10000

Frequency, Hz

10000

Frequency, Hz

Figure B-4. Five aircraft spectra normalized to equivalent

A-weiglnted sound pressure levels.
152 Prior work of Ljunggren [19] had suggested

that a single number rating should be

chosen upon some measure of the degree

to which partition transmission loss data

"fit" the A-weighted typical exterior noise

band levels. For the noise spectra chosen

in his study, these considerations led to choice of a rating contour consisting of a

straight line sloped at +3 dB/octave, and

this contour was selected for evaluation.

Much published data are available, however, for the STC single figure ratings characteristic of partitions, and it was thought

prudent to consider whether the use of this rating contour (and thus, these published

data) would be desirable for the purposes

of this design guide.

Still a third trial contour was considered:

a straight line with zero slope (a "flat" contour). This was thought to be desirable on the basis of certain simple curve-fitting

properties.

These three trial contours were to be applied to the transmission loss data for a

large number of exterior partitions and partition components such as doors, windows,

decorative panels, etc. The available litera- ture was extensively reviewed to obtain

these data. It should be noted that there are some contradictory data to be found in the literature, i.e., discrepant data published

for nominally identical constructions, and

that, as well, the descriptions of construction details are often imprecise. Ideally, the

data should be critically reviewed and a rep- resentative selection of exterior partition

elements and components chosen. For this study, transmission loss data for more than

500 exterior partition elements were col- lected from the literature [19-31].

.5 , ,

A trial room was selected, with dimensions

of 12 ft wide by 8 ft high by 25 ft deep.

Because of the possible sensitivity of single

number curve fitting procedures to the details of interior absorption, three different

interior configurations were studied for the

trial room. These correspond to acoustically

"hard", "medium", and "soft" rooms. The

absorption coefficients were computed from

published data. The "hard" room was as- sumed to have a floor of vinyl asbestos tile on concrete, walls of gypsum board on 2 in. by 4 in. wooden studs spaced 16 in. on

center, and a concrete ceiling. No allowance was made for absorption due to furniture or occupants for any of the configurations, so that it is probable that the "hard" configuration represents an extreme not often found in practice. In the "medium" room,

the absorption coefficients for a carpet and

pad were substituted for those of the vinyl

asbestos tile. For the "soft" configuration,

a fissured tile ceiling was also included.

Data for the average sound absorption coefficient, corresponding to the term (A2)

divided by the total interior surface area

are given in Figure B-5 for the three configurations.

Statistical Studies

Initially, for each of the 27 examples of exterior noise spectra, computations of the

difference in A-weighted levels were made

for each of 507 exterior partitions or partition elements, for the "medium" configurations of the trial room. For comparison, the

507 partitions were assigned single number

ratings using a simple curve fitting proce- dure and the "flat" reference contour. The mean difference between the single numbers thus obtained and the differences in

I

a> 3

n.2

<U Q. > w < o

01 JQ<

.3 "

200 500 1000 2000

Vs -Octave Band Center Frequency, Hz

5000 10000

Figure B-5. Average sound absorption coefficients versus frequency for three room configurations.
A-weighted levels computed using the detailed transmission loss data was then obtained by averaging over the 507 partition

elements for each of the 27 spectra. The

standard deviation about the mean differ- ence was also computed.

The magnitude of the standard deviation for each of the 27 sets of data was such that the differences between the magnitude of the mean differences were small in comparison. Thus, an insensitivity of the comparison to the details of the spectral characteristics was indicated. This indicated

that, at the least, data for subsets of dif- ferent class of noise source would be adequate as opposed to computations for each

specific source, and that a method involving

averaging over all exterior noises might be

successful. "Success", or "adequacy" of these studies was understood to be primarily that the standard deviations were not appreciably enlarged when comparing the standard deviations for subsets with the 27

individual standard deviations.

Studies were next conducted by computing

the corresponding statistics again for the twenty-seven spectra, but including the use

of "flat", +3 dB/octave, and STC rating

contours, again for the more than 500 partitions, and including the three trial room

configurations. However, because of the

noted insensitivity to details of the spectral

characteristics, the statistics were this time

computed for each of the three subsets cor- responding to different classes of external noise source (highway, railway and aircraft) as well as when averaged over the complete

set of twenty-seven noise source spectra.

Thirty-six values of the mean differences

and standard deviations were thus computed; corresponding to four sets of source

spectra (3 sub sets of class of source plus

the complete set including the 27 source

spectra); three rating curves; and three absorption configurations. These data are shown in Table B-1.

It is apparent that the differences between

the data for each of the subsets corresponding to differing classes of sources were modest relative to the sizes of the standard

deviations so that the separate considerations of different classes of source is probably not warranted. Consideration of these

data was thus subsequently restricted to the statistical data for the complete set which include consideration of all 27 source

spectra.

The most desirable single figure rating

system would be that characterized by a small value of standard deviation. For the "medium" room configuration, the data

obtained using the 3 dB/octave curve are characterized by the smallest standard deviation (2.10 dB), followed by the "flat" (2.19 dB) and STC (2.69 dB) data. For the

"soft" room configuration, the relative rank

orderings, in terms of increasing size of the standard deviation, are the "flat", 3 dB/octave, and STC data. Finally, for the "hard" configuration, the rank orderings are STC, 3 dB/octave, and "flat". Though no one rating curve is superior for all room

configurations, the differences between the "3 dB/octave" and "flat" data for the two most representative room configurations are small and the data using these two curves

are superior to those for the STC contour.

In view of the fact that the 3 dB/octave data

are superior to the "flat" contour (and only

slightly inferior to the STC contour data)

for the "hard" room configuration, a slight overall preference is shown for the 3 dB/

octave contour as Ljunggren suggested.

In order to test the sensitivity of this choice

Table B-1

statistical analysis of mean differences and standard deviations between the single figure derived by curve fitting to

partition transmission loss data and the level difference. Three room absorption configurations, twenty-seven noise spectra, 507 partitions and three contours were considered. All data are units of dB.

3 dB/octave STC "Flat" Contour Contour Contour Mean Diff. Std. Dev. Mean Diff. Std. Dev. Mean Ditf. Sid. Dev. Hard Room Configuration

11 Highway Spectra

11 Railway Spectra

5 Aircraft Spectra

Complete Set of 27 Spectra

Medium Room Configuration

11 Highway Spectra

11 Railway Spectra

5 Aircraft Spectra

Complete Set of 27 Spectra

Soft Room Configuration

11 Highway Spectra

11 Railway Spectra

5 Aircraft Spectra

Complete Set of 27 Spectra

-2.32 1.57 —5.47 1.53 -0.71 2.63 -1.85 1.76 -5.00 1.58 -0.24 2.91 -1.46 1.98 -4.61 1.66 -1-0.15 3.21 -1.97 1.76 -5.12 1.61 -0.36 2.88

-f 2.01 1.94 -1.13 2.66 -1-3.63 1.78

-1-2.75 2.09 -0.39 2.67 -1-4.37 2.23

-1-3.39 2.12 -1-0.25 2.50 -1-5.01 2.56

-1-2.57 2.10 -0.58 2.69 -1-4.19 2.19

-f3.77 2.31 -fO.63 3.19 -1-5.39 1.65 -f4.65 2.51 -f 1.50 3.24 -1-6.27 2.23

-1-5.42 2.33 -1-2.27 2.92 -1-7.03 2.39 -^4.44 2.48 -t-1.29 3.22 -6.05 2.14
of preferred rating curve to the composition

of the set of trial partitions, a subset of 50

external partition elements was chosen, with

attention to selection of a more representative assortment of walls, windows and

doors. (It had been noted that the set in- volving 507 partition elements included more windows and doors than external partitions. Thus it was decided to select a subset which contained a smaller relative number of windows and doors, and to see

if the statistical studies differed appreciably.) Once again, statistical analysis of the data was conducted, averaging over the one set of 27 external noise spectra, for three configurations of absorption, and three

rating curves. Nine values of the mean

differences and standard deviations were

thus obtained. For the medium room absorption this time the rank orderings are

"flat", 3 dB/octave and STC. For the "soft" configuration, the orderings are "flat", "3

dB/octave", and "STC", while for the "hard"

conf guration, the orderings are "STC",

"3 dB/octave", and "flat". Here the dif- ferences are slightly in favor of the "flat" contour as opposed to the 3 dB/octave contour for the two most representative room

configurations, with a preference shown to the STC and 3 dB/octave contour for the

"hard" configuration.

Comparison of the results of these two

studies shows that there is not really any

marked superiority to either use of the 3 dB/

octave or "flat" contour, but that the STC

contour is generally not favored in this study.

A more detailed and exhaustive study than

that conducted here would be essential to clearly show the superiority of any method.

However, such a study should include adequate definition of "typical" long term time

averaged exterior noise source spectra, consideration of the transmission loss characteristics of a representative selection of "typical" exterior partition elements, careful

definition of "typical" absorption data for "hard", "medium", and "soft" room configurations, and variation of room geometrical parameters. In the absence of these

data, a decision to make use of the 3 dB/

octave contour as suggested by Ljunggren was made. This decision was motivated by

the absence of clear demonstration of the

superiority of the alternative contours ("flat" and STC contours), because of the apparent

adequacy of such a contour (as demonstrated by these statistical studies), and by

a desire to avoid advocacy of any additional

reference contours.

Evolution of The SIR Method from the Statistical Data

In order to make use of the single figure

ratings characterizing the partition's noise

isolation properties (the "member SIR") in order to predict the difference in A-weighted

levels, it is necessary to account for obvious systematic factors relating to the room

and partition which enter into the relation- ship. Two of the immediate factors entering into the analysis are the differences due

to room absorptivity and partition area. By comparing the data for the hard, medium,

and soft room configurations when averaged

over the smaller set of partitions and 27

spectra, when using the chosen 3 dB/octave

rating curve, the mean differences are —1.8,

+2.3, and +4.3 dB. That is, on the average,

the single number assigned to the partition

differs from the actual computed difference

in A-weighted sound levels by these

amounts. To the nearest integer, these are —2, -f2, and -)-4 dB. Thus, for example,

the change from "medium" to "soft" room

configuration Increases the mean difference

by 2 dB. This difference is probably principally due to the additional absorption at high frequencies provided by the "soft" room configuration. Therefore, a simple

method of accounting for differences in room absorption is suggested; namely, adding appropriate correction factors to the

partition's single figure (member SIR) number to allow for the absorptivity of the in- terior volume. These considerations led to the room absorption corrections on the SIR

worksheet for the hard and soft configurations, and the additional mean difference for the medium room configuration of -\-2 dB

is "built into" the room geometry correction.

The next parameter to be systematically

studied was the effect of variation of the area of the test panel relative to the total absorptive area of the room. The total amount of acoustical absorption in this model is approximately proportional to the

floor area (particularly for the "soft" configuration). It is apparent that otherwise

identical rooms will be such that rooms with

larger total floor areas will have the larger

absorption, and hence, lower interior noise.

Considerations of variation of the exterior

wall area (corresponding to the term Sw)

relative to the floor area led to the evolution

of Table 6-4, which allows us to adapt the

SIR predictive method to account for rooms

with various ratios of exterior wall to floor area.

In order, then, to obtain the difference in A-weigh+ed levels in the room and at the

exterior of the building, the following steps

are indicated:

1) Obtain the SIR single-figure rating appropriate for the exterior partition wall through the use of the selected curvefitting procedure and the -f3 dB/
1

octave contour. This is a "member

SIR".

2) Account for the average absorptivity

of the room's surface absorption characteristics by allowing absorption cor- rections of -\-2 dB for the soft room

configuration, and —4 dB for the hard room configuration.

3) Account for the specific room geometry (floor area/partition area) by consulting Table 6-4 to derive a correction factor which accounts for the fac- tors [10 log,o (Sw)] and [—10 logio

A2], and which also incorporates a factor of -\-2 dB to account for a sys- tematic mean difference noted in the

statistical analysis for the medium

room configuration.

To this point, the SIR procedure provides an estimate of the difference in levels (the

"room SIR") based upon three factors:

... a single figure rating derived from, and

proportional to, the external partition

transmission loss data.

. . . the room acoustic absorption, corre- sponding to the frequency characteristics of the three differing room absorption configurations.

. . . the room geometry correction factor accounts for the relative sizes of the

exterior partition and the total amount

of acoustic absorption, (proportional

to the floor area).

To illustrate these facts, consider the case

of the trial room used for the study. As- sume that the exterior partition wall is 8 ft by 12 ft, with a SIR number of 30. The floor area is (12 ft X 25 ft = 300 ff). The room

geometry correction factor is -\-2 dB be- cause the ratio of exterior partition wall area to floor area is 0.32 (see Table 6-4). For the "medium" room case (carpeted

floor, bare walls and hard ceiling) no additional correction factor is required. Thus, the

level difference is (30 + 2) = 32 dB. That

is, the A-weighted sound level of the acoustic field incident upon the exterior side of the wall will be 32 dB larger than the

A-weighted sound level in the interior of the room.

Next, it is necessary to consider the effect of the presence of several partitions. The

analytic model chosen for this case assumes

in effect that the room can always be re- garded as a superposition of several nominally identical rooms, each of which has

only one wall exposed to the exterior noise.

In such a case, simple logarithmic combination of the levels within each of the indi- vidual rooms of the analytic model will yield the level corresponding to the case which has several exterior partitions with one room. This is because the individual

rooms of the analytic model each have a sound pressure level which arises as a con- sequence of the acoustic power flowing

through the individual exterior walls, and

because logarithmic combination of sound

pressure levels is the proper way to ac- count for the addition of quantities proportional to power.

To account for the derivation of the SIR

number appropriate for composite partitions, it is necessary to account for two

factors; the areas of the individual components and the differences in their sound

transmission properties. The data of Table

6-2 were generated from consideration of an expression derived for the transmission

loss of composite partitions, accounting for these two variable factors. An incremental

change in transmission loss will correspondingly affect the SIR number.

The tabulated data to account for the pres- ence of leaks is obtained from considerations similar to those used to account for the existence of composite partitions. Here,

the analytic model assumed that the leaks

constitute finite openings with a zero trans- mission loss. Although this is an oversimplified model, and does not account for the possible resonance effects known to occur for narrow slot-like openings, it is nonetheless relatively simple, and may be

adequate for typical leaks which occur due

to poor and moderate workmanship.

Determination of the Shell Isolation Rating

The SIR rating of partitions or partition ele- ments not listed in Appendix A may be determined by using laboratory test data of transmission loss versus one-third octave

or octave band frequency, if these data are

available. For the SIR single-figure rating

system, the transmission loss data are compared with the SIR reference curve

(a -|- 3 dB/octave straight line with an

intercept of the 0 dB axis at 500 Hz) in each

of the one-third octave or octave bands of data. The curve fitting technique used to determine the SIR number for a particular

partition or element is related to that used

to determine the STC rating [4]. That is, the transmission loss data for the test speci- men is plotted on a graph with a transparent

overlay on which the SIR reference contour

is drawn. The SIR contour is shifted vertically relative to the test curve until some

of the measured TL values for the test specimen fall below those of the SIR contour such that the sum of the deficiencies

(i.e., the deviations below the SIR contour)

in one-third octave or octave bands is less than two times the total number of frequency

bands for which data are given. An example

of this curve fitting process is shown in
Figure B-6. For this example, data are given for 16 bands. The sum of the deficiencies must be less than 32 dB in this case. When the contour is adjusted to the highest

value (in integer decibels) that meets this requirement, the SIR number for the speci- men is the TL value corresponding to the

position of the 500 Hz coordinate of the

SIR curve. Note that the primary difference

betw^een the SIR and STC curve fitting techniques, aside from the difference in refer- ence contours, is that the requirement that the maximum deficiency at a single test point not exceed 8 dB is not used in the SIR system. Also, it should be pointed out

that the use of one-third-octave band data is preferable to the use of octave band data be- cause there are more data points and thus

finer resolution of the actual ' transmission

loss characteristics of the test specimen.

Discussion

There are several readily identifiable deficiencies of this method of accounting for building shell sound transmission, and it is important to state some of the limitations so that there is no misunderstanding about

the range of validity of this analysis.

As previously mentioned, in a typical urban

noise situation, the acoustic field incident

upon the building exterior will not be a dif-

'° II I I

I I

I 11 I I I I 125 250 500 1000 2000 4000

Band Center Frequency, Hz

Figure B-6. Example of curve-fitting technique for determination of SIR value of a test specimen based upon one-third octave band transmission loss data. SIR

contour is +3 db/octave straight line with

ordinate intercept at 500 Hz equal to the

test specimen SIR value.

fuse acoustic field as is assumed in both

the STC and SIR models, but is more probably a wave incident at some specific angle

(or narrow range of angles) of incidence.

Under these conditions, the transmission

loss data, already known to be frequency

dependent, are also dependent on the angle

of incidence. These complications were

judged to be beyond the scope of this report.

The choice of the +3 dB/octave contour

for the evaluation of the SIR method was

predicated upon comparative consideration

of more than 500 exterior partitions or partition elements with three trial contours,

twenty-seven source spectra, and three room absorption configurations. While this

is not as exhaustive a study as might be

conceived, this choice of reference contour does have the virtue of relative simplicity, and the averaged standard deviations

of the difference between the computed

A-weighted level difference and the results

of the SIR method in the statistical analysis are typically of the order of 2 dB, and the mean differences have been accommodated

in the adaptations of the "member SIR"

into the "room SIR". The optimum choice of a reference curve

is undoubtedly dependent upon the details

of the exterior noise spectra under consideration [33]. In the absence of long-term

time-averaged exterior noise spectral data, as would be most appropriate for a design

method keyed to equivalent sound level metrics, the present selection of a reference curve should be adequate for interior usage.

It is also important to acknowledge that the choice of representative room absorption characteristics will influence the details of the method. In reality, few rooms

are as "hard" as the "hard" room approximation and it is certain that other "representative" room absorption data and correction factors can be conceived. Further- more, the correction factor for "leaks" could

be more sophisticated than that suggested

here. But once again, it was thought desirable to provide a simplified model and

computational method.

Finally, it must be admitted that the evolution (and evaluation) of single-figure computational methods for the estimation of acoustical properties is an important re- search topic. The present method is only one example of such a procedure, and this method may be subject to modification as

data on its utility and comparisons with

experimental data become available. Current research at the National Research

Council in Canada [34, 35] has led to the

evolution of an alternative simplified method

directed toward control of aircraft noise in
buildings, and the work of Ljunggren in Sweden [19] can be cited as yet anottier

exannple directed toward traffic noise design considerations. Tlie autiiors of this design guide encourage the interested

reader to mal<e use of alternative simplified computational methods and to consider

the use of more detailed methods as their understanding of the acoustics involved in designing for noise control increases. Such

an increased understanding can only lead

to a better environment.

References

Appendix B

SIR Method

[1] Beranek, L. L., Acoustics (McGraw-Hill

Book Co., Inc., New York, N.Y., 1954).

[2] American Society for Testing and Materials, E90-70, Standard Recommended

Practice for Laboratory Measurement

of Airborne Sound Transmission Loss

of Building Partitions in Part 18, Book

of ASTM Standards, 1975 (ASTM,

Philadelphia, Pennsylvania).

[3] American Society for Testing and Materials, E336-71, Standard Recommended Practice for l\Aeasurement of Airborne Sound Insulation in Buildings

in Part 18, Book of ASTM Standards,

1975 (ASTM, Philadelphia, Pennsylvania).

[4] American Society for Testing and Materials, E413-73, Standard Classification for Determination of Sound Trans- mission Class in Part 18, Book of ASTM

Standards, 1975 (ASTM, Philadelphia,

Pennsylvania).

[5] American Society for Testing and Materials, E492-73T, Tentative Method of Laboratory Measurement of Impact

Sound Transmission Tfirougti Floor- Ceiling Assemblies Using the Tapping

Machine in Part 18, Book of ASTM

Standards, 1975 (ASTM, Philadelphia,

Pennsylvania).

[6] Lyon, R. H., Lectures in Transportation

Noise (Grozier Publishing inc., Cambridge, Mass. 1973).

[7] de Lange, P. A., Sound insulation of glazing with respect to traffic noise,

Applied Acoustics 2, 215-236 (1969).

[8] Ingemansson, S., Insulation against

traffic noise (Proceedings of Inter- Noise 73, Technical University, Copenhagen, Denmark, 1973).

[9] Lawrence, A., Hegvold, L., and Green,

R. C, Prediction of traffic noise spectrum levels for use in building design

(Proceedings of 6th International Congress on Acoustics, Tokyo, Japan,

1968) .

[10] Galloway, W. J., Clark, W. E., and Kerrick, J. S., Highway noise: measurement, simulation, and mixed reactions,

NCHRP Report 78 (Bolt Beranek and

Newman Inc., Van Nuys, California,

1969) .

[11] Anon., Community noise, U.S. Environmental Protection Agency Report

NTID300.3 (Wyle Laboratories, El Se- gundo, California, 1971).

[12] Anon., Transportation noise and noise

from equipment powered by internal combustion engines, U.S. Environmental Protection Agency Report

NTID300.13 (Wyle Laboratories, El Segundo, California, 1971).

[13] Anon., Noise and vibration characteristics of high speed transit vehicles,

U.S. Department of Transportation Report OST-ONA-71-7 (Wilson, Ihrig, and

Associates, Inc., Berkeley, California,

1971).

[14] Manning, J. E., Cann., R. G., and Fredberg, J. J., Prediction and control of

rail transit noise and vibration —

a

state-of-the-art assessment, CC Report

No. 74-1 (Cambridge Collaborative,

Inc., Cambridge, Massachusetts, 1974).

[15] Rickley, E. J., Quinn, R. W., and

Sussan, N. R., Wayside noise and vi- bration signatures of high-speed trains

in the northeast corridor, U.S. DOT Report DOT-TSC-OST-73-18, U.S. De- partment of Transportation, Washington, D.C. (1973).

[16] Path, J. M., Blomquist, D. S., Heinen,

J. M., and Tarica, M., Measurements

of railroad noise—line operations, yard

boundaries, and retarders, Joint EPA/

NBS study, U.S. Environmental Protection Agency Report 550/9-74-007,

NBS Report No. NBSIR 74-488 (National Bureau of Standards, Washington D.C, 1974).

[17] Anon., A study of the magnitude of transportation noise generation and

potential abatement: Vol. Ill —airport/

aircraft system noise, U.S. Department

of Transportation Report OST-ONA71-1 (Serendipity, Inc., Arlington, Vir- ginia, 1970).

[18] Private communication, R. W. Young

(Department of the Navy, Naval Undersea Center, San Diego, California) to D. R. Flynn (National Bureau of Standards, Washington, D.C), 26 June 1973,

[19] Ljunggren, S., Sound insulation of windows with respect to traffic noise. Report H-3065-A (Ingemanssons Ingenjorsbyra, Gothenburg, Sweden, 1972).

[20] Sabine, H. J., Lacher, M. B., Flynn, D.

R., and Quindry, T. L., Acoustical and
thermal performance of exterior resi- dential walls, doors, and windows, NBS

BSS 77 (Owens Corning Fiberglas,

Granville, Ohio and National Bureau

of Standards, Washington, D.C., 1975).

[21] Veneklassen, P. S., Noise exposure and

control in the City of Inglewood, Cali- fornia (Paul S. Veneklassen and Associates, Santa Monica, California, 1968).

[22] Purcell, W. E., and Lempert, B., Compendium of materials for noise control,

HEW Publication No. (NIOSH) 75-165

(Illinois Institute of Technology Re- search Institute, Chicago, III., 1975).

[23] Berendt, R. D., Winzer, G. E., and Bur- roughs, C. B., A guide to airborne,

impact, and structure borne noisecontrol in multifamily dwellings, U.S. Department of Housing and Urban Development Report No. HUD-TS-24 (National Bureau of Standards, Washington, D.C., 1967).

[24] Miller, L. N., Lecture notes on noise

and vibration control for mechanical

and electrical equipment in buildings

and noise in manufacturing plants (Bolt

Beranek and Newman Inc., Cambridge,

Mass.).

[25] Bishop, D. E., and Hirtle, P. W., Notes

on the sound transmission loss of resi- dential-type windows and doors, J. Acoust. Soc. Am 43, 880-882 (1968).

[26] Holtz, F., and Verhoven, M., Development of composite windows with high

sound insulation (Proceedings of Inter- Noise 73, Technical University, Copenhagen, Denmark, 1973).

[27] Ingemansson, S., Sound insulating window constructions, Report No. 3:1968,

Statens institut for byggnadsforskning,

Stockholm, Sweden (1968).

[28] Taylor, M. A., The airborne sound

transmission loss of a sliding window

with Va in. glazing, Technical Record

44/153/394, Department of Works

Commonwealth Experimental Building

Station, Australia (1970).

[29] Anon., A guide to selecting concrete masonry walls for noise reduction, National Concrete Masonry Association,

Arlington, Virginia (1970).

[30] Anon., The airborne sound insulation

of glass, Environmental Advisory Service Report No. 4, Pilkington Brothers

Limited, Lancashire, England (1970).

[31] Manufacturer's literature, Glas-wich ar- chitectural laminated glass. Publication 8.26/DE, Dearborn Glass Company, Bedford Park, Illinois.

[32] Manufacturer's literature, Acousta

glaze. Publication 8, Sitelines, Inc., Van Nuys, California (1969).

[33] Rettinger, M., Sound insulation for buildings, J. Acoust. Soc. Am 56 (5), 1511-1514 (1974).

[34] Donate, R. J., Insulating houses against

aircraft noise, J. Acoust. Soc. Am. 53

(4), 1025-1027 (1973).

[35] Anon., New housing and airport noise,

Report No. NHA 5059, Central Mort- gage and Housing Corporation, Ottawa,

Canada (1973).
Appendix C

Sample Worksheets

PRELIMINARY SOURCE EVALUATION WORKSHEET

1 2 3 4 Noise

Snurpp

Building-

.^n 1 1 rpp Distance

Might there

hp pYpQCOiv/p

noise? (yes

or no) [See

Table 2-2]

If the answer

i c n n in q ! 1

1 O 1 1 U III Ct 1 1 cases,

for highways,

railways, or

airports *

If the answer

is yes for one

or more of the sources,

Highway #1 feet Omit Section 2

of Chapter 5 Obtain the data

and perform the #2 feet computations

outlined in Sec. #3 feet

^1 oi L-napier o

for each high-

#4 feet way with a yes

answer.

Railway #1 feet Omit Section 3

of Chapter 5 Obtain the dat^

and perform the

computations

outlined in Sec.

3 of Chapter 5

for each railway

with a yes answer.

#2 feet

#3 feet

#4 feet

Airport #1 miles Omit Section 4

of Chapter 5

Obtain the data

and perform the

computations

outlined in Sec. 4 of Chapter 5

for each airport

with a yes answer.

#2 miles

#3 miles

#4 miles

* If the answer is no for all three types of transportation system noise source, this design guide evaluation is not necessary.
160

Pivot +Point

Heavy

Trucks

20 30 40 50 I -h +

^ I 60 70

+

20

SPEED; MPH

+ + +

30 40 50

Automobiles and Medium Trucks

60+

70 -f

HNL

dB

100

90

80

70

60

50

40

Predicted Noise Level

DC

FT

30 -

40 —

50 -

70 -

100-

150-

200

300

400

500

700

1000-

1500

2000 —

Distance To

Observer

Highway Noise Prediction Nomogram
Highway Worksheet 1

Building Project Highway Number

Location

Owner

Site point or building room lor which sound pressure

levels are being estimated

Designer Date Revised

Roadway—Building Site Distance: DC (Feel)

Medium Trucks Heavy Trucks

Average Vehicle Speed, mph SA SM SH

Total Number ol Vehicles ^^^^^^^^^^^^^^^

a) Leq(1)

Leq(1) No Shielding

Total Shielding Correction (Highway Worksheet 2)

Leq(1) Corrected lor Shielding

Leq(8) No Shielding

b) Leq(8)

Total Shielding Correction (Highway Worksheet 2)

Leq(8) Corrected lor Shielding

Leq(24) No Shielding

c) Leq(24)

Total Shielding Correction (Highway Worksheet 2)

Leq(24) Corrected lor Shielding

HNL

RDN

CDN

d) Ldn

Ldn No Shielding

Total Shielding Correction (Highway Worksheet 2)

Ldn Corrected lor Shielding

Building Site Noise Due To Several Highways
Highway Worksheet 2

Highway Number

Building Project

Location

Owner

Site point or building room for which sound pressure

levels are being estimated

Designer

Date Revised

Roadway—Building Site Distance: DC (Feet)

Shielding Geometry

Path Length

Difference

Autos And Medium

Trucks

Heavy

Trucks

Barrier

DB HB hB

Elevated Roadway

DE HE

'a/m

Depressed

Roadway

DD HD hD

•-a/m

Correction For

"Infinite" Shielding

Element

Auto

CSA/M

Medium Truck

CSA/M

Heavy Trucit

CSH

Correction For

"Finite" Shielding Element

Included Angle Ratio, RA

Auto

CSA/M

Medium Truck Heavy Truck

CSA/M CSH

Building Barrier

Vegetation dw

CSB

CSV

Total

Shielding

Correction

Auto Medium Truck Heavy Truck

CSA/M + CSB + CSV CSA/M + CSB + CSV CSH + CSB + CSV
163 Railway Worksheet 1

Building Project

Location

Owner

Railway Number

Site point or building room tor which sound pressure

levels are being estimated

Designer Date Revised

Railway—Building Site Distance: D (Feet).

Does this type of train use

the track being analyzed?

Diesel-Electric or All-Electric Locomotive

Average Train Speed, S, mph

Average number of cars, nc Average train length, LT, feet

Average

a) Leq(1)

Number

: N1

of Passbys ^^^^^^^ b) Leq(8) : N8

c) Leq(24) : N24

d) Ldn

Diesel-Electric Locomotive //^/^/^ ^/^^/^X/^^^^

Reference Level, LS

Distance Attenuation, DAL

Railway Cars

Reference Level, CL

Duration Factor, CD

Track Characteristics, CT

Distance Attenuation, DAG

Predicted Noise Levels

a) Leq(1)

b) Leq(8)

c) Leq(24)

d) Ldn

CN1

CI

Leq(1) No Shielding

Total Shielding Correction (Railway Worksheet 2) Leq(1) Corrected for Shielding CN8

C8

Leq(8) No Shielding

Total Shielding Correction (Railway Worksheet 2)

Leq(8) Corrected for Shielding CN24

C24

Leq(24) No Shielding

Total Shielding Correction (Railway Worksheet 2) Leq(24) Corrected for Shielding CNCDN

Ldn No Shielding

Total Shielding Correction (Railway Worksheet 2) Ldn Corrected for Shielding

Total Railway Noise

Freight Trains

NL

ND NN

Conventional Passenger Trains

NL

ND NN

Rapid Transit Trains

Diesel-Electric Locomotive

Railway Cars

^zzz

Diesel-Electric Locomotive V77///////A

777-////////^

Railway Cars Railway Cars

V/////////////////////////A
Railway Worksheet 2

Railway Number

Building Proiecf . . ^ . ^. ^ Site point or building room for which sound pressure

levels are being estimated

Location Designer Owner Date Revised

Barrier Elevated Railway

Depressed

Railway

Shielding Geometry DB HB hB a DE ' HE a DD HD hD a

Railway—Building Site Distance: D (Feet),

Path Length

Difference

Railway Cars

DieselElectric Locomotive

Ac

A/

Be

Bl

Cc

CI

Lc

Railway Cars Diesel-Electric Loc.

Correction For

"Infinite" Shielding Element CSC CSL

Included Angle Ratio, RA

Correction For

"Finite" Shielding Element

Railway Cars

CSC

Diesel-Electric Loc.

CSL

Building Barrier CSB

Vegetation dw CSV

Railway Cars Diesel-Electric Loc.

Total Shielding Correction CSC -t- CSB + CSV CSL + CSB + CSV

Track Characteristics

a b c d

Presence of Switching Frog

or Grade

Crossing

Radius of Bridgework Welded

Track

Jointed Track

Tight Curve « 900 Feet)

In Feet

Concrete

Structure

Steel Girder

with Concrete

or Open Tie Deck

Steel Girder

with Steel

Plate Deck
Aircraft Worksheet 1

Building Pro|ect

Location

Owner

Site point or building room (or which sound pressure

levels are being estimated

Designer

Date Revised

Contour Maps Available y///////////////.

if Building is on or very near Contour #1 or #2, Record that value on Line 11.

It not, obtain the data of Lines 2 and 3

Contour Values CNR or NEF #1 CNR or NEF #2

Building Location Between Contours #1 and #2

X2 C5 CIO

CNR or NEF Value At The Building Site Also Record on

Line 11

Contour Maps Not Available y///////////////-

5 Number of Jet Operations

NJday NJnight NJeff

6

Airport Category (Check One)

1 2 3 4

If building is on or very near the NEF 30 or NEF 40 Contour, record that value on Line 11.

If not, obtain the data on Line 8.

Building Location Between NEF 30 and NEF 40 Contours
Iu9UJisn|pv uoisSjoisuBJ J. — (J3W0|) yis — HIS ujooy a

L-9 eiqei luojj luemisnlpv UOISSIUJSUBJl t

5 HIS — fr'e'S'l dIS = 93U3J3K'a 9in|0sqv CT

lueiDisnlpv uoissiujsuBJj. — (JaMOi) ulS = f'Z'l'l HIS Q.Q.

L-9 eiqei ujojj juaiuisnlpv uojssiujsuEJi OO

^dlS — G'2'L HIS ~ a3U3J3|4!a 3in|0sqv C

C

luemisnfpv uoissiiusubji — (jawoi) yis = 'Z'Z'i HIS £E

L-9 9|qei ujoji lueiuisnlpv UOjSSIUJSUBJX =

G dIS — S'l dIS = eouajaiiiQ einiosqv

juaujisnlpv uoissiujsueji — (jomoi) his = 2'L HIS

L-9 eiqei ujojj luaiuisnlpv uo!SS|ujsubj_l -

S HIS - L HIS = aouajaniQ ainiosqv sJOpej uoiioejjoo uojidjosqv pu0 eaiv "aeeHBai joj pajsnlpv yis =

B9JB iiBM (0 %05 jaAOD sadeip

i! JO Buineo OjjsnooE ii z+ iaiu^

^-9 Biqej. LUOJJ jopej uojioajjoo AJieujoar) luoou TJ

AJieiuoao ujooy—eejv Jooy oi eajv jaqiua^ iiaqs to oiibu o

e-9 eiqei ujoji 9Bbhb9-i j]V uo pasBg HIS peisn[pv n

^Be^ eJBnb6 00L/g9i^3U| ejsnbs ui bQb'ubb'] jiv eiBUjiisg s

Jopej uojpajjoo dIS eiisodujoQ + q yis = aoav HIS

2-9 eiqsj, ujojj jopej uoiiosjjoo yis aiisodujoQ X

(a dIS — D8V dIS) = 90U9J9J(!a

(B9JV J9qUJ3V^ l|9L|S/e9JV lU9UOdUJ00) 69JV iBuoipejj Q luauodujoQ >

joioej UOIP9JJO0 yis aiisodujoo + o yis = oav dIS

2-9 9|q8j. oiojj jopBj U0I109JJ0Q uis eiisodujoo -

{0 HIS - 9V HIS) =1 90UeJ9J)!a "

{eejv JQQuja/^ liaqs/sajv 0 ;u9uodujoo) B9JV iBuoiioBj^ 0 lueuodujoo

*•

jopej uoijDajJOQ yis ensodujOQ + g yis = gv dIS 17

2-9 eiqBj. ujojj JopBj uoipejjoo yis aijsodujoo O.

(9 HIS — V dIS) :90u9jejj!a O

(Bejy J9quj9v^ l|9LJS/e9JV 9 luauodujoo) B9JV IBUOjpBJJ g lueuodLUOQ C

leej 9JBnbs ui eejy lueuodujoo E

leej UI 2 ON uojsueujia aoej juauodujoQ -

leej u| L uo|€U8Uj|Q 9dbj jueuodujOQ

1 X M—199( 9JBnbs UI e9JV Jooij ujooy

)99;J U| 6U0!SU3UJ|a UJOOy qi6uei

LJIPIM

V X|pu9ddv UJOJJ yis luauodujoo jo jequja^^ liaqs

Component

Description

Arrange

components

ol

shell

members

in

order

ot

decreasing

SIR

tor

each

shell

member.

Order

ot

shell

members

is

optional.

8;u9uodujoo jaquje/^ liei^S D < O O a < o o o < a o o < m u o < ID O o

iQOl 9Jenb8 UI b9jv jaquja^ lldqs

9UJ6N J8quj9^ iie^S

jequjnr^ J9qijjg^ iie^s CM CO
(gp) |9Aen uoueiiJO qbioh

(gp) seojnos leujeixg oi OHQ punos Joopui

UlS ujoou

(gp) I9A9T punos

J0IJ91X3 IBIOI

(1-9 eiqBi luojj)

)U9U.I)Sn|pv I9A91

(gp) S|9A9n punos l)BJOJ!V PUB ^e«|!BU PUB

/^BMySlH IBlOi U99Ml9g 9DU9J9H!a

(gp) |9A9n punos

XBM|!By pUB AbMI|6!H |B;oi

(1-9 eiqBi uiojj) }U9UJlSn[pv |9A9n

(gp) S|9A9n punos <BM|!Bt| pUB ABMqBlH

U99M)9g 93U9Jg|lia

(S -dBijo) (gp) |9A9n gojnos
MfiS-114A (REV. 1 1-77)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBS ESS 84

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

DESIGN GUIDE for Reducing Transportation Noise

in and Around Buildings

5. Publication Date April 1978

6. Performing Organization Code

/. AuiHUK^a; David S. Pallett, Rooert wenrii, Koger u. js.i±iner,

and Thomas L. Quindry

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON D.C 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP) 13. Type of Report & Period

Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

Library of Congress Catalog Card Number: 76-58340

16. ABSTRACT (A 200-word or less factual summary of most si^ificant information. If document includes a significant

bibliogf^pfiy or literature survey, mention it here.)

This design guide presents a unified procedure for the selection of noise

criteria in and around buildings, for the prediction of exterior and

interior noise levels arising as a consequence of transportation systems

operations, and for the evaluation of the adequacy of building designs

with regard to environmental noise. Noise criteria levels are suggested

in terms of equivalent sound levels (Leq) . Simplified predictive methods

enable the estimation of noise levels arising as a consequence of highway,

railway, and aircraft operations. The sound isolation provided by the

building shell is estimated by means of a new single-figure rating system.

Finally, design manipulations which may make possible the improvement of

the acoustic conditions in and around buildings are suggested.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Acoustics; architectural acoustics; building acoustics; environmental noise;

noise; noise control; sound; transportation system noise.

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