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'' NBS TECHNICAL NOTE 1113-2
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act ot Congress on March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau's technical work is per- formed by the National Measurement Laboratory, the National Engineering Laboratory, and

the Institute for Computer Sciences and Technology.

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Absolute Physical Quantities^ — Radiation Research — Thermodynamics and

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provides engineering measurement traceability services; develops test methods and proposes

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and develops and improves mechanisms to transfer results of its research to the ultimate user. The Laboratory consists of the following centers:

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THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts

research and provides scientific and technical services to aid Federal agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and

economy in Government operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives; carries out this mission by managing the Federal Information Processing Standards Program, developing Federal ADP standards

guidelines, and managing Federal participation in ADP voluntary standardization activities; provides scientific and technological advisory services and assistance to Federal agencies; and

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The Institute consists of the following centers:

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'Headquarters and Laboratories at Gaithersburg, MD, unless otherwise noted; mailing address Washington, DC 20234. Some divisions within the center are located at Boulder, CO 80303.
TIOMAL BURBAD

Of STANPABDS

LDBRART SEP' i 9 1980

Highway Noise Criteria Study: ^J^^^

Outdoor/Indoor Noise Isolation .t ifi^

Paul R. Donavan*

Daniel R. Flynn

Simone L. Yaniv

National Engineering Laboratory

National Bureau of Standards

Washington, DC 20234

Sponsored by:

U.S. Department of Transportation

Federal Highway Administration

Office of Research, Environmental Design and Control Washington, DC 20585

*Current Address: General Motors Research Laboratories

12 Mile Road

Warren, Ml 48090

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U.S. DEPARTMENT OF COMMERCE, Philip M. Klutznick, Secretary

Luther H. Hodges, Jr., Deputy Secretary

Jordan J. Baruch, Assistant Secretary for Productivity, Technology and Innovation

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued August 1980
National Bureau of Standards Technical Note 1113-2

Nat. Bur. Stand. (U.S.), Tech. Note 1113-2, 180 pages (Aug. 1980) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1980

For sale by the Superintendent of Documents, U.S. Government Printing Office. Washington, B.C. 20402

Price $6. (Add 25 percent for other than U.S. mailing)
Abstract

This report documents a series of measurements of the outdoor-to-indoor

noise isolation provided by nine houses in the Washington, DC, area. These

measurements were carried out as part of a large research program developed to

identify and quantify the important physical parameters which affect human response

to time-varying traffic noise and to investigate various procedures for rating

such noise so as to enable reliable predictions of subjective response to the

noise. While a small truck was driven past each test house, simultaneous

recordings were made of the sound level at three outdoor microphones and at

four indoor microphones (three of which were positioned at representative

listener positions) . These recordings were analyzed to yield one-third octave

band sound levels as functions of time and from these levels outdoor-to-indoor

level differences were computed. Analyses are given of the influence of different

experimental variables. It is found that microphone placement, both indoors

and outdoors, is the major source of measurement uncertainty. The data from this

study are in good agreement with sound isolation data reported in the literature

for houses in colder climates.

Key words: Acoustics; building acoustics; environmental pollution; noise control;

noise isolation; sound.

iix
Table of Contents

Page

1. INTRODUCTION 1

2. MEASURES OF BUILDING SOUND ISOLATION . . 3

2.1 Definitions 3

2.2 Measurement Considerations for Outdoor and Indoor Sound

Fields 5

2.2.1 Measurement of Outdoor Sound Pressure Levels . . 5

2.2.2 Measurement of Indoor Sound Pressure Levels . . 7

3. MEASUREMENTS OF NOISE INTRUSION REDUCTION 9

3.1 Measurement Procedure 9

3.2 Measurement Sites 18

3.3 Data Reduction 18

4. AVERAGED VALUES OF NOISE INTRUSION REDUCTION 23

4.1 Average Noise Intrusion Reduction for Individual

Houses 23

4.1.1 Averaging Technique 23

4.1.2 Comparison of Average Values for Data Sets No. 1,

2, and 3 24

4.2 Average Noise Intrusion Reduction for All Nine Test

Houses 28

4.2.1 Averaging Technique 28

4.2.2 Values of Average Noise Intrusion Reduction ... 31

4.3 Comparison of the Average Noise Intrusion Reduction

to Published Values of Sound Isolation 34

5. DISCUSSION OF NOISE INTRUSION REDUCTION RESULTS 42

5.1 Dependence of NIR on Building Facade Parameters .... 42

5.1.1 Dependence on Presence of Storm Windows 42

5.1.2 Dependence on Window Area 44

5.1.3 Dependence on Facade Wall Composition 47

5.2 NIR with Windows or Doors Open 51

5.3 Dependence of NIR on Exterior Noise Source Position . . 51

5.3.1 Exterior Windows Closed 51

5.3.2 Exterior Windows Open 55

5.4 Variation Between NIR Values for Listener and

Interior Reference Microphone Positions 57

6. IMPLICATION OF RESULTS FOR MEASUREMENTS OF SOUND ISOLATION ... 62

6.1 Measurements of Exterior Sound Pressure Levels 62

6.1.1 Theoretical Considerations 62

6.1.2 Results of the Current Study 68

6.1.3 Implications for Sound Isolation Measurements . . 76

IV
Page

6.2 Measurement of Interior Sound Pressure Levels 79

6.2.1 Spatial Variation at Low Frequency 79

6.2.2 Spatial Variation at High Frequency 81

6.2.3 Magnitude of Interior Sound Pressure Levels 88

7. REFERENCES 92

APPENDIX A. FLOOR PLANS FOR THE NINE TEST HOUSES A-1

APPENDIX B. VALUES OF NOISE INTRUSION REDUCTION DETERMINED WITH

SIMULTANEOUSLY OCCURRING OUTDOOR AND INDOOR SOUND

PRESSURE LEVELS B-1

APPENDIX C. VALUES OF NOISE INTRUSION REDUCTION DETERMINED WITH

MAXIMUM OCCURRING OUTDOOR AND INDOOR SOUND PRESSURE LEVELS. C-1

APPENDIX D. VALUES OF NOISE INTRUSION REDUCTION DETERMINED FROM

OUTDOOR AND INDOOR l/3-OCTAVE BAND SOUND EXPOSURE

LEVELS D-1

APPENDIX E. ELECTRONIC FILTER SIMULATING AVERAGE NOISE INTRUSION

REDUCTION E-1

k
List of Figures

Page

Figure 1. Schematic diagram of data acquisition system . 10

Figure 2. Schematic diagram showing exterior and interior microphone

positions for a hypothetical house 11

Figure 3. Placement of interior microphones at Test House No . 9 .... 12

Figure 4. Placement of exterior microphones at Test House No . 9 .... 14

Figure 5. Passby of test vehicle at Test House No . 9 14

Figure 6. Interior of test vehicle showing placement of loudspeakers

used for supplemental pink noise 16

Figure 7. One-third octave band sound pressure level spectra as produced outdoors during a passby of the test vehicle with

and without supplemental pink noise 17

Figure 8, Noise Intrusion Reductions, for the three different data sets,

at Test House No. 6 2 5

Figure 9. Noise Intrusion Reductions, for the three different data

sets, at Test House No . 8 2 6

Figure 10. Range of Noise Intrusion Reduction values, for Data Set No. 1,

for five passbys of Test House No . 9 2 7

Figure 11. Range of Noise Intrusion Reduction values, for Data Set No. 2,

for five passbys of Test House No . 9 2 9

Figure 12. Range of Noise Intrusion Reduction Values, for Data Set No. 2,

for four passbys of Test House No . 2 30

Figure 13 • Noise Intrusion Reduction values averaged over all nine test

houses using three different averaging procedures 32

Figure 14. Average and range of Noise Intrusion Reduction values for all

nine test houses 3 3

Figure 15. Comparison of average octave-band Noise Intrusion Reduction

values from the present investigation with sound isolation

values reported in the literature for aircraft noise 35

Figure 16. Comparison of average octave-band Noise Intrusion Reduction

values from the present investigation with the average and

range of sound isolation values reported in the literature

for aircraft noise in the Boston and New York areas 36

VI
Page

Figure 17. Comparison of average Noise Intrusion Reduction values from

the present investigation with sound isolation values reported

in the literature for brick and wood siding houses at Wallops

Island, Virginia 37

Figure 18. Comparison of average octave-band Noise Intrusion Reduction

values from the present investigation with sound isolation

values reported in the literature for traffic noise 39

Figure 19. Comparison of average octave-band Noise Intrusion Reduction

values from the present investigation with the average and

t

range of sound isolation values reported in the literature

for New York State houses subjected to controlled loudspeaker

noise sources 41

Figure 20. Comparison of Noise Intrusion Reduction values averaged for

houses with and without storm windows 4 3

Figure 21. Comparison of Noise Intrusion Reduction values averaged for

houses with large and small frontal window areas 45

Figure 22. Comparison of Noise Intrusion Reduction values averaged for

houses with large and small total window areas 46

Figure 23. Comparison of Noise Intrusion Reduction values averaged for

houses with brick veneer and wood siding 48

Figure 24. Comparison of published sound transmission loss data for

exterior walls with brick veneer and wood siding 49

Figure 25. Comparison of Noise Intrusion Reduction values, averaged over listener positions, for Test Houses No. 7 (with brick veneer

and storm windows) and No. 8 (with wood siding and no storm

windows) 50

Figure 26. Comparison of Noise Intrusion Reduction values, averaged over listener positions, for Test House No. 2 with and without

windows open 52

Figure 27. Comparison of Noise Intrusion Reduction values, averaged over listener positions, for Test House No. 9 with and without

front door open 5 3

Figure 28. Comparison of Noise Intrusion Reduction Values, averaged over listener positions, at various times during the vehicle

passby as determined from simultaneously occurring exterior

and interior sound pressure levels at Test House No. 8 with

windows closed 54

vii
Figure 29. Comparison of Noise Intrusion Reduction Values, averaged over listener positions, at various times during the vehicle

passby as determined from simultaneously occurring exterior

and interior sound pressure levels at Test House No. 2 with

windows open 56

Figure 30. Mean, standard deviation, and range of differences between

Noise Intrusion Reduction values determined for individual

listener positions and those for interior reference

positions, for the set at all nine test houses , . . , 58

Figure 31. Frequency histograms of the differences between Noise

Intrusion Reduction values determined at individual listener

positions and at the interior reference position for all nine

test houses 60

Figure 32. Increase in 1/3-octave band sound pressure level due to

reflection from an infinite plane of real impedance with a sound absorption coefficient of 0.1 63

Figure 33. Measured ratio of reflected to incident mean-squared

pressures, averaged for frequencies corresponding to 250,

500, 1000, and 2000 Hz '..... 66

Figure 34. Spatial variation of 500-Hz octave band sound pressure level

due to reflection from a periodic, rectangular surface

protrusion . , ................... 67

Figure 35. One- third octave band sound pressure levels measured outside

Test House No. 2 at three microphone positions at the time of

maximum interior A-weighted level .... 69

Figure 36. Computed increase in 1/3-octave band sound pressure level due

to reflection from an idealized planar surface for microphone

positions located 4.5 cm and 3.0 m from the surface 70

Figure 37. One-third octave band sound pressure levels measured outside

Test House No. 5 at three microphone positions at the time of

maximum interior A-weighted level 72

Figure 38. Computed increase in 1/3-octave band sound pressure level due

to reflection from an idealized planar surface for microphone

position located 15 cm and 3.0 m from the surface 73

Figure 39. One-third octave band sound pressure levels measured outside

Test House No. 8 at three microphone positions at the time of

maximum interior A-weighted level 74

Figure 40. Computed increase in 1/3-octave band sound pressure level due

to reflection from an idealized planar surface for microphone

positions located 1.6 m and 3.0 m from the surface 75

viix
Page

Figure 41, Computed increase in 1/3-octave band sound pressure level due

to reflection from an idealized planar surface for microntone

positions located 2 cm, 2.0 m, and 3.0 m from the surface , , , 77

Figure 42. Noise Intrusion Reduction for the three listener positions

at Test House No. 5 with windows closed 80

Figure 43. Approximate average number of room modes in a 1/3-octave band

for Test House No. 5 82

Figure 44. Computed sound pressure level as a function of distance from

the source of noise in a hypothetical room (typical of those

in the present study) for three values of the directivity

factor, Q- 84

Figure 45. Noise Intrusion Reduction for the three listener positions at

Test House No. 2 with the windows open 86

Figure 46. Floor plan and listener position microphone locations for

Test House No. 2 87

Figure 47. Traffic noise equivalent sound level spectra as measured

outdoors and as estimated indoors from average Noise

Intrusion Reduction values for the nine test houses 89

Figure 48. Range of 1/3-octave band sound pressure levels of background

noise for the nine test houses compared with estioiated indoor

spectrum for exterior traffic noise 91

ix
List of Tables

Page

Table 1. Summary of test house parameters 19

Table 2. Summary of Noise Intrusion Reduction data set parameters ... 21

Table 3. Summary of cases analyzed for the three different data sets. . 22

Table 4. Mean, standard deviation, and extreme values of differences

between NIR values determined at individual listener positions

and at interior reference positions for all nine test houses . 59
1. Introduction

The measurements documented in this report were obtained as part of a larger research program [1] having the following main objectives:

o to identify and quantify important physical parameters which affect human

response to time-varying traffic noise associated with varying densities

of both free-flowing highway traffic and stop-and-go traffic;

o to investigate and compare various measures and computational procedures

for rating time-varying traffic noise and to investigate which method (or

methods) best predicts the subjective response of people to the noise from

various types of traffic situations;

o to develop, if necessary, improved procedures for rating time-varying

traffic noise in terms of measurable parameters of the noise; and

o to formulate procedures by which the most useful of the above rating

procedures may be related to other commonly used environmental noise

descriptors.

These objectives are to be achieved mainly through a series of psychoacoustic

experiments designed to measure human response to a variety of traffic noises.

Stimuli for these experiments will be selected from a library of audio recordings

of traffic noise which was also obtained as part of the overall program [2]

Since people are often exposed to traffic noise while indoors, the effects of

time-varying traffic noise on human response should be studied under conditions

of listeners located both indoors and outdoors. To simulate indoor listening

conditions, the traffic noises recorded in this program will be modified on

playback, using electrical filters, so as to sound approximately as they would

when transmitted from outside to inside a building.

In order to develop a filter which will simulate transmission of traffic

noise from outdoors to indoors, a series of measurements was conducted to determine

the sound isolation provided by residential building shells. For this purpose, a measure of sound isolation termed Noise Intrusion Reduction (NIR) was used (see

Section 2) . Values of NIR were determined using analog tape recordings of sound

pressure taken simultaneously indoors and outdoors at each of nine single-family

dwellings in the greater metropolitan Washington, D.C., area. These analog recordings were subsequently reduced to indoor and outdoor 1/3-octave band sound pressure

levels. These levels were then used to compute values of NIR. The NIR data obtained

in the current study are compared to outdoor-to-indoor sound isolation data reported

in the literature.

Figures in square brackets indicate the literature references in Section 7 of this report.
The data obtained in this study were used to examine general problems

that may arise in the measurement of building sound isolation. In particular, sources of error in measuring exterior and interior sound pressure levels,

for the purpose of determining building sound isolation, are examined.

The remainder of this report is divided into six sections. A discussion

of measures of building sound isolation is presented in Section 2. A

description of measurement procedures, sites, and data reduction techniques

used in the current study is provided in Section 3. The resulting NIR data are presented in Section 4. A discussion of the NIR values obtained in the

current study is presented in Section 5. Implications of the results of

the current study to measures of building sound isolation are discussed in

Section 6. Section 7 contains the literature references used throughout the

report. Appendices A through E include floor plans of houses included in

the measurements, the complete set of NIR values, and the electronic design

of two outdoor-to-indoor sound transmission filters.
2. Measures of Building Sound Isolation

The outdoor-to-indoor sound isolation of a building shell is a measure of

the degree of lack of acoustical connection between the outdoor and indoor

environments [3] . This sound isolation includes the attenuation of sound in

traveling from the source to the outside of the building, the sound insulation

provided by the elements of the building shell, and any attenuation occurring

as the sound propagates inside the building to the point of reception. Building

sound insulation is typically quantified by a measure of the sound transmission

loss of the building facade or facade elements.^

Several definitions of building sound isolation and insulation are in use

by different standards organizations. The International Organization for

Standardization (ISO) has issued a standard test procedure [4] for determining

the field sound transmission loss of building facades and facade elements.

The American Society for Testing and Materials (ASTM) is developing a similar

standard [5] . ASTM [3] defines outside-to-inside level reduction^ for an enclosure as a measure of the sound isolation properties of the building facade

and the receiving room. For the determination of both facade sound transmission

loss and outside-to-inside level reduction, microphone locations within the

test room are chosen to yield a spatial average (on a mean-square pressure

basis) sound pressure level over the volume of the room.

For the purposes of the current study, the reduction of outdoor noise

intrusion into the building was determined as it would be experienced by

listeners located indoors. Thus, microphone positions corresponding to

probable listener positions within the room were used rather than receiver

positions which might be used to determine the spatial average mean-square

sound pressure level over the volume of the room. Accordingly, a sound

isolation metric dubbed "Noise Intrusion Reduction" (NIR) has been defined.

2.1 Definitions

A measure of facade sound transmission loss is defined both by ASTM and

ISO in similar test procedures for the determination of building facade sound

insulation. In the ASTM proposed standard [5] , the sound transmission loss

of the facade element, when traffic noise (or similar natural source) is

incident on the facade, is defined by:

TL = L^ -<L2>+ 10 ^og^Q (S/A), (1)

Sound transmission loss is defined as the ratio, expressed on the decibel

scale, of the airborne sound power incident on the partition to the sound

power transmitted by the partition and radiated on the other side [3]

^Level reduction is defined as the decrease in sound pressure level, measured

at the location of the receiver, when a barrier or other sound -reducing element

is placed between the source and the receiver [3]
where L^ is the outdoor time-averaged sound pressure level, <^L_^ is the

time-averaged sound pressure level spatially averaged over the volume of the

receiving room, S is the area of the facade element, and A is the absorption

of the room as a function of frequency. Equation (1) corresponds to sound

incident over a large range of angles rather than from a single direction.

In the ISO standard [A], a "sound reduction index" (R ) is similarly defined.

Note that both the ISO and ASTM procedures require a measure of the spatially

averaged mean-square sound pressure over the volume of the receiving room.

As discussed above, outside-to-inside sound level reduction has been

defined by ASTM as a particular measure of building sound isolation. Level

reduction is defined by ASTM [6] by the expression:

LR = \ -<\y > (2)

where L and <^L^ are the same quantities as defined above. Equation (2)

has no terms to account for test partition size or receiving room absorption.

Such terms are omitted in LR as this quantity is not intended to be a measure

of the sound insulation of the facade, but rather is a measure of overall

sound isolation from outdoors to indoors.

In order to assess the reduction of the environmental noise intrusion as would be typically experienced by occupants of a building, a measure of sound

isolation is required which combines the effects of facade sound transmission

loss and the attenuation provided within the room. Further, to assess the

reduction of noise intrusion as experienced by occupants in the receiving

room, it is necessary to examine sound isolation at probable locations of room occupants rather than at positions chosen to yield the spatial average

sound pressure level in the room. For these two reasons, the expressions

defined in Eqs. (1) and (2) were not considered to be appropriate for the

purposes of the current study. Therefore, the Noise Intrusion Reduction (NIR) was defined as a measure of building sound isolation corresponding to probable

occupant locations within the test room. Noise Intrusion Reduction is defined

by the expression:

NIR = L^ - L^p , (3)

where L is the sound pressure level at a listener position, or averaged

over a number of listener positions, in the receiving room. As in the

expression for outdoor-to-indoor level reduction, Eq. (2) , no terms are presented in Eq. (3) to account for test partition size or receiving room

absorption. Omission of such terms is consistent with a measure of building

sound isolation which combines the overall isolation due to the facade

insulation and the attenuation within the receiving room.
p

A number of specific measures of building sound isolation have been

reported in the literature [7-19] . Generally, these measure are defined so as to correspond to Eqs. (1), (2), or (3).

2.2 Measurement Congiderations for Outdoor and Indoor Soimd Fields

Common to the determinations of all of the building sound isolation

quantities is the quantification of the exterior and interior sound fields.

Some of the problems and uncertainties in both of these sound pressure level

measurements are mentioned below. Additionally, the procedures used to measure exterior and interior sound pressure levels specified in the existing

proposed standards and in the literature are presented. (Some of the measurement

problems associated with such measurements have been examined by Mulholland [20]

and by Lewis [21].)

2.2.1 Measurement of Outdoor Sound Pressure Levels

2.2.1.1 Microphone Placement

Ideally, in order to determine building sound isolation, it would be

desirable to measure the outdoor sound pressure level at the building site

with the building not present. However, as this is not typically possible,

the measurement of the outdoor sound field must be made in the presence of

reflecting surfaces introduced by the building, in addition to the existing

ground plane. The presence of building surfaces complicates the measurement

of the outdoor sound field because the reflected sound interferes with the

direct sound from the noise source, thereby creating spatial and temporal

variations in the sound field relative to those that would exist in the

absence of the building. Characterization of the influence of the reflected

sound is complicated due to the finite (and possibly complex) impedance of

the building surface and ground cover and to irregularities in the surface

created by facade structures such as window and door recesses.

For measurement of outdoor sound pressure levels in conjunction with the

ISO [4] and the proposed ASTM [5] standards, it is stated that the microphone

is to be placed 2 m from the building surface. As an alternative, in the ISO

standard a microphone distance of less than 2 cm may be used.

In the literature several additional microphone positions relative to the

building facade have been used to measure outdoor sound pressure levels. In a number of studies, a microphone distance of 1 m has been used. In one study,

the microphone was placed 4.5 cm from the building surface, corresponding to

the radius of a microphone windscreen [7] . Many of the reported studies do

not include information on microphone placement or supply vague information

such as "away" from or "several feet" from the building.

As an alternative to measuring the existing sound field outside a building

with a microphone placed in the vicinity of the building surface, both the

ISO and ASTM procedures allow the use of a controlled loudspeaker noise

source to infer the exterior sound pressure level. Using this technique.
the sound level produced at the test facade by a loudspeaker is inferred

from an earlier measurement of the level produced by the loudspeaker. This

is determined by measuring the level produced at a corresponding location

relative to the loudspeaker when the loudspeaker is installed in an environment

similar to that in which the test is to be made, but with no vertical building

surface present. The electrical input corresponding to the measured sound

level is then set and is maintained during the actual facade test. In this

manner, the level of the incident sound is known, uncomplicated by reflection

from the test facade.

2.2.1.2 Position of Exterior Sources of Noise

In addition to the positioning of the microphone relative to the exterior

building surface, the angle of incidence of the exterior sound will affect

measured values of sound isolation because of the angular dependence of

the sound transmission loss of facade elements. For infinitely large panels,

the dependence of sound transmission loss on incidence angle can be demonstrated

theoretically [22,23]. Although this model may not be representative of actual

building facades, the angular dependence of sound transmission loss for windows

has been demonstrated both theoretically and experimentally [23-25] . Because

of such angular dependencies, the position of the exterior source of noise

relative to the test facade is of importance in characterizing building sound

isolation properties.

The position of the exterior source of noise is specified in a similar

manner in both the ISO and proposed ASTM standards for the measurement of

facade sound transmission loss. If the building facade to be assessed is

exposed to traffic noise, both of the standards recommend using the timeaveraged sound pressure level measured 2 m from the building facade as the

exterior level in Eq. (2). Typically, this measurement provides some averaging over incident angle for the exterior sounds as well as providing

some characterization of the sound transmission loss of the facade for the

environmental noise sources to which it is normally exposed. If a controlled

loudspeaker noise source is used to determine sound insulation, both test

methods require an incidence angle of 45 from normal with other angles

being included as options.

The position of the noise source relative to the test structure is often

dictated by the intent of the outdoor-to-indoor sound isolation measurement.

In the literature, numerous studies have used aircraft overflights as the

noise source. This was done because the intent was to determine the effectiveness of the test structure in reducing aircraft noise. In most of

these studies, the position of the source relative to the structure is not

well known. In some cases, there is no one defined source position. This occurs because reported noise reduction values correspond to the difference

between the maximum exterior level and the maximum interior level regardless of

when either occurred during the overflight [9,17,19]. In one recent study,

the intent of the measurement was to assess the performance of dwellings
in reducing noise from electrical transmission lines [15] . Due to the

(spatially) linear nature of the source in this case, loudspeaker noise

sources were placed outside the building in a line parallel to the building

surface.

\-

' The position of the exterior noise source is also important in sound

isolation determinations due to multiple sound transmission paths in the

structure. For most surface transportation noise sources, sound is transmitted

primarily through windows and doors and to a lesser extent through the wall

structure itself [26] . However, if the noise source is elevated, other

transmission paths, including roof-ceiling systems and chimney flues, may

become significant [11,26]. The occurrence of such multiple transmission

paths further complicates the measurement of the exterior sound field when the

multiple transmission paths are spatially distributed over the test structure.

In this case, microphone placement should be such as to characterize adequately

the sound incident on each element contributing to the sound transmission.

2.2.2 Measurement of Indoor Sound Pressure Levels

The measurement procedures used to characterize the indoor sound field are dependent on the type of sound isolation measurement to be made. If the

sound transmission loss of the facade or the outdoor-to-indoor level reduction

as defined by Eq. (2) is to be determined, an estimation of the spatially

averaged (on a mean-square pressure basis) sound pressure level within the

receiving room is necessary. If the reduction of outdoor environmental noise

exposure produced within a room by the building shell is to be determined for

occupants of that room, an estimation of sound levels occurring at probable

listener locations within the room is necessary. For either of these purposes,

significant variations in sound pressure levels measured at different discrete

points within the receiving room may occur.

Spatial variation of measured indoor sound pressure levels, particularly

for living spaces, can occur for a variety of reasons. At low frequencies,

the principal reason is wave phenomena within the enclosed space of the

receiving room, resulting in local variations in sound pressure level [22]

Spatial variations can occur due to the finite size of the radiating surfaces

(e.g. windows and walls) within the room, multiple transmission paths through

the building shells, the presence of furnishings within the receiving room,

and the position and temporal characteristics of the exterior sound source. For many living spaces, spatial variations are further complicated by the

typical sound absorptive nature of such spaces. Furnishings (e.g., chairs,

sofas, carpeting, drapes) within the receiving room can act both to increase

spatial variation by providing localized absorption and shielding of sound

and to decrease spatial variation by providing localized scattering of sound

and by increasing modal bandwidths for the room acoustic resonances.
Procedures for the determination of the spatially averaged sound

pressure level within the receiving room are not explicitly provided in

the ISO and the proposed ASTM standards. In the ISO standard [4], the

location and number of interior measurement points to be used to determine

the average interior mean-squared pressure are not specified. However, in an example cited in the standard, six randomly distributed microphone positions

are used with no position nearer than 0.5 m from a room boundary or nearer than 1 m from the exterior wall under test. Similarly, in the proposed

ASTM standard, measurement points are not specified other than the requirement that none be within 1 m of the exterior wall [5]. The ASTM proposed

procedure allows the use of a single microphone position at the approximate

center of the room if preliminary measurements indicate that the level at

this one position approximates the room average.

In the studies reported in the literature, the uncertainties in the

estimation of spatially averaged sound pressure level within the receiving room are not well addressed. In a number of previous studies, the level

corresponding to a single microphone position in the center of the room was

used as an estimate of the spatial average sound pressure level [8,10,11].

Also cited in previous studies is the use of one or more microphones placed

along a diagonal of the receiving room at a point one-third of the length of

the diagonal away from a corner of the room [7,12]. Although this microphone

position has been advocated in the literature [16] , data relating sound

pressure levels measured at these points to the level that would be obtained

from a comprehensive spatial average of mean-square sound pressure are not

available.

Interior microphone positions used in measurements made to assess interior noise exposure are not well documented in the literature. In many

studies, the location of the interior microphone is not specified at all. In one recent study [15], two microphone positions were used, one at the geometric

center of the room, and one at a typical listener location such as an armchair

or near the head of a bed; however only the averages of these two interior

levels are reported.
3. Measurements of Noise Intrusion Reduction

As discussed in Sec. 1, the purpose of the outdoor-to-indoor sound

isolation measurements in this study was to determine how outdoor traffic

noises are modified when heard by indoor listeners. In order to achieve this

specialized purpose. Noise Intrusion Reduction (NIR) was defined in Sec. 2.1

and measurement and analysis procedures were developed which varied from

other procedures used in measuring building sound isolation in several

ways, including choice of noise source, outdoor microphone placement, indoor

microphone placement, and data reduction. The procedures used to determine

NIR are presented in the remainder of this section.

3.1 Measurement Procedtire

In order to determine Noise Intrusion Reduction, simultaneous magnetic

tape recordings were made of sound pressure outside and inside each test house

during a vehicle passby. The instrumentation used to acquire the simultaneous

recordings is illustrated in Fig. 1.-^ Sound pressures were recorded using

seven microphones, corresponding to three positions outdoors and four indoors.

The signal on each of the seveh channels was amplified and monitored to

maximize the usage of the dynamic range of the FM magnetic tape recorder.

The positioning of the seven microphones relative to a hypothetical house

is illustrated in Fig. 2. Of the four interior microphones, one was always

positioned 1.0 meter from a window which faced the street upon which the

vehicle passby occurred. This reference microphone was adjusted to be 1.2

meters above the floor. As it was intended to characterize sound isolation,

as it relates to the noise exposure of listeners, the remaining three microphones were placed above seating positions throughout the room. These seating

positions corresponded to the existing position of furniture (i.e., sofas and

chairs) in the receiving room. Each microphone was centered above the seat of

a particular piece of furniture and adjusted to be 1.0 meter above the floor,

approximating typical ear height for seated listeners. The interior of Test

House No. 9 is illustrated in Fig. 3.

^ Commercial instruments are identified in this report in order to specify

adequately the experimental procedure. In no case does such identification

imply recommendation or endorsement by the National Bureau of Standards, nor does it imply that the equipment identified is necessarily the best available

for the purpose.
3 B&K MODEL 4165 '/j" MICROPHONES

3 B&K MODEL 2619 ^ ^^^ MODEL 2804

PREAMPLIFIERS 2 CHANNEL POWER SUPPLIES

== CZI

C3

4 B&K MODEL 4165

Vi" MICROPHONES

4 B&K MODEL 2619

PREAMPLIFIERS

2 B&K MODEL 2804

2 CHANNEL POWER

SUPPLIES

TIME CODE

GENERATOR

EXTERIOR

INTERIOR

MULTI-CHANNEL

AMPLIFIER

HONEYWELL

14 CHANNEL

FM TAPE RECORDER

Figure 1. Schematic diagram of data acquisition system.

10
p

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TOWARD

ROADWAY

3m

REFERENCE INTERIOR

MIKE POSITION

!£ 31!^

^

INTERIOR LISTENER

MIKE POSITIONS

NOTE: Exterior mikes

at same height as interior

listener position mikes

NOTE: Interior reference mike

centered on window, 1.2m above floor. Listener position mike centered on seating positions at nominal ear height

Figure 2. Schematic diagram showing exterior and interior microphone

positions for a hypothetical house.

11
A\l

1

Ilk .MIK^' -

\ %"««' __' -.^H^H^^ '*' ' p.^ -„_

A '^

Figure 3. Placement of interior microphones at Test House No. 9,

12
Of the three outdoor microphones, two were positioned at a distance of

3.0 meters from the front facade of the house. The 3-m distance was selected

to minimize variations in the measured sound levels, due to the presence of

the reflecting plane of the building, for the frequency range from 50 to

4,000 Hz (see also Sec. 6.1). Two microphones were used at the 3-m distance

to avoid reliance on a single microphone channel and to obtain some indication

of the spatial variation of the exterior sound field.

The 3-m microphones were separated by a distance of 1.8 meter. This

separation was selected to be greater than an acoustic wavelength for

frequencies above 250 Hz where spatial variation is expected to be most

pronounced. The separation was also selected to be on the order of the

dimension over which irregularities in the building surface are likely to occur. The third outdoor microphone was positioned within 4.5 cm of the

building facade for most of the test houses. This distance is the closest

that the microphone could be placed to the facade as the microphone windscreen

used had a radius of 4.5 cm. (For comparison to measurements at the 4.5 cm position, at two of the test houses distances of 15 cm and 160 cm were used)

The purpose of this third exterior microphone was to provide data which could

be compared to those obtained at 3 m to afford evaluation of the effect of

microphone placement relative to an exterior building surface. All three

outdoor microphones were adjusted in height to be approximately level with the

interior listener position microphones. The placement of the three exterior

microphones is illustrated in Fig. 4 for the test house shown in Fig. 3.

As the overall purpose of the program is to evaluate human response to

traffic noise, the noise of vehicular passbys was chosen as the exterior noise

source. It was further decided not to use local traffic in the vicinity of

potential measurement sites, but rather to generate the exterior sound field

with a passby of an NBS truck. This method was preferred because in those

situations where there was sufficient local traffic to provide suitable interior

sound levels, the background noise level in the house in the absence of vehicular

noise could not be determined due to the continually-present traffic noise.

The vehicle used as a noise source is shown in Fig. 5 as it was driven

by Test House No. 9. The vehicle was an International Harvester step-van

with a V-8 engine, 4-speed manual transmission, and a maximum gross vehicle

weight of 10,000 lbs. This vehicle had dual rear wheels with mud and snow

tires and single front wheels with rib tires. For all the test houses except

No. 1, the truck was driven past the house from left to right as viewed from

the front of the house. For House No. 1, the passby was from right to left.

In all cases, the vehicle was driven as close as possible to the edge of the

roadway nearest the house.

For the nominally 48 km/hr (30 mph) passbys that were used, it was found

that the truck alone produced sufficient noise in the frequency range from

50 to 1000 Hz to be measurable inside houses. However, above 1000 Hz,

r

13
Figure 4, Placement of exterior microphones at Test House No. 9

Figure 5. Passby of test vehicle at Test House No. 9,

14
where buildings provide more sound isolation, the passby noise of the vehicle

alone produced insufficient signal to be measured adequately indoors. To

remedy this situation, the high frequency portion of the truck spectrum was supplemented with "pink noise" broadcast through loudspeakers. The loudspeakers were placed on the van step on the opposite side of the vehicle from the driver

position. At this position, the loudspeakers were approximately 0.75 m above

the roadway. The position of these loudspeakers on the truck is pictured in

Fig. 6. The effect of the supplemental pink noise on the 1/3-octave band

spectrum of the truck as recorded outdoors is illustrated in Fig. 7 for a passby at Test House No. 9. With the addition of the supplemental pink noise,

sufficient interior signal was obtained to determine the Noise Intrusion

Reduction over the frequency range from 50 to 4,000 Hz for all of the test

houses.

Prior to the recording of passby sound levels at each of the nine test

houses, calibration signals were recorded for each of the seven data acquisition microphones, using a Briiel and Kjaer (B & K) Type 4220 Pistonphone,

producing 124 dB , re 20 yPa, at 250 Hz, for a minimum of 10 seconds after the

signal stabilized. After calibration, B & K Type 0237 windscreens were placed on the three exterior microphones.

To minimize the intrusion of environmental noise events other than the

truck passby, two-way radio communication was maintained between the recording

team and the driver. In this manner, the truck passbys were coordinated with

data acquisition so that data were only obtained during the passbys. At least

five truck passbys were recorded at each house with all exterior windows and

doors closed. Three additional passbys were conducted with either several

windows or an exterior door open. During the course of the recordings, an ambient noise recording was also made on all seven microphone channels in the

absence of the truck and of any observable environmental noise source.

For all the recordings at each of the houses, the wind speed was less

than 4 m/sec. The outdoor temperature ranged from 18 to 30 C. In all cases,

the roadway surface was dry.

At each of the test houses, supplemental physical data regarding the test

house and room were obtained. Photographs were taken to indicate the

positioning of the four interior microphones relative to the room and

furniture. These photographs were also intended to afford information

regarding furnishings in the room and their orientations. In addition to

photographs, a sketch of the room floor plan was drawn and room dimensions

noted (see Appendix A) . The location, dimension, and type of exterior doors

and windows were noted. Photographs were taken of the exterior of the house

to indicate the positioning of the exterior microphones and to provide overall

orientation of the street and house. The distance from the front of each

house to the near edge of the roadway was measured and noted. Only a few

sample photographs have been included in this report.

15
Figure 6. Interior of test vehicle showing placement of loudspeakers

used for supplemental pink noise.

16
90 1—

00

a. 80 -

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LU

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50 -

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Vehicle spectrum w/

supplemental pink noise

Vehicle spectrum w/o

supplemental pink noise

J L J L J L J_L I I I I 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz]

Figure 7. One-third octave band sound pressure level spectra as produced outdoors during a passby of the test vehicle

with and without supplemental pink noise.

I

17
3.2 Measurement Sites

Recordings of outdoor and indoor sound levels were made at nine different

single-family houses in the metropolitan Washington, D.C. area. These houses were selected to include several samples of two common construction types,

wood frame and frame with brick veneer. For each type of construction, other

parameters were varied, such as window type, distance to roadway, presence of

exterior doors, and amount of brick facing. The parameters characterizing

the nine houses are summarized in Table 1. With the large number of possible

combinations of construction variables, not all parameters could be varied

independently over the sample set of nine houses. From Table 1, it will be

noted that three all-frame houses, five frame houses with brick veneer, and one frame house with stone veneer were tested. Of the brick veneer houses,

three had brick veneer all around the house up to the top of the windows, one

had brick only to the front (facing the roadway) of the house, and one had

brick veneer over the entire exterior surface. For both all-frame and brick

veneer construction types, houses with and without storm windows were tested.

In the set of test houses, storm windows were not in place on four houses and were in place on four houses. The remaining house had storm windows on all

windows except on one large, fixed window. This house is referred to as having "partial" storm windows. The set of houses also included two houses

with exterior doors to the side of the house and two with no exterior doors in

the test room. All of the houses tested had windows facing the roadway with

five also having windows to the side of the house. In all cases, the test room was either a living room or living/dining room combination. The floor

plans of the test rooms for the nine houses are given in Appendix A.

3.3 Data Reduction

The exterior and interior analog sound pressure recordings for each of

the nine test houses were reduced to 1/3-octave band sound pressure levels

using three different processing methods. The first method was designed to

produce 1/3-octave band sound pressure level time histories for the individual

vehicle passbys for each of the microphone positions. This reduction was accomplished by playing the tape recordings back into a General Radio Model

1921 real-time 1/3-octave band analyzer. This analyzer utilizes "true"

integration, i.e., levels corresponding to the average mean-square sound

pressure over a specified integration time are obtained. For the purposes of

this study, an integration time of 0.2 seconds was used. The resultant sound

level time histories were printed and simultaneously recorded digitally on magnetic tape under computer control.

The second method of obtaining 1/3-octave band sound pressure levels from

the recorded pressure signals was designed to obtain the maximum sound pressure

level occurring in each 1/3-octave band during an individual vehicle passby

for each of the microphone positions. This reduction was accomplished using

a B & K Type 2131 Digital Frequency Analyzer. Using the "max hold" feature

of the analyzer, the maximum (1.0 second time constant) level occurring in

each 1/3-octave band was detected and held. The resultant maximum levels were printed on a teletype controlled by the analyzer.

18
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19
The B & K analyzer was also used for the third method of data reduction.

For this method, the average 1/3-octave band levels were obtained by averaging

the squared sound pressure over an 8.0 second interval. The 8.0 second time

interval was found to be sufficiently long to include all of the A-weighted

sound levels occurring between the 10-dB-down points of the passby at all of

the microphone positions. The average level occurring in the 8.0 second time

interval was then used to compute the sound exposure level-"^ (SEL) of the

passby at each microphone position.

Prior to calculating NIR values from the 1/3-octave band sound pressure

level data, the mean-square pressures obtained at the two exterior 3-m

microphones were averaged. This was done to minimize the uncertainty due to

spatial variation of the measured sound pressure levels for these two microphone positions. Further discussion of the variation observed between the

two 3-m microphone positions is provided in Section 5. Other than averaging

the data for the two 3-m microphone positions, no corrections were applied

to exterior data to compensate for the presence of the building surface. Also, no correction was applied for spherical divergence between the microphone

position and building surface because the difference in level due to this

phenomenon is approximately frequency independent.

After averaging the 1/3-octave band pressure levels obtained from the

two 3-m exterior microphones, NIR values were calculated by subtracting the

interior 1/3-octave band sound pressure levels measured at each of the four

microphone positions from the corresponding average exterior level at 3 m. This calculation was performed on the data obtained using the three reduction

techniques discussed above, thus forming three distinct data sets. The

characteristics of these three data sets are summarized in Table 2.

Data Set No. 1 was formed using simultaneously occurring exterior and

interior levels corresponding to the time at which the interior A-weighted

level was at a maximum at the interior reference microphone position. This

time in the passby was chosen to optimize the signal-to-noise ratio as measured indoors. Such optimization was necessary since it was found that

for some houses with either particularly good isolation properties or with

large distances between the house and roadway, measurable sound pressure

levels in each of the 1/3-octave bands were generated indoors only for a very

short time near the time of the maximum interior A-weighted sound level. At

the time of maximum interior A-weighted sound level, there was sufficient

signal-to-noise ratio in all 1/3-octave bands to avoid background noise

corrections for all test houses except Nos . 1 and 3. In House No. 3, which

was 61 m from the roadway, sufficient signal was not present at the time

of maximum interior A-weighted sound level to allow computation of Noise

Intrusion Reduction in the 1/3-octave bands centered from 315 to 800 Hz, even with corrections for background noise.

Sound exposure level is defined as

^'T SEL = 10 log'10 kf. 1°""°"'

where T is the duration of the event in seconds, L is the 1/3-octave band

or the A-weighted sound pressure level, re 20yPa, as a function of time,

and t 5 1.0 second is a reference time [2]. o

20
Table 2. Summary of Noise

Intrusion Reduction data set

parameters

Data Set

No.

Averaging

Time

(s)

Sample Used in

NIR Calculation

1

2

3

0.2

1.0

8.0

1/3-octave band data at time of

maximum interior A-weighted sound

level

Maximum 1/3-octave band (indoor

and outdoor) sound pressure level

regardless of time of occurrence

Approximate sound exposure level

(indoor and outdoor) in each 1/3-

octave band

Data Set No. 2 was formed using the maximum level occurring in each

1/3-octave band for each microphone position during the passby, regardless

of when the maximum occurred. For this type of data reduction, sufficient

signal-to-noise ratio was obtained in all 1/3-octave bands to avoid any

need for correction for background noise, except for Test House No. 1.

Data Set No. 3 was formed using the 1/3-octave band sound exposure levels

determined for the individual exterior and interior microphone positions

for passbys of Houses No. 6 and No. 8. This calculation was only done for

these two houses since the other seven houses did not provide sufficient

signal-to-noise ratio in 1/3-octave bands over the 8.0 second time interval.

The numbers of passbys for which NIR values were calculated for each

Data Set are summarized in Table 3. The results of these calculations are

presented in Appendices B, C, and D and discussed in Sections 4 and 5. For

Data Set No. 1, 1/3-octave band NIR values were calculated for House No. 8

at different instances during the passby using the 1/3-octave band time

history data. These additional instances in time were at 2.8 and 1.4 seconds

before the maximum interior A-weighted level and at 1.4 and 2.8 seconds after

the maximum.

21
Table 3. Summary of cases analyzed for the three different data sets.

Test House Windows

and

Doors

Number of Passbys Analyzed

Data Set No. 1 Data Set No. 2 Data Set No. 3

Both closed

Both closed

Windows open

Both closed

Both closed

Both closed

Both closed

Both closed

Both closed

Both closed

Door open

1

1

1

1

1

1

1

1^/

5

1

a/ — NIR values were also calculated for different instances during the passby

(see text)

22
4. Average Values of Noise Intrusion Reduction

In order to use the results presented in Appendices B, C, and D to

develop a filter shape corresponding to the "typical" modification of outdoor

traffic noise spectra as received by listeners located indoors, some method

must be used to combine the results for individual microphone positions at the

nine different houses. For the purposes of the current study, this combination

was performed by first determining the spatial average Noise Intrusion Reduction

(NIR) values for each house individually. Using these spatial average values,

average NIR values for the set of nine houses were calculated. Discussion of

several averaging techniques and values resulting from the averaging is presented

in this section. Also included in this section is a comparison of the average

values obtained in the current study with noise isolation data reported in the

literature.

4.1 Average Noise Intoision Reduction for Individual Houses

4.1.1 Averaging Technique

For each of the individual test houses and for each of the data sets of

Table 2 it was desired to combine the NIR values determined for the three

interior listener position microphones into one set of 1/3-octave band NIR

values representing each house. These spatially averaged values are of

particular concern because significant variation in NIR values among the three

interior listener positions in individual houses was observed. Variation was most pronounced in the lower 1/3-octave bands, with variations in some cases of

more than 10 dB in the 1/3-octave bands centered from 63 to 200 Hz. Above

800 Hz, variations of up to about 5 dB were found to occur. Spatial variations

are further examined in Sec. 6.2.

Combination of the NIR values for individual houses could be performed

using any of several methods. One possible method of spatially combining

values is to represent the house by the lowest values of NIR, thus representing the most severe noise exposure case. These lowest values might be

those obtained from some determined "worst" case microphone or those obtained

on a 1/3-octave band basis using the worst case of any of the three positions.

A second possible method of consolidation is to perform some type of averaging

of the three sets of values.

For the purposes of current study, it was decided to compute an NIR

corresponding to the values that would be obtained by subtracting the average

level (based on averaging the squared sound pressures) of the three interior

listener microphone positions from the average level of the two 3-m exterior

microphone positions:

r , / L /lo L ^/io\"|

\

/lO ^'^ + 10 ^'2 jI NIR = 10 £og

/lO U JlO L^ ^/lO

- 10 Jiog -r r, / L /lO L, -/lO L /lO V -1 U f 10 ^'1 + 10 ^'2 + 10 ^'^

I

(A)

23
where L. is the exterior sound pressure level at microphone position m and

L, is the interior sound pressure level for the microphone at listener

position n, This method of representing the average Noise Intrusion Reduction

for each house was selected because the averaging represented in Eq. (4)

corresponds to that specified in the ISO and proposed ASTM standards for sound

insulation measurements [4,5] and also is the same as that used in a recent

study of "dwelling attenuation" for purposes of assessing occupant exposure

to exterior transmission line noise [15]

From Eq. (4), NIR values averaged over the three interior listener

positions were calculated and are presented in Appendices B, C, and D for

each of the nine test houses and passby cases for which individual microphone

data are reported.

4.1.2 Comparison of Average Values for Data Sets No. 1, 2, and 3

Prior to combining the results of measured noise reduction into a single

outdoor-to-indoor filter shape, several aspects of the individual house

average values should be considered. One of these is the relationships among

average NIR values determined for the three data sets of Table 2. The averages

corresponding to these three values of NIR are plotted in Fig. 8 for one passby at House No. 6. For the case shown in this figure, there are only slight

differences between the values corresponding to Data Sets No. 2 and No. 3.

These differences are typically about 1 dB and always less than 2 dB . The values

for Data Set No. 1 vary from those of the other two data sets. For some 1/3-

octave bands, the difference between values from Data Set No. 1 and the other

two sets is as much as 7 to 8 dB, with typical differences of 2 to 3 dB at

the higher frequencies. Averages corresponding to the three types of NIR

values are plotted in Fig. 9 for House No . 8 . As in the previous case, the

differences between the values of Data Set No. 2 and Data Set No. 3 are uniformly small, at most 2 dB , and the difference between the values of Data

Set No. 1 and the other two sets is more pronounced, being as much as 5 to 6

dB for some 1/3-octave bands.

Departures of the values for Data Set No. 1 from the values for Data Set

No. 3 are expected for two reasons. First, Data Set No. 3 corresponds to an average over the varying incidence angle of the exterior sound. Second, the

measurement uncertainty in the lower 1/3-octave bands is greater for the simultaneous levels of Data Set No. 1.

The variation from one passby to another of the NIR values obtained for

Data Sets No. 1 and No. 2 was also examined. For House No. 9, five consecutive

vehicle passbys were reduced to average NIR values for both Data Sets No. 1

and No. 2. The range of 1/3-octave band average NIR values resulting from the

five individual passbys of Test House No. 9 for Data Set No. 1 is shown in

Fig. 10. From this figure, it is seen that, from run-to-run, values in individual

1/3-octave bands typically range over about 5 dB . Below 400 Hz, this range

24
00

CO

00

50

40

30

20

S 10

1—I—I—

"I—I—

1—I—I—I—

1—1—I—

J L I I I I I I I I I

I

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY [Hz]

Figure 8. Noise Intrusion Reductions, for the three different data

sets, at Test House No. 6.

Data Set No. 1. Computed from simultaneous 1/3-octave band

levels at the time of maxim.um interior

A-weighted level.

Data Set No, 2. Computed from the maximum 1/3-octave band

levels, regardless of when they occurred.

Data Set No. 3. Computed from 1/3-octave band sound exposure

levels.

25
00

50

40

o

t—

CO

E 30

oo 20 -

g 10

1 1

1

1 1 11 1 I'M'' 1

' '

-aV

* Data set

#1

- _A/^ • #2

A #3

1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz)

Figure 9. Noise Intrusion Reductions, for the three different

data sets, at Test House No. 8. (The three data

sets are defined in the text and in the caption

for Fig. 8.)

26
50 1—I—i—

-i—I—I—I—I—I—I—

1

\—I—I—I—I—

S 40

o

»—C3

o

30

20

S 10

J I I I I I I L J I I I I I I I I l__L

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz)

Figure 10. Range of Noise Intrusion Reduction values, for Data Set

No. 1, for five passbys of Test House No. 9.

27
increases to as much as 6 to 7 dB. For comparison, the range resulting

from the same five passbys of Test House No. 9 determined using the differences

in maximum level (for Data Set No. 2) is provided in Fig. 11. From this figure

it is seen that the range from run to run using the data reduction technique of

Data Set No. 2 is less than 2 dB above 250 Hz and at most 5 dB below 250 Hz.

Since Data Sets No. 2 and 3 are practically identical (see Figs. 8 and 9), the

range is similarly small for Data Set No. 3. The range resulting from the

four passbys of Test House No. 2 is shown in Fig. 12. Above 160 Hz, the

range is less than 3 dB for all bands. At and below 160 Hz, the range varies

from 1.5 dB at 63 Hz to 7 dB at 125 Hz. For comparison, for Test House No. 9,

above 125 Hz the range was less than 3 dB while at and below 125 Hz it varied

from 2 dB at 50 Hz to 5 dB at 100 Hz.

The results presented in Figs. 8 and 9 can be used to compare more

generally the three data reduction techniques. The use of spatially averaged

NIR values obtained from sound exposure levels to determine the house attenuation "filter" shape would have the advantage of averaging over incidence angles

for the exterior sound field and would be directly relatable to the commonly

used average (equivalent) sound level. Also, because the SEL-related values

of NIR correspond to average sound level, the use of this data reduction

technique is consistent with the ISO and proposed ASTM standards [4,5]. However,

as discussed previously, sufficient signal-to-noise ratio to determine the SEL

data in most of the test houses could not be maintained, even with supplemental

pink noise, for the duration of the passby. It is anticipated that such signalto-noise limitations would occur in many cases where vehicular noise sources are used unless exceptionally loud or close vehicles are present or the test

house has quite poor sound isolation.

In the further combination of the NIR values to obtain a single filter

shape, only those values corresponding to the difference in maximum level

(Data Set No. 2) were used. These values are used because of their agreement

with the Data Set No. 3 values obtained for two of the test houses, their run- to-run consistency, and their maximization of signal-to-noise ratio. The

values of Data Set No. 2 display quite close agreement to the values of Data

Set No. 3 because the largest contribution to the SEL in any one band occurs when the level in that band is at its maximum value. In addition to the

close correspondence to the SEL-related NIR values, the maximum level values

of Data Set No. 2 also have the advantage of providing the greatest signalto-noise ratio of the three data reduction methods.

4.2 Average Noise Intrusion Reduction for All Nine Test Houses

4.2.1 Averaging Technique

To combine further the average NIR values of Data Set No. 2 so as to

obtain an appropriate average NIR for the set of nine test houses, it was necessary to select a method for averaging these nine sets of values. To

perform such an average, three methods were considered, corresponding to

the following equations:

28
50

40

CQ

-ao

E 30

ULl o

CO

20 -

5 10

1

\—I—I

\—I—I—I—I—I—I—I

\—I—I—I—I—I—I—I—I—I—

J I I I I I l_J I I \ I \ I I I I I I L 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hzj

Figure 11. Range of Noise Intrusion Reduction values, for Data Set

No. 2, for five passbys of Test House No. 9.

29
QO

50

40

30

S 20

cc

% 10

T I r 1—I—I—I—I—1—I—I—I—I—

r

1—I—I—

r

I ' I 'I I 'I I I I I I

I I i__i I I I I I L 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz)

Figure 12. Range of Noise Intrusion Reduction Values, for Data Set

No. 2, for four passbys of Test House No. 2.

30
NIR = - (nIRi + NIR2 + ... + NIR ] , (5)

r 1 / NIRi/10 NIR2/IO NIR /10\1

NIR = 10 £og - f 10 +10 + ... + 10 '^ yj , (6)

and

NIR = -10 log

r. I -NIR./IO -NIR2/IO -NIR /10\1 Mio + + ... + 10 ^

yj. (7)

where NIR. is the value for the i-th house. These three equations correspond

to different interpretations of the average values obtained.

Equation (5) is simply the arithmetic average of the NIR values. Equation

(6) corresponds in concept to adjusting the exterior noise source for each

house to a level which produces a specified (constant) level inside each of

the houses, computing the resultant average exterior sound pressure levels,

and subtracting the fixed interior level from the average exterior level.

Equation (7) corresponds in concept to exposing the houses to a specified

(constant) exterior noise environment, computing the resultant interior

sound levels at all houses, averaging the interior mean-square sound pressure

levels, and subtracting this average interior level from the specified exterior

sound level to produce the "average" NIR.

Although the three averaging techniques discussed above are conceptually

distinct, when applied to the NIR values for the nine test houses only minimal

differences among the resultant average values were found. The average

values for the nine test houses using each of the three methods are presented

in Fig. 13. From this figure it is seen that Eq. (6) yields averages that are

consistently higher than those from Eq. (7) and that the values resulting from

Eq. (5) lie in between the values produced by Eqs. (6) and (7). Typically, the

range of the average values in any one 1/3-octave band is about 2 dB except in

the bands centered at 80, 100, and 125 Hz, where the range is 3 to 4 dB. It is

further evident in Fig. 13 that the shapes of the three average noise reduction

curves are nearly identical so that the distinctions among the averaging techniques

are not critical for the purposes of the current study. For the current study,

it was decided to use Eq. (7) to combine the NIR values for the nine test

houses so as to produce a single filter shape.

4.2.2. Values of Average Noise Intrusion Reduction

The average (using Eq. (7)) NIR values in each 1/3-octave band for the

set of the nine test houses are presented again in Fig. 14. Also indicated

in Fig. 14 is the range of NIR values in each 1/3-octave band for average

values for individual houses and the range of NIR values for individual

microphone positions for all nine of the test houses. From Fig. 14 it is seen that the range of average NIR values for the individual houses is 10 dB

or less in all 1/3-octave bands except those centered at 80, 100, and 125 Hz.

31
50

40

30 -

CO 20

q:1—

z

UJ

CO

o

10

I 1

1 1 1 1

1 1 1

1 1

1

1 1 11 1 1

1 1

1 1 I

—

y -../^ —

Eq.(5) -— Eq.(6)

r -— Eq.(7)

—.1. 1 1 1 1 1 i 1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz|

Figure 13. Noise Intrusion Reduction values averaged over all

nine test houses using three different averaging

procedures.

32
50

S 40

o

I—

C_3 C3

LU

Zo

00

00

30

20 -

i 10

"T—I—

I—I—I—

I—I—I

\—I—I—

I—I—I—

I—I—I—

I—I—I

\—

Average for all houses and all mike positionsRange of averages

for individual houses

'—Range for individual mike

positions for all houses

L^L^ X_J \ L I I I 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY [Hz]

Figure 14. Average and range of Noise Intrusion Reduction values for

all nine test houses.

33
The range of values for the individual microphone positions is consistently

greater than the range of the (spatial) average values for the individual

houses — typically it is about 10-12 dB with the maximum range of 19 dB

occurring in the 125-Hz 1/3-octave band. From Fig. 14, it will also be

observed that the shapes of all five of the curves, i.e., the two pairs of

ranges and the overall average NIR, are quite similar except that below

250 Hz variations are more pronounced.

In calculating the nine-house average NIR values of Fig. 14, data from

a single passby of each test house were used. Data from more than one passby

of each test house might have been reduced and used to calculate the ninehouse average, but it is believed that this would not significantly reduce

the uncertainty in the nine-house average values. From Figs. 11 and 12, it

is seen that the range of NIR values for several vehicle passbys is small, on the order of 3 dB for most 1/3-octave bands. Further, for any given test

house, there is approximately equal likelihood that any one 1/3-octave band

value for one vehicle passby would be above or below an average value for

several passbys. Thus, when the values for nine houses are averaged, the

small differences between values for a single passby and an average of passbys

for any one house will tend to average out.

4.3 Comparison of the Average Noise Intrusion Reduction to Published Values of Sound Isolation

Published data on building sound isolation have been reviewed in order

to determine the range of typically-occurring sound isolation values. For

purposes of comparison to the current study, attention was restricted to

those studies which reported the results of field measurements for buildings

rather than laboratory measurements of the sound insulation properties of

building elements, such as windows and wall construction. With this restriction, it was found that only a limited amount of spectral building sound

isolation data is available in the literature. Of these reported data,

most were obtained using aircraft flyovers as the source of exterior noise,

with the remainder using traffic noise or controlled loudspeakers.

Published outdoor-to-indoor isolation data obtained for aircraft noise

sources are presented in Figs. 15 through 17, along with the average Noise

Intrusion Reduction curve from the present study. For the purposes of this

comparison, the average NIR values from the current study have been reduced

by 1.5 dB to account for average spherical divergence differences between

levels measured at the 3-m exterior microphone position and those at the

building surface. Further, for comparison with the published octave band

data, the 1/3-octave band NIR values averaged over the nine houses in the

present study have been combined into octave band values (the averaging

being done in a manner analogous to that represented by Eq. (7). The

resulting values are shown in Figs. 15 and 16. (Note that the data from the

34
50

00-a2 40

I—o

^

^

30

20

o: 10

31.5

• Average NIR - Current study

Average for cold climate houses (19)

Average for warm climate house (19)

Los Angeles data (13)

Los Angeles data (9)

63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz|

Figure 15. Comparison of average octave-band Noise Intrusion Reduction

values from the present investigation with sound isolation

values reported in the literature for aircraft noise.

35
50

CO

o 40

»—o

ZDO

LU

QC

LU 30

OO

CD

z

q:

C3O 20 O

CDO

10

31.5

• Average NIR - Current study

Average of Boston &

New York data

Range of Boston & New York data

63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure 16. Comparison of average octave-band Noise Intrusion Reduction

values from the present investigation with the average and

range of sound isolation values reported in the literature

for aircraft noise in the Boston and New York areas [27].

36
50

CO

S 40

o

CO

30

I

o 20

10

1—

"I r

-|—

T—

1—

• Average NIR - Current study

Brick house

Wood siding house

J L 31.5 63

J L J L 125 250 500 1000 2000

BAND CENTER FREQUENCY (Hz)

4000 8000

Figure 17. Comparison of average Noise Intrusion Reduction values

from the present investigation with sound isolation values

reported in the literature for brick and wood siding

houses at Wallops Island, Virginia [17]

I

37
present study correspond to interior sound levels being averaged over listener positions; this is not generally the case for the previouslypublished data.) Presented in Fig. 15 are the results of a Society of

Automotive Engineers (SAE) data summary document [19] and results of two

studies performed in the Los Angeles area [9,13]. The average house sound

isolation values compiled by SAE were grouped into those for warm and cold

climates since it was found that houses in warmer climates tended to have

(1) a larger ratio of window area to exposed wall surface, (2) windows not

as tightly fitted, and (3) lighter weight roof construction. It x^rill be

noted that the data reported for the Los Angeles area are quite similar to

the SAE warm climate average. Generally, the warm climate data display a flatter spectrum shape than those reported for the colder climates. This

relative flatness is due to lower isolation in the middle and high frequencies in comparison to the SAE cold climate average. It should be

noted that the average curve obtained in the present study is similar in

shape and magnitude to the SAE cold climate average, except in the

63-Hz 1/3-octave band.

For purposes of further comparison to data obtained in colder climates,

the average results from the literature for eighteen rooms in 6 houses in

Boston and New York [27] are presented in Fig. 16 along with the average

results of the present study. Also indicated in Fig. 16 is the range of

values observed in the Boston and New York data. This range, about 9 to

17 dB, is similar to the range in NIR values observed in the current study,

as shown in Fig. 14. The shape and magnitude of the two average building

sound isolation spectra presented in Fig. 16 are also similar.

Although most of the building sound isolation data reported in the

literature are octave band spectra, the results of one study are presented

as average 1/3-octave band values for two houses [17] . These data are presented in Fig. 17 along with the 1/3-octave band average NIR values

obtained in the current report for nine test houses. The published data

were for a frame house with brick veneer and a frame house with wood siding.

In comparison to the average NIR values of the current report, it is seen

that the published data display a slightly smaller slope.

The published building sound isolation data reported for traffic noise

sources are presented in Fig. 18. The published data in this figure correspond

to two studies, one conducted on one apartment in New York City [18] and one

study conducted on eight residential buildings in New York City, ten in

Boston, and eleven in Los Angeles [28] . Comparison of the published building

sound isolation values in Fig. 18 with those of this report indicates that the

published spectrum shapes are less steeply sloped than those obtained in the

current study. The NIR values reported in the current study are greater

than the published data for the New York apartment [18] at the middle and

high frequencies. Below 250 Hz, the data from the present study tend to be

lower than published data; thus the data of the current study show greater

slope with frequency.

38
50

CO

X3

°

40

I—o=>

ixJ

• Average NIR - Current study

New York apartment

New York average

Boston average

Los Angeles average

ocoo

30

20

10

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY IHzl

Figure 18. Comparison of average octave-band Noise Intrusion Reduction

values from the present investigation with sound isolation

values reported in the literature for traffic noise [18,28],

39
A final comparison of the average sound isolation values from the current

study to those reported in the literature is provided in Fig. 19. The published data shown in this figure correspond to building sound isolation data

determined for 14 residences in the state of New York [15] . The noise source used in these measurements consisted of three loudspeakers positioned outside

the dwelling. The interior sound pressure levels used to calculate attenuation

for this study were an average of data from a microphone position at the

geometric center of the room and at one typical listener position. Examination

of Fig. 19 reveals that the agreement between the published data and those

obtained in the current study is good, as indicated by differences of less

than 3 dB. Also shown is the range of values obtained in the reported study

for the 14 residences. This range, 10 to 17 dB, is similar to that observed

in the current study.

From the comparisons in Figs. 15 through 19, it is seen that the sound

isolation spectra determined in the current study are similar in both shape

and magnitude to most of those reported in the literature for dwellings in

cold climates. Further, from those studies in which the observed ranges of

sound isolation were reported, it is seen that the range of values in the

current study is consistent with ranges reported in the literature. It should

be noted, however, that the reported data for dwellings in warm climates

tend to have smaller slopes (versus frequency) than those of the current study.

For this reason, it should be realized that the filter shape developed as a result of the NIR data obtained in this study is most representative of cold

climate dwellings. Because sound isolation spectra for cold climates are more steeply sloped than those for warm climates, use of the cold climate data

to derive an outdoor-indoor filter results in a more significant modification

of an outdoor spectrum than might be expected to occur in the case of a warm climate dwelling.

40
50

CO

°

40

I—o

o

oro

o

30

20

Q= 10

Average NIR - Current study

Range of New York State data

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY [Hz]

Figure 19. Comparison of average octave-band Noise Intrusion Reduction

values from the present investigation with the average and

range of sound isolation values reported in the literature

for New York state houses subjected to controlled loudspeaker

noise sources [15].

41
5. Discussion of Noise Intrusion Reduction Results

Based on the Noise Intrusion Reduction (NIR) values reported in Appendix C

for Data Set No. 2 (see Section 3.3), several aspects of the results obtained

in the current study can be considered. These include the dependence of NIR

on building facade construction, openings in the facade structure, the position

of the exterior sound source, and the microphone positions. The influence of

the ratio of facade area to floor area was not considered because of the limited

range of this quantity for most of the test houses. Although the data set is

restricted to a limited number of houses and pass-bys, the results are believed

to be useful in indicating trends which may be more universally valid. These

trends should be further investigated.

5.1 Dependence of MR on Building Facade Parameters

In order to assess» within the current data set, the dependence of NIR

on building facade parameters, spatial-average NIR values for individual

test houses were grouped according to various facade parameters. For each

grouping, NIR values within that group were averaged using Eq. (7). Using

the averages and ranges of NIR within each group, comparisons among groupings

were made. Groupings were made to enable comparison among the parameters of

window type, window area (both frontal and total for the test room) , and

facade composition. Each grouping consisted of three test houses, selected

on the basis of similarity of one facade parameter, for example, all woodframe exterior wall construction. Due to the limited size of the data set,

it should be realized that for a pair of groupings used for a particular

comparison, the other facade parameters are varied. Thus, for example, in

comparing groupings with and without storm windows present, houses with

various wall constructions will be contained within each group. For this

reason, specific facade parameters cannot be isolated within each grouping.

5.1.1 Dependence on Presence of Storm Windows

The average NIR values for two groupings of houses with and without storm

windows are presented in Fig. 20. Examination of this figure indicates that

at frequencies higher than 250 Hz, the average NIR for the group with storm

windows is consistently higher than the average for the group without storm

windows. Above this frequency, the difference in the average NIR values is

3 to 5 dB, depending upon frequency. In addition to the average of the storm

window grouping being higher above 250 Hz, the average of this grouping does

not lie within the range of the group without storm windows. Also, the

average, above 250 Hz, of the group without storm windows does not lie within

the range of the group with storm windows. From Fig. 20 it appears that the

presence of storm windows on a building facade typically increases the NIR

of a house above 250 Hz.

42
CQ

O

O

50

40

30

20

S 10

T—

"I—T—

"1—

—1

\—\—I—

I—I—I—I—I—

Houses w/ storm windows

Houses w/o storm windows

Range of spatial average —

|

NIR for houses w/

storm windows

'—Range of spatial average NIR

for houses w/o storm windows

I I I I 1 I I I 1 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz)

Figure 20. Comparison of Noise Intrusion Reduction values averaged

for houses with and without storm windows.

43
The behavior indicated in Fig, 20 is consistent with findings from

laboratory tests of exterior window configurations. These laboratory data

show increased sound transmission loss when storm windows are added to

existing single windows (e.g., see [29]). Further, from previous studies, it

is known that transmission through windows is the path which typically

controls the overall sound insulation of a building facade at higher

frequencies [7,26]. For these reasons, the increase in measured NIR indicated

in Fig. 20 for houses with storm windows is generally consistent with

expectations based upon laboratory data.

5.1.2 Dependence on Window Area

Within the set of nine test houses in the current study, the range of

frontal window areas was from 2.3 to 4.5 m^, as indicated in Table 1. To

facilitate comparison of NIR values on the basis of frontal window area, the

three houses with the smallest areas (2.3, 2.7, and 3.3 m^) were grouped

together to form the first group and the three houses with the largest areas

(3.6, 3.9, and 4.5 m^) were grouped together to form th,e second group. The

NIR averages and ranges of these groupings are presented in Fig. 21. This

figure indicates that there is no discernible difference between the two

groupings. The curves defined by the average values of groups display

considerable crossing of each other throughout the frequency range and the

range of values for each group consistently overlap.

Although there is no observable difference between the two groupings of

Fig. 21, the sound transmission loss of facades is dependent on window area with sound transmission loss decreasing with increasing window area [26,29].

However, for this effect to be pronounced, the change in the ratio of window

area to wall area must be significant. For example, a change in the windowto-wall area from a ratio of 10 percent to a ratio of 40 percent typically

produces at most a 5.5 dB decrease in the sound transmission loss of a com- posite exterior wall [26]. For the average NIR values shown in Fig. 21, the

difference in the average window areas between the two window area groupings is

only 1.2 m2 for total wall areas of about 15 m^ . With such a small change in

window- to-wall area ratios, the similarity between the two groupings of Fig. 21

is expected, particularly since the influence of window type can be expected

to overwhelm the influence of window area for the houses of the present study.

In addition to comparing groupings of test houses on the basis of frontal

window area, a comparison was made on the basis of total window area within

the test room. In producing the groupings for this comparison, however, the

group with the larger total window area (4.6, 5.0, and 5.5 m^) was comprised

of three test houses with test-room windows to the side of the house, while

only one such house was included in the group with smaller total window area

(3.3, 3.4, and 3.8 m^) . Because of this difference in the location of windows

relative to the noise source, the resultant comparison must be qualified. The

averages and ranges of NIR for the two groupings of total window area are presented in Fig. 22. The values shown in this figure indicate that the average

44
CO

o

»—C3

o

oo

50

40

30

20 -

S 10 -

1—

I r "I—

I r I'M T\—\—I—

1—

Range of spatial average

NIR for houses w/ small

frontal window area

'—Range of spatial average NIR for houses w/ large frontal window area

-•— Small frontal window area Large frontal window area

1 J L J L J L I I I ill!

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz|

Figure 21. Comparison of Noise Intrusion Reduction values

averaged for houses with large and small frontal

window areas.

45
a

o

I—

a

LU

a:o

oo

50

40

30

20

(^2 <3S 10

1 r "I—

r

"1—I—

I—I—I—

I—I—

r

Range of spatial average NIRfor houses w/ small total window area

'—Range of spatial average NIR for houses w/ large total window area

J L J L J L

-•—Small total window area Large total window area

J I I I I I I I I \ I I L 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure 22. Comparison of Noise Intrusion Reduction values averaged

for houses with large and small total window areas.

46
NIR of the group with smaller total window area is consistently larger than

the average NIR for the group with larger window area for frequencies ranging

from 250 to 2,000 Hz. The significance of this average difference is inconclusive

as the average of the smaller total window area group is contained within the

range of the larger window area group for seven of the ten 1/3-octave bands

from 250 to 2,000 Hz. Little difference in the group NIR averages in Fig. 22

is expected as the increase in window-to-wall area ratio is small between

the groupings.

5.1.3 Dependence on Facade Wall Composition

Although all of the test houses were basically of frame construction, the

exterior finish varied within the set of nine houses. Two common types of

exterior finish were brick veneer (at least to the height of the ceiling of

the test room) and wood siding. Three houses of each type were selected

to form groupings to enable a comparison of NIR values for the two facade

wall compositions. The averages and ranges of NIR for these two groupings

are presented in Fig. 23. Examination of this figure reveals that for

frequencies from 63 to 500 Hz the average NIR value for the group of houses

with brick veneer is consistently higher by 2 to 8 dB than the average for

the group of houses with wood siding. It, appears, therefore, that a facade

with brick veneer may typically increase NIR at low frequencies relative to

that of a house with wood siding.

The increased NIR observed in Fig. 23 for brick veneer exterior walls

relative to wood siding is qualitatively consistent with findings reported in

the literature. In one laboratory study of the sound transmission loss of

exterior walls with windows, the data reproduced in Fig. 24 were obtained

[29] . The increased sound transmission loss for brick veneer walls in the

1/3-octave bands from 100 to 200 Hz, relative to that for wood siding walls,

is similar to the increase observed for NIR in Fig. 23.

From Figs. 20 to 23 it is observed that if two houses were similar

except that one had brick veneer and storm windows and the other had wood

siding and no storm windows, then the NIR of the first house would be expected

to be higher than the second throughout the entire frequency range. This

conclusion is based on the observed increased NIR at high frequencies for facades

with storm windows relative to those without and the increased NIR at low

frequencies for facades constructed of brick veneer as opposed to wood siding.

To verify this observation, it would be desirable to study additional houses.

However, lacking additional data, a comparison between Test House No. 7 and

No. 8 can be made. These two houses have similar window areas and both have

test-room windows to the side of the house. House No. 7 has brick veneer and

storm windows while House No. 8 has wood siding and no storm windows. The

average NIR for each house is plotted in Fig. 25. As would be expected from

the above arguments, the NIR values for House No. 8 are lower than those for

House No. 7 by 2 to 7 dB for almost all frequency bands. (Note that the isolation provided by a given house is also dependent upon air leaks as well as upon the wall and window types.)

47
o

a

o

oo

50

40 -

30 -

20 -

g 10

1 1

1

1 1

1

1 1

1

1

Range of spatial average-

~NIR for houses w/ brick veneer

^^ -•

1

1 1 1

1

1 1

1

1 1

1

1 1

'—Range of spatial average NIR

for houses w/ wood siding

Brick veneer

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hzl

Figure 23. Comparison of Noise Intrusion Reduction values averaged

for houses with brick veneer and wood siding.

48
oo

CO

ooo

CO

CO

CO

JU ''I'M 1 1

1

1 1

1

1 I

1

1 1

1

1 1

1

' '

40 — \ -

30

Sv^

20 - X/ • Brick veneer Wood siding

10 —

n 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1 , 1

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz]

Figure 24. Comparison of published sound transmission loss data

for exterior walls with brick veneer and wood siding [29]

49
JU 1 1

1 ' >

1

1 1 1

1 1

1

1 1 11 1

1

1 1

1

1 1

S 40 — r\

REDUCTrON

CO — y^y^^^^-*-^ 1

[INTRUSION CD '-^ • Test house #7

Test house #8

1

10

V-"

n 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure 25. Comparison of Noise Intrusion Reduction values, averaged

over listener positions, for Test Houses No. 7 (with brick

veneer and storm windows) and No. 8 (with wood siding and

no storm windows)

.

50
5.2 NIR with Windows or Doore Open

A comparison of the average NIR values with and without exterior windows

open for Test House No. 2 is presented in Fig. 26. For this particular case,

the total open area of the windows was 0.72 m^ with the open windows on the

front of the house. As would be expected, the effect of opening the windows

is to lower the NIR of the building throughout the entire frequency range.

The lowering of the average NIR values is particularly pronounced at the

middle and high frequencies, above about 80 Hz. Further, the average NIR

values display only limited frequency dependence, with all 1/3-octave band

values lying between 10.5 and 18.5 dB and with nearly zero slope for the

NIR-versus-frequency curve.

The effect of open windows on sound isolation, as indicated in Fig. 26,

is consistent with data reported in the literature. Typically, reported

values of sound isolation are not significantly dependent on frequency,

ranging from 10 to 20 dB for octave bands centered from 63 to 4,000 Hz

[8,14,18,30]. Individual differences among the various studies are probably attributable to variables such as window area, source of exterior

noise, location of the noise source, and microphone positions.

An effect similar to that illustrated in Fig. 26 was observed for average

NIR values with and without an exterior door open for Test House No. 9, as presented in Fig. 27. For this case, although the front door of the house

was open, the storm door on the opening was left in the closed position. The

storm door, however, had a 0.54 m^ screened opening. Except for the 1/3-octave

bands centered at 50 and 63 Hz, the resultant average values of NIR are not

significantly dependent on frequency, all 1/3-octave band NIR values lying

between 12 and 18 dB at frequencies above 63 Hz.

5.3 Dependence of NIR on Exterior Noise Source Position

5.3.1 Exterior Windows Closed

As discussed in Section 3.3, NIR values for Test House No. 8 at five

instances during a single passby of that house were obtained for Data Set

No. 1. These values were calculated using sound pressure levels (reduced

using an integration time of 0.2 seconds) which occurred simultaneously at

the exterior and interior microphone positions. The times for which the NIR

values were obtained correspond to the time at which the maximum A-weighted

sound level occurred at the interior reference microphone position, 2.8 and

1.4 seconds before this maximum, and 1.4 and 2.8 seconds after the maximum.

The average NIR values corresponding to these five instances during the

passby for House No. 8 are plotted in Fig. 28. Examination of this figure

reveals that generally there was no consistent relationship among the NIR

values at the different times during the passby. One exception to this

generality occurs at frequencies above 630 Hz. In this frequency range.

51
00

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40

30

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Windows open

(open area: 0.72m2j

J I I L_i I I I I I I

I I I I 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz|

Figure 26. Comparison of Noise Intrusion Reduction values,

averaged over listener positions, for Test House

No. 2 with and without windows open.

52
00

50

40

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S 10

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Door open

(open area: 0.54m2)

I I I I I

I 1 I I I \ I I I L 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz)

Figure 27. Comparison of Noise Intrusion Reduction values, averaged

over listener positions, for Test House No. 9 with and

without front door open.

53
00

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50

40 -

30 -

20 -

% 10

''I'M' 1

1 1

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^^A I m\v/ A-weigtited sound level ^/\i^fyf A -2.8 sec a^Pm rf-1.4 sec

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1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure 28. Comparison of Noise Intrusion Reduction Values,

averaged over listener positions, at various times

during the vehicle passby as determined from simultaneously

occurring exterior and interior sound pressure levels

at Test House No. 8 with windows closed.

54
the NIR values corresponding to 1.4 seconds after the maximum interior

level are consistently and significantly higher than those values for the

other times. This difference between the NIR value at 1.4 seconds after

maximum and the other values ranges from 2.5 to 10 dB in the 1/3-octave

bands above 630 Hz.

Although the position of the vehicle is not precisely known at the times

during the passby shown in Fig. 28 and the temporal variation in outdoorto-indoor sound level difference also depends upon the directivity of the

source, some qualitative inference of the dependence of NIR above 630 Hz on source position can be made from Fig. 28. As the vehicle approaches the

house, the NIR values (above 630 Hz) remain relatively low and then at some point when the vehicle is adjacent to the house (i.e, when the sound from

the vehicle is at near normal incidence relative to the front facade) , the

NIR value increases by 2.5 to 10 dB . As the vehicle recedes from the house,

the NIR values decrease.

The qualitative behavior of NIR values during the vehicle passby inferred

above is generally consistent with the fact that the sound transmission loss

of windows decreases as the angle of incident sound increases from normal

incidence [23-25] . Although sound transmission loss will vary depending on parameters such as window size, thickness, and double glazing, this basic

angular dependence occurs for most window designs [25] . Further, since the

sound transmission loss of windows is often the limiting element in the sound

insulation capabilities of facade structures [26] , it is expected that measures

of sound isolation in most field situations will display some angularlyd ep end ent behav ior

5.3.2 Exterior Windows Open

A comparison of NIR values at different instances during the vehicle

passby is presented in Fig. 29 for Test House No. 2 with the front windows

open. In this case, the NIR values determined with simultaneously occurring

exterior and interior sound pressure levels correspond to instances 2.0

seconds before, at, and 2.0 seconds after the time when the maximum A-weighted

sound level occurred at the interior reference microphone position.

Although there is variation among the NIR values occurring at the three

instances of time during the passby, the relationship among the values at

different times is not consistent from one 1/3-octave band to another except

in the ranges from 100 to 200 Hz and from 1,000 to 2,500 Hz. In the lower of

these two frequency ranges, the values of NIR at near normal sound incidence

(i.e., NIR at the time of maximum interior A~weighted sound level) are higher

55
50

S 40

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1—

r

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30

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Time relative to time

of maximum interior

A-weighted sound level • -2.0 sec A sec

+2.0 sec

g 10

J L J L I I I I J L I I I I J L 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz)

Figure 29. Comparison of Noise Intrusion Reduction Values, averaged

over listener positions, at various times during the vehicle

passby as determined from simultaneously occurring exterior

and interior sound pressure levels at Test House No. 2 with

windows open.

56
than the values before and after the maximum. In the higher frequency range,

this ordering is reversed as the NIR values at near normal incidence are less

than the other two. It should be further noted that in the higher of these

frequency ranges, the qualitative behavior of NIR values during the vehicle

passby with the windows open is the opposite of that observed with the windows

closed. With the windows open, the NIR decreases as the vehicle approaches

the house, reaching a minimum when it is in front of the house (near normal

incidence) and then increasing again as the vehicle continues on beyond the

house. This behavior is consistent with that reported in the previous work

for the high frequency case when the acoustic wavelength of the incident sound

is less than the dimensions of the window opening. For this high frequency

case, the sound transmission loss of an open window increases with increasing

angle of incidence as £og(sec 0) , where 9 is the angle from normal incidence

[24].

5.4 Variation Between NIR Values for Listener and Interior Reference Microphone Postions

The NIR values reported in Appendix C (Data Set No. 2 of Sec. 3.3)

for one vehicle passby at each of the nine test houses can be used to make

some comparison between NIR values determined at individual listener positions

and the interior reference microphone position. As noted in Sec. 3.2, at

each of the nine test houses the interior reference microphone was 1 m from

one of the test room windows which faced the street on which the vehicle passed

by. On the other hand, the listener position microphones bore no particular

relationship between one house and the next as they were determined by the

location of furnishings in each individual room. Due to the consistency of

the placement of the reference microphone position, it is of interest to

compare the NIR values measured at this position with those determined at

the listener positions to determine if any consistent relationship exists

from house to house.

To compare reference and listener position NIR values, the NIR value

deteirmined at the reference microphone position for each house was subtracted

from each of the three individual listener position NIR values for the

corresponding house. With the nine test houses, 27 such differences between

listener and reference position values were obtained for each 1/3-octave band

centered from 50 to 4000 Hz, The mean (x) , standard deviation (a), and

extremes of the 27 values in each 1/3-octave band were then determined. These

resultant values are plotted in Fig. 30 and are presented in Table 4. To

provide some indication of the distribution of the values of difference between

the listener and reference positions, frequency histograms of these values are presented in Fig. 31 for the 1/3-octave bands centered at 125, 500, and 2500 Hz.

Prior to examining the results presented in Fig. 30 and Table 4, the

distributions indicated in the frequency histograms of Fig. 31 should be

considered. From this figure, it appears that the distributions of the

NIR differences tend to approach a normal distribution for the 500- and 2500-Hz

1/3-octave bands. For the 125-Hz 1/3-octave band data, however, a tendency

toward normal distribution is less apparent. More data would be required to

ascertain the form of the distribution for the 125-Hz band.

57
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i_ 1 1 1 1 1 1 1 1 1 1 1 1 r 1 1 1 1 1 1 1

1 1 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz|

Figure 30. Mean, standard deviation, and range of differences between

Noise Intrusion Reduction values determined for individual

listener positions and those for interior reference positions,

for the set of all nine test houses.

58
Table 4. Mean, standard deviation, and extreme values of

differences between NIR values determined at individual listener

positions and at interior reference positions for all nine test houses.

1/3-Octave Band

Center Frequency

Difference Between NIR Values for Listener and Reference

Positions

Mean

Standard

Deviation Maximum Minimum

50 Hz

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

1.3 dB 3.3 dB

0.8 3.3

1.4 3.9

0.4 3.4

0.3 4.3

1.1 4.3

3.6 3.8

4.8 3.3

3.9 3.8

2.4 3.2

1.7 2.3

1.6 1.8

1.8 1.7

1.7 2.1

2.1 2.2

2.3 2.1

1.8 2.3

1.7 2.1

1.5 2.8

1.2 2.4

7.9 dB

7.9

10.7

5.6

7.6

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10.5

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6.5

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59
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i^-L

-10 -8-6-4-2 2 4 6 8 10 DIFFERENCE IN NIR VALUE, LISTENER POSITION-REFERENCE POSITION |dBj

Figure 31. Frequency histograms of the differences

between Noise Intrusion Reduction values

determined at individual listener positions

and at the interior reference position for

all nine test houses.

60
Examination of the data in Fig. 30 and Table 4 reveals that, except

for the two 1/3-octave bands centered at 100 and 125 Hz, the mean values

of the difference in NIR values are consistently positive. This indicates

that, on the average, the NIR values for the listener positions are higher

than those for the reference position. Above 315 Hz, the mean difference is

between +1 and +3 dB; from 200 to 315 Hz, the mean is slightly higher, +3 to

+5 dB; below 200 Hz, the mean varies from about -.5 to +1.5 dB . Although

the frequency dependence of the mean values appears to have some consistency,

further data and analyses would be required to provide quantitative explanations of the observed behavior. The standard deviations and ranges of

values also indicate some frequency dependence, with these quantities

generally decreasing with increasing frequency. This behavior is consistent

with the higher spatial variation of NIR values that is evident in the lower

frequency bands.

The standard deviations in Fig. 30 and Table 4 range from 1.7 to 4.3 dB

The range of values varies from 7.5 to 17.1 dB. From Fig. 30 and Table 4,

the NIR values at listener positions can be estimated from measured values

obtained at the reference microphone position. In field measurement

situations, if resources preclude the use of more than one microphone, the

reference microphone position could be used with the data of Fig. 30 and

Table 4 used to estimate NIR values at listener positions.

61
6. Implication of Results for Measurements of Sound Isolation

6.1 Measurements of Exterior Sound Pressure Levels

6.1.1 Theoretical Considerations

As discussed in Sec. 2.2.1, the sound incident on a building facade

is measured in the presence of the vertical surface defined by the facade.

The presence of this vertical surface creates ambiguity in the determination of the magnitude of the incident sound as the sound pressure level

measured adjacent to the building results from a combination of directly

incident and reflected sound. Because of interference between the direct

and reflected sound, frequency dependent differences between measured sound

pressure level and the level of the incident sound wave occur as a function

of the distance of the microphone from the surface and of the characteristics

of the surface. For this reason, in determining building sound isolation or facade insulation, the influence of the placement of the exterior microphone

relative to the building facade is important.

In order to obtain a basic understanding of the variations in the sound

pressure level occurring as a result of interference between the direct and

reflected sound waves caused by the vertical plane of the building surface,

a simple model of the building surface is of use. In previous studies of

sound reflection [33] it has been assumed that the vertical building surface

is planar, infinite in extent, and of real acoustic impedance and that reflections from this surface are specular. To illustrate the application of this

model to building surfaces, a value of acoustic impedance corresponding to a normal incidence sound absorption coefficient of 0.1 can be assumed. This

value of sound absorption is tj^ical of exterior building materials such as brick, concrete, wood, and glass over the frequency range of interest [34]

.

Using the above model, the increase in 1/3-octave band sound pressure

level, due to reflected sound, above the level of the incident sound, can be

calculated [33] . The increase in level for normally incident sound is plotted

in Fig. 32 as a function of path length difference between the sound arriving

directly from the noise source to the microphone position and that which is

reflected from the vertical building surface. The path length difference in

Fig. 32 is expressed in terms of acoustic wavelengths since the increase in

level due to reflection is both a function of path length difference and

acoustic wavelength (or alternatively, frequency) . In calculating the values

shown in Fig. 32, the direct path of sound from source to receiver was taken

to be much greater than the path length difference between direct and

reflected sound in order to eliminate dependence of increased level on the

direct path length.

62
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100

Figure 32. Increase in 1/3-octave band sound pressure level due

to reflection from an infinite plane of real impedance

with a sound absorption coefficient of 0.1.

63
From Fig. 32, It is seen that the increase in level due to the sound

reflected from a vertical building surface, as idealized above, exhibits

variation as a function of path length difference. This variation is most

pronoTonced for path length differences between 0.2 and 4.0 acoustic

wavelengths. In this region, minima occur at path length differences of 0.5,

1.5, and 2.5 acoustic wavelengths, corresponding to increased levels of -13,

-5, and -1 dB, respectively. Below about 0.2 acoustic wavelengths, the

increase in level is essentially independent of path length difference, having

a value of about 5.5 dB for the assumed value of 0.1 for the absorption

coefficient. This region is commonly referred to as the region of "pressure

addition" of the direct and reflected sounds. Above about A.O acoustic

wavelengths, the increase in level is also virtually independent of path

length difference and has a value of about 2.5 dB. This region is commonly

referred to as the region of "energy addition" of the direct and reflected

sounds

.

The information conveyed in Fig. 32 can be used to address the question

of microphone placement relative to a vertical building surface for the

purpose of determining sound isolation. It is seen that if the exterior

microphone is placed at a distance such that, for the frequency range of

interest, the path length difference is between 0.2 and 4.0 acoustic

wavelengths, then the measured exterior 1/3-octave band sound pressure level

will be frequency dependent due to the presence of the vertical building

surface. However, the distance of the microphone from the building surface

can be selected to avoid such frequency dependence. This is accomplished by

selecting a distance such that the path length differences, for the frequency

range of interest, are contained either in the pressure addition or energy

addition region. For these regions the presence of the vertical building

surface raises the sound pressure level by nominally 5.5 or 2.5 dB, respectively,

assuming an absorption coefficient for the building facade of 0.1.

In practical measurement situations, neither pressure nor energy addition

of the direct and reflected sound can be completely achieved for several

reasons. For the frequencies of interest, to obtain energy addition for the

entire frequency range would require quite large distances from the building

surface, e.g., 6-10 m. This would probably be an unacceptably large distance in

most measurement situations due to the uncertainty introduced by propagation

differences between the microphone position and the building surface and, for

traffic noise, due to the fact that the microphones might have to be located in

the middle of the street. In addition, the finite extent of buildings and the

presence of surface irregularities would lead to departures from the behavior

predicted by a simple model based on specular reflection from an infinite vertical

plane. To obtain pressure addition for the entire frequency range typically of

interest, the microphone would have to be either flush mounted in the building

surface or within less than 2 cm of the surface. It should be noted that 2 cm is

about the diameter of microphones typically used to make outdoor sound pressure

level measurements. Further, this distance would not allow the use of conventional

microphone windscreens, which are typically 9 cm or more in diameter. Because

64
of practical limitations on the use of sufficiently distant or sufficiently

close microphone positions relative to the building surface, significant

frequency-dependent variations in the measured sound pressure level due to

the presence of the vertical building surface will typically occur.

For the energy addition region defined from Fig. 32, reflections from

real building surfaces are further modified from the idealization in this figure

by scattering from irregularities in the building surface due to window

recesses, decorative facade structure, etc. Reflection from surfaces

containing variations similar to those typically occurring on building

surfaces has been studied both theoretically and experimentally [33,35]. In

one study [33] , it was determined that the ratio of reflected to incident

mean-square sound pressure is dependent on the angle of the Incident sound.

This was found to be true for octave bands centered from 250 to 2000 Hz. The

angular dependence reported in Ref . 33 for typical building surfaces

containing periodic irregularities is given in Fig. 33 as averaged over the

four octave bands used in the study. From Fig. 33 it is seen that the

mean-squared pressure ratio of reflected to incident sound varies from .8 at

normal incidence to .2 at grazing incidence. This corresponds to a sound

pressure level variation ranging from 2.5 dB to 0.8 dB. In practical

situations, the behavior indicated in Fig. 33 increases the uncertainty in the

measurement of the exterior sound pressure level by as much as 1.3 dB for the

octave bands centered between 250 and 2,000 Hz and for buildings with periodic

surface irregularities. For buildings with non-periodic surface

irregularities and at frequencies outside the range from 250 to 2,000 Hz, the

possible magnitude of this effect is not known at present.

In addition to the dependence of the ratio of mean-squared pressure of

reflected and direct sound on angle of incidence as indicated in Fig. 3 3, it was further reported in Ref. 33 that spatial variation of the reflection ratio

occurred depending on the specific details of the surface geometry. An

example of such spatial variation is presented in Fig. 34 for one of the

surface configurations included in the study for the 500-Hz octave band. In

this figure, the specific surface geometry is Indicated along with the

position of the microphone relative to the surface. The resultant increase in

the measured sound pressure level at the microphone position due to the

reflected sound is shown as a function of microphone location. For the

example of Fig. 34, the measured level varied by as much as 2-4 dB , depending on

the exact relation of the microphone position to the building surface.

Similar variations were noted for the 250, 1000, and 2000 Hz octave bands and

for other surface geometries. Also, the spatial variation of the increased

level due to reflection was found to be most pronounced near normal incidence.

The spatial variation indicated in Fig. 34 is expected to exist in most

field measurement situations when exterior sound pressure levels are measured

in the presence of a vertical building surface. For a stationary source, as examined in Fig. 34, this spatial variation can introduce uncertainties of

about 3 dB in the exterior sound pressure levels when measurements are made

in octave bands. For narrower frequency bands, the magnitude of the uncertainty

65
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1 1 1 1 1 1 1 1 10 20 30 40 50 60 70 80 90

ANGLE FROM GRAZING INCIDENCE (Degrees)

Figure 33. Measured ratio of reflected to incident meansquared pressures, averaged for frequencies

corresponding to 250, 500, 1000, and 2000 Hz [33]

66
RECEIVER POSITION

NO. 1 2 3 4 5 6 7 8

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Figure 34. Spatial variation of 500-Hz octave band sound

pressure level due to reflection from a periodic,

rectangular surface protrusion [33]

67
has not been determined, but it is expected to be as large or larger than

that found when measurements are made in octave bands. Further, it should

be noted that if the depths of irregularities in the building surface are

less than those indicated in the example of Fig. 34, the indicated spatial

variation would still occur, but in a higher frequency band. For example,

if instead of being 24 cm, the depth of the protrusions in Fig. 34 was

12 cm, the variation indicated for the 500 Hz octave band would occur in

the 1000-Hz band. Thus, even relatively small irregularities in the building

surface can produce spatial variation in the measured exterior sound pressure

level in some of the frequency bands of interest in measures of building

sound isolation.

6.1.2 Results of the Current Study

The measured exterior sound pressure level data obtained in the current

study can be used to examine some of the aspects of the exterior measurement

problems described in the previous section. As discussed in Section 3.2,

three microphones were used to measure outdoor sound pressure level at each

test house. Two of these microphones were positioned 3 m away from the

building facade and separated by 1.8 m for all nine test houses. The third

microphone was positioned 4.5 cm from the facade for seven of the test

houses; for the other two houses, one was placed at 15 cm, and one at 1.6 m.

The sound pressure levels measured at the various exterior microphone

positions can be used to examine two of the three aspects discussed in the

previous section. The data can be used to examine the interference of direct

and reflected sound and its relation to microphone placement relative to the

building facade. Also, the spatial variation in sound pressure level measured

at two microphone positions at 3 m from the building facade can be examined.

However, angular dependence of the ratio of reflected to direct mean-square

pressure cannot be addressed since the angle of the incident sound is not

known and the output of the source was not necessarily constant during the

passby.

A comparison between exterior sound pressure levels measured at the

three positions for Test House No. 2 is shown in Fig. 35. The sound pressure

levels (determined with an integration time of 0.2 seconds) presented in

this figure are those which simultaneously occurred at the three positions

at the time of maximum A-weighted sound level at the interior reference

microphone position. For this house, in addition to the two 3-m exterior

positions, a microphone position 4.5 cm from the facade was used.

Much of the variation indicated in Fig. 35 between the sound pressure

levels at the 3-m positions and those at the 4 . 5-cm position can be attributed

to differences in interference of the direct and reflected sound for the two

microphone distances. The increases in level expected (see Fig. 32) for

the two microphone distances of Fig. 35 are presented in Fig. 36 as functions

of frequency. From Fig. 36, the differences in the increase in level

between the 3-m and 4 . 5-cm positions indicate that the measured sound pressure

levels at the 4 . 5-cm positions are about 1 to 3 dB higher than those at the

3-m position for frequencies between 50 to 800 Hz, except for the 80 Hz

band. This predicted behavior is seen in Fig. 35 for most of these

frequencies, particularly those between 250 and 800 Hz. For the 80-Hz band.

Fig. 36 indicates that the difference between the levels at the two microphone

68
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CO a.

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90

80

70

60

50

40

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Mike position #2, 3m from facade

A Mike position #3, 3m from facade

J L J L J L J L 1 J I I \ \ 1 I L 31.5 63 125 250 500 1000 2000

BAND CENTER FREQUENCY |Hz|

4000 8000

Figure 35. One-third octave band sound pressure levels measured outside

Test House No. 2 at three microphone positions at the time

of maximum interior A-weighted level.

69
IT 20

00

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CL

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CO

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10 -

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31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure 36. Computed increase in 1/3-octave band sound pressure level

due to reflection from an idealized planar surface for

microphone positions located 4.5 cm and 3.0 m from the surface.

70
positions should be about 10 dB . The measured sound pressure levels of

Fig. 35 indicate a difference of 5.5 to 6.5 dB for the 80-Hz band. Between

1250 and 3150 Hz, Fig. 36 indicates that the level at the 4.5-cm microphone

should be less than that at the 3-m position. This difference is as much

as 12 dB in the 2000-Hz band and 9 dB in the 2500-Hz band. This predicted

behavior is also indicated in Fig. 35. For the 2000-Hz band the measured

level at the 4.5-cm position is 9 to 11 dB lower than that at the 3-m position

and the level in the 2500-Hz band is 7 to 9 dB lower.

Figure 35 can also be used to examine the variation in measured level

between the two 3-m positions. Below 2000 Hz, the sound pressure levels

measured at the two positions are nearly identical, with individual variations

of no more than 1.5 dB. At 2000 Hz and above, slightly more variation between

the levels at the two positions occurs. For these frequencies, typical

variations are 1 to 2 dB . Although these high frequency variations are consistent with the variations attributable to surface irregularities of

small depth, variations of this small magnitude could also occur due to other

physical phenomena.

Another comparison of sound pressure levels measured simultaneously at

three exterior microphone position is shown in Fig. 37 for Test House No. 5,

where, in addition to the 3-m positions, a microphone was placed 15 cm from

the facade. The increase in level due to reflection from the building facade,

as determined from Fig. 32, is plotted in Fig. 38 for the two microphone

distances.

As in the previous example of Figs. 35 and 36, much of the variation

seen in Fig. 37 in the measured sound pressure levels between the 3-m and

15-cm positions can be attributed to reflections as shown in Fig. 38. Below

250 Hz, the measured sound pressure level at the 15-cm position is greater

than that at the 3-m position. Further, for the 500- and 630-Hz bands, the

level in Fig. 37 corresponding to the 15-cm position is less than that corresponding to the 3-m position, as is also indicated in Fig. 38, The measured

level in the 1000- and 1250-Hz bands is greater for the 15-cm position, as

is consistent with the predicted difference of Fig. 38. Above 1250 Hz, with

the exception of the 1600-Hz band, the variations indicated in the two figures are also consistent.

A final comparison of measured exterior sound pressure levels is

presented in Fig. 39 for Test House No. 6. For this house, two microphones

were located 3 m from the building surface and one 1.6 m from the surface.

The increased level expected (see Fig. 32) for these two microphone distances

is plotted in Fig. 40. As in the previous two examples, the variations

between the measured levels at the 3 and 1.6m positions are consistent with

the variations of increased level due to reflections from the building surface.

As would be expected from Fig. 40, the measured levels of Fig. 39 show only

minimal variation between observations at the two microphone distances. Above

100 Hz, the levels at 1.6 m are consistently within 1 or 2 dB of at least one

71
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70

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60 —

L -

50

/in 1 1

• Mike position #1, 15cm from facade

Mike position #2, 3m from facade

A Mike position #3, 3m from facade

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure 37. One-third octave band sound pressure levels

measured outside Test House No. 5 at three

microphone positions at the time of maximum

interior A-weighted level.

72
GQ

_, 20 -

»

00

co

CO

00

10 -

-

-10 -

"20 -

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY [Hzj

Figure 38. Computed increase in 1/3-octave band sound pressure level

due to reflection from an idealized planar surface for microphone positions located 15 cm and 3.0 m from the surface.

73
00-o

QCM

00oo

LU

QOO

90

80

70

60

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Milte position #2, 3m from facade

Mike position #3, 3m from facade

CO 40 J L J L J L J L J L I I I I I 31.5 63 125 250 500 1000 2000

BAND CENTER FREQUENCY (Hz)

4000 8000

Figure 39. One- third octave band sound pressure levels

measured outside Test House No. 8 at three

microphone positions at the time of maximum

interior A-weighted level.

74
00

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1

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-20

1 1 1 1 1 1 1 1 1 1 1 1 i 1 1

1 1 1 1 1 1 1 1

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz]

Figure 40. Computed increase in 1/3-octave band sound pressure level

due to reflection from an idealized planar surface for

microphone positions located 1.6 m and 3.0 m from the surface.

75
of the levels measured at 3 m, except for the 4000-Hz band. For the

50- and 63-Hz bands, the lower measured levels at the 1.6 m position are also consistent with the difference in increased level due to

reflection indicated in Fig. 32. For the 80- and 100-Hz bands, as expected from Fig. AO, the level measured at the 1.6-m position is higher

than that at the 3-m positions.

6.1.3 Implications for Sound Isolation Measurements

The results of Sees. 6.1.1 and 6.1.2 can be used to address two sources of uncertainty in the measurement of exterior sound pressure level

for the purposes of determining building sound isolation. The first of

these uncertainties arises from frequency-dependent interference of the

sound directly incident from the source at a given microphone position and

that reflected from the vertical building surface. The second of these

uncertainties arises from spatial variation of measured sound pressure

levels at a fixed distance from the building surface.

In Figs. 35-40, it was shown that the model of reflection from

vertical building surfaces as discussed in Sec. 6.1.1 and illustrated

in Fig. 32 can be used to estimate the variation in measured sound pressure

level for different microphone distances from the building facade. The

model can therefore be used to attempt to optimize the distance at which

the microphone is placed so as to minimize the variations due to frequencydependent interference between the direct and reflected sound.

As discussed in Sec. 6.1.1 energy or pressure addition of the direct

and reflected sound over the entire frequency range of interest is usually

not achievable. It is therefore necessary to select a measurement distance

which is practical, minimizes the variation due to interference, and is not

too distant from the building facade. For purposes of comparison, the

increased level due to reflection is plotted in Fig. 41 for the microphone

distances of 2 m (as specified in the ISO and proposed ASTM standards [4,5],

2 cm (as specified as an alternative in the ISO proposal), and 3m (as used

in the present study)

.

The amount of variation in increased level for any one microphone

position depends on the frequency range of interest. In the current study.

Noise Intrusion Reduction (NIR) was determined from 50 to 4000 Hz. For this

frequency range. Fig. 41 indicates that the smallest range of variation occurs

for the 3-m position, 8 dB versus 18 dB and 10 dB for the 2-cm and 2-m positions,

respectively. For the 2-cm position, the large variation observed occurs above

2000 Hz. Below this frequency, the 2-cm position displays little variation

with frequency, less than 2 dB . Variation for the 2-m position is most pronounced below 200 Hz. At 200 Hz and above, the variation in increased level

at this position is less than 3 dB . For the 3-m position, the variation above

80 Hz is less than 3 dB.

76
00

00

oo

oe

QO

00

CO

oo

LU

o

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure 41, Computed Increase in 1/3-octave band sound pressure level

due to reflection from an idealized planar surface for

microphone positions located 2 cm, 2.0 m, and 3.0 m from

the surface.

77
In the ISO and proposed ASTM standards [4,5], the frequency range of

interest is from 100 to 4000 Hz. In this frequency range, significant

variations at the 2-m and 2-cm position are present. For the 3-in position,

however, the range of variation is small, less than 3 dB , so that this

position affords significantly less uncertainty in the measurement of the

exterior sound pressure level in the frequency range of typical interest.

The uncertainty due to reflection in the exterior sound pressure level

measurement can be minimized by either of two methods. The first is the

simultaneous use of more than one microphone distance. From Fig. 36, it is seen that a microphone distance of 4.5 cm or less results in variations of

less than 1 dB below 500 Hz, with the increased level corresponding to pressure

addition of the direct and reflected sound. At and above 500 Hz, a distance

of 2 m or greater also produces variations of less than 1 dB and corresponds

to energy addition of the direct and reflected sound. Thus to determine the

exterior sound pressure level below 500 Hz, the near microphone position can be used provided that 5.5 dB is subtracted from the measured level to estimate

the incident sound pressure level. At and above 500 Hz, the far microphone

position can be used provided that 2.5 dB is subtracted to yield an estimate

of the incident sound pressure level. Although some uncertainty is introduced

into this measurement technique by the assumed increased levels for pressure

and energy addition (5.5 and 2.5 dB, respectively), this uncertainty is not

expected to be large, at most 3 dB. This should be compared with the 10 to

18 dB variation indicated in Fig. 41 for the 2-m and 2-cm microphone positions.

The second method of minimizing uncertainty is to use a distance sufficiently

large to yield energy addition throughout the frequency range of interest.

In selecting a distance greater than a few meters, however, some uncertainty

may be introduced due to differences in sound propagation from the source

to the microphone and from the source to the building facade and due to the

fact that the building is not a smooth, infinitely-large plane. In the

current study, from Figs. 35-40, any variations due to differences in propagation between the 3-m microphone position and those closer to the building

were small compared to the variations observed due to differences in interference of the direct and reflected sound at the different microphone distances.

A second source of uncertainty in the measurement of exterior sound

pressure levels is the spatial variation of measured level at a fixed distance

from the building surface. In Sec. 6.1.2 it was observed that variations

of as much as 5 dB occurred between sound pressure levels measured at the two

3-m microphone positions. The cause of this spatial variation cannot be

conclusively determined; however, the magnitude of the variation is consistent

with that known to occur due to scattered reflection from irregularities in

the vertical surface of the building, as discussed in regard to Fig. 34. To

reduce the uncertainty in the measured exterior sound pressure level due to

spatial variation of the exterior sound field, averaging of the levels measured

at several microphone positions can be used. Determination of the number of

microphone positions required to reduce significantly the uncertainty in the

measured exterior level, however, was beyond the scope of the current study.
6.2 Measurement of Interior Sound Pressure Levels

Uncertainty in the measurement of interior sound pressure level for

purposes of determining building sound isolation can be introduced both by

spatial variation of the interior sound field and by the dynamic range of the

sound pressure levels within the receiving room. From the Noise Intrusion

Reduction (NIR) data reported in Appendix B, the spatial variation of the

interior sound field is indicated by the variation in NIR seen among

individual microphone positions within a given test house. Typically, this

variation is more pronounced in the lower frequency bands (200 Hz and below)

than in the higher frequency bands. At lower frequencies, spatial variation

can occur due to wave phenomena of the sound field within the enclosed space

of the receiving room. In the higher frequencies, wave phenomena are of less

importance but, particularly in residential rooms where reverberation times are low, spatial variation can occur due to the influence of the direct sound

field within the room relative to the reverberant sound field.

The range of interior sound pressure levels, particularly when existing

traffic is used as a source of noise, can also result in uncertainty in the

interior measurements due to difficult dynamic range requirements for

instrumentation and to background noise within the receiving room due to other sources of noise located inside the building.

6.2.1 Spatial Variation at Low Frequency

As an example of the variation in NIR values determined for the three

different listener microphone positions within a given receiving room, the

values determined for Test House No. 5 (see Appendix C) are presented in

Fig. 42. This figure indicates that substantial variation in the measured

interior sound pressure levels occurred in the frequency bands below 315 Hz.

For the 100-Hz 1/3-octave band, the variation is as great as 16 dB

At low frequencies, the spatial variation of the sound field in a room can be interpreted in terms of the formal wave-theory solution for

a rectilinear closed space [22,36]. Examination of the computed eigenfunctions for the six normal modes that would be expected to exist in the

100-Hz, 1/3-octave band for the dimensions of the room in Test House No. 5 showed qualitative agreement with the results of Fig. 42 for the 100-Hz

band.

If the number of normal modes within a 1/3-octave band is small,

large spatial variation of the band pressure levels is likely. As the

number of modes within a band increases, large spatial variation of the

band pressure level becomes less likely. The average number of normal

modes, AN, within a frequency band, Af , is given approximately by the

expression:

A^T f 4TTf^V . TTfS , L \,^ ,ON

79
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1

1 1 11 1 I1 1 1

1 1—

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1 1 -

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REDUCTION

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INTRUSION to CD - rhy • Mike position #1 —

- U4 T

Mike position #2 _ LU

1

10 -m Mike position #3 —

n 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz)

Figure 42. Noise Intrusion Reduction for the three listener positions

at Test House No. 5 with windows closed.
where c is the speed of sound, f is the center frequency of the band, V

is the room volume, S is the total surface area, and L is the sum of the lengths

of all the edges of the room [36]. From this expression, it is seen that the

number of modes in a fixed bandwidth increases with both the size of the room

and frequency. For 1/3-octave bands, the increase in the number of modes with

increasing frequency is further emphasized as the bandwidth also increases

in proportion to the band center frequency.

As an example of the increase in the number of modes as a function of

frequency for 1/3-octave bands, the average number of modes in a 1/3-octave

band, as calculated for Test House No. 5, is plotted in Fig. 43. For the

100-Hz band, the average number of modes within the band is about 6. Above

100 Hz, the average number of modes increases rapidly, reaching about 64

for the 250-Hz band. Because of the rapid increase in the average number

of modes with frequency as indicated in Fig. 43, spatial variation in

measured sound pressure levels due to wave phenomenon in the room decreases

rapidly with frequency.

Substantial uncertainty in measures of building sound isolation can be

introduced at low frequencies due to wave phenomena within the receiving

room. This uncertainty may be reduced by averaging the mean-square pressure

over a number of microphone positions throughout the receiving room. From

the data for individual listener positions within each of the nine test

houses of the current study, variations in NIR for individual houses were

observed to be as much as 7 to 16 dB for 1/3-octave band center frequencies

from 50 to 200 Hz. Above these frequencies, spatial variations were observed;

however, it is unlikely that at these higher frequencies spatial variations

are attributable to normal mode wave phenomena within the receiving room.

6.2.2 Spatial Variation at High Frequency

6.2.2.1 Windows Closed

As indicated in Fig. 42, the variation among NIR values determined

at individual interior microphone positions above 250 Hz is typically less

than that at lower frequencies. From the data presented in Appendix B, the

variation of NIR values among individual listener positions was typically

about 3 dB but in some cases was as much as 8 dB

To obtain some understanding of the sound field within the receiving

room for the higher frequencies, sound within the room can be conceptualized

as acoustic rays emanating from the source of sound, propagating outward

until reflected from a room wall, and then being repeatedly reflected. The

sound received, at a point in the room, which comes directly from the source

is termed the direct sound field, while sound which is reflected at least once is termed the reverberant sound field [22] . The total mean-square

sound pressure at a point a distance r from a source is given by:

81
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50

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LU 40

to

LU

LU

30

20

10

T—I—

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I—I—

r

T—I I

I I—i—r

31.5

I I I I I I I I I I I I I I I I 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz|

Figure 43. Approximate average number of room modes in a 1/3-octave

band for Test House No. 5.

82
>2 _= pcW

% ^ 4

i\ + —

ATTr"^ A

(9)

where p is the density of air, c is the speed of sound, VJ is the acoustic

power output of the source, Qg is the source directivity factor in a particular direction 6, and A is the total absorption in the room [22].

The first term in Eq. (9) corresponds to the direct field while the second

term represents the reverberant field. Based on Eq. (9) with A=27 m2 (typical

for the test houses of this study) , relative sound pressure level as a function

of distance from the source of noise is plotted in Fig. 44 for values of Qg

of 1, 4, and 8. For the omni-directional case (i.e., Qq=1) . the variation

of sound pressure level is less than 1 dB at distances greater than 1.5 m

from the source. For distances less than 1.5m, the level increases rapidly

as the source is approached, corresponding to increasing influence of the

direct sound field of the source.

When the sound field within a receiving room is produced by sources^

exterior to the building, the sources of noise within the room are building

shell elements such as windows, doors, air leaks, etc. When the dimensions

of these radiating elements are less than one acoustic wavelength, Qg=2,

typically [24] . For higher frequencies, as the acoustic wavelength of the source approaches the dimension of the source, the radiation may become even more directive, producing still higher values of Q. in certain directions

[36]. The effect that higher values of Q have on the fall-off of sound

pressure level with distance, in a receiving room typical of those in the

current study, is illustrated in Fig. 44 for Q values of 4 and 8. It is seen that as the source becomes more directive, the influence of the direct

field of the sound source, relative to the reverberant field in the room,

extends farther away from the radiating element. Thus, at 1.5m from the

radiating element, while the sound pressure level due to a point source

(Qq =1) is only about 1 dB above that of the reverberant field in the room,

the levels due to a directive source are 2 . 5 dB and 4.5 dB above the reverberant values for Q. values of 4 and 8, respectively.

Although precise values of Q cannot be readily assigned. Fig. 44 is

useful in understanding causes of spatial variation of sound pressure level

within the receiving room at higher frequencies. Depending cm the directivity

of the source, it is seen that the influence of the direct field of a noise

source may extend well into a room. If this does occur, then the sound field

produced within the room will display a spatial variation due to the distance

dependence of the mean-square pressure in the direct field. Furthermore, sound

pressure levels measured in the reverberant field will be consistently less then

those measured in the direct field of a source. The interior sound field is

further complicated when more then one element of the building shell acts as

a source of interior noise. In this situation, the level of the reverberant

field is determined by the total of the multiple sources while each source has

its own direct field and subsequent spatial variation.

83
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1 1 1

1

4 -\\ ^Q, = 8 - o ' w /^-Q0 = 4

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-2 - Y —

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- z \

o -4 \

—

CO

UJ \\K ^^**s. ^**'^*^'s^ - > \ ^Sn,^ ^"^^^^^^^ 1— -6 \^ ^\^^^^ ^"^^-^^^^..^^^^ < ^"*S»^ ^*'*>^^,^^ ^'^^^'"'^^^^ -J ^*'^Nh^ ^^^^ ^^

UJ _ ^**^^*»*^ ^^*''*''*'°*"*—-—^ ——^ — q: -8 -

~~-

—

_ -10 1 1 1 1 2 3 DISTANCE FROM SOURCE (ml

Figure 44. Computed sound pressure level as a function of distance

from the source of noise in a hypothetical room (typical

of those in the present study) for three values of the

directivity factor, Q .

84
In residential rooms, the interior sound field is still further

complicated by furnishings within the test room. Wall and floor coverings

such as drapes and rugs and upholstered furniture provide added sound

absorption relative to uncovered surfaces, so that sound reflected from

such absorptive surfaces is decreased in amplitude relative to that

reflected from uncovered surfaces, contributing further to spatial

variation. Furnishings also may increase spatial variation by shielding

some regions of the room from sound which would have arrived at a microphone position in the absence of these obstacles.

It was not the intent of the current study to quantify these sources

of spatial variation or the resultant measurement uncertainty in interior

sound pressure levels. However, from the NIR data obtained, spatial variation of sound pressure levels within individual receiving rooms was indicated.

For most of the test houses in the current study, the indicated spatial

variation was about 3 dB or less above 500 Hz. For one of the test houses.

No. 1, the indicated variation was slightly greater, being about 5 dB . As

with low-frequency spatial variation discussed in Sec. 6.2.1, uncertainty

due to high-frequency spatial variation can be reduced by spatially averaging

over a number of microphone positions.

6.2.2.2 Windows Open

The discussion above regarding the high frequency (above 315 to 500 Hz)

sound field within the receiving room is also applicable to measurements of

building sound isolation with the exterior windows (or doors) open. With

the windows open the interior sound field is strongly dominated by sound

transmitted through the open windows. An example of the indicated spatial

variation with windows open is presented in Fig. 45 for Test House No. 2,

where NIR values determined at the three interior listener microphone

positions are plotted. The approximate location of these three microphone

positions, relative to the open windows, is presented in Fig. 46.

In Fig. 45, substantial spatial variation is indicated both at low and

high frequency. The variation below 315 Hz is similar to that noted for

test houses with windows closed, as discussed in Sec. 6.2.1. Above 800 Hz,

the indicated spatial variation is considerably larger than that typically

observed with the windows closed. Above 1600 Hz, the indicated variation

is about 7 to 9 dB compared to about 2 to 4 dB with the windows closed for

this house (see Appendix C)

The increased high frequency spatial variation in Fig. 45 with windows

open can be readily interpreted using the high frequency assumption of ray

acoustics as described in Sec. 6.2.2.1. For the data of Fig. 45, the

acoustic rays emanating from the test vehicle nominally impinge at normal

incidence on the front of the building. Those rays which are not reflected

by the building propagate directly through the two open windows into the room until reflected by a wall. At sufficiently high frequencies, the rays

85
CO

50

40

C_3 g 30

LU

o

CO

20

g 10

1—I—

I—I

\—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—

r

A Mike position #1 • Mike position #2

Mike position #3

J L J L J L J L J L I I I

31.5 63 125 250 500 1000 2000

BAND CENTER FREQUENCY [Hz]

4000 8000

Figure 45. Noise Intrusion Reduction for the three listener positions

at Test House No. 2 with the windows open.

86
OPEN WINDOWS

TOWARD

ROADWAY

3.91m

MIKE POSITION

#2

e

MIKE POSITION #10

FLOOR/CEILING HEIGHT = 2.64 m

-6.06m

e MIKE POSITION #3

Figure 46 . Floor plan and listener position microphone locations

for Test House No. 1,

87
would be confined to a beam of cross-section approximately equal to that of

the window opening and extending across the room. Thus, the microphone at

position No. 3 would be directly exposed to the sound transmitted in this

beam and the measured level would have a correspondingly high value. For

microphone positions out of the beam formed by the open window, the measured

sound pressure level would be a combination of sound diffracted around the

edge of the open window and sound which is reflected from the interior

surfaces and furnishings of the rooms. As both the diffracted and reflected

sound are of less amplitude than the direct sound, microphone positions not

in the direct beam from the open windows are expected to correspond to

smaller values of sound pressure level. Such behavior is indicated in the

data of Fig. 44. The values of NIR determined at position No. 3 are significantly lower than those determined at positions No. 1 and No. 2, which

are not in the direct beam of the open window. Above 1600 Hz, the values

at position No. 3 are 6 to 9 dB lower than those for the other two positions.

For the 1/3-octave bands centered at 1000, 1250 and 1600 Hz, the values at

position No. 3 are also lower, but only by 2 to 5 dB . At these frequencies,

since the acoustic wavelengths are on the order of the window opening dimension,

diffraction is expected to be more pronounced than at higher frequencies.

From the data and discussion above, it is seen that the uncertainty in

the measurement of interior sound pressure level for high frequencies (above

800 Hz) is increased when the exterior windows are open relative to that

when the windows are closed. When the exterior windows are closed, variation

in sound pressure levels among listener position microphones was found to be

typically 3-4 dB. With the windows open, for one of the test houses, the

spatial variation was found to be as much as 9 dB at frequencies above 1600 Hz.

For measures of building sound isolation with windows or doors open, the

increased spatial variation, and hence measurement uncertainty, in the high

frequency should be considered.

6.2.3 Magnitude of Interior Sound Pressure Levels

A final source of certainty in the measurement of interior sound

pressure levels for the purposes of determining measures of building sound

isolation is the magnitude of the interior sound pressure levels. In

measuring interior levels, background noise of similar magnitude to the

noise produced by the exterior source may be present due to existing sources

of sound within the building. Also, due to the frequency dependency of the

sound isolation performance of building shells, measurement of the interior

sound pressure levels can require a large instrumentation dynamic range.

The uncertainty due to these two causes is particularly accentuated when

existing traffic outside of the building is used as the source of exterior

noise.

6.2.3.1 Dynamic Range Requirement

To examine the dynamic range requirements for the interior sound

pressure level measurement, a 1/3-octave band traffic noise equivalent

sound level spectrum was selected. This spectrum was taken from the

traffic noise data base obtained as part of the overall program of which

the current report was part [2] . The spectrum was chosen to represent

a mix of vehicle types traveling at low speed (posted limit of 64 km/hr.)

as might be encountered on an arterial street. The data are presented in

Fig. 47 as obtained 15 m from the roadway. In addition, the 1/3-octave

88
125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz)

Figure 47 . Traffic noise equivalent sound level spectra as measured

outdoors and as estimated indoors from average Noise

Intrusion Reduction values for the nine test houses. The

outdoor spectrum corresponds to a recording taken 15 m

from the center line of the near lane of Gude Drive with an average traffic speed of 64 km/hr and an average traffic

flow of 510 vehicles per hour (84.4% automobiles, 2.8%

medium trucks, and 12.8% heavy trucks) [2].

89
band spectrum obtained by subtracting the average NIR values reported in

Fig. 14 from the traffic levels is also presented in Fig. 47. The resultant, illustrative indoor spectrum can be used to consider the influence of

background noise on the interior sound pressure level measurement.

From Fig. 47 it is seen that although the outdoor spectrum covers a range in level of about 21 dB over the frequency range from 50 to 4000 Hz,

the indoor spectrum covers a range of about 40 dB. This requires that

the instrumentation used to measure the interior sound pressure levels have

a dynamic range of greater than 40 dB. This requirement is further extended

as temporal variations in the level will occur which require additional

dynamic range. For the traffic noise reported in Fig. 47, the level

exceeded 1 percent of the time in individual 1/3-octave bands was typically

10 dB greater than the equivalent level in the corresponding band. Thus

the total djmamic range required to measure the interior sound pressure

levels of Fig. 47 would be greater than 50 dB. With such dynamic range

requirements, particular attention must be given to the characteristics of

the instrumentation employed in measures of building sound isolation when

existing traffic is used as the source of exterior noise. If the dynamic

range requirement are not adequately addressed, uncertainty in the sound

isolation measure can occur due to the limitations of the instrumentation.

6.2.3.2 Background Noise within the Receiving Room

The range of background 1/3-octave band sound pressure levels measured

at each of the nine test houses is presented in Fig. 48. Typically, this

range has a magnitude on the order of 10 dB and indicates some frequency

dependence. Also presented in Fig. 48 is the indoor sound pressure levels

determined from the traffic noise equivalent sound levels of Fig. 46 and

the average NIR values of the current study. Although this resultant

indoor spectrum is not necessarily typical of that which occurs in any

given house, it does illustrate the difficulty which could occur due to the

presence of background noise in the receiving room when existing traffic

noise is used as the source of exterior noise. It is seen that, for this

indoor spectrum, the values are greater than the upper limit of the range

of background noise for frequencies below 2500 Hz. However, between 800

and 2500 Hz, the level due to traffic noise is only a few decibels greater

than the upper limit. If the traffic noise of Fig. 47 were actually measured

in a house with background noise levels similar to those of the upper limit

of the range of background noise from the nine test houses, the level measured

inside would be increased by the background noise above 800 Hz.

To reduce the uncertainty in building sound isolation resulting from

the presence of background noise within the receiving room, the background

noise due to sources within the building should be determined. However, if

the building is exposed to continual traffic or other environmental noise,

this background level cannot be readily determined due to the continuing

intrusion of the exterior noise. In this circumstance, the use of a loudspeaker

or other controllable exterior source of noise may be required to eliminate

the uncertainty created by background noise within the building.

90
60 T—

CO

3.

CM

50 -

40

I ' ' I

' '

I

Range of background levels

Traffic noise as estimated for indoors

00

00

oe

a.

00

00

30

20

10 1 L

31.5 63 125 250 500 1000 2000

BAND CENTER FREQUENCY (Hz)

4000 8000

Figure 48 . Range of 1/3-octave band sound pressure levels of

background noise for the nine test houses compared with

estimated indoor spectrum for exterior traffic noise

(from Fig. 47) .

91
7. References

[1] Highway Noise Criteria, FHWA Order No. 630154 (9 September 1976).

[2] Flynn, D. R. , Voorhees, C. R. , and Yaniv, S. L. , Highway Noise

Criteria Study: Traffic Noise Data Base, NBS Technical Note 1113-1

(National Bureau of Standards, Washington, D.C., 1980)

[3] Standard Definitions of Terms Relating to Environmental Acoustics,

ANSI/ASTM C634-79a, pp 333-338, Part 18, 1979 Annual Book of ASTM

Standards (American Society for Testing and Materials, Philadelphia,

Pa., 1979).

[4] Measurement of Sound Insulation in Buildings and of Building Elements

Part V: Field Measurements of Airborne Sound Insulation of Facade

Elements and Facades, ISO 140, Part V (International Organization

for Standardization, Geneva, Switzerland, 1978).

[5] Proposed Standard Recommended Practice for Field Measurement of

Airborne Sound Insulation of Building Facades and Facade Elements,

8th Draft (American Society for Testing and Materials, Philadelphia,

Pa., January 1980)

.

[6] Standard Test Method for Measurement of Airborne Sound Insulation

in Buildings, Annex Al, ANSI/ASTM E336-77, pp 914-933, Part 18, 1979

Annual Book of ASTM Standards (American Society for Testing and

Materials, Philadelphia, Pa., 1979).

[7] Study of Soundproofing Public Buildings Near Airports, Report No.

DOT-F4A-AEQ-77-9 (Federal Aviation Administration, Office of

Environmental Quality, Washington, D.C., 1977).

[8] Noise Environment of Urban and Suburban Areas (Federal Housing

Administration, Department of Housing and Urban Development,

Washington, D. C, 1967).

[9] Bishop, D. E., Reduction of aircraft noise measured in several

school, motel, and residential rooms, J. Acoust. Soc. Am. 39 , 907-913 (1966)

.

[10] Scholes, W. E., and Parkin, P. H., The insulation of houses against

noise from aircraft in flight, Appl. Acoust. 1^, 37-46 (1968).

[11] Ford, R. I., and Kerry, G. , Insulating one house against aircraft

noise, Appl. Acoust. 7_, 193-211 (1974).

[12] Leventhall, H. G., Simplified Methods for the Measurement of Airborne

Sound Isolation in Buildings, Working Group 51 on Acoustics of the

International Council on Building (Chelsea College, University of

London, Department of Physics, London, June 1977).

92
[13] Home Soundproofing Pilot Project for the Los Angeles Department of

Airports, Report No. WCR 70-1 (Wyle Laboratories, El Segundo, Ca.,

1970).

[14] Sato, H., On the outdoor noise insulation of dwellings — particularly

on the results of field measurements, Proc. 6th International Congress on Acoustics, Vol. IV, Paper F-5-16 (Tokyo, Japan, 1968).

[15] Driscoll, D. A., Dulin, J. P., and Keast, D. N., Attenuation of

northern dwellings to a linear source of noise, J. Acoust. Soc. Am.

^, Suppl. No. 1, 58 (1978).

[16] Sieknan, W. , Yerges, J. F. , and Yerges, L. F., A simplified field

sound transmission test, Sound and Vibration, _5(10) , 17-22 (October 1971)

[17] Young, J. R., Attenuation of Aircraft Noise by Wood-Sided and Brick

Veneered Frame Houses, Report NASA CR-1637 (National Aeronautics and

Space Administration, Washington, D. C, 1970).

[18] Sutherland, L. C, Braden, M. H., and Colman, R. , A Program for the

Measurement of Environmental Noise in the Community and Its Associated

Human Response, Volume I. A Feasibility Test of Measurement Techniques,

Report No. DOT-TST-74-5 (Office of Noise Abatement, Department of

Transportation, Washington, D. C, 1973).

[19] House Noise-Reduction Measurements for Use in Studies of Aircraft

Flyover Noise, Aerospace Information Report 1081 (Society of Automotive

Engineers, Warrendale, Pa., October 1971).

[20] Mulholland, K. A., Method for measuring the sound insulation of

facades: Factors to be considered, Appl. Acoust. 4^, 279-286 (1971).

[21] Lewis, P. T., A method for field measurement of the transmission

loss of building facades, J. Sound Vibrational, 127-141 (1974).

[22] Beranek, L. L. (Editor), Noise and Vibration Control (McGraw-Hill,

New York, 1971)

[23] Marsh, J. A., The airborne sound insulation of glass. Part 1, Appl.

Acoust. 4_, 55-70 (1971); Part 2, Appl. Acoust. ^, 131-154 (1971); and

Part 3, Appl. Acoust. 4_, 175-191 (1971). Also available, in a single

report, as Environmental Advisory Service 4 (Pilkington Bros. Ltd.,

St. Helena, Lanes., England, 197 0).

[24] Rindel, J. H., Transmission of Traffic Noise Through Windows, Report

No. 9 (Technical University of Denmark, Acoustics Laboratory,

Denmark, 1975).

[25] deLange, P. A., Sound insulation of glazing with respect to traffic

noise, Appl. Acoust. 1_, 215-236 (1969).

[26] Sharp, B. H. , Davy, B. A., and Mange, G. E., The Assessment of Noise

Attenuation Measures for External Noise, Wyle Research Report No. WR

76-3 (Department of Housing and Urban Development, Washington, D. C,

April 1976) .

93
[27] Methods for Improving the Noise Insulation of Houses with Respect

to Aircraft Noise, Report No. 1387 (Bolt Beranek and Newman Inc.,

Cambridge, Ma. , 1966)

.

[28] Bolt Beranek and Newman Inc., Noise in Urban Areas: Results of

Field Studies (U. S. Department of Housing and Urban Development,

Washington, D. C, 1967).

[29] Sabine, H. J., Lacher, M. M. , Flynn, D. R. , and Quindry, T. L.

,

Acoustical and Thenncil Performance of Exterior Residential Walls,

Doors, and Windows, NBS Building Science Series 77 (National

Bureau of Standards, Washington, D. C, 1975).

[30] Kerry, G. , and Ford, R. D. , The field performance of partially open

dual glazing, Appl. Acoust. 1_, IVh-lll (1974).

[31] Flynn, D. R. , Leasure, W. A., Jr., Rubin, A. I., and Cadoff, M. A.,

Noise Emission Measurements for Regulatory Purposes, NBS Handbook

122 (National Bureau of Standards, Washington, D. C, 1977).

[32] Jones, R. E., Effects of flanking and test environment on labfield correlations of airborne sound insulation, J. Acoust. Soc.

Am. 57, 1138-1149 (1975).

[33] Donavan, P. R. , Sound Propagation in Urban Spaces, Sc. D. Thesis

(Massachusetts Institute of Technology, Department of Mechanical

Engineering, Cambridge, Ma., January 1976).

[34] The Use of Architectural Acoustical Materials - Theory and

Practice, Fourth Edition (Acoustical and Insulating Materials

Association, New York, 1972)

.

[35] Wagner, L. R., Acoustic Reflection from Rough Surfaces, S. M.

Thesis (Massachusetts Institute of Technology, Department of

Mechanical Engineering, Cambridge, Ma., August 1974).

[36] Morse, P. E., and Ingard, K. U. , Theoretical Acoustics (McGrawHill, New York, 1968).

94
Appendix A. Floor Plans For The Nine Test Houses

Contained In this Appendix are the room floor plans for the nine test

houses for which Noise Intrusion Reduction values were obtained as described

in Section 3. For Test House No. 8, an interior elevation is also presented

as the ceiling and floor are not parallel. The window dimensions are indicated in the figures using the following symbols:

a = distance from the floor to the base of the window opening

h = height of the window opening

b = distance from the ceiling to the top of the window opening.

The symbol H in the figures is used to denote the floor to ceiling dimension.

The construction details of each of the nine test houses are summarized in

Table 1 of Section 3.2. The top of each figure corresponds to the side of

the house which faces the road.

A-1
a = .69, h = 1.32, b = .43

Figure Al. Floor plan for Test House No. 1.

I 1 I I [ c^ '

a

= .71, h = 1.55, b = .38

464- .58 -I .94 —I-.58-I— .94 1-.58-4 -94 i— .58-I-.48-

6.06

H = 2.64m

3.91

.12 -4.14- -j 1.80 1 L

^

a

= .18, h = 2.06,

b = .40

Figure A2 . Floor plan for Test House No. 2

A-2
a = .69, h = 1.32, b = .41

-h = 2.03

Figure A3. Floor plan for Test House No. 3.

a = .66, h = 1.40, b = .38

Figure A4 . Floor plan for Test House No. 4.

A-3
h = 2.03

Figure A5. Floor plan for Test House No. 5,

1.98-

.76

1.65 4.67

1.27

-.94-

air conditioner ^^

.84-

-a = .71, h = 1.35, b = .36 t

a = .71, h = 1.35, b = .36

I * [ 1.42- -^.84^- 1.98- 7.06-

H = 2.42m

3.60

L07-

-2.18 \ .94

2.99

-1.19

j .89 1-

h = 2.03

1.47

h = 2.42

Figure A5. Floor plan for Test House No. 6,

A-4
a = .64, h = 1.52, b = .28

a = 0, h = 2.04, b = .40

1. FRONT WINDOW CANNOT BE OPENED

2. EXTERNAL FRONT DOOR (detailed on left! SUBSTITUTED AS AN

',"2 ACOUSTICAL PATH

Figure A7 . Floor plan for Test House No. 7

h = 2.03

-.434—91

-a = .23, h = 2.03

J

* ==r

1.27 1-

-6.47-

-3.68-^

a = .23, h = 2.03, b = .38-

.23-

.94

3.76

a = .23, h = 2.03, b = .38-

|-.36-f 2.67

1.65

.94

Figure A8 . Floor plan for Test House No. 8,

A-5
Figure A9. Interior elevation for Test House No. 8,

h = 2.03

a = .20, h = 1.83, b = .41

Figure AlO. Floor plan for Test House No. 9.

A6
Appendix B. Values of Noise Intrusion Reduction Determined

With Simultaneously Occurring Outdoor and Indoor Sound Pressure Levels

The NIR values presented in this Appendix were obtained from the sound

pressure levels measured simultaneously at the exterior and interior

microphone positions and correspond to Data Set No. 1 of Section 3.3. The

1/3-octave band values of NIR from 50 to 4000 Hz obtained with this data

reduction technique are presented in Tables Bl through B18. In each table

values of the average outside sound pressure level at the two 3-m microphone

positions, NIR values at the interior reference position, and NIR values at

each of the three interior listener positions are presented. The average NIR

for the three listener positions is also presented as calculated from Eq. (4)

of Section 4.1.1.

The values reported in Tables B1-B8 and B13-B18 were determined using the

sound pressure levels which occurred at the instant of maximum interior

A-weighted sound level for the reference position microphone. The values

presented in Tables B9-B12 for Test House No. 8 were determined using

simultaneously-occurring sound pressure levels during a passby of the test

vehicle at four instances other than when the maximum interior level occurred.

Tables B13-B17 present the values determined for five different passbys of

Test House No. 5. Table B18 presents values obtained with the front door of

Test House No. 9 open.

Also included in this Appendix are plots of the NIR values averaged over

the three listener positions for each of the nine test houses. These are presented in Figures B1-B9.

B-1
Table Bl. Noise Intrusion Reduction Data Set No. 1, Test House No. 1

1/3-

Octave

Band Average

NIR, dB

Interior Listener Listener Listener Average

of

Listener

Positions

Center Exterior Reference Position Position Position

Frequency

,

Hz

Level, dB Position No.l No.

2

No.

3

50 59.8 8.8 7.3 9.5 6.5 7.6

63 61.2 17.6 15.4 13.4 12.5 13.6

80 58.4 18.2 23.4 17.6 22.6 20.4

100 61.9 22.2 24.4 23.1 21.4 22.8

125 62.3 20.3 23.0 21.7 23.0 22.5

160 61.6 23.6 19.3 18.6 16.6 18.0

200 61.0 27.0 22.5 23.7 24.3 23.4

250 66.0 27.0 31.0 30.4 28.0 29.6

315 66.9 25.7 31.2 29.3 27.6 29.1

400 62.1 30.9 27.8 27.3 26.7 27.2

500 63.3 28.3 29.3 27.5 24.8 26.8

630 62.7 26.0 28.4 26.9 25.2 26.6

800 63.3 29.9 32.8 27.0 29.2 29.1

1000 63.3 29.8 32.8 29.0 29.0 29.9

1250 64.4 28.7 33.7 29.6 32.2 31.5

1600 64.4 33.4 35.1 32.1 35.5 34.0

2000 60.8 32.8 34.5 31.5 31.8 32.4

2500 56.6 30.2 - 29.0 29.3 29.1

3150 55.0 29.6 - 29.4 28.5 28.9

4000 52.5 - - 27.9 27.2 27.5

B-2
Table B2 . Noise Intrusion Reduction Data Set No.l, Test House No.

1/3-

Octave

Band

Cent er

NIR, DB

Average

Exterior

Interior

Reference

Listener

Position

Listener

Position

Listener

Position

Average

of

Listener

Positions Frequency* Level, dB Position No.l No.

No.

50 69.8 14.8 19.2 21.8 20.0 20.2

63 61.6 12.3 23.0 14.6 21.1 18.0

80 73.1 23.6 24.8 14.4 19.6 17.7

100 74.8 31.3 38.4 28.4 26.6 29.0

125 76.4 26.2 24.8 28.2 28.2 26.8

160 69.8 23.0 22.2 23.8 27.4 24.0

200 78.4 20.8 27.4 21.4 26.3 24.2

250 69.5 24.7 27.9 26.3 24.3 25.9

315 59.8 22.8 25.0 26.4 21.5 23.8

400 56.6 19.6 20.6 22.9 26.4 22.7

500 61.7 27.2 29.1 28.3 23.9 26.5

630 59.1 24.3 29.5 29.9 26.9 28.6

800 65.8 37.6 32.2 31.4 31.0 31.5

1000 69.0 34.5 34.2 36.0 34.2 34.7

1250 70.8 33.3 33.0 37.6 36.8 35.3

1600 68.9 32.1 32.1 37.7 35.4 34.5

2000 70.0 34.2 30.7 37.8 36.0 33.7

2500 67.2 31.4 28.9 35.0 35.7 32.0

3150 61.6 28.8 28.3 32.6 30.8 30.2

4000 59.5 30.7 30.5 33.8 32.3 32.0

B-3
Table R3. Noise Intrusion Reduction Data Set No.l, Test House No.

3

1/3-

Octave

Band Average

NIR, dB

Interior Listener Listener Listener Average

of

Listener

Positions

Center Exterior Reference Position Position Position

Frequency,

Hz

Level, dB Position No.l No. 2 No. 3

50 52.5 16.0 19.5 - - -

63 63.4 27.6 28.6 25.3 26.5 26.6

80 53.7 24.0 16.9 22.4 16.5 17.9

100 70.6 27.1 30.4 29.6 29.4 29.8

125 62.5 26.5 25.7 29.2 25.5 26.5

160 76.4 19.1 20.9 22.6 21.4 21.6

200 64.3 9.6 18.5 21.7 14.9 17.5

250 57.0 15.3 26.0 27.0 22.6 24.8

315 52.9 25.9 _ - - -

400 46.3 - - - - -

500 46.2 - - - - -

630 47.2 - - - - -

800 49.9 - - - - -

1000 56.4 30.7 31.4 32.6 - 32.0

1250 61.2 35.7 35.4 35.4 35.0 35.3

1600 64.0 37.3 38.0 38.4 38.3 38.2

2000 64.0 33.5 34.0 35.2 35.3 34.8

2500 64.8 34.5 35.0 36.2 37.4 36.1

3150 62.3 35.8 36.5 36.3 35.9 36.2

4000 57.2 - - - — ^

B-4
Table B4. Noise Intrusion Reduction, Data Set No.l, Test Eouse No.

1/3- NIR, dB

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No. 3

Average

of

Listener

Positions

50 66.9 14.9 16.9 13.4 17.4 15.5

63 63.0 14.2 15.5 20.2 23.0 18.5

80 72.2 16.9 14.2 24.7 25.0 18.3

100 66.9 18.3 22.4 20.9 20.1 21.0

125 78.8 19.5 26.3 19.2 17.3 19.6

160 68.1 22.3 26.3 20.9 19.1 21.2

200 74.8 16.8 23.6 22.6 21.0 22.3

250 69.6 16.0 29.8 26.8 22.6 25.4

315 65.6 18.0 26.5 31.8 25.4 27.1

400 66.4 23.6 32.2 33.4 31.6 32.3

500 63.7 25.9 32.9 27.5 31.2 29.9

630 60.9 26.1 32.1 31.7 33.9 32.5

800 66.6 29.6 37.1 33.4 35.1 34.9

1000 70.9 32.3 40.1 35.7 37.4 37.4

1250 75.0 33.7 40.2 38.0 39.5 39.1

1600 73.2 34.4 42.7 40.2 41.7 41.4

2000 68.6 32.3 36.8 36.8 33.8 35.6

2500 69.8 32.8 38.8 38.8 36.3 37.8

3150 69.4 34.8 40.6 38.4 37.9 38.8

4000 65.3 33.0

-

38.8 37.3 36.3 37.3

B-5
Table B5. Noise Intrusion Reduction, Data Set No.l, Test House No.

5

1/3- NIR, dB

Octave

Band Average Interior Listener Listener Listener Average

of

Listener

Positions

Center Exterior Reference Position Position Position

Frequency,

Hz

Level, dB Position No.l No.

2

No. 3

50 74.3 12.6 13.3 12.1 10.1 11.6

63 73.9 22.7 16.9 19.2 22.9 19.0

80 68.4 23.7 21.2 18.4 15.2 17.6

100 72.2 17.2 27.2 14.0 21.7 17.9

125 64.9 21.2 23.7 20.9 23.9 22.6

160 68.0 17.3 24.8 21.5 21.3 22.3

200 70.9 18.7 25.7 23.9 19.4 22.2

250 64.8 28.6 30.3 28.3 28.6 29.0

315 63.5 28.8 33.3 31.0 30.5 31.4

400 62.6 25.6 33.6 30.6 29.9 31.1

500 60.5 30.8 35.3 32.5 32.3 33.2

630 59.9 33.2 35.4 35.9 34.7 35.3

800 63.7 35.0 36.2 35.7 37.0 36.8

1000 68.1 35.9 36.1 37.4 37.1 36.8

1250 71.9 33.9 36.2 36.2 35.4 35.9

1600 71.7 36.5 37.7 36.0 35.5 36.3

2000 66.8 31.1 32.3 32.1 31.3 31.9

2500 68.5 35.0 35.5 34.3 32.5 33.9

3150 64.7 35.0 33.7 33.7 30.5 33.6

4000 60.8 35.8 34.6 34.8 34.1 34.5

B-6
Table B6. Noise Intrusion Reduction, Data Set No.l, Test House No .

1/3-

Octave

Band Average

NIR, dB

Interior Listener Listener Listener Average

of

Listener

Positions

Center Exterior Reference Position Position Position

Frequency,

Hz

Level, dB Position No.l No.

No.

50 69.0 11.2 14.3 19.2 11.8 14.2

63 66.9 18.4 21.9 22.9 17.0 19.8

80 66.1 8.6 10.1 9.7 12.2 10.5

100 63.6 6.1 8.6 8.4 9.7 8.9

125 74.9 28.9 23.6 25.1 27.4 25.1

160 69.9 23.9 16.9 21.4 21.0 19.3

200 67.1 20.9 21.8 21.3 24.9 22.4

250 61.9 19.4 20.9 20.7 19.0 20.1

315 63.6 20.8 30.1 30.1 23.4 26.6

400 61.8 23.8 29.3 29.6 29.1 29.3

500 58.3 28.1 29.6 30.1 29.1 29.6

630 56.8 27.8 27.8 27.8 30.3 28.5

800 61.0 29.8 30.7 31.5 32.8 31.6

1000 63.4 29.6 30.4 30.9 32.7 31.2

1250 67.7 29.5 33.7 29.5 33.2 31.7

1600 69.8 34.0 35.3 33.3 34.9 34.4

2000 69.5 32.3 32.5 28.3 34.0 30.9

2500 69.5 35.0 37.0 35.0 38.0 36.5

3150 65.4 33.4 34.9 35.6 33.9 34.7

4000 59.7 32.7 30.7 30.9 33.2 31.5

B-7
Table B7. Noise Intrusion Reduction, Data Set No.l, Test House No.

7

1/3- NIR, dB

Octave

Average

of

Listener

Positions

Band Average Interior Listener Listener Listener

Center Exterior Reference Position Position Position

Frequency,

Hz

Level, dB Position No.l No.

2

No.

3

50 69.1 13.6 12.3 15.3 15.3 14.1

63 71.2 13.2 12.7 16.0 15.0 14.3

80 63.1 14.1 11.9 17.9 18.1 14.9

100 68.9 14.4 16.4 13.4 22.4 16.1

125 67.0 30.5 30.2 20.2 19.5 21.4

160 67.4 28.2 31.9 34.9 23.9 27.7

200 78.1 32.3 36.3 39.6 24.9 29.2

250 66.0 28.0 28.5 22.0 29.8 25.3

315 60.8 25.8 30.3 26.8 28.6 28.3

400 62.2 25.7 35.4 30.4 27.7 30.1

500 58.0 30.5 31.2 28.5 29.8 29.7

630 57.0 31.2 32.8 33.0 29.8 31.6

800 58.9 28.1 31.9 27.4 29.1 29.1

1000 62.9 30.7 31.9 30.7 30.9 31.1

1250 66.2 31.0 30.7 31.4 30.7 30.9

1600 68.0 32.5 33.8 32.2 32.8 32.9

2000 67.5 37.7 36.7 36.5 35.7 36.3

2500 63.0 40.0 38.2 38.5 37.8 38.2

3150 57.5 - - - - -

4000 51.2

-

- - - -

B-8
Table B8. Noise Intrusion Reduction, Data Set No.l, Test House No.

1/3-

Octave

Band

Center

Average

Exterior

NIR, dB

Interior

Reference

Listener

Position

Listener

Position

Listener

Position

Average

of

Listener

Positions Frequency,

Hz

Level, dB Position No.l No. 2 No. 3

50 55.9 15.1 18.1 15.9 11.9 14.5

63 64.7 14.9 26.1 22.0 15.2 18.9

80 63.8 14.7 11.8 11.3 22.8 13.1

100 64.4 16.1 14.4 12.1 13.6 13.3

125 69.4 17.8 20.6 18.4 19.2 19.3

160 66.1 17.5 17.9 20.4 26.6 20.4

200 63.6 19.3 24.6 27.1 31.1 26.9

250 64.5 20.2 26.5 25.5 26.0 26.0

315 72.7 27.9 25.9 29.0 31.5 28.2

400 63.4 24.4 23.2 23.1 25.2 23.7

500 62.5 27.5 30.3 24.0 30.0 27.1

630 63.2 27.2 30.7 32.7 30.7 31.3

800 64.9 29.9 32.9 28.2 31.4 30.4

1000 67.8 29.5 32.3 30.1 33.3 31.7

1250 67.0 28.7 31.0 28.3 30.8 29.9

1600 66.0 25.4 29.0 28.7 29.2 29.0

2000 62.4 24.6 27.9 27.9 28.6 28.1

2500 60.4 31.8 33.2 29.7 31.4 31.2

3150 58.5 33.5 34.7 32.2 32.7 33.1

4000 55.9 32.9 - 32.6 -

B-9
Table B9 . Noxse Intrusion Reciuction, Data Set No.l, Test House No. 8,

2.8 Seconds Before Maximum Interior A-Weighted Sound Level

1/3-

Octave

Band

Center

Average

Exterior

NIR, dB

Interior

Reference

Listener

Position

Listener

Position

Listener

Position

Average

of

Listener

Positions Frequency,

Hz

Level , dB Position No.l No.

2

No.

3

50 52.9 13.3 9.7 7.9 7.7 8.3

63 51.4 23.7 18.9 15.7 11.9 14.6

80 60.4 22.9 16.9 20.1 11.6 14.8

100 63.1 22.3 12.9 14.8 27.3 15.4

125 67.7 16.4 14.5 9.7 14.5 12.3

160 63.4 19.8 19.6 15.4 22.4 18.2

200 56.4 21.8 16.4 19.9 17.2 17.6

250 65.0 28.4 25.0 27.7 24.2 25.4

315 54.1 24.3 24.1 25.4 23.1 24.1

400 48.9 22.3 25.1 23.4 24.7 24.3

500 49.4 22.1 22.4 25.4 26.6 24.4

630 50.8 24.0 26.0 26.1 26.8 26.3

800 48.8 24.0 26.3 23.5 23.3 24.2

1000 50.1 25.1 26.6 25.6 25.1 25.7

1250 52.2 25.9 26.7 27.2 26.4 26.8

1600 53.8 23.0 26.0 25.1 26.0 25.7

2000 52.3 24.3 27.1 26.8 26.3 26.7

2500 51.8 25.5 27.1 27.3 26.6 27.0

3150 50.7 27.4 - 27.2 27.7 27.5

4000 48.3 - 25.1 22.6 20.1 21.3

B-10
Table BIO. Noise Intrusion Reduction, Data Test No.l, Test House No. 8,

1.4 Seconds Before Maximum Interior A-Weighted Sound Level

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No. 3

Average

of

Listener

Positions

50 54.7 17.3 16.3 9.7 11.0 11.5

63 61.1 20.6 23.5 10.1 18.9 14.2

80 65.8 25.7 8.0 13.5 19.3 11.5

100 62.9 17.6 7.9 15.2 17.4 11.5

125 70.3 16.7 12.1 24.0 18.8 15.8

160 74.2 24.2 20.4 19.9 19.0 19.7

200 62.4 21.8 27.6 14.4 19.4 17.8

250 63.9 21.9 28.4 24.9 26.1 26.2

315 68.9 27.1 26.9 25.9 28.7 27.0

400 58.1 26.5 28.6 27.8 27.3 27.9

500 57.5 25.5 26.0 28.8 30.3 28.0

630 59.3 30.7 31.3 31.8 32.3 31.8

800 57.0 29.7 29.8 29.0 30.2 29.6

1000 58.4 27.4 27.9 28.1 28.2 28.1

1250 60.1 25.1 29.9 30.1 28.6 29.5

1600 62.0 25.4 30.0 28.7 30.0 29.5

2000 59.4 26.1 27.9 29.4 29.6 28.9

2500 58.0 30.2 29.8 28.0 29.8 29.1

3150 57.5 33.2 34.3 31.5 32.5 32.6

4000 56.0 33.0 33.8 32.3 33.2 33.1

B-11
Table Bll. Noise Intrusion Reduction, Data Set No.l, Test House No. 8,

l.A Seconds After Maximum Interior Sound Level

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

3

Average

of

Listener

Positions

50 61.3 11.7 19.8 16.8 14.8 16.7

63 66.1 11.1 21.6 15.1 14.3 16.0

80 59.5 17.7 16.3 12.8 19.0 15.3

100 66.7 17.4 21.7 22.2 29.4 23.3

125 72.4 17.1 21.6 31.4 30.4 25.4

160 68.9 16.9 20.4 25.4 25.9 23.1

200 62.6 17.8 21.6 25.6 26.8 24.1

250 65.7 23.7 25.2 27.2 29.9 27.0

315 66.1 25.1 28.1 27.8 33.6 29.2

400 59.9 25.9 29.1 30.6 31.1 30.2

500 54.8 25.8 25.3 27.5 25.8 26.1

630 62.4 35.6 36.6 31.1 35.4 33.7

800 61.5 29.7 33.0 33.5 34.0 33.5

1000 67.7 28.9 33.2 34.2 34.7 34.0

1250 70.1 28.5 32.3 34.8 35.6 34.0

1600 70.4 29.4 32.9 34.4 35.4 34.1

2000 69.7 29.9 34.2 37.4 38.5 36.3

2500 66.9 35.6 38.4 39.9 39.7 39.3

3150 62.7 36.1 37.7 38.4 38.9 38.3

4000 58.4 34.6

B-12
Table B12 . Noise Intrusion Reduction, Data Set No.l, Test House No. 8,

2.8 Seconds After Maximum A-Weigb.ted Interior Sound Level

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

NIR, dB

T

Interior

Reference

Level, dB Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No. 3

Average

of

Listener

Positions

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

64.7

66.6

63.0

66.4

69.3

69.9

67.6

71.2

65.3

59.7

54.8

57.9

58.6

60.0

59.8

61.1

59.0

58.2

55.4

51.2

24.1

23.8

18.0

21.6

22.3

21.9

25.0

23.6

19.0

25.1

25.2

29.1

25.0

25.7

25.8

27.5

26.4

30.9

30.6

26.9

19.7

28.3

4.0

12.6

14.1

19.9

25.2

26.7

24.1

26.5

29.6

31.9

29.1

30.2

29.3

30.8

30.0

32.4

32.2

17.2

18.3

6.7

19.4

24.8

25.4

26.1

25.7

25.6

29.7

28.3

32.2

31.3

29.3

30.8

30.4

32.5

32.5

32.1

24.7

21.0

23.4

23.3

21.7

29.6

32.7

26.1

29.7

29.0

32.4

32.6

30.8

28.8

32.6

32.8

34.0

32.2

19.6

20.9

6.8

16.3

18.1

21.8

26.6

27.5

25.2

28.4

28.9

32.2

30.8

30.1

29.6

31.2

31.6

32.9

32.2

B-13
Table B13. Noise Intrusion Reduction, Data Set No.l, Test House No. 9,

Passby No.l

1/3- NIR, dB

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

3

Average

of

Listener

Positions

50 68.5 14.5 19.3 9.7 18.8 13.6

63 63.8 13.5 16.9 11.8 20.6 15.0

80 68.5 18.0 11.1 13.0 16.1 12.9

100 72.3 17.0 21.6 16.8 16.6 17.8

125 70.3 23.8 26.6 24.5 19.9 22.7

160 69.3 16.3 17.1 16.3 25.6 18.2

200 72.3 16.8 19.1 28.3 26.4 22.7

250 71.7 19.7 24.7 31.2 30.3 27.7

315 70.2 20.7 28.4 29.4 24.2 26.7

400 72.1 21.8 29.7 28.3 24.4 26.9

500 70.3 27.6 30.6 30.1 24.9 27.7

630 68.1 28.8 33.9 33.1 30.9 32.4

800 74.2 31.9 34.0 33.7 33.2 33.6

1000 80.8 32.8 36.1 34.3 32.4 34.0

1250 83.3 38.0 39.6 37.3 36.1 37.4

1600 83.1 38.6 38.1 39.3 37.7 38.3

2000 82.8 40.5 40.6 42.0 41.1 41.2

2500 75.6 38.1 37.9 39.4 37.2 38.1

3150 70.0 35.0 35.0 35.2 33.8 34.6

4000 68.4 37.7 38.4 39.2 37.2 38.2

B-14
Table B14. Noise Intrusion Reduction, Data Set No.l, Test Eouse No. 9,

Passby No.

1/3- . Octave

Band

Center

Frequency*

Hz

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No. 3

Average

of

Listener

Positions

50 64.0 20.3 20.3 11.5 17.8 14.9

63 68.2 16.5 15.0 15.2 23.8 16.6

80 72.5 20.8 17.8 19.3 21.5 19.3

100 71.2 24.9 24.8 24.7 24.0 24.5

125 81.8 27.5 27.1 30.6 25.8 27.4

160 70.9 19.4 22.2 25.1 26.9 24.3

200 69.9 20.4 18.9 24.4 29.9 22.3

250 68.2 23.5 23.2 26.4 24.8 24.6

315 67.7 21.2 24.5 27.9 22.3 24.3

400 70.9 22.9 28.2 27.9 22.7 25.5

500 69.9 26.4 27.2 28.1 21.5 24.5

630 64.4 27.9 30.2 30.9 29.2 30.1

800 72.5 29.1 31.8 32.0 30.8 31.5

1000 79.5 30.0 31.8 31.3 30.3 31.1

1250 80.7 34.2 36.7 35.2 33.5 34.9

1600 77.4 36.7 35.4 36.6 35.2 35.7

2000 74.8 37.8 37.1 39.3 37.1 37.7

2500 70.3 37.0 36.9 38.3 34.3 36.2

3150 64.9 33.4 34.9 36.4 30.5 33.2

4000 64.6 35.9 37.2 37.8 - 37.5

B-15
Table B15. Noise Intrusion Reduction, Data Set No.l, No. 9,

Passby No.

3

1/3-

Octave

Band Average

NIR, dB

Interior Listener Listener Listener Average

of

Listener

Positions

Center Exterior Reference Position Position Position

Frequency

,

Hz

Level, dB Position No.l No.

2

No.

3

50 70.0 16.0 24.6 7.2 16.3 11.4

63 68.8 15.8 13.8 13.8 26.1 15.4

80 74.1 19.4 16.9 17.9 18.1 17.6

100 70.9 21.6 17.9 18.7 17.9 18.2

125 77.8 22.5 24.1 24.0 25.6 24.5

160 73.2 18.9 22.0 21.0 25.2 22.4

200 71.5 21.0 16.3 22.5 24.5 19.6

250 69.9 20.6 19.9 26.4 25.2 22.9

315 70.4 22.7 22.7 29.9 23.0 24.2

400 71.8 25.8 28.6 30.8 24.1 26.9

500 69.3 28.3 27.9 28.3 21.6 24.8

630 65.9 27.6 31.7 30.9 30.7 31.1

800 73.6 29.9 32.9 33.6 30.6 32.2

1000 78.3 29.8 33.3 30.8 28.1 30.2

1250 82.9 36.6 37.2 34.7 33.7 35.0

1600 80.2 35.2 35.8 38.2 35.0 36.1

2000 78.3 35.3 38.1 39.5 38.1 38.5

2500 73.6 35.3 37.6 39.1 35.6 37.2

3150 67.4 30.1 34.7 35.6 31.4 33.5

4000 66.5 35.0 37.5 38.3 " 37.9

B-16
Table B16. Noise Intrusion Reduction, Data Set No.l, Test House No. 9. Passby No.

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No. 3

Average

of

Listener

Positions

50 65.1 21.1 19.7 11.1 17.7 14.5

63 68.6 16.6 16.4 16.1 22.6 17.5

80 76.5 22.8 20.1 18.5 21.8 19.9

100 74.7 28.7 26.3 26.7 22.7 24.8

125 88.8 26.3 29.8 36.3 27.4 29.9

160 75.2 23.2 25.2 25.7 28.0 26.1

200 72.1 22.4 18.9 26.9 24.1 22.0

250 72.0 24.0 22.0 32.0 26.8 25.2

315 72.7 21.2 28.7 33.2 29.3 30.0

400 69.5 21.5 27.8 28.7 23.5 26.0

500 70.7 27.4 29.5 30.2 23.3 26.5

630 67.0 30.3 33.0 31.0 32.0 31.9

800 72.8 30.5 33.6 33.3 32.8 33.2

1000 81.0 30.7 35.0 33.0 29.8 32.1

1250 81.0 36.5 37.0 34.8 31.8 34.0

ISOO 79.8 37.8 35.6 36.8 34.6 35.6

2000 79.8 39.8 39.4 40.3 38.6 39.4

2500 72.3 37.6 36.9 38.5 34.1 36.1

3150 67.8 34.1 35.4 35.3 31.6 33.7

4000 66.0 36.5 37.8 39.2 — 38.4

B-17
B17. Noise Intrusion Reduction, Data Set No.l, Test House No. 9,

Passby No.

5

1/3-

Octave

Band Average

NIR, dB

Interior Listener Listener Listener 1 Average

of

Listener

Positions

Center Exterior Reference Position Position Position

Frequency,

Hz

Level, dB Position No.l No.

2

No.

3

50 65.9 18.9 20.9 9.9 17.5 13.7

63 68.1 16.6 15.7 14.3 22.9 16.4

80 71.2 16.5 16.0 18.7 20.5 18.0

100 70.4 16.9 17.7 20.9 19.2 19.1

125 72.9 26.2 25.9 23.4 24.5 24.5

160 74.5 20.2 22.8 23.7 25.5 23.9

200 72.4 21.7 16.2 27.4 28.2 20.4

250 71.7 23.2 23.5 26.7 23.3 24.2

315 71.7 21.4 25.7 31.6 23.9 26.0

400 71.8 21.5 28.6 30.3 24.6 27.2

500 71.1 28.6 26.9 32.1 22.4 25.5

630 64.7 28.0 29.5 29.5 28.5 29.1

800 71.6 30.9 32.2 33.6 30.4 31.9

1000 78.5 32.2 34.5 32.3 30.8 32.3

1250 82.5 36.2 39.8 38.0 35.8 37.6

1600 82.6 38.3 39.9 39.4 39.9 39.7

2000 81.1 39.1 40.9 41.6 41.9 41.4

2500 75.3 38.3 41.3 40.1 38.6 39.9

3150 71.5 36.8 41.3 37.7 35.5 37.6

4000 68.5 38.5 41.1 39.3 40.1

B-18
Table B18. Noise Intrusion Reduction, Data Set No. 1, Test Eouse No. 9,

Front Door Open

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

Average

of

Listener

Positions

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

64.9

65.1

64.3

74.1

77.3

73.4

77.1

65.7

68.6

72.0

69.7

66.8

75.2

78.2

80.8

83.3

77.7

74.7

69.7

65.1

5.9

7.4

12.8

17.1

14.8

3.1

17.8

17.0

17.6

18.5

17.0

14.8

13.7

15.2

13.8

13.0

10.7

10.2

8.4

7.8

4.9

8.4

6.9

10.1

25.9

17.0

15.4

10.7

14.9

16.8

15.7

12.1

15.8

14.5

12.4

13.1

10.7

9.5

11.5

11.9

4.9

9.9

7.5

9.6

19.8

6.2

22.1

13.5

14.6

14.8

14.2

13.0

15.4

12.0

10.8

10.8

7.5

8.5

7.9

9.1

7.9 6.7

12.4 9.9

12.1 7.4

11.9 10.4

15.3 18.5

12.4 9.8

19.4 18.1

14.7 12.6

19.6 15.9

20.8 16.8

17.5 15.6

17.6 13.7

20.2 16.7

16.0 13.8

16.1 12.6

16.6 12.9

14.0 10.0

12.7 9.9

13.5 10.3

13.7 11.1

B-19
50 n—I—

I—I—I—

I—I—

r

_ Test House No. 1

40

00

o

I—

Q 30

LU

O

20

g 10

I I I

'

' I

' '

I 1—I—I—I—

r

Range of NIR values for individual listener positions

J L J L J L J L I I I I J L 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz|

Figure Bl. Noise Intrusion Reduction (average and range over listener positions) for Test House No. 1, Data Set No. 1.

B-20
COa

o

I—

C_3

o

50

40

30

20 -

1 I

I

I I

I

I r

. Test House No. 2

g lOh

"1—

I—I—I—I—I—I—I—I—I—

I—I—

J \ I \ L

Range of NIR values for individual listener positions

I I I I

I I I 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY [Hzj

Figure B2 . Noise Intrusion Reduction (average and range over listener positions) for Test House No. 2, Data Set No. 1.

B-21
CO

50

40

. Test House No. 3

o

CD

E 30

o

20 -

oo^

10

1—I—

I—I—I—

I—I—I—I—I—I—

I—I—I—

I—I—I—

I—I—

r

/Vh

Range of NIR values for individual listener positions

J L

NOTE: NIR values between 200 and

1000 Hz not given due to insufficient interior SPL for these bands.

J I I I I I I I I I \ \ I I 1 I I I I L 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz|

Figure B3. Noise Intrusion Reduction (average and range over listener positions) for Test House No. 3, Data Set No. 1,

B-22
00a

O

I—

a

LU

CC

o

50

40

30

20

g 10

-|—I—

I—I—I—I—I—

Test House No. 4

I I I r I'M 1—

L_L

'Range of NIR values for individual listener positions

I I I I '

I

'

I I 1 L I I I 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY fHzl

Figure B4. Noise Intrusion Reduction (average and range over listener positions) for Test House Mo. 4, Data Set No. 1.

B-23
CO

50

40

C_3

g 30

LU

o

00

20 -

i 10

T 1

1 1 1 1

1 1

1 1 11 1 11 1 11 1 11 I'M 1—^T Test House No. 5

•Range of NIR values for individual listener positions

J I I \ I I L I 1 I I _1_J L J I I I L

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz)

Figure B5. Noise Intrusion Reduction (average and range over listener positions) for Test House No. 5, Data Set No. 1.

B-24
QO

50

40

C3

g 30

00

20

% 10

~i—I—

I—I—I

\—I—I—

I—I—I—

I—I—I—

I—I—I—

I—I—

Test House No. 6

Range of NIR values for ndividual listener positions

T—

kvW~^

I \ \ I I I I I I I I I I I I I I I \ \ i \ \ L

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz|

Figure B6. Noise Intrusion Reduction (average and range over listener positions) for Test House No. 6, Data Set No. 1.

Br-25
CO

CO

50

40

30

20

1 I

I

I \ II I

I

I—I—

I—I—I—I—I—I—

I—I—I—

I—I—

r

. Test House No. 7

CO^

10

Range of NIR values for

individual listener positions

111 III I I I I J 1 I I I I I I I I L 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz]

Figure B7. Noise Intrusion Reduction (average and range over listener positions) for Test Rouse No. 7, Data Set No. 1,

B-26
CQ

50

40

1

\—

I—I—I

\—I—I—

I—I—I—

I—I—I—I—I—I—I—I—I—

I—I—

_ Test House No. 8

o

I—

g 30

UJ

O

CO

00

20 -

5 10

Range of NIR values for individual listener positions

1

I I I I I J I I I I I I 1 I I

I I I I 1 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY [Hz]

Figure B8. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 8, Data Set No. 1.

B-27
50

S 40

O

HCO

g 30

UJ

O

20

g 10

1—I—

I—I—I—

I—I—I—I—I—

r

Test House No. 9

1—I—I—I—I—I—I—I—I—

r

Range of NIR values for individual listener positions

J i I I \ I L J I I I I I I \ I I L 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hzl

Figure B9. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 9, Data Set No. 1.

B-28
Appendix C. Values of Noise Intrusion Reduction Determined

K With Maximum Occurring Outdoor and Indoor Sound Pressure Levek

Hi The NIR values presented in this Appendix were obtained from the maximum

sound pressure levels measured at each exterior and interior microphone

position regardless of when, during the test vehicle passby, the maximum level

at an individual position occurred. These values of NIR correspond to those of

Data Set No. 2 as referred to in Section 3.3. The 1/3-octave band values of

NIR from 50 to 4000 Hz obtained using this data reduction technique are presented in Tables CI through C19. In Tables C1-C18, the average of the two

3-m exterior sound pressure levels are presented along with the NIR values for

the interior reference microphone position, those for the three individual

listener microphone positions, and the average of the listener position

values, as determined using Eq. (4) of Section 4.1.1.

The NIR values used to obtain the average NIR for the nine test houses

are presented in Tables CI, C3, and C7-C13. Additional NIR values for three

different test vehicle passbys of test house No. 2 are presented in Tables C2,

C4, and C5. Also, NIR values for four additional passbys of Test House No. 9 are presented in Tables C14-C17. NIR values determined with the windows open

for Test House No. 2 are given in Table C6 and values with the front door of

Test House No. 9 open are given in Table C18. A summary of the NIR values

averaged over the three listener positions for each of the nine test houses is

presented in Table C19 , along with NIR values averaged for all nine houses,

using Eq. (7) of Section 4.2.1 (for both 1/3- and 1/1-octave bands).

Also included in this Appendix are plots of the average NIR values

determined for each of the nine test houses with windows and doors closed.

These are presented in Figures C1-C9 and correspond to the values in Tables

CI, C3, and C7-C13.

C-1
Table CI. Noise Intrusion Reduction, Data Set No. 2, Test House No.l

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

KIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

3

Average

of

Listener

Positions

50 70.3 16.3 11.8 13.3 16.2 13.4

63 71.0 15.4 18.8 13.0 14.7 14.9

80 64.5 18.1 23.2 17.5 18.8 19.2

100 67.3 23.2 24.4 21.6 24.0 23.1

125 73.1 23.7 29.4 24.6 31.3 27.5

160 66.1 23.0 22.7 17.9 20.6 20.0

200 67.6 26.4 25.6 22.0 25.0 23.9

250 74.9 23.4 30.3 26.9 32.8 29.3

315 70.7 27.1 28.7 26.3 30.1 28.1

400 62.6 29.2 27.0 26.1 27.6 26.9

500 69.6 30,6 34.4 29.6 29.6 30.7

630 67.4 30.6 33.3 29.6 31.2 31.1

800 66.2 33.1 35.1 31.0 32.6 32.6

1000 65.2 32.3 35.4 31.3 30.6 32.0

1250 65.8 32.0 35.7 30.6 32.4 32.4

1600 63.8 34.5 37.1 32.3 33.9 34.0

2000 61.6 34.1 38.1 31.5 32.8 35.1

2500 59.4 34.5 37.5 31.4 32.6 34.7

3150 55.7 35.5 36.0 32.1 31.5 33.7

4000 53.4 34.8 34.8 30.0 30.4 32.3

C-2
Table C2. Noise Intrusion Reduction, Data Set No. 2, Test House No. 2,

Passby No.l

1/3-

Octave

Band

Center

Frequency

,

Hz

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

Average

of

Listener

Positions

Frequency AVG

50 62.0

63 67.6

80 70.4

100 76.5

125 80.2

160 81.5

200 73.9

250 65.4

315 59.6

400 57.4

500 59.0

630 60.0

800 64.0

1000 68.9

1250 71.2

1600 69.9

2000 70.9

2500 69.9

3150 65.3

4000 64.0

NR

11.1

19.0

23.7

18.6

19.4

19.4

17.3

16.3

21.0

25.8

26.9

28.6

33.9

34.4

34.4

35.1

34.9

32.8

36.9

NR

14.1

23.8

24.0

18.7

17.8

22.5

24.0

21.5

25.6

27.2

27.0

33.1

33.7

35.4

34.1

33.7

32.1

32.8

37.1

NR

12.3

14.8

14.9

26.8

29.8

27.9

24.8

23.8

27.4

28.6

29.5

33.3

36.0

37.7

37.2

38.2

38.8

34.6

38.7

NR

12.9

16.9

21.2

22.8

22.0

28.6

22.3

20.5

24.7

26.3

27.9

31.9

34.4

37.9

37.2

37.4

37.8

35.7

38.4

NR

13.0

17.2

18.3

21.6

21.0

25.4

23.6

21.7

25.8

27.3

28.0

32.7

34.6

36.8

35.9

36.0

35.2

34.2

38.0

C-3
Table C3. Noise Intrusion Reduction, Data Set No. 2, Test House No,

2

Passby No.

2

1/3- NIR, dB

Octave

Band Average Interior Listener Listener Listener Average

Center Exterior Reference Position Position Position of

Listener

Positions Frequency

,

Hz

Level, dB Position No.l No. 2 No.

3

Frequency AVG NR NR NR NR NR

50 68.4 13.1 16.5 16.7 14.7 15.9

63 64.4 11.8 15.2 15.5 13.0 14.4

80 74.6 22.8 21.7 17.1 20.0 19.2

100 73.1 25.1 28.5 20.8 24.8 23.6

125 81.7 29.5 26.1 33.6 28.2 28.3

160 71.2 20.2 21.0 26.0 25.0 23.4

200 77.3 19.7 25.4 25.9 30.2 26.7

250 70.8 22.7 26.4 25.6 25.6 25.9

315 62.7 21.0 23.4 26.9 23.8 24.4

400 59.6 21.0 23.6 27.0 25.4 25.1

500 62.1 25.7 26.3 29.1 25.3 26.6

630 61.4 26.9 28.9 29.1 29.1 29.0

800 65.5 28.3 32.7 32.4 31.5 32.2

1000 69.6 34.2 34.6 35.8 35.4 35.2

1250 71.2 34.3 35.3 37.5 37.6 36.7

1600 70.5 33.8 35.1 37.5 37.2 36.5

2000 70.7 34.1 33.4 38.1 37.1 35.7

2500 70.3 35.1 33.9 37.7 37.8 36.1

3150 65.0 33.0 32.8 33.7 34.4 33.6

4000 63.8 36.1 36.3 38.8 37.9 37.5

C-4
Table C4. Noise Intrusion Reduction, Data Set No. 2, Test House No. 2, Passby No.

1/3-

Octave

Band Average

NIR, dB

Interior Listener Listener Listener Average

of

Listener

Positions

Center Exterior Reference Positioa Position Position

Frequency,

Hz

Level, dB Position No.l No. 2 No.

50 68.6 13.8 11.3 16.6 15.0 13.7

63 65.8 12.5 11.3 15.1 14.2 13.2

80 72.4 21.0 22.0 14.0 18.8 17.0

100 74.5 30.5 28.6 23.5 25.2 25.3

125 76.9 20.2 19.9 30.6 26.2 23.5

160 74.4 19.8 20.4 28.9 24.6 23.3

200 76.4 21.2 24.6 25.1 29.0 25.8

250 72.3 19.9 24.5 25.8 23.3 24.4

315 66.4 19.4 21.6 27.2 23.1 23.4

400 64.5 22.7 24.8 26.4 26.6 25.9

500 63.8 26.2 27.3 28.2 26.9 27.4

630 63.1 26.9 28.9 29.4 28.5 28.9

800 66.6 28.1 33.1 33.7 32.5 33.1

1000 70.1 33.7 34.3 35.5 35.2 35.0

1250 70.9 34.4 34.9 37.2 37.5 36.4

1600 69.6 34.0 33.8 37.4 36.8 35.7

2000 70.4 35.3 34.0 38.9 .38.2 36.5

2500 69.2 35.4 34.1 37.1 37.7 36.0

3150 64.2 31.1 31.0 31.2 31.1 31.7

4000 63.0 35.5 35.8 38.1 37.2 36.9

C-5
Table C5. Noise Intrusion Reduction, Data Set No. 2, Test House No.

2

Passby No.

4

1/3- NIR, dB 1 Octave

Band

Center

Frequency*

Hz

Average

Exterior

Level, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No. 3

Average

of

Listener

Positions

50 64.7 11.5 11.8 13.0 12.4 12.4

63 63.7 11.6 11.9 16.6 12.6 13.3

80 69.2 18.6 20.3 12.2 17.1 15.3

.00 73.7 31.1 28.1 19.3 26.9 22.9

125 73.9 19.9 19.6 27.8 23.7 22.5

160 75.6 16.7 16.6 27.3 21.1 19.8

200 74.9 19.6 25.0 24.5 28.4 25.7

250 73.1 20.6 25.7 25.7 24.2 25.1

315 68.3 23.2 23.7 26.6 23.8 24.5

400 63.4 23.4 26.6 28.0 26.9 27.1

500 63.6 26.0 25.8 28.7 25.4 26.4

630 63.7 27.3 28.9 30.4 28.4 29.2

800 65.9 29.1 32.0 32.8 31.7 32.1

1000 69.5 33.3 34.1 35.0 35.0 34.7

1250 70.9 34.7 35.1 37.9 37.1 36.5

1600 69.3 33.5 33.8 37.0 36.6 35.6

2000 69.4 34.1 32.6 37.6 36.6 35.0

2500 69.3 35.0 32.9 38.3 37.7 35.6

3150 64.3 32.4 32.4 34.1 34.3 33.5

4000 63.1 35.7

-

36.1 38.4 37.9 37.4

C-6
Table C6. Noise Intrusion Reduction, Data Set No. 2, Test House No.

Windows Open

1/3-

Octave

Band

Center

Erequency,

Hz

Average

Exterior

Level , dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

Average

of

Listener

Positions

50 66.3 9.9 13.5 16.5 12.7 14.0

63 64.2 8.7 12.8 14.2 9.0 11.4

80 69.6 13.7 18.8 11.2 13.1 13.4

100 67.8 17.7 18.6 13.5 15.2 15.3

125 72.2 13.6 12.0 19.4 16.2 14.8

160 73.3 10.5 10.7 19.8 13.6 13.3

200 74.8 14.6 17.2 18.7 20.6 18.6

250 70.1 10.9 14.4 15.3 10.6. 12.9

315 65.0 11.3 13.6 14.3 15.3 14.3

400 63.3 10.8 13.0 12.8 13.8 13.2

500 63.8 7.2 13.9 14.5 12.9 13.7

630 62.5 6.5 11.9 13.7 14.0 13.1

800 65.9 6.8 13.0 13.9 13.2 13.3

1000 71.1 7.3 14.5 16.4 12.4 14.1

1250 74.7 5.7 14.8 15.7 12.2 14.0

1600 74.0 5.3 14.0 15.7 10.8 13.0

2000 67.5 5.8 12.5 14.7 7.6 10.6

2500 67.4 6.9 12.5 15.3 7.2 10.4

3150 66.5 5.1 16.9 19.1 9.8 13.3

4000 63.4 3.9 16.2 17.7 11.8 14.5

C-7
Table C7. Noise Intrusion Reduction, Data Set No. 2, Test House No.

3

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

KIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

3

Average

of

Listener

Positions

63 56.0 8.8 16.7 10.8 11.9 12.5

63 64.9 22.6 23.8 21.6 22.7 22.6

80 66.4 22.4 27.4 25.1 25.7 26.0

100 72.4 26.8 25.8 26.8 26.2 26.2

125 74.6 30.2 21.9 29.0 26.7 24.8

160 77.2 21.6 23.3 25.3 24.7 24.4

200 72.6 20.2 28.4 28.7 24.9 27.0

250 72.7 27.1 37.2 33.2 31.7 33.5

315 60.2 21.8 31.6 30.7 30.0 30.7

400 55.4 26.2 28.5 30.8 29.0 29.3

500 55.2 27.8 30.8 32.2 29.9 30.9

630 52.9 29.8 30.9 31.7 28.9 30.3

800 52.6 29.6 31.4 32.2 31.2 31.6

1000 58.4 33.2 33.3 35.0 34.2 34.1

1250 63.0 36.2 36.8 34.6 36.6 35.9

1600 65.6 37.8 38.8 39.2 39.1 39.0

2000 65.9 32.6 33.0 34.3 34.9 34.0

2500 66.9 35.7 35.8 36.5 37.9 36.6

315,0 65.3 37.7 37.6 38.2 38.6 38.1

_

4000 62.7 38.4 38.5 40.0 39.0 39.1

0-8
Table C8. Noise Intrusion Reduction, Data Set No. 2, Test House No. 4

1/3-

Octave

Band

Center

Frequency*

Hz

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

Mo -3

Average

of

Listener

Positions

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

68.4

64.4

76.9

68.1

81.2

70.9

76.8

72.7

66.7

67.1

64.2

63.5

67.5

71.0

73.7

72.0

68.7

69.0

67.5

63.9

14.0 13.8

15.2 17.8

21.1 19.8

20.4 22.0

22.1 25.6

19.8 29.5

20.7 28.1

21.5 31.4

19.3 26.4

24.2 30.1

25.8 32.3

29.2 35.0

31.4 36.8

32.1 39.7

33.6 40.8

34.9 42.4

33.6 38.4

33.8 39.6

35.8 42.0

34.1 39.9

8.7

11.3

17.9

18.-4

22.4

24.9

26.8

31.7

31.0

33.1

28.2

33.0

34.9

37.2

38.2

38.9

36.0

38.4

38.9

37.9

14.6

23.1

25.1

17.5

18.8

20.-9

22.3

26.7

28.0

30.7

30.8

33.2

35.2

38.0

39.4

40.4

36.0

37.5

38.7

37.1

11.5

15.0

20.0

18.9

21.4

23.8

25.0

29.3

28.1

31.1

30.1

33.6

35.6

38.2

39.3

40.3

36.7

38.4

39.6

38.1

C-9
Table C9. Noise Intrusion Reduction, Data Set No. 2,

Test House No. 5

1/3- NIR, dB 1 Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

3

Average

of

Listener

Positions

50 70.9

7.15

10.3 13.4 11.0 9.3 10.9

63 13.5 9.5 13.7 17.2 12.4

80 67.0 16.8 21.1 14.2 13.3 15.1

100 76.7 18.9 25.0 9.3 23.5 13.8

125 63.9 15.4 17.9 15.6 15.0 16.0

160 68.5 14.2 17.3 22.0 23.6 20.1

200 73.5 22.3 22.0 26.1 22.0 23.0

250 65.9 29.9 26.9 28.8 31.8 28.7

315 64.6 28.2 29.9 28.8 31.3 29.9

400 62.9 26.9 29.7 31.7 28.7 29.9

500 60.6 28.9 30.3 31.2 30.6 30.7

630 61.8 32.0 33.9 32.2 32.3 32.7

800 64.4 36.4 36.2 36.1 37.3 36.5

1000 69.9 36.8 38.4 38.6 38.7 38.5

1250 72.6 35.2 37.4 36.8 37.0 37.1

1600 71.1 37.0 39.0 37.1 36.5 37.4

2000 69.5 35.0 36.9 35.9 35.7 36.1

2500 70.1 37.7 39.4 38.2 37.1 38.1

3150 66.7 38.3 38.8 38.9 38.3 38.7

4000 63.8 39.0 39.8 39.6 40.2 39.9

C-10
Table CIO. Noise Intrusion Reduction, Data Set No. 2 Test House No. 6

' '

1/3-

Octave

Band

Center

Frequency*

Hz

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

Average

Exterior

NIR, d3

Interior

Reference

Level, dB Position

67.6

67.1

73.8

71.2

75.9

74.3

70.8

66.4

65.7

61.7

58.5

57.7

61.2

64.4

68.2

70.5

70.3

70.0

67.4

62.8

T

Listener

Position

No.l

Listener

Position

No. 2

12.2

19.1

15.3

15.7

20.9

23.1

20.3

21.3

21.7

25.8

23.5

26.9

29.7

30.5

30.9

34.1

32.9

35.1

30.5

32.7

13.2

17.6

16.8

17.7

21.9

19.8

22.4

34.2

24.7

25.0

20.5

24.6

29.7

31.6

34.2

35.4

34.0

38.0

37.3

34.2

Listener

Position

No.

19.4 11.6

22.4 16.2

16.0 19.6

16.8 19.4

17.0 24.1

20.8 25.2

23.3 27.8

25.2 24.8

25.0 24.7

26.9 26.1

24.1 25.2

27.2 25.7

30.6 30.6

30.4 33.1

30.0 33.9

33.2 36.4

27.3 35.6

36.2 38.3

37.4 37.6

34.1 36.6

Average

of

Listener

Positions

13 .7

18 .0

17 .2

17 .8

20 .0

21 .4

23 .9

24 .7

24 .8

25 9

22 8

25. 7

30. 6

31. 6

32. 2

34. 8

30. 7

37. 4

37. 4

34. 8

C-11
Table Cll. Noise Intrusion Reduction, Data Set No, 2 Test House No. 7

'

1/3-

Octave

Band

Center

Frequencyj

Hz

KIR, d3

Average

Exterior

Level, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

3

Average

of

Listener

Positions

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

69.6

72.2

70.5

75.8

66.2

68.3

75.6

65.9

64.6

65.2

62.0

63.0

63.5

67.7

69.8

69.6

67.6

65.6

61.2

57.1

13.8

13.5

15.0

17.3

25.2

19.3

26.3

20.5

25.1

27.0

30.1

31.5

32.4

34.4

34.0

33.3

34.5

40.9

41.5

39.3

13.4

13.0

17.9

17.8

31.3

23.4

32.9

27.5

28.0

32.9

33.0

32.5

34.6

36.1

35.5

34.7

36.7

42.8

42.2

39.2

14.5

16.5

16.6

15.3

19.8

26.4

34.9

23.5

30.1

29.8

32.0

34.1

33.6

34.3

35.4

33.0

35.7

41.3

41.3

39.1

16.0

14.9

21.2

22.9

19.9

24.0

25.6

26.3

29.0

29.8

32.6

34.7

34.1

34.9

35.2

33.4

34.9

41.3

40.3

38.2

14.5

14.6

18.2

17.7

21.5

24.4

29.2

25.4

28.9

30.6

32.5

33.7

34.1

35.0

35.4

33.6

35.7

41.7

41.2

38.8

C-12
Table C12. Noise Intrusion Reduction, Data Set No. 2, Test House No. 8

1/3-

Octave

Band

Center

Frequency^

Jis

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

Average

of

Listener

Positions

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

66.3

70.4

67.6

66.0

71.9

73.7

66.9

70.9

72.2

64.7

62.4

62.9

64.0

68.3

70.6

71.2

69.6

67.0

63.3

58.7

17.3 15.1

14.4 21.7

16.1 9.7

13.2 11.9

18.5 14.4

22.7 20.3

22.1 22.2

23.1 27.1

26.2 24.2

26.9 23.9

26.7 28.7

29.6 31.4

30.0 32.3

29.6 31.9

28.3 31.3

28.3 30.3

29.9 32.9

34.6 35.2

36.8 37.4

31.9 32.8

15.6

15.9

11.9

15.5

14.0

18.5

20.8

25.8

25.2

25.4

25.4

30.9

29.6

31.2

32.2

30.9

33.4

33.2

35.0

31.9

17.6

16.2

16.1

16.5

19.0

19.4

24.8

29.1

28.1

28.0

31.1

31.9

32.8

33.4

32.4

32.1

33.9

36.1

37.3

31.3

16.0

17.3

11.8

14.2

15.3

19.3

22.3

27.1

25.5

25.5

27.8

31.4

31.3

32.1

31.9

31.0

33.4

34.7

36.4

32.0

C-13
Table C13 . Noise Intrusion Reduction, Data Set No. 2,

Test House No. 9, Passby No. 1

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

"^'osition

No.l

Listener

Position

No. 2

Listener

Position

No.

3

Average

of

Listener

Positions

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

.1

6l'

'

73 . z

76 .1

74 .5

76 .7

75 .6

71 .7

71 .2

72 2

70 4

68 6

75. 3

80. 5

83. 1

84. 3

81. 8

78. 4

75. 6

70. 5

12.6

13.7

17.7

19.7

23.5

19.4

20.3

19.2

20.5

23.4

28.1

30.8

32.3

33.8

36.3

37.1

37.4

36.1

39.1

37.2

14.1

14.3

18.2

17.0

20.

11.

18 >^

22.5

26.7

27.8

28.8

32.1

34.3

35.8

39.0

40.3

39.7

38.0

40.6

40.3

12.1

13.6

18.6

15.1

26.8

24.5

24.4

27.9

29.4

28.3

29.6

32.3

35.0

35.8

39.1

41.4

40.5

36.9

41.3

41.7

18.1

17.9

23.8

18.7

18.0

23.4

25.6

25.7

22.8

24.6

24.8

31.6

32.8

33.5

36.3

40.3

40.3

39.8

40.6

4\7

14.1

14.9

19.6

16.7

20.5

22.2

21.9

24.8

25.5

26.6

27.2

32.0

33.9

34.8

37.9

40.6

40.2

38.1

40.8

40.9

C-14
Table C14. Noise Intrusion Reduction, Data Set No. 2, Test House No. 9, Passby No. 2

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

Average

of

Listener

Positions

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

67.9

69.9

73.7

71.1

81.1

72.1

70.2

67.5

69.7

71.1

70.6

68.5

76.2

80.7

83.2

84.0

81.1

78.1

75.4

70.9

15.5

16.8

19.2

21.8

26.1

20.7

20.7

18.5

21.3

23.7

28.3

31.6

32.8

32.2

36.1

37.4

38.1

36.7

38.7

38.2

17.2

16.1

13.6

22.7

27.4

20.7

19.0

19.7

25.6

27.7

28.2

33.4

34.9

34.6

39.1

40.0

39.8

37.4

40.4

40.7

10.6

16.0

18.9

21.0

30.8

24.4

23.3

27.4

29.9

28.1

29.8

32.3

35.4

34.0

39.1

41.7

39.8

36.8

40.4

42.2

19.5

23.2

19.3

17.6

21.6

25.5

23.1

24.0

23.9

24.0

24.2

32.4

34.2

33.6

36.3

39.6

40.1

39.3

40.2

40.2

14.1

17.4

16.4

19.9

25.0

23.0

21.3

22.6

25 8

26.2

26.7

32.7

34.8

34.0

38.0

40.3

39.9

37.7

40.3

41.0

C-15
Table C15. Noise Intrusion Reduction, uata Set No. 2, Test House

No. 9, Passby No.

3

1/3-

Octave

Band Average

NIR, dB

Interior Listener Listener Listener Average

Center

Frequency

Hz

Exterior

Level , dB

Reference

Position

Position

No.l

Position

No. 2

Position

No.

3

of

Listener

Positions

50 68.5 14.4 15.9 8.6 15.9 12.0

63 71.3 17.3 15.5 15.2 22.2 16.7

80 75.9 20.3 14.2 20.6 20.0 17.2

100 70.3 20.5 15.6 17.4 19.9 17.3

125 81.1 24.1 26.1 27.3 22.6 24.9

160 76.3 18.9 22.5 24.2 23.6 23.4

200 71.9 22.2 17.8 22.5 23.5 20.5

250 69.8 19.5 20.7 26.5 25.0 23.3

315 70.3 21.6 25.8 29.6 22.8 25.2

400 71.7 25.0 27.7 29.4 24.7 26.8

500 70.6 28.3 29.1 29.8 25.2 27.5

630 68.2 30.4 31.6 30.4 31.5 31.1

800 76.0 32.6 34.6 35.5 33.3 34.4

1000 80.5 33.2 35.3 34.4 33.0 34.1

1250 83.2 36.5 38.7 37.6 36.2 37.4

1600 83.6 37.6 40.0 41.8 39.9 40.5

2000 81.6 37.4 39.4 39.7 40.1 39.7

2500 78.3 36.0 37.5 36.5 39.1 37.6

3150 75.7 38.8 40.8 41.1 40.3 40.7

4000 70.8 36.7 40.4 41.6 39.8 40.5

1

C-16
Table C16. Noise Intrusion Reduction, Data Set No. 2, Test House No. 9, Passby No.

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level. , dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No. 3

Average

of

Listener

Positions

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

67.0

66.0

76.4

83.4

87.3

73.3

73.1

70.3

72.2

71.7

71.4

68.0

74.0

81.1

83.7

84.1

82.1

79.0

76.3

71.7

15.5

13.7

20.5

22.0

26.8

19.5

20.8

19.8

21.8

24.7

27.8

31.1

32.4

32.9

36.9

38.0

38.0

36.6

39.0

38.6

16.2

11.3

14.7

22.9

29.6

22.3

17.8

20.4

27.4

27.6

27.5

32.4

34.5

35.4

38.9

40.2

39.9

37.5

40.8

40.9

9.8

12.8

19.5

24.8

30.7

23.4

23.1

27.7

31.0

29.7

30.0

31.7

35.1

35.2

38.5

41.3

40.3

36.0

41.0

42.2

16.9

18.4

20.2

19.2

20.3

25.9

24.6

25.2

24.0

24.7

24.9

31.9

31.8

33.0

36.4

39.1

40.7

39.3

41.0

41.0

13.0

13.3

17.4

21.7

24.2

23.6

20.8

23.4

26.6

26.8

27.0

32.0

33.6

34.4

37.8

40.1

40.3

37.4

40.9

41.3

C-17
Table C17 . Noise Intrusion Reduction, Data Set No. 2, Test House No. 9,

Passby no.

5

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

. Position

No.l

Listener

Position

No. 2

Listener

Position

No.

3

Average

of

Listener

Positions

50 67.8 13.4 15.3 9.7 16.8 12.8

63 69.2 17.7 16.5 15.3 22.2 17.1

80 74.8 18.6 15.2 19.2 21.4 17.8

100 70.8 19.7 16.7 18.0 19.1 17.8

125 77.3 22.4 22.2 27.0 20.3 22.4

160 77.6 20.3 22.2 25.5 25.2 24.0

200 71.5 21.5 17.3 22.4 22.8 20.1

250 70.5 20.6 20.9 25.7 23.7 23.0

315 70.1 21.7 26.4 29.9 23.6 25.9

400 71.4 22.7 27.9 28.1 24.2 26.3

500 70.9 27.9 28.2 30.3 23.9 26.6

630 68.1 31.0 32.1 30.6 32.1 31.5

800 74.0 31.9 33.6 35.3 31.4 33.1

1000 80.1 34.1 34.9 34.7 34.1 34.6

1250 83.2 36.5 38.6 38.5 36.6 37.8

1600 83.5 37.7 40.0 41.3 39.1 40.0

2000 81.3 37.3 39.8 39.7 40.3 39.9

2500 78.1 36.7 36.8 36.3 39.3 37.3

3150 75.1 38.6 40.3 40.3 40.3 40.3

4000 70.5 37.2 40.0 41.7 39.8 40.4

C-18
Table C18. Noise Intrusion Reduction, Data Set No. 2, Test House No.

Door Open

1/3-

Octave

Band

Center

Frequency,

H7.

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Lxstener

Position

No.

Average

of

Listener

Positions

50 71.3 8.2 7.6 5.5 10.7 7.4

63 68.6 8.2 9.0 7.6 12.1 9.2

80 71.2 9.6 13.7 11.9 17.7 13.8

100 76.6 13.3 15.1 9.7 14.3 12.3

125 77.9 10.5 19.2 10.4 13.4 13.0

160 78.3 8.0 19.0 8.3 18.6 12.4

200 76.4 13.7 13.6 18.4 17.8 16.0

250 71.1 17.2 15.8 17.9 19.3 17.4

315 70.8 19.0 16.4 16.3 19.8 17.2

400 71.5 18.1 17.6 14.8 17.5 16.4

500 70.7 19.2 16.1 16.3 18.3 16.8

630 68.1 15.0 15.5 13.3 17.4 15.1

800 74.8 16.2 16.7 12.9 18.7 15.4

1000 80.3 17.2 15.9 13.7 18.0 15.5

1250 82.9 16.2 16.2 13.0 19.1 15.4

1600 82.4 13.4 14.7 11.8 17.4 14.0

200 81.0 15.1 15.0 11.9 17.7 14.2

2500 78.0 14.8 15.0 12.3 16.5 14.2

3150 75.2 15.9 16.3 15.0 18.1 16.3

4000 70.7 15.6 17.1 15.4 18.3 16.8

C-19
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I r

"1—I—I—

I

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Range of NIR values for individual listener positions

J I I I I \ \ \ I L I I I I I I I I I I 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz]

Figure CI. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 1, Data Set No. 2.

C-21
00

50

40

T I

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I—I—II—I—

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Test House No. 2

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31.5

'Range of NIR values for individual listener positions

I I I

I I I l_J I I I I I \ I I I \ I L 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz|

Figure C2. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 2, Data Set No. 2.

C-22
cao

50

40

T—I—

I—I—I—

I—I

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I—I—I—I—I—I—I—

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'Range of NIR values for individual listener positions

I \ I I I I I I I I I'll I I

I I I I I I I I 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure C3. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 3, Data Set No. 2.

C-23
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50

40

o

o

E 30

UJ

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o

00

20

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Test House No. 4

'

I I L__l I I L

Range of NIR values for individual listener positions

J I I I I 1 I I I I I L 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz)

Figure C4. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 4, Data Set No. 2.

C-24
00

50

40

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I—I

\—

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_ Test House No. 5

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'Range of NIR values for individual listener positions

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31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY [Hz]

Figure C5. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 5, Data Set No. 2.

C-25
00

50

40

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-Range of NIR values for individual listener positions

I I I ' 'I I I

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31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure C6. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 6, Data Set No. 2.

C-26
00

o

00

oo

50

40

30

20

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^

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Range of NIR values for individual listener positions

L-L J I I \ L J I I I L I I 1

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31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure C7. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 7, Data Set No. 2.

C-27
00-Q

o

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50

40

30

20 -

^

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I—I—I—

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Test House No. 8

T

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—Range of NIR values for individual listener positions

I—I I I I I I I I I I I I I I I I' I I I I '

I 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY |Hz)

Figure C8. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 8, Data Set No. 2.

C-28
CO

50

40

C3

g 30

LU

O

CO

20

S 10

"I\—

I—I—I—

I—I—I—I—I—

Test House No. 9

1—I—I—

1—I—

I—I—

Range of NIR values for individual listener positions

I I I I I I _1_J \ L I I I I 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY [Hz]

Figure C9. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 9, Data Set No. 2.

C-29

Appendix D. Values of Noise Intrusion Reduction Determined

from Outdoor and Indoor 1/3-Octave Band Sound Exposure Levels

The NIR values presented in this Appendix were obtained from 1/3-octave

band sound exposure levels (SEL) as determined at each exterior and interior

microphone position and correspond to Data Set No. 3 of Section 3.3. The

values of NIR from 50 to 4000 Hz obtained using this data reduction technique

are presented in Tables Dl and D2 for Test Houses No. 6 and No. 8, respectively.

In each table, the average SEL values for the two 3-m microphone positions

are presented along with the NIR values for the interior reference microphone

position, the values for the three individual listener microphone positions,

and the average over the listener positions, as determined using Eq. (4) of

Section 4.1.1. The average NIR values determined for the listener positions

at the two test houses are plotted in Figures Dl and D2.

D-1
Table Dl. Noise Intrusion Reduction, Data Set No. 3, Test House No.

6

1/3-

Octave

Band

Center

Frequency,

Hz

Average

Exterior

Level, dB

NIR. dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No.

3

Average

of

Listener

Positions

50 60.0 10.6 11.2 17.8 9.9 11.9

63 61.4 17.7 15.7 20.8 15.7 16.8

80 67.9 15.5 18.0 13.8 19.3 16.4

100 63.7 15.4 18.2 14.9 18.7 16.9

125 70.5 21.1 22.4 18.6 23.7 21.0

160 68.1 22.2 19.4 20.8 24.9 21.1

200 65.4 20.5 23.0 21.9 26.2 23.3

250 60.2 20.4 22.2 24.2 23.6 23.3

315 60.0 19.9 23.6 24.9 23.3 23.9

400 56.7 23.8 24.4 26.3 25.8 25.4

500 55.0 24.6 22.7 25.7 27.4 24.8

630 53.6 27.7 25.9 27.7 29.4 27.4

800 54.9 28.0 28.3 29.9 30.4 29.4

1000 58.1 29.7 30.4 30.4 32.2 30.9

1250 60.9 30.4 32.8 30.5 33.1 32.0

1600 62.2 32.5 34.4 33.3 34.7 34.1

2000 61.6 31.7 33.3 28.1 34.1 31.0

2500 61.0 32.9 35.6 34.2 35.3 35.0

3150 58.0 30.1

-

34.7 34.9 34.9 34.8

D-2
Table D2 . Noise Intrusion Reduction, Data Set No. 3, Test House No.

1/3-

Octave

Band

Center

Frequency*

Hz

Average

Exterior

Level, dB

NIR, dB

Interior

Reference

Position

Listener

Position

No.l

Listener

Position

No. 2

Listener

Position

No -3

Average

of

Listener

Positions

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

61.2

65.5

64.0

63.3

69.4

69.6

63.4

66.6

67.9

59.8

58.3

58.6

60.1

63.7

65.2

65.4

63.4

61.1

58.1

16.4

10.0

17.1

18.0

19.3

21.3

21.6

22.4

25.8

26.4

27.1

29.6

30.1

28.9

28.1

28.0

28.7

33.0

34.7

16.3

21.2

8.8

12.3

16.3

20.1

22.0

25.4

25.3

25.6

28.3

30.9

32.3

31.8

31.5

30.1

31.5

33.9

35.5

14.2

16.1

12.2

15.9

17.2

19.9

22.3

25.4

25.9

27.0

26.9

30.8

31.4

31.1

31.7

30.8

32.5

32.6

34.0

16.8

16.7

16.3

18.9

20.0

21.6

26.0

27.9

28.6

28.2

30.2

32.1

33.0

32.8

32.0

32.2

33.2

34.7

35.1

15.6

17.5

11.4

14.9

17.6

20.5

23.1

26.1

26.4

26.8

28.3

31.2

32.2

31.8

31.7

30.9

32.3

33.6

34.8

D-3
CO

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50

40

30

20 -

. Test House No. 6

^

10

1—

r

I'M I I

I—

r

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I—I—I—I—I—I

\—I—r-|

n-r

'Range of NIR values for

individual listener positions

I

'

I ' 'I

' ' I' ' I' I I' ' I I I

I ' ' 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure Dl. Noise Intrusion Reduction (average and range over listener

positions) for Test House No. 6, Data Set No. 3.

D-A
50

40

00

o

E 30

CO

CO

20

S 10

T—

I

' ' I' ' I' ' I

' ' T—I—I—I—I—I—I—

I'M

Test House No. 8

J I I I L

-Range of NIR values for individual listener positions

J \ \ I I I I 1 I I I I I I L

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREOUENCY |Hz|

Figure D2. Noise Intrusion Reduction (average and range over listener

positions) for Test House NO, 8, Data Set No. 3.

D-5

Appendix E. Electronic Filter Simulating Average Noise Intrusion Reduction

For psychoacoustic tests to be carried out as part of this overall study

of highway noise criteria, it is desired to have an electronic filter that

will modify the signal from recordings of outdoor traffic noise so as to yield

a signal that corresponds closely to the signal that would be expected inside

a typical house. For this purpose it was decided to design a filter that

would have a frequency response simulating the average Noise Intrusion

Reduction for the nine houses included in the present investigation over the

frequency range from 50 to 4,000 Hz and that would have a nominally flat

frequency response above and below these frequencies. In order to attain the

desired perfoinnance, an active filter circuit as shown in Fig. El was

selected. The transfer function of this circuit is:

u/ N A l+jaa3T

O l+JOJT Ki^'-LJ

where A

R + R,

c f o R.

T = R C^

c f

^f

R^ + R

f c

= v^

= 2TTf = circular frequency

and R. » R » R_» and C are circuit elements as shown in Fig. El. The

amplicude^deniity spectrum of this filter is

3(03) = |H(u.)|2 = A

' ]

"- %'"^' . (-..2) O 1 + lj}^T^

E-1
Re

Cf

Rf

VWVAn

Figure El. Circuit diagram for active filter used to

simulate average Noise Intrusion Reduction.

E-2
Values of a, t, and A were selected so as to minimize the meansquare deviation between -iO Jlog [S(ca)] and the octave-band Noise Intrusion

Reduction values averaged over the nine houses (i.e., the values in column

11 of Table C19 of Appendix C) . The values so obtained are:

a = 0.0526

T = 0.00302

A 0.279

The smooth curve in Fig. E2 shows the values of -10 Sx3g [S(ol))] computed from

Eq. (E.2) using these values of a, T, and A . The triangular symbols

represent the average octave-band Noise Intrusion Reduction values (column 11

of Table C19) that were used to generate the values of the parameters for the

electronic filter. The deviations of these octave band Noise Intrusion

Reduction values from the smooth curve are less than +0.3 dB except at 250

and 500 Hz where the deviations are +1.4 and -1.4 dB , respectively. The

root-mean-square deviation of the seven octave-band values from the smooth curve is 0.8 dB.

The circular symbols in Fig. E2 represent the 1/3-octave band data for

the average of the nine houses (column 10 in Table C19) . The deviations from

the smooth curve are less than +1.0 dB except at 200, 250, 500, and 2000 Hz,

where the deviations are +1.5, +2.5, -1.9, and -1.1 dB , respectively. The

root-mean-square deviation of the twenty-one 1/3-octave band values from the

smooth curve is 0.9 dB

In addition to the filter described above that was fitted to the data

obtained as part of the present investigation, Eq. (E.2) was fitted to the

average outdoor-to-indoor octave-band noise isolation data shown as the last row of Table El in order to obtain the filter parameters for a "warm climate"

filter. The following filter parameters were selected:

a = 0.3043

T = 0.000749

A = 0.1445

The solid smooth curve in Fig. E3 shows the values of -10 2,og [S(ca)] computed

from Eq. (E.2) using these values of a, t, and A . The triangular symbols

represent the averaged experimental values listed at the bottom of Table El,

while the upper and lower limits indicate the range of the values listed in

Table El. The dashed curve corresponds to the filter response curve for

Washington, DC, area houses as shown in Fig. E2

Values of the two filter response curves are listed in Table E2,

for 1/3-octave band frequencies from 10 to 20,000 Hz.

E-3
50

40 -

00a

o

O

E 30

q:

o

20 -

g 10

I 1

1

' 1 1I 1 I1

1 . 1 1 1 .

I

1 . 1 1 I -

:

Filter response^ A * . X..^^"^^ >^

- • 9^i<

- ^

A Octave band average

NIR values

r^

("•"T^ • 1/3-octave band average

NIR values

1 1

1 , 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY [Hz)

Figure E2. Average Noise Intrusion Reduction values, for houses in

the Washington, D.C., area, compared to computed response

of an electronic filter having the circuit of Fig. El and

circuit parameter values of a= 0.0526, t= 0.00302, and

A = 0.279.

E-4
Table El. Outdoor-to-indoor noise isolation, in decibels, for houses

in "warm climates." The average values shown in the last row were averaged using Eq. (7), with the data for each city

being weighted in proportion to the number of rooms for which

measurements were made.

City

No. of No. of

Houses Rooms

Frequency

,

Hz

63 125 250 500 1000 2000 4000

a Miami 4 8 18.0 17.0 18.0 22.5 25.0 27.0 29.0

Los Angeles, CA 2 4 19.0 16.0 20.0 21.5 25.0 25.0 26.5

Wallops Island, VA

Brick Construction 1 4 17.1 23.0 21.0 20.0 27.8 30.3 30.5

Wood Construction 1 4 16.3 21.1 21.3 20.3 21.3 24.0 25.0

PIaya Del Rey, CA^ 1 3 16.9 14.5 21.0 22.5 23.5 24.8 28.8

Westchester, CA 1 5 16.7 17.3 23.8 25.4 28.2 29.4 32.4

Los Angeles, CA 11 11 16.0 20.0 21.0 24.0 25.0 26.0 28.0

AVERAGE 16.7 18.4 20.3 22.9 24.8 26.1 28.1

House Noise-Reducti(

SAE Aerospace Infom

Dn Measurements for Use in Studies o aation Report 1081 (1971)

f Aircraft Flyover Noise »

Noise Environment oJ Department of Housiic Urban and Subur

ig and Urban Deve

ban Areas (Federal

ilopment, Washington

Housing Administration,

, DC, 1967).

E-5
a

oe

LU

CO

50

40-

30

20-

Washington, D.C. area

"Warm climate" average

10

31.5 63 125 250 500 1000 2000 4000 8000

BAND CENTER FREQUENCY (Hz)

Figure E3 . The solid curve corresponds to the computed response of

a "warm climate" filter having the circuit of Fig. E2

and circuit parameter values of a= 0.3043, t= 0.000749,

and A = 0.1445. The symbols are described in the text,

The dashed curve corresponds to the computed filter

response from Fig. E2.

E-6
Table E. Tabulated values for smoothed filter response corresponding

to Washington, DC, area houses and to 'Warm climate" houses.

I

Frequency Filter Response (dB)

(Hz)

Washington, DC 'Warm Climate"

10 11.3 16.8

12.5 11.3 16.8

16 11.5 16.8

20 11.7 16.8

25 12.0 16.9

31.5 12.4 16.9

40 13.1 16.9

50 13.9 17.0

63 14.9 17.1

80 16.3 17.3

100 17.7 17.6

125 19.2 18.0

160 21.1 18.5

200 22.8 19.2

250 24.5 20.1

315 26.3 21.0

400 28.1 22.1

500 29.7 23.2

630 31.2 24.1

800 32.6 25.0

1000 33.7 25.6

1250 34.5 26.1

1600 35.2 26.5

2000 35.7 26.7

2500 36.0 26.8

3150 36.3 26.9

4000 36.4 27.0

5000 36.5 27.1

6300 36.6 27.1

8000 36.6 27.1

10,000 36.6 27.1

12,500 36.6 27.1

16,000 36.6 27.1

20,000 36.6 27.1

^7
NBS-114A (REV. S-7S)

U.S. DEPT. OF COMM. HBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBS TN 1113-2 '•4> ^A; A

A.

4. TITLE AND SUBTITLE Highway Noise Criteria Study: Outdoor/Indoor Noise Isolation

7. AUTHOR(S)

Paul R. Donavan, Daniel R. Flynn, and Simone L. Yaniv

^^^WWWPW

5. Publication Date

Augnfsr 198n , *. I»erfei^fng Otganijatkm Code

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

10. PnliCt/Tam/^^ ibH m.

11. Contract/Grant No.

6-3-0154

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS rSfr«(, City, st^ie, ZIP) U. S. Department of Transportation

Federal Highway Administration

Office of Research, Environmental Design and Control

Washington, DC 20590

13. Type of Report & Period Covered Final

>^«. !^<»i»»lfl|; Ag«>cy CoKle

15. SUPPLEMENTARY NOTES

I I Docurnent describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibiiogrepby or

literature survey, mention it here.) This report documents a series of measurements of the outdoor-to-indoor

noise isolation provided by nine houses in the Washington, DC, area. These

measurements were carried out as part of a large research program developed to

identify and quantify the important physical parameters which affect human response

to time-varying traffic noise and to investigate various procedures for rating

such noise so as to enable reliable predictions of subjective response to the

noise. While a small truck was driven past each test house, simultaneous

recordings were made of the sound level at three outdoor microphones and at

four indoor microphones (three of which were positioned at representative

listener positions) . These recordings were analyzed to yield one-third octave

band sound levels as functions of time and from these levels outdoor-to-indoor

level differences were computed. Analyses are given of the influence of different

experimental variables. It is found that microphone placement, both indoors

and outdoors, is the major source of measurement uncertainty. The data from this

study are in good agreement with sound isolation data reported in the literature

for houses in colder climates.

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; building acoustics; environmental pollution; noise control;

noise isolation; sound

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