NBSIR 73-191

Acoustical Evaluation of a Single Family

Attached Wood-Frame Modular Housing

System Constructed on an Operation

Breakthrough Prototype Site

Thomas L. Quindry

Applied Acoustics and Illumination Section

Center for Building Tectinology (Building Research Division)

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

April 1973

Final Report

Prepared for Office of Research and Technology

Department of Housing and Urban Development

Washington, D. C. 20410

NBSIR 73-191

ACOUSTICAL EVALUATION OF A SINGLE FAMILY

ATTACHED WOOD-FRAME MODULAR HOUSING

SYSTEM CONSTRUCTED ON AN OPERATION

BREAKTHROUGH PROTOTYPE SITE

Thomas L. Quindry

Applied Acoustics and Illumination Section

Center for Building Technology (Building Research Division)

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

April 1973

Final Report

Prepared for Office of Research and Technology

Department of Housing and Urban Development

Washington, D. C. 20410

U. S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

MATiONAL BUREAU OF STANDARDS, Richard W. Roberts. Director

Acoustical Evaluation of a Single Family Attached

Wood-Frame Modular Housing System Constructed

On An Operation BREAKTHROUGH Prototype Site

by

Thomas L. Quindry

Applied Acoustics and Illumination Section

Building Research Division

ABSTRACT

The acoustical performance of a single family attached wood-frame

modular housing system was tested on an Operation BREAKTHROUGH prototype

site.

Test results are given concerning the noise isolation of intradwelling walls and floor-ceilings, as well as the noise levels within

living units.

Key Words: Acoustics; field impact insulation class; noise criterion

curve; noise isolation class; Operation BREAKTHROUGH

i
TABLE OF CONTENTS

• Page

Abstract i

1. Introduction. 1

2. Objective 1

3. Test Procedure , 2

4. Description of Housing System 5

5 . Test Results 6

5.1 Noise Isolation of Intra-Dwelling Walls 6

5.2 Noise Isolation of Intra-Dwelling Floor-Ceiling. ... 6

5.3 Noise Levels Within Living Unit 7

6. Observations 7

Table 1 8

Table 2 . . . 9

ii
1. INTRODUCTION

Drawings and specifications for the housing systems being demonstrated as a part of Operation BREAKTHROUGH were reviewed in order to

determine the acoustical performance of the dwelling units. Any potential

deficiencies in acoustic performance were noted such that appropriate

action could be taken prior to manufacture and site installation of

the housing units.

Poor workmanship, however, can negate even the best planned

acoustical improvement. The many unknowns associated with workmanship,

possible damage to the housing modules during shipment, assembly of

the housing modules on the building site, and even the modular concept

of construction typical of many of the Operation BREAKTHROUGH housing

systems, emphasized the importance of performance testing.

More builders than ever before are now at least aware that acoustic

quality in buildings is becoming an essential consumer requirement. A

great deal of information can ultimately be drawn from the acoustical

performance testing of Operation BREAKTHROUGH housing.

2. OBJECTIVE

The objective of this work was to obtain information regarding

interior noise levels and the intra-dwelling noise isolation provided

by this prototype housing system constructed within the Operation

BREAKTHROUGH Program on one of the prototype sites, and to provide this

information as a data base for possible comparison with the acoustical

performance of conventional housing.

1
3. TEST PROCEDURE

All tests were performed in accordance with the methods outlined

in the appropriate standards. The pertinent tests include:

Appendix Al of ASTM E 336-71, "Recommended Practice for the

Measurement of Airborne Sound Insulation in Buildings."

ASTM E 413-70T, "Tentative Classification for Determination of

Sound Transmission Class." (This test method is used for the

determination of Noise Isolation Class.)

ASTM RM 14-4, 1971, "Proposed Tapping Machine Method for

Laboratory Measurement of Impact Sound Transmission

Through Floor-Ceiling Assemblies."

ASTM C 423-66, "Standard Method of Test for Sound Absorption

of Acoustical Materials in Reverberation Rooms," Section 9.1,

for measurement of decay rate procedure.

ANSI SI. 2-1962, "ANSI Standard Method for the Physical Measurement of Sound."

All measurements were carried out using the NBS Mobile Acoustical

Laboratory^^ . A complete list of the equipment utilized for these

measurements is given in Table 1.

Airborne noise reductions were measured using 1/3-octave bands

2/

of pink random noise— to excite the speaker systems. A multiplex

system which scanned the outputs of the microphones was used for

simultaneous spatial averaging in both the source and receiving rooms.

The output of the multiplexer was passed through a 1/3-octave bandpass filter set and then to the measuring system.

(1) Winzer, George E. , National Bureau of Standards Mobile Acoustical

Laboratory, Sound and Vibration, May 1970.

(2) Pink random noise is a quantity (e.g., sound pressure) whose

amplitude probability is a normal (Gaussian) distribution curve

and whose frequency spectrum slopes at minus 3 dB per octave.

2
A total of six microphones, in a modified spherical array as

shown in Figure 1, was used in all rooms.

Temporal averages of sound pressure levels were obtained using

a true root-mean-square voltmeter in order to obtain less statistical

error in sound pressure levels than can be obtained with the graphic

level recorder recommended in ASTM E 336-71. A differential amplifier

was used with two true r.m.s. voltmeters to obtain the differences in

the r.m.s. sound pressure levels of the random noise between the source

and the receiving room. Airborne noise reduction determination averaging times of 100 seconds for tests at frequencies from 125 through 400

Hz and 30 seconds for tests at frequencies from 500 through 4000 Hz

were used in order to achieve a statistical error (due to temporal

averaging) of less than +0.4 dB (at a confidence level of 95 percent).

The uncertainty in measured sound pressure levels, due to random

and systematic uncertainties associated with the over-all data acquisition system, is estimated (95 percent confidence level) to be less than

4- 1 dB for relative sound pressure levels (measured to determine airborne noise reductions) over a range of band-center frequencies from

100 to 4000 Hz. ASTM E 336-71 specifies that for suitable accuracy in

determining the average sound pressure levels in the source and receiving

rooms the rooms shall be large enough that there are at least 10 normal

modes per measurement bandwidth. The lower limit of frequency for which

this would occur using 1/3-octave bands was: 225 Hz for the bathroom

and 155 Hz for the bedroom.

3
For the airborne noise reduction measurements, as well as for

impact sound transmission measurements , the background noise in the

receiving room was at least 10 dB below the transmitted signal. The

equivalent sound absorption of the receiving rooms was determined by

the reverberation decay method described in ASTM C 423-66.

For the measurement of impact sound transmission through the

floor-ceiling assembly, the same modified spherical array, multiplex

system and true root-mean-square voltmeter were used. The output of

the voltmeter was recorded with a graphic level recorder. The positions

for the tapping machine are shown in Figure 1. The tapping machine was

positioned according to those positions suggested by ASTM RM 14-4, 1971,

where space permitted.

Measurements of noise levels of certain mechanical eauipment

were carried out for comparison with the Noise Criterion (NC)

3/ contours— . An octave band-pass filter set and graphic level recorder were used for these measurements. The background noise in the

receiving room was at least 10 dB below the sound pressure level of

the equipment being measured.

During the field measurements the temperature was nominally

66° F and the relative humidity 41%.

(3) Schultz, T. J., "Noise Criterion Curves for use with the USASI

Preferred Frequencies," J. Acoust. Soc. Am. 43, 637-638 (1968)

4
4. DESCRIPTION OF HOUSING SYSTEM

The housing system which was tested was classified as a single family

attached housing system. It consisted of a two story building made up

of first and second floor modules. The floor plan of the living unit

tested, which was an end unit, is shown in Figure 1. Adjacent units

contained different floor plans.

The three modules comprising this living unit contained respectively:

(1) a dining area, two bedrooms, and a bathroom

(2) a living room, kitchen, mechanical room, and stairway

(3) two bedrooms and a bathroom.

The living units were unfurnished except for floor coverings and

kitchen equipment.

The first floor modules were placed over a full basement.

A cross-section of the floor-ceiling assembly is shown in Figure 2.

The floor ceiling assembly consisted of 2 x 8 (nominal) wood joists

located 16 inches on center with a 5/8-inch plywood subfloor. The

ceiling joists were spaced 3-1/2 inches from the bottom of the floor

joist and consisted of 2 x 6 (nominal) wood studs located 16 inches

on center with 1/2-inch gypsum drywall on the room side.

The intradwelling walls within a module were of conventional construction built of 2 X 4 (nominal) wood studs ]*ocated 16 inches on center

with 1/2-inch gypsum drywall on each side. Interior doors were of a

hollow core wood construction and were undercut approximately 3/4 inch.

The gas fueled, warm air circulation HVAC system was located on the

first floor in the area between the living room and kitchen as shown in

5
Figure 1. The single cold air return register, which was located near

the floor, controls the flow of return air to the HVAC unit through a

short duct run of approximately 12 inches.

5. TEST RESULTS

j 5.1 Noise Isolation of Intra-Dwelling Walls

Each measured noise reduction was normalized to a reference re2 2 ceiving room absorption, , of 10 m (100 ft ) according to the

following equation:

NR^ = NR - (10 log^Q I

) o where NR = Normalized noise reduction

n NR = Noise reduction before normalization

A = Total sound absorption of the receiving space.

The results of measurements of the normalized noise reduction

between the bathroom and the horizontally adjacent back bedroom are

shown in Figure 3. The three-segmented solid line represents the Noise

Isolation Class (NIC) contour fitted to these data according to the

specified procedure in ASTM E 413-70T. The dotted line points to the

normalized NIC value. The normalized NIC value obtained is also given

in Table 2.

5.2 Noise Isolation of Intra-Dwelling Floor-Ceiling

The results of measurements of the normalized noise reduction

between kitchen and vertically adjacent back bedroom are shown in

Figure 4. The impact noise isolation was measured between two second

floor rooms and the kitchen; (a) a carpeted back bedroom and (b) a bathroom with vinyl-covered floor. The impact sound pressure levels were

6
normalized according to the procedure stated in ASTM 14-A , 1971. The

normalized impact sound pressure levels vs. frequency are shown in Figures

5 and 6 for these two cases. These figures also include the Impact

Insulation Class (IIC) contour fitted to these data according to the

specified procedure in ASTM RM 14-4, 1971. The normalized NIC value

and IIC values obtained are given in Table 2.

5.3 Noise Levels Within Living Unit

The noise levels in both the living room and kitchen with the

heating system in operation are given in Figures 7 and 8, along with

the Noise Criterion contours (NC)

.

6. OBSERVATIONS

During the tests of the housing unit two conditions were observed

which affected its acoustical quality:

(1) Due to the proximity of the HVAC system installation noirmal

conversation was difficult in the living room when the system

fan was in operation.

(2) Some of the walls in the second floor module did not quite

meet the ceiling, leaving gaps of 1/8- to 1/4-inch which

could be possible "f lanking-paths" for sound.

7
Table 1

^

Instrumentation*

1. Bruel & Kjaer 1402 Random Noise Generator

2. (3) Bruel & Kjaer Models 1612, 5004 Band-Pass Filter Sets

3. JBL Speaker Systems

4. (2) Bruel & Kjaer 2606 Measuring Amplifier

5. (2) Bruel & Kjaer 215 RMS Converter & Log Amplifier

6. (2) Bruel & Kjaer 221 Microphone Energizer - Multiplexer

7. Bruel & Kjaer 2305 Graphic Level Recorder

8. (12) Bruel & Kjaer 4132 Condensor Microphones

9. (12) Bruel & Kjaer 2619 FET Preamplifier

10. (2) Bruel & Kjaer 4220 Pistonphone

11. Bruel & Kjaer 3204 Tapping Machine

12. NBS Differential Amplifier

13. NBS Reverberation Time Measuring System

14. HP 5325 A Counter

* Commercial instruments are identified in this report in order to

. adequately specify 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.

8
Table 2

The measured noise isolation characteristics of the housing system

Partition

Source Room

Unit

Receive Room

Unit

Normalized

NIC

Normalized

lie

(Mean)

Intra-dwelling

Wall

Bathroom

09-SPA/03-16

Bedroom

(Back)

09-SFA/03-16

30 —

Intra-dwelling

Floor/ Ceiling

Kitchen

09-SFA/03-16

Bedroom

(Back)

09-SFA/03-16

29 —

Intra-dwelling

Floor/Ceiling

Bedroom

(Back)

09-SFA/03-16

Kitchen

09-SFA/03-16

61

Intra-dwelling

Floor/Ceiling

Bathroom

09-SFA/03-16

Kitchen

09-SFA/03-16

33

Equipment

Receive Room

Unit NC

Heater on Living Room

09-SFA/03-16

<60

Heater on Kitchen

09-SFA/03-16

<55

9
^ BACK X- BEDROefM

EXTERIOR WALL

DN

BATH

4>

MICROPHONE POS. (TYP)

ISO TAPPING MACHINE POS. (TYP)

— INTER- DWELLING WALL

FRONT

BEDROOM

MODULE

(2nd Floor

)

LIVING ROOM

MODULE

(1st Floor )

MODULI

(1st Floor

SPEAKER LOCATION (TYP)

EXTERIOR WALL

inter-\dwelling wall

gure 1. Floor plans of housing system showing microplaane, speaker, and

tapping machine positions tested.

10
11
<

>

<:H

o

I Q

M

H

Q

W

N

O

O

I—

I

H

CJQ

W

W

i-i O

125 250 500 IK 2K 4K

FREQUENCY, Hz

(NORMALIZED TO Ao = 10 METRIC SABINS)

Figure 3. Normalized 1/3-Octave Band Noise Reduction Between a Bathroom and a Back Bedroom Separated by an IntraDwelling Wall. Unit 09-SFA/03-16 (NIC - 30).

12
I'M' nr-^

r-^T

60 —

50 —

10_

I I I I I I I I I I I I I I I L

125 250 500 IK 2K 4K

FREQUENCY, Hz

(NORMALIZED TO Ao = 10 METRIC SABINS)

Figure 4. Normalized 1/3-Octave Band Noise Reduction Between a Kitchen and a Back Bedroom Separated by an IntraDwelling Floor-Ceiling Assembly. Unit 09-SFA/03-16

(NIC - 29 )

13
o

H

< S

M 3. Q

<:

PQ>

<

HU

O

I o

OS

QW

M

O

o

CNI

XIW

>

w

w

CO

CDw

Pi

Pu

FREQUENCY, Hz

(NORMALIZED TO Ao = 10 METRIC SARINS)

Figure 5. Normalized 1/3-Octave Band Impact Sound Pressure Level

Between a Back Bedroom and Kitchen Separated by an

Intra-Dwelling Floor-Ceiling Assembly. Unit 09-SFA/03-16

(IXC - 59)

.

14
Figure 6. Normalized 1/3-Octave Band Impact Sound Pressure Level

Between a Bathroom and a Kitchen Separated by an Intra

Dwelling Floor-Ceiling Assembly. Unit 09-SFA/03-16

(lie - 33) .

15
16
63 125 250 500 IK 2K 4K 8K

FREQUENCY, Hz

Figure 8. Octave Band Sound Pressure Level in the Kitchen of

Unit 09-SFA/03-16 with the Heating System Running.

( <NC - 55) .

17

FORM NBS-1 14A 1) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

i. PUBLICATION OR REPORT NO.

N'ESIR 73-191

2. Gov t Accession

No.

3. Recipient's Accossion

4. TITLE AND SUBTITLE

Acoustical Evaluation of a Single Family Attached Wood-Frame

Modular Housing System Constructed on an Operation

BREAKTHROUGH Prototype Site

5. Publication Date

6. Pc-rf'^rmin Or gan izaf i on Coic

7. AUTHOR(S)

Thomas L. Quindry

8. Performin.g Organization

NBSIR 73-191

9, PERFOR.MING ORGANIZATION NA.ME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Proiect/ Task, Aork Unit .\o 4600441

11. Contract/Grant .No. IAA-H-16-70

12. Sponsoring Organization Name and Address

Office of Research and Technology

Department of Housing and Urban Development

Washington, D.C. 20410

13. Type of Report &c Period Covered

Final

14, Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) The acoustical performance of a single family attached wood-frame modular housing

system was tested on an Operation BREAKTHROUGH prototype site.

Test results are given concerning the noise isolation of intradwelling walls and

floor-ceilings, as well as the noise levels within living units.

17. KEY WORDS (Alphabetical order, separated by semicolons)

Acoustics; field impact insulation class; noise criterion curve;

noise isolation class; Operation BREAKTHROUGH

18. AVAILABILITY STATEMENT 21. NO. OF PAGES

HUNLIMITED.

I i FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Pr

USCOMM-DC 66244. P71