SOUND INSULATION EVALUATIONS OF SEVERAL SINGLE-ROW-OF-WOOD-STUD PARTY WALLS UNDER LABORATORY AND FIELD CONDITIONS

USDA FOREST SERVICE RESEARCH PAPER FPL 241 1975

U.S. DEPARTMENT OF AGRICULTURE FOREST SERVICE

FOREST PRODUCTS LABORATORY MADISON, WIS.

Abstract Adequate party wall design for multifamily

dwellings requires an STC > 45. A standard stud wall consisting of a single layer of 1/2- or 5/8-inch gypsum board directly attached to each side of the studs will give an STC = 32 to 37. If insulation is placed in the stud cavity and at least one gypsum board face is decoupledfrom the studs, a potential for STC values up to 50 exists. Although STC values over 50 can be obtained with double-row-of-stud constructions using a single layer of gypsum board on each side, the added space and material require-ments make the single-row-of-stud construction economically desirable.

This study evaluates four different types of single-row-of-stud designs under both laboratory and field test conditions. LaboratorySTC values for the single layer of 5/8-inch gyp-sum board constructions ranged from 39 to 47. The STC = 47 (6.4 lb/ft 2 ) showed a potential for providing field values up to FSTC = 49 when test environment factors were taken into ac-count. The one wall studied with multiplelayers of 1/2-inch gypsum board on each side (11.6 lb/ft 2 ) had a laboratory STC = 56. Similar performance in the field would be possible in the absence of flanking.

In addition the overall performance of single-row-of-stud walls under field conditions was found to:

(a) Be influenced by variable installation techniques of the gypsum board decouplers.

(b) Give, in the absence of flanking, field FSTC values two to four points higher than laboratory STC values under certain com-binations of test environment and wall design.

(c) Require a good bounding structure flanking limit if a field FSTC > 45 is to be ob-tained with a laboratory STC = 45 to 50.

(d) Be potentially sensitive to perimeterleaks such as at the gypsum board base.

The use of trade, firm, or corporation names in this publica-tion is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture of any product or service to the exclusion of others which may be suitable.

SOUND INSULATION EVALUATIONS OF SEVERAL SINGLE-ROW-OF-WOOD-STUD PARTY WALLS UNDER LABORATORY AND FIELD CONDITIONS

ByROBERT E. JONES, Physicist Forest Products Laboratory,1

Forest Service U. S. Department of Agriculture

Introduction

Noise, along with other forms of pollution,is receiving increased public attention. Residen-tial acoustical privacy is no exception where the increase in noise due generally to populationgrowth and mechanical devices can be aggravated by the improper use of buildingmaterials. The trend to multifamily dwellingswith their associated “party” walls and “party”floor-ceilings provides a special challenge to privacy. These “party” boundaries for livingunits are particularly sensitive acoustically due to the proximity of the occupants of adjacentunits, and practical sound insulation designprovides privacy only to the level of the raised voice. Also, the noise (unwanted sound)radiated from a party wall is particularlyfrustrating to the receiver since he normally has no control over the duration or frequency of oc-currence. By contrast, considerable tolerance may exist for similar noises originating within the occupant’s own dwelling unit.

An important criterion in determining the airborne noise privacy between adjacent living areas is the Sound Transmission Class (STC), as defined in ASTM E 413 (3).2 For example,the HUD Minimum Property Standards for

Multifamily Housing (15) requires STC > 45 for living unit to living unit. A wall with an STC = 50 can perform significantly better. A single-row-of-wood-stud wall with a single laver of gvpsum board directly attached to both sides of the studs has an STC = 32 to 37 and is inade-quate acoustically for party wall constructions. For the single-row-of-stud wall, significant STC improvement up to about 50 can occur when one or both of the gypsum board faces are mechanically decoupled from the stud and in-sulation placed in the stud cavity. The broad objective of this study was to investigate under both laboratory and field test conditions several of these constructions which, on the basis of published laboratory tests, would give STC values greater than or equal to 45. The publish-ed laboratory data for these walls suggestedgood sound insulation performance and emphasized the economies in both space (wallthickness) and material efficiencies when com-pared to double-row-of-stud walls. 1Maintained at Madison Wis., in cooperation with the

Univeristy of Wisconsin. 2Numbers in parentheses refer to Literature Cited ut end

of report.

1

However, no field data were available for two of the three walls originally planned for the study(a fourth wall was added as part of the field test site evaluation), so that field determinations were essential to the work.

The four types of walls studied along with the gypsum board decouplers are listed in table 1. Also noted are published fire resistance ratings as well as published laboratory and field sound insulation data. Wall B, a common field construction for which limited published field data are available, was included as a control. Walls C and D used wood-base panel materials for gypsum board decouplers and no field data were available.

In order to both verify existing laboratorydata and provide values for matched materials and assembly techniques, a single test for each wall was made at Riverbank Acoustical Laboratories, Geneva, Ill. This was also impor-tant because the published laboratory data from two different laboratories for wall B (con-trol) did not appear to agree with each other (see table 1). The field data were obtained in a duplex housing unit rented by Forest Products Laboratory to conduct this study3 .

In summary, the purposes of this study were to:

1. Obtain classical laboratory data on the four test walls to determine representativelaboratory values for the construction including a comparison of these data with some previous-ly published data, as available, as well as field

(duplex) test replication data. 2. Obtain replicate field data in a rented

duplex living unit, noting factors that affect the partition sound transmission and the influence of flanking transmission and test environment on results.

3. Compare laboratory and field results and note relationships between them. Important to this objective was careful matching of materials and wall erection procedures, as well as good in-strumental and procedural testing techniques.

4. Establish overall performance of single-row-of-stud walls, noting their capabilities and limit ations.

In the analyses of the laboratory and duplex data a series of unexpected and useful results were found that can significantly changeestablished concepts of laboratory and field transmission loss testing. Because these theoretical and empirical findings were exten-sive and complicated a separate publication(10) was written to cover them. This presentpublication is a less technical companion report emphasizing the performance of several single-row-of-stud party walls under laboratory and field test conditions.

We appreciate the financial cooperationprovided by the American Hardboard Associa-tion and the Acoustical and InsulatingMaterials Association. Appreciation is also given to U.S. Gypsum Company for furnishingthe gypsum board and to the Masonite Corpora-tion for furnishing the hardboard.

Sound Insulation Potential of Single-Row-of-Stud Walls

In order to understand the data and sion Class (STC) or Field Sound Transmission analysis for this study, certain concepts are Class (FSTC) as appropriate to the data. The necessary. It is the purpose of this section to solid line contour in figure 1 shows how the present these concepts in elementary ways and rating system works. The rating system is, in thus assist the reader in the later sections. general, a valid one and the STC or FSTC can

An airborne sound insulator, such as a par- be related to privacy as shown by Northwood ty wall, performs its function by maintaining (11) and Young (18). The circumstances where acoustical separation between adjoining enclos- problems can develop is where the STC rating ed spaces. The effectiveness of the sound in- contour is eight-point deficiency limited at one sulator can be quantified by obtaining the frequency and with a low total deficiency count. transmission loss, TL, in dB4 as described in ASTM E 90 (4) for laboratory tests and E 336 (6) for field tests. The transmission loss can be 3 I wish to thank Earl Geske for his contribution to this

work in supervising the construction of the walls atplotted against frequency as shown in figure 1, the duplex and Riverbank Acoustical Laboratory, asnoting that increased transmission loss well as conducting the transmission loss tests at the represents increased sound insulation. A single duplex. number rating scheme. as described in ASTM 4 All sound pressure level measurements in dB are referenced E 413, can he used to obtain a Sound Transmis- to 2 x 10-5 Newtons per square meter.

2

Tabl

e 1,--S

umm

ary

of

wal

l co

nstru

ctio

ns 1

and

publ

ishe

d fir

e an

d ST

C

valu

es

Figure 1.-Example of lab airborne transmission loss vs. frequency for acoustically de-signed single-row-of-wood-stud wall. Solid line contour shows sound trans-mission class. STC, rating position for these data. The STC rating contour deficiencies at each frequency are ob-tained by subtracting the TL values below the rating contour from the rating contour itself. The deficiency points are shown in the boxes with the total. *, to the right. The rating contour is placed as high as possible without exceeding a total of 32 deficiency, points, and with no more than right points at any one frequency. The horizontal dashed line shows the FSTC value corresponding to 500 Hz for the rating contour. M 142 438

In this case, the rating system can be overly sen-sitive to variability in test results and may be overly severe with respect to privacy as shown by Clark (8). Examples of this are discussed in the Results section,

To get STC ratings of 45 or over with lightframe constructions (surface weight < 20 pounds per square foot (lb/ft 2 )) an acousticallydesigned wall is required. Two types of design are single leaf and double leaf walls. A singleleaf wall design is defined as a design for which the entire thickness of the wall acts as an in-

tergral structure over most of the frequency range of sound excitation. Examples of this are single plywood and gypsum board panels as well as concrete block walls. In a double leaf designthe two leaves do not act integrally over most of the frequency range, though they may be acoustically coupled to each other by an air cavity separating them. An example of this would be a double-row-of-stud wall (e.g., 1-in. separation between the two rows of studs and plates).

To understand the advantages of double leaf over single leaf design, a comparison of the mass law performance of single leaf walls with tvpical double leaf performance is useful. The usual mass law for limp materials states that the transmission loss, TL, increases 6 dB when either the surface weight or frequency is doubl-ed. It is given by:

TL = 20 log fw - 33.5 (1)where f is frequency, Hz; and

w is surface weight, lb/ft2 .

Figure 2.-Transmissionloss, TL, us. frequency for theoretical field incidence mass law at 3 lb/ft2 . Mass law, is TL = 20 log fw - 33.5 where f is the frequentcy in Hz and w the surface weight in lb/ft2. The STC rating contour deficiency points are shown in the boxes with the total deficiencies, *, to the right. M 142 439

4

A plot of TL versus frequency is shown in figure2 for a surface weight of 3 lb/ft 2 . If we vary sur-face weight and obtain the STC, we obtain figure 3 where for the theoretical mass law the STC increases six points for every doubling of surface weight. For materials with sufficient limpness, such as 1/8-inch hardboard, the mass law of equation (1) can be obtained experimen-tally (14, p. 9). For materials like 518-inch gyp-sum board, a particular type of resonance oc-curs due to its stiffness. This resonance is due to

the coincidence of the speed of sound for air and the speed of sound for the material being ex-cited. This coincidence effect occurs over a range of frequencies and results in a departurefrom theoretical mass law, as shown in figure 4, referred to as a coincidence dip. The lowest point in the dip is typically in the 2,500 Hz third octave band width for 518-inch gypsum board and 3,150 Hz for 1/2-inch gypsum board. As il-lustrated in figure 4, any type of resonance con-dition detracts from the mass law performance.

Figure 3.-Graph of theoretical (see also fig 2) and experimental field incidence mass laws (shaded area) expressed as sound transmission class vs. panel or partition surface weight, w. Examples of typical constructions are also shown. The experimental mass law is based on a plot of average transmission loss vs. surface weight by Cook and Chrzanowski (9), adjusted +2 dB to approximate STC via ASTM E 413 (6). Shaded area is ±1 dB with respect to STC = 14.5 log w + 2.5 and indicates approximate nature of relationship. M 142 440

5

Figure 4.-Transmission loss vs. frequency for 5/8-inch gypsum board. Note coincidence dip centered on 2,500 Hz. Data obtained by Sharp (14. p 69). FSTC deficiencies for the rating contour are shown in the bores with the total deficiencies, *, to the right. M 142 441

The existence of various resonance con-ditions (as well as shifts from bending to shear wave propagation in the partition (14, p.12-16)) result in an experimental mass law as shown in figure 3. For the experimental mass law above 1 lb/ft2 a doubling of surface weight results in an increase of 4.5 STC points.A 100-lb/ft 2 9-inch brick wall will give an STC = 52, which conforms to experimental mass law performance. Similarly, an 8-inch hollow concrete block wall at 33 lb/ft2 will give an STC = 45. Again, 5/8-inch gypsum board at a surface weight of 2.5 lb/ft2 will give an STC = 30. Thus, it can be seen in figure 3 that at a 20-lb/ft2 limit for light frame construction the STC would be limited to values under STC = 45.

When a double leaf design is used, a much improved TL response can be obtained as shown in figures 3 and 5. With 2 inches or more of insulation in the cavity and adequate cavitythickness, the double leaf STC performance can be nearly twice the STC for each leaf. For

example, if two pieces of 112-inch gypsum board at 2.0 lb/ft2 (STC = 28) were spot laminated 12 inches on center, the resulting STC of this single leaf construction would be 34 (14, p.69). In a double wall construction (2 in. of insulation in 6- to 8-in. cavity) an STC > 50 could be obtained with the same amount of gypsum board. Thus, double leaf design has a clear TL advantage over single leaf designwhere an acoustically designed double-row-of-stud wall at 6 to 8 lb/ft2 will perform better than an 8-inch light weight concrete block wall at 33 lb/ft2 .

Figure 5-Schematic transmission loss vs. frequency for single leaf (lower dashed line) and double this transmission loss (upper dashed line), including effects of critical frequencies, fc . The solid lines indicate double-leaf transmission loss for a typical wall with no insulation in cavity (curve a) and some insulation, perhaps 2 inches thick (curve b) in the cavity. The solid line curves also show the effect of the double-leaf resonance frequenty, fo . Curves adapted from Vér and Holmer (17). M 142 442

Single-row-of-stud walls with the gypsumboard directly attached perform at about mass law with STC = 32 to 37 depending on the gyp-sum board and assembly technique. An exam-ple is shown in figure 6 where a standard stud wall using 5/8-inch gypsum board gave an STC = 32. Also shown in figure 6 are the effects of

6

between the gypsum board leaves decreases the TL performance, controlled bridging can provide STC > 45 and take advantage of the smaller thickness for the single-row-of-stud wall. The minimum thickness of the stud cavitydoes place a restriction on the potential of single-row-of-stud walls. At a 3.5-inch stud cavity the double leaf cavity resonance of the wall (see fig.5) for 518-inch gypsum board is about 80 Hz which places the low frequency TL response in the 18 dB per octave range resulting in the STC rating being controlled by the 125 Hz TL value. This provides a basic limitation for this type of design. and the effects will be noted in the data analysis.

The single-row-of-stud constructions tested for this study are examples of various techni-ques for mechanically decoupling the gypsumboard faces from each other, within the limitations intrinsic with single-row-of-stud constructions. An additional restriction is plac-ed on these constructions by fire performancerequirements. In order to pass ASTM E 119 (5).including the hose test, drywall screws on 24-inch centers are generally considered necessaryfor adhesively applied facings.

The above discussion has concerned the TL Figure 6.-Graph transmission loss vs. fre-

quency showing the effects of adding per-imeter connections and studs 16 inches on center to double leafs of 5/8-inch gypsum board with 2 inches of insulation in a 4-inch cavity. The fully isolated and per-imeter bridge data were obtained at Wyle Laboratories (14) and the standard stud wall data (no insulation in cavity) are Riverbank Acoustical Laboratory test TL 68- 182. The STC rating contour deficiency points are shown in the boxes with the total deficiencies, *, to the right. M 142 443

removing first the studs in the field of the wall (STC = 49) and then all mechanical connec-tions between the faces (STC = 50). Between the TL response for the standard stud wall and for the direct perimeter bridge is a range of TL performance that can, experimentally, be ob-tained, depending on the amount of bridgingbetween the gypsum leaves.

The walls investigated for this study fall in this range between single leaf and double leaf design where the effectiveness of the decouplingof the gypsum board faces from the studs in the field of the wall determines the actual STC. While acoustical bridging across the studs

assuming that all significant intruding sound energy in a room is from the test partition under consideration and where the physicalcharacteristics of the room (e.g., room geometryand absorptive materials) do not interact with the test partition or the sound field itself. In real structures such as the FPL-rented duplex test facility we need to take account of both the flanking TL (transfer of sound energy between adjoining rooms by paths other than directlythrough the partition under consideration) and acoustic test environment effects. These topics are discussed in detail in reference (10). For this report a brief introduction to the concepts is provided.

A flanking TL (and corresponding FSTC) can be obtained experimentally in much the same way as can a partition TL (10). When the flanking TL is known it can be plotted as shown in figure 7 along with the partition TL. The separate contributions of the flanking and par-tition TL to the sound energy in the receiving room can be combined by a logarithmic process to give a field TL as also shown in figure 7. The field TL cannot exceed the flanking or partitionTL, whichever is lowest and can be lower, giv-ing a field TL curve that is very different from either the partition or flanking TL due to their influence. In this example the partition STC = 52 resulted in a field FSTC four points lower due to flanking interaction.

In the absence of flanking, the partition TL

7

Figure 7. -Transmission loss, TL, vs. fre-quency, showing the field TL data result-ing from the mutual contributions of the partition and flanking TL. Note that the field TL can never exceed the flanking TL and that the field FSTC in this example is 3 points lower than the partition or lab STC. M 142 444

at most frequencies can be assumed to be the same as the laboratory TL for a replicate struc-ture. There are, however, some important ex-ceptions due to test environment effects sum-marized in figure 8. At low frequencies the field TL tends to be higher than laboratory TL values due to the difficulty in producing a true airborn wave motion when the wave length is of

Figure 8 --Graph of transmission loss, TL, vs. frequency, illustrating test environ-ment effects on partition TL that can occur at low5 frequencies (room geometry) and in a coincidence dip frequency range (absorptive room condition).

M 142 445

the order of magnitude of the room dimensions. At high frequencies when a coincidence dip oc-curs in the presence of absorptive material (such as carpet and pad, and drapes) the field TL again may be higher. Both of these effects will be noted in the Data Analysis sec-tion.

Research Materials

Wall Constructions Four types of single-row-of-stud walls were

investigated in this study. Detailed descriptionsof fastener schedules and adhesive application, are given in appendix I. Isometric drawings are shown in figure 9. Briefly, the constructions were as follows, starting with factors common to all the walls:

1. Framing consisted of 2- by 4-inch studs, 16 inches on center with single bottom platesand double top plates.

2. Kraft paper-backed glass fiber insulation (2-1/4 in. thick) was mounted in the stud cavities and stapled to the studs.

3. Gypsum board joints were treated with a quick drying prefill compound and then with

8

Figure 9.-Isometric drawings showing wall construction and types of gypsum board decoupling for this study: (A) resilient channels, both sides, (B) resilient channel, one side, (C) 1/2-inch hardboard, both sides, and (D) 112-inch sound deadening board both sides.

M 141 673

joint compound and tape in the usual manner, and the entire perimeter of the gypsum board which had 1/4- to l/2-inch gaps was sealed with a calking compound. The intersections of the test partition with adjacent walls and ceilings had a joint compound and tape treatment over the calking compound.

The unique factors for each wall were in the number of layers and mounting of the gypsumboard faces as shown in table 1.

The inclusion in this study of walls B, C, and D with single gypsum board faces was in-fluenced by the following factors:

1. The cost of these walls runs 12 to 25 per-

cent less than a double-row-of-stud wall, based on similar constructions in a report byPrestemon (13).

2. The thickness of the wall is about half that of double-row-of-stud constructions.

3. Performance of the walls was acceptablebased on published reports as summarized in table 1.

4. Walls C and D were constructions that were laboratory tested designs supported by the American Hardboard Association (2) and the Acoustical and Insulating Materials Association (1), respectively. The walls had never been field tested.

9

Tab

le

2 .-

-Sum

mar

y of

pr

oper

ties

for

wal

l co

mpo

nent

s

5. Wall B was a commercially used wall (12,16) and was originally included as a control.

Wall A is an FPL design for high STC per-formance on single-row-of-stud framing. The channels on both sides give added cavitythickness as well as isolating the facings from each other. The original purpose of the wall was to obtain the flanking characteristic of the duplex bounding structure. The wall achieved that purpose as well as providing an example of a high STC single-row-of-stud wall.

Since the purposes of the study included both field replication and laboratory-field data comparison, uniformity in the materials of con-struction and assembly detail were important.Yet, to also maintain the validity of the data as field tests, it was important to use commerciallyavailable materials as well as assembly prac-tices compatible with field installation. A balance between these competing objectives was achieved in the following ways:

1. Single lots of commercial materials, in-cluding the studs, hardboard, sound deadeningboard, and gypsum board were used. For typicalproperties see table 2.

2. The same FPL craftsmen were used for building all the walls. Partial walls were built prior to the test walls to familiarize the craftsmen with the special features of each wall.

3. The studs were pretested in flexure and those with a modulus of elasticity, MOE, out-side the range of 1.3 to 2.5 x 106 pounds per square inch or a crook of greater than 1/2 inch were culled. The remaining studs were statistically randomized based on the MOE with respect to position in the wall.

4. A commercial drywall screwgun was used to insert and dimple all screws, similar to field practice. Normal joint compound and tapeprocedures were followed, according to manufacturer’s published instructions.

Research Methods

Laboratory tests were conducted at River-bank Acoustical Laboratories (RAL), Geneva, Ill. The walls were constructed by FPL per-sonnel and tested by RAL personnel, in explicitcompliance with ASTM E 90 (4). The laboratory test method is well established, and no special test conditions were used, except that the walls were 8 feet high (as in the duplex)rather than 9 feet high as is commercially used in the laboratory. However, the precision of the laboratory test (expressed as 90 pct confidence limits) is required by E 90 to be ± 2 dB at 125 Hz and ± 1 dB at all other frequencies. The ap-parent lack of precision at 125 Hz will be impor-tant to part of the data analysis.

The FPL test instrumentation used for the field tests is of laboratory quality and includes both visual and auditory means for monitoringthe random noise source and microphone signalquality. Procedural and instrumentive details are included in appendix II of reference (10).

While the laboratory tests, for the walls studied. provide a non-interacting flankingtransmission and test environment, the field test facility provided various interactions. Bythe nature of field tests the room layout and fur-nishings can provide a variable test environ-ment, and the bounding structures for the test wall can provide a significant flanking trans-mission. The selection and characterization of the duplex test facility was an important steptoward providing a coherent analysis of the data

that were obtained. The selection criteria and full acoustical characterization of the duplexliving units are contained in reference (10). A brief acoustical description of those factors necessary to understanding the data analysisfollows.

The rented duplex met the test environ-ment requirements of E 336 including the room volumes and partition area shown in the planview of figure 10. The offset of the source and receiving rooms made the test wall sound radiating area somewhat indeterminate, but stethoscopic checks indicated that low frequen-cies, especially, decreased rapidly in the offset area so the area of the wall common to both rooms was used for normalization. The source and receiving rooms met the absorption re-quirement of E 336 with carpet and pad, and drapes in place. Two room conditions were used in the study. One is referred to as the “bare room condition” and the room layout is shown in figure 10. This consists of 112-inch plywooddoor blocks to define the room volume as in-dicated, and three fixed 112-inch plywood dif-fusors, 42 to 48 by 92 inches, located as in-dicated in the figure. The bare room condition simulates a laboratory test environment. The other is referred to as the “absorptive room con-dition” and is the same as the bare room condi-tion except the diffusors are removed and carpetand pad and 9 by 7 feet of closed drapes placedin the room. The absorptive room condition

11

Figure 10.-Plan view of FPL duplex source and receiving rooms showing room offset of test cavity and bare room condition layout. The bare room test setup consisted of a fixed diffusors, b, door blocks; c, microphone positions; and d, FPL speakers.

M 112 308

simulates furnished living space. Typicalreverberation time versus frequency curves for the two room conditions are shown in figure 11. The receiving room had a 3/8-inch urethane foam pad at 6.7 ounces per square yard and a 50 ounce per square yard shag carpet, wall to wall, except for the front door hall.

The test environment for the duplex was checked by testing a 1/8-inch hardboard parti-tion (coincidence dip frequency 10,000 Hz).Good limp mass law compliance was obtained under both hare and absorptive room con-ditions. with some exceptions at low and highfrequencies the effects of which are similar to those described in figure 8.

The flanking TL characteristic was ob-tained experimentally by testing a high STC wall which gave the results shown in figure 12A for laboratory and duplex data. Using the method described in reference (10), bare and absorptive room flanking TL limits were calculated as plotted in figure 12B from the data in figure 12A. From a stethoscopic surveyof' the hare room with wall A in place it was found that considerable midfrequency floor-floor flanking existed. This was to be expectedfrom the joist framing shown in figure 13 where the joists are nailed to a common header. Air-borne flanking through the basement was effec-tively blocked by t he dividing poured concrete

12

wall as evidenced by sound pressure level measurements. The difference in the bare and absorptive room flanking limits was due to the test environment effects on the coincidence frequencies of the 3/4-inch plywood subfloor and gvpsum board. The damping effect of the carpet and pad on the floor may also have been a factor.

With these characterizations of the duplex test environment and flanking limits we can proceed with the data analysis.

Figure 11. -Typical receiving room reverbera-tion time vs. frequency, for FPL rented duplex under bare room and absorptive room test conditions

M 112 309

Figure 12.-Transmissionloss vs. frequency data for wall A showing (A) the laboratory and duplex data from which (B) the duplex flanking limits were derived. The STC rating contour deficiency points are shown in the boxes in (A) with the total deficiencies at the right. M 142 446

13

Figure 13.-Vertical cross section of duplex party wall test cavity and, floor and ceiling bounding structures.

M 142 312

Analysis of Results

The test wall references, basic wall shown in figure 14A for all the FPL/RAL data. characteristics. and the single number ratings In addition to the wide range of STC values (39 under laboratory as well as bare and absorptive to 56) it can also be noted that there is con-duplex room conditions are given in table 3. The siderable diversity in TL frequency response detailed TL data at third-octave bandwidth curve shapes. For example wall B shows a large frequencies are given for each test in table 4. All coincidence dip, while wall C has none. If we the data were taken on walls that were fully note the deficiency points listed in figures 14B, sealed against airborne leaks or airborne flank- C, and D, it can be seen that the STC ratings for ing. The results of improper sealing and per- walls C and D are dominated by the eight-point missible leaks are discussed in reference (10). deficiency at 125 Hz. Because of this diversity

in both TL and STC values, this series of single-row-of-stud constructions provides a broad

Laboratory Data basis for the study of the various types of A composite plot of TL versus frequency is decoupling approaches used. This diversity will

14

Table 3. --Summary of test wall references, basic wall characteristics and single number ratings

also provide good examples of the interaction of and test methods to justify such a comparison. the duplex flanking TL limit and test environ-

Wall Ament with the partition transmission. As shown in table 1, published STC data The laboratory and duplex TL data for wall

exist for walls generically similar to FPL/RAL A (multiple lavers of gypsum board over B, C, and D which are about five STC points resilient channels) under bare room conditions higher than the FPL/RAL data. (There is also a (see also table 4) are plotted in figure 15A. The published result for wall B that is one STC absorptive room condition TL data are plotted point lower than FPL/RAL data.) While it is similarly in figure 15B. Note that the laboratory tempting to compare the higher published TL data do not exhibit a deep gypsum board coin-data with the present study, a detailed review of cidence dip, apparently due to some damping the test methods (prior to 1966) and construc- between the layers of gypsum board. Neither tions revealed too many variables and un- the laboratory nor field TL data resulted in any knowns with respect to both the constructions eight-point deficiency limited STC ratings or

15

Tabl

e 4.

--Tr

ansm

issi

on

loss

da

ta

at

16

1/3-

octa

ve

band

wid

th

cent

er

freq

uenc

ies

for

wal

ls

A,

B,

C,

and

D

Figure. 14.-Transmission loss vs. frequency, data for the laboratory data used in this study, including (A) a composite plot of the FPL/RAL data for walls A, B, C, and D, (B) a comparison of the FPL/RAL B data with previously published lab data, (C) FPL/RAL C data, and (D) FPL/RAL D data. The STC rating contour deficiency points are shown in the boxes for (B), (C), and (D) with the total deficiencies, *, to the right.

M 142 404

even high total deficiency point count, so that the STC values could not be affected by small variations in individual TL values.

When the hare room TL data for wall A are compared with the duplex hare room flankingTL limit in figure l5A (the derivation of the flanking limit is given in ref. (10)) a strong in-teraction can he seen. The duplex absorptive

room condition TL data also show a strong in-teraction with the flanking limit in figure 15B, except at high frequencies. This interaction was to he expected since the purpose of buildingwall A was to determine the duplex flankinglimit as shown in figure 12B.

Wall A is an example of a high STC single-row-of-stud wall, achieved through multiple

17

Figure 15.-Transmission loss vs. frequency data for wall A comparing FPL/ RAL lab data with duplex data under (A) bare room and (B) absorptive room conditions. STC and FSTC rating contour deficiency points are shown in the boxes of (A) and (B) with the total deficiencies, *, at the right.

M 142 447

gypsum hoard layers on resilient channels for both sides of the wall. While similar perfor-mance could he obtained with single layers of gypsum hoard in a double-row-of-stud wall, it would be at the expense of greater wall thickness. Although the mounting position of the channels may be important as discussed for wall B, a partition STC close to 56 would be the potential for general field installation.

With a high STC partition such as wall A a good bounding structure flanking FSTC is necessary to realize its potential. This would require an acoustical design for the framing as well as extra effort in following the design.However, a high STC wall can also assure that the field FSTC is kept close to the flankingFSTC as in the duplex where under absorptiveconditions the duplex FSTC = 51 was obtained for wall A-1A with a flanking FSTC only two points higher.

Wall B The laboratory TL data FPL/RAL B

(single-layer gypsum board with resilient channel decoupler on one side) are shown in figure 14B where it can be noted that while a deep coincidence dip exists, there are no eight-point deficiencies. The duplex data for wall B under hare and absorptive room conditions are shown in figures 16A and B, respectively, where somewhat different TL frequency responses are obtained.

Before comparing the laboratory and field data the replication of the field data needs to be considered. Duplex tests B-1B and B-1A were run first, and the results of FSTC = 43 and 45 under bare and absorptive room conditions were disappointing in comparison with published values up to STC = 52. The assembly technique was reviewed, and it was noted that a random orientation of the predrill-

18

Figure 16.-Transmission loss vs. frequency for wall B showing duplex data under (A) bare and (B) absorptive room conditions, and then comparing the corresponding lab data with duplex data under (C) bare and (D) a absorptive room conditions. The FSTC rating contour deficiency points are shown in the boxes for (A) and (B) with the total deficiencies, *. at the right.

M 142 528

19

ed holes in the channels was used for mounting to the studs. It was also noted that use of the predrilled holes gave increased flexibility to the gypsum board. As a result, the predrilled holes were alined with the studs for the duplex wall B-2 and the RAL test of wall B. Under this resilient channel mounting, the duplex data un-der absorptive room conditions showed a general TL increase of two points over much of the frequency range giving an FSTC = 47. The lack of response under bare room conditions (fig.16A) is due, in part, to the flanking interaction which will be considered shortly. Because of the difference in the duplex data for the two walls, and also because FPL/RAL B was assembled the same as duplex B-2, the latter is used for laboratorv- field correlations.

The laboratory and field (bare room condi-tion) TL data for wall B are plotted in figure16C, along with the corresponding duplex flank-ing limit. The substantial difference between laboratory and field TL data from 250 to 1,600 Hz is due to the flanking limit which reduces the laboratory STC = 47 to a field FSTC = 44. Much less flanking influence is noted under ab-sorptive room conditions in figure 16D. Because the duplex B-2A TL is higher than the laboratory data (see fig. 8 for explanation) in the gypsum hoard coincidence dip area the duplex FSTC = 47 is equal to the laboratorySTC value, despite some lowering of the parti-tion TL in the midfrequency range. In fact, if there had been no midfrequency flanking in-teraction. the field FSTC would have been 49, two points higher than the laboratory value due to test environment effects at low and high fre-quencies.

Wall B has demonstrated a potential for field FSTC = 45 to 50 when no flanking interac-tion exists. Test environment effects can in-crease its FSTC by two points over lab STC, perhaps compensating for some flanking. To ob-tain the full potential of the wall B design, the predrilled mounting holes of the resilient channels should be alined with the studs.

The laboratory and field TL data for wall B provide the basis for a coherent analysis. The STC = 46 data shown in figure 14B are very similar to the FPL/RALB data and were run in an ASTM E 90-66T laboratory.

Wall C The laboratory TL and FSTC = 44 data for

FPL/RAL C (hardboard decouplers) are shown in figure 14C where it can be noted that there is no gypsum hoard coincidence dip and the STC rating is dominated by an eightpoint deficiency

at 125 Hz. The absence of a gypsum board coin-cidence dip is apparently due to the laminated construction using a neoprene adhesive (seeappendix I).

The duplex TL data for wall C under bare and absorptive room conditions are shown in figures 17A and B, respectively. Under both bare and absorptive room conditions excellent replication was obtained for walls C-1 and C-3. However, wall C-2 gave unexpectedly better TL performance. When duplex wall C-2 was dis-mantled after testing a very poor adhesive bond was found between the hardboard and studs. Also noted were gaps of from 1/8 inch to 9/16inch between the studs and hardboard. When the next duplex wall C-3 was constructed, careful attention was given to the way the supplementary screws (24 in. on center) pulledthe gypsum board and hardboard into the studs. It was found that the screws not only did not draw the boards to the studs but actuallyhad a tendency to back the boards off the studs. This was because the screw withdrawal strengthof the hardboard was great enough so that it could dimple the drywall screw head into the gypsum board and activate the screw depth sen-sitive shutoff for the drywall screw gun. Thus, depending on how straight the studs were, how much flashing time is used on the adhesive, and how much pressure is applied to the screw gun, a highly variable mounting of the wall facings oc-curs. These data are included to show the potential variability of the wall. The data for wall C-2 are not included in the averages for this construction.

Using the average TL for walls C-1 and C-3, the field data under bare room conditions are compared with laboratory data for wall C in figure 17C. A substantial limiting of the field TL data above 500 Hz can be noted with the laboratory data intersecting the flankinglimit. However, the duplex average FSTC of 42 is determined by the 125 Hz TL value which does not show any flanking interaction. The duplex average FSTC = 44 under absorptive room conditions is also controlled by the 125 Hz TL value. Thus the good field performanceof wall C at other frequencies does not help the FSTC rating. Since the average TL for wall C did not show a coincidence dip, the coincidence dip phenomenon of figure 8 (under absorptive room conditions) is not found in figure 17C. The two-point difference in average FSTC values is apparently due to the low fre-quency phenomenon described in figure 8.

Based on these data wall C has demonstrated a potential for field FSTC = 42 to 44. Low frequency test environment effects have

20

Figure 17 -Transmission loss vs. frequency for wall C showing duplex data under (A) bare and (B) absorptive room conditions, and then comparing the corresponding lab data with the average duplex data under (C) bare and (D) absorptive room conditions. The FSTC rating contour deficiency points are shown in the boxes for (A) and (B) with the total deficiencies at the right. M 142 530

21

a potential for providing field performance in excess of the laboratory STC = 44. However, the low frequency performance of this wall design is very sensitive to the way the supplementary screws are inserted; FSTC values as high as 49 were obtained when the screws failed to seat the hardboard into the studs. It is expected that typical field potentialwould be approximately equal to the laboratorySTC = 44 when no flanking interaction exists.

Wall D The laboratory TL data FPL/RAL D (wood

fiber sound deadening board decouplers) are presented in figure 14D where it may be noted that a small gypsum board coincidence dip oc-curs, apparently due to the damping providedby the laminated construction (see appendix I).Significant is the low 125 Hz TL value which provides an eight-point deficiency which dominates the STC = 39 rating.

The duplex TL data for wall D under bare and absorptive room conditions are shown in figures 18A and B, respectively. Under both room conditions good replication of the duplexTL data was found. Average TL values for D-1, D-2, and D-3 are used for comparison with laboratory data in figures 18C and D.

Under bare room conditions the averageduplex TL data (see fig. 18C) show some flank-ing interaction from 630 to 1,000 Hz. However, since the FSTC value is controlled by the 125 Hz TL value, there is no significant flanking in-fluence on the FSTC rating. The good TL per-formance at all but 125 Hz does not help the average FSTC = 40 rating. Under absorptive room conditions similar comments apply, where the average FSTC = 42. A small increase in the field TL value over the laboratory TL values for the coincidence dip may be noted.

Based on these data, wall D has demonstrated a potential for field FSTC = 40-42. Low frequency test environment effects as shown in figure 8 can improve the FSTC to 43 (duplex D-1A). Typical field potential is ex-pected to give FSTC = 42.

Because the RAL test of wall D gave an STC = 39 which was six points lower than previously published data, a second RAL test was conducted on a wall that was a replicate of wall D, except for the drywall laminating com-pound type. The laminating compound for the original wall was a casein type powder productthat was widely used at the time of testing in 1964. When laminating compound for the pre-sent study was purchased, casein based drywalllaminating products were being phased off the market in favor of noncasein based materials, so that the latter were obtained. A ready-to-use

water base noncasein adhesive was used for walls FPL/RAL D and duplex walls D-1 and D-2. To see if a different laminating compoundwould affect the data for wall D-3 jointcompound-taping powder mix was used. No significant difference was noted.

For the second RAL test, FPL/RAL D2, a third type of noncasein-based drywalllaminating adhesive powder mix was used. The data for this test are compared with FPL/RALD in figure 19 where it may be noted that the low frequency controlled STC = 42 for the sec-ond test is three points higher than the STC = 39 for FPL/RAL D. Inspection of the adhesive distribution on samples taken after testingfrom each of the walls showed that for thesecond RAL wall much less flattening of the adhesive bead (1/4-by 1/4-in. notched trowel) occurred. This lesser flattening is thought to be the prin-cipal reason for the improved decoupling of the gypsum board and therefore, higher STC value. The reason for the difference in the adhesive bead flattening was apparently an adhesive property, based on visual observation of adhesive distribution with various amounts of impacting. This would provide an example of variable performance due to material dif-ferences.

Effectiveness of the STC Rating Sys t em

Included in this report are numerous ex-amples in which the STC rating system of ASTM E 413 (3) would seem overly severe for laboratory tests when compared with field per-formance. One example of this is walls C and D where the STC was eight-point deficiency con-trolled at 125 Hz. This should not be an unusual condition when it is recalled from the section, “Sound Insulation Potential of Single-Row-of-Stud Walls,” that for an acoustically designeddouble leaf wall the low frequency TL increases at a rate of 12 to 18 dB per octave.

When this rate is compared to the initial rise of the rating contour at 9 dB per octave it is evident that 125 Hz laboratory TL values are very likely to be controlling unless the gypsumboard decoupler (wall A) or perimeter connec-tion (fig. 6) reduce the mid and/or high TL fre-quency response, including the coincidence phenomenon. In addition to the likelihood of 125 Hz being controlling for the STC rating, it also is a variable measurement in the laboratory as discussed in reference (10). The duplex D-1A FSTC = 43 was four points higher than the laboratory STC, apparently due to uncertain-ties in the 125 Hz measurement illustrated in figure 8.

22

Figure 18.-Transmission loss vs. frequency for wall D showing duplex data under (A) bare and (B) absorptive room conditions and then comparing the corresponding lab data with the average duplex data under (C) bare and (D) absorptive room conditions. The FSTC rating contour deficiency points are shown in the boxes for (A) and (B) with the total deficiencies at the right. M 142 529

23

Deep coincidence dips provide another ex-ample of eight-point deficiencies being con-trolling as for the previously published data STC = 46 in figure 14B. Under absorptive room conditions typical of many field situations the coincidence dip could be considerablymoderated as shown in figure 8. A good field ex-ample is illustrated by wall B in figure 16D.

When this information is considered alongwith the study by Clark (7) that showed, based on jury listening tests, that the eight-pointdeficiency limitation may be overly stringent

Figure 19 -Transmission loss us. frequency for wall FPL/RAL D, and an RAL test of an FPL-constructed wall that was a replicate of wall D except for a different drywall laminating compound type and application technique. The STC rating contour deficiency points are shown in the boxes with the total deficiencies, *, at the right.

M 142 448

for coincidence dips, consideration of further studies on the ASTM E 413 STC ratingdeficiency point system may be productive. If some easing of the eight-point limitations were allowed, the laboratory STC ratings of walls C and D would be improved several points and the laboratory STC rating of wall B would be less subject to penalty due to a deep coincidence dip at one frequency, giving apparently better lab-field correlations. This may also provide better correspondence to human response.

24

Summary of Data

The conclusions with respect to the specific types of walls tested were:

1. Wall A using resilient channels on both sides of the studs and multiple gypsumboard layers: The laboratory STC = 56 represents a high performance single-row-of-stud wall which would require an acoustically designed bounding structure to realize field values close to the lab-oratory STC. However, a high STC wall such as wall A allows in theory a flankingFSTC as low as 45 to provide a field FSTC = 45.

2. Wall B using single layers of gypsumboard and resilient channels on one side of the studs: The laboratory evaluation gave STC = 47: field evaluations gaveFSTC = 44 and 47 values under bare and absorptive room conditions respectively,including some flanking. Under absorp-tive room conditions. it was estimated that test environment effects could giveFSTC = 49 in the absence of flanking.Mounting the resilient channels on the studs with the predrilled holes alined gaveFSTC values one or two points higher than a random orientation of the predrilledholes.

3. Wall C using 1/4-inch hardboard decouplers for single layers of 518-inch gypsum board on both sides of the studs: A laboratory test of wall C gave an STC = 44. Field tests gave average FSTC values of 42 and 44 under bare and absorptive

room conditions, respectively. Because the FSTC ratings were controlled by eight point deficiencies at 125 Hz there was no duplex flanking effect on the ratingvalues. The construction was sensitive to the technique of assembly with varia-tions in screw insertion resulting in FSTC values as high as 49, under absorptive room conditions. Typical field installations are estimated to have a potential for measured FSTC values similar to the duplex FSTC = 42 to 44.

4. Wall D using 1/2-inch sound deadeningboard decouplers for single layers of 5/8-inch gypsum board: A laboratory test of wall D gave an STC = 39. Field tests gave average FSTC values of 40 and 42 for bare and absorptive room conditions, respectively. Because the FSTC ratings were controlled by eight point deficiences at 125 Hz there was no duplex flankingeffect on the rating values. Typical field installations are estimated to have a potential for measured FSTC values similar to the duplex FSTC = 40 to 42.

A second wall D2 that was constructed and tested at RAL and was a replicate of the first RAL wall D except for a different drywalladhesive gave an STC = 42. The higher value was due, apparently to a property of the adhesive which resulted in less flattening of the 1/4-inch adhesive beads.

Conclusions The conclusions regarding the overall

performance of single-row-of-stud walls where: 1. For STC performance over 50, mul-

tiple lavers of gypsum board and gooddecouplers, such as resilient channels, are required.

2. Single-row-of-stud walls with singledecoupled lavers of gypsum board have STC and FSTC potential up to about 50.

3. The STC and FSTC ratings of the walls are sensitive to the type of decouplerand also the assembly techniques used.

4. For a wall with an STC performanceof 47 a flanking FSTC of 50 is required

to maintain a field FSTC > 45. 5. Test environment effects can, under

certain conditions of test and wall design,give field FSTC values two to four pointshigher than laboratory STC values. The conclusion regarding the STC rating

svstem is: 1. Because of uncertainties in test data

at 125 Hz and field test environment effects. improved correlation between laboratory and field tests might be possible if the eight point maximum defici-ency points requirement was eased.

25

Literature Cited

1. Acoustical and Insulating Materials Association 1967. Noise control with insulation board for homes, apartments, motels,

and offices. Test IBI-33FT, p. 22. AIMA, 205 W. Touhy Ave., Park Ridge, Ill.

2. American Hardboard Association 1970. Hardboard partitions for sound control. Test TL 65-164, p. 7. AHA,

20 N. Wacker Dr., Chicago, Ill.

3. American Society for Testing and Materials. 1970. Determination of sound transmission class. ASTM Designation E

413-70T. ASTM, 1916 Race St., Philadelphia, Pa.

4. 1970. Laboratory measurement of airborne sound transmission loss of

building partitions. ASTM Designation E 90-70. ASTM, 1916 Race St., Philadelphia, Pa.

5. 1971. Fire tests of building construction and materials. ASTM Designation

E 119-71. ASTM, 1916 Race St., Philadelphia, Pa.

6. 1971. Measurement of airborne sound insulation in buildings. ASTM

Designation E 336-71. ASTM, 1916 Race St., Philadelphia, Pa.

7. Berendt, R.D., Winzer, G.E., and Burroughs, C.B. 1967. Airborne. impact and structure borne noise control in multi-family

dwellings. U.S. Dept. of Housing and Urban Development reportavailable from Sup. of Doc., U.S. Gov. Printing Office, Washington, D.C.

8. Clark, D.M. 1970. Subjective study of the sound-transmission class system for rating

building partitions. (Part 1) J. Acoust. Soc. of Amer. 47(3):676-682.

9. Cook, Richard K., and Chrzanowski, Peter 1957. Transmission of noise through walls and floors. In Handbook of

Noise Control (C.M. Harris, ed.) McGraw-Hill Book Co., New York, N.Y.

10. Jones, Robert E. 1974. Lab-field correlations for airborne sound transmission through

party walls. USDA Forest Serv. Res. Pap. FPL 240. Forest Prod. Lab., Madison, Wis.

11. Northwood, T.D. 1964. Sound insulation and the apartment dweller. J. Acoust. SOC. of

Amer. 36(4): 725-728.

26

12. Owens Corning Fiberglass 1969. Solutions to noise control problems. Construction W-W3. Owens

Corning Fiberglass Corp., Fiberglass Tower, Toledo, Ohio.

13. Prestemon, Dean R. 1968. Least-cost wall and floor constructions for limiting transmission of

noise. Spec. Rep. No. 55, p. 15. Agr. and Home Econ. Exp. Sta., Iowa State Univ. of Sci. and Tech., Ames, Iowa.

14. Sharp, Ben H. 1973. A study of techniques to increase the sound insulation of building

elements. HUD contract H-1095. Clearinghouse for Fed. Sci. and Tech. Inform., Springfield. Va.

15. U.S. Department of Housing and Urban Development, Washington, D.C. 1972. Minimum property standards for multifamily housing, Vol 2, No.

EIS-AA-72-5667-D-2, p. 72. Nat. Tech. Inform. Serv., U.S. Dep. of Corn.. Springfield, Va.

16. United States Gypsum1971. Drywall construction handbook. Test data/sound tests USG-33-FT-

G & H, p. 252. U.S. Gypsum, 101 S. Wacker Dr., Chicago, Ill.

17. Ver, I.L.. and Holmer, C.I. 1971. Interaction of sound waves with solid structures. In Noise and

Vibration Control (L.L. Beranek, ed.). McGraw-Hill Book Co., New York, N.Y.

18. Young. Robert W. 1965. Re-vision of the speech-privacy calculation. J. Acoust. Soc. of

Amer. 38(4): 524-530.

APPENDIX I Test Wall

Assembly Details

The four test walls for this study had the following fastener schedule and adhesive application assembly details in common, except as noted. For the framing the sole plate and lower top plate were attached to the studs with two twelvepennv nails driven through the platesinto each end of the stud. For the lab tests, the upper top plate was fastened to the lower topplate with twelvepennv nails. 16 inches on center. The test partition was anchored to the bottom and sides of the Riverbank Acoustical Laboratory test frame on about 32-inch centers and to the top on 64-inch centers. For the duplex test cavity the upper top plate of the original duplex wall was left in place. The wood framing was tilted into the test cavity and the lower top plate screwed to the upper top plate

on 32-inch centers. The base plate was fastened to the subfloor with twelvepenny nails, 16 in-ches on center.

One piece of kraft backed glass fiber insula-tion. 1.5 by 96 by 2-1/4 inches thick, was hung in each stud cavity using 1/4-inch staples 24 inches on center to fasten the paper mounting flange to the inside surface of the stud.

The unique factors for each wall are as follows:

Wall A Resilient channels (manufactured length =

12 ft) and 1/2-inch gypsum board base filler strips were applied horizontally to both sides of the test partition (fig. 9A). The channels were oriented so that the stud attachment flange was

27

below the gypsum board attachment face. They were located at 2, 4, and 6 feet and 7 feet, 8 in-ches from the test cavity base. The resilient channels were adjusted horizontally until the predrilled holes lined up with the studs and one 1-1/4-inch drywall screw driven with a drywall screw gun at each intersection of the channel with a stud. Where splices were made in the channels, a 6-inch overlap was used. A 3-by 1/2-inch gypsum board base filler strip was at-tached to the base of the stud framing with 1-1/4-inch drywall screws, 16 inches on center.

Two layers of 1/2- by 48- by 96-inch gypsumboard were applied vertically and screw at-tached to the resilient channels and filler strip on one side of the partition while three layers of the same type of gypsum board were attached on the other side, as shown in figure 9A. Each gyp-sum board layer was offset 16 inches with respect to the layer below it. The partitionperimeter of each layer of the gypsum board had 1/4- to 1/2-inch relief to permit calking.

For the two layer side, the first layer was attached with 1-inch drywall screws 24 inches on center into the channel and 1-7/8-inch drywall screws 24 inches on center into the filler strip. The second and top layer was attached with 1-1/4-inch drywall screws 12 inches on center along the channels, and 1-7/8-inch drywall screws, 12 inches on center along the filler strip.

For the three layer side. the first layer was attached with 1-inch drywall screws 24 inches on center into the channel and 1-7/8-inch drywall screws 24 inches on center into the filler strip. The second layer was attached with 1-1/4-inch drywall screws 24 inches on center for the filler strip. The third and outermost layer was attached with 1-7/8-inch drywall screws 12 in-ches on center along the channels and tenpennycoated nails, 12 inches on center over the filler strip.

All screws were driven and dimpled into the gypsum board approximately 1/32 inch with a drywall screwgun. When difficulty in piercingthe channel was experienced, a longer screw was used. and care was taken to place the screw between the studs. The gypsum board butt joints for each layer were treated with the 90-minute drying time filler compound. For wall A, the additional treatment of the joints or edgeswith joint compound and tape was omitted.

Wall B Resilient channels and 1/2-inch gypsum

board base filler strips were applied horizontal-ly to one side of the test partition (fig. 9B) the same as for wall A. A single layer of 5/8- by 48-by 96-inch type X fire rated gypsum board was

U.S. GOVERNMENT PRINTING OFFICE 1974-650-252/21

applied vertically to both sides of the partitionand screw attached. The partition perimeter of the gypsum board had 1/4- to 1/2-inch relief to permit calking. For the resilient channels side, 1-inch drywall screws. 12 inches on center, were used. Over the filler strip 1-7/8-inch drywall screws, 12 inches on center, were used. On the other side of the partition, the gypsum board was screw attached directly to the studs with 1-1/4-inch drywall screws. 16 inches on center in the gypsum board field and perimeter. All screws were driven and dimpled into the gyp-sum board approximately 1/32 inch with a drywall screw gun.

Wall C A single layer of 1/4- by 48- by 96-inch

standard hardboard paneling was applied(screen side to studs) vertically to the studs on both sides of the partition (fig. 9C) using a Neo-prene base contact adhesive. Vertical joints were staggered on opposite sides. The partitionperimeter of the hardboard paneling had 1/4- to 1/2-inch relief to permit calking after the gyp-sum board had been applied. The adhesive was applied with a calking gun to the studs in 1/8- to 1/4-inch diameter straight continuous beads, one bead per stud (centered) in panel field and along top and bottom plates, two beads per stud at vertical panel joints (approximately 5-1/2fluid ounces per hardboard panel). The adhesive was applied for one panel at a time. The hardboard was positioned against the studs by using a temporary 1/2-inch block at the base for vertical spacing and by placing a fourpennyfinishing nail at each of the upper corners. The hardboard was then impacted along the adhesive lines by hand or block and hammer to squash the adhesive beads and wet the hard-board surface. The bottom of the board was then swung away from the base plate about 8 in-ches. using the top nails as hinges. The adhesive was allowed to flash for about 2 minutes and the hardboard impacted into the studs again.

A single laver of 5/8- by 48- by 96-inch typeX fire rated gypsum board was adhesivelyapplied vertically to the sound deadening board sides of the partition with vertical joints offset 8 inches with respect to the studs and staggered on opposite sides. The partition perimeter of the gypsurn board had a 1/4- to 1/2-inch relief to permit calking. The Neoprene base contact panel adhesive was applied to the hardboard surface between the studs in 1/8- to 1/4-inch diameter continuous straight beads with a single bead corresponding to the gypsum board panel field and also along the panel perimeter,approximately 2 inches from the edge. The gyp-sum board panel was alined vertically with a

28 2.5-29-10-74

temporary 1/2-inch spacer block at the base and was impacted with block and hammer along the adhesive lines. Supplemental attachment was obtained using 1-5/8-inch drywall screws 24 in-ches on center along the studs in the field and vertical joints, and 16 inches on center along the top and sole plates. The screws were driven and dimpled approximately 1/32 inch into the gyp-sum board with a drywall screw gun.

Wall D A single layer of 1/2-by 48- by 96-inch wood

fiber sound-deadening board was applied ver-tically to the studs on both sides of the partition(fig. 9D) using fivepenny coated nails 12 inches on center in the field and perimeter. The nail heads were well dimpled with a hammer. Ver-tical joints were staggered on opposite sides. The partition perimeter of the sound deadeningboard had 1/4- to 1/2-inch relief at the wall perimeter to permit calking after the gypsumboard was applied. The board was positionedagainst the studs by using a temporary 112-inch block at the base for vertical spacing. A gap of up to 1/8 inch was permitted for sound deaden-ing board joints over the studs.

A single layer of 5/8- by 48- by 96-inch typeX fire rated gypsum board was adhesivelyapplied vertically to the sound deadening board on both sides of the partition. On each side, the vertical joints were offset 16 inches with respect to the sound deadening board joints. The parti-tion perimeter of the gypsum board had 1/4- to 1/2-inch relief to permit calking. The gypsumboard was supported horizontally while a water base drywall adhesive was applied to it with a notched trowel. The trowel contained four notches, 1/4 by 1/4 inch, 2 inches on center. The 6-inch-wide strips of adhesive were appliedalong the vertical centerline and 2 inches from the edges and ends. The gypsum board panel was alined vertically with a temporary 1/2-inch spacer block at the base and was impacted byhand or with block and hammer along the adhesive lines. Supplemental attachment was obtained using 1-7/8-inch drywall screws 24 in-ches on center along the studs in the field and vertical joints and 16 inches on center along the top and sole plates. The screws were driven and dimpled approximately 1/32 inch into the gyp-sum board with a drywall screw gun.