Sound transmission loss of masonry walls: twelve-inch lightweight concrete blocks, comparison of latex and plaster sealers

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Sound transmission loss of masonry walls: twelve-inch lightweight

concrete blocks, comparison of latex and plaster sealers

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ANALYZED

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I

SOUND TRANSMISSION LOSS

OF

Twelve -Inch Lightweight Concrete Blocks

Comparison of Latex and Plaster Sealers

by

SOUND TRANSMISSION LUSS

O F

Twelve -Inch Lightweight Concrete Blocks - Comparison of Latex a n d Plaster Sealers

T . D . Nar+thwood and D. W. Monk

This i s the second of a proposed s e r i e s of notes reporting

laboratory measurements of sound transmission l o s s of masonry w a l l s .

The t e s t pro g r a m , w h i c h will extend o v e r several y e a r s , w i l l eventually

include a range of block t h i c k n e s s e s and d e n s i t i e s , and w i l l examine t h e effects of various additional layers and surface f i n i s h e s . T h e f i r s t note

(Building R e s e a r c h N o t e No. 90) reported six t e s t s on a basic 12-inch lightweight block w a l l w i t h various surface finishes. The present note reports t h r e e _{additional t e s t s on the same type of 12 -inch block wall.}

DESCRIPTION O F

TEST

A wall 1 0 _{f t long x 8 ft high} was built i n a N R C sample mounting rack using nominal 12 -in. thick lightweight concrete blocks. The w a l l consisted of t w e l v e r o w s of b l o c k s l a i d up in a Type N mortar with

mortar joints 318 in. thick tooled to a concave f i n i s h on b t h s i d e s of t h e wall.

Each block w a s 7 -5 J 8 in. high x 15 -518 i n . long x 11-518 in. thick

w i t h i n s e t s o n e a c h e n d . The blocks c o n t a i n e d t h r e e c o r e s of which the two o u t e r cores were 8-112 in. l o n g x 2 - 5 1 8 in. w i d e , t h e centre core

was 8 in, long x 2 - 5 1 8 in. wide and t h e w a l l s between the cores 1-114 in. thick. The outer walls of t h e blocks w e r e 1-5/8 in. thick. All the

measurements w e r e the minimum dimensions measured on the section

w i t h the least amount of bearing s u r f a c e . The average weight of each block was approximately 4 3 lb,

Test 2A - The wall was plastered initially on the source r o o m s i d e with a base coat of s a n d plaa tar approximately 112 in. thick and a f i n i s h c o a t

1/16

consisted of t h r e e parts finishing lime to one part gouging plaster. The r e c e i v i n g room s i d e was left unsealed. Weight per s q f t of the wall was

T e s t 2B - O n the r e c e i v i n g room s i d e t h e wall of T e s t 2A was sealed w i t h latex base block f i l l e r . Three coats w e r e applied to the s u r f a c e allowing approximately one b u r d r y i n g time between c o a t s . _{The filler w a s}

applied by b r u s h and a d e e p p i l e paint r o l l e r , A f t e r completing t h e f i n a l

coat the wall was allowed to d r y for approximately sixteen hours before

conducting a t e s t . W e i g h t per s q f t of the w a l l w a s 56 lb.

Test 2G - T h e latex block sealer w a s removed from the receiving room

s i d e by sand b l a s t i n g and t h e n this s i d e w a s plastered similarly t o the

source room s i d e . The weight per sq f t of the w a l l w a s 59 lb. A photo graph

of the sand blasted surface p r i o r to plastering is shuwn in Figure 2 .

TEST

P R O

Each t e s t was d o n e in accordance with

ASTM

E9O

The results of the three t e s t s a r e g i v e n in Table 1.

COMbrlENTS

ON

The results indicate that once one s i d e o f t h e w a l l is sealed w i t h

plaster t h e r e is little to be gained from t h e v i e w p o i n t of sound insulation by s e a l i n g t h e second side w i t h either block sealer or p l a s t e r . The

a d d i t i o n a l plaster layer makes a very s l i g h t improvement at the l o w e s t

test frequencies because of t h e increased m a s s , b u t o t h e r w i s e the results a r e almost indistinguishable as indicated in Figure 3. I t wiI1 be noted by reference te BRN No. 9 0 ( W a l l l B ) that sealing t h e w a l l with a layer of

plaster also results in a negligible improvement as compared to sealing

w i t h t h r e e c o a t s of latex block filler.

ACKNOWLEDGEMENT

The t e s t s reported here w e r e done as a cooperative project w i t h t h e N a t i o n a l Concrete P r o d u c e r s ' Association, who furnished the materials and constructed t h e test specimens.

TABLE I

SOUND TRANSMISSION LOSS

O F

IN

W a l l No

.

Centre Band

Frequency, Hz. - - 2A

_-

Figure 1 _{Photograph of block section showing}

plaster l a y e r .

Figure 2 Photograph showing wall surface after sand blasting to r e m o v e latex sealer

0

SOURCE ROOM RECEIVING ROOM

LATEX SEALER w O O a m O C 3 Q o O O C S O d O a N 5 0 O L n - O O m O O V ) O Q C 1 V ) o - C ~ m m - ~ s d a o ~ . a a v - o -'-CUCUm*

Centre

F r e q u e n c y

of

T h i r d - O c t a v e

B a n d ,

H z .

F I G U R E

3