Acousta-Wal Sound Absorption Coefficients

Complete tables of coefficients of the various materials that normally constitute the interior finish of rooms may be found in the various books on architectural acoustics. The following short list will be useful in making simple calculations of the reverberation in rooms.

Materials	Coefficients
	125cps.	250cps.	500cps.	1000cps.	2000cps.	4000cps.
Brick, unglazed	.03	.03	.03	.04	.05	.07
Brick, unglazed, painted	.01	.01	.02	.02	.02	.03
Carpet
heavy, on concrete	.02	.06	.14	.37	.60	.65
Same, on 40 oz. hairfelt or foam rubber	.08	.24	.57	.69	.71	.73
Same, with impermeable latex backing on 40 oz. hairfelt or foam rubber	.08	.27	.39	.34	.48	.63
Concrete block, coarse	.36	.44	.31	.29	.39	.25
Concrete block, painted	.10	.05	.06	.07	.09	.08
Fabrics
Light velour, 10 oz. per sq. yd., hung straight, in contact with wall	.03	.04	.11	.17	.24	.35
Medium velour, 10 oz. per sq. yd., draped to half area	.07	.31	.49	.75	.70	.60
Heavy velour, 18 oz. per sq. yd., draped to half area	.14	.35	.55	.72	.70	.65
Floors
Concrete or terrazzo	.01	.01	.015	.02	.02	.02
Linoleum, asphalt, rubber or cork tile on concrete	.02	‘.03	.03	.03	.03	.02
Wood	.15	.11	.10	.07	.06	.07
Wood parquet in asphalt on concrete	.04	.04	.07	.06	.06	.07
Glass
Large panes of heavy plate glass	.18	.06	.04	.03	.02	.02
Ordinary window glass	.35	.25	.18	.12	.07	.04
Gypsum board
1/2″ nailed to 2 x 4″s 16″ o.c.	.29	.10	.05	.04	.07	.09
Marble or glazed tile	.01	.01	.01	.01	.02	.02
Openings
Stage, depending on furnishings	.25 – .75
Deep balcony, upholstered seats	.50 – 1.00
Grills, ventilating	.15 – .50
Plaster, gypsum or lime, smooth finish
on tile or brick	.013	.015	.02	.03	.04	.05
Plaster, gypsum or lime, rough finish
on lath	.02	.03	.04	.05	.04	.03
Same, with smooth finish	.02	.02	.03	.04	.04	.03
Plywood paneling
3/8″ thick	.28	.22	.17	.09	.10	.11
Water surface
as in a swimming pool	.008	.008	.013	.015	.020	.025
Air
sabins per 1000 cubic feet					2.3	7.2

SOUND TRANSMISSION CLASS

Approximate Sound Transmission Class (STC) ratings for Acousta-Wal units as compared to ratings for other units are shown below.

Acousta-Wal Masonry Units		Regular Lightweight CMU
4″	49
6″	52	6″	43
8″	56	8″	46
12″	62	12″	51

A 12″ Type I RF Acousta-Wal unit will absorb 62 decibels of sound (laid facing the origin of the sound).

Therefore, if there is a sound of 105 decibels reaching the wall, 62 decibels will be absorbed by the wall and 43 decibels will go through the wall to the other side.

Typical Sound Levels (in Decibels)
Threshold of audibility	0
Rustle of leaves in gentle breeze	10
Average whisper 4 feet away	20
Soft radio in apartment; average residence	35
Average office	45
Moderate restaurant background	50
Noisy office or department store	55
Average busy street	60
Stenographic room	70
City subway	80
Loud automobile horn 23 feet away	100
Express train passing at high speed	105
Threshold of feeling (varies with frequency)	120
Threshold of painful sounds; limit of ear’s endurance	130
Near jet engine	160