Table shows sound absorption coefficient for different building materials.

Beta version#

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Floor materials#

Material	125 Hz	250 Hz	500 Hz	1 kHz	2 kHz	4 kHz
Carpet	0.01	0.02	0.06	0.15	0.25	0.45
Concrete (unpainted, rough finish)	0.01	0.02	0.04	0.06	0.08	0.1
Concrete (sealed or painted)	0.01	0.01	0.02	0.02	0.02	0.02
Marble or glazed tile	0.01	0.01	0.01	0.01	0.02	0.02
Vinyl tile or linoleum on concrete	0.02	0.03	0.03	0.03	0.03	0.02
Wood parquet on concrete	0.04	0.04	0.07	0.06	0.06	0.07
Wood flooring on joists	0.15	0.11	0.1	0.07	0.06	0.07

Seating Materials#

Material	125 Hz	250 Hz	500 Hz	1 kHz	2 kHz	4 kHz
Benches (wooden, empty)	0.1	0.09	0.08	0.08	0.08	0.08
Benches (wooden, 2/3 occupied)	0.37	0.4	0.47	0.53	0.56	0.53
Benches (wooden, fully occupied)	0.5	0.56	0.66	0.76	0.8	0.76
Benches (cushioned seats and backs, empty)	0.32	0.4	0.42	0.44	0.43	0.48
Benches (cushioned seats and backs, 2/3 occupied)	0.44	0.56	0.65	0.72	0.72	0.67
Benches (cushioned seats and backs, fully occupied)	0.5	0.64	0.76	0.86	0.86	0.76
Theater seats (wood, empty)	0.03	0.04	0.05	0.07	0.08	0.08
Theater seats (wood, 2/3 occupied)	0.34	0.21	0.28	0.53	0.56	0.53
Theater seats (wood, fully occupied)	0.5	0.3	0.4	0.76	0.8	0.76
Seats (fabric-upholsterd, empty)	0.49	0.66	0.8	0.88	0.82	0.7
Seats (fabric-upholsterd, fully occupied)	0.6	0.74	0.88	0.96	0.93	0.85

Reflective wall materials#

Material	125 Hz	250 Hz	500 Hz	1 kHz	2 kHz	4 kHz
Brick (natural)	0.03	0.03	0.03	0.04	0.05	0.07
Brick (painted)	0.01	0.01	0.02	0.02	0.02	0.03
Concrete block (coarse)	0.36	0.44	0.31	0.29	0.39	0.25
Concrete block (painted)	0.1	0.05	0.06	0.07	0.09	0.08
Concrete (poured, rough finish, unpainted)	0.01	0.02	0.04	0.06	0.08	0.1
Doors (solid wood panels)	0.1	0.07	0.05	0.04	0.04	0.04
Glass (1/4 inch plate, large pane)	0.18	0.06	0.04	0.03	0.02	0.02
Glass (small pane)	0.04	0.04	0.03	0.03	0.02	0.02
Plasterboard (12 mm paneling on studs)	0.29	0.1	0.06	0.05	0.04	0.04
Plaster (gypsum or lime, on masonry)	0.01	0.02	0.02	0.03	0.04	0.05
Plaster (gypsum or lime, on wood lath)	0.14	0.1	0.06	0.05	0.04	0.04
Plywood (3mm paneling over 31.7 mm airspace)	0.15	0.25	0.12	0.08	0.08	0.08
Plywood (3mm paneling over 57.1mm airspace)	0.28	0.2	0.1	0.1	0.08	0.08
Plywood (5mm paneling over 50mm airspace)	0.38	0.24	0.17	0.1	0.08	0.05
Plywood (5mm panel, 25mm fiberglass in 50mm airspace)	0.42	0.36	0.19	0.1	0.08	0.05
Plywood (6mm paneling, airspace, light bracing)	0.3	0.25	0.15	0.1	0.1	0.1
Plywood (10mm paneling, airspace, light bracing)	0.28	0.22	0.17	0.09	0.1	0.11
Plywood (19mm paneling, airspace, light bracing)	0.2	0.18	0.15	0.12	0.1	0.1

Absorptive wall materials#

Material	125 Hz	250 Hz	500 Hz	1 kHz	2 kHz	4 kHz
Drapery (10 oz/yd2, 340 g/m², flat against wall)	0.04	0.05	0.11	0.18	0.3	0.35
Drapery (14 oz/yd2, 476 g/m², flat against wall)	0.05	0.07	0.13	0.22	0.32	0.35
Drapery (18 oz/yd2, 612 g/m², flat against wall)	0.05	0.12	0.35	0.48	0.38	0.36
Drapery (14 oz/yd2, 476 g/m², pleated 50%)	0.07	0.31	0.49	0.75	0.7	0.6
Drapery (18 oz/yd2, 612 g/m², pleated 50%)	0.14	0.35	0.53	0.75	0.7	0.6
Fiberglass board (25mm)	0.06	0.2	0.65	0.9	0.95	0.98
Fiberglass board (50 mm)	0.18	0.76	0.99	0.99	0.99	0.99
Fiberglass board (75 mm)	0.53	0.99	0.99	0.99	0.99	0.99
Fiberglass board (100mm)	0.99	0.99	0.99	0.99	0.99	0.97
Open brick pattern over 75 mm fiberglass	0.4	0.65	0.85	0.75	0.65	0.6
Pageboard over 25 mm fiberglass board	0.08	0.32	0.99	0.76	0.34	0.12
Pageboard over 50mm fiberglass board	0.26	0.97	0.99	0.66	0.34	0.14
Pageboard over 75mm fiberglass board	0.49	0.99	0.99	0.69	0.37	0.15
Performated metal (13% open, over 50mm fiberglass)	0.25	0.64	0.99	0.97	0.88	0.92

Ceiling Material#

Material	125 Hz	250 Hz	500 Hz	1 kHz	2 kHz	4 kHz
Plasterboard (12mm in suspended ceiling grid)	0.15	0.11	0.04	0.04	0.07	0.08
Underlay in perforated metal panels (25 mm batts)	0.51	0.78	0.57	0.77	0.9	0.79
Metal deck (perforated channels, 25 mm batts)	0.19	0.69	0.99	0.88	0.52	0.27
Metal deck (perforated channels, 75mm batts)	0.73	0.99	0.99	0.89	0.52	0.31
Plaster (gypsum or lime, on masonary)	0.01	0.02	0.02	0.03	0.04	0.05
Plaster (gypsum or lime, rough finish or timber lath)	0.14	0.1	0.06	0.05	0.04	0.04
Sprayed cellulose fiber (16 mm on solid backing)	0.05	0.16	0.44	0.79	0.9	0.91
Sprayed cellulose fiber (25mm on solid backing)	0.08	0.29	0.75	0.98	0.93	0.76
Sprayed cellulose fiber (25mm on timber lath)	0.47	0.9	1.1	1.03	1.05	1.03
Sprayed cellulose fiber (32mm on solid backing)	0.1	0.3	0.73	0.92	0.98	0.98
Sprayed cellulose fiber (75mm on solid backing)	0.7	0.95	1	0.85	0.85	0.9
Wood tongue-and-groove roof decking	0.24	0.19	0.14	0.08	0.13	0.1

Miscellaneous surface material#

Material	125 Hz	250 Hz	500 Hz	1 kHz	2 kHz	4 kHz
People-adults (per 1/10 person)	0.25	0.35	0.42	0.46	0.5	0.5
People-high school students (per 1/10 person)	0.22	0.3	0.38	0.42	0.45	0.45
People-elementary students (per 1/10 person)	0.18	0.23	0.28	0.32	0.35	0.35
Ventilating grilles	0.3	0.4	0.5	0.5	0.5	0.4
Water or ice surface	0.008	0.008	0.013	0.015	0.02	0.025

Some facts#

When a sound wave moves through the air meets a barrier, part of the acoustic energy is reflected, part is absorbed inside the wall (converted to heat), and the another part is transmited out (on the other side of the wall). We can write it mathematically as follows:

$\alpha + \beta + \tau = 1$
where:
- $\alpha$ - absorption coefficient (determines the part of the energy that was absorbed inside the wall),
- $\beta$ - reflection coefficient (defines the part of the energy remaining in the first room),
- $\tau$ - transmission coefficient (defines the part of the energy that was emitted to the second room).
The absorption coefficient determines what part of the acoustic energy was absorbed by the encountered barrier:

$\alpha = \frac{E_{abs.}}{E_{inc.}}$
where:
- $E_{abs.}$ - energy of the absorbed wave,
- $E_ {inc.}$ - energy of the incident wave.
The absorption coefficient equal to one (α = 1) means that all energy has been absorbed .
The absorption coefficient equal to zero (α = 0) means that all energy has been reflected or passed through the barrier .
The ability of bodies to absorb sound energy is used during acoustic adaptation of rooms. Sound-absorbing materials can be used to reduce the reverberation of a room to the desired level or reduce resonant frequencies.