Absorption coefficients of common building materials and finishes

What is an absorption coefficient? It’s the fraction of incident sound energy absorbed by a surface at a given frequency. Values range from 0.00 (highly reflective) to 1.00 (highly absorptive). Use the tables below to select suitable finishes and to estimate room treatment needs across octave bands.

How to use: identify the dominant problem frequencies (speech clarity → 1–4 kHz, low-frequency rumble → 125–250 Hz). Choose materials with higher α (alpha) at those bands. Combine materials and consider coverage (m²) to achieve your target reverberation time.

Note: Laboratory values vary with installation method, mounting and manufacturer. Treat this as guidance and confirm with product data sheets where possible.

Floor materials

Absorption coefficients (α) by octave band
Floor materials	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	0.10
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	0.10	0.07	0.06	0.07

Explore JCW’s floor soundproofing products for improved absorption and impact isolation.

Seating materials

Absorption coefficients (α) by octave band
Seating materials	125 Hz	250 Hz	500 Hz	1 kHz	2 kHz	4 kHz
Benches (wooden, empty)	0.10	0.09	0.08	0.08	0.08	0.08
Benches (wooden, 2/3 occupied)	0.37	0.40	0.47	0.53	0.56	0.53
Benches (wooden, fully occupied)	0.50	0.56	0.66	0.76	0.80	0.76
Benches (cushioned seats & backs, empty)	0.32	0.40	0.42	0.44	0.43	0.48
Benches (cushioned seats & backs, 2/3 occupied)	0.44	0.56	0.65	0.72	0.72	0.67
Benches (cushioned seats & backs, fully occupied)	0.50	0.64	0.76	0.86	0.86	0.76
Theatre seats (wood, empty)	0.03	0.04	0.05	0.07	0.08	0.08
Theatre seats (wood, 2/3 occupied)	0.34	0.21	0.28	0.53	0.56	0.53
Theatre seats (wood, fully occupied)	0.50	0.30	0.40	0.76	0.80	0.76
Seats (fabric-upholstered, empty)	0.49	0.66	0.80	0.88	0.82	0.70
Seats (fabric-upholstered, fully occupied)	0.60	0.74	0.88	0.96	0.93	0.85

See our cinema & theatre room solutions for seating/room package options.

Reflective wall materials

Absorption coefficients (α) by octave band
Reflective wall materials	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)	0.10	0.05	0.06	0.07	0.09	0.08
Concrete (poured, rough, unpainted)	0.01	0.02	0.04	0.06	0.08	0.10
Doors (solid wood panels)	0.10	0.07	0.05	0.04	0.04	0.04
Glass (6 mm 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 on studs)	0.29	0.10	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	0.10	0.06	0.05	0.04	0.04
Plywood (3 mm over 32 mm airspace)	0.15	0.25	0.12	0.08	0.08	0.08
Plywood (3 mm over 57 mm airspace)	0.28	0.20	0.10	0.10	0.08	0.08
Plywood (5 mm over 50 mm airspace)	0.38	0.24	0.17	0.10	0.08	0.05
Plywood (5 mm + 25 mm fiberglass in 50 mm airspace)	0.42	0.36	0.19	0.10	0.08	0.05
Plywood (6 mm, airspace, light bracing)	0.30	0.25	0.15	0.10	0.10	0.10
Plywood (10 mm, airspace, light bracing)	0.28	0.22	0.17	0.09	0.10	0.11
Plywood (19 mm, airspace, light bracing)	0.20	0.18	0.15	0.12	0.10	0.10

Absorptive wall materials

Absorption coefficients (α) by octave band
Absorptive wall materials	125 Hz	250 Hz	500 Hz	1 kHz	2 kHz	4 kHz
Drapery (10 oz/yd², flat)	0.04	0.05	0.11	0.18	0.30	0.35
Drapery (14 oz/yd², flat)	0.05	0.07	0.13	0.22	0.32	0.35
Drapery (18 oz/yd², flat)	0.05	0.12	0.35	0.48	0.38	0.36
Drapery (14 oz/yd², pleated 50%)	0.07	0.31	0.49	0.75	0.70	0.60
Drapery (18 oz/yd², pleated 50%)	0.14	0.35	0.53	0.75	0.70	0.60
Fiberglass board (25 mm)	0.06	0.20	0.65	0.90	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 (100 mm)	0.99	0.99	0.99	0.99	0.99	0.97
Open brick pattern over 75 mm fiberglass	0.40	0.65	0.85	0.75	0.65	0.60
Pegboard over 25 mm fiberglass	0.08	0.32	0.99	0.76	0.34	0.12
Pegboard over 50 mm fiberglass	0.26	0.97	0.99	0.66	0.34	0.14
Pegboard over 75 mm fiberglass	0.49	0.99	0.99	0.69	0.37	0.15
Perforated metal (13% open) over 50 mm fiberglass	0.25	0.64	0.99	0.97	0.88	0.92

See our wall soundproofing products & solutions.

Ceiling materials

Absorption coefficients (α) by octave band
Ceiling materials	125 Hz	250 Hz	500 Hz	1 kHz	2 kHz	4 kHz
Plasterboard (12 mm in suspended 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	0.90	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, 75 mm batts)	0.73	0.99	0.99	0.89	0.52	0.31
Plaster (gypsum or lime, on masonry)	0.01	0.02	0.02	0.03	0.04	0.05
Plaster (gypsum or lime, rough finish or timber lath)	0.14	0.10	0.06	0.05	0.04	0.04
Sprayed cellulose fibre (16 mm on solid backing)	0.05	0.16	0.44	0.79	0.90	0.91
Sprayed cellulose fibre (25 mm on solid backing)	0.08	0.29	0.75	0.98	0.93	0.76
Sprayed cellulose fibre (25 mm on timber lath)	0.47	0.90	1.10	1.03	1.05	1.03
Sprayed cellulose fibre (32 mm on solid backing)	0.10	0.30	0.73	0.92	0.98	0.98
Sprayed cellulose fibre (75 mm on solid backing)	0.70	0.95	1.00	0.85	0.85	0.90
Wood tongue-and-groove roof decking	0.24	0.19	0.14	0.08	0.13	0.10

See our ceiling soundproofing products & solutions.

Miscellaneous surfaces

Absorption coefficients (α) by octave band
Miscellaneous surface material	125 Hz	250 Hz	500 Hz	1 kHz	2 kHz	4 kHz
People – adults (per 0.1 person)	0.25	0.35	0.42	0.46	0.50	0.50
People – high school students (per 0.1 person)	0.22	0.30	0.38	0.42	0.45	0.45
People – elementary students (per 0.1 person)	0.18	0.23	0.28	0.32	0.35	0.35
Ventilating grilles	0.30	0.40	0.50	0.50	0.50	0.40
Water or ice surface	0.008	0.008	0.013	0.015	0.020	0.025

Need help choosing materials?

Tell us about your room and target use (office, classroom, studio). We’ll recommend a package of acoustic wall panels, mass-adding boards and floor treatments to hit your acoustic goals.

Contact the JCW team for expert advice.