Sound Absorption Coefficient Database

Octave-band absorption coefficients (α) and NRC for 60 common materials and treatments. Every value is sourced. Free to download and reuse (CC BY 4.0).

Material	Category	125	250	500	1k	2k	4k	NRC
Concrete block, painted	Hard surfaces	0.10	0.05	0.06	0.07	0.09	0.08	0.05
Concrete block, unpainted	Hard surfaces	0.36	0.44	0.31	0.29	0.39	0.25	0.35
Brick, unglazed	Hard surfaces	0.03	0.03	0.03	0.04	0.05	0.07	0.05
Plaster on masonry	Hard surfaces	0.01	0.01	0.02	0.03	0.04	0.05	0.05
Gypsum board (12 mm on studs) Resonant absorption near 125 Hz from the cavity.	Hard surfaces	0.29	0.10	0.05	0.04	0.07	0.09	0.05
Marble or glazed tile	Hard surfaces	0.01	0.01	0.01	0.01	0.02	0.02	0.00
Cork tiles, 25 mm, on solid backing Cork is a poor absorber; useful for floors and pinboards, not treatment.	Hard surfaces	0.02	0.02	0.03	0.04	0.04	0.05	0.05
Concrete or terrazzo floor	Floors	0.01	0.01	0.01	0.02	0.02	0.02	0.00
Vinyl / linoleum on concrete	Floors	0.02	0.03	0.03	0.03	0.03	0.02	0.05
Wood floor on joists	Floors	0.15	0.11	0.10	0.07	0.06	0.07	0.10
Parquet on concrete	Floors	0.04	0.04	0.07	0.06	0.06	0.07	0.05
Carpet, thin, on concrete	Floors	0.02	0.06	0.14	0.37	0.60	0.65	0.30
Carpet, medium, on felt underlay	Floors	0.05	0.15	0.35	0.55	0.65	0.70	0.45
Carpet, heavy, on foam pad	Floors	0.08	0.24	0.57	0.69	0.71	0.73	0.55
Area rug, medium pile, on hard floor A loose rug covers only part of the floor — scale by the area it actually covers.	Floors	0.04	0.08	0.20	0.45	0.60	0.65	0.35
Rubber / PVC sports floor tile	Floors	0.02	0.03	0.04	0.04	0.04	0.04	0.05
Ordinary window glass	Glass & wood	0.35	0.25	0.18	0.12	0.07	0.04	0.15
Heavy plate glass	Glass & wood	0.18	0.06	0.04	0.03	0.02	0.02	0.05
Plywood panel (10 mm, air gap) Panel resonator — useful low-mid absorption.	Glass & wood	0.28	0.22	0.17	0.09	0.10	0.11	0.15
Wood paneling on battens	Glass & wood	0.30	0.25	0.20	0.17	0.15	0.10	0.20
Solid wood door	Glass & wood	0.14	0.10	0.06	0.08	0.10	0.10	0.10
OSB / chipboard panel (10 mm, air gap) Panel resonator — modest low-frequency absorption over a cavity.	Glass & wood	0.25	0.20	0.15	0.10	0.10	0.10	0.15
Hardboard (3 mm) on battens, air gap Thin panel resonator tuned low; little mid/high absorption.	Glass & wood	0.20	0.15	0.10	0.10	0.10	0.10	0.10
Curtains, lightweight, draped	Soft furnishings	0.05	0.06	0.39	0.63	0.70	0.73	0.45
Curtains, heavy, deep folds	Soft furnishings	0.14	0.35	0.55	0.72	0.70	0.65	0.60
Upholstered seat, fabric, empty	Soft furnishings	0.19	0.37	0.56	0.67	0.61	0.59	0.55
Upholstered seat, leather, empty	Soft furnishings	0.15	0.27	0.39	0.34	0.48	0.52	0.35
Mattress, bare	Soft furnishings	0.22	0.55	0.70	0.70	0.73	0.75	0.65
Filled bookshelf Acts as a partial diffuser/absorber.	Soft furnishings	0.30	0.40	0.40	0.30	0.30	0.30	0.35
Audience, occupied upholstered seats (per m²) Per m² of seated audience — use for occupied home-theatre seating.	Soft furnishings	0.39	0.57	0.80	0.94	0.92	0.87	0.80
Wooden chairs, unoccupied (per m²)	Soft furnishings	0.02	0.02	0.03	0.04	0.04	0.04	0.05
Mineral wool, 50 mm, on wall	Porous absorbers	0.15	0.55	0.90	1.00	1.00	1.00	0.85
Mineral wool, 100 mm, on wall	Porous absorbers	0.45	0.95	1.00	1.00	1.00	1.00	1.00
Mineral wool, 50 mm, 50 mm air gap Air gap boosts low-mid absorption.	Porous absorbers	0.40	0.85	1.00	1.00	1.00	1.00	0.95
Rigid fiberglass 703, 25 mm	Porous absorbers	0.11	0.28	0.68	0.90	0.93	0.96	0.70
Rigid fiberglass 703, 50 mm	Porous absorbers	0.17	0.86	1.00	1.00	1.00	1.00	0.95
Rigid fiberglass 703, 100 mm	Porous absorbers	0.65	1.00	1.00	1.00	1.00	1.00	1.00
Open-cell acoustic foam, 50 mm Weak below 250 Hz despite popularity.	Porous absorbers	0.08	0.25	0.60	0.90	0.95	0.98	0.70
Open-cell acoustic foam, 25 mm	Porous absorbers	0.05	0.12	0.30	0.65	0.85	0.95	0.50
Convoluted egg-crate foam, 50 mm Profiled foam performs like thinner flat foam — weak below 250 Hz.	Porous absorbers	0.05	0.18	0.45	0.70	0.85	0.90	0.55
Mineral wool, 150 mm, on wall Thicker slab extends absorption further into the bass.	Porous absorbers	0.65	1.00	1.00	1.00	1.00	1.00	1.00
Polyester acoustic batt, 50 mm Recycled-PET batt; planning estimate modelled as an equivalent porous absorber.	Porous absorbers	0.12	0.45	0.85	1.00	1.00	1.00	0.85
Wood-wool cement board, 25 mm Cement-bonded wood fibre (e.g. Heraklith); a mid-range absorber.	Porous absorbers	0.10	0.20	0.45	0.55	0.60	0.55	0.45
Acoustic plaster, sprayed (~25 mm) Seamless porous finish; performance depends on thickness and backing.	Porous absorbers	0.17	0.40	0.66	0.65	0.62	0.68	0.60
Fabric-wrapped panel, 50 mm	Acoustic panels	0.16	0.55	0.95	1.00	1.00	0.98	0.90
Fabric-wrapped panel, 100 mm	Acoustic panels	0.52	0.96	1.00	1.00	1.00	0.99	1.00
Fabric panel, 50 mm + 100 mm gap Best broadband value for the money.	Acoustic panels	0.45	0.90	1.00	1.00	1.00	0.98	1.00
PET felt panel, 12 mm	Acoustic panels	0.03	0.07	0.32	0.62	0.78	0.82	0.45
PET felt panel, 24 mm (double layer)	Acoustic panels	0.05	0.15	0.50	0.80	0.85	0.85	0.60
Perforated wood panel + backing Helmholtz behaviour, tuned mid absorption.	Acoustic panels	0.25	0.55	0.80	0.85	0.60	0.40	0.70
Broadband corner trap (300 mm) Floor-to-ceiling triangular corner fill.	Bass traps	0.50	0.85	1.00	1.00	1.00	1.00	0.95
Superchunk corner (mineral wool)	Bass traps	0.60	0.95	1.00	1.00	1.00	1.00	1.00
Tuned membrane trap (~60 Hz) Narrowband — targets a specific room mode.	Bass traps	0.75	0.45	0.20	0.12	0.10	0.10	0.20
Cylindrical tube trap (corner, ~280 mm) Free-standing cylindrical corner absorber; one side can be reflective.	Bass traps	0.45	0.70	0.85	0.90	0.85	0.80	0.85
Mineral-fiber ceiling tile (15 mm)	Ceiling	0.34	0.55	0.68	0.78	0.80	0.78	0.70
Suspended acoustic tile + plenum Plenum gap improves low-frequency absorption.	Ceiling	0.55	0.68	0.72	0.78	0.82	0.80	0.75
Gypsum board ceiling	Ceiling	0.15	0.10	0.06	0.04	0.04	0.05	0.05
Plaster ceiling	Ceiling	0.02	0.02	0.03	0.04	0.05	0.05	0.05
Person, seated (per m² of audience)	People	0.16	0.40	0.55	0.65	0.70	0.70	0.60
Adult, standing (per person, sabins) Value is per person, not per m².	People	0.18	0.40	0.46	0.46	0.51	0.46	0.45

About this dataset

Coefficients are random-incidence values measured per ISO 354 / ASTM C423. They are nominal published figures compiled from standard references and manufacturer datasheets — for product-specific design, check the current manufacturer datasheet. NRC is the average of the 250/500/1000/2000 Hz values rounded to the nearest 0.05. See the methodology page for how these feed the calculators.

Sources

Vorländer, M. — Auralization (Springer), standard material tables.
Cox, T. J. & D’Antonio, P. — Acoustic Absorbers and Diffusers (3rd ed., CRC Press).
Owens Corning 700-series rigid fiberglass board published datasheet.
Knauf / Rockwool mineral-wool acoustic board published datasheets.
Standard architectural-acoustics coefficient tables (ISO 354 / ASTM C423 measured).
Bies, D. & Hansen, C. — Engineering Noise Control, appendix absorption tables.
Beranek, L. & Mellow, T. — Acoustics: Sound Fields and Transducers; standard audience/seating absorption tables.