Acoustic absorption coefficients table
Table shows sound absorption coefficient for different building materials.

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Floor materials#

Material125 Hz250 Hz500 Hz1 kHz2 kHz4 kHz
Carpet0.010.020.060.150.250.45
Concrete (unpainted, rough finish)0.010.020.040.060.080.1
Concrete (sealed or painted)0.010.010.020.020.020.02
Marble or glazed tile0.010.010.010.010.020.02
Vinyl tile or linoleum on concrete0.020.030.030.030.030.02
Wood parquet on concrete0.040.040.070.060.060.07
Wood flooring on joists0.150.110.10.070.060.07

Seating Materials#

Material125 Hz250 Hz500 Hz1 kHz2 kHz4 kHz
Benches (wooden, empty)0.10.090.080.080.080.08
Benches (wooden, 2/3 occupied)0.370.40.470.530.560.53
Benches (wooden, fully occupied)0.50.560.660.760.80.76
Benches (cushioned seats and backs, empty)0.320.40.420.440.430.48
Benches (cushioned seats and backs, 2/3 occupied)0.440.560.650.720.720.67
Benches (cushioned seats and backs, fully occupied)0.50.640.760.860.860.76
Theater seats (wood, empty)0.030.040.050.070.080.08
Theater seats (wood, 2/3 occupied)0.340.210.280.530.560.53
Theater seats (wood, fully occupied)0.50.30.40.760.80.76
Seats (fabric-upholsterd, empty)0.490.660.80.880.820.7
Seats (fabric-upholsterd, fully occupied)0.60.740.880.960.930.85

Reflective wall materials#

Material125 Hz250 Hz500 Hz1 kHz2 kHz4 kHz
Brick (natural)0.030.030.030.040.050.07
Brick (painted)0.010.010.020.020.020.03
Concrete block (coarse)0.360.440.310.290.390.25
Concrete block (painted)0.10.050.060.070.090.08
Concrete (poured, rough finish, unpainted)0.010.020.040.060.080.1
Doors (solid wood panels)0.10.070.050.040.040.04
Glass (1/4 inch plate, large pane)0.180.060.040.030.020.02
Glass (small pane)0.040.040.030.030.020.02
Plasterboard (12 mm paneling on studs)0.290.10.060.050.040.04
Plaster (gypsum or lime, on masonry)0.010.020.020.030.040.05
Plaster (gypsum or lime, on wood lath)0.140.10.060.050.040.04
Plywood (3mm paneling over 31.7 mm airspace)0.150.250.120.080.080.08
Plywood (3mm paneling over 57.1mm airspace)0.280.20.10.10.080.08
Plywood (5mm paneling over 50mm airspace)0.380.240.170.10.080.05
Plywood (5mm panel, 25mm fiberglass in 50mm airspace)0.420.360.190.10.080.05
Plywood (6mm paneling, airspace, light bracing)0.30.250.150.10.10.1
Plywood (10mm paneling, airspace, light bracing)0.280.220.170.090.10.11
Plywood (19mm paneling, airspace, light bracing)0.20.180.150.120.10.1

Absorptive wall materials#

Material125 Hz250 Hz500 Hz1 kHz2 kHz4 kHz
Drapery (10 oz/yd2, 340 g/m2, flat against wall)0.040.050.110.180.30.35
Drapery (14 oz/yd2, 476 g/m2, flat against wall)0.050.070.130.220.320.35
Drapery (18 oz/yd2, 612 g/m2, flat against wall)0.050.120.350.480.380.36
Drapery (14 oz/yd2, 476 g/m2, pleated 50%)0.070.310.490.750.70.6
Drapery (18 oz/yd2, 612 g/m2, pleated 50%)0.140.350.530.750.70.6
Fiberglass board (25mm)0.060.20.650.90.950.98
Fiberglass board (50 mm)0.180.760.990.990.990.99
Fiberglass board (75 mm)0.530.990.990.990.990.99
Fiberglass board (100mm)0.990.990.990.990.990.97
Open brick pattern over 75 mm fiberglass0.40.650.850.750.650.6
Pageboard over 25 mm fiberglass board0.080.320.990.760.340.12
Pageboard over 50mm fiberglass board0.260.970.990.660.340.14
Pageboard over 75mm fiberglass board0.490.990.990.690.370.15
Performated metal (13% open, over 50mm fiberglass)0.250.640.990.970.880.92

Ceiling Material#

Material125 Hz250 Hz500 Hz1 kHz2 kHz4 kHz
Plasterboard (12mm in suspended ceiling grid)0.150.110.040.040.070.08
Underlay in perforated metal panels (25 mm batts)0.510.780.570.770.90.79
Metal deck (perforated channels, 25 mm batts)0.190.690.990.880.520.27
Metal deck (perforated channels, 75mm batts)0.730.990.990.890.520.31
Plaster (gypsum or lime, on masonary)0.010.020.020.030.040.05
Plaster (gypsum or lime, rough finish or timber lath)0.140.10.060.050.040.04
Sprayed cellulose fiber (16 mm on solid backing)0.050.160.440.790.90.91
Sprayed cellulose fiber (25mm on solid backing)0.080.290.750.980.930.76
Sprayed cellulose fiber (25mm on timber lath)0.470.91.11.031.051.03
Sprayed cellulose fiber (32mm on solid backing)0.10.30.730.920.980.98
Sprayed cellulose fiber (75mm on solid backing)0.70.9510.850.850.9
Wood tongue-and-groove roof decking0.240.190.140.080.130.1

Miscellaneous surface material#

Material125 Hz250 Hz500 Hz1 kHz2 kHz4 kHz
People-adults (per 1/10 person)0.250.350.420.460.50.5
People-high school students (per 1/10 person)0.220.30.380.420.450.45
People-elementary students (per 1/10 person)0.180.230.280.320.350.35
Ventilating grilles0.30.40.50.50.50.4
Water or ice surface0.0080.0080.0130.0150.020.025

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:
    α+β+τ=1\alpha + \beta + \tau = 1
    where:
    • α\alpha - absorption coefficient (determines the part of the energy that was absorbed inside the wall),
    • β\beta - reflection coefficient (defines the part of the energy remaining in the first room),
    • τ\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:
    α=Eabs.Einc.\alpha = \frac{E_{abs.}}{E_{inc.}}
    where:
    • Eabs.E_{abs.} - energy of the absorbed wave,
    • Einc.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.

See also#

If you're interested in calculators related to acoustics, check out our other calculators:
  • Sound intensity level (dB) - if you want to learn what is decibel and how the sound intensity level is measured,
  • Sound velocity in materials - if you want to learn how the type of substance affects the speed of acoustic wave propagation,
  • Acoustic impedance of substances - if you want to learn what is acoustic impedance and how it depends on the type of substance,
  • Sound wave reflection - if you want to find out how an acoustic wave behaves when it encounters an obstacle in the form of media boundary,
  • Mass law: single wall - if you're interested in building acoustics and would like to estimate the acoustic insulation of a single wall,
  • Mass law: double wall - if you're interested in building acoustics and would like to estimate the acoustic insulation of a double wall with an air gap between the walls,
  • Sound absorption coefficients - if you're interested in acoustic adaptation of room and you would like to learn how different materials absorb the acoustic wave,
  • Noise propagation - if you want to learn how sound intensity level changes with distance from the source,
  • Sound insulation countours - if you want to learn more about acoustic insulation assessment standards used over the world,
  • Sound reduction index (SRI) - if you're searching for acoustic insulation of popular building materials expressed in the coefficient Rw,
  • Sound transmission class (STC) - if you're searching for acoustic insulation of popular building materials expressed by the index STC.

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