Sound Absorption Calculator
Total room absorption (in sabins) is needed to calculate reverberation time using Sabine's formula. For each surface in the room, the contribution is area (m^2) multiplied by the absorption coefficient (alpha, 0 to 1). The total A = sum of all (area x alpha). This calculator supports up to four surfaces. Once you have the total absorption, use the reverberation time calculator to find RT60. Common applications include studio design, classroom acoustics, and noise control in industrial facilities.
Sound absorption formula
A = Σ (Si × αi)
Where S_i is the area of each surface in m^2 and alpha_i is its absorption coefficient. A is in sabins (equivalent m^2 of perfect absorption).
Absorption coefficients for common materials
- Smooth concrete / brick: 0.02-0.05
- Plasterboard wall: 0.05-0.10
- Wood floor: 0.05-0.15
- Carpet on hard floor: 0.20-0.40
- Upholstered seating: 0.50-0.80
- Acoustic foam (50 mm): 0.70-0.95
Frequently asked questions
What is a sabin?
A sabin is the unit of acoustic absorption. One sabin equals the absorption provided by one square metre of a perfectly absorbing surface (absorption coefficient = 1.0). The total absorption A in sabins is the sum of area x alpha for all surfaces in the room.
What are typical absorption coefficients?
Absorption coefficients (alpha) range from 0 (perfectly reflective) to 1 (perfectly absorptive). Painted concrete: 0.02; carpet on concrete: 0.30; heavy curtain: 0.50; acoustic foam: 0.70-0.95; open window (standard reference): 1.0.
How does absorption relate to RT60?
Total absorption A in sabins goes directly into Sabine's formula: RT60 = 0.161 V / A. Doubling the total absorption halves the reverberation time.
Does absorption coefficient vary with frequency?
Yes. Absorption coefficients are frequency-dependent and are typically tabulated at octave bands (125, 250, 500, 1,000, 2,000, 4,000 Hz). This calculator accepts a single value for a simplified broadband estimate. For precise design, calculate A at each octave band.
What are imperial sabins (ft^2)?
An imperial sabin is the absorption of one square foot of a perfectly absorbing surface. One metric sabin (m^2) equals approximately 10.76 imperial sabins. Sabine's RT60 constant changes to 0.049 when using imperial sabins and ft^3.
Official sources
- AES: Audio Engineering Society.
- ANSI/ASA S12.60: Acoustical Performance Criteria for Schools.
- OpenStax University Physics Vol. 1, Chapter 17: Sound.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.