Room acoustics
Sabin Absorption & RT60 Calculator
Calculate equivalent absorption area from surface areas and absorption coefficients, then estimate reverberation time with the Sabine equation when room volume is known.
Equivalent absorption area
Enter each surface or treatment area and its absorption coefficient for the frequency band you are evaluating. Use manufacturer or measured coefficients for serious design work.
| Surface / material | Area ft² | Absorption coefficient α | Absorption |
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Absorption coefficients vary with frequency. For octave-band analysis, calculate each band separately using the coefficient for that band rather than a single NRC-style average.
What a sabin represents
One sabin is the absorption provided by one square unit of perfectly absorbing surface. A 100 ft² surface with an absorption coefficient of 0.60 contributes 60 imperial sabins at that frequency. The same calculation in metric units produces square metres of equivalent absorption area.
Using the calculator for treatment planning
Start with the untreated room surfaces, then add absorbers, seating, curtains or other significant elements as separate rows. If you know the room volume, the calculator estimates RT60 and the equivalent absorption required to reach a selected target RT60. The difference provides a first-pass estimate of how much additional absorption is required.
The result is most useful when calculated by octave band. A porous absorber may have a very high coefficient at 1 kHz but a much lower coefficient at 125 Hz, so a single broadband number can conceal the behavior that matters most.
When the Sabine equation is appropriate
Sabine is a classical diffuse-field approximation. It is most useful when absorption is reasonably distributed and the room is not extremely absorptive. Small studios, highly treated rooms, coupled spaces and rooms with strongly nonuniform absorption may deviate substantially from the estimate.
For more heavily absorptive spaces, the Eyring relationship can be more appropriate. For commissioning or critical design, calculated reverberation time should be checked against measured decay rather than treated as an exact prediction.
Do not confuse sabins with absorption coefficient
An absorption coefficient is dimensionless and describes the fraction of incident sound energy absorbed by a material under a particular test condition. Sabins represent equivalent absorption area. Multiplying area by coefficient converts the material description into the amount of absorption contributed to the room model.