How this calculator works
Sabine RT60 estimates how long a diffuse sound field takes to drop by 60 dB after the source stops. Equivalent absorption is the sum of each area times its absorption coefficient at the frequency of interest. Rectangular-room mode subtracts doors and windows from wall area. Enter measured or specified coefficients for that frequency. The 0.161 SI coefficient is a conventional room-temperature approximation; air absorption and nonuniform fields are omitted.
Formula
RT60 = 0.161 V/A, with V in m3 and equivalent absorption A in m2. A = sum(alpha_i S_i). Relative level after time t = -60t/RT60 dB.
Worked example
A 100 m3 room with 20 m2 of equivalent absorption gives RT60 = 0.805 s. To achieve 1.61 s in 200 m3, the required absorption is 20 m2.
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Frequently asked questions
Is absorption area the floor area?
No. It is the sum of absorbing contributions from all room surfaces and objects.
Which coefficient should I enter?
Use a coefficient measured at your chosen frequency, with the intended mounting method.
When is Sabine inaccurate?
Highly absorbent, irregular or poorly mixed rooms can need Eyring, ray tracing or measured decay instead.