Sabine Reverberation Time

Estimate frequency-specific RT60 and additional equivalent absorption for a target decay time.

How this calculation works

Sabine's relation estimates the time for sound level to decay by 60 dB from room volume and equivalent absorption. Enter the room volume, total boundary surface area, an area-weighted boundary absorption coefficient and any additional equivalent absorption from objects or occupants. All absorption data and the target time must refer to the same frequency band. Boundary area times coefficient, plus the object contribution, gives total equivalent absorption. The calculator uses this total to estimate RT60 and the extra absorption needed to reach the target; a target already met gives zero additional requirement. Equivalent absorption is not the same as physical panel area. The model assumes a diffuse field with reasonably distributed, low-to-moderate absorption, and excludes room modes, air absorption and treatment-placement analysis.

Inputs and units

Room volume (m³)
Total room boundary area (m²)
Area-weighted boundary absorption coefficient (1)
Additional object/occupant equivalent absorption (m²): Use data for the same frequency band; avoid counting surfaces twice
Target reverberation time (s)

Method and formula

A = S × mean absorption coefficient + Aobjects; RT60 = 0.161V/A; additional A = max(0, 0.161V/target RT60 − A).

Worked example

Example inputs

Room volume: 300 m³
Total room boundary area: 300 m²
Area-weighted boundary absorption coefficient: 0.1 1
Additional object/occupant equivalent absorption: 10 m²
Target reverberation time: 0.8 s

Calculation steps

Calculate total equivalent absorption: A = 300 × 0.1 + 10 = 40 m².
Estimate reverberation time: RT60 = 0.161 × 300/40 = 1.2075 s.
Find the absorption required for a 0.8 s target: Atarget = 0.161 × 300/0.8 = 60.375 m².
Subtract existing absorption: additional A = max(0, 60.375 − 40) = 20.375 m² of equivalent absorption.

Example results

Sabine RT60: 1.2075 s
Total equivalent absorption: 40 m²
Additional equivalent absorption for target: 20.375 m²

Assumptions

Diffuse room sound field and low-to-moderate, reasonably distributed absorption
All absorption coefficients and target RT60 refer to the same frequency band

Limitations

No air-absorption correction, room modes or uneven-treatment analysis
Equivalent absorption is not the physical panel area; panel effectiveness depends on tested installation

Sources

Montana State University: Room Acoustics Lecture: Sabine RT60 and equivalent absorption sum
Duke University: Reverberation: Sabine assumptions and uneven absorption limitations