Room Acoustics Calculator
Why the Same Speakers Sound Different in Two Rooms
A room's reverberation time — how long sound continues to reflect around a space after the source stops — depends on its volume and how much of its surface area absorbs sound versus reflects it. A bare room with hard walls and floors rings much longer than one with carpet, curtains, and furniture, even at identical dimensions. This calculator applies the Sabine equation directly to room dimensions and an average absorption coefficient to estimate that reverberation time, known as RT60.
The Formula
Surface Area = 2 × (L×W + L×H + W×H)
Total Absorption = Surface Area × Average Absorption Coefficient
RT60 = 0.161 × Volume / Total Absorption
RT60 is the time it takes for sound pressure to decay by 60 decibels after the source stops. The 0.161 constant comes from the Sabine equation and assumes metric units (volume in m³, absorption in metric sabins).
A Worked Example
For a 5m × 4m × 2.5m room (volume 50 m³, surface area 85 m²) with an average absorption coefficient of 0.3 — typical of a room with some soft furnishing but mostly hard surfaces — total absorption works out to 25.5 sabins, giving an RT60 of 0.316 seconds.
Typical Absorption Coefficients
| Room character | Typical avg. coefficient |
|---|---|
| Bare room (concrete, glass, tile) | 0.02–0.05 |
| Living room, light furnishing | 0.15–0.25 |
| Living room, carpet and curtains | 0.25–0.35 |
| Treated home studio | 0.35–0.50 |
These ranges are general reference points; actual absorption depends on the specific materials present and should be measured or looked up per-material for precise work.
Where This Gets Used
- Home studio treatment — deciding how much acoustic paneling or bass trapping a room needs to bring RT60 into a target range for recording or mixing.
- Living room speaker setup — understanding why the same stereo system sounds boomy in an empty room and controlled once rugs and furniture are added.
- Conference room and classroom design — excessive RT60 degrades speech intelligibility, which is why these spaces target shorter reverb times than concert halls.
How to Use This Calculator
- Enter the room length, width, and height in meters.
- Enter the average absorption coefficient for the room's surfaces, a value between 0 and 1.
- Select Calculate to see the computed volume, surface area, total absorption, and RT60.
Related Calculations
For a more precise reverb estimate using per-surface data or the Eyring equation, see the Reverb Time Calculator, or check speaker placement impedance with the Speaker Impedance Calculator.