Calculated Results
These values appear after you press the calculate button.
Interpretation
Run the calculator to see an acoustic interpretation.
Calculator Inputs
Use metric dimensions and realistic absorption coefficients between 0 and 1.
Plotly Graph
The chart compares reverberation predictions from the main acoustic methods.
Example Data Table
This sample shows a medium lecture room with mixed finishes and seated occupancy.
| Parameter | Example Value | Unit | Notes |
|---|---|---|---|
| Length | 12 | m | Main room dimension |
| Width | 9 | m | Side-to-side dimension |
| Height | 3.5 | m | Finished ceiling height |
| Floor coefficient | 0.08 | - | Hard finish floor |
| Ceiling coefficient | 0.55 | - | Acoustic ceiling treatment |
| Long wall coefficient | 0.12 | - | Painted wall with partial treatment |
| Short wall coefficient | 0.15 | - | Front and rear wall absorption |
| Occupants | 20 | persons | Seated users |
| Absorption per occupant | 0.45 | sabins | Approximate broadband value |
| Seats | 40 | units | Upholstered chairs |
| Absorption per seat | 0.35 | sabins | Per empty upholstered seat |
Formula Used
1) Room Volume
V = L × W × H
Where V is volume in cubic meters.
2) Total Surface Area
S = 2(LW + LH + WH)
This is used to derive the average absorption coefficient.
3) Equivalent Absorption Area
A = Σ(Surface Area × Absorption Coefficient) + Occupant Absorption + Seat Absorption
This gives total absorption in sabins.
4) Sabine Equation
RT60 = 0.161 × V / A
Best for rooms with relatively low average absorption.
5) Eyring Equation
RT60 = 0.161 × V / [-S × ln(1 - ᾱ)]
Where ᾱ is the average absorption coefficient, equal to A / S.
6) Fitzroy Approximation
RT60 = 0.161 × V / (Ax + Ay + Az)
For this implementation, directional absorption terms are estimated from opposing wall pairs, plus floor and ceiling contributions. This helps when absorption is not evenly distributed.
How to Use This Calculator
- Enter room length, width, and height in meters.
- Set absorption coefficients for the floor, ceiling, long walls, and short walls.
- Enter the number of occupants and their approximate absorption contribution.
- Enter the number of upholstered seats and their absorption value.
- Select the intended room use to compare the result against a practical target.
- Press the calculate button to show results above the form.
- Review the graph, interpretation, and method comparison.
- Export the result summary using the CSV or PDF buttons.
Useful Acoustic Notes
Short RT60 improves speech clarity Long RT60 adds liveliness for music High occupancy reduces reverberation Soft finishes increase absorption Ceiling treatment is often highly effective Uneven absorption can affect room characterFrequently Asked Questions
1) What is reverberation time?
Reverberation time, often called RT60, is the time needed for sound energy in a room to decay by 60 decibels after the source stops. It helps describe how live, echoic, or controlled a space sounds.
2) Why does this calculator use more than one equation?
Different acoustic models behave better under different absorption conditions. Sabine is widely used for lighter absorption, while Eyring usually gives better estimates in more absorbent rooms. Fitzroy helps when surface absorption is unevenly distributed.
3) What absorption coefficient values should I enter?
Use values between 0 and 1. Hard reflective finishes often fall near 0.02 to 0.10, while acoustic panels and heavy absorbers can be much higher. Use published manufacturer data whenever possible.
4) Does furniture or occupancy really matter?
Yes. People, chairs, curtains, and soft furnishings can noticeably increase total absorption. A nearly empty room usually has a longer reverberation time than the same room when fully occupied.
5) What reverberation time is good for speech rooms?
Speech-focused spaces often benefit from shorter reverberation times, commonly around 0.4 to 0.8 seconds, depending on room size and purpose. Lower values generally improve clarity, especially in classrooms and meeting rooms.
6) What reverberation time is good for music rooms?
Music spaces usually tolerate or prefer longer reverberation times than speech rooms. Small rehearsal areas may work around 0.8 to 1.2 seconds, while larger performance spaces may be designed for significantly longer values.
7) Is this calculator frequency dependent?
This version gives a broadband estimate. Real acoustic behavior changes with frequency, so professional room design often evaluates separate octave or one-third-octave bands using material data for each band.
8) Can I rely on this for final acoustic design?
This tool is excellent for planning, screening, and educational use. Final design should still consider frequency behavior, room geometry, diffusion, sound isolation, source placement, and verified product absorption data.