What this reverberation calculator does
This tool estimates reverberation time (RT60), which is the time it takes for sound to decay by 60 dB after the source stops. RT60 is one of the most useful single numbers in room acoustics. It helps you answer practical questions quickly:
- Will speech be clear or muddy in this room?
- Will music sound dry, balanced, or overly live?
- How much acoustic treatment is likely needed?
- Will adding people, curtains, or panels make a meaningful difference?
How the calculation works
The calculator uses two standard acoustic models for rectangular spaces: the Sabine equation and the Eyring equation. Both are approximations and are most useful in early design, room planning, and treatment sizing.
1) Sabine formula
Sabine is simple and widely used. It performs well in many ordinary rooms, especially when average absorption is moderate.
2) Eyring formula
Eyring tends to be more reliable when the room has higher average absorption. Comparing both values gives a better sense of expected behavior.
Input guide (what each field means)
- Room dimensions: Length, width, and height determine volume and total surface area.
- Surface coefficients: Floor, ceiling, and wall absorption values from 0 to 1 (0 = fully reflective, 1 = fully absorptive).
- Audience absorption: Equivalent absorption area from occupants.
- Additional treatment: Absorbers, curtains, upholstered seating, and other added sabins.
- Room use target: A practical RT60 range for your application (speech, music, theater, etc.).
Typical mid-frequency coefficients (quick reference)
| Material | Approx. α (500–1000 Hz) | General behavior |
|---|---|---|
| Painted concrete / brick | 0.01–0.05 | Very reflective |
| Wood floor | 0.06–0.12 | Low absorption |
| Carpet on pad | 0.20–0.40 | Moderate absorption |
| Gypsum board wall | 0.03–0.08 | Mostly reflective |
| Acoustic ceiling tile | 0.50–0.80 | High absorption |
| Heavy curtains | 0.35–0.70 | Moderate to high absorption |
How to use the result
After calculation, compare the RT60 estimate against the target range for your room type. If your RT60 is too high, speech clarity and transient detail usually suffer. If it is too low, the room may feel acoustically dead or uncomfortable for musical performance.
If RT60 is too high
- Add broadband absorbers on walls or ceiling.
- Increase soft finishes (carpet, curtains, upholstered seating).
- Use distributed treatment instead of placing all panels in one area.
If RT60 is too low
- Reduce excessive absorption in key bands.
- Add diffusion to preserve energy without harsh echoes.
- Balance low-, mid-, and high-frequency treatment.
Important limitations
This calculator is intentionally practical, but simplified. Real rooms are frequency-dependent and often non-rectangular. RT60 can vary dramatically with octave band, occupancy, source location, and measurement method. Use this as an early design estimate, then verify with acoustic measurements or simulation when precision matters.
Frequently asked questions
What is a “good” RT60?
It depends on use. Speech rooms often perform best around 0.5–0.8 seconds, while worship and some music spaces can benefit from longer decay.
Do people really matter that much?
Yes. Occupants can contribute significant absorption, especially in the mid and high frequencies. Empty and occupied RT60 values can differ noticeably.
Should I trust Sabine or Eyring more?
Use both as bounds. In many practical cases they are close. If absorption is high, Eyring often better reflects behavior.