Reverberation time (RT60) is how long a sound takes to fade by 60 dB after it stops. For classrooms, a good target is about 0.60 seconds at mid frequencies.
| Space | Typical target |
|---|---|
| Recording studio control room | 0.2–0.4 s |
| Home office, podcast room | 0.3–0.5 s |
| Classroom (ANSI S12.60) | ≤ 0.6 s |
| Conference room | 0.4–0.6 s |
| Restaurant | 0.6–0.9 s |
| Lecture hall | 0.7–1.0 s |
| House of worship (speech and music) | 1.0–1.8 s |
| Gymnasium | 1.2–2.0 s |
The typical classroom we used in these guides measures about 2.66 s untreated, so it is well above the target.
How to measure it
A free phone app can measure RT60 from a balloon pop or a hand clap. Measure in several spots, then average the results at 500 Hz and 1,000 Hz. See what RT60 is.