RT60 Calculator

The RT60 calculator computes reverberation time — the period it takes for sound energy in a room to decay by 60 dB after the source stops. The tool uses two classical formulas: Sabine and Eyring. Sabine's formula works well for rooms with moderate absorption where the average surface coefficient is below 0.3. Eyring's formula is more accurate at higher absorption levels — it yields finite RT60 values even with fully absorptive surfaces, unlike Sabine's. Why it matters: reverberation time is the key indicator of acoustic quality for any room. In control rooms, the target is typically 0.2 – 0.4 s; in recording rooms 0.3 – 0.6 s; in concert halls 1.0 – 2.0 s. Too short a time makes the sound dry and lifeless; too long blurs detail and critically reduces the intelligibility of speech and music. How to read results: compare the computed value against the target for your room type. The calculator shows RT60 by octave band — pay special attention to low frequencies: in small rooms RT60 at 63 – 125 Hz is often two to three times higher than at midrange frequencies, creating a "boomy" bass effect. Common mistakes: using Sabine's formula for heavily damped rooms, which yields inflated results; not accounting for furniture and people as absorptive surfaces; entering surface areas without correcting for real mounting conditions of materials. Next steps: use the Treatment Planner to choose materials and see how absorber placement affects RT60 across each octave band.