RT60 Reverberation Calculator

RT60: reverberation time using Sabine's formula

RT60 measures how long sound takes to decay 60 dB once the source goes quiet. Sabine worked out the relationship back in 1900: RT60 = 0.161·V/A, with V the room volume in m³ and A the total absorption in m² Sabin (each surface area multiplied by its absorption coefficient, all added up). Run the numbers on a 100 m³ room with 25 m² Sabin and you get RT60 = 0.161·100/25 = 0.64 s. What you usually aim for varies a lot: living room ~0.5 s, recording studio < 0.3 s, concert hall 1.5–2 s, church 2 s+. Worth checking against NBR 10152 (ambient noise limits) and NBR 12179 (acoustic treatment design).

Applications

It shows up in the acoustic design of home studios (mixing rooms, vocal booths), in concert halls and theatres where a longer RT60 makes music bloom, in recording studios kept very dry for clean takes, and in noise-sensitive places such as schools and hospitals, where too much reverberation makes speech hard to follow. Sabine holds up well for diffuse fields; once a room gets very absorbent, switch to Eyring's correction.

FAQ

What is the ideal RT60 for a home office? Somewhere around 0.4–0.6 s. Go lower and the room starts to sound muffled; push past 0.8 s and people struggle to understand you on video calls.

How do I increase absorption (A)? Hang rockwool, fiberglass or acoustic foam panels on the walls and ceiling, throw down thick rugs, bring in upholstered furniture and heavy curtains. Every m² you treat adds its own absorption coefficient to the total.

Why does a church reverberate so much? The volume V is huge, often 5,000 m³+, and the surfaces are hard and reflective (stone, glass), so A stays small and RT60 climbs. That suits organ and choir beautifully, but it wrecks the spoken word unless you add sound reinforcement.