Room acoustics
RT60
The time it takes sound in a room to decay by 60 dB after the source stops, the standard measure of how live or dead a space is.
RT60 is reverberation time: how long a sound takes to fall 60 decibels once it stops. It is usually extrapolated from a shorter decay such as T20 or T30 and reported per frequency band, since rooms often ring longer in the bass.
Long reverberation blurs dialogue and smears the transients that make effects feel real. A room that is too dead sounds oppressive and makes surround effects stop at the speaker. The target is short but not zero.
Aim for about 0.3 to 0.5 seconds across the midband, fairly even from 125 Hz to 4 kHz; untreated living rooms often measure 0.6 to 0.8 s. Sabine's formula, RT60 = 0.161 V / A, links volume in cubic meters to total absorption in square meters.