# Derivation of Sabine's formula for reverberation time

1. Nov 12, 2014

### smart_worker

2. Nov 12, 2014

### M Quack

Hmmm, looks pretty clear to me, but it was obviously written by a physicist for physicists.

The first part is deriving that the time derivative dW/dt of the acoustic energy W is proportional to the acoustic energy.

From that it follows that the acoustic energy must decay exponentially, with the time constant derived above tau_W = 4V/(cA).

T60 (T30) is defined as the time by which the acoustic energy has decayed by -60 dB (-30 dB) = 10^-6 (10^-3).

tau_W is defined as the time by which the acoustic energy has decayed by 1/e. T60 and T30 are just tau_W multiplied by constants.