Reverberation time
= Reverberation time
{title2=$T_{60}$}
The conventional <reverberation time> $T_{60}$ is the time for the level of decaying acoustic <energy> to decrease by $60$ <decibels>, a factor $10^6$ in <energy> or $10^3$ in pressure <wave amplitude>. For exponential <energy> decay $E(t)=E(0)e^{-t/\tau_E}$, $T_{60}=6\ln(10)\tau_E$. It is not the <exponential relaxation time> itself and cannot be inferred exactly from an unspecified audibility threshold.