Statistical reverberation and receiver decay#
Reverberation time (RT60)#
Room Analysis estimates RT60 statistically using room quantities and absorption. Its method is described in Room Analysis. Ray EDT, T20 and T30 are derived from backward-integrated receiver energy and fitted decay ranges.
Receiver energy and decay fits#
Backward-integrated receiver energy
Backward integration gives the energy remaining after each point in the retained receiver response. Ray analysis integrates received energy directly; measured pressure responses use squared pressure.
- e(t)
- Receiver energy per unit time in one octave band (consistent energy unit/s)
- t, τ
- Time measured from the response arrival origin (s)
- tₑₙd
- End of the retained response (s)
- R(t)
- Remaining integrated energy (consistent energy unit)
M. R. Schroeder (1965), New Method of Measuring Reverberation Time.
Normalised energy decay
This curve expresses the remaining receiver energy relative to its initial value in decibels.
- L(t)
- Normalised decay level (dB)
- R(t), R(0)
- Remaining and initial integrated energy (consistent energy unit)
M. R. Schroeder (1965), New Method of Measuring Reverberation Time.
Extrapolated decay time
A fitted decay slope is extrapolated to estimate the time for a 60 dB decay.
- T₆₀
- Extrapolated decay time (s)
- b
- Slope fitted over the applicable decay range (dB/s)
M. R. Schroeder (1965), New Method of Measuring Reverberation Time.
Early decay time (EDT)#
Initial decay fitted from 0 to −10 dB, extrapolated to a 60 dB time.
Reverberation time (T20)#
Decay fitted from −5 to −25 dB, extrapolated to a 60 dB time.
Reverberation time (T30)#
Decay fitted from −5 to −35 dB, extrapolated to a 60 dB time.
Decay fit support and limitations#
A response must support the requested range and the calculation's quality checks. Short, incomplete or non-linear decays can limit a fit. A displayed number is not evidence that every decay range is available or that a single straight-line decay represents the entire room.
Low-frequency decay balance#
Low-frequency decay balance compares low- and mid-frequency decay times using the same decay method. It is a dimensionless ratio; values above one indicate longer low-frequency decay.