Decay times

The reverberation time (T30), is the 60dB decay time calculated by a line fit to the portion of the decay curve between -5 and -35dB. If the decay range is less than 35dB, the T30 is in WinMLS calculated using the range available. It is therefore important when using the T30, to keep an eye on the SNR to evaluate the quality. To be a valid measurement according to the ISO 3382 standard, the SNR should be displayed as 35dB or larger.

The standard recommends a certain safety margin to the noise floor. It should be noted that the Noise margin parameter taken into account before forming the decay curve and calculating the decay range provides this safety margin. It is user changeable and described in the Integration options section.

The early decay time (EDT), is the 60dB decay time calculated by a line fit to the portion of the decay curve between 0 and -10dB.

The user defined reverberation time (Tu), is the 60dB decay time calculated by a line fit to the portion of the decay curve in an interval specified in the level limit boxes, remembering the minus signs in front. It is often used as a T15 (-5 to –20dB) or T20 (-5 to –25dB) parameter, giving a well defined decay time measure for responses with inferior decay range, or providing an indication of double sloping of the decay if it is significantly different from the T30.

All the decay time parameters are given in seconds. If the decay range in a particular frequency band is insufficient for EDT or Tu measurement, no calculation will be carried out.