When recording RMS level statistics, the instantaneous RMS signal is low-pass-filtered with an adjustable time constant.

The time constant is only relevant when recording RMS level statistics, and is only used to detect min and max values. The average is calculated by a rectangular integration over the log interval. A shorter time constant should be chosen to detect sharp transients. Otherwise the measurements will be smoothed out. On the other hand, when the RMS levels are slowly varying, a longer time constant will provide more precise values.

Typical fast time constants are 100 ms and under.

Typical slow time constants are 1s and over.