1/3 Octave (Reverberation times only)

Third-octave band filters, responses corresponding to the requirements in IEC1260 [IEC 1260: 1995, Electroacoustics – Octave-band and fractional-octave-band filters]. Lowest 1/3-octave where calculation is attempted is 40Hz, highest band depends on the sampling frequency of the measured impulse response. For this bandwidth only reverberation times is generally of interest, and therefore only the reverberation time parameters T30, early decay time (EDT) and user defined reverberation time (Tu) can be calculated.

To minimize the influence of the filter response on the reverberation time calculation, the impulse responses are filtered backwards. This greatly improves the accuracy for short decay times at low frequencies.