The energy decay relief (EDR) is a time-frequency distribution which generalizes the EDC to multiple frequency bands [199]:
Thus, is the total amount of signal energy remaining in the reverberator at time in a frequency band centered about Hz, where denotes the FFT length.
The EDR of a violin-body impulse response is shown in Fig. 2.2. For better correspondence with audio perception, the frequency axis is warped to the Bark frequency scale [431], and energy is summed within each Bark band (one critical band of hearing equals one Bark). A violin body can be regarded as a very small reverberant room, with correspondingly ``magnified'' spectral structure relative to reverberant rooms.
The EDR of the Boston Symphony Hall is displayed in [145, p. 96].