Perceptual Metrics for Ideal Reverberation
Some desirable controls for an artificial reverberator include 
- desired reverberation time at each frequency
- signal power gain at each frequency
- ``clarity'' = ratio of impulse-response energy in early reflections to that in the late reverb
- interaural correlation coefficient at left and right ears
The time to decay 60 dB () is a classical objective parameter used as a measure of perceived reverberation time. Classically, was measured for the whole response. More recently , it has become more common to design for a given at more than one frequency, e.g., one for low frequencies, another for high frequencies, and interpolated values at intermediate frequencies. Perceptual studies indicate that reverberation time should be independently adjustable in at least three frequency bands .
The EDR of a violin-body impulse response is shown in Fig.3.2. For better correspondence with audio perception, the frequency axis is warped to the Bark frequency scale , 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 [153, p. 96].
Desired Qualities in Late Reverberation
Perception of Echo Density and Mode Density