Perceptual Metrics for Ideal Reverberation

Some desirable controls for an artificial reverberator include [219]

• $t_{60}(f) =$ desired reverberation time at each frequency $f$
• $G^2(f) =$ signal power gain at each frequency
• $C(f) =$ ``clarity'' = ratio of impulse-response energy in early reflections to that in the late reverb
• $\rho(f) =$ interaural correlation coefficient at left and right ears

The time to decay 60 dB ($t_{60}$ ) is a classical objective parameter used as a measure of perceived reverberation time. Classically, $t_{60}$ was measured for the whole response. More recently [217], it has become more common to design for a given $t_{60}$ 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 [218].