Comb filter with a low-pass element built into the feedback loop, for use as a unit reverberator according to the design in [Moorer2] (based on the ideas of Schroeder).
A verbatim implementation of the filter shown in Fig. 5 of [Moorer2]. The transfer function, T(z), is given by: T(z) = z-m /(1 -g2 z-m -g1g2 z-(m+1)) where the delay, m, and gains, g1 and g2, are adjusted via the Parameter Window, as summarised in the following table. Parameter Purpose "Delay" slider Adjusts the comb delay, m, expressed in milliseconds. The available range of 50 to 80 ms is recommended in [Moorer2] "Gain" slider Adjusts the quantity denoted g in [Moorer2] which determines the "reverberation time". A value of 0.83 gives a reverberation time of about 2 seconds, for delays between 50 to 80 ms. The filter gains g1 and g2 are related to g according to the following formula (from [Moorer2]): g2= g (1-g1). "Gain 1" slider Adjusts the low-pass filter gain, g1, which is intended to simulate the absorption of high frequencies by the air inside a room. Table 2 in [Moorer2] lists suitable values for g1 for a range of delays, obtained from a series of optimizations designed to match the model filter frequency reponse with measured data. The delays are implemented using circular buffers. For more information on room acoustics and reverberation, see, for example: [Roa] p. 477-492, [Moore] p. 370-394, [Ros]p. 459-493, [Be] p. 172-222, [Zo] p. 181-205, plus various articles in [AES8] and [AES16].
