I hope the answer to this question is not too obvious but,… We have recently been talking about auditory processing models, in specific, temporal processing models, many of which incorporate an envelope extraction stage. To do this I’ve seen in many cases the use of half wave rectification followed by a low pass filter. The cutoff for this filter is generally a pretty low frequency, say around 50 Hz or so. A colleague suggested that the actual cutoff frequency should be based on the assumed time constant of the system or subsystem being evaluated. I’ve been trying to determine the physiologic rational for such a low frequency filter (slow time constant) in models of auditory processing. Neural processing limitations like the refractory period of the neuron are much faster than this. Anyone have a reference or two that might help explain the physiologic rational for this low frequency filter cutoff?