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Re: envelope extraction

Hello Ben,

You are right to question auditory models with transduction filters whose cutoff is below about 1000 Hz. They are often just trying to explain amplitude modulation detection without concern for other aspects of auditory processing.

There is a discussion of the different methods of extracting envelopes in Yost et al. 1998, reference below. It concludes that if you want to be able to explain the pitch shift of the residue, there is only one of the methods that can be used to represent auditory processing, and that is half-wave rectification followed by lowpass filtering. The filter needs to have a relatively high cutoff frequency, 800-1200 Hz and beyond the cutoff, the filter should fall about 24 dB per octave. 

Regards Roy P

Yost, W.A., Patterson, R.D. and Sheft, S. (1998). The role of the envelope in processing iterated rippled noise. J. Acoust. Soc. Am. 104 2349-2361.

Hornsby, Benjamin Wade Young wrote:

Hi all,

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?


Thanks much,





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Roy D. Patterson
Centre for the Neural Basis of Hearing
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