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,
Ben
--
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Roy D. Patterson
Centre for the Neural Basis of Hearing
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University of Cambridge
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