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Re: ERB at high levels
Thanks, Pierre, but I don't think I have a distribution of the latest
model and the latest filter fitting data yet, and it might not be the
answer he's looking for anyway.
The question as posed leads to two immediate difficulties:
1. Nobody knows exactly what the filters, or their shapes, are; and
the ERB depends on what shape you assume, and what data you fit it to.
2. The dependence on dB SPL is ambiguous. What level should one use
to parameterize the filter shapes? The level of a probe tone that's
just audible in a simultaneous masker? The masker level per Hz?
With help from Unoki and Patterson, I recently redid some fits to
simultaneous notch-noise masker data of Baker et al. and of Glasberg
and Moore, using several gammachirp, gammatone, and related filter
models, including the pole-zero filter cascade (PZFC), which is
probably what Pierre is referring to. I parameterized the ERB in
terms of the threshold probe level, up to 70 dB SPL, in which case
the total noise level is probably around 90 dB SPL, at least for some
notch widths. At these levels the ERB is typically about twice the
reference ERB curve of Glasberg and Moore 1990.
This is not significantly different from what Patterson, Unoki, and
Irino reported in their 2003 JASA article. But the dependence of ERB
on level does vary quite a bit depending on which filter model you
choose to fit, so there's really not a definitive answer from these
data sets and fits.
Whether the ERB becomes constant at high levels, or continues to
grow, is not yet clear. And even if you get a clear answer for that
from other psychoacoustic experiments, it doesn't necessarily mean
that's exactly what's happening in the cochlear mechanics; or vice
versa. But probably others do have more data points relevant to the
As for my latest PZFC cochlea model, it's now integrated into Roy
Patterson's AIM-MAT package, using parameters determined by the
fitting to the human masking data (under the assumption that the
psychoacoustic features correspond to cochlea channel filters, which
Steve Greenberg warns me may not be a good assumption). Hopefully an
AIM-MAT release with this is not too far off; we may want to tweak it
a bit more first.
At 6:06 PM -0700 4/25/08, Pierre Divenyi wrote:
Check out Dick Lyon's new cochleogram (also misnamed cochleagram)
model on his web site. He spent a long time trying to come up with
the correct parameters. In any case, the model is beautiful.
At 10:29 AM 4/25/2008, Ken Grant wrote:
We are looking for any data or model of ERB as a function of level.
We are aware of the Oxenham and Simonson (2006) and the Baker and
Rosen (2006) papers which don't go above 70 dB SPL. We would like
to hear any suggestions as to what people think normal-hearing ERBs
at 500, 1000, 2000, and 4000 look like at input levels as high as
90-95 dB SPL.
Ken W. Grant
Walter Reed Army Medical Center
Army Audiology and Speech Center
Building 2, Room 6A53C
Washington, DC 20307-5001