Re: ERB at high levels ("Richard F. Lyon" )

Subject: Re: ERB at high levels
From:    "Richard F. Lyon"  <DickLyon@xxxxxxxx>
Date:    Fri, 25 Apr 2008 22:44:39 -0700

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? Other? 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 question. 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. Dick At 6:06 PM -0700 4/25/08, Pierre Divenyi wrote: >Ken, > >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. > >Pierre > >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 >> >>Work: 202-782-8596 >>Fax: 202-782-9228 >> >>email: grant@xxxxxxxx

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