Re: Cochlear AGC attack/release times (Abeer Alwan )


Subject: Re: Cochlear AGC attack/release times
From:    Abeer Alwan  <abeera(at)ICSL.UCLA.EDU>
Date:    Mon, 23 May 2005 22:34:31 -0700

Brian Strope wrote a very nice Ph.D. dissertation on the topic (1998) and an IEEE article (1997). He derived the attack/release times from carefully-designed forward-masking experiments: B. Strope and A. Alwan, "A model of dynamic auditory perception and its application to robust word recognition," IEEE Transactions on Speech and Audio Processing, Vol. 5, No. 5, pp. 451-464, September 1997. Both the dissertation and article can be downloaded from our website. http://www.icsl.ucla.edu/~spapl/ Regards, Abeer On Tue, 24 May 2005, Automatic digest processor wrote: > There are 3 messages totalling 131 lines in this issue. > > Topics of the day: > > 1. Cochlear AGC attack/releases times? (3) > > ---------------------------------------------------------------------- > > Date: Mon, 23 May 2005 19:15:52 +0100 > From: "Richard H." <auditory(at)AUGMENTICS.COM> > Subject: Cochlear AGC attack/releases times? > > Hi, > > Does anyone know how the cochlear AGC can be modelled? > > Suppose a short tone burst hits the cochlear, how long does it take for the "gain" to be reduced? And then to recover? > > Are we talking 1 millisec or 1000 millisecs? [Or 0 millisecs i.e. the transfer function is more like an amplitude compander, without > any time aspect] > > And is this AGC very frequency specific - narrow nand, or perhaps critical band? > > Or does the cochear not really work like an electronic AGC [or compander] at all? > > kind regards, > > Richard > > ------------------------------ > > Date: Mon, 23 May 2005 14:56:41 -0400 > From: David Mountain <dcm(at)BU.EDU> > Subject: Re: Cochlear AGC attack/releases times? > > I'll start my answer with my engineer's hat on. I usually > usually refer to nonlinearities that are essentially instantaneous as > "compression" and nonlinearities that respond to some time average of the > signal as "automatic gain control" or AGC. > > The auditory system includes a lot more than the cochlea so the answer to > your question is not straight forward. If you are asking about the > nonlinearity in cochlear mechanics, I would say that the answer is that it > is essentially instantaneous (comparable to the rise time of the cochlear > filters) and hence refer to it as compression. Additional compression > takes place in the hair cells due to the nonlinear nature of the > transduction process. The synapse between the inner hair cell and the > auditory nerve fibers is best described as an AGC with two or more time > constants. There is a fast component to the gain change (adaptation in the > physiological jargon) that is the major component and has a time constant > in the 2-4 ms range. There is a slower component with a time constant in > the 10's of ms and there are other components that operate on time scales > over over 1 s. Additional adaptation takes place in the central nervous > system. > > The cochlear efferent system also can alter the gain. The primary efferent > effect build up with a time constant in the 50-100 ms range but here again > there are longer term effects as well. > > -------------------------------------------------------------------- > > David C. Mountain, Ph.D. > Professor of Biomedical Engineering > > Boston University > 44 Cummington St. > Boston, MA 02215 > > Email: dcm(at)bu.edu > Website: http://earlab.bu.edu/external/dcm/ > Phone: (617) 353-4343 > FAX: (617) 353-6766 > Office: ERB 413 > On Mon, 23 May 2005, Richard H. wrote: > > > Hi, > > > > Does anyone know how the cochlear AGC can be modelled? > > > > Suppose a short tone burst hits the cochlear, how long does it take for the "gain" to be reduced? And then to recover? > > > > Are we talking 1 millisec or 1000 millisecs? [Or 0 millisecs i.e. the transfer function is more like an amplitude compander, without > > any time aspect] > > > > And is this AGC very frequency specific - narrow nand, or perhaps critical band? > > > > Or does the cochear not really work like an electronic AGC [or compander] at all? > > > > kind regards, > > > > Richard > > > > > > ------------------------------ > > Date: Mon, 23 May 2005 22:51:54 +0200 > From: Martin Braun <nombraun(at)TELIA.COM> > Subject: Re: Cochlear AGC attack/releases times? > > Richard H. also asked: > > > And is this AGC very frequency specific - narrow nand, or perhaps critical > > band? > > Very frequency specific, yes. But this is level dependent. > > The critical band is an effect of processing in the auditory midbrain, which > is now also pointed out in the new review by Günter Ehret and Christoph > Schreiner. > > This book chapter can be downloaded for free as a sample chapter (398 KB): > > http://www.springeronline.com/sgw/cda/pageitems/document/cda_downloaddocument/0,11996,0-0-45-140972-0,00.pdf > > Book details: > > http://www.springeronline.com/sgw/cda/frontpage/0,11855,5-40109-22-34527392-0,00.html > > > Martin > > ---------------------------- > Martin Braun > Neuroscience of Music > S-671 95 Klässbol > Sweden > web site: http://w1.570.telia.com/~u57011259/index.htm > > ------------------------------ > > End of AUDITORY Digest - 20 May 2005 to 23 May 2005 (#2005-99) > ************************************************************** > >


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