Re: Cochlear AGC attack/release times

[Abeer Alwan <abeera@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxx>
> 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@xxxxxx>
> 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@xxxxxx
> 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@xxxxxxxxx>
> 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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