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Re: Place-based pitch


There are various sorts of diplacusis:

"Diplacusis binauralis" - when binaural sounds seem to be different due to our cochlea being physically frequency "misaligned" with
the respect to the other ... the brain can "fuse" a certain amount of misaligment ... but not over a semitone. The misalignmemnt can
either be due to "manufacturing tolerances" or due to physical distortion from Menieres etc. The fusing process is mandatory because
the 2 cochleas CAN grow slightly differently even in healthy people.

"Diplacusis echotica" - when one sound is reheard after a time delay ... suspected to be due to either brain issues, or to a SAW
(surface acoustic wave) echo in the TM (Tectorial Membrane) of the cochlea.

Another form of diplacusis is when a monaural tone is split into TWO tones because of major nonlinearities in the cochlea.

Hope that helps ...


----- Original Message -----
From: "Al Bregman" <al.bregman@mcgill.ca>
To: <AUDITORY@lists.mcgill.ca>
Sent: Wednesday, March 24, 2004 10:26 PM
Subject: Place-based pitch

> Dear list,
> There is a phenomenon that suggests a contribution of place information to
> pitch at all frequencies: the phenomenon of diplacusis, the hearing of
> different pitches for the same sound at the two ears (when presented to only
> one ear at a time).  It is hard to imagine how a temporal mechanism could
> produce such an effect, but if the two cochleas were slightly different
> anatomically, one could see how this phenomenon could occur.  The idea is
> that place plays a secondary role at all frequencies, perhaps choosing
> between temporal conclusions that are close to one another in probability
> based on the temporal mechanism (e.g., octave differences), but can
> influence the pitches to be slightly "off" when the two cochleas have
> different topologies.
> Al
> -----------------------------------------------------------
> Albert S. Bregman, Emeritus Professor
> Dept. of Psychology, McGill University
> 1205 Docteur Penfield Ave.
> Montreal, QC  Canada  H3A 1B1
> Office Tel: (514) 398-6103, Fax -4896
> E-mail: al.bregman@mcgill.ca
> -----------------------------------------------------------

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