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Re: Is correlation any good for pitch perception?

Dear Dmitry,

My understanding recently was that autocorrelation may not be the best
measure of periodicity pitch because it performs too well. Papers in
1996 by Cariani and Delgutte showed that pitch salience was
overestimated for unresolved harmonics. For most everything else the
model worked quite well. Note that these studies were a
neurophysiological test of Licklider's original autocorrelation idea,
where he gave a basic schematic of how autocorrelation might be
implemented in a neural system. I recently heard a talk where Delgutte
said that he was moving more in the direction of Shamma's earlier work
based on spatio-temporal representations of auditory signals.

I did read your earlier ICASSP paper and took a look at the Matlab
files on the website. Unfortunately, the code is not available for
viewing and the ICASSP paper lacks some detail. I, for one, was really
intrigued by your idea, so I kindly suggest that you write a longer
paper and submit it to JASA. The editors there are always interested
in pitch, as are the reviewers and readers. (I believe that last year
Pierre Divenyi proposed this as well.)

You also mentioned that a basic analog system could implement your
idea. Including that in the JASA paper would be great too. It would be
helpful to see that so we could determine which neural center, if any,
might be able to implement your idea.

Best wishes,


Craig Atencio
Department of Bioengineering UCSF/UCB
W.M. Keck Center for Integrative Neuroscience UCSF
513 Parnassus Ave.
HSE 834, Box 0732
San Francisco, CA, 94143-0732, USA
office: 415-476-1762 (UCSF)
cell: 510-708-6346

----- Original Message -----
From: "Dmitry Terez" <terez@SOUNDMATHTECH.COM>
Sent: Friday, January 16, 2004 1:21 PM
Subject: Is correlation any good for pitch perception?

> Dear Auditory List Members,
> I would like to convey some thoughts on the much-discussed subject
> how human auditory system can use autocorrelation analysis for pitch
> perception.
> Are you really sure that our auditory system uses autocorrelation at
> all?
> Has anybody seen it really happening in the brain? As far as I
> understand
> (Forgive me if I am wrong), beyond the cochlea not much is really
> known about the real mechanism behind an exceptionally robust human
> pitch perception. I am not an auditory scientist, but it just looks
> to me that the correct answer on your part is “We do not know”.
> I do think that correlation function has two fatal drawbacks, as far
> as pitch detection is concerned  (I am talking about a classical
>  or cross-correlation function of a signal, that is, a multiply-and-
> add type of operation, as defined in any textbook on signal
> processing)
> The first fatal drawback of correlation is the abundance of
> peaks due to complex harmonic structure of a signal. For some real
> signals we are dealing with every day, such as speech, the secondary
> peaks in the correlation function due to speech formants (vocal
> resonances) are sometimes about the same height as the main peaks
> to signal periodicity (pitch).
> The second fatal drawback of correlation is its pitch strength
> (salience) property for simple and complex tones. In other words,
> main peaks in the correlation function computed for, e.g. a simple
> sine wave, are too wide. Meanwhile, I would expect a simple tone to
> cause the same or even stronger pitch sensation than a complex tone
> with the same fundamental frequency.
> I think that it would be strange if evolution resulted in such a
> suboptimal mechanism of perceiving sound periodicity.
> As some of you may know, recently we introduced a new revolutionary
> concept of pitch detection. It has nothing to do with correlation
> (although one can see some similarity) or spectrum of a signal. It
> basically based on “unfolding” a scalar signal in several
dimensions –
>  a concept of signal “embedding”, as it is called in nonlinear and
> chaotic signal processing.
> The ICASSP paper and the Matlab demo are available from
> http://www.soundmathtech.com/pitch
> You can also read our US patent application publication No.
> 20030088401
> at http://www.uspto.gov/patft
> Although a purely digital implementation is described, I can build a
> simple analog electro-mechanical device (basically a mechanical part
> followed by a two-dimensional grid of “neurons” for projecting an
> output) that is based on the same principle and is exceptionally
> robust at detecting pitch.
> My question is: Can our auditory system use this type of processing
> for pitch perception?
> Is it possible to find some mechanism that can perform this kind of
> processing, perhaps between the cochlea and the brain?
> I do not expect a quick answer. Please, take your time, maybe next
> years …
> Also, I would like to add that although words like “chaos
> theory”, “phase space” or “signal embedding” might seem not relevant
> to your research on pitch perception, they are now, in fact. This is
> an entirely new game…
> Best Regards,
> Dmitry E. Terez, Ph.D.
> SoundMath Technologies, LLC
> P.O. Box 846
> Cherry Hill, New Jersey, 08003
> e-mail: dterez AT soundmathtech.com