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From: doug@eris.berkeley.edu (Doug Merritt)
Newsgroups: comp.dsp
Subject: Re: Autocorrelation Pitch Tracker
Message-ID: <1991Apr15.181327.22527@agate.berkeley.edu>
Date: 15 Apr 91 18:13:27 GMT
References: <51258@apple.Apple.COM> <1991Apr13.013025.26614@agate.berkeley.edu> <51534@apple.Apple.COM>
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In article <51534@apple.Apple.COM> malcolm@Apple.COM (Malcolm Slaney) writes:
>	Early experiments by Savart (1830) indicated that a sense of pitch 
>	develops after only two cycles. Very brief tones are described as 
>	"clicks," but as the tones lengthen, the clicks take on a sense of 

This was interesting, thanks.

>Bad move.  First the signals I am talking about were synthesized in the
>time domain...Mr. Fourier wasn't involved.
>
>Fourier transforms are not good because the ear is non-linear.  Fourier 
>theory is great for linear systems but the ear is far from linear.

I understand, I've read your "Lyon's Cochlea Model" paper (quite
interesting, BTW). But that's not the point. You're talking about the
ear and perception, I meant to talk about the sound itself.

What I meant (and didn't say very well) is that you can always look at
the Fourier domain for information about the sound itself; it makes no
difference whether it was synthesized in that domain or not (as I'm
sure you know). And what I predict you'll find is that the result is
very close to what you would see for a single cycle of a square wave,
which means that it would take only a small perturbation to transform
the one into the other.

And in fact, the nonlinear characteristics of the ear may well perform
exactly such a perturbation. So far from being irrelevent, looking at
this in the Fourier domain may explain *why* the nonlinearity of the
ear produces perception of a click rather than a pitch.

Fair enough?
	Doug
-- 
--
Doug Merritt		doug@eris.berkeley.edu (ucbvax!eris!doug)
		or	uunet.uu.net!crossck!dougm