Re: Is there considerable phase locking up to 6 kHz?

["Richard F. Lyon" <DickLyon@xxxxxxx>]

Title: Re: Is there considerable phase locking up to 6 kHz?

At 9:53 AM +0100 03/18/2004, Eckard Blumschein wrote:

> However, we all should be wary of
> thoughtlessly using notions like spectrum
> and temporal fine structure.

I'm glad that we have that point of agreement.

> Already the fundamentally inappropriate
> traditional spectrogram illustrates
> that the iteration of a segment of noise without any spectral
> profile
> introduces an audible spectral signature. Of course, the FCT-based
> natural
> spectrogram shows a more realistic picture of firing pattern in
> the
> auditory nerve. I remind those who do not trust in FCT, because
> they
> wrongly put it in the drawer of an exotic mathematical idea while
> it
> actually replaces FT, of the need to define what we are talking about
> if we
> are using terms like spectral
> component.

I'm trying to decide whether that comment is directed at me.  Certainly I've always been very careful about concepts such as spectral components, as I believe the such frequency-domain concepts often force thinking into wrong directions.  I also don't regard Fourier Cosine Transforms as any more exotic than other mathematical transforms.  But I do mistrust them as auditory models.

> Martin Braun is certainly correct in
> that, there are at least two main
> streams of auditory information within each CN. However, he
> apparently
> ignores tonotopy as long as he doesn't follow my suggestion that place
> code
> is the best base for subsequent temporal processing. For more than
> a
> century, Fourier analysis and place code were considered the basis
> of
> hearing and of related audio technology because alternative temporal
> models
> failed.

Here we have a different view of the impact of the Fourier analysis approach and place code on the historical development of auditory theory.  I'm more aligned with a quote that I heard attributed to Georg von Békésy:  "Dehydrated cats and the application of Fourier analysis to problems in hearing become more and more a handicap for progress in hearing research."

As far as I know, temporal models have succeeded more than failed (that is, temporal models of processing in and beyond the cochlea, not to be confused with temporal processing of raw sound waveforms).  Spectral models, while widely used, often run into limitations that make them "fail".

> Why not seriously dealing with an unseen
> mathematically correct and
> physiologically plausible model that unites function of cochlea and
> brain
> in a somewhat strange hidden manner which is already known as
> cepstral
> analysis? It also may elucidate why different codes contribute to a
> unitary
> pitch.

Cepstral analysis is fine as far as it goes.  But it is rather limiting, as a mathematical framework that stops short of describing what's going on in detail, essentially ignoring temporal fine structure on the auditory nerve.

> I do not appreciate glossing over FCT as
> a red herring since such emotional
> arguments are difficult to falsify. Nonetheless, I would hope that
> expert
> listeners confirm or deny the putative 400/800 Hz confusion. So far, I
> am
> only aware of a plausible 50/100 Hz confusion in case of iterated
> noise
> segments with alternating polarity
> inversion (Warren & Wrightson 1981).

OK, this part I'm certain is directed at me, since I mentioned red herrings.  My comment was not directed at the FCT itself, which is a perfectly fine transform, but rather to the idea that if you use it then you can ignore questions of temporal fine structure.  Specifically, what I said quoted your assertion, this way ...the idea that "FCT is the only realistic cochlear transform" is just a mathematician trying to force a biological system to be something he can analyze.'  I apologize for putting it in such personal terms.

Dick

> Eckard Blumschein