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Re: Non-linear additions to linear models. (was On pitch and periodicity (was "correction to post"))


I agree with you ... however I think we are a long way off having
physiological models explain high level processes ...

There has been a considerable amount of work into physiological models
of hearing. Such models don't necessarily assume anything other then a
travelling wave in the Cochlea. Other models don't believe in the
passive travelling wave ... all of them however have some form of
resonance ... and this is tuned in some way ... but as you say, not a FT
type of tuning.

Once you leave the realm of psychoacoustics, you are so low level, that
you are no longer concerned with high level 'illusions'. Before you can
even start to model these high level illusions, you must model the
physiological elements of the Cochlea.

As such when you are on the physiological level you are now worried
about things like two tone suppression (not masking), emissions,
distortion products and so on. Depending how you go about modelling, you
may also me modelling how the membranes and cells move in the inner ear.

People do take elements of the physiological models and simplify them as
their basis for high level psychoacoustics work ... this is where the
gammatone and gammachirp physiological basis comes from ... Richard Lyon
- as another example - has recently re-worked his physiological bases
for his high level CASA system ...


On Mon, 2011-08-08 at 10:52 -0400, John Bates wrote:
> Hello Randy,
> I think you are totally correct in your belief that a new paradigm for
> auditory perception is needed.
> This thread, which began with a question on how auditory illusions
> might affect hearing aid operation, has missed the main point. In my 
> estimation
> the greatest auditory illusion of all is that the ear operates by spectrum
> analysis.
> To Ohm and Helmhotz the Fourier transform was a mathematical delicacy that
> they could use to justify any observation of tonal perception. Since then,
> researchers have followed their lead by cherry-picking "ineresting problems"
> and proposing solutions involving impressive Fourierian mathematics but
> always ending with ineffective, qualified results. There is now not even the
> slightest hint of an applicable auditory model.
> The reason for this stalemate is that there has been no complete system
> analysis to establish the functional and physical requirements for a way to 
> extract
> meaning from environmental sounds.  Why else could it be that all animals
> have some kind of sonic perception? And, in terms of biological survival,
> speech and music would be at the bottom of the list. Yet, with us, these 
> are,
> and have been, the primary goals of auditory research.
> An analysis of auditory requirements should reveal that there is no physical
> way that a spectrum analyzer can respond to the temporal, spatial, and
> physiological requirements that are easily accomplished by the ear-brain
> system. Given that our ears do things that cannot be done in the Fourier
> paradigm, it is only logical that a different paradigm can be discovered:
> one that can explain those baffling psychophysical illusions without having
> to make wild assumptions.
> Good luck,
> John Bates
> ----- Original Message ----- 
> From: "Ranjit Randhawa" <rsran@xxxxxxxxxxx>
> To: <AUDITORY@xxxxxxxxxxxxxxx>
> Sent: Sunday, August 07, 2011 11:50 AM
> Subject: Re: Non-linear additions to linear models. (was On pitch and
> periodicity (was "correction to post"))
> > Hi Dick,
> > My last observation is on your suggestion of adding non-linearity to some
> > linear model to cover what some people may call illusions. As an tran
> > aside, I believe Helmholtz was forced to add in the quadratic function
> > only because experimentalists (Seebeck I believe) were breathing down his
> > neck proving the existence of the missing fundamental problem. I would
> > have to strongly disagree with some of the conclusions reached from such
> > quadratic and cubic  expansions. In my opinion, I think when people say
> > that a new paradigm was needed I assumed that it meant a totally new
> > approach to signal analysis that did not necessarily adhere to any
> > assumptions of linearity. Take for example a system based on rate of
> > change of signal  energy, it could right away explain some minor
> > psycho-acoustic phenomenon associated with changes in static pressure or
> > that tricky bias term that comes up when one is analyzing sounds like
> > speech. But as I am sure you would point out, much more would be needed
> > before such a statement could have any validity as the basis for a system
> > theory. I agree. On that note, I believe that till some such system is
> > offered for review, non-linear additions to linear models will have to do
> > for rest of us who are appalled by the associated mathematics. Regards,
> > Randy Randhawa
> >
> > On 8/4/2011 1:42 PM, Richard F. Lyon wrote:
> >> Randy,
> >>
> >> I'll be the first to agree that linear systems theory is sometimes
> >> stretched beyond where it makes sense, and that you need to use nonlinear
> >> descriptions to describe pitch perception and most other aspects of
> >> hearing, and more so when you get up to cognitive levels.
> >>
> >> I'm sorry to hear that you "gave up on linear systems", because I don't
> >> think it's possible to do much sensible with nonlinear systems when you
> >> don't have linear systems as a solid base to build on. Certainly at the
> >> level of HRFTs, cochlear function, and pitch perception models, a solid
> >> understanding of linear systems theory is in indispensible prerequisite.
> >> Then, the nonlinear modifications needed to make better models will seem
> >> less "tortured".
> >>
> >> Dick
> >>
> >> At 10:33 AM -0400 8/4/11, Ranjit Randhawa wrote:
> >>> Dear Dick,
> >>> While linear system theories seem to work reasonably well with
> >>> mechanical systems, I believe they fail when applied to Biological
> >>> systems. Consider that even Helmoholtz had to appeal to non-linear
> >>> processes (never really described) in the auditory system to account for
> >>> the "missing fundamental" and "combination tones". Both of these
> >>> psycho-acoustical phenomenon have been well established and explanations
> >>> for pitch perception are either spectral based or time based with some
> >>> throwing in learning and cognition to avoid having to make the harder
> >>> decision that maybe this field needs a new paradigm. This new paradigm
> >>> should be able to provide a better model that explains frequency
> >>> (sound!) analysis in a fashion such that the nothing is missing and
> >>> parameter values can be calculated to explain pitch salience, a subject
> >>> that seems to be never discussed in pitch perception models.
> >>> Furthermore, such a new approach should also be able to explain why the
> >>> cochlear is the shape it is, which as far as I can see has never been
> >>> touched upon by existing signal processing methods. Finally, are these
> >>> missing components "illusions" that are filled in so to speak by our
> >>> higher level cognitive capabilities? It is remarkable that this so
> >>> called filling in process is as robust as it is, to  be more or less
> >>> common to everyone, and therefore one wonders if all the other illusions
> >>> are really not illusions but may have a perfectly good basis for their
> >>> existence. If they were "illusions" one would expect a fair amount of
> >>> variation in the psycho-acoustic experimental results I would think.
> >>> I myself gave up on linear systems early in my study of this field and
> >>> have felt that other systems, e.g. switching, may offer a better future
> >>> explanatory capability, especially when it comes to showing some
> >>> commonality of signal processing between the visual and the auditory
> >>> system. To this end, I am quite happy to accept that I do not consider
> >>> myself an expert in linear system theory.
> >>> Regards,
> >>> Randy Randhawa
> >>>
> >>>