Re: Gaussian vs uniform noise audibility

[Israel Nelken <israel@xxxxxxxxxxxxx>]

       I think that one has to distinguish between the spectral representation
as a tool for describing signals on the one hand, and the question of
whether the ear is a fourier analyser. For the second question, I think
everyone's answer (certainly mine) is strictly speaking no - although
spectrograms are reasonable 0th order approximations to what we hear...
       For the first question, spectral representation is mathematically
'true' (within the obvious limits of the application of a mathematical
theory to real life). Furthermore, for real-life signals the inverse
fourier transform is equal to the original function almost everywhere,
so that any operation on the signal that is formulated in terms of its
temporal waveform can be also formulated in terms of the fourier
spectrum (amplitdue AND phase). Some of these operations may be vastly
more complicated when described in the spectral domain, but this does
not invalidate the above statement. In these terms, there's a full
equivalence between time and spectral processing.
       Finally, there's the question of the usefullness of the spectral
description of random processes, which is yet a somewhat different
question. The independence of the spectral components of a gaussian
process is a mathematical result, independent of the physiology of
hearing, but it has consequences for hearing. Since we are sensitive to
spectral correlations, non-gaussianity can be detectable by such
sensitivity. This doesn't assume anything about the use of Fourier
transforms in the ear!
       Eli


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Israel Nelken
Dept. of Neurobiology
The Alexander Silberman Institute of Life Sciences
Edmond Safra Campus, Givat Ram    | Tel: Int-972-2-6584229
Hebrew University                 | Fax: Int-972-2-6586077
Jerusalem 91904, ISRAEL           | Email: israel@md.huji.ac.il
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