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Re: An effect I've been working on

I'd like to ask Mr. Faria to clarify a few details of his interesting

Regis Rossi A. Faria wrote [control character garbage edited out!]:

> The wavelet approach has several advantages over normal Fourier filtering
> since its filters have local support both in time and frequency, making it
> easy to locate transients on some frequency bands.

When you say "normal Fourier filtering" I assume you mean (1) a method such as
the Phase Vocoder, where filters are typically allocated one-per-harmonic
of an estimated fundamental, but not (2) a method such as McCauley&Quatieri
where an arbitrary number of  filters are allocated dynamically according to
the signal.  Is that true?

Transients consist of non-harmonic information, and method (1) smears
non-harmonic information over several bands.  Then is what you are
saying that wavelets more accurately assigns them to appropriate
frequency bands?

> Another advantage
> of wavelet filtering is its property of separating bands with quality
> factor (Q) constant over the frequency axis, in a way the basilar membrane
> in
> the inner ear also resolves frequency bands. This property makes wavelets
> closer to ear's acoustic pre-processing, on stages before neural
> processing.

Is the nature of the advantage that (1) a person examining wavelet
analysis output is observing "how the ear experiences the sound", or (2)
the method is more economical by ignoring detail that goes beyond
the resolving properties of the ear, or (3) both?

>  (1) the result of mixing the original tone with a reconstruction of the sound
> from its wavelet coefficients (obtained in the forward transform) taking only
> the coefficients in level n and "clamping" other coefficients (from all other
> levels) to zero value (this is reconstructing only the level n and mixing it
> to the original sound).

Can you clarify what "in level n" means?  Do you mean "only those
coefficients whose value is n or greater?

Gregory J. Sandell, Research Associate, sandell@sparky.parmly.luc.edu
Parmly Hearing Institute, Loyola University Chicago
6525 N. Sheridan Chicago IL 60626 USA voice:773-508-3976 FAX:773-508-2719
WWW: http://www.parmly.luc.edu/sandell/