Re: An effect I've been working on (Jont Allen )

Subject: Re: An effect I've been working on
From:    Jont Allen  <jba(at)RESEARCH.ATT.COM>
Date:    Wed, 19 Mar 1997 15:14:06 -0500

Ludger Solbach wrote: > > Regis Rossi Alves Faria <regis(at)LSI.USP.BR> wrote: > > > The wavelet approach has several advantages over normal Fourier filtering > > since its filters have local support both in time and frequency, > > Due to the uncertainty principle this ain't possible for linear > time-frequency distributions. > > > making it > > easy to locate transients on some frequency bands. > > I would say, locating transients within single frequency bands is a thing > one should not do at all, because it's the nature of transients that their > spectrum is local in time and spread over the whole frequency axis. This is > why transient detectors should rather watch out for such a pattern in the > time-frequency plane to gain maximum time resolution. > See for intermediate results > of our work in this area. > > [...] > > Curiously (or not, that's what I want to learn) the sounds (1) and (2) are > > virtually the same, with differences under the threshold of perception for > > some levels. > > You did not say if you are using orthogonal or non-orthogonal wavelets. I > assume it's the latter, because in this case removing redundancy from the > coefficients would not have a very strong effect on the audible content > of the sound. In fact, this is even true for orthogonal wavelet expansions, > if you drop the right (i.e. small) coefficients. This is basically how > compression works. > > Best wishes, > > Ludger. > > --- > > ----------- Ludger Solbach, Distributed Systems Department ----------- > | Technical University of Hamburg-Harburg, Germany | > | e-mail: Solbach(at)TU-Harburg.d400.De, Tel.: +49-40-7718-3357 | > ----------------- ----------------- I very much agree with the above coments. Jont Allen

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