Subject:Re: AUDITORY Digest - 30 Oct 2003 to 6 Nov 2003 (#2003-183)From:Jont Allen <jba(at)auditorymodels.org>Date:Fri, 7 Nov 2003 10:02:08 -0600Dear Hafiz An all-pass filter is only flat if the entire impulse response is processed. When you take a finite window of a filtered stimulus, this rule is broken. In a sense, this is equivalent to taking a piece of the impulse response a(t) and expecting it to have a constant spectrum. Such a piece of a(t) will not be flat. The longer you make a(t), the worse the problem becomes. Hope this helps, Jont Automatic digest processor wrote: > There is one message totalling 46 lines in this issue. > > Topics of the day: > > 1. why all-pass filter introducing inaudiable magnitude distortion > > ---------------------------------------------------------------------- > > Date: Thu, 6 Nov 2003 03:20:49 -0600 > From: hmalik1 <hmalik1(at)UIC.EDU> > Subject: why all-pass filter introducing inaudiable magnitude distortion > > Dear Experts and Friends, > I need guidance for understanding the theory behind distortion(inaudible) > introduced by all-pass filter..... > > I'm using 10-14th order all-pass filter(cascade form) with complex pole-zero > pair close to unit circle i.e.( pole at .9 and zero at 1/.9 and theta = +/- > phi). > when a frame of 128-256 audio samples passed through the all-pass filter and > power-spectrum of the output frame is estimated using > a) Moving Average signal model > b) Autoregressive signal model > > this is observed that all-pass filter has introduced a local minima in the > estimated power spectrum at frequency = phi for both models, but minima in > model (a) is stronger than model (b). > > this distortion introduced by all-pass filter become more stronger as > pole-zero pair moves close to unit circle or by increasing the order of the > filter used. (simulation is done using MatLab) > > I would appreciate any suggestion or reference that'll help me to understand. > this behavior . > > thanks in advance. > > Regards > > Hafiz M.A. Malik, > Multimedia Systems LAB. > Elecrical & Computer Engineering Dept, > UIC, Chicago, IL, 60607 > 1(312)4135499 > 1(312)9966007 > hmalik1(at)uic.edu > hmalik(at)uic.edu > http//multimedia.ece.uic.edu/aslam > > ------------------------------ > > End of AUDITORY Digest - 30 Oct 2003 to 6 Nov 2003 (#2003-183) > ************************************************************** > >

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