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Re: AUDITORY Digest - 30 Oct 2003 to 6 Nov 2003 (#2003-183)
- To: AUDITORY@xxxxxxxxxxxxxxx
- Subject: Re: AUDITORY Digest - 30 Oct 2003 to 6 Nov 2003 (#2003-183)
- From: Jont Allen <jba@xxxxxxxxxxxxxxxxxx>
- Date: Fri, 7 Nov 2003 10:02:08 -0600
- Delivery-date: Fri Nov 7 11:11:31 2003
- References: <200311070501.hA751VNB003509@prion.mcgill.ca>
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- Sender: AUDITORY Research in Auditory Perception <AUDITORY@xxxxxxxxxxxxxxx>
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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,
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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@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 = +/-
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.
Hafiz M.A. Malik,
Multimedia Systems LAB.
Elecrical & Computer Engineering Dept,
UIC, Chicago, IL, 60607
End of AUDITORY Digest - 30 Oct 2003 to 6 Nov 2003 (#2003-183)