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Re: digital filter design

I've had good results using the "embedded all-pass filter" scheme for this
sort of thing.  The first reference is:

P.A. Regalia and S.K. Mitra (1987), "Tunable Digital Frequency Response
Equalization Filters," IEEE Trans. Acoustics Speech Signal Processing,
ASSP-35(1), pp. 118-120.  (Separate coefficients control boost/cut, center
frequency, and bandwidth)

There are also a few useful descriptions of similar filters with improved
attributes among the Audio Engineering Society preprints.

R.C. Maher (1995), "Tunable Bandpass Filters in Music Synthesis," Proc. 99th
AES Convention, New York, preprint 4098. (Use of Regalia-Mitra for vocal
formants and other purposes)

U. Zolzer and T. Boltze (1995), "Parametric Digital Filter Structures,"
Proc. 99th AES Convention, New York, preprint 4099. (Better decoupling
between the control coefficients)

S.J. Orfanidis (1996), "Digital Parametric Equalizer Design with Prescribed
Nyquist-Frequency Gain," Proc. 101st AES Convention, Los Angeles, preprint
4361. (Good match to analog prototype response; includes Matlab code;
similar to presentation in Orfanidis' textbook)

Best wishes,
Rob Maher

> -----Original Message-----
> From: AUDITORY Research in Auditory Perception
> [mailto:AUDITORY@xxxxxxxxxxxxxxx] On Behalf Of beaucham
> Sent: Saturday, January 29, 2005 4:39 PM
> To: AUDITORY@xxxxxxxxxxxxxxx
> Subject: digital filter design
> Does someone have a good answer for this student?
> Jim Beauchamp
> Original message:
> > From: Farsheed <hamidito@xxxxxxxx>
> > Date: Sat, 29 Jan 2005 16:42:48 -0500
> > To: beaucham <beaucham@xxxxxxxxxxxxxxxxxxxxxx>
> > Subject: filter design?
> >
> > For my senior design project we are working on making a
> > touchpad filter equalizer, so that you can boost or attenuate
> > frequencies on the fly using your finger.  My question for you
> > is, would you recommend any texts to read regarding choosing a
> > good DSP filter for such a design?  We would like to be able
> > to control Q, boost/attenuation, and frequency for a
> > bandstop/bandpass filter directly, using one algorithm only.
> >
> > Thank you,
> > Farsheed
> >
> > ***************************************
> > Farsheed Hamidi-Toosi
> > Student, University of Illinois at Urbana-Champaign
> > Webpage: http://www.midnightparking.com