critical band vocoder (beaucham )

Subject: critical band vocoder
From:    beaucham  <beaucham@xxxxxxxx>
Date:    Wed, 17 May 2006 15:07:02 -0500

For many years vocoders were used for data reduction of speech signals.
A vocoder separates the input signal into consecutive bands, codes the
band outputs, and then transmits the coded information to a receiver
for resynthesis. An early model of Bell Lab's vocoder used 20
uniform-width bands below 3000 Hz and 10 log-spaced bands above 3000
Hz, extending to 7500 Hz.

Recently, mel-frequency cepstral coefficients have been popular for
speech recognition. Mel frequency spacing is approximately proportional
to critical-band frequency spacing. My question is: Has anyone designed
and tested a vocoder using critical-band spacing of the filters?

Jim Beauchamp
Univ. of Illinois at Urbana-Champaign