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mfcc filters gain

Dear list,
In the Malcom Slaney's Matlab implementation of mel frequency cepstral
coefficients, triangular filters are normalized "so that each filter has
weight". Parsing some papers dealing with mfcc, I noticed that most of
authors does not mention this normalization step (a few of them do, but
without explanation).
I am wondering what does this normalization correspond to. If I am
correct, and if triangular filters were supposed to approximate critical
band filtering, they all should have the same unit height, just as third
octave, or Patterson's gammatone filterbank. Am I wrong ?

I am also wondering if some work has already be done to improve
mfcc-like processing. As it is suggested in [1], Moore's ERB scale or
Bark scale seems to be more appropriated than the mel scale, and
gammatone filterbank should be much more accurate (even if probably more
computationaly expensive) than a triangular filterbank ?


[1] M. D. Skoweonski and J. G. Harris
"Improving the filterbank of a classic speech feature extraction algorithm"
IEEE Int. Symp. on Circuits and Systems, Bangkok, Thailand, 2003

Guillaume Lemaitre, Ph.D.
Post-doctoral fellow
Project-team REVES (REndering and Virtual Environments with Sounds)
INRIA Sophia-Antipolis                 tel: (+33) (0)4 92 38 50 83
2004 route des Lucioles               fax: (+33) (0)4 92 38 50 30
BP 93, F-06902 Sophia-Antipolis, France