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Re: mp3 and the perceptual coding demo

A related demo is to subtract the spectrum of the mp3 coded sound from the original, and do an inverse fft, to show all the sounds that they are not "hearing."  Werner Deutsch used to do this with symphonic recordings and joke that this showed that most of the musicians in the symphony were not needed.
Brian Gygi, Ph.D.
Speech and Hearing Research
Veterans Affairs Northern California Health Care System
150 Muir Road
Martinez, CA 94553
(925) 372-2000 x5653
-----Original Message-----
From: Laszlo Toth [mailto:tothl@xxxxxxxxxxxxxxx]
Sent: Thursday, March 25, 2010 05:37 AM
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: Re: mp3 and the perceptual coding

On Thu, 25 Mar 2010, Massimo Grassi wrote: > I would like to convince to my students that psychophysics can (seldom) > be useful. For this reason, I want to talk about mp3 and perceptual coding. I usually do the following demonstration: take a speech sample, compress it with an mp3 codec at the highest possible compression rate, then decompress it and display the spectrogram of the original and the processed signal. The spectral valleys are wiped out, while there is minimal perceptual difference. I think this quite convincingly demonstrates that masking indeed works, and that the industry can make use of the results of psychophysics. Laszlo Toth Hungarian Academy of Sciences * Research Group on Artificial Intelligence * "Failure only begins e-mail: tothl@xxxxxxxxxxxxxxx * when you stop trying" http://www.inf.u-szeged.hu/~tothl *