[music-dsp] Killer speech noise reduction?

James Chandler Jr. jchandjr at bellsouth.net
Mon Jun 24 13:31:53 EDT 2002

A curiosity question--

Does anyone know of programs that can enhance speech intelligibility that is
at or below the noise level?

Have heard that FBI and CIA type organizations have really effective speech
extraction software, but maybe that is just rumor.

Lawyers occasionally bring me "really important" evidence microcassette
tapes that are hopelessly buried in noise. Said lawyers are routinely
saddened and alarmed when I can't recover their important evidence (though
these guys have not learned their lesson yet and made serious efforts to
improve their surveillance recording techniques (GRIN)).

Have used several common spectral noise reduction programs. "Noise signature
based" spectral noise reduction works fabulous if the signal is at least a
little higher than the noise level.

But commercial spectral noise reduction programs seem completely ineffective
as soon as the noise is as loud as the signal level. Once the S/N ratio gets
really bad, spectral noise reduction seems to make speech intelligibility
worse rather than better. Not only does the speech remain unintellible, but
it also sounds like a robotic ring-modulated special effect.

Are any specialized noise-reduction programs available, customized for
improving speech intelligibility on really noisy recordings?


James Chandler Jr.

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