[music-dsp] Random Noise Reduction

Al Clark aclark at danvillesignal.com
Thu Jan 15 07:31:01 EST 2004

At 08:33 AM 1/15/2004, Joshua Scholar wrote:

>----- Original Message -----
>From: "Yaakov Stein" <yaakov_s at rad.com>
>To: <music-dsp at shoko.calarts.edu>
>Sent: Wednesday, January 14, 2004 11:34 PM
>Subject: RE: [music-dsp] Random Noise Reduction
> > If the noise is stationary and the signal is not always present,
> > then spectral subtraction might help (but destroys phase).
>Is spectral subtraction just taking short time (possibly overlapping) FFTs
>and zeroing coefficients below a threshold?

Not quite. You use some form of method to determine which blocks have both 
noise and desired signals and which blocks represent only noise. The noise 
spectrums are used as the reference to subtract from the composite blocks.

  There are tricks that reduce certain artifacts such as musical tones 
caused by the fact that the noise is not really stationary.

Al Clark
Danville Signal Processing, Inc.
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com

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