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From: ender@mtuxo.UUCP (e.ayanoglu)
Newsgroups: rec.aviation,sci.electronics,rec.audio
Subject: Re: Noise-cancelling microphone
Message-ID: <2796@mtuxo.UUCP>
Date: Wed, 3-Jun-87 02:56:09 EDT
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Posted: Wed Jun  3 02:56:09 1987
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> Regarding noise-cancelling speakers and mikes, there was an article in the
> British magazine "New Scientist" a while back about the use of "anti-noise"
> near large sources of acoustic noise...

This is an application of a well-known method of noise cancellation, the
Least Mean Squares (LMS) algorithm. See, for example,

Widrow et al., ``Adaptive Noise Cancelling: Principles and Applications,''
Proc. IEEE, Vol. 63, pp. 1692-1716, 1975,

or

Widrow and Stearns, ``Adaptive Signal Processing,'' Prentice-Hall, 
Englewood Cliffs, NJ, 1985.

As pointed by others, the method does not work as well when the noise
spectrum widens.
-- 
Ender Ayanoglu  	   ..!ihnp4!mtuxo!ender 		 (201) 957-3734