> You can't filter out noise with DSP.  By definition, it's noise... there's
> no way to distinguish the noise from the desired signal.  The way to
> eliminate noise is to not let it in to begin with. :)

This is true when you know nothing about the characteristics of the noise.
However, if the noise has some characteristic that distinguishes itself from
the real signal, it is possible, in theory, to reduce or eliminate that
noise.  One of the simplest distinguising characteristics is frequency.
Noise with frequency outside the desired signals frequency range can be
filtered.  For example, it is easy to eliminate (greatly attenuate actually)
50KHz or 5Hz noise from an audio channel.

I do agree with the audio engineer though.  The best defense against noise
is to not allow it in to begin with.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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