Ron Parker wrote:
> 
> On Mon, 29 Jan 2001 22:52:47 -0600, David Fontaine wrote:
> >Aside from that, any mathematician will tell you the sample rate is
> >insufficient. The highest frequency a person can hear is around 20kHz. The
> >sample rate of a CD is 44kHz. It should be at least double that, 5x the
> >highest frequency. Think about it, you could be sampling near the zero
> >point every time.
> 
> Careful... I am a mathematician, though I don't practice anymore.  The
> Nyquist Theorem says a sampling frequency of twice the highest expected
> frequency is sufficient to recreate anything at or below that expected
> frequency.  Thus, CDs can accurately reproduce sounds at 22050 Hz and
> below.
> 
> It is important, though, to filter out anything above 22050 Hz before
> the digitizing stage, due to aliasing.  I suspect most professionals do
> so as a matter of course.

Careful... I am a "electronician", though I don't practice analog 
electronics anymore.  ;-)

This is one of the problems with CD players:

It's difficult to design good and cheap 
filters that has a very sharp cut-off 
frequency that lies right above this 
22 kHz frequency.

But if the sampling frequency had been chosen 
higher for CD's, then one could have used 
cheaper and more "relaxed" filters with higher 
cut off frequencies that would not make 
distortions to the sound (within the "audible"
range).


-- 
Best regards,

Tor Olav

mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html

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