Re: SoundSmith on a PC???

[supertimer@aol.com (Supertimer)]

CUTjefbla@bconnex.net (Jeff Blakeney) write:

>The low pass filter is to kill all the high frequencies that we humans
>can't hear.  If they were left in the audio output they would just
>result in distorting the sound a bit.  Much better to remove them to
>get the cleanest possible sound.

That's what I've been trying to tell Mitch.

If you think about it, CD quality is 44.1Khz not because it
takes 44.1Khz is the highest frequency we can hear,
but because that 44.1Khz refers to sampling rate.

Sampling rate and frequency are not the same thing, even
though they both use hertz as a measure.

The highest frequency that's recorded is half of the
sampling rate.

Thus, the maximum frequency that a CD captures is
22Khz.  That, incidentally, is about the peak of human
hearing.

On a 44.1Khz sample, the frequencies above 22Khz
are caused by sampling distortion and that's what a
low pass filter is supposed to remove.

Mitch seems to have been thinking that PC sound
is better because it can reproduce 44.1Khz
FREQUENCIES at a sampling rate of 44.1Khz, which
is, of course, completely wrong.  The top frequency
that can be reproduced using that sampling rate
would be 22Khz, which would fall below a 26Khz
low pass filter if it were present.

I really blame the audio CD industry for this confusion.
Back in the early days of CD audio, CD manufacturers
use to advertise frequency response and correctly
listed 22Khz as top frequency.  Then someone got the
bright idea of advertising sampling rate.  They could
say "we got 44.1Khz sound" when actually refering to
sampling rate.  They changed nothing but could appear
to give twice the sound (ignoring the fact that people
can't hear above the 22k's).  And thus the great confusion
started.