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From: wjm@whuxj.UUCP (MITCHELL)
Newsgroups: net.audio
Subject: Re: Square Wave Response
Message-ID: <270@whuxj.UUCP>
Date: Tue, 12-Jun-84 11:22:49 EDT
Article-I.D.: whuxj.270
Posted: Tue Jun 12 11:22:49 1984
Date-Received: Wed, 13-Jun-84 00:48:03 EDT
Organization: Bell Communications Research, Inc.
Lines: 25


Yes, one of the problems of choosing a 44.1 KHz sampling rate for CD's is that
no frequency above 22.05 KHz will be reproduced.  Since a square wave is
composed of all odd harmonics of the given fundamental frequency, the square
wave response for CD players will not look as "good" as that from analog
components that can reproduce 22KHz+ frequencies (even with 5 or 10 dB of
loss compared to response at 1KHz or so).
What does this mean???
1.  As I've said before, I feel the 44.1 KHz sampling rate is too low - I
believe that there is useful musical information in the top octave of music
(10-20 KHz) and that some of the harmonics on percussion instruments go as high
as 25KHz.  Personally, I can hear 25 KHz (ultrasonic alarms drive me bats) and
there is information there.  While I realise the need for a digital standard
if CD is to be a workable system, I fear we may have been locked into a
standard that limits us as recording technology improves.  This is the same
problem that happened with the NTSC TV standard, and is now coming back to
bite us when we want to develop HDTV.
2.  The square wave test is very useful, since it does give some feel for
the high frequency response of the system.
3.  Even though no CD player can properly handle a 20 KHz square wave, the
test results provide valuable information about the effects produced by the
filters in the unit, by examining the amount of ringing that takes place at
the corners of the square wave.
Regards,
Bill Mitchell (whuxj!wjm)