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From: briand@tekig1.UUCP (Brian Diehm)
Newsgroups: net.audio
Subject: Terminal Squeal
Message-ID: <1698@tekig1.UUCP>
Date: Wed, 27-Jun-84 15:09:50 EDT
Article-I.D.: tekig1.1698
Posted: Wed Jun 27 15:09:50 1984
Date-Received: Sun, 1-Jul-84 01:45:12 EDT
Organization: Tektronix, Beaverton OR
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     In the US, the horizontal frequency for TVs (and most non-interlaced
terminals) is 15.75kHz.  Yes, this is well below 20kHz.

     You should remember that this is a low-amplitude noise (or should be, as
it is attempted to be eliminated), and therefore some people who really can
hear that frequency might not detect it in an office environment.

     For my case (my case is aged 32), I can hear the sound, but not in any 
normal sense of hearing.  It tightens the muscles in the back of my neck, but
I can barely "hear" it at all - my hearing ability drops off about 15.5kHz.
This only points out how subjective the audio field can get, I guess.  Anyway,
I know of one escalator in a local department store that absolutely drives me
bananas, though I can't actually *hear* it.

     Perhaps, some of my acquaintences would say, that's why ultrasonic waves
work at repelling rodents :-) !

Brian Diehm
Tektronix, Inc.