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Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!usc!srhqla!quad1!psivax!torkil
From: torkil@psivax.UUCP (Torkil Hammer)
Newsgroups: sci.physics,comp.sys.apple2
Subject: Re: VDT fatigue
Message-ID: <3457@psivax.UUCP>
Date: 13 Jul 90 15:39:53 GMT
References: <1990Jun25.18589.2139@cec1.wust1.edu> <1990Jul12.143750.3531@acc.stolaf.edu>
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 21

In article <1990Jul12.143750.3531@acc.stolaf.edu> christm@thor.acc.stolaf.edu (Mark C. Christianson) writes:
# 
# When I was a senior in high school, I had a math class in the school's
# computer room.  I could tell the instant I walked in the door, if there
# was a monitor left on when someone switched off thier computer.  I had
# noticed that when the Apple II was switched off that the noise from the
# Apple green screen monitor got louder and much more anoying. Does anyone have 
# an explaination for this?

1. The 16 kHz acoustic output from many of the cheaper monitors is
likely to trip your middle ear reflex.  That gives you a stuffy feeling
if you can not hear the sound, and it muffles everything else.  You
really hear the difference when it changes or goes away.

2. When the monitor loses the sync signal from the computer it changes
frequency slightly.  Acoustic high freq is particular about room and ear
resonances, and it will change the sound one way or another.

3. Right after swithcing off the monitor itself you hear crackling noises
due to electrostatic discharges.  Not quite as loud as those outside
your windows (Minnesota), though. :-)