Path: utzoo!utgpu!watserv1!watmath!maytag!watstat!dmurdoch
From: dmurdoch@watstat.waterloo.edu (Duncan Murdoch)
Newsgroups: comp.sys.ibm.pc
Subject: Re: GAS PLASMA SCREENS!!
Message-ID: <1947@maytag.waterloo.edu>
Date: 13 Apr 90 22:59:24 GMT
References: <1990Apr10.002440.9812@ux1.cso.uiuc.edu> <26226d66.1467@petunia.CalPoly.EDU> <3366@jato.Jpl.Nasa.Gov> <5603@amelia.nas.nasa.gov>
Sender: daemon@maytag.waterloo.edu
Reply-To: dmurdoch@watstat.waterloo.edu (Duncan Murdoch)
Organization: U. of Waterloo, Ontario
Lines: 13

Most of the discussion of radiation from CRTs so far has been about xray and RF
electromagnetic radiation.  But most CRTs are also strong ultrasound emitters.
Personally, I find it very irritating to be in the same room as some colour TVs
or CGA monitors for long:  they're both emitting strongly at 15 KHz or so,
just within the range I can hear, and very nerve racking.  I remember once
having my IBM EGA monitor tested, and in CGA modes the 15 KHz emission was
easily detectable, but in the EGA modes, where I thought things were fine, 
it was even louder at 20+ KHz.

I wonder how many health effects from CRTs are actually due to the sound, not
the EM radiation?

Duncan Murdoch