Re: Apple RGB Monitor Making Very High Pitched Noise

[toh@freenet.Victoria.BC.CA (Marc Sira)]

In our last episode, msean@ix.netcom.com(Michael Sean Madill ) said:

>    Two of my Apple RGB monitors can't be used because the kids in my
>class say they make a high pitched noise that bothers them. It is too
>high for me to hear and my hearing is normal. Has anyone ever heard of
>something like this?

There's not really any such thing as "normal" hearing. Frequency ranges
differ for everyone, and change with age - your range narrows dramatically
as you get older. The usual estimate is a loss of about 20 Hz per day off
the highest frequency you can hear, though it's not really much of an
estimate - just a division of the barely-understood ranges measured in people
of different ages. I'm just now getting to an age where my hearing has
deteriorated enough that I can't hear every CRT in a building any more,
which is something of a mixed blessing.

If you're about my age (mid 20's to 30's or older) and have "average"
hearing, you probably have a top range of around 10kHz, so you can't hear it.
My hearing has always been hyperacute, though there have been cases of
people being able to hear truly astoundingly high tones (though perhaps "hear"
isn't the word, it's almost more like an unpleasant "feeling" with many CRT
sounds).

The kids can probably hear up to (or well past) 20,000 Hertz, which includes
the noise made by CRTs. I'm not sure what that noise is caused by, but it's
plagued me all my life, while most people around me are oblivious to it.
It can be very annoying. I suspect it may actually be something like the
horizontal sync frequency, which I believe is something above 16kHz on a GS
RGB. It's particularly bad for monitors that aren't receiving a signal (ie.
when the monitor is on, but the computer is off or not connected). It does
vary between different models, and even different monitors of the same
model. It also varies with temperature, meaning that a monitor that's just
been turned on may get quieter (or louder) as it warms up.

The noise is very real, and can be very distracting and irritating,
particularly for children in a learning environment. I'd say if it's
bothering the kids enough to complain, you should probably replace those
two monitors.

I have always classed this noise in the "unknown effects of technology"
department - along with EMR and lots of other things that no one ever bothered
to study or question before selling to the public. It may be actively
destructive to people (whether they can hear it or not) for all anyone knows,
as may half of the side-effects from technology we use - because none of it
has ever been properly studied. Perhaps those kids are just the canaries in
the coal mine...

-- 
Marc Sira			   |
{ub675,toh}@freenet.victoria.bc.ca | "Your god drinks...p-p-peach nectar!"
{aa,xx}382@freenet.carleton.ca	   '