Path: utzoo!attcan!uunet!ncrlnk!ncr-sd!hp-sdd!ucsdhub!ucsd!nosc!helios.ee.lbl.gov!pasteur!ames!lll-lcc!unisoft!hoptoad!xanth!rlb
From: rlb@xanth.cs.odu.edu (Robert Lee Bailey)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Computer Whine
Message-ID: <6319@xanth.cs.odu.edu>
Date: 22 Sep 88 04:13:00 GMT
References: <45900151@uxe.cso.uiuc.edu>
Reply-To: rlb@cs.odu.edu (Robert Lee Bailey)
Organization: Old Dominion University, Norfolk Va.
Lines: 38

In article <45900151@uxe.cso.uiuc.edu> mcdonald@uxe.cso.uiuc.edu writes:
>
>I just moved my PS/2 model 80 from my very noisy lab to my nice 
>quiet office. I now notice a very odd thing: When idling at the DOS
>prompt the system box makes a loud, high pitched whine. When it
>is actually running a program this ceases. The only explanation
>I can come up with is that it is drawing lower power from the
>power supply when idling, and that the supply is a switching one,
>and hence going to a lower frequency. Then when the power requirement
>goes up, so does the frequency, above the audible range. I this
>correct? Why would the MSDOS idle loop draw less power?
>
>Doug McDonald



While its true that switching power supplies "whine", I doubt that
the difference comes from CPU activity.  If the power supply is
really the culprit, it is more likely that disk accesses are placing
an additional load on the supply, which may alter the frequency
and/or volume of the whine.

Another highly likely culprit, is the video monitor.  Most monitors
use a sync signal which falls in the range of 15-25 Khz.  This, of
course, is right at the upper limit of human hearing, which makes it
that much more annoying.  Since it is JUST barely perceptible to a 
person with very good hearing, it becomes that much MORE annoying
when you realize that its there!  My monitor has a very noticeable
"whistle".  The pitch and intensity will slightly vary as the
screen changes.  Mine was SO annoying to me that my solution was
to add another LOUD fan to my system. This provided additional
cooling to my CPU case, but, more importantly, it covered up the
monitors whistle! To me, the drone of the fan is MUCH more 
tolerable (like white noise), and tends to be a soothing sound,
whereas, the whistle is more like the proverbial Chinese water
torture.

		Bob Bailey