Xref: utzoo sci.physics:5755 sci.electronics:4903
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!ucsd!brian
From: brian@ucsd.EDU (Brian Kantor)
Newsgroups: sci.physics,sci.electronics
Subject: Re: Audible effects in solid-state electronics
Keywords: VAX FPA CD
Message-ID: <1424@ucsd.EDU>
Date: 28 Jan 89 17:51:33 GMT
References: <9359@nsc.nsc.com> <8650@ihlpl.ATT.COM>
Reply-To: brian@ucsd.edu (Brian Kantor)
Organization: The Avant-Garde of the Now, Ltd.
Lines: 12

I've heard memory boards sing; it wasn't the power supply because I was
running the system off of batteries at the time, using just simple monolythic
pass regulators.  I believe that it was the high-current output driver
structures that were the cause, since in write-only tests, and during
refresh (neither of which turn on the output drivers in the chips) did I
hear the crickets chirping.  I don't know what the physical effect is
(thermal, magnetic, poltergeisten), but it's real.

Of course, in larger machines, it's most likely the switching supply
loading down into the audible range, but there could be chirping chips too.

	Brian Kantor	UC San Diego