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From: ch@maths.tcd.ie (Charles Bryant)
Newsgroups: sci.physics,sci.electronics
Subject: Re: Audible effects in solid-state electronics
Message-ID: <325@maths.tcd.ie>
Date: 28 Jan 89 17:28:23 GMT
References: <9359@nsc.nsc.com> <1989Jan25.054823.2166@utzoo.uucp>
Reply-To: ch@maths.tcd.ie (Charles Bryant)
Organization: Maths Dept., Trinity College, Dublin
Lines: 26

In article <1989Jan25.054823.2166@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes:
>In article <9359@nsc.nsc.com> woolsey@nsc.nsc.com (Jeff Woolsey) writes:
>>...So, is there any validity to the theory that certain logic families
>>exhibit piezoelectric effects when operating?
>
>Much more probably you are rediscovering the fact that switching power
>supplies can "sing" and the music :-) is load-dependent.  It's quite
>noticeable on an Iris 4D when the graphics hardware fires up.
>-- 

I have heard the same effect from my Sinclair Spectrum which has a linear power
supply. The sound changes depending on what the CPU was doing. In fact it was a
good way to tell if your program had crashed as the tone changed! It may have
come partly from the video circuits as it also changed depending on what was
on the screen, but there were different sounds produced for blank screens.

inews
gives
no
prizes
for
conciseness
-- 

		Charles Bryant.
Working at Datacode Electronics Ltd.