Re: Can an electrolytic capacitor "sing"?

From: ohaya (ohaya_at_cox.net)
Date: 03/28/05 

Date: Sun, 27 Mar 2005 22:25:25 -0500

ohaya wrote:
>
> Dave VanHorn wrote:
> >
> > Parallel plates, very close together, with varying applied field, will have
> > a varying attractive force between them. I've heard this at 120 Hz in bridge
> > rectifier systems where the cap was overlarge and the diode conduction angle
> > was rather narrow.
>
> Hi,
>
> I've got the motherboard completely out of the case now, with the power
> supply outside also, and separated with some material to deaden the
> sound from the power supply.
>
> After running the motherboard for awhile, I think that I've gotten it to
> emanate the sound. It's much lower in volume, probably since it's
> outside of the case now.
>
> What I've been doing is to block off area by area with a thick pad of
> newspaper, to try to isolate where the sound is coming from, and, I know
> that this is going to sound very weird, but it sounds like it's coming
> from the CPU itself, or something within the footprint of the CPU.
>
> If I place my 'sound barrier on one side of the CPU, immediately
> adjacent to the CPU/heatsink, I can hear the sound (it's actually more
> like a 'squealing' sound) from the other side of the CPU. In this case,
> the sound is probably coming through the channels between the heatsink
> fins.
>
> If I place my sound barrier on the direct opposite side of the
> CPU/heatsink, I can't hear the sound.
>
> On the motherboard, around the CPU socket (actually kind of underneath
> the edge of the CPU socket, I can see a couple of surface mount ICs and
> surface mount resistors or caps, but that's all that's there. I've
> tried tapping some of those to see if it affects the sound, but no
> change.
>
> So now, I guess I have to change my question: Is it possible for a CPU
> chip to "sing" or make this "squealing" sound??
>
> Again, I know that this sounds a bit strange, so my apologies.
>
> Jim

P.S. In case anyone is interested, I've uploaded a WAV file of a tape
recording that I made of the sound when the board was in the case. As I
mentioned above, the sound was much louder when the board was in the
case. I did the recording with one of those voice recorders.

The WAV is at: http://members.cox.net/ohaya/AbitNoise.wav

Thanks again,
Jim

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