Thanks for the tip. I'll try both ideas (when I get a chance; it might
be a while) and post anything interesting. I'm hoping to eventually
(maybe after I learn more about electronics) build a reasonably
sensitive EMI-only "microphone" to use as a sort of computer
stethoscope.

Here's my idea: could a computer technician, with this tool and some
practice, hear and immediately recognize the EMI signature of a dying
power supply or other bad component, the same way an expert pilot can
instantly diagnose engine troubles just from their noises? Certainly,
many technicians recognize the distinctive sound made by some dying hard
drives; but most components don't make any noise that we can hear
naturally.

-- Josh


In article ,
John Fields wrote:

If your mic was picking up EMI and also acoustic sound you could
probably get rid of a large amount of the acoustic sound by
shielding the mic's diaphagm. That is, cover the places where the
sound enters the microphone in order to keep sound out of there.
Maybe cotton balls and Scotch tape?


The other thing you might want to try would be to wind a coil and
substitute it for the mic. I'd start with a couple of hundred turns
of 24 gauge telephone wire wound on an air core just to see what
would happen, and then go on from there.