"Joe Kesselman" wrote ...
For what it's worth: This isn't a new discovery. There
was a time when some of us actually used the EMI from
computers as a debugging tool. With practice, we could
recognize the sound of different parts of our program and
get a rough idea of what it was doing.

At the time we were mostly using AM radios as our pickups...
so an AM loopstick antenna might work well for your experiment.

They used to do "stupid computer tricks" back in the
1960s and 1970s with specially-written code that would
play specific notes on an AM radio placed next to the
big racks full of discreete component logic circuits.
I used to do this with an IBM 1620 that I maintained.

And even more bizzare, the really high-speed printers
(like the IBM "train" printer) hit the hammers so fast
that they would also produce quite loud musical notes
and people wrote code to play songs on them. The
managers that ran the computer rooms were generally
not amused.