Re: Disk noise in audio

Aragorn <aragorn@xxxxxxxxxxxxxxxxxxx> wrote:
Just a wild guess, not from an IT perspective but from my
experience as a musician... It is possible that either your
speakers or - more likely - your soundchip is experiencing
microphonics. Concretely, this would boil down to your
soundchip picking up the vibrations from your hard disk
activity and amplifying them.

I myself am mainly an electric guitarist. Real electric
guitars make use of electromagnetic induction pickups -
basically composed of one or two bobbins with coil wire, with a
magnet inside the bobbin - and can therefore only be used with
magnetically conductive strings, which pass through the top of
the pickup's magnetic field - we call this the magnetic window.

You pluck the string, it starts vibrating in the magnetic
field and thus disrupts the field, and this causes a signal
to be generated in the coil wire of the bobbins. As such,
electric guitar pickups are not microphones, because they
can (in theory) only pick up the vibration of a magnetically
susceptible alloy string in their magnetic window.

Hiya,

Your description of the coil/pickup stuff seems pretty good.
But, it's quite unlikely that there is magnetic interference
affecting the internals of the sound chip itself. I speak as
a designer of chips. Also, there are regulations as to how
much electromagnetic interference is tolerable to be put out by
electronic equipment. It's *much* more likely that the disk
drive is demanding different amounts of power from the power
supply and that this is causing the power supply voltage to
rattle a little, which could be picked up by the circuitry on
the soundcard. It's still possible that the gain on an unused
channel is turned way up, and that the channel is picking up
electric field interference from whatever is running inside the
case of the computer. But, I think magnetic field interference
is pretty unlikely.

Cheers....


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