EMC and computer microphonics

Hello

Has anyone noticed that when EMC starts up the stepper tasks
that your computer "whines" at the emc task rate? I have been
searching for this anoying problem and it seems to come from the
disk drives. I got a clue because the sound stops for an
instant when the disks get busy. Is this a "microphonic"
phenomena? i.e. vibration casued by the ripple in the supply or
a control line? Any one else hear this? I have it on more than
one machine.

dave