You could try filtering the audio line and or power cord. Radio shaft use
to have chokes you could open up, wind the wire around and then snap back
together. Those sometimes worked. Try unplugging from the computer and
see if the interference is still there. You could also tear into the
things and start adding .001 bypass caps, but that might require some
tricky soldering.
73s
Butch Bussen
wa0vjr