[G4] Screechy speakers on a Digital Audio

[Jim Dean]

My digital speakers recently began emitting a high-pitched,
interference-like sound when the volume is cranked up. This is a
processor-upgraded 533 Digital Audio G4. It started the behavior in the past
week. Nothing in the hardware or software has been changed in at least two
months. I have restarted the machine, unplugged and replugged the speakers
and turned off various nearby electronic devices.

Thoughts?

Thanks,

Jim Dean