I have a Mac G4 with a MOTU 828mkII and a pair of M-Audio BX8 monitors. I'm hearing a faint but steady and repetitive beep (about once per second) from my monitors, and I think I've narrowed down the cause to my two external SATA drives. If I turn either one of the drives off (or both), the beeping stops. I've tried moving the drives farther away from the CPU and I've tried changing the PCI slot of the SATA card, but the results are the same.

Has anybody else experienced anything similar to this? Any suggestions on what else to try would really be appreciated.