My set-up is:
iMac 3.2GHz i3 Intel
Virus TI2 Desktop OS 4.5.15
The Virus is the only thing connected to the iMac directly, it shares it's USB High Speed Bus with IR Receiver & Built-in iSight, all other USB devices are connected via a USB hub on a different USB High Speed Bus.
The buzzing is occurring on the starting up screen while the circle of dashes is working it's way round, it's very much like the buzzing you get from a guitar amp.