My interact is silent, but my r2c3, which is nearly identical, makes a significant, I would not call it loud, hum when the power enable button is engaged[IOW it shuts up when you hit the EMO] I believe it is actually the main power relay that makes the noise, since it is actively holding in under power
I suppose you could unplug the drive card one at a time to see if it was one of them, but I have never seen that |