[overgrowntroll]

YES. it happens to me when im on logic, i will pause and think, 'Whats that electrical noise'? I hit mute or change the volume from my keyboard and it stops. I too have external speakers but i don't use headphones very often. It has only happened to me a few times, but doesn't really bother me cos i press one button and it will stop. I don't get it whilst playing audio, only after.

I have the same imac as you btw, the aluminum one.