iSight "ringing"

[JMax1]

I've recently been using my Intel iMac's built in iSight to make some iMovies, and I have noticed that there is a distinct ringing throughout the recording. I'm not sure if it is the iSight or it could be ringing from the speakers, but I can sometimes hear it when I am watching TV through my eyeTV setup. Altough the recording has the ringing even when I record with the computer on mute.

I tried searching the forums already but couldn't find anything that resembled isight ringing

Thanks!