Internal microphone

Hi,

I use my macbook to make music on Ableton 8. This program has a feature which allows the user to record sound from an external source (through a mic) or from another channel in the program itself. Whenever I try to record internally, the mic on the mac starts picking up sound and this also gets recorded. Even when I set the mic volume to minimum, it still picks up background noise at a very low level which is still apparent while recording.

Is there any way I can turn off the mic?

Thanks,

Rahul.