Ok, this scared the crap out of me - remember this is a laptop and I was watching this on a macbookpro on my lap - exploding batteries etc:
http://gizmodo.com/gadgets/laptops/the-mysterious-macbook-pro-noise-198298.php
http://www.youtube.com/v/uwuMcFt07x8
:eek:
One explanation was that it sounds like a fan - I didn't think the macbookpro has a fan... Can't hear one and a freind told me that's why it get so hot.