I've only just noticed it and it only does it sometimes, but could my MBP be suffering from the dreaded Whine? It's the dead of night here so I can't here anything other than the sound of my MBP, so now's a better time to notice it, but I think I could probably hear it at normal times. In the following sound, the first thing you'll hear is the sound with the mains cord plugged in. After the 'pop' you'll hear it with the cord unplugged (running of battery) and this is when the whine seems loudest. After that you'll hear another pop and then after a small delay, the whine goes quieter again. IS THIS THE WHINE? Thanks!