i just noticed this, but when i was playing a game (the rpm of the fans were at max) i tilted my MBP and the was a humming noise whenever i moved it. like when you touch a moving fan and its makes the noise. i dont know how else to explain it (if you have a fan, turn it on and touch it : ) is there a way to tighten the fan down or something? seems to me that the fan might be a tad bit loose and its moving slightly.