Every now and then a noise will start coming from the speaker grill area on the right side my MBP. It sounds like I just put a disc in the drive (ie. something spinning, not clicking or anything like that). It's not always loud but it can get a little loud especially in a room without a TV or music on. Out of frustration I whacked the area where the power button is and it stopped. Whacking this area also appears to make it start too, and change 'pitch'. I sent it to a repair place and they couldn't even hear it, although I'm not sure how quiet their rooms are because it would be impossible not to hear this thing sometimes. I have an older MBP that doesn't make this sound at all and I'm just wondering if anyone knows what it could be.