EDIT: Just updated Minecraft, and now there's no sound at all. WHAT'S GOIN ON?!?!?

Hey guys. I started using my parent's computer the other day for Minecraft cause mine was lagging, and I the first time I started the game up, it nearly blew my ears out! The second the Mojang title is gone and it skips to the main menu, the computer starts making this awful noise, like a drill. If you just blow air out your lips, brbrbrbrbr... That's what it sounds like. I know it's weird, but the sound doesn't stop until you quit the game. It seems like it had different pitches, and the sounds are different some times. about 10% of the time the sound just cuts out altogether, and meaybe another 10% of the time it actually works, but there have been a couple of times where the sound has worked, and then the drill sound started up again. TRUST ME, I KNOW IT ISN'T THE GAME!! I went through nearly all the sound files in the resources bin and NOTHING sounded like this. Doesn't happen on any other program that I know of. PLZ HELP!!!