Awesome Noise Opening Laptop

For a few weeks now this problem has gotten worse.
I have a 17in. gateway core duo 2ghz, 2 gb ram.

When I open it up after closing it for a while (without turning it off) it makes the noise that Sonic the Hedgehog made when doing a spin attack! At first this was awesome, but Im pretty sure it means bad things are on the way. The sound does not happen when mute is on, so it probably isnt the harddrive or anything making noise. I only very rarely get a feedback like quiet static from the speakers during normal use, but this fades after a few minutes. I'm not sure if there is a ground loose or what. Any ideas? The computer is just over a year old so no warranty.