Sometimes when I use my iBook, out of nowhere it will make this really loud high pitched sound. It is usually very high pitched static, or a high pitched whine. It hurts to hear, its worse than squeeky brakes or someone running fingernails across a chalkboard. The only way to make it stop is to just close it so it goes to sleep. I can't mute the sound or turn it down while it does it. Is there a way to fix this, or is it basically.. screwed?

EDIT: Specs are in my sig, its a Dual USB, 2001 model.