buzzing noise

Anybody ever have their computer buzz at them? the closest comparison I can come is like the timer buzz on a dryer, telling you that the dryer is almost done. The OS is windows XP, a viewsonic a70 monitor. The sound is coming out of my speaker system. And AMDk 1.3 chip on a first mainboard motherboard, with a GEforce 400 video card. I am puzzled. I feel like it is trying to warn me of something but I have no idea what.