Annoying sound from my laptop's speakers?

I was wondering if anyone had problems with their lap-top's speakers making a sorta brrrrrr brrrrr sound .. it's like the bass is turned up extremely high but its not..even though when its turned up the sound become even worse and worse. It's like the speaker is making a fluttering noise as if it's vibrating against something. It's kinda hard to describe the sound but I've tried my best to do so...Any ideas how to fix it?