What's wrong with my my laptop speakers?

I have a Lenovo Thinkpad, it's a little less than a year old but it's been doing this since I first got it (I haven't bothered seeing what the issue is but it's started to bug me): they are fully capable of being really nice, quality speakers, but more often than not, they switch to this weird, canned, cell-phone-esque quality. Like I'll be playing music and it'll sound really great but in a split second it'll become horrible cell phone quality. Like I said, it's been doing this since I got it and haven't cared til recently, but I just don't know what to do about it or even why it's happening at all. Anyone know?