Iphone 4 buzzing sound?

My Iphone 4 is making a buzzing sound coming from the speakers for no reason. It happens strongly when I'm about to receive a text or call, but it's pretty constant. I just noticed it like 30 minutes ago. I've tried resetting it but no luck. Has anyone else had this problem?

Is this a jumpy kind of noise? If so, then its normal-ish. I would take it to an apple store and get the 'geeks' there to look at it. Or you can take it back to where you got it, if you got it elsewhere.