I've recently started to hear an unsettling noise in my engine bay... it's like a rattle/buzz/whine? It also sounds to me somewhat like bearings gone dry in something and buzzing? When I try to locate it with the hood popped, it seems to be located very near, or indeed be coming from the alternator.

On close inspection around the alternator area I noticed that the rubber belt connecting all those parts at the passenger side ("front"?) of the engine has some cracking in it that is easily seen... cracks maybe a millimeter to three deep.

So I'm wondering... could an aging belt cause this kind of noise? How should I judge when I'm due for a belt replacement, and is an expensive project at a decent/fair shop? About how much should I be looking at for a preventative belt replacement anyway?

Any ideas on how to further isolate this rattle/buzz/whine noise would be greatly appreciated also.

Thanks Brick-ers!