Car smart people, what could be wrong with my car...?

I hear a chirping sound coming from somewhere up front when I'm driving slowly (with windows down). I realize it could be one of several things, and I don't think it's brakes. I'm not applying the brakes when I hear it. It's not rhythmic. It's kinda random. Normally I'd ignore something like that, but I just bought this car used. It seems to be in really good shape otherwise.