I've noticed this too. It was silent when I got it a few months ago (used). I think the garaged used some kind of withchcraft on it as it rattles loads now. Still love the car though.
Yeah for it depends on the road surface. I've not helped it as I have the rear seats down almost always and something in the boot has a horrid buzz between 1100and 1400 rpm. @ Exact frugal cruising revs!