hmmm.... weird, if your belt tensioner goes it whines when you drive, as mine did, but it also rattled on tick over, you can only hear this when you are stationary and looking at the engine, might be worth a check anyway as its easy to do, also you could jack the car up and give the front wheels a pull about, if one has movement when you pull the top and push the bottom and the other doesnt then its prob a wheel bearing.... they are the easiest things to check, other than that i dont know... ill leave that to someone else to answer, lol.