A normal wheel bearing should have no noise. Noise is made when a bearing goes out and metal rubs metal. A good way to check your bearings is to jack up the vehicle and see if it has side to side play in it. If so you have a bad bearing and should be replaced immediately.
It should be pretty quiet and turn smoothly. Any grinding, squeaking, squalling, scraping, or gritty sounds resulting from the wheel turning indicates a problem.
