Usually the pump starts leaking before the bearing fails. The easiest way to find out what makes the noise us by using a car stethoscope and check al the belt pulleys. These stethoscopes are very cheap and worth the money. Just put it on the bearing brackets, as far away from the belt as possible, be careful that is does not get caught by the belt!!
In my car the small pulleys from the belt tensioner and the one above the alternator ware worn and made noise. The smaller they are, the faster they turn (and wear).