Wheel bearing noise is common but your description doesn't exactly match the typical symptoms. They will sound like an airplane engine, but unless they're really bad, you won't hear it below about 25 mph.
First I'd raise all four tires off the ground, then run it in gear to listen for the noise. If it's a wheel bearing, you won't hear it with the weight off of it. You CAN hear it by listening next to it with a stethoscope. It won't be nearly as loud but you'll tell the difference between it and the one on the other side. If you can hear the noise when standing by the rotating wheel, inspect the brake rotor.
You can also check at the auto parts stores that rent or borrow tools to see if they have a "Chassis Ear". That is a set of six microphones, a switch box, and head phones. You place the microphones at suspect points, then switch between them while listening on a test drive. By moving them around you can zero in on the source of the noise.
Friday, July 22nd, 2011 AT 10:40 PM