2003 Buick Century growling sound

There's a few different ways to identify a noisy wheel bearing. One way is to raise that tire off the ground, then feel for the vibration in the coil spring when you rotate the tire by hand. I don't know how well that will work on your car though. Wheel bearings don't typically make noise just at certain speeds. My preferred method is to run the car in gear on a hoist, then listen next to each bearing with a stethoscope. You'll definitely hear the noisy one. The third way is to use a "Chassis Ear". That's a set of six microphones, a switch box, and head phones. You clip the microphones to suspect parts, then drive around while switching between them. Be aware that a lot of mechanics have never heard of this tool. Suspension and alignment mechanics use them to find all kinds of noises.