A wheel bearing that is bad will sound like a grinding noise and the grinding noise should get worse the faster you go.
If you've ever made contact with the rumble strips on the side of a highway it will kind of sound like that when the wheel bearings are bad.
A growling, clunking or knocking noise is also common when a wheel bearing is bad.
If a wheel bearing is bad or going bad you need to get it replaced as soon as possible because the wheel bearing could potentially lock up and cause your vehicle to roll.