I would say that you shouldn't panic yet...I had a very similar problem a few weeks ago and 2 new tires, a balance, rotation, and 4 wheel alignment cleared it right up. The fact that it goes away when you turn the wheel makes me think it'* the same thing that happened to me...good luck.

I rotated my tires today and the vibrating noise is still in the same spot, I'm sure its on the drivers side. Must be the bearings-DAMN I guess I will used my next years income tax refund and replace the bearings on both sides along with CV shafts and ball joints, get it all overwith at once.

Drive the car for about an hour straight. Stop, turn off the car and get out and feel around the tire, grab the bearing with your bare hand. Compare the other side, does any side feel hot? or much different then the other? if not its not the bearing, with noise comes heat.