2000 STS Rear Buzzing Noise

I have a 2000 STS with 96K miles on it.  Recently it started buzzing from the rear of the car.  The buzzing sounds like when you put a card in a bicycles spokes, ie: the faster I go the faster it buzzes.  It stops when I get down to about 5 miles per hour.  The intensity is not huge, just annoying.
 
Does anybody have any idea what this could be?
 

Possibly very cupped tires or bad hub bearing. Does noise change when turning?

I think my initial assessment of the noise coming from the  rear was wrong.  I now believe it is coming from under the hood.  I almost sounds like noisy speedometer cable or something in the drive line.  It is not in the motor because the pitch doesn't change with the RPM's only with the speed.  I don't know if an STS has a speedometer cable?  I may take it to GM tomorrow, if so I will come back an post the fix.

Good question, no the noise is the same if I am turning or going straight.

No speedo cable,you may have to take it in. Noises have to be heard many times to offer advise. 

this may be way off, but is the buzz coming from the rear fuzz box....perhaps a relay or something...... disconnect battery negitive, for 20 min...see if stops the buzz....good luck, and a big welcome to the Forum!
rickyd

I just got my 2000 Cadillac back from the GM dealership.  The problem was a bad right front wheel bearing.   FYI
 
Thanks for your comments!