sounds like driving w/ snow tires

[Hawkdaddy63]

Just bought an 05 X5 3.0 with sport suspension. When I get above 40 mph there's a sound from the rear that sounds like I have snow tires on the vehicle. I't barely audible when I've got my foot on the gas, but you can really hear it when I coast and it keeps humming until I coast down to 20 mph or so. The humming is in direct relation to the speed of the car, e.g. faster the car goes, so does the noise.

Local "european shop" mechanic says it's not wheel bearings and that these cars just make that noise. I've got brand new tires on it, so cupping shouldn't be the problem.

Is this normal?

Any help is appreciated!