Wheel/Tyre noise from 40mph to 60mph ?

[silkysmooth]

Hi,
I've recently bought 2008 2.7 A6 Le Mans manual. While it is significantly louder inside than A6 SE with 17" wheels, it doesn't bother me that much. I assume it's those 19" wheels that does it. However, when I reach to about 40mph the noise increases significantly to bother me a bit and then goes away when go past about 55-60mph. Sounds like constant monotonous howling, nothing unusual, no vibrations, just too loud for my liking. I believe it comes from the back of the car. Tyres: Continentals - don't look to be too bad, about half worn, but could be old.
So is it tyres, wheel bearings or something else? It's just strange that only happens within that speed range.

[dan2485]

Swap the wheels to the fronts to rule out the tyres whilst doing so spin the rear wheels to listen for a bearing rumble.

Then grab the wheel at the top and bottom and with a push and pull motion check for play in the bearing.

[Lukenkarl]

Do a search and ye shall find. Very common problem, though due to tyres normally