I think maybe a wheel bearing? I have noticed it for about a few thousand miles. In a straight line perfect, but when the wheel is turned to the left on a sweeping long turn it makes a vibration sort of a ??whirring?? sound every second or so. very rythmic.

The only time i really notice it is in the mountains, on big turns and long sweepers.

Not a squeal like a lot of other tires. It sounded more like a window airleak. Is gone now that I've changed tires.

Consider swapping wheels/tires from side to side and see if the noise changes.

but now that i think about it I just got the tires put on and the noise was there with both my winter and now summer set up.

At first I thought that it was the M3's that I was running for the winter. but alas Whirr, whirr, whirr .....

I have a similar problem. It's very hard to pin down. My local service department was unable to detect the noise/vibaration. I haerd it with both (brand new) winter and (1/2 worn) summer tires. I can feel it when driving straight, it's most noticeable between 40-60 MPH. I kinda feel it in the gas pedal.

I describe it as:........mmmMMMMmmm.........mmmMMMMmmm.......

It gets higher in frequency at higher speeds, seems to go away when turning (on a sweeper) in one direction but not when turning the other way.
It's still there if I drop into neutral and coast.

I put a microphone under the carpet but was unable to record the sound.

The dealer claimed they ran the car on a lift with a stethoscope on the wheel bearings. My guess was wheel bearing or maybe differential bearing? I do not know if I can get a mic or transducer onto the driveline somewhere and try to record this vibration somehow. It's frustrating. Very subtle though.

-Joel.

I had a Porsche 928 that would make a gurgling noise in the rear when cornering hard. It was the wheel bearings. The rear of the 928 and front of the a8 use the same bearing principal becasue the wheels are driven respectively. If your car is high mileage consider doing the bearing. The bearing is in a bolted in carrier race. I would buy the carrier race and the bearing , then pre-assemble it for a ready to use assembly. The feasibility of this differs by year. This makes it a 2 to 3 hour bolt in job.