Fritz1, this noise you are hearing, does it occur at the same time the car is vibrating? Recently I experienced something like this where the "rhhhh" starts low then gets louder whilst the vehicle feels like it's going over ripples on the road. This happens for a few minutes then disappears. Three trips to the dealer and no solution yet. They did a road force balance for the 4 tires and changed a stop light switch. Problem still there. I have 200 miles left on my btb warranty and am worried I might be stuck with this.
