i was getting wind noise on my 1998 C230, sounded as though a body panel was shunted or a window wasn't closing tightly.
The culprit of the noise was that a metal heat shield under the car had bent down into the slipstream. Bent it back up and the noise went away.

I think when I use a garden hose to spray down the botton of my car it moves the shield down a bit and then when I get on the road for a high-speed cruise the wind moves the metal piece further down and then the noise.