I hope somebody can offer some helps on this:
My seven month old C240 recently exibits a faint high-pitch whistling noise when the car is travelling between 64mph (104km/h) and 69mph (111 km/h). The noise is not there at speed below and beyond this range. The noise appears to be coming from the right rear passenger door. I check the weatherstripping and it appears to be fine.
Maybe some treatment to weatherstripping would cure the noise?