EXACT SAME thing happens to me at 160 km/h (100 mph).
It's like you are breaking through a sound barrier or something, very interesting. It's not the mirrors whistling, it's really like you are in a plane about to take off. Spoiler is a good guess, maybe this proves that the spoiler does generate significant downforce at high speeds
Originally posted by Glenn Wallace
I hear it as I pass 100 mph. I think it is the spoiler resonating.