I get a very loud flaping type sound when my passanger window is half way down. Kinda like the seat belt is flapping against the side molding, but that isn't it. It only happens on the passanger side, & only if the window is 1/2 way down, any more & the noise stops. If the window is all the way down it's gone too. Happens at any speed over 15mph. Anyone else have this happen? Any ideas, This is a 2002 with the new smaller mirrors.

 

This is common in many cars. What happens is that wind gets caught within the window seal (the rubber seals that the actual window glass slides up and down against) and creates a loud turbulance noise.

Not a major concern. Either slightly crack your window or use your sunroof for ventilation.