You don't have to open any window to eliminate the noise. I also noticed the unpleasant noise and here is what I did:

- Open the moon roof completely.
- Hit the button once as if you are about to close it, your moon roof should close little bit (about 4 to 5 inches) and then stop. At this position, you will no longer hear the helicopter noise. Not necessary the best solution but at least you don’t have leave the window open. Good luck.