So imagine a side window is barely cracked open so you can first start to hear the wind noise. That is the sound that was coming from somewhere in windshield area. I know that is pretty general, but it is nearly impossible to localize the sound. We owned the car for months before it suddenly started doing it one day. Then it quit for a few days a couple months later, then started up again for a few months. Now it has gone away. I have NO IDEA what it was.

The dealership thought maybe the electric gate that moves when you selected the recirculate button, defrost button, etc. was caught in an in-between position to cause air to flow noisily over it. I don't know. I wish I did because I'm afraid it might come back. If it happens again I'll use painters tape to seal off all the areas around the windshield to make sure it isn't a poor seal causing it. I also wondered if the rubber stoppers at the front of the roof rack rail weren't fitting correctly. Who knows, but if you have this issue (especially if you find the fix) please make a complaint on this site with the steps you did to fix it.