moonroof wind noise
 

I was thinking about getting a moonroof deflector but they are kinda expensive. Anyway when I was driving down the road with my moonroof open I put my hand up there and pushed down that little plastic deflector that pops up when you open the roof. Almost all the wind noise went away. So, what is the purpose of this thing? If I take it off will it do anything bad? I thought maybe it was there to improve gas mileage with the moonroof open.

I have the deflector, but it still makes some noise. I haven't heard what it sounds like without the reflector, so I don't have anything to compare mine with. But, IMO, save your money, because there's still noise.

i love the moonroof deflector. works like a hot damn. i can have the roof open at 120 kph and it doesn't feel like a tornado in the car.

i believe the little pop-up thing will prevent some of the buffeting you'd experience without a full deflector but it's not going to do much for noise reduction (in fact, as you said, it's noisier)

Yeah, I have found that if I reach up and push down the flip up deflector, the sound changes, but I wouldn't call it quieter. Instead of the higher pitch SCHHHHH noise with it up, there is like a WOMMMMMMM noise and LOTS of wind buffetting with it down. I prefer a little extra noise to having it feel like a tornado in my car :)

I don't have the deflector on my car...I think it kinda takes a little away from the open feeling I enjoy having the roof open.

If you have a roof rack then remove it. That high pitched whistle will be no more.