It is kind of a combination of things.
The helmet by itself is a noisy helmet, no way around that.
The air foil effect seems to work, I trimmed my stock shield and used that piece to create an airfoil on the windscreen.
That helped but mostly I find riding with the street helmet makes the ride a lot more comfortable for the long haul than with my XD.
It takes some trial and error to get it working right.
Just my .02