In my experience, most windscreens on "adventure" bikes from most manufacturers really, really suck. The problem is that a windscreen that is short like a sport bike screen is pretty useless for an upright rider. A screen that is tall enough to get the wind up over your head like the CalSci stuff or some of the solutions from Madstad, is not going to look good in a showroom (or anywhere else). BMW does a decent job, but at a price and for a very specific target market and in part by offering a variety of windscreens. There's a reason they went for a much shorter shield on the F700GS than on the F800GS. All their research showed that the purchaser of the former is going to be almost entirely on pavement, while the latter is going to do more "serious" adventure riding. For the street they went with the short shield because it's quieter! V-strom shields suck. Versys shields suck. 500X screens suck.
The problem is that they tend to direct the airflow at the precise worst point, which is right at the bottom of the helmet where it creates an awful low-frequency buffet that gives me a headache no matter what earplugs I use. Not a matter of sound level as much as the frequency/nature of the sound. Get a taller screen and it will drive the air higher. Get rid of the screen and you'll take more wind to the chest but your head will be in clean air. Use the stock screens and your experience will suck. Hold your hand across the front of your neck right below the chinbar and most of that noise goes away completely.
I find this is particularly a problem with the Shoeis. My old Icon Airframe is quieter behind a windscreen than my Quest because it seems to do better with wind coming at the neck roll. The "upright" Shoeis (GT Air, Quest) seem to be designed on the assumption that you'll be behind a large touring screen. The sport helmets (RF1100/1200, X12) are designed for a 3/4 to full-tuck position. None of them do well in my opinion on an upright bike with a mid sized screen and I find them somewhat lacking on naked bikes too. They are incredibly sensitive to head position. Move your chin up and down just a little bit and the noise level changes tremendously. Hold your hand out under the chin bar to block the wind and the problem goes away completely. (I won't even talk about the Neotec, which I thought was a disaster in terms of noise both from the neckroll and the chinbar joints.) I just switched to an Arai RX-Q. Best money I've spent. Can't wait for their new pro-shade option.
Go over to Stromtrooper.com (another Motorcycle.com site) and read their threads that have been going on for years about the problems with buffeting on all the V-stroms including the latest one that supposedly addressed the problem with a new windshield design (it didn't, despite years of feedback and home-made solutions). Do the same at Triumphrat for discussion of the same issue on the Tiger 800s. It's not uncommon with these bikes. The manufacturers all know what can be done to address the issue because it's been hashed out by motorcyclists all over the world since the first adventure bikes came out. The problem is that the solutions look dorky and manufacturers are not interested in putting out bikes whose look is offputting. As I said, the solution seems to be either taller screens or shorter screens. Noise on a motorcycle is ineveitable and the faster you go the louder it'll be, but that migrane-inducing low-frequency pounding is not inevitable and can be easily removed.