The typical airflow pattern of the wake from most windscreens is called a van Karman vortex. At speeds of 50-90 mph, the air swirls off the windscreen in an approximate 90-degree segment of rotation, hits the bottom of the rider's neck on the way up, and curves off the shoulder at approximately 45 degrees.
National Cycle gave the VStream its name for the shape it takes at the upper edge. The patented "V" shape is so quiet because it pushes this vortex out and away from the side of the rider's head. The rider’s helmet then resides in still air, and the passenger's environment is greatly improved as well. Of course, with small sporty screens of different sizes, the effect on the rider will vary, but there is always a notable difference in quietness and comfort!
Note: Image for reference only. Actual product may vary according to vehicle.
All of the windshield dimensions provided are based on the following: