SCHUBERTH C4 Manuel page 56

C. THE HELMET
Note:
With faired motorcycles, strong eddy currents occur at the edges of
the wind shadow. These may significantly reduce the aeroacoustic
performance of the helmet. The motorcycle fairing should be adjusted so
that the turbulence created does not reach the bottom surface of the
helmet.
Turbulators
The patented turbulators on the top of the face shield also
optimise the aeroacoustic properties when riding and
prevent acoustic disturbances in the form of whistling
sounds that can be created by smooth and straight
edges.
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aeroacousitcally non-critical area
aeroacoustically critical area
aeroacousitcally non-critical area