Abstract
An investigation was undertaken into the source and levels of wind noise in motorcycle helmets, and their sound attenuation characteristics. All noise measurements increased in a linear fashion when plotted against log10 speed. Low frequency wind noise displayed a greater rate of increase than vehicle noise and surpassed it and the recommended 8 hour occupational maximum of 90dB(A) at approximately 17m/s (40mph/68kph) to reach levels of 111dB(A) at 44m/s (100mph/170kph). There were no statistical differences in the sound levels for different motorcycles, riding position or helmet fit. There were small but significant differences between helmet types. A wind tunnel analysis indicates a turbulent boundary layer as the sound source.
As currently designed, a typical motorcycle crash helmet provides no useful sound attenuation below 2000 Hertz and thus little protection against the damaging effects of wind noise. It is suggested that improvements in helmet attenuation characteristics would go some way to addressing this problem.
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