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Title: Wind noise, hearing loss and motorcyclists
Author: McCombe, Andrew Wightman
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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An investigation was undertaken to establish the source and effects of noise to which motorcyclists are exposed. Various methods of noise reduction and their effects have also been assessed. It would appear that at about 40mph, wind noise caused by turbulent airflow around the rider's helmet becomes the dominant sound source, exceeding the vehicle noise and the safe occupational maximum of 90dB(A). It continues to increase, linearly with log10 speed, to reach levels of 110dB(A) at 100mph. Wind tunnel work indicates that the source of this noise is random pressure fluctuations in the thin boundary layer adjacent to the helmet shell. As currently designed crash helmets provide no useful attenuation against this low frequency noise. These sound levels cause significant temporary threshold shift after only 1 hour of typical motorway speed riding and, with time, significant permanent hearing loss in up to 45% of motorcyclists. Most riders are unaware of this noise problem; only 15-25% of riders regularly wear earplugs, which are currently the only available protection, although providing a set of earplugs with a new crash helmet at the point of sale can significantly improve the usage rate to 85%. Efforts to try and produce a "quiet" helmet using a variety of aerodynamic modifications have been consistently unsuccessful. However, incorporating a set of standard earmuffs under the helmet shell has achieved highly significant reductions in "at ear" wind noise levels. A working prototype using earmuffs and a pneumatic control system now exists and should ultimately prove to be the most acceptable solution to this unpleasant problem.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available