Noise levels under a motorcyclist's helmet are high and increase rapidly with road speed. Many motorcyclists may suffer damaging noise exposures if they frequently travel at high speeds for long periods. For working riders, e.g. couriers or police motorcyclists, exposures may regularly exceed the Second Action Level of the Noise at Work Regulations 1989. Above 60 to 70 km/h (35 to 45 mph) aerodynamic noise from the airflow around the motorcycle and rider is the dominant source. This paper reports noise measurements in a wind tunnel and on the road to quantify noise levels, identify noise sources and paths, and to investigate the possibility of noise reduction. Noise levels and spectra were measured in the 2.1 m x 1.7 m Wind Tunnel at Southhampton with miniature microphones at the ears of a rider. The main noise source was the turbulent flow from the top of the windscreen. The turbulence hits the helmet at a position somewhere between the neck or the top of the visor depending upon the windscreen's height. This position determines whether improvements to the sealing round the neck or improvements to the visor and its sealing and hinges will be more effective at reducing noise. Noise reductions up to 8 dB were achieved by simple helmet modifications or treatments. The lowest levels at the ear were obtained under earplugs and under a flying helmet containing earmuffs with active noise reduction.
Noise levels and noise reduction under motorcycle helmets
Lärmpegel und Lärmminderung unter Motorradschutzhelmen
1996
4 Seiten, 3 Quellen
Conference paper
English
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