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Attenuation of Noise by Motorcycle Safety Helmets

Młyński R., Kozłowski E., Żera J.

International Journal of Occupational Safety and Ergonomics

2009

Vol. 15, No. 3

287--293

For workers such as police motorcyclists or couriers, traffic and engine noise reaching the ears is an important factor contributing to the overall condition of their work. This noise can be reduced with motorcycle helmets. In this study, insertion loss of motorcycle helmets was measured with the microphone-in-real-ear technique and sound attenuation with the real-ear-at-threshold method. Results for 3 Nolan helmets show essentially no protection against external noise in the frequency range <250 Hz. In the frequency range >500 Hz, attenuation increases linearly at a rate of 8–9 dB per octave, to ~30 dB at 8 kHz. Lack of attenuation in the low-frequency range may cause annoying effects. In addition, high attenuation in the high-frequency range may decrease intelligibility of speech signals for a rider in a helmet. Attenuation measured in this study does not take into account noise generated by turbulent wind around the helmet. Thus, the measured values of attenuation represent a motorcycle rider’s best conditions of hearing.

Attenuation of outside noise by shotblasting helmets

Żera J., Młyński R.

Archives of Acoustics

2004

Vol. 29, no. 2

347-358

Abrasive blasting is a technological process in which forcibly propelling a stream of abrasive material is used to clean or prepare a surface. Among various physical and chemical hazards related to this process a shotblasting operator is exposed to high levels of noise. Regardless of the fact that there are no requirements to measure and report the attenuation of high level of blasting noise, manufacturers often face a question to which extent shotblasting helmets protect the operator from noise. Currently the well developed method for measuring the noise attenuation of shotblasting helmets is neither given in EN 271 standard dealing with the construction of helmets nor in EN 458 series of standards dealing with requirements for hearing protective devices. The purpose of this paper is to present the method of measurements of the noise attenuation provided by the shotblasting helmet.