Sound attenuation of hearing protectors in use at work (BGIA Report 4/2009e)

Abstract: Hearing protectors used at work often reduce noise levels less effectively than during type testing. This is known from international publications and from an earlier study by the BGIA, Institute for Occupational Safety and Health of the German Social Accident Insurance (Deutsche Gesetzliche Unfallversicherung, DGUV). The Working Group "Hearing Protection" of the Expert Committee "Personal Protective Equipment" of the German Social Accident Insurance therefore initiated a study to determine the actual sound attenuation of hearing protectors used at workplaces. In cooperation with several institutions for statutory accident insurance and prevention, the sound attenuation of the hearing protectors used in various branches of industry was measured. The measuring method replicated as far as possible that used for type testing in the laboratory in accordance with DIN ISO 4869-1. On average, all of the products yielded lower sound attenuation in practice than in laboratory measurements. The effect is biggest with ear-plugs that have to be shaped before use, with a mean deviation of 7.8 dB. Other types of plugs showed less difference, with values of 5.0 and 4.5 dB. For ear-muffs the difference is 3.0 dB, and for custom moulded earplugs a value of 6.0 dB is achieved if they are not checked prior to use to help ensure individual quality fit. No data were obtained for products that had been checked. To improve the use of hearing protection in the field, employees should receive instruction at work or during occupational medical check-ups that draws attention to the care required when inserting/fitting hearing protectors. This applies particularly in the case of ear-plugs that have to be shaped before use.