Critical Issues Regarding Hearing Protection Devices

The HPD's efficacy is evaluated by calculating the exposure level when hearing protectors are worn. This estimate is based on two aspects: the spectral characteristics of the specific noise to be attenuated and the attenuation values of the specific device. The latter are determined following the REAT (Real-Ear Attenuation at Threshold) technique which evaluates hearing threshold levels on a subject with and without the HPD. According to the EN 24869-1 standard, 16 selected subjects fully informed of the proper HPD wearing procedures (trained-fit) have to be tested. This method provides unrealistically high attenuation values which are not representative of those found in the workplace, where workers are neither selected nor expert and where fitting procedures are minimal. Although these values are reported on the HPD label as manufacturer's attenuation data, they should not be used in a reliable hearing conservation program. This paper illustrates two possible solutions: adoption of the subject-fit procedure which allows for a realistic estimate of attenuation on the group of subjects and an assessment of protection attained from an HPD on specific workers.