The attenuations of some hearing protectors as used in the workplace

A sound field which conforms to the requirements of ISO 4869 (1981) has been created in an audiometric booth which has been installed in a mobile trailer. This trailer has visited industrial sites where protectors, which were being used in the workplace, were tested. Work people, selected at random, were tested in a procedure similar to that specified in ISO 4869. The occluded and unoccluded thresholds of hearing were measured and then used to estimate the protector attenuation. Results from a number of muffs, plugs and helmet-mounted muffs, tested in the workplace, show that, in most cases, the attenuations were less and the standard deviations were greater than those quoted by manufacturers from laboratory ISO 4869 tests. The implications of these results for the selection of hearing protectors are discussed.