Suitability of commercially available systems for individual fit tests of hearing protectors.

Hearing protector label attenuation is measured according to the REAT method covered by the ISO 4869-1. This method relies on optimum fitting under laboratory conditions and group statistics to predict an individual wearers hearing protector performance. The consequence is that there has been an emergence of commercially available systems that offer the capability of individually fit testing hearing protectors in the field to control how much attenuation an individual user will actually receive. The purpose of this paper is the test of these methods. Four commercially available systems were used under laboratory conditions to assess the performances of two ear-muffs, 4 pre-formed or foam ear-plugs and 2 custom molded ear-plugs for 22 test subjects. Results were compared to REAT attenuations (obtained for the same group of subjects) and also to attenuations obtained from MIRE (ISO 11904-1). Three of the four systems provide mean attenuations close to the reference values. For these three systems, individual comparisons are acceptable in terms of SNR or HML values, although discrepancies with reference values can be large. Thus these systems can be used to validate the hearing protection choice, particularly in case of custom molded plugs, as long as a large safety margin is considered.