Suitability of commercial systems for earplug individual fit testing

Abstract

Hearing Protection Device (HPD) rated attenuation is measured using the Real Ear Attenuation at Threshold (REAT) method specified in Standard ISO 4869-1. This statistical method assumes optimal fitting and is applied under laboratory conditions to predict the hearing protector performance for an individual wearer. The rated attenuation is therefore generally higher than that measured in the field. A consequence is the emergence of commercially available systems, which offer the capability of individual fit testing of hearing protectors in the field to control the attenuation actually received by the wearer. The purpose of this paper is to assess the suitability of these systems. Three commercially available systems dedicated to earplugs were used under laboratory conditions to assess the performance of pre-formed, foam or custom-molded earplugs for at least 20 test subjects. Results were compared with REAT attenuations for the same group of subjects. Two of these systems ensure mean attenuations close to benchmark values and individual comparisons are acceptable for these systems, although discrepancies with respect to benchmark values can be wide. These systems can therefore be used to validate a choice of hearing protection as long as a large but acceptable safety margin is considered. They are also quick and easy to use, and can contribute to worker training and motivation.