Real-world performance of hearing protection systems in Army aviation

Abstract

Methods to measure the performance of hearing protective devices using naive subjects were developed to better estimate the hearing protection that can be reasonably achieved in operational environments. A ‘‘preference’’ for subject-fit methods over experimenter-fit or experimenter-supervised-fit methods has been growing among many hearing conservation professionals but has not received universal acceptance. The real-world performance of hearing protection used in Army aviation was measured. Army aviators who had completed 38 weeks of rotary-wing aircraft training were used in personal hearing protector evaluations using ANSI S12.6 real-ear attenuation at threshold procedures. Using their own flight helmets (group 1) or helmets and earplugs (group 2), the aviators were instructed to fit their helmet or helmets with earplugs as they do for flight operations (i.e., an informed-user fit). Following this evaluation, an experimenter-supervised fit evaluation was performed, which included helmet and earplug fit by a technician trained and experienced in helmet fit procedures. For both groups, the real-ear attenuation at threshold results for the informed-user and experimenter-supervised fitting procedures were virtually identical. Thus, the experimenter-supervised fit procedure (ANSI S12.6-1997 Method A) is appropriate for evaluating the performance of personal hearing protective headgear in the Army aviation environments.