How Subject and Experimenter Variables Influence Estimates of Hearing Protector Attenuation Using Ansi-Standardized Testing Procedures

Abstract

Hearing threshold levels (HTLs) were determined using audiometrically-normal subjects with and without earplugs for two hearing protection device (HPD) laboratory fitting protocols. The experimenter-fit (EF) protocol intended to estimate the optimum attenuation of an HPD. EF involved a high level of experimenter participation and a low level of subject participation—the experimenter optimally fit earplugs to the subject. The subject-fit (SF) protocol, on the other hand, intended to estimate the more typical attenuation achievable in the real-world by well-run hearing conservation programs (HCPs), therefore, inexperienced-in-HPD-use subjects fit one of two types of earplugs on themselves using only the manufacturer's on-package instructions and without experimenter assistance. The objective was to compare the attenuation performance of the two HPD fitting protocols which varied in subject and experimenter testing participation and involvement. As expected, significantly greater attenuation resulted under EF than SF. Comparisons of the SF data to real-world studies demonstrated that SF slightly overestimated real-world attenuation, but not by nearly as much as EF. Therefore, SF better estimated the level of noise protection likely to be afforded to actual HPD users. The factors of subject gender and number of trial repetitions per subject were studied as well but did not significantly affect HPD attenuation. The results supported the work currently underway by ANSI Working Group S12/WG11 to develop a new ANSI standard to be used for obtaining attenuation data for labeling purposes which recommends the SF procedure.

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