The effect of fitting procedure on hearing protector attenuation

Realistically evaluating the effectiveness of hearing protectors continues to be a major problem in hearing conservation. The purpose of this study was to examine a laboratory-based fitting procedure (User Fit) that was designed to yield hearing protector attenuation values similar to that derived from field studies. Ten subjects who were naive to hearing protectors were used in a repeated measures design that measured real ear attenuation at threshold for two types of plugs. Each subject was tested in two fitting conditions that varied based on the type and degree of assistance given to the subjects by the experimenter. The results showed significant differences in attenuation based on the fitting procedure used, with the User Fit best approximating field data. In addition, a generalized learning effect was noted. The results suggest that any experience with earplugs leads to subsequent improvement in attenuation despite the type of earplug used. Further testing is planned with greater numbers of subjects and additional types of hearing protectors.