An empirical study of comfort afforded by various hearing protection devices: Laboratory versus field results

Abstract Two studies, each using 40 subjects and four hearing protection devices (HPD), of which three were common to both studies, were conducted to assess perceived user comfort based on multidimensional bipolar rating scales in controlled laboratory and industrial field settings. Subjective comfort data were obtained in conjunction with psychophysical attenuation results reported elsewhere for both studies. The behavioral laboratory experiment investigated the effects of fitting procedure, activity movement, and HPD wearing time on first-time HPD user comfort, while the field study determined actual comfort achieved by noise-exposed industrial workers who used HPDs on the job. In the field study, subjects were pulled from their workplaces without prior knowledge of when they were to be tested and without readjusting the fit of their HPDs. The results of statistical analyses indicated that user-rated comfort achieved with the earplugs (particularly a foam earplug) was noticeably sensitive to different fitting procedures, whereas the earmuff and the ear canal cap devices were resistant to the fitting effect. In the laboratory study, perceived HPD comfort degraded significantly over a 2-h wearing period for the earmuff devices, while the earplugs provided more consistent comfort over the period. Among the four single HPDs, the most and the least comfortable, judged by the subjects, were the foam earplug and the canal cap, respectively. The field study comfort results did not validate those of the laboratory study, implying that it may be infeasible to devise a reliable short-term laboratory test which realistically estimates field HPD comfort.