Measuring earplug noise attenuation: A comparison of laboratory and field methods

Hearing protection device (HPD) fit-testing is a recommended best practice for hearing conservation programs as it yields a metric of the amount of attenuation an individual achieves with an HPD. This metric, the personal attenuation rating (PAR), provides hearing health care, safety, and occupational health personnel the data needed to select the optimal hearing protection for the occupational environment in which the HPD will be worn. Although commercial-off-the-shelf equipment allows the professional to complete HPD fit tests in the field, a standard test methodology does not exist across HPD fit-test systems. The purpose of this study was to compare the amount of attenuation obtained using the "gold standard" laboratory test (i.e., real-ear attenuation at threshold [REAT]) and three commercially available HPD fit-test systems (i.e., Benson Computer Controlled Fit Test System [CCF-200] with narrowband noise stimuli, Benson CCF-200 with pure tone stimuli, and Michael and Associates FitCheck Solo). A total of 57 adults, aged 18 to 63, were enrolled in the study and tested up to seven earplugs each across all fit-test systems. Once fitted by a trained member of the research team, earplugs remained in the ear throughout testing across test systems. Results revealed a statistically significant difference in measured group noise attenuation between the laboratory and field HPD fit-test systems (p < .0001). The mean attenuation was statistically significantly different (Benson CCF-200 narrowband noise was +3.1 dB, Benson CCF-200 pure tone was +2.1 dB, and Michael and Associates FitCheck Solo was +2.5 dB) from the control laboratory method. However, the mean attenuation values across the three experimental HPD fit-test systems did not reach statistical significance and were within 1.0 dB of one another. These findings imply consistency across the evaluated HPD fit-test systems and agree with the control REAT test method. Therefore, the use of each is acceptable for obtaining individual PARs outside of a laboratory environment.