Comparing long-term effects of different earplug fit-training methods on U.S. Marine Corps training recruits

To compare the long-term effects of two earplug fit-training methods on the ability of U.S. military personnel to self-fit a foam earplug and achieve sufficient attenuation of weapon noise during military training. Participants were randomly assigned to one of two earplug fit-training methods (control typical; n = 239, experimental experiential hearing protection device (eHPD); n = 151), and one of two hearing protector fit-testing (HPFT) schedules (quarterly, annually). 390 U.S. Marine Corps Infantry training recruits. Passing had no association with participants tested quarterly or annually and were merged to two groups for analysis. Immediately post-training, 57% of the control and 78% of the experimental training groups achieved a passing personal attenuation rating (PAR) of at least 25.0 A-weighted decibels. Approximately 12 months post-training, the passing PAR proportion reduced to 19% (control) and 37% (experimental). The differences in pass rates between groups at both time points were statistically significant (p < 0.05). The individualised eHPD fit-training resulted in a greater proportion of participants able to achieve adequate noise protection (both immediately and one year later) with issued foam earplugs. Based on our study results, the ability to adequately self-fit in-ear hearing protection is a perishable skill and annual training is justified.