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

Objective: 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.

Design: 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).

Study sample: 390 U.S. Marine Corps Infantry training recruits.

Results: 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).

Conclusions: 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.