Fit test data: Attenuation of uniform-fit high-fidelity hearing protection devices

High-fidelity earplugs vary physically (shape, material, and filter properties) and acoustically (amount and uniformity of attenuation). They often have low noise reduction ratings and relatively flat attenuation profiles to limit music distortion. However, achieved attenuation varies as with other hearing protection devices (HPDs). Fit testing principles recommended in DoD Instruction 6055.12 and NIOSH science policy were assessed with high-fidelity HPDs. Achieved attenuation was measured before and after training to use four high-fidelity HPDs. Only one HPD product was tested per visit, with HPD order counter-balanced and return visits scheduled after real-world use of study HPDs. There were statistically significant main effects for training, HPD, and order, with no significant interaction effects. Pair-wise comparisons with Bonferroni corrections revealed statistically significant increases in attenuation after initial training with no further increase after additional training. When participants previously trained on another HPD were compared to those attending initial study visits, there were statistically significant main effects for training and HPD, with no interaction effects. Participants previously trained with a different HPD achieved greater attenuation during tests with other HPDs, suggesting retention of knowledge. The use of fit testing and training resulted in greater achieved attenuation with high-fidelity HPDs.