This study assessed attitudes toward the use of hearing protection devices (HPDs) and the effect of an educational intervention on fit-testing results by comparing personal attenuation ratings (PAR50) before and after the intervention. Employees (n = 327) from a large metal container manufacturer at four geographic locations were tested with a field attenuation estimation system (FAES) to identify workers (n = 91) requiring intervention. PAR50 values significantly increased from baseline to post-intervention (p < .001, 15.1 to 26.9) and at the 6-month follow-up (p < .001, 95% confidence interval = -11.2, -6.3). Perceived self-efficacy scores for using HPDs significantly declined from baseline to post-intervention (p = .006, 95% confidence interval = 0.3, 1.9), but were not significantly related to PAR50. Therefore, a FAES can assist the occupational health nurse to identify workers at high risk (low PAR50), teach proper fit and use of HPDs, and improve hearing protector selection.