Effect of modified hearing protection devices to cochlear function among Indonesian military personnel during a 105 Howitzer Cannon Shooting Practice

Objective: To evaluate the effectiveness of the use of modified hearing protection device (modified HPD) and compare it with standard HPD against impulsive noise reduction with very high intensity. Methodology: This quantitative study used a pretest-posttest with control group design. Randomization was conducted for the placement of subjects in the standard hearing protection group (control) and the modified HPD group using block permutation. The sample size is determined for a two-treatment hypothesis test. Minimum subjects in each group were 20 people. Chi Square test was used to compare changes in DPOAE results between the standard APP group and the modified APP group. McNemar's test was used to determine the difference in DPOAE results before and after shooting practice. Results: The DPOAE refer after the Howitzer 105 cannon shooting training was obtained from the group of soldiers using standard HPD (foam earplugs) with 10 soldiers (50%) and from the group of soldiers using modified HPD with 3 soldiers (15%). The group using the standard HPD has a 5.667 times higher risk of outer cochlear hair cell damage (DPOAE refer result) compared to the group using the modified HPD. Conclusion: The use of modified HPD for Howitzer 105 shooting practice had a lower risk of damage to outer hair cells in the cochlea.