Background: At present, ear protective devices during gunfire by Thai military training conscripts are not routinely used. The 5-wing type ear protection was invented to protect them from hearing loss with lower cost and better transmitted speaking voice.

Objective: To study the effectiveness of 5-wing type ear protection in shielding sensorineural hearing loss (SNHL) from military shooting training.

Materials and Methods: The study design was a randomized control trial (RCT) study. Sixty conscripts during routine training were enrolled and randomized in 2 groups: not using ear protection and 5-wings type ear protection groups as they routinely trained. Audiogram and Distortion Product Otoacoustic Emission (DPOAE) was performed before and after firing within 24 hr, 3rd day and 7th day in both groups.

Result: Immediately after gunfire, those not using ear protection group had SNHL more than the other group at a high frequency (53.2% vs. 0%, p < 0.05). At day 3, the hearing levels were gradually improved at all frequencies except 6,000 Hz. At day 7, three conscripts (10%) in the not using ear protection group still had SNHL detected by audiogram, 12 individuals (40%) had abnormal outer hair cell (OHCs) function detected by DPOAE.

Conclusion: The 5-wing type ear protection could prevent SNHL immediately after gunfire training. DPOAE had higher sensitivity than audiograms in detecting OHCs deficiency up to 30%.