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, 3^rd day and 7^th day in both groups.

Results: 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%.

Keywords: Sensory neural hearing loss, Audiogram, DPOAE , 5-wing type ear protection