Hearing threshold shift measured by pure tone audiometry after gun shot exposure in military personnel not using hearing protectors

Awareness of the prevalence and intensity of acoustic traumas and the permanent impairments has an important role in planning preventive programs. This study was performed to evaluate temporary or permanent hearing threshold shift with the help of Pure Tone Audiometry among a group of military personnel in the shooting gallery.

In this cohort study performed in 2010, 40 military forces from a military unit in Tehran were selected by simple randomized sampling method. Pure Tone Audiometry was performed on samples before and immediately after gunshot exposure and also a week later. Threshold Shift (TS) analysis and comparison was done separately and for the mean frequency of 3 to 6 KHz. Data were analyzed using descriptive statistical methods, Chi-square test and paired T-test by SPSS 17 software.

After exposure to impulse noise, 28 individuals (70%) reported at least one hearing symptom that tinnitus was the most common one. Sixteen individuals (40%) showed TS increase in at least one of the studied frequencies. TS was only significant in the frequency of 4000 Hz for the right ear (p=0.0001) while separately evaluating the frequencies. The clinical findings and audiogram changes had remained in 8 and 6 participants respectively after one week.

Temporary or permanent threshold shift due to impulse noises can be detected by Pure Tone Audiometry. Assessment of hearing health in military personnel during the training courses and use of proper personal protective equipment is highly recommended.