Transient Threshold Shift after gunshot noise exposure


Otolaryngology Department, Tehran University of Medical Sciences


Occupation Medicine Department, Baghiatalah University of Medical Sciences


Department of ENT, ENT Research Center, Tehran University of Medical Sciences, Tehran, Iran

B-ENT 2013; 9: 133-139
Read: 351 Downloads: 321 Published: 12 February 2020

Transient Threshold Shift after gunshot noise exposure. Background: Many people, such as soldiers, are routinely exposed to gunshot noise during target practice. It is suspected that this high-intensity noise may affect audition through repeated Transient Threshold Shifts (TTS); it can also mechanically alter auditory components such as waves. This study investigates the scope of gunshot noise from the AK-47 rifle (Kalashnikov) and the impact on the shooters’ audition.

Methods: Forty soldiers (80 ears) were recruited in this study. They were all young and being exposed to gunshot noise for the first time. Gunshot characteristics were measured before exposure. The soldiers underwent auditory evaluation with Pure Tone Audiometry (PTA) and Oto-Acoustic Emission (OAE) once before exposure and immediately (less than one hour) after exposure.

Results: The AK-47 gunshot noise pressure level varied between LAIm = 73.7 dBA to LAIm = 111.4 dBA. Fourteen participants had subclinical hearing impairment in their pre-exposure evaluation; this number increased to 16 after the exposure. Six months post-exposure and later, the number of cases with impairment had fallen to eight (improvement in 50%). Both pre- and post-exposure OAE results were within normal values, while PTA results indicated a significant threshold alteration only at 6 kHz.

Conclusion: The results of this study confirm that exposure to gunshot noise with no ear protection can represent a significant hazard for auditory function, especially at higher frequencies.

EISSN 2684-4907