Effects of impulse noise from small arms on the organ of hearing when anti-noise devices are used

Relevance. The basis of modern rationing of noise and assessing its safety is the principle of equal energy: regardless of the source, effects are equal. However, this approach is not valid for impulse noise reaching the external auditory canal through the means of individual hearing protection. This issue needs further research.

Intention. To assess effects of impulse noise when anti-noise devices are used on the auditory sensitivity and safety of military personnel.

Methods. Effects of impulse noise of equal energy without anti-noise devices and reaching the external auditory canal through the means of protection was carried out in two groups of volunteers aged 18–23 years without contraindications for working under noise conditions. Shooters from the 1st group (12 persons) fired from an AK74M assault rifle (150 shots) in a free acoustic field. Shooters from the 2nd group (13 persons) used 6M2 noise protection headsets when shooting (330 shots).

Results and discussion. The equivalent level of impulse noise affecting the hearing organ of the shooters from both study groups amounted to 99.4 dBA. Impulse noise filtering through a 6M2 noise protection headset led to a shift in the noise spectrum to the low-frequency region, therefore the maximum increase in hearing thresholds was noted not at high (as without anti-noise devices), but at low frequencies – 250 and 500 Hz. At the same time, the hearing thresholds restored after shooting without anti-noise devices within a day, and after shooting with noise protection headsets – in two hours.

Conclusion. It was established that the impulse noise from small arms of the same equivalent level when reaching the external auditory canal through the anti-noise headphones is less dangerous in terms of hearing restoration than after direct exposure.

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