Physical Characteristics of Gunfire Impulse Noise and its Attenuation by Hearing Protectors

Abstract

The peak sound pressure level (SPL), spreading of pressure wave and other physical characteristics of the impulse noise from weapons were studied in actual shooting conditions for assessment of gunfire noise exposure. Additionally, the attenuation of SPL by hearing protectors was measured with miniature microphones to evaluate protection efficiency in real shooting conditions. The peak SPLs at the shooter's ear ranged from 132 dB (miniature rifle) to 183 dB (howitzer). The spectral content of the main part of the acoustic energy was less than 400 Hz (peak 16-100 Hz) for large-caliber weapons and 150-2,500 Hz (peak 900-1,500 Hz) for small-caliber weapons (rifles). The safe distances from the noise source (less than 140 dB peak SPL) were 50-200 m for large-caliber weapons. Rifle impulses (assault rifle, caliber 7.62) had a peak SPL of 154 dB at a distance of 4 m from the muzzle. The peak SPLs of different explosives ranged from 125 to 185 dB at distances of 10 to 300 m. In rifle shooting, the attenuation efficiency of earplugs (16dB) or small-volume (thin) earmuffs (17 dB) was not sufficient and their use as sole protectors cannot be recommended. Instead, large-volume earmuffs should be used. Impulses from pistol and shotgun were fairly effectively attenuated both by small-volume and large-volume earmuffs. All kinds of earmuffs appeared to be ineffective (attenuation less than 15 dB) against impulses from large-caliber weapons with energy content at very low frequencies. Therefore, the combined use of earmuffs and earplugs is recommended for the most noisy operations. On the basis of the present data, wider safety zones were adopted in the Finish Defence Forces at shooting with different weapons.

Assessment of Impulse Noise Level and Acoustic Trauma in Military Personnel

“…The small-caliber weapons have been considered to produce a peak level of 132-165 dB with a frequency spectrum between 150 to 2500 Hz (22)(23)(24). Even explosion noise of gunfire can reach up to 170 dB A (1, 5).…”

Impulse noise generated by starter pistols

“…Internationally, 120-140 dB peak SPL limits (weighted or unweighted) are referenced in the international occupational noise exposure standards for Australia, Brazil, Chile, Columbia, India, Israel, Netherlands, New Zealand, United Kingdom, and Venezuela (Suter, 2007). Peak levels from firearms shooting projectiles usually exceed these limits for both the shooter and the bystander (Flamme et al, 2009b(Flamme et al, , 2011Kardous et al, 2003;Murphy & Tubbs, 2007;Odess, 1972, Ylikoski et al, 1995, and the current authors' unpublished data, 2012. In recent studies, mean peak levels for firearm impulses ranged from 141-167 dB SPL at the shooter's ear and at a bystander position to the left of the shooter for a subset of civilian firearms and ammunition, (Flamme et al, 2009b(Flamme et al, , 2011.…”

Database for a hearing conservation program

“…Forest workers exposed to shooting noise demonstrate approximately a 10dB greater decrease in hearing than those with only occupational exposure to chainsaw noise (Pekkarinen et al, 1993). The NIHL appears at a younger age in military personnel than in other groups of workers exposed to noise (Ylikoski et al, 1994(Ylikoski et al, , 1995. Soldiers exposed to large-calibre weapons have a higher risk of NIHL, as the HPDs are less effective due to the non-linearity of attenuation against very high-peak levels and the low-frequency components of large-calibre weapons (Ylikoski et al, 1987;Toppila et al, 1995).…”