Abstract
Police officers are exposed to impact noise coming from firearms, which may cause irreversible injuries to the hearing system. AimTo evaluate the noise exposure in shooting stands during gunfire exercises, to analyze the acoustic impact of the noise produced by the firearms and to associate it with tonal audiometry results. Study designCross-sectional. Materials and methodsTo measure noise intensity we used a digital sound level meter, and the acoustic analysis was carried out by means of the oscillations and cochlear response curves provided by the Praat software. 30 police officers were selected (27 males and 3 females). ResultsThe peak level measured was 113.1 dB(C) from a .40 pistol and 116.8 dB(C) for a .38 revolver. The values obtained for oscillation and Praat was 17.9±0.3 Barks, corresponding to the rate of 4,120 and 4,580 Hz. Audiometry indicated greater hearing loss at 4,000Hz in 86.7% of the cases. ConclusionWith the acoustic analysis it was possible to show cause and effect between the main areas of energy excitation of the cochlea (Praat cochlear response curve) and the frequencies of low hearing acuity.
Highlights
IntroductionIn Portuguese, is a word derived from Latin’s rugitu, which means large noise
Noise, in Portuguese, is a word derived from Latin’s rugitu, which means large noise
Considered fundamental to associate the exposure of military personnel to firearm noise, the goal of the present study was to assess noise exposure at the shooting stand of the police force, to analyze the acoustic spectrum of the noise produced by the firearms, transforming these values into the Bark scale, in order to compare these data with the audiometric results
Summary
In Portuguese, is a word derived from Latin’s rugitu, which means large noise. Impact noises are usually produced by quick gas expansion, such as that produced by firearms or bomb explosions These types of sound can reach intensities of 140 dB SPL (sound pressure level) in frequencies around 2 and 3 kHz and, for this reason, they are harmful for human hearing[3]. When the human ear is exposed to impact noise, at a sound intensity of 120 dB or higher, there is a risk for acoustic trauma This noise intensity can cause important and abrupt lesions to the cochlea, such as base membrane rupture, tissue and hair cell disarray. The extension and the grade of the hearing damage has a direct relation with the sound pressure intensity, duration in time, frequency and the greater or lower susceptibility of the individual, which can cause changes to the hearing threshold, or noise-induced-hearing-loss (NIHL) which, just like the acoustic trauma, is irreversible
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