Measurement and Characterization of Hearing Protection Devices in the Presence of Impulse Sound

Abstract

Impulsive sounds can cause severe hearing damage and even hearing loss. Sound protection devices are widely used to attenuate impulsive sounds and reduce their impact on hearing. Properly measuring and characterizing the sound attenuation is essential when choosing a specific hearing protection device. Currently, hearing protection devices are often characterized using the Impulse Peak Insertion Loss (IPIL) that measures the total attenuation across all frequency bands. IPIL does not provide any information about the spectral attenuation of the device. Human hearing is spectrally sensitive, and the risk of noise-induced hearing damage is frequency-dependent. Therefore, characterizing hearing protection devices has to be done for both the peak and the full audible frequency spectrum from 20 Hz to 20k Hz. In this paper, we propose a novel energy preserving method for estimating the 1/3 octave band insertion loss using the continuous wavelet transform. To do so, we collected gunshot audio sounds from firing a sniper rifle and evaluated the sound attenuation effect of adding a sound protection device (or sound suppressor) to the rifle. The method that we called Wavelets Octave Band Insertion Loss (WOBIL) is compared with existing methods such as the IPIL, the Impulsive Spectral Insertion Loss (ISIL) and the recently published Octave Band Impulse Peak Insertion Loss (OBIPIL).