Contribution
Impact of the Tissular Conduction, Earplug Transmissions and Leakages on the Hearing Protection Facing Impulsive Sounds.
* Presenting author
Abstract:
Hearing protection devices (HPDs) prevent acoustic trauma from high-level impulse noise. However, their performance is limited and depends on the device and noise characteristics. The main limiting factors are (i) wave transmission through the outer ear tissues (tissue conduction), (ii) wave transmission through the protection (inertial and compressive piston effects), and (iii) leakage. The contributions of each factor depend on the ear’s mechanical properties, the HPD characteristics, and its proper wearing. The contributions of these phenomena can be isolated over time for high-level impulsive sounds. An experimental protocol using an artificial head, a laser vibrometer, and explosive charges was employed to study the relationship between the displacement of earplugs and the resulting ear canal pressure during impulses ranging from 167 to 180 dB-peak. Measurements were made with two earplugs of different hardness. Besides, the study also has considered the effect of head tilting and has used a novel signal processing method to determine the pure delay of tissue conduction transmission. Differences between configurations and insights from an analytical piston effect model have led to hypotheses about the dominant factors in various scenarios and have paved the way for improving HPDs.