Simulation and Experimental Validation of Alternate Pathways of Impulse Noise Conduction Into the Inner Ear

Abstract

Abstract Recent data from heavy weapons training and breaching exercise environments suggest that protection of the ear canal alone may not be sufficient to prevent detrimental effects of blast-induced impulse noise on the Warfighter. This work is to elucidate alternate pathways of impulse noise penetration into the inner ear, including through the soft tissues of the head and bone conduction, gain insight into the fundamental mechanism(s) of blast induced hearing loss and validate the computational model with experiment. We have exposed the instrumented head model to impulse noise events generated via a shock tube (sound pressure level > 140 dB) to identify the role of bone conduction in pressure build up in the inner ear. Concurrently, we have developed a finite element (FE) model of the head to simulate the biomechanical response of the ear to impulse noise. The loading condition applied to the model to characterize the biomechanical effects in the ear is derived from notional weapons firing incidents. We have also developed an inner ear model to analyze the dynamic behavior of the basilar membrane when subjected to skull vibration stimulated by an impulse noise event. Using the simulated motion of the basilar membrane, we attempted to establish the relationship between the impulse noise and possible auditory disruption outcomes to the inner ear.