Simulation of High-Level Impulse Noise Propagation into the Human Head

Recent data from heavy weapon training environments suggests that protecting the Warfighter from impulse noise exceeding 140 dB may require assessing and mitigating various modes of noise propagation into the head, rather than solely focusing on protecting air conduction through the ear canal. To achieve this, we have developed a finite element (FE) model of the human head, simulating the biomechanical response of the ear to impulse noise. The FE model was generated based on MRI images, detailed geometric representations, and published material models. The head-ear FE model incorporated major ear structural components with NRL high-fidelity head model. The loading conditions were derived from notional weapons firing and/or explosive incidents and used to characterize the biomechanical effects in the ear. Additionally, a detailed cochlea model has been developed and validated to analyze the dynamic behavior of the inner ear when subjected to skull vibration induced by impulse noise. Results from the simulations highlight differences in sound transmission between bone conduction and air conduction pathways. The protective function of the temporal bone against impulse noise has been quantified. The pressure responses in the brain and the inner ear have been compared with experimental data obtained from shock tube testing. By examining the simulated motion of the basilar membrane, we established a relationship between impulse noise and the auditory risk probability of the inner ear. This work represents the first attempt to dissect multiple transmission modes, such as air conduction (or through the ear canal) and bone conduction, shedding light on how impulse noise affects the biomechanical responses of sensitive inner ear organs