The mechanisms of blast-induced hearing loss are still not well understood. We used an integrated modeling and experimental approach to investigate the bone conducted impulse noise transmission into the inner ear and to gain insight into the fundamental mechanisms. One important question to address is how a small air bubble in the fluid near the inner ear wall, as observed in the experiment, affects the inner ear pressure when the head is exposed to blast overpressure. Understanding this effect can help develop strategies to prevent air bubbles from forming in the fluid and improve the performance of experiments. A head surrogate was designed to quantify the pressure wave and noise propagation into the inner ear. This instrumented head was exposed to impulse noise generated by a shock tube to identify the role of bone conduction in pressure buildup in the inner ear. We have developed a corresponding finite element (FE) model of the head surrogate to simulate the biomechanical response of inner ear to impulse noise. The sub-millimeter air bubble trapped in the fluid was explicitly modeled using a local refined mesh around the inner ear. The appropriate material models for skull bone, brain tissue and air and fluid in the inner ear and the loading condition derived from the recorded incident data were used to characterize the biomechanical effects in the inner ear. By evaluating the pressure changes in the inner ear, we assessed the effects of impulse noise propagation into both the inner ear and the brain through the skull bone. We simulated the effect of air bubbles on pressure transmission by varying the size and location of the air bubble in the inner ear fluid. It was found that the air bubble plays an important role in inner ear pressure, compared to the model without air bubble in the fluid. An air bubble that is a few percent of the inner ear’s length can notably reduce the pressure and cause pressure oscillations in the inner ear fluid.
2025-04-09 09:00:00
