Three-dimensional finite element modeling of the human external ear: Simulation study of the bone conduction occlusion effect

A linear three-dimensional (3D) elasto-acoustic finite element model was used to simulate the occlusion effect following mechanical vibration at the mastoid process. The ear canal and the surrounding soft and bony tissues were reconstructed using images of a female cadaver head (Visible Human Project®). The geometrical model was coupled to a 3D earplug model and imported into comsol Multiphysics (COMSOL®, Sweden). The software was used to solve for the sound pressure at the eardrum. Finite element modeling of the human external ear and of the occlusion effect has several qualities that can complement existing measuring and modeling techniques. First, geometrically complex structures such as the external ear can be reconstructed. Second, various material behavioral laws and complex loading can be accounted for. Last, 3D analyses of external ear substructures are possible allowing for the computation of a broad range of acoustic indicators. The model simulates consistent occlusion effects (e.g., insertion depth variability). Comparison with an experimental dataset, kindly provided by Stenfelt and Reinfeldt [Int. J. Audiol. 46, 595-608 (2007)], further demonstrates the model's accuracy. Power balances were used to analyze occlusion effect differences obtained for a silicone earplug and to examine the increase in sound energy when the ear canal is occluded (e.g., high-pass filter removal).