An axisymmetric linear elasto-acoustic finite element (FE) model of an occluded human external ear is proposed to simulate the bone conduction occlusion effect (OE). The model consists of a cylindrical ear canal cavity surrounded by layers of biological tissues (skin, cartilage and bone) in which an earplug is inserted. Geometrical and material properties are taken from the literature. OEs are predicted for foam and silicone earplug FE-models using COMSOL Multiphysics (COMSOL®, Sweden). The FE-model is shown to predict the experimental OE measured in two healthy human reference groups wearing foam or silicone earplugs, satisfactorily. Deviations between model and experiment are of similar magnitudes as for previous electro-acoustical OE models. Comparison of the axisymmetric FE-model with two existing gold standard electro-acoustical OE models showed (i) minor differences for shallow occlusion and (ii) a large underestimation for frequencies < 1 kHz, but a good agreement above 1 kHz, for deep insertion. OE differences between silicone and foam earplug types (similar insertion depths, close to bony meatus) were observed experimentally and confirmed with the FE-model. Power balance computations in the ear canal and the earplug (both FE-models) indicate an insertion depth dependent contribution of the earplug type to the OE magnitude.
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Brummund et al. (2015) studied this question.