Influence of the external ear tissue domains on the sound attenuation of an earplug predicted by a finite element model

Earplugs are a widespread solution to prevent the problem of hearing loss in the workplace environment, but they do not always perform as desired. Using a model of the ear canal occluded by an earplug could be helpful to perform sensitivity analyses (geometry and materials of the earplug) and to better understand the role of the earplug. The human external ear is a complex system made up of different tissues with a 3D geometry. In practice, it is reduced to a 2D cylindrical geometry for the acoustical tests fixtures. The purpose of this study is to compare the insertion loss predicted by a 3D complex finite element model of the ear canal surrounded by different tissue domains (skin, soft tissue, and bone) and occluded by a silicon earplug versus a 2D axisymmetric model of the same system. In both models, some investigations are made in order to verify if the models could be simplified by replacing the tissue domains by mechanical impedances. These investigations are made to reduce the complexity of the models and to discuss the relevance of whether or not including external ear tissue domains in a sound attenuation model of an earplug.