Validation using the in vivo experiment of the 3D model of the human ear using the equivalent mechanical impedance of the Mass-Spring-Damper System

Abstract

The ear can be defined as the organ responsible for auditory perception. Its role among others is to amplify, transmit and convert an acoustic wave, presents in the environment, into an electrical pulse that can be interpreted by the brain via the auditory nerve. The conductive hearing loss is a major public health problem; it is related to a malfunction of the outer or middle ear leading to an interruption of the propagation of the sound wave within the hearing organ. Conductive deafness is caused by impulse noise which is present in a large number of professional sectors; many professions and/or sectors of activity are therefore concerned. There are two primary aims of this study: (1) to realize a 3D model of the human ear in order to characterize the impulse noise and evaluate its auditory risks in professional environments so as to identify the means of protecting the ear; (2) to carry out a comparison between the results obtained numerically using our 3D model and those obtained from experimental tests. The 3D model of the human ear was realized using the COMSOL multiphysics software. The structure–acoustic interaction between the auditory canal, which will be considered as the propagation field of the acoustic wave, and the structures of the ear (eardrum, skin, bone, cartilage) have been solved using the Finite Element Method (FEM). For the modeling, the ossicles, the cochlea and the middle ear were replaced by a Mass-Spring-Damper System (MSDS). The results obtained from the 3D modeling show that the maximum displacements of the eardrum are in the frequency range of [1700, 2600] Hz. A peak on the sound pressure gain results around 3000 Hz was observed. The change in the damping coefficient d has a strong influence on the displacement of the eardrum. A grow of the acoustic pressure honest the eardrum compared to that recorded at the entrance of the auditory canal is noted. These results were validated by the results of experiments carried out in vivo.