Abstract. This paper presents the analysis and discussion about different effects of the external auditory canal (EAC) geometry on the response of the human hearing system. Simulation has been made by means of 3D finite element models which included EAC and a model of the ossiculareardrum system. Different EAC geometries were constructed, coupled to a middle ear model validated in previous works. The EAC geometry is based on anatomical measurements taken from the literature. The relative position and orientation of the tympanic membrane and section reduction of the canal at the isthmus were studied and analyzed with a harmonic analysis. A sound pressure level of 90 dB was applied at the canal entrance and through fluid-structure coupling, the pressures in the umbo and the displacements of umbo and stapes footplate were measured in a frequency range from 100 Hz to 20000 Hz.
The pressure gain distribution along the ear canal is strongly dependent on boundary conditions, and, in normal conditions, the ear canal produces a 0–20-dB pressure gain close to the tympanic membrane in the 0.1–20[Formula: see text]kHz range. Additionally, the pressure gain distribution along the ear canal at high frequencies (over the second resonance of the ear canal at 8–9[Formula: see text]kHz) depends strongly on axis position; therefore, the middle ear transfer functions based on ear canal pressure are also strongly dependent on the measuring point. Objective: The aim of this study is to evaluate the mechanical influence of the tympanic cavity, ossicular chain and tympanic membrane connections on the pressure in the ear canal in the frequency range of 0.1–20[Formula: see text]kHz when a pressure source is applied to the ear canal entrance. Methods: We have developed numerical simulations for seven different models using the finite element method (FEM). Starting with an external ear canal finite element model, additional elements are coupled or removed to evaluate their contributions. We modeled and simulated the tympanic membrane, ossicular chain, tympanic cavity and a simplified cochlea in seven different combinations. Results: The pressure distribution along the external ear canal is obtained and represented in the 0.1–20[Formula: see text]kHz range for the seven model configurations.
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