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

Abstract

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).

Inner ear contribution to bone conduction hearing in the human

“…A more comprehensive finite element model of the middle ear for BC was presented by Homma et al (2009). The occlusion effect have been investigated by both lumped element models (Schroeter et al, 1986;Stenfelt et al, 2007) and finite element models (Brummund et al, 2014). The most comprehensive work of a finite element model of a whole human head was presented by Taschke et al (2006).…”

Model predictions for bone conduction perception in the human

“…One way to circumvent this problem is to use a model that can simulate BC excitation. Several such models have been devised to investigate a specific aspect of BC stimulation, for example the occlusion effect (Brummund et al, 2014;Schroeter et al, 1986;Stenfelt et al, 2007), middle ear inertia (Homma et al, 2009;Williams et al, 1990), and inner ear fluid inertia and compression (Bohnke et al, 2006;Kim et al, 2011;Schick, 1991;Stenfelt, 2015). These models are often specific meaning they only investigate a single or a couple of phenomena and not the complete response of the ear to BC stimulation.…”

Investigation of the variability in earplugs sound attenuation measurements using a finite element model

“…geometrical variations of the EC have been frequently mentioned as a factor that can affect the sound pressure level (SPL) in both the open EC [25] and the occluded EC [11,31]. The inter-individual variability of the dynamic properties of the EC tissues can also result in SPL variations in the EC [12,8]. Even if these factors are frequently reported in the literature to qualitatively explain the variation of the EP attenuation measurements, their precise impacts on the attenuation have never been investigated and quantified separately.…”

“…In Viallet et al [29], the authors accounted for the biological tissues surrounding the ear canal via a mechanical boundary impedance condition but did not take into account the part of the incident acoustic energy which could flow directly through the skin into the unoccluded part of the EC. The geometrical reconstruction of an individual EC including the surrounding tissues is a difficult and highly time consuming process (see [8,22]). In recent works [32], a 2D axisymmetric model of the silicone-lined EC to mimic the effect of the skin was developed to study the effect of the artificial skin present in the available ATF.…”