The use of in-ear devices such as hearing aids or earplugs can be accompanied by an amplification of physiological noises upon their insertion in the earcanal, also called occlusion effect. Classical lumped elements-based prediction models for the occlusion effect consider the source
of this effect solely due to the ear canal walls vibration. In most of these models, the in-ear device is considered as a simple infinite acoustic impedance which modifies the ear canal cavity length and thereby the ear canal walls vibrating surface depending on the insertion depth. The contribution
of the earplug sound radiation to the occlusion effect is not considered as a significant mechanism. However, some authors have recently demonstrated using a finite element (FE) model that the earplug affect the vibration pattern of the ear canal walls but also may play the role of sound source
in the unobstructed ear canal cavity thereby affecting the occlusion effect. In the most sophisticated lumped models, the in-ear device acts additionally as a loading on the ear canal wall which in turn modifies the ear canal free walls vibration. However the skin/in-ear device mechanical
coupling is simplified and the earcanal cavity/in-ear device vibroacoustic coupling is ignored. Other physical effects such as leaks between in-ear device and skin may affect the occlusion effect at low frequencies but this has been rarely tackled in the literature. In this paper, a 2D axisymmetric
FE model of the human open and occluded external ear including or not the presence of leaks is proposed to calculate the occlusion effect induced by earplugs. This model is used to study the influence on the occlusion effect of the various couplings skin/earplug/earcanal cavity for various
insertion depths and leak diameters.
Document Type: Research Article
ÉTS. Montréal, Canada
September 30, 2019
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