A finite element model to predict the sound attenuation of earplugs in an acoustical test fixture.

Abstract

Acoustical test fixtures (ATFs) are currently used to measure the attenuation of the earplugs. Several authors pointed out that the presence of an artificial skin layer inside the cylindrical ear canal of the ATFs strongly influenced the attenuation measurements. In this paper, this role is investigated via a 2D axisymmetric finite element model of a silicon earplug coupled to an artificial skin. The model is solved using COMSOL Multiphysics (COMSOL(®), Sweden) and validated experimentally. The model is exploited thereafter to better understand the role of each part of the earplug/ear canal system and how the energy circulates within the domains. This is investigated by calculating power balances and by representing the mechanical and acoustical fluxes in the system. The important dissipative role of the artificial skin is underlined and its contribution as a sound transmission pathway is quantified. In addition, the influence of both the earplug and the artificial skin parameters is assessed via sensitivities analyses performed on the model.