Prediction of airborne and structure borne sound transmission through hearing protectors using FEM

Individual hearing protection is a short term solution frequently used to protect workers against noise exposure. This work is part of a larger research program on the evaluation of real world attenuation of hearing protection devices (HPD) such as earplugs and earmuffs. Its objective is to develop a Finite Element (FE) model to predict both the airborne and structure borne sound transmission through an ear canal/hearing protector system. The model can help providing a better understanding of the acoustical behavior of this system and hence help designing better HPD ultimately. FEM can account for realistic ear and hearing protector geometries, materials with complicated physical behavioral laws and complex transmission phenomena through the different coupled domains in particular the tissues surrounding the ear canal. Several comparisons between numerical predictions and experimental results are presented. The sound transmission through the system is investigated using power balances and sensitivity analyses are carried out to identify the key parameters which govern the acoustic behavior of the system. The importance of parameters such as the system geometry, the coupling between the different domains and the loadings is discussed together with the characterization of the physical properties of each domain.