Abstract
Earplugs are a frequently used short-term solution for hearing conservation in the workplace environment. Due to limited auditory comfort, however, workers often only wear them for short periods of time and become prone to hearing loss. An important source of discomfort is the auditory occlusion effect, which expresses itself through the distortion of the wearer's voice and the amplification of physiological noises upon earplug insertion. Simplified numerical modeling can help to better assess and design earplugs, because it requires few system resources and is simpler in terms of numerical and experimental implementation than an equivalent complex model. This work describes a novel coupled linear elasto-acoustic two dimensional finite element (FE) model of the human outer ear. The model comprises the auditory canal as well as the bony, cartilaginous, and skin tissues whose material parameters were approximated using literature findings. The outlined model can compute the transfer functions between the sound pressure levels at the eardrum and a structure-borne excitation for both an unoccluded ear and an ear occluded by a molded earplug. Simulated occlusion effects are examined as a function of excitation, earplug, and insertion depth. Predicted model results are compared to literature findings and to findings obtained from an equivalent three dimensional FE-model.
Published Version
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