Noise levels in modern industrial and military environments are constantly increasing, requiring the improvement of current hearing protection devices. The improvement of passive hearing protection devices lies in examining the performance of major contributors to reduction of noise attenuation. The finite element method can be used to fully explore single hearing protection (SHP) and double hearing protection (DHP) systems, and the major performance mechanisms can be observed numerically as well as visually in modern postprocessing software.

This thesis focuses on developing and evaluating double hearing protection finite element models, and exploring the behavior mechanisms responsible for reduced noise attenuation. The double hearing protection model studied consists of an earmuff preloaded to a barrier covered to simulate human flesh, and a foam earplug installed inside a rigid cylinder designed to simulate the human ear canal. Pressure readings are taken at the bottom of the simulated ear canal assembly. Advanced finite element models are used to reconcile differences between the experimental and finite element results, and to investigate the behavior of the modeled system.

The foam earplug material properties for the finite element model are required in the same shear state of stress and boundary condition configuration as the experimental DHP setup, therefore a novel material extraction method is used to obtain this data. The effects of radial compression preload on the earplugs are considered, and the resulting foam earplug shear material properties are input into the finite element DHP model where the effects of the updated foam material properties are observed.