The boundary element method (BEM) has been utilized to formulate a three-dimensional math model for the foam earplug-earcanal and earmuff-earcanal systems. The BEM technique consists of transforming the partial differential equation describing the behavior of the unknowns, inside and on the boundary of the domain, into an integral equation relating only boundary values. In representing the viscoelastic properties of the foam earplug, both integer differential operator and fractional operator constitutive equations were utilized. The BEM model was then utilized to study the steady-state and transient responses (including the prediction of each system's insertion loss) for different earplug-earcanal and earmuff-earcanal configurations. The basic BEM model has demonstrated the ability to predict the internal resonances for a production earmuff shell-earcanal system and the measured insertion loss of a foam earplug-earcanal system subjected to an impulse. Together with these findings a general discussion of the need for improvements in the ability to model a variety of earplug- and earmuff-earcanal configurations will be presented.
The subject of this investigation is the use of the boundary element method (BEM) to predict the steady-state and transient response of a plugged acoustic cavity to externa• excitation. The plug is an elastodynamic material subject to external excitation. The excitation of the plug is transmitted to the acoustic cavity. No internal sources of excitation are considered. A three-dimensional BEM model is developed for the analysis, both for the fluid in the cavity and the elastodynamic material in contact with it. Transient response is determined by recovering the time domain response from the Laplace transform domain solution using an FFT-based inversion scheme. Steady-state response is obtained from
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