Applying acoustic ray tracing from the full wave equation solution to determine the nonair conduction pathways into the human head.

Abstract

Flight deck crews are subject to high intensity sounds for prolonged periods of time. Even while using current hearing protection devices such as ear plugs, ear muffs, and helmets, hearing loss is still possible. It is likely that this hearing loss is due to the cochlear stimulation through pathways other than the usual air conduction pathways. In order to develop new hearing protection devices to prevent hearing loss due to these nonair conduction pathways, ray tracing from the full wave equation solution is being used to determine and visualize these dominant pathways. Numerical techniques for performing ray tracing are presented along with the validation of the method by comparing with Snell's law. For small changes in sound speed, angle of transmission errors are less than 20%. As the frequency of the incident pulse is increased, these errors are reduced as would be expected. Results of ray tracing performed on simulation data from two concentric fluid spheres as an approximation to the human head are...