Acoustic Boundary Layer Attenuation in Ducts With Rigid and Elastic Walls Applied to Cochlear Mechanics

Abstract

The cochlea is the most important part of the hearing system, due to the fact that it transforms sound guided through air, bone, and lymphatic fluid to vibrations of the cochlear partition which includes the organ of Corti with its sensory cells. These send nerve impulses to the brain leading to hearing perception. The work presents the wave propagation in rigid ducts filled with air or water including viscous-thermal boundary layer damping. In extension, a mechanical box model of the human cochlea represented by a rectangular duct limited by the tapered basilar membrane at one side is developed and evaluated numerically by the finite element method. The results match with rare experiments on human temporal bones without using the physically unfounded assumption of Rayleigh damping. A forecast on the concept of the traveling wave parametric amplification is given to potentially explain the high hearing sensitivity and otoacoustic emissions.