Efficiency Evaluation of Bone Conduction Devices Using Three-Dimensional Finite-Difference Time-Domain Head Model

Abstract

Bone conduction devices that can deliver a sound directly to the inner ear through the skull are roughly classified into three types: direct-drive, skin-drive, and tooth-drive types. In this paper, we develop a three-dimensional (3D) head anatomical model based on the elastic finite-difference time-domain (EFDTD) method and evaluate the propagation efficiency of bone conduction sound (BCS) to the inner ear using the three types of devices. Through the comparison of the excitation positions in the tooth-drive device, we confirmed that the acceleration responses of the inner ear when a back tooth was vibrated were about 20 dB higher than that when a front tooth was vibrated. In addition, by the comparison of direct-drive, skin-drive, and tooth-drive devices, we found that the propagation efficiency of BCS was, in order of increasing efficiency, as follows: direct drive > tooth drive > skin drive.