Exploring the impact of force direction and phase on bone conduction hearing with bone conduction actuator.

A comprehensive understanding of the effects of bone conduction (BC) input force is essential for elucidating BC hearing mechanisms. However, this area remains underexplored due to the inherent difficulties in controlling input forces when BC transducers are anchored to the bone. In this study, the effects of both unilateral and bilateral BC input forces were investigated using a three-dimensional finite element (FE) model of the human head, which allows precise manipulation of input forces. For unilateral input, 16 distinct directions were created by combining eight in-plane vectors with two tilt angles based on the normal direction of the input force location, and the resulting promontory velocities were compared. Although the magnitude differences between input directions remained within 10 dB, anti-resonance shifts were observed between 1 and 3 kHz. In the bilateral case, phase differences of 0°, 90°, and 180° were applied between input forces at the right and left mastoid positions, and basilar membrane velocities were compared to examine the complex interactions between input forces. These findings provide deeper insights into the effects of input force direction and phase on BC hearing, advancing the understanding of BC hearing mechanisms.