Investigation on the Influence of Actuators Excitation Position on Acoustic Performance of Bone Conduction

To study the effect of the actuator excitation position on the performance of bone conduction (BC) hearing aids, the BC sound transmission mechanism was studied. To facilitate this study, a coupled finite element (FE) model of the human head and the ear was built. First, a series of micro-CT images of a human head was used to establish an FE model of the human head, and the reliability of the model was verified by comparing the model-predicted mechanical impedance of the excitation position and the acceleration response of the promontory with the experimental data. Second, an FE model of the human ear, which consists of the ear canal, the middle ear, and the spiral cochlea incorporating the cochlear third windows, was also established and verified. Then, based on these two FE models, we constructed a coupled FE model of the human head and the ear by coupling the corresponding nodes and applied force excitation at different sites on the model’s head. Finally, through comparative analysis of the dynamic response characteristics of the basilar membrane (BM) in the coupled FE model, the effect of different excitation positions of the actuator on the hearing compensation performance of the BC hearing aid was studied. The results show that the best excitation position for the BC actuator is near the cochlea, especially close to the mastoid. In addition, excitating the human head close to the cochlea would improve the BC performance at low-mid frequencies.