Optimization and Performance Evaluation of a Transducer for Bone Conduction Implants

We designed and implemented an electromagnetic transducer for implantable bone conduction hearing aids. The proposed transducer is smaller than previous bone conduction transducers for easy implantation and was designed using high permeability metals to produce large electromagnetic forces. In addition, the number of cantilever beams was changed from two to three to minimize distortion of the transducer, potentially due to twisting of the cantilever beam. The proposed transducer consists of a titanium cover with three screw holes, a metal ring, a circular plate, a vibrational membrane with a three-cantilever structure, a metal plate and cylinder, a permanent magnet, top and bottom coils, and a cylindrical titanium case. The transducer was optimally designed based on analysis of electromagnetic and mechanical vibrations, and the target resonance frequency was derived by controlling the variable elements of the vibrational membrane. The transducer was manufactured based on the results of finite element analysis, and the validity of the design was verified by comparing the results of vibration measurement experiments and a simulation. Finally, to evaluate the performance of the proposed transducer, the transducer was attached to the mastoid of participants and functional near-infrared spectroscopy was used to measure brain activation changes of the auditory cortex due to vibration stimulation.