Evaluation of Bone Conduction Vibration System Using Photoacoustic Effect

This article proposes a novel bone conduction vibrator based on an interesting phenomenon where audible sound can be perceived when a vibration is produced using a laser beam that is synchronized to the sound and this vibration is transmitted to an auricular cartilage. To study this phenomenon, we measured the effect using a rubber sheet with similar properties to those of soft tissue, together with an acceleration sensor, and found that audible sound was produced in the sample. We also calculated the force level based on the mechanical impedance and the acceleration in the proposed system. It is expected that a force level equal to the reference equivalent threshold force level can be achieved at a light intensity below the safety limit for human skin exposure by choosing an irradiation wavelength at which a larger degree of optical absorption occurs. This novel application of the photoacoustic effect is promising for bone conduction hearing aids.