Bone conduction earphone using ultrasound vibration

摘要

This article proposes a novel bone conduction earphone based on an interesting phenomenon that audible sound is perceived when the ultrasonic vibration modulated by the sound is given to tragus of a listener. The earphone comprises an amplifier that modulates ultrasound with audible sound signal, and an ultrasonic piezoelectric actuator. The frequency characteristics of the audible sound given by the earphone are examined through a subjective loudness balance test as well as the measurement of the sound in external ear canals of one with normal hearing and the other with hearing difficulties. The results show that the level of the audible sound is in proportion to the power of the frequency. Moreover, the audible sound seems to be produced by the nonlinear demodulation somewhere in the ultrasound transmission from the tragus to the external ear canal.