Bone conduction (or bone conduction) is a mechanism for hearing sound that propagates inside the body (cranium, middle ear, inner ear, etc.).On the other hand, air conduction (or air conduction) is the mechanism of listening to sound that is transmitted to the eardrum through the external auditory canal as air vibrations from the outside.Bone conduction headphones are attracting attention as one of wearable devices.However, although bone-conducted sound is not easily affected by ambient noise, the sound quality and speech intelligibility are lower when listening with bone-conduction headphones than when listening with air conduction.

　In this study, we focused on two types of observable bone-conducted sound (temporal vibration and sound emitted from the ear canal) and measured their transfer characteristics. was attenuating.Therefore, we developed a high-frequency emphasis processing method to pre-compensate for the frequency characteristics of the audio signal input to the bone conduction device by using the inverse characteristics that act on the two types of bone conduction characteristics.This effectively improved the intelligibility of bone conduction presentation speech even in a noisy environment.

　This research is a joint research with WestUnitis Co., Ltd., which develops and manufactures industrial wearable devices.This result has been adopted for bone conduction technology in industrial smart glasses developed by the company.In the future, in addition to applying it to wearable devices, we plan to expand it to apply it to hearing aid technology using bone conduction and to expand it as a voice communication device at disaster sites (high-noise environments).

Paper information:【Applied Acoustics】Methods for improving word intelligibility of bone-conducted speech by using bone-conduction headphones