Cartilage conduction hearing-The third sound conduction pathway

Abstract

Hosoi found in 2004 that a clear sound can be heard when a vibration signal is delivered to the aural cartilage from a transducer. This form of signal transmission is referred to as cartilage conduction (CC). Then, we have examined its mechanism, application, and superiority over the well-known air or bone conduction (AC or BC). We have published 11 English articles including JASA by 2016. AC, BC, and CC are distinguishable according to two points, namely, transmission media and movement of the skull bone. The transmission media are sound in AC, vibration in BC and CC. The movements of the bone are immobile in AC and CC, vibrated in BC. The world first CC hearing aids have been completed. It is very useful for the patients who cannot wear regular hearing aids because of atresia of external auditory canals, for example. More useful applications are cell phones and robots. The CC cell phone has a lot of advantage such as 1) easy volume control without button operation, 2) insulation from outer noise and obtaining the best S/N instantly, 3) no sound leakage to outward, 4) clean liquid crystal display, 5) easy to use even with hearing aids, 6) better suited for very small body type cell phone, and all that. There is no disadvantage compared with the regular phone. Various types of cell phone can be realized using CC. For example, wrist watch type, pen type, eye glass type, finger ring type, etc. Also, CC will give the good method to communication between robots and human beings.