Researches for practical use of the ultra sound hearing system for profoundly hearing impaired patients and auditory mechanism of ultra sound

虽然我们听不到20 kHz以上的超声波，但该频率的振动可以通过骨传导（骨传导超声）引起听觉。有趣的是，骨导超声也可以对完全听不到声音的重度听力障碍患者产生听觉。利用这一现象，我们研制了骨导超声助听器。本研究主要解决了（1）超声感知机制的定义和（2）骨导超声助听器的实际实现两个难题，阐明了外周和中枢听觉通路的机制;例如，外围感知器官位于耳蜗的基回，感知器官不是对转换后的可听声音作出反应，而是对超声波本身作出反应，此时外毛细胞不工作。此外，助听器的实际研究可以发现，调幅超声在语言中可以表达韵律（语调），使用助听器进行康复可以提高言语清晰度。

Although we can not hear ultra sound above 20 kHz, the vibration in the frequency can induce auditory sensation through the bone conduction (bone-conducted ultrasound). And it is interesting that the bone-conducted ultrasound can induce auditory sensation also for profoundly hearing impaired patients who can not hear sound absolutely. Using this phenomenon, we have developed the bone-conducted ultrasound hearing aid. In this study, we addressed two challenges such as(1) definition of the mechanism of ultrasound perceptionand (2) practical realization of the bone-conducted ultrasound hearing aid.As results, the mechanisms on the peripheral and central auditory pathways were clarified; for examples, that the peripheral perceptual organs are located in the basal turn of the cochlea, the perceptual organs respond not to the transformed audible sound but to the ultrasound itself, and the outer hair cells does not work at that time. Moreover, practical researches of the hearing aid could found that the amplitude-modulated ultrasound in language can express the prosody (intonation) and the rehabilitation using the hearing aid can improve the speech intelligibility.