半植込型人工中耳
―その原理と聴力評価法―
1987 年 80 巻 12 号 p. 1819-1825
詳細
1987 年 80 巻 12 号 p. 1819-1825
The function of the partially implantable hearing aid depends upon direct driving of the stapes by the piezoelectric ceramic bimorph element. Acoustic signals from a microphone are transmitted to the vibrator element by means of electromagnetic induction. Prior to utilizing the device, it was necessary to develop a method of assessing hearing induced by the device. During middle ear surgery, the element was attached to the stapes, and excited by the pure tone output signal of an audiometer. The threshold of hearing thus determined was termed vibratory hearing threshold. This value was converted into dB SPL at the ear drum. From this value we can obtain the expected hearing threshold afforded by the device. Instead of a microphone in the external unit, an appropriate resistance is incorporated in order to excite the internal unit by signals from the audiometer. With this system, the actual hearing threshold afforded by the device could be measured. Our data confirmed that the device was applicable and that the system was useful for the assessment of postimplant hearing.
