Necessity of human middle ear characteristics at design of piezoelectric type round window vibrator

A new implantable hearing device, which vibrates round window (RW) of human cochlea, has been widely developed in the world. This device has been remarkable owing to compensate conductive hearing loss of hearing impaired people which was damaged their ossicles. Recently, piezoelectric actuator has been applied to RW drive type hearing devices because of flat and excellent vibrational characteristics at audible frequency range. However, in case of the RW vibration, patients cannot hear natural sound because the auditory pathway don´t include middle ear. And human middle ear has resonant characteristics. Thus, piezoelectric vibrators need the resonance corresponding to the middle ear characteristics for hearing natural sound.