The frequency response of a floating piezoelectric microphone for the implantable middle ear microphone.

OBJECTIVES/HYPOTHESIS A piezoelectric sensor, floating piezoelectric microphone, driven by acoustic vibration of the ossicles, is one possible design for a microphone for a totally implantable cochlear implant. The purpose of the article was to study the frequency response of the floating piezoelectric microphone and to identify the ideal feasible position in the ossicular chain. STUDY DESIGN Basic Research. METHODS The frequency response of the floating piezoelectric microphone was analyzed by finite-element modeling and in vitro testing of fresh cadaveric heads. The floating piezoelectric microphone, 5.0 mm in length and 1.5 mm by 1.2 mm in rectangular cross section, as a piezoelectric microphone, was placed at various locations on the ossicular chain and stimulated by pure tones of different frequencies. RESULTS The floating piezoelectric microphone can pick up the vibration of the ossicular chain and effectively convert it into the electronic signals effectively both in the long process of incus and in the malleus. The average sensitivity of the FPM is -44.22 dB rms ref 1V at 1000 Hz in the long process of incus, -53.33 dB rms ref 1V at 1000 Hz in the malleus, and -108.59 dB rms ref 1V at 1000 Hz in the tympanic cavity. CONCLUSIONS The floating piezoelectric microphone is expected to be used as an implantable middle ear microphone for the totally implantable cochlear implant.