Piezoelectric floating mass transducer for implantable middle ear hearing devices

A simple piezoelectric floating mass transducer (PFMT) for implantable middle ear hearing devices (IMEHDs) is studied. The transducer that is implanted in the middle ear consists of a PMN-PT multi-layered piezoelectric actuator and a metal case. The proposed PFMT can be attached to the long process of the incus using a metal clamp, and vibrates the ossicular chain according to the force originating from the expansion and contraction of the piezoelectric actuator. This chapter presents the design and an evaluation of the proposed PFMT as a new type of vibrating transducer. The design factors considered include the dimensions, generated force, weight, power consumption, and time-frequency characteristics. An in vitro experiment using a human temporal bone confirms that the PFMT excitation at 10 V_PP can generate vibration displacements equivalent to a sound pressure of about 94 dB SPL below 1 kHz and about 140 dB SPL at 8 kHz. The power consumption of the PFMT to produce a sound stimulation equivalent to 94 dB SPL is 65 μW at 1 kHz. Therefore, the proposed PFMT is expected to be useful as an IMEHD transducer with the advantages of simple surgical implantation, no interference from external electromagnetic fields, and improved productivity.