Sensitivity and Fidelity of a Novel Piezoelectric Middle Ear Transducer

Abstract

Objective: A novel implantable piezoelectric transducer has been developed in this laboratory. The transfer functions of the transducer were assessed in anesthetized acutely implanted cats, and were compared with the microphone of a cochlear implant’s speech processor. Methods: The piezoelectric transducer was fixed to the head of the malleus of the cat. Pure tone signals of 97 dB SPL ranging from 250 to 8,000 Hz delivered from a loudspeaker placed beside the auricle of the cat were used to vibrate the tympanic membrane. The frequency response of the transducer was measured by monitoring the output signal of the transducer with an oscilloscope. The transfer functions of the transducer were then compared with the standard external microphone receiving the same tonal stimulus. Results: The average sensitivity of the implantable piezoelectric transducer was –38.7 dB re 1 V/Pa at 1,000 Hz. The frequency-response curve of the transducer mirrored that of the external microphone, even with high-frequency stimuli. Conclusion: The implantable piezoelectric transducer developed in this laboratory transmits tonal stimuli with high fidelity.

Energy harvesting for assistive and mobile applications

“…Compared to the conventional piezoelectric actuators discussed in the section “Energy harvesting using dome shaped piezoelectric generator,” they are small in size but can generate higher displacement and force at low voltage. Current applications include autofocusing in cell phone camera, image stabilization in digital still camera, for accurate ejection of precisely shaped ink droplets in inkjet printers and controlling the gram load on a disk drive suspension, mirror/prism positioning ; medical applications such as implantable drug delivery system , orthopedics and audiology . Weber showed that multilayer piezoelectric ceramic elements are capable of eliminating the need for an external voltage boost circuit, thereby allowing for miniaturized size of the motor drive circuitry with higher stored energy density than an electromechanical micromotor and can therefore be one‐tenth the size for equivalent performance.…”

Implantable microphones as an alternative to external microphones for cochlear implants

“…Piezoelectric microphones must be built to precise dimensions to optimise its resonance frequency and sensitivity. Nonetheless, it is not currently possible to have both sufficient sensitivity and a resonant frequency below the range of normal hearing (Chi et al, 2009).…”

“…In a previous temporal bone model, however, it was difficult to avoid the sheet touching the middle ear which led to significantly reduced sensitivity. An alternative method was developed by Chi et al (2009) using a piezoelectric bimorph element microphone implanted on the malleus of cats (Chi et al, 2009). The frequency response curve of the piezoelectric microphone mirrored the standard external microphones but sensitivities were different (-38.7 dB re 1 V/Pa at 1,000 Hz and -1.5dB re 1V/Pa at 1,000Hz respectively).…”

A Consistency Evaluation and Calibration Method for Piezoelectric Transmitters

“…These transducers can be divided into piezoelectric and magnetostrictive transducers according to their materials, and piezoelectric transducer technologies that use piezoelectric effect to detect energy transformation are known to be more mature and useful [2,5,6]. Transducers that transform electric energy into sonic energy are called transmitters, and those that transform sonic energy into electric energy are called receivers.…”