Fluid-Structure Interaction Analysis of Trapezoidal and Arc-Shaped Membranes Mimicking the Organ of Corti.

In a previous study [H. Shintaku et al., Sensors and Actuators A: Physical 158 (2010): 183-192], an artificially developed auditory sensor device showed a frequency selectivity in the range from 6.6 to 19.8 kHz in air and from 1.4 to 4.9 kHz in liquid. Furthermore, the sensor succeeded in obtaining auditory brain-stem responses in deafened guinea pigs [T. Inaoka et al., Proceedings of the National Academy of Sciences of the United States of America 108 (2011): 18390-18395]. Since then, several research groups have developed piezoelectric auditory devices that have the capability of acoustic/electric conversion. However, the piezoelectric devices are required to be optimally designed with respect to the frequency range in liquids. In the present study, focusing on the trapezoidal shape of the piezoelectric membrane, the vibration characteristics are numerically and experimentally investigated. In the numerical analysis, solving a three-dimensional fluid-structure interaction problem, resonant frequencies of the trapezoidal membrane are evaluated. Herein, Young's modulus of the membrane, which is made of polyvinylidene difluoride and is different from that of bulk, is properly determined to reproduce the experimental results measured in air. Using the modified elastic modulus for the membrane, the vibration modes and resonant frequencies in liquid are in good agreement with experimental results. It is also found that the resonant characteristics of the artificial basilar membrane for guinea pigs are quantitatively reproduced, considering the fluid-structure interaction. The present numerical method predicts experimental results and is available to improve the frequency selectivity of the piezoelectric membranes for artificial cochlear devices.