Naoki Ikeuchi

Fish-bone-structured acoustic sensor toward silicon cochlear systems

This paper describes a micro mechanical acoustic sensor modeling the basilar membrane of the human cochlea. The skeleton of the acoustic sensor is an array of resonators each of specific frequency selectivity. The mechanical structure of the sensor is designed using FEM analysis to have a particular geometrical structure looking like a fish bone that consists of cantilever ribs extending out from a backbone. Acoustic wave is supposed to be introduced to the diaphragm placed at one end of the backbone to travel in one way along the backbone. During traveling each frequency component of the wave is delivered to the corresponding cantilever according to its resonant frequency. The mechanical vibrations of each cantilever are detected in parallel by use of piezoresistors. The fish-bone structure is fabricated to be suspended in the air on a silicon substrate using silicon micromachining technology. We observe the frequency response of each cantilever to verify fairly sharp frequency selectivity associated with the one- way flow of the vibration energy. The present results encourage us to implement the human auditory system on a silicon chip toward the goal of silicon cochlea.

Silicon Cochlear Michrophone "Fishbone" with Complex Filtering and Hilbert Transform Capability for Instantaneous Signal Detection and Analysis

We have been studying on the cochlear mechanism as an efficient structure for sensors and actuators [3], [4], [5], The Fishbone has a silicon micromachinable shape derived from the electro-mechanical analogy of the Zwislockis transmission line modelfl], [2], We propose here a novel transduction method being suitable for single- chip and wireless acoustic/vibrometric sensor. It has digitally adjustable complex frequency characteristics, radio- frequency (RF) outputs with direct modulation on resonant beams, and Hilbert transform capability to produce real and imaginary signal pair after quadrature-demodulating the RF output. We show theoretical analysis and experimental results using a newly fabricated Fishbone chip.