Research/Multichannel Acoustic Filter Bank

2008-05-04 (日) 23:10:27 (4483d)

Micromechanical Cochlea


Human ear picks up sounds of a particular frequency range by the function of basilar membrane in a cochlea. The geometrical shape of the cochlea serves as cascaded frequency band pass filters, and the hair cells on the basilar membrane detect the oscillation. Here we copy the function of the basilar membrane by using the resonant frequencies of coupled cantilever array.

Mechanical Filtering


Acoustic vibration applied to the higher frequency side is frequency-analyzed while traveling through the backbone. It works as an input device of the hearing aids, speech or speaker recognition system. Device size 5 mm x 5 mm, SOI thickness 5 micron, 16 channels for 1 to 6 kHz, bandwidth ~100Hz each, visually characterized under CCD microscope.


  1. Muneo Harada, Naoki Ikeuchi, Shoichi Fukui, Hiroshi Toshiyoshi, Hiroyuki Fujita, Shigeru Ando, "Micro Mechanical Acoustic Sensor toward Artificial Basilar Membrane Modeling," Trans. IEE Japan, vol.119-E, No.3 (1999) pp.125-130.

Improved Version of MEMS Acoustic Filter Bank


We modified the fishbone structure to make a new version of the sound analyzing device called Micro Harp. It is made of micro bridge array instead of cantilevers. Piezoelectric or piezoresistive sensors are integrated on the beams to detect the vibration. Device size 2 cm x 2 cm, bridge length 1 mm to 10 mm, width 50 micron, SOI thickness 5 micron, ZnO piezoelectric transducer and Cr-Au electrode, ZnO piezoelectric diaphragm for excitation, 40 channel output with offset adjust electrodes.


  1. Markus Mueller, Hiroshi Toshiyoshi, Hiroyuki Fujita, "Acoustic wavelet analysis using micro electro-mechanical sensors," SPIE 1998 Symposium on Micromachining and Microfabrication, 20-22 September, 1998, Santa Clara, California, USA.