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.
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.
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.