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Proceedings Paper

MEMS direction finding acoustic sensor
Author(s): Gamani Karunasiri; Fabio Alves; William Swan
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Paper Abstract

Conventional directional sound sensing systems employ an array of spatially separated microphones to achieve directivity. However, there are insects such as the Ormia ochracea fly that can determine the direction of sound using a miniature hearing organ much smaller than the wavelength of sound it detects. The fly's eardrums are coupled mechanically with a separation of only 0.5 mm and yet have a remarkable sensitivity to the direction of sound. The MEMS based sensor mimicking the fly’s hearing system was fabricated using an SOI substrate with a 25 μm device layer. The sensor consists of two 1.5 mm x1.6 mm wings connected in the middle by a 2.7 mm x 30 μm bridge. The entire structure is connected to the substrate by two torsional legs at the center. The frequency response of the sensor showed two resonance frequencies at approximately 1.1 kHz (rocking) and 1.5 kHz (bending). The resonance at 1.1 kHz is due to rocking of the wings by twisting the legs and the other at 1.5 kHz is due to bending of the bridge. The response of the sensor was probed electronically using comb finger capacitors integrated to the edges of the wings and with the help of an MS3110 chip. A peak output voltage of about 9V/Pa was measured for sound incident normal to the device at the resonance frequency of the bending mode. The bearing of the incident sound under these conditions could be determined to within a few degrees. These findings indicate the potential use of the MEMS sensor to locate sound sources with high accuracy.

Paper Details

Date Published: 2 June 2017
PDF: 6 pages
Proc. SPIE 10246, Smart Sensors, Actuators, and MEMS VIII, 102460I (2 June 2017); doi: 10.1117/12.2264952
Show Author Affiliations
Gamani Karunasiri, Naval Postgraduate School (United States)
Fabio Alves, Naval Postgraduate School (United States)
William Swan, Naval Postgraduate School (United States)

Published in SPIE Proceedings Vol. 10246:
Smart Sensors, Actuators, and MEMS VIII
Luis Fonseca; Mika Prunnila; Erwin Peiner, Editor(s)

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