A low-frequency dual-band operational microphone mimicking the hearing property of Ormia ochracea

Zhang, Y., Bauer, R., Jackson, J. C., Whitmer, W. M. , Windmill, J. F.C. and Uttamchandani, D. (2018) A low-frequency dual-band operational microphone mimicking the hearing property of Ormia ochracea. Journal of Microelectromechanical Systems, 27(4), pp. 667-676. (doi: 10.1109/JMEMS.2018.2845680)

Abstract

This paper introduces a directional MEMS microphone designed for hearing aid applications appropriate to low-frequency hearing impairment, inspired by the hearing mechanism of a fly, the female Ormia ochracea. It uses both piezoelectric and capacitive sensing schemes. In order to obtain a high sensitivity at low frequency bands, the presented microphone is designed to have two resonance frequencies below the threshold of low-frequency hearing loss at approximately 2 kHz. One is around 500 Hz and the other is slightly above 2 kHz. The novel dual sensing mechanism allows for optimization of the microphone sensitivity at both frequencies, with a maximum open-circuit (excluding pre-amplification) acoustic response captured via differential piezoelectric sensing at approximately -46 dB (V) ref. 94 dB (SPL) at the resonance frequencies. The corresponding minimum detectable sound pressure level is just below -12 dB. The comb finger capacitive sensing was employed due to a lower electrical response generated from a ground referenced single-ended output by the piezoelectric sensing at the first resonance frequency compared with the second resonance frequency. The capacitive sensing mechanism, connected to a charge amplifier, generates a -28.4 dB (V) ref. 94 dB (SPL) acoustic response when the device is excited at either of the two resonance frequencies. Due to the asymmetric geometry and the 400 μm thick substrate, the device is predicted to perform as a bi-directional microphone below 3 kHz, which is shown by the measured directional polar patterns.

• Item Type: Articles
• Additional Information: This work was supported in part by the EPSRC under Grant EP/M026701/1 and in part by the European Research Coun- cil through the European Union’s Seventh Framework Programme under Grant FP/2007-2013 and ERC under Grant 615030.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Windmill, Professor James and Jackson, Mr Joseph and Whitmer, Dr William
• Authors: Zhang, Y., Bauer, R., Jackson, J. C., Whitmer, W. M., Windmill, J. F.C., and Uttamchandani, D.
• College/School: College of Medical Veterinary and Life Sciences; College of Science and Engineering > School of Engineering
• Journal Name: Journal of Microelectromechanical Systems
• Publisher: IEEE
• ISSN: 1057-7157
• ISSN (Online): 1941-0158
• Published Online: 20 June 2018
• Copyright Holders: Copyright © 2018 The Authors
• First Published: First published in Journal of Microelectromechanical Systems 27(4): 667-676
• Publisher Policy: Reproduced under a Creative Commons License