Abstract

The influence of custom microphone housings on the acoustic directionality and frequency response of a multi-band bio-inspired MEMS microphone is presented. The 3.2 mm by 1.7 mm piezoelectric MEMS microphone, fabricated by a cost-effective multi-user process, has four frequency bands of operation below 10 kHz, with a desired first-order directionality for all four bands. $7\times 7\times 2.5$ mm $^{3}~3$ -D-printed bespoke housings with varying acoustic access to the backside of the microphone membrane are investigated through simulation and experiment with respect to their influence on the directionality and frequency response to sound stimulus. Results show a clear link between directionality and acoustic access to the back cavity of the microphone. Furthermore, there was a change in direction of the first-order directionality with reduced height in this back cavity acoustic access. The required configuration for creating an identical directionality for all four frequency bands is investigated along with the influence of reducing the symmetry of the acoustic back cavity access. This paper highlights the overall requirement of considering housing geometries and their influence on acoustic behavior for bio-inspired directional microphones.

Highlights

  • T HE use of directional sound receivers for sound source localization or improvement of hearing aid technologies through suppression of unwanted sound sources is a research topic with strong biomedical, entertainment and defense industry interest, with solutions depending on signal processing approaches or specialized mechanical microphone designs

  • In our previous work [15] we have shown the expansion from 2 movement modes to multi-band operation with the inclusion of multiple membranes set inside each other, with all operation frequency bands below 15 kHz

  • A bio-inspired directional Microelectromechanical Systems (MEMS) multi-band microphone based on the hearing mechanism of the fly Ormia ochracea was presented together with the influence of the microphone housing geometry on its frequency response and directionality

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Summary

Introduction

T HE use of directional sound receivers for sound source localization or improvement of hearing aid technologies through suppression of unwanted sound sources is a research topic with strong biomedical, entertainment and defense industry interest, with solutions depending on signal processing approaches or specialized mechanical microphone designs. Current commercially available products rely on multiple. Manuscript received May 26, 2017; accepted July 17, 2017. Date of publication July 20, 2017; date of current version August 9, 2017. Union’s Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement n. The associate editor coordinating the review of this paper and approving it for publication was Dr Stefan J.

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