Modal Superposition-Induced Novel Directional Responses in a Low-Damping Biomimetic Microphone for Sound Source Localization

MEMS microphones inspired by the coupled ears of the fly Ormia ochracea have been extensively investigated for miniature, high-accuracy, and low-noise-floor sound source localization (SSL). However, most studies focus on the rocking-mode-dominated bidirectional polar response for SSL while neglecting the omnidirectional response of the bending mode, leaving other directional responses arising from the dual-mode superposition largely unexplored. Therefore, in this paper, based on a low-damping optical beam deflection (OBD) biomimetic microphone with a pronounced bending-mode omnidirectional response, various directional responses arising from the dual-mode superposition are identified and characterized. Both simulation and experimental results demonstrate that, under the dual-mode superposition, the directional responses of the OBD biomimetic microphone transition from the bidirectional polar pattern with asymmetric lobes to the two gradually overlapping circular patterns and eventually to the two nearly completely overlapping circular patterns, and this process is well described by the developed theoretical model. Moreover, we explore the SSL performance of the modal superposition-induced directional responses and demonstrate for the first time that the non-overlapping circular patterns have the same sinusoidal SSL potential as the bidirectional polar responses. This paper advances the understanding of modal superposition-induced directional responses and expands the variety of directional responses available for SSL in biomimetic microphones.