An optical beam deflection based MEMS biomimetic microphone for wide-range sound source localization

Abstract

Miniature microphones inspired by the ears of the parasitic fly Ormia Ochracea are an important means to overcome the fundamental size constraint of microphone arrays for sound source localization (SSL). However, the signal demodulation performance and the SSL range of the biomimetic microphones need to be improved. This study aims to develop a miniature biomimetic microphone with good signal demodulation capability and wide SSL range. Specifically, in this paper, an optical beam deflection (OBD) demodulation system was designed and combined with a micro-electro-mechanical system omimetic diaphragm to form a miniature microphone for SSL. The OBD-based biomimetic microphone shows many merits in signal demodulation, including low noise floor (⩽−110 dB), high repeatability of sound pressure measurement, and linear temperature response. The theoretical and experimental results demonstrated that the two wings of the biomimetic microphone have the bi-directional polar patterns with different sizes of lobes at the rocking-mode eigenfrequency, and have omnidirectional response at the bending-mode eigenfrequency. Furthermore, a new SSL method was proposed, which effectively extends the SSL range of the biomimetic microphone at the rocking-mode eigenfrequency to ±90° by combining the interaural intensity difference between the two wings. The proposed OBD-based biomimetic microphone not only has the advantages of small volume and low power consumption, but also has the stable and wide-range SSL capability, which shows that it has a great prospect in the practical applications of SSL, such as wearable devices and rescue robots, etc.