Fast Demodulated White-Light Interferometry-Based Measurement and Theoretical Verification of Mechanical Sensitivity of MEMS Biomimetic Microphone With Fiber-Optic Fabry-Pérot Interferometer

MEMS microphones inspired by the coupled ears of the fly Ormia ochracea have been extensively studied to achieve miniaturization of sound source localization (SSL). However, the SSL of all current biomimetic microphones relies on the electrical signals converted from the directional vibration of the biomimetic diaphragms. Consequently, only the electrical performance of the biomimetic microphones under sound pressure excitation (i.e., electrical sensitivity mV/Pa) has been characterized, whereas the mechanical performance (i.e., mechanical sensitivity nm/Pa) has not. Characterizing the mechanical sensitivity can not only directly represent the acoustic response magnitude of the biomimetic microphones but also directly verify the corresponding theoretical models. Therefore, in this article, we designed and fabricated an MEMS biomimetic microphone with a fiber-optic Fabry-Pérot interferometer (FPI), based on which we successfully measured the mechanical sensitivity of the biomimetic microphone by the fast demodulated white-light interferometry (WLI) for the first time. In addition, an improved theoretical model with exact expressions was first derived to better describe the acoustic response of the biomimetic microphone, and the theoretical and measurement results can be corroborated by each other in terms of mechanical sensitivity. Therefore, this study verifies a feasible solution to directly measure the acoustic response of the biomimetic microphone and constructs a more effective and detailed theoretical model to describe this acoustic response. The results in this article can not only provide a numerical reference for designing future demodulation systems regarding the dynamic range and the linear demodulation interval but also promote a deeper understanding of the working mechanism of the biomimetic microphones.