Miniature optical MEMS microphone with 14dBA noise floor

This paper explains the fundamental technology used to create an optical microphone transducer. In recent years, microelectromechanical system (MEMS) capacitive microphones have demonstrated improved performance. State-of-the-art capacitive MEMS microphones can achieve SNR in the order of 73 dBA (21 dBA noise floor) with overall dynamic range in the order of 101 dB. There are fundamental challenges to driving the performance of capacitive MEMS microphone technology in very small packages to new heights. Piezoelectric MEMS microphones have not demonstrated SNR performance >65 dBA. The next breakthrough in miniature microphone technology will come from optical MEMS microphone technology. 80dB SNR (14 dBA noise floor) with 132 dB dynamic range (146dB maximum sound pressure level) has been achieved in a very small package. This paper will review the fundamentals of optical acoustic transduction and describe some of the approaches to miniaturization of the technology.