A MEMS Low-Noise Sound Pressure Gradient Microphone With Capacitive Sensing

A silicon microelectromechanical systems microphone is described that detects sound pressure gradients. The diaphragm consists of a stiffened plate that rotates around a central axis in response to sound pressure gradients. The motion of the diaphragm is converted into an electronic signal through the use of interdigitated comb fins that enable capacitive sensing. Measured results show that the microphone achieves a substantially lower low-frequency sound pressure-referred noise floor than can be achieved using existing dual miniature microphone systems. Measured directivity patterns are shown to be very close to what is expected for sound pressure gradient receivers over a broad range of frequencies.