Wide-band aero-acoustic microphone with improved low-frequency characteristics

A wide-band aero-acoustic microphone was realized using a bulk micro-machining process based on the deep reactive-ion etching of silicon. Compared to the previously reported surface micromachined microphone, the sensing diaphragm is completely sealed, thus eliminating the loss of low-frequency response associated with the release holes. A dynamic sensitivity of ~0.33 μV/V/Pa was measured using optically calibrated acoustic shockwaves (“N-wave”) generated using a high-voltage electrical spark-discharge system. This value is comparable to the ~0.28 μV/V/Pa static sensitivity, measured using a nano-indentation technique. The response of the microphone is relatively flat from 6 kHz to 500kHz, with a resonant frequency of ~715 kHz.