Acantilever Microphone Using Resonance of Closed-End Air Columns

This paper reports on a cantilever microphone for ultrasonic waves using resonance of a closed-end air column. The proposed microphone is composed of a cantilever and a cavity installed just under the cantilever. Sound waves of a specific frequency resonate in the cavity and the cantilever senses the resonance. Therefore, the microphone acquires high sensitivity and sharp resonance at the resonant frequency. We measured the frequency responses of the cantilever and the microphone to evaluate the sensitivity in the range of 20 to 40 kHz. The microphone improved the sensitivity by 22 dB at the resonant frequency compared to the cantilever without a cavity.