Characterization and Modeling of an Acoustic Sensor Using AlN Thin-Film for Frequency Selectivity

In this study, a one-dimensional beam array acoustic sensor was built using microelectromechanical system technology to achieve mechanical frequency selectivity. The acoustic sensor contained 16 beams of various lengths. The frequency selectivity was evaluated with a scanning laser Doppler vibrometer, while applying an alternating current having various frequencies with 2 volts amplitude and 0 volt offset. The beams formed separate band-pass filters in the proximity of the corresponding resonance frequencies in the range of 3 kHz to 13 kHz. The first resonance frequencies of the beams were calculated using finite element analysis to simulate the frequency response. In the finite element analysis models, mode shapes were studied to understand the effect of the beam deformation caused by the residual stress generated during the MEMS fabrication. The measured and simulated first resonance frequencies of the beams provided solid evidence of the tonotopicity of the sensor.