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A novel suite of parameter extraction experiments were used to assess the accuracy of individual elements of a lumped element model for a microelectromechanical systems based piezoelectric microphone. The MEMS microphone was developed via model-based design utilizing the lumped element model for use in aeroacoustic applications. Laser vibrometer scans of the microphone diaphragm while subjected to electrical or pressure excitation provided experimental predictions for the effective electroacoustic piezoelectric coupling coefficient, diaphragm compliance, and mass. The experimental results were compared with analytical predictions from a piezocomposite diaphragm model for these individual lumped elements. Associated lumped element model predictions were also compared with the results of device characterization experiments. Similar trends in theory and experiments were observed, though comparative error in element values was attributed to uncertainty in model-inputs, most notably thin-film residual stresses in the microphone diaphragm. [This work was sponsored by Boeing Corporation.]

This paper presents the design, fabrication and preliminary testing of a flush-mount sensor die and associated package for an aluminum nitride (AlN) based piezoelectric MEMS microphone for aircraft fuselage arrays. The optimal microphone design is determined using composite plate theory in combination with lumped element modeling. Through-silicon-vias are incorporated into the fabrication of the sensor thus eliminating front-side wire bonds and enabling an overall flush surface for the packaged sensor that minimizes flow disturbance.Frequency response measurements show a comparable sensitivity (13.1 µV/Pa) and significantly higher resonant frequency (194 kHz) than prior piezoelectric aeroacoustic microphones. The developed packaging method for the sensor demonstrates an overall flushness to within 10 µm, showing substantial improvement from any previously reported efforts. This is the first truly flush-mount piezoelectric MEMS microphone with associated packaging that has been developed.