Wideband response of MEMS resonators beyond their natural frequency for structural health monitoring applications

This study presents an experimental characterization of a multi-frequency MEMS acoustic emission (AE) sensor designed for broadband structural health monitoring (SHM) applications. This work demonstrates the capability of this sensor to operate effectively under off-resonance conditions at significantly lower frequencies. The sensor’s electromechanical response was quantified using a Laser Doppler Vibrometer (LDV) over a broad excitation range of 40–650 kHz. These LDV measurements revealed a consistent displacement response outside the resonance peaks, confirming mechanical sensitivity across the full spectrum. To evaluate its practical AE detection performance, controlled wire-break tests were conducted and benchmarked against a commercial broadband AE sensor. The MEMS sensor demonstrated comparable signal fidelity and broadband response in the frequency range below 100 kHz. These findings highlight the sensor’s viability for detecting low-frequency AE events that typically fall outside standard AE sensor resonance bands. The combined LDV and wire-break analysis establishes a comprehensive framework for validating MEMS AE sensor behavior both off-resonance and at resonance, supporting their integration into wideband AE monitoring systems.