A Novel Slotted-Structure Low-Frequency, Low-Noise Piezoelectric Accelerometer for Hydrophones

Co-vibrating vector hydrophones, using piezoelectric accelerometers as sensitive elements, are widely used for low-frequency underwater target detection. A novel piezoelectric accelerometer, based on a PMNT triple-laminate structure and a uniquely designed four-slot proof mass, is developed to address the long-standing challenge of achieving both high sensitivity and low self-noise. Guided by theoretical models of sensitivity and self-noise, a slotted petal-shaped structure is optimized to lower the resonant frequency. Finite element analysis validated the principles and guided parameter optimization, resulting in a final structure with a beam thickness of 0.8 mm, a proof mass outer diameter of 12 mm, and a slot width of 0.6 mm. The fabricated sensor demonstrated a resonant frequency of 2438 Hz, closely matching the simulation, a low-frequency sensitivity of ≥ 11.3 V/g (with ≤ 1.6% variation up to 300 Hz), and a self-noise floor of approximately 30 ng Hz-1/2. Comprehensive noise component analysis revealed that the dielectric loss noise of the piezoelectric material dominates the main noise sources in the frequency band from 1 Hz to 1 kHz. These results validate that the slotted-structure design is an effective approach for resolving the traditional trade-off between bandwidth and sensitivity, offering a promising solution for advanced low-frequency vector hydrophones in marine target detection.