A piezoelectric AlN MEMS hydrophone with high sensitivity and low noise density

[Display omitted] •The hydrophone is composed of a 10by10 piezoelectric aluminum nitride (AlN) membrane array.•Equivalent noise model is used to analyze the equivalent input noise of receiving system.•A new pouring method is applied to improve the acoustic performance of the matching layer.•The lowest equivalent noise density of 52.6 dB@100 Hz (Ref. μPa/√Hz) of MEMS hydrophone is achieved in this paper. This paper presents a micromachined hydrophone with high sensitivity and low noise density. The hydrophone is composed of a 10by10 piezoelectric aluminum nitride (AlN) membrane array, a low noise amplification circuit, and packaged by an acoustic transparent material. Equivalent noise model is used to analyze the equivalent input noise of receiving system, which can be effective to reducing the noise floor by choosing appropriate components. Moreover, a new pouring method is applied to improve the acoustic performance of the matching layer. The experiment results show that the packaged MEMS hydrophone achieves an acoustic sensitivity of -178 dB (Ref. 1 V/μPa), a bandwidth from 100 Hz to 1600 Hz, and an equivalent noise density of 52.6 dB@100 Hz (Ref. μPa/√Hz). The enhanced hydrophone is beneficial to achieve weak signals detecting in pipeline leak detection, marine noise monitoring and many other low frequency engineering applications.