Development of A Large-Aperture 160-Element Coherent Hydrophone Array System for Instantaneous Wide Area Ocean Acoustic Sensing

A large-aperture coherent hydrophone array and processing system has been developed in-house at Northeastern University (NU). The overall acoustic aperture length is 194 m with 160-elements nested into four sub-apertures each with 64 hydrophones and spacing corresponding to half-wavelength at design frequencies in Hertz of 250, 500, 1000, and 2000. Hydrophones with integrated broadband preamplifiers designed with a linear frequency response from 10 to 50 kHz sending differential pair amplified and filtered analog signals to 24-bit, 32-channel Analog to Digital Converters (ADC) with sampling rate programmable up to 100 kHz per channel. Array internals are designed using field replaceable pressure tolerant components including hydrophones, preamplifiers, power modules, telemetry units, and ADC verified by testing in an in-house assembled pressure chamber. Forward and aft modules are equipped with non-acoustic sensor elements to provide depth, heading, pitch, roll, and temperature measurements. The NU array was made without specialized facilities by utilizing modular interchangeable array interconnects allowing for conventional array populating and filling methods. The system implements real-time array data acquisition and processing including beamforming, beamformed spectrogram generation and signal detections. The NU array has been sea tested in 2021 in both shallow and deep water environments of the US Northeast coast.