| Summary: | Large-aperture coherent towed hydrophone array systems are capable of surveying wide ocean areas for detection, classification and localization of various underwater and surface objects. Current ocean acoustic monitoring equipment is costly, and the robust expansion of ocean acoustic sensing has primarily been held back by the lack of affordable multi-sensor systems even as the ability to analyze this data becomes more widespread. The ocean bio-acoustic sensing community has numerous researchers using single dipping hydrophones, buoy mounted hydrophones and small-aperture fixed hydrophone systems. While these systems are readily available, they do not offer the directional sensing, wide area surveying, array gain and the enhanced Signal to Noise Ratio (SNR) capabilities of a large-aperture coherent hydrophone array. In this thesis, a prototype eight-element oil-filled hydrophone array is developed to measure the acoustic field in littoral waters. This array is equipped with heading and depth sensors as well as a compact workstation with an independent Global Positioning System (GPS) receiver and winch system. The array is developed using rapid prototyping technology and low-cost manufacturing techniques by designing 3D printing thermoplastic urethane array internals, pressure tolerant designed amplifiers, potting connector moldings using 3D printed over molds, machining stainless tube adaptors, test and verification of transducer/sensor components that are readily available and acoustic testing of noise dampening materials. The prototype array developed here will serve as the basis for the development of a 160-element large-aperture coherent hydrophone array. The prototype array was deployed during an experiment between Jeffreys Ledge and the Stellwagen Bank region off the coast of Rockport, Massachusetts USA. During the experiment, several humpback whale vocalizations and distant ship tonals were recorded. Visual confirmation of humpback moving in bearing relative to the array verifies the directional sensing ...
|
|---|