Wireless, real-time monitoring of ocean noise via a nimble shallow-water moored hydrophone array

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The objective of the proposed research is to develop a mobile directional hydrophone array, deployable in a range of hydrodynamic conditions and seafloor types in the coastal ocean, and incorporating wireless data transmission for real-time reporting sound pressure levels. The approach will be based on the 5-hydrophone instrument developed by Turbulent Research. The mobile system will be designed for rapid deployment and recovery in water depths of up to 100 m, with the hydrophones emplaced at depth to minimize flow noise from surface waves. Design activities will include modelling of mooring requirements in high energy environments and analyses of current forcing on the instrumentation. A radio link module installed in a surface buoy and cabled to the hydrophone will transmit processed data to a receiver, enabling real time acquisition of the noise signal. Trials will be conducted in Grand Passage, Nova Scotia, a high-flow tidal channel in the Bay of Fundy. This location provides a diverse noise environment, including half-hourly ferry crossings, other vessel traffic, marine mammals (harbour porpoise, seals, and the occasional whale), high current speeds (up to 3 m/s), and breaking surface gravity waves. Underwater ambient noise measurements will also be made in the immediate vicinity of an active marine construction site. The significance of this research is the enhanced capability for opportunistic measurement and evaluation of ambient noise in the marine environment. Targeted applications include: (1) noise levels as a function of distance from stationary sources such as marine construction activities (e.g. pile driving) and in-stream tidal turbines; (2) marine mammal detection and behavioural studies. This research directly addresses the limitations of shore-cabled or autonomous hydrophone moorings through a unique mooring and data transmission design, enabling improved acquisition and reporting of ocean noise data in a wide range of coastal and freshwater locales.