Development of Acoustical Oceanographic Techniques

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My program of research is focused on instrument development and applications in underwater acoustics. Developments in this area are important because acoustic methods are the only means that allow underwater remote sensing or communication over extended distances (underwater, sound travels many orders-of-magnitude farther than can light or radio waves). Active "sonar" systems are used for mapping and inspecting underwater structures and bottom depths (with resolution ranging from meters to centimeters), and similar systems are used for evaluating the integrity of pipes (from the inside). Precision calibrated systems are used for undertaking fisheries surveys, and a variety of systems are important for defense related purposes. Passive systems that only listen are used for intruder monitoring, leak detection, biological observations, and monitoring of marine mammals. In Canada there are manufacturers of sonar equipment centered on both the Atlantic and Pacific coasts. These manufacturers, Government Departments of Fisheries and Oceans, Natural Resources, and National Defense, as well as many industrial users, all have a need for graduates with specialty skills in acoustic systems and applications. The specific area of focus in this proposal is the development and application of Doppler sonar systems which allow measurement of water velocities over a range of depths from a single instrument position using signal processing that is similar to that used in police radar. This research program will apply existing commercial Doppler systems to new applications and develop new systems for use where existing technology is not suitable. One component of the program will use observations from a commercial Doppler system to analyze water velocities in sites where deep-water corals occur (at depths beyond 500 m off the coast of Labrador). Commercial Doppler systems normally exclude signals that are scattered from fish, but by using an analysis method that we developed, it is possible to extract both fish swimming velocity and water velocity at the same time. This capability is being developed to provide fisheries regulators and researchers with information on the movement of fish populations. Another component of this research program involves the development of a new sonar system to measure turbulent velocity profiles where the small scales of motion make existing measurement systems unsuitable. Turbulence is important from a research perspective because it is responsible for mixing of different ocean water types. At this time there is also interest in ocean turbulence from the perspective of a new industry that is developing turbines that convert tidal motion into electrical power. Knowledge of turbulent velocities is critical to allow the design of safe and efficient generating turbines.