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Experimental confirmation of horizontal refraction of cw acoustic radiation from a point source in a wedge-shaped ocean environment
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1988
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Coastal EngineeringEngineeringAcoustical OceanographyUnderwater AcousticOceanographyMarine EngineeringMarine Geophysical DataEarth ScienceGeophysicsNaval ArchitectureHorizontal RefractionOcean Internal WaveGeodesyMarine HydrodynamicsMarine GeologyCw Acoustic RadiationSeismic ImagingWake HydrodynamicsMultiple ReflectionsOcean EngineeringPhysical OceanographyAerospace EngineeringPoint SourceBearing ShiftsEnergetic Horizontal Refraction
Analysis of experimental data obtained in the region of the East Australian Continental Slope has been found to be consistent with theoretical predictions of energetic horizontal refraction due to multiple reflections from a sloping bottom. The observed azimuthal characteristics are in accordance with both normal mode and ray theoretical solutions. The experiment, conducted with two ships (one towing a source and the other an array), started in water ≊400 to 500 m deep with an initial separation of 34 km and proceeded to deeper water on a diverging but constant line of bearing course. Bearing shifts deduced from beamformed data show changes of tens of degrees in as little as half an hour. These bearing shifts demonstrate the dominance of horizontally refracted arrivals for the geometry. A combination of source–array positions and critical angle effects served to limit both the azimuthal extent of energy received and the total number of modes arriving at any one position.