Ray Transmissions Over a Sloping Bottom in Shallow Water
RENSSELAER POLYTECHNIC INST TROY NY
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The effects of a sloping bottom on acoustic transmissions, between a source and receiver at arbitrary but fixed locations, are investigated using ray theory. An isospeed channel is assumed, and bottom angles up to about 3 degrees are considered. Sloping bottom influence on per-ray quantities, including travel time and transmission loss, are examined for cw transmissions. Significant variations are shown to occur, such as travel time changes of more than 200 ms over ranges of about six km. Per-ray transmission loss is found to be influenced strongly by bottom slope, the amount of influence depending upon source-receiver bearing and the bottom loss model used. Variations of more than 20 dB are demonstrated. Effects of a sloping bottom on the total acoustic field are examined also, and the results compared with those for a horizontal bottom. Finally, a simple model of a shallow water front is superposed over the sloping bottom, and travel time is investigated. The sloping bottom effect can induce travel time changes more than 300 larger than the frontal effect for different source-receiver geometries and bottom inclinations.