Measurements were carried out in shallow water 23 m deep off the Argentinian coast in quasi-isovelocity conditions. The data were analyzed for grazing angles in the interval 1°50′–8°. A method to make an indirect determination of bottom-scattering strengths in shallow water has been worked out. It consists of separating the surface, volume, and bottom contributions according to their time decays in recordings of signals from distant explosions. For this purpose, a simplified model based on the equivalence of both bistatic and monostatic experimental geometries was used. The results show a slight increase in bottom-scattering strength with grazing angle and with frequency according to the 1.0 power 3 dB/octave). An attempt to correlate scattering strength with type and roughness of the sea bed was also carried out. The coincidence between our results and direct measurements made under similar conditions by others suggests the validity of the present method.
In the South Atlantic Ocean the cold Malvinas current flowing up from the South meets the warm Brazil current flowing down from the North off the coast of Argentina near Buenos Aires. The confluence of subtropical and subantarctic water masses results in a complex oceanographic regime. As a basis for a future measurement program, acoustic propagation predictions have been made for the region utilizing raywave and other modeling programs. Results are compared to a previous experiment conducted through the subtropical convergence near New Zealand [R. W. Bannister et al., J. Acoust. Soc. Am. 62, 847–859 (1977)].
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