UDC 534.26We study the possibilities of acoustic tomography observation of small-size bodies in shallow-water layered oceanic waveguides within the framework of geometric acoustics. For increasing the spatial resolution and sensitivity in the considered inverse problem, we used the waveguide-matched focusing of the received and radiated fields into the region of expected location of the observed body. The algorithm of observation in this case consists of search for a global extremum of decision statistics, which is determined by the difference between the measured data and the hypothetic body location. Such hypotheses are formed on the basis of a priori information in the form of the waveguide model and the data on the structure of the observation system. For decreasing the influence of noise associated with the interference of fields in the waveguide, selection of separate tomographic ray projections with the subsequent incoherent accumulation of partial images is used. A tomographic shallow-water observation model based on such principles is analyzed.

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We discuss the possibilities of forming low-frequency mode acoustic signals by vertical arrays. We present formulations and solutions for several problems of optimal formation of such signals. Results of numerical simulation of the selective excitation of mode-signals are presented with reference to practical problems related to the low-frequency low-mode acoustic tomography of inhomogeneities in shallow sea.