Stable Components of the Wave Field in Underwater Sound Waveguides

A technique is proposed for determining which sound field components are weakly sensitive to variations in the parameters of the speed of sound field in a marine waveguide. Such components are formed by narrow ray beams, with the dispersion of their vertical coordinates on the distance to the point of observation being less than the vertical scale of the perturbation. Since these rays pass through the same inhomogeneities, their phases in the presence of perturbations acquire approximately the same increment. For a monochromatic field, such components in perturbed and unperturbed waveguides differ only by their phase factors. With a pulsed field, perturbations lead only to some additional delays of the stable components. A procedure based on decomposing the field into coherent states is proposed to select stable components from the total field. The solution to the problem of finding the location of a source using the stable components is illustrated by a simple example.