Results are presented from an experimental study of the propagation of acoustic pulses on the shallow marine shelf of the Black Sea and a coastal wedge. Signals associated with bathymetric refraction are analyzed. Short-period signal fluctuations on a Black Sea coastal wedge along stationary acoustic tracks with a mean bottom slope of ~25° are studied. The spectra and characteristic periods of fluctuations in the amplitude, azimuthal angles, angles of slide, and arrival times of pulsed signals are determined. The main reasons for fluctuations in the characteristics of signals under conditions of pronounced horizontal refraction with changing bathymetric characteristics are discussed.
The frequency dispersion of the sound propagation speed in a marine waveguide makes it possible to compress an acoustic signal with an increase in its intensity. The paper presents the results of experimental research of this effect during the propagation of a broadband acoustic signal from a parametric array in shallow water. The parametric array provided single-mode excitation for the marine waveguide. The possibility of compressing a broadband signal during its propagation in shallow water with special selection of the frequency modulation mode is discussed. Waveguide dispersion leads to an increase in the efficiency of parametric radiation in shallow water.
Results of a survey of the technical state of the underwater sections of two bridges and a reservoir are presented. The techniques used to perform the studies are briefly described. The basic parameters of the equipment used — side-scan sonar and parametric profilograph — are presented. The advantages gained with the use of acoustic instruments in monitoring the technical state of hydraulic and traffic structures are demonstrated.
