Kasatkin B.A., Kasatkin S.B.
A classification of known solutions of the Pekeris boundary value problem obtained in various model formulations is given, and their comparative assessment is given. To verify various model solutions, an experimental study of the energy and spatial structure of the sound field in a shallow sea in the infrasonic frequency range of 2—20 Hz, which is obviously lower than the first critical frequency of the Pekeris model waveguide, was carried out. The results of experimental studies of sound fields using combined receivers, forming a vertically oriented 3-element antenna, are analyzed. Based on the results of the analysis of the vertical structure of the sound field, it was concluded, that the sound field at the extremely low frequencies of the infrasonic range is formed by inhomogeneous Rayleigh–Scholte waves, regular and generalized. As the frequency increases, the depth of penetration of the sound wave into the bottom half-space decreases and the role of inhomogeneous waves of the Pekeris waveguide, excited by the complex angular spectrum of the source, increases. Such waves appear as hybrid waves, but only with a generalized description of the sound field in a non-self-conjugated model setting. The kinematic characteristics of the sound field are analyzed with a refined definition of the group velocity as the rate of energy transfer. The mechanisms of a significant slowing down of the energy transfer rate in the waveguide at low frequencies are discussed.
