A. A. Stromkov

TL;DR: In this paper, a numerical time reversal of waves is proposed instead of the conventional Time Reversing of Wave procedure used in underwater acoustics, where the test sound source and the receiving arrays are used, as in the conventional method, but the transmission of the received signals after their time reversal into the same medium, as well as the measurement of the field obtained in this way at the point of the test source, is replaced by computations.

Abstract: A numerical experiment is carried out to study the focusing of a low-frequency (100–300 Hz) sound field in a shallow-water acoustic waveguide typical of an oceanic shelf. Focusing with the use of time reversal of broadband acoustic signals, which is called time reversal mirror (TRM) of waves, is considered along with focusing by phase conjugation (PC) of a monochromatic sound field. It is demonstrated that, in the case of focusing by the TRM method in the waveguide of interest, it is sufficient to have a single source-receiving element. The use of a vertical array improves the quality of focusing. The quality achieved in the latter case proves to be approximately the same as that achieved in the case of focusing by phase conjugation of a monochromatic field at a frequency identical to the carrier frequency of the broadband signals. It is also shown that, in a range-independent waveguide, intense surface waves considerably reduce the quality of focusing. This effect is most pronounced in the case of using phase conjugation.

TL;DR: In this paper, the results of experimental investigations of the seismoacoustical sounding of the bottom structure of the Caspian Sea were obtained using a ship towed hydroacoustic emitter of LFM pulse signals in several frequency ranges of frequency band from 100 to 1000 Hz based on the high coherence and relatively high frequencies of emitted signals.

TL;DR: In this article, the possibilities of matching low-frequency underwater sound pulses to the parameters of an oceanic waveguide are considered, and the objective is to optimize the system of few-mode tomographic observation in a shallow-water sea.

TL;DR: In this paper, the authors considered the problem of determining the mode composition of the sound field in a shallow sea by using linearly frequency-modulated broadband pulses at relatively short distances (about 20 km).