Home page of the Russian Acoustical Society Proceedings of the X Session of the Russian Acoustical Society
 
Ocean Acoustics

N. V. Studenichnik
RESEARCH OF A SOUND REFLECTION COEFFICIENT FROM A BOTTOM IN RANGE OF ANGLES OF TOTAL INTERNAL REFLECTION.
N.N. Andreev Acoustics Institute
ul. Shvernika 4, Moscow, 117036 Russia
Phone (095)126-9052; Fax: (095) 126-8411;
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The outcomes of experimental research of the sound reflection coefficient from the bottom at low angles lying within the limits of angles of total internal reflection are presented. A new method of research based on the use of signals of repeated bottom-surface reflections, which excited by explosive sound sources is suggested. The method allows one to explore angular relation of the reflection coefficient from the bottom in the range of low angles from units to 20-40 and in the frequency band from units up to hundreds hertz. From 3-5 to 30-60 of bottom-surface reflections are met in various regions of the World Ocean depending on the region, chosen distances, parameters of bottom deposits and structure of the bottom, in experiments at the deep ocean at large distances. Up to 1500 bottom-surface reflections were recorded in the shallow water at a rocky structure of a bottom. The offered method enables one to obtain reliable data (averaged on the number of reflections) with minimum of admissible errors. The examples of the power and space-time structure of sound fields are presented for the Black Sea at a depth of 2000 m and in the Arabian Sea of the Indian Ocean as a frequency function (10-400 Hz). The range of the reflection coefficient variation depending on parameters of the ground and region of researches is shown. In deep water the values lie in limits from 0,1-0,2, to south-west from the Madeira Island in the Atlantic Ocean, up to 0,95-0,98 in the central region of the Black Sea and in the Arabian Sea of the Indian Ocean. In shallow regions of the South-Chinese Sea at a depth of 40 m, the effective reflection coefficient from the surface and bottom on separate frequencies reaches values 0,997. The explored range of low angles (that were not investigated in the literature at all) is most essential for the formation of sound fields in long-sound propagation and forecasting of operating of hydroacoustic means of underwater supervision.