Propagation and Reverberation in Shallow Water for a Vertical Array and Single Transducer -Implications in Sonar Operation.

摘要

The results of a Shallow Water Echo and Reverberation Experiment (SWERE) PERFORMED IN September 1975 in a flat-bottom, shallow-water, acoustic range located in Block Island Sound are reported. The experiment is part of an effort to develop the concept of Mode Enhancement Techniques (transmitting or receiving techniques for enhancing modes to improve signal-to-background levels in shallow water). Consequently, the results are interpreted in terms of normal mode theory . Compared are the depth and range structures of the out-going signal field and reverberation produced by a vertical array and a single transducer, both driven with equal input power at a frequency of 1700 Hz. It is shown that for the array, the peak- and depth-averaged signal levels decay at a rate of -4 dB per distance octave (distance doubled) in contrast to the rate of -11.3 dB per distance octave for the single transducer. The depth-averaged reverberation levels for the array are 4 dB greater, but decay at approximately the same rate, -13.5 dB per distance octave, as for the single transducer. By using the above decay rates and reasonable target strength values to calculate echo-to-reverberation and echo-to-noise levels, it is shown that a vertical array can markedly increase the potential for detection in shallow water over that of a single transducer. (Author)