Abstract
A sub-bottom profiler system for remotely operated vehicle in deep sea was developed to observe surface sedimentary layers of several thousand meter-depth. Using a parametric acoustic array, we realized a very narrow beam width of 4 degrees with the frequency of 3.5 kHz. In this report, first, the dependency of the secondary pressure levels of parametric acoustic sources on the depth of water is calculated by the use of the physical data obtained in real sea. As the result, it is shown that the second pressure levels become slightly higher in deep sea of 6, 000 m than the values at sea surface. Next, a prototype of the parametric source for the experiments under ordinary ambient pressure is developed and tested. The experimental data obtained in water tank agree with the calculated values. Then, in the field experiments of the sub-bottom profiling at the wharf in comparison with the conventional source. Finally, we developed a parametric sub-bottom profiler for 10, 000 m class ROY, and acoustic characteristics of these equipments measured in water tank and experimental results in shallow water are shown.
