Design of a Small Fisheries Research Vessel with Low Level of Underwater-Radiated Noise

Abstract

It is important for a fisheries research vessel to reduce the underwater-radiated noise. In 1995, the International Council for the Exploration of the Sea (ICES) firstly recommended the maximum noise level for research vessels to ensure the acoustic research works and to prevent the fish reaction against the noise. Since then, it has been the world standard for the design of fisheries research vessels. For a small size vessel, however, it is very difficult to achieve the recommendations because of not enough space or capacity to make sound insulations. Moreover, the Froude number (Fn) of such small vessels tends to be higher than that of the larger vessels. Since the higher Froude number of the operating condition causes the large wave-making resistance, both propeller thrust and occurrence of cavitation increase, which tends to result in the higher level of underwater-radiated noise. Meanwhile, the fisheries research-cost can be reduced by using a small vessel, because not only the construction and operation cost, but also maintenance cost become lower than those of a large vessel. It would be desirable and efficient if a small vessel could satisfy the ICES's recommendation in place of a large research vessel.
In this paper, the authors propose a design method for a small research vessel to reduce the underwater-radiated noise level. Utilizing this method, a small fisheries research vessel whose capacity is 290 GT and length is 33.5 m has been designed. From the sea trials after the construction, it has been proved successfully that the underwater-radiated noise level is the world lowest class at 10 knots (Fn=0.28) of researching speed and still satisfies the ICES's recommendation even in 11.6 knots (Fn=0.33) of the high-speed region.