Abstract
Boats with low vibration and noise offer one of solutions to ease the fish avoidance behavior. The vibration and the noise generated by the water-jet electric boats are low compared with those of same sized internal combustion engine boats. However, an objective evaluation of the vibration and the noise of electric boats has not yet been conducted. In this research, an underwater noise of an electric boat and that of an internal combustion engine boat, which is particularly under the audible sound frequency range of fishes, was measured and analyzed. From results of experiments and frequency analysis, maximum noise level of the electric boat was found to be lower than that of internal combustion engine boat. It was also shown that the impeller revolution was the main source of underwater noise for the electric boat.
