Stern-Aspect Noise Radiated by the Cycloidally Propelled Vessel Seacon and Its Comparison with that Radiated by Conventionally Propelled Vessels.

摘要

The stern-aspect radiated noise of the cycloidal-propeller-powered vessel Seacon was measured and compared with that of several conventionally powered array tow-ships used by the Navy. The radiated noise spectra of the Seacon ranged from 150 to 133 dB re 1 microns Pa/m-Hz over the frequency range 100 to 500 Hz for low-thrust conditions and 153 to 133 dB microns Pa/m-Hz over the same frequency range at full thrust (5.6 knots). The low-thrust conditions were characterized by a more pronounced line structure. For the high-thrust conditions the cavitation-noise background masked most of the lines. Above 150 Hz these levels are equivalent to those of other vessels for which no special quieting efforts have been made. Below 150 Hz the noise spectra of the Seacon continued to increase at about 6 dB per octave, whereas that of the other vessels typically remained constant or peaked and declined. This continued rise is attributed to the Seacon's cycloidal propulsion system. Vessels for which special quieting efforts had been made were 10 to 20 dB quieter. Because of its special maneuvering capabilities the Seacon and vessels like it should be considered first when choosing platforms where station-keeping ability and slow-speed maneuvering are important. The propulsion system of the M/V Acadian Navigator was apparently the most effective in reducing noise, and this type of vessel is recommended for array towing.