Extensive underwater radiated noise analysis of a research vessel in compliance with DNV SILENT notation

Abstract

Studies have shown that underwater-radiated noise from ships may have both short and long-term negative consequences on marine life, especially marine mammals. An international community of researchers, environmental groups, government agencies, and sectors of the shipping industry has recognized shipping noise as an important marine conservation issue. In 2010, Det Norske Veritas (DNV, the Norwegian Classification Society) made the first attempt to fix the radiated noise limits for commercial ships, in which vessels fulfilling the requirements will be given an optional class notation SILENT. In this study, underwater noise measurements were performed on a new research vessel in shallow water in compliance with DNV SILENT notation. More speeds were tested than required by DNV, to understand the characteristics of related noises. Results show the new ship satisfies the allowable noise level curve for type R (Research); however, the measured noise levels do not increase as speed accordingly. Moreover, level differences can be significant between starboard and port side tracks especially at low frequencies. Commonly observed coastal currents play an import role on ship maneuverings and test conditions and therefore unexpected results. Practical considerations and suggestions about performing measurements and analyzing the data will be discussed and summarized.Studies have shown that underwater-radiated noise from ships may have both short and long-term negative consequences on marine life, especially marine mammals. An international community of researchers, environmental groups, government agencies, and sectors of the shipping industry has recognized shipping noise as an important marine conservation issue. In 2010, Det Norske Veritas (DNV, the Norwegian Classification Society) made the first attempt to fix the radiated noise limits for commercial ships, in which vessels fulfilling the requirements will be given an optional class notation SILENT. In this study, underwater noise measurements were performed on a new research vessel in shallow water in compliance with DNV SILENT notation. More speeds were tested than required by DNV, to understand the characteristics of related noises. Results show the new ship satisfies the allowable noise level curve for type R (Research); however, the measured noise levels do not increase as speed accordingly. Moreover, level...