Modeling on low-frequency underwater noise radiated from a typical fishing boat based on measurement in shallow water

Abstract

As evidenced in documents during the past decades, the impact of man-made underwater noise on the marine environment has always attracted more and more interest of the global researchers. About ten kinds of models have been proposed to predict underwater radiated noise (URN) by ships, and most of which are applicable above 100 Hz. This paper is aimed to modeling the low-frequency URN. Extensive measurements were made of the URN of a small fishing boat (length 43 m, displacement 500 tons) at South China Sea. The URN data show the high-level noise below 100 Hz is mainly contributed by the mechanical noise (e.g., main engine and service diesel generator) and propeller cavitation, and performs complex varying characteristics with the speed. The effect on the Transmission Loss (TL) from the sound-speed profile and bottom has been analyzed, compared with the empirical function, which show the estimated TL has an important influence on the spectral source levels (SSLs). Inspired by the method in AQUO (Achieve QUieter Oceans) project, a predicted model applied to typical fishing boat was built.As evidenced in documents during the past decades, the impact of man-made underwater noise on the marine environment has always attracted more and more interest of the global researchers. About ten kinds of models have been proposed to predict underwater radiated noise (URN) by ships, and most of which are applicable above 100 Hz. This paper is aimed to modeling the low-frequency URN. Extensive measurements were made of the URN of a small fishing boat (length 43 m, displacement 500 tons) at South China Sea. The URN data show the high-level noise below 100 Hz is mainly contributed by the mechanical noise (e.g., main engine and service diesel generator) and propeller cavitation, and performs complex varying characteristics with the speed. The effect on the Transmission Loss (TL) from the sound-speed profile and bottom has been analyzed, compared with the empirical function, which show the estimated TL has an important influence on the spectral source levels (SSLs). Inspired by the method in AQUO (Achieve QU...