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indicates the hearing-related reference pressure in air in the unit of dB SPL (ref = 20 μPa). # indicates the pressure gradient from the inlet to the outlet of the transverse-sigmoid sinus.* The f requency matching was perfor med using 1/3 octave nar row-band noise with center f requency of 125/250/500/750/1000 Hz.

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With the tremendous growth of science and technology in the world, the silent submarine has been an interesting research topic for many years. What is of equal interest is how to produce a high-speed submarine that limits noise to minimise detection from the enemy. In this study, we investigated the combination of a propeller and a duct so that when a submarine is operated, it minimises as much as possible the noise without affecting the speed of the submarine. The goal of installing the duct outside the propeller is to reduce the noise and loss of thrust simultaneously. The purpose of this article is to investigate the variation of the magnitude of the noise and thrust that occurs when a submarine propeller is operated in six different types of ducts. The research method is to use the large eddy simulation method with the cavitation model and then to calculate the result using the finite volume method. The study found that Ducts 1 and 4 have a better noise reduction effect and better propulsion than the other four ducts. Among them, Duct 4 has the best noise reduction effect, and Duct 1 provides the maximum propulsion. In all of the computation examples herein, the cavitation phenomenon did not occur. In the future, we will continue to study the growth and decline of related physical quantities with various types of propellers and ducts.