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.

In this article, a three-dimensional (3D) lumped model of the human auditoria peripherals that consisted of four masses equipped with five major springs and major dashpots is presented. This model will support the quantitative basis for construction of a human middle ear physical model. This 3D lumped model consists of a human ear bone model having a similar working principle as the tiny mechanical structure. The 3D lumped model's parameters were identified using previous anatomical data, and then constructed via a parameter optimizing process using 16 springs and dashpots that represent the tiny mechanical structure's five connections. The computational results showed the sensitivity priority of the five connections to the stapes displacement with a variety of sound frequencies. Moreover, a detailed discussion of the five connections' mechanical properties affecting the magnitude of the stapes displacement was also shown in this paper. As a result of increasing the stiffness in the joint of the middle ear bone connection, the stapes' vibrational amplitude was increased. However, the magnitude of the value of the four masses reacts in a manner that is opposite to stapes displacement. Some specific frequency ranges of the voice properties to the mass and connector systems are also discussed in this paper. The details of the individual mass or joint activity to the stapes displacement at various frequency ranges are also presented. The model's behaviors were calculated using the software ANSYS workbench 15.0, Solid works 2017, and the MATLAB R2015a. Our findings provide a relevant reference for related medical research.