The Research On Controlling The Internal Airborne Noise Of Ship

In a modern ship design, ship noise has become one of the most important tactical and technical indicators. The noise indicators of ship include radiated noise, self noise, target strength and internal airborne noise. This thesis proposes a method for controlling ship's internal airborne noise with the traditional noise control technology and the active noise control technology. The discussion is favorable for noise control of the hull.This thesis presents the theory of sound absorption technology and sound isolation technology in the traditional noise control technology. At first, the absorption coefficient of sound-absorbing material is investigated in theory, and presented engineering application and effect evaluation in a ship's interior. Then according to acoustic boundary conditions and fluctuations equation, with Euler formula, the sound pressure transmission coefficient and the sound transmission loss formula of sound isolation components are derived. Finally, an analysis under two conditions of sound isolation in ship is presented, and the empirical formula of engineering application is also presented.This thesis proposes a method for using secondary sound sources to produce global reduction of the total time averaged acoustical potential energy in an enclosure of ship. The total time averaged acoustical potential energy is expressed as an objective function, according to sound pressure boundary conditions and Helmholtz equations, with unconstrained optimization method, the noise reduction formula is presented for the active noise controlling of a finite stiffened cylindrical shell which inspirited by interior airborne sound pressure. Finally, an active noise control analysis of a finite stiffened cylindrical shell's interior acoustic cavity is presented. The discussion is favorable for the active noise control technology of the hull.