Optimization Theory And Methods Of Ship Cabins Acoustics Design

Due to the implementation of EEDI on January 1st, 2013, ship designs started to face new challenges brought by “green ships”. Ship designs nowadays should consider not only the strength of structure, but also the factors like low emissions, low energy consumption and comfort of vibration and noise, towards the environmental friendly and safety design. As for the comfort of vibration and noise, design technology for ship vibration and noise reduction receives universal attention. IMO adopted an even stricter standard for cabin-noise on July 1st, 2014. With the implementation of this new international standard for noise, the acoustic design method of ship cabins becomes a hot topic of current research.Focusing on the acoustic design involved in the ship design process, this dissertation studies cabins acoustic layout optimization theory, theory and methods of ship structural acoustic design, as well as optimal allocation design method of sound packages.Firstly, the way of cabin-noise control at the stages of conceptual design and initial design of ships is studied. To minimize the cost of cabinnoise reduction, the overall acoustic layout of ship cabins is optimized, and cabins with different functions are properly laid out according to the sound pressure limits on the various cabins. Based on the proposed general cabins acoustic layout optimization model, this dissertation presents two methods for optimizing the matching relationship between ship spaces and ship cabins. One is Hungarian algorithm and the other is criterion method using sorting inequality. Software for the proposed optimization algorithm is developed, and examples of cabin acoustic layout optimization design under areas and locations constraints are given.Secondly, methods of controlling the ship noise transmission paths at the stage of the detailed design of ships are conducted with statistical energy analysis. By expanding the concepts of temperature and entropy in the sense of thermodynamics to be the vibroacoustic temperature and vibroacoustic entropy within the framework of energy statistics, and application of Graph Theory, the way of identifying the cabin-noise transmission paths is investigated. By turning the problem of identifying noise transmission paths into that of K shortest path, and taking the mixing entropy as the weight, and adopting the removing side algorithm, the main noise energy transmission path is found. This method can quickly identify the main cabin-noise transmission paths in energy statistic model.Using sound package technology in solving the problem of cabinnoise reduction design will be the future trends. Sound package is an acoustic component which can achieve the pre-set noise reduction effect, by optimizing the combination of structural matrix materials, soundabsorbing/sound-insulation materials and damping materials. Based on the identification of the vibration and noise transmission paths and acoustic layout optimization design, the optimal allocation of sound package is studied with the acoustic sensitivity and genetic algorithm. This technology is significantly valuable for engineering application, and plays an important role in realizing the standardization and program of sound package optimization design and effectively reducing the cost of sound package.Finally, integrating the theory of cabin acoustic layout optimization, the technology of identifying noise energy transmission paths, and the technology of sound package, a flowchart suitable for noise reduction design of large ships is proposed, and software based on the abovementioned theory for optimizing the acoustics of ship cabins is developed.