Noise Source Separation Method Research In Floating Raft Isolation System

The floating raft isolation system of vessels contains much equipment, and is an important source of mechanical noise in vessels. To improve the acoustics performance of vessels, the floating raft isolation system must be studied. The study of noise source separation of the floating raft isolation system can find out the main factors of affecting the acoustic performance of vessels, and guide the work of noise and vibration reduction in the following steps. So the study of noise source separation has great significance. The current noise source separation methods have some problems to research the floating raft isolation system. In view of this situation, the improved transfer path analysis method is proved to solve the problem of noise source separation in the floating raft isolation system.The principle of transfer path analysis and operational transfer path analysis are presented in the second chapter of the paper, and the advantages and disadvantages of the two methods are also described. Then, for the specific circumstances of floating raft isolation system, the calculation method of exciting force and the measurement method of frequency response function in transfer path analysis are researched when the transfer path analysis method is used in the floating raft isolation system, and several methods of the contribution assessment are described in this paper.The transfer path analysis method is accurate but complex, the operation transfer path analysis method is high-speed but inaccurate. In view of this, the further research is proceeding in the third chapter. Combined with the advantages of these methods, the improved transfer path analysis is proved. The method can equal multi-exciting force produced by equipment feet to an equivalent exciting force, so the number of frequency response functions in the system can be reduced. Besides, the method can use the operational data and the simplification of piecewise function to calculate frequency responses function quickly, and avoid the measurement of frequency response functions. The noise source separation in the floating raft isolation system can be realized accurately and quickly by using the method of the improved transfer path analysis.On the basis of the theoretical analysis, an experiment using a diesel engine is preceded on a floating raft of a cabin in the forth chapter of the paper. The improved transfer path analysis is verified in the experiment. And, the results of the experiment show that the improved method for calculating frequency response functions is accurate and reliable. Therefore, the method can realize the fast analysis of the floating raft isolation system.At the end of this paper, according to the basic principles of transfer path analysis and the specific characteristics of floating raft isolation system in vessels, the software of transfer path analysis named TPA is designed for the floating raft isolation system. The software provides an effective analysis tool for the floating raft isolation system.