Study On Noise Prediction Of Ship Cabin With SEA

Shipboard noise control is attracting increasing attention from the shipping industry. This is due to the introduction of national and international rules and recommendations concerning noise such as IMO468(A) of International Marine Organization (IMO) and DMA noise-code of Danish Maritime Authority (DMA), but also a growing interest in reducing annoyance and discomfort to the crew and passengers. It is recognized that light noise levels can be a health problem, a safety factor, and that excessive noise can decrease the efficiency of the work force and have a general negative effect on the environment. So the ship-owners, especially the European ship-owner, stipulate the requirement about the shipboard noise in the contract specifications. It is necessary to predict the noise of ship cabin in the stage of the project and to make the noise level in ship cabin satisfy both the requirement of the contract specifications and criteria.The noise has a relationship with the vibration. To study the noise is based on the study on vibration. But the noise is more sensitivity to many factors than that of the vibration, so it is not only important but also difficult to predict the noise level. There are three main approaches to predict the noise level: similitude structure method including the frequency-response method and proportion method, modal method including finite element method (FEM) and boundary element method (BEM), and statistical energy analysis (SEA).The advantage of similitude structure method is to give the predicting data fast, but it has some error because of dealing with rough similitude parameter and mass load. The modal method can do finite and distinct lower modes. The higher the frequency range, the greater the error and the analysis difficulty is getting more with the complexity of structure. FEM and BEM is very adapted to predict the noise level in lower frequency, but they need to describe the geometry of structure detailedly which is wasting-time for many modes in system and high frequency, wide band and random variable. The SEA method need a much simpler description of the system and has many advantage in analysis of high frequency, high modal density and complex dynamic systems in despite of limitations of assuming that the system is conservative and light coupling. But this is not a problem for ship structure which is thin and good ductibility.The basic equation of statistical energy analysis is deduced in this paper, the shipboard noise of 295,OOODWT VLCC is calculated based on SEA, the factor effect on the noise of shipboard is discussed and some measurement to reduce the noise level is suggested.