Research On Noise Analysis And Control Of Merchant Ships

With the new regulations of the noise level on board revised by International Maritime Organization(IMO)coming into force,the noise control of the ship has been paid more and more attention by the domestic shipbuilding enterprises.In the design stage,prediction analysis of noise level and noise reduction design can effectively avoid technical risks and save design and construction costs.Therefore,the research on ship noise analysis and control technology has important engineering value.In this paper,combined with the actual ship design of a CON-RO vessel,the noise analysis and control technology of merchant ships was studied.The main noise specifications were compared,the process of noise analysis and control in the whole design stage were studied,noise prediction analysis and noise reduction was carried out in the preliminary design and detailed design stages.The paper mainly includes the following content:(1)The comparison between new and old version of the Code on Noise Levels on Board was carried out through the requirement of acceptable sound pressure levels,sound insulation index and measure equipment.Besides,the compare between new version of the Code on Noise Levels on Board and rules of several main classification societies was carried out.The influence of shipbuilding industry of our country brought by application of new code was analyzed.(2)The process of noise analysis and control in the design of merchant ships was introduced,and the technical difficulty and key measures of noise analysis and control in every stage of ship design were summarized.In the preliminary design stage,the whole cabin noise control scheme was formulated according to the technical characteristics of the ship type and the noise limit requirements,and the preliminary assessment of cabin noise is carried out based on the empirical formula method or the method of the mother ship.In the detailed design stage,the assessment of cabin noise was carried with the numerical method.For the cabins where noise is over the limit,noise reduction measures were adopted.In the production design stage,the construction technology of vibration and noise reduction should be reasonably compiled,and the installation quality of vibration and noise reduction facilities should be paid attention to.(3)In the preliminary design stage of the target ship,a brief noise assessment of major cabin was carried out based on empirical methods.It was found that noise level of most ship cabins can meet the requirements of technical specification,but part of the accommodation cabins exist excessive risk.According to the preliminary analysis results,some treatments such as insulation treatment of cabin wall of the air-conditioner room,application of high acoustic rock wool board and welded insulating glass were adopted.(4)In the detail design stage of the target ship,a detailed evaluation of noise level of the cabins on board was carried out based on numerical methods.The contribution of different types of noise components to the noise of typical accommodation cabins is compared and analyzed.By analyzing the main noise components and transmission path,the optimal design scheme of acoustics is proposed,and the noise level of cabin can be effectively reduced and improved by reducing the noise level of the main noise source and increasing the insulating material of the bulkhead.According to the measurement results of the actual ship,the noise level of the ship meets the requirements of the technical indicators,which verifies the feasibility and effectiveness of the noise analysis and noise reduction design technology mentioned in the paper.The research content of this paper can provide references for the noise analysis and noise reduction design of related ships in the future.