Research On Fast Airborne Cabin Noise Prediction On Board

It has been widely recognized that ship noise bring negative effects.In recent years along with the gradual increase of ship habitability requirements,after several discussions of the International Maritime Organization(IMO)the latest “Code on Noise Levels on Board Ships” came into effect on July 1,2014 in order to ensure staff and passengers free from the harm caused by noise.Because the emphasis on noise control of ship design and building are relatively low and the accumulation of the relevant experience is also poorly insufficient before,the new rules brought quite a new challenge to the whole China's shipbuilding industry accordingly.After studying some common forecasting methods,a simple but effective semi-empirical method for ship cabin noise prediction is put forward,based on the system analysis method of "noise source-path-receiving point" and room acoustics in order to achieve the goal of making a preliminary forecast to determine the level of each cabin noise distribution of the whole ship during the initial general arrangement of the basic ship design stage,which make sure designers can adopt noise reduction measures for the cabins in which the noise level exceeds the standards as soon as possible.This thesis focuses on the following aspects:(1)The characteristics,evaluation and control standards of ship noise were studied and the difficulty of ship noise calculation was also pointed out.The noise regulations of major classification societies were compared and then their own characteristics were analyzed.The key areas of cabin noise control were emphasized.(2)Based on a semi-empirical method,practical pre-forecasting method of the cabin noise was discussed in detail.Through quantitative analysis of intensity of the noise source,transmission path and receiving point,some commonly used parameters of practical experience were listed to form a complete ship cabin noise calculation method.(3)After using the proposed method to calculate cabin noise levels of a certain type of speed boat and taking appropriate noise reduction measures for cabins in which the noise level exceeds the standards and comparing with the result of VA One software calculations,the error is less than 3d B,which proved the engineering practicability of this method.Since the most empirical formulas of this method came from the regression analysis according to the measurement of real ships or experimental data obtained from testing,those formulas need to be constantly corrected with the advance in machinery technology.It's also a vital work to set up and continuously improve a ship noise database,laying solid foundation to further improve both the accuracy of ship noise forecasting and the speed of calculation in the future.