Research On The Correlation Between The Ship Underwater Radiation Noise And The Cabin Noise

With the ship's comfort requirements continuously improving,the cabin noise control attracts more and more attention,especially for many ships under construction.In recent years,there are more abnormal behaviors of marine mammal.Marine species' important hearing systems and even the marine environment are have been seriously damaged by human activities.The legislation of underwater radiation noise control of civilian ship seems to be in front of us,so in the beginning of the ship building,the accurate prediction of ship cabin noise,fast prediction of underwater radiation noise,vibration and noise reduction scheme are in great request,nip in the bud,which is very important.Statistical energy analysis method is different from other numerical simulation method such as finite element analysis method,based on statistical theory,from the energy point of view.The complex ship structure is divided into several SEA subsystems,do not solve the structural mode,but through the modal density,loss factor,coupling loss factors,put them into the power flow balance equation,get the subsystem response.This method has many advantages such as fast calculation speed,easy to modify,suitable for high frequency calculation and others.First of all,we take the 72000 DWT crude oil tanker as an example,based on VA One,applied the statistical energy analysis method,to predict the cabin noise level.SEA parameters,model building,noise source loading,NCT settings,simulation of energy transfer of nacelle have all been described in detail.The results show that the noise levels of 9 cabins exceed the standard,so modify NCTs of these cabins as to meet the specification requirements.Secondly,introduce the semi infinite fluid calculation function.Based on the prediction of the cabin noise level,arrange 168 monitoring points under the 72000 DWT crude oil tanker.The characteristics of underwater radiated noise are predicted,and the directivity and propagation attenuation are analyzed.Finally,applied grey relational analysis method,regard the sound pressure level of monitor as the reference sequence and regard the sound pressure level of monitor when each device is turned on alone as the compare sequence,to explore the correlation between the underwater radiated noise and the cabin noise,sort and analyze them.By installing vibration isolator and silencer for noise source,the underwater radiation noise level can be reduced effectively,and also proved the applicability of grey correlation theory.The source of underwater radiation is complex,and the radiation noise level is affected by the working conditions and environment.It is difficult to quantify the effect of cabin radiation noise on the underwater radiation noise.In this paper,the statistical energy analysis method is used to predict the noise,and the grey correlation analysis theory is used to study the sources of radiation noise,which is of great significance for noise prediction and control of underwater radiated noise.