Research On Prediction Of Low Frequency Sound Radiated From Elastic Cylindrical Shell In Non-anechoic Pool

At present,the research on acoustic radiation prediction of underwater structures is mainly focused on the free field environment,but in fact,the free field environment is difficult while the measurement of non-anechoic pool is relatively easy to achieve.In this paper,the elastic cylindrical shell is taken as the research object,aiming at the problem of low-frequency sound radiation prediction in non-anechoic pool,the low-frequency sound radiation of structure in free field is predicted by measuring the vibration of structure in non-anechoic pool combined with the efficiency in free field.The key to the prediction is the similar vibration in nonanechoic pool and free field.The method presented in this paper has guiding significance for evaluating the free-field acoustic radiation level of large underwater structures based on pool vibration measurement.Compared with non-anechoic pool,the main difference of anechoic tank is limited water body and wall impedance.Therefore,this paper focuses on the influence of boundary condition of tank on structural surface vibration,compares the difference between shell surface vibration and free field under different volume ratio of model and tank,and analyses the cause of change from impedance.The peak value of vibration is explained on the point of resonance mode.At the same time,the influence of model parameters and position on the structure surface vibration is also studied.The results show that the calculated results under different boundary conditions are basically the same.With the increase of the volume ratio of the model to the tank,the difference between the vibration in the tank and the free field increases gradually.The single-layer cylindrical shell is selected as the test model,and the experiments are carried out in non-anechoic tank and anechoic tank respectively.The vibration of cylindrical shell structure is collected in non-anechoic tank,as well in anechoic tank,and sound pressure are also collected in anechoic tank.The comparison between the vibration of structure in nonanechoic environment and in free field is verified,and the test results are basically consistent with the simulation rules.The calculated radiation efficiency combined with the mean square velocity in the non-anechoic environment can predict the radiated sound power of the structure in the free field,and the average prediction precision is less than 2dB.