Prediction of sound radiation from submerged structure by transfer method based on measuring vibration

Abstract

A prediction method of submerged structure sound radiation is presented, in which the measured structure vibration data is processed to obtain sound radiation by a transfer method. For an underwater vehicle, its own vibration and sound radiation usually needs to be known accurately. Therefore, accurate prediction of sound radiation from submerged structures is of great significance. As we know, the generation of radiated sound by a submerged structure is a very complicated process. Consequently, it is very difficult to predict radiated noise by monitoring submerged structure vibration. Traditionally, BEM methodology is suitable for solving the problem of the acoustic field calculation by known structure vibration. However, the required number of measuring vibration points is very large; and, vibration phase information needs to be measured accurately - but we know that these requirements are difficult to be satisfied in practice. Therefore, this paper proposes a method of sound radiation prediction of submerged structures by using a transfer method. As we know, under the action of an excitation force sound radiation of a submerged structure is generally a linear system, so the radiation field is proportional to the structure vibration. For an experimental structure model, the structural vibration and the sound radiation field can be calculated by theoretical modeling, and their transfer relationship can be derived easily. Then the sound radiation field can be predicted according to the structure vibration data obtained by experiment. In this paper, the structure vibration is described by the mean square velocity, and sound radiated power is concerned with sound radiated field. For the underwater cylindrical shell model, the simulation calculation is carried out with LMS Virtual Lab software; and, the transfer relationship between the structure mean square velocity and sound radiated power is investigated for different force excitation cases. Then, a measuring experiment is carried out for a cylindrical shell model. By measuring vibration acceleration of the cylindrical shell, the sound radiated power of the model is predicted by a transfer method. The predicted result has a good agreement with the directly measured sound radiated power. The experiment result shows that this paper's prediction method is feasible. In this paper, the prediction method of sound radiation is suitable for engineering application, which has the advantages of needing fewer measuring points and also no need to measure the phase information.