Research On Underwater Acoustic Field Measurement System Based On Near-field Measurement Method

In recent years,hydroacoustic transducers have developed in the direction of large size and high power.The measurement of the performance in far field was always limited by the size of the experimental water.What's more,in the measurement of the focal point parameters of the focusing field,the measurement equipment was easily damaged by the high energy.In order to solve these problems,a new technique of underwater acoustic field measurement,namely near-field measurement method was introduced,then the acoustic field distribution in the far field and focus was predicted by the measurement of the acoustic field of the near field plane and the focal plane.The underwater acoustic field measurement system was designed and carried out theortical and experimental researches.In chapter one,the background and significance of the research were stated;the current method of underwater acoustic field measurement and near-field measurement method were reviewed;and the primary coverage of this paper was given.In chapter two,the condition of ideal acoustic field environment and the equation of underwater acoustic propagation were introduced,then the Helmholtz-Kirchhoff theorem was elaborated,and near-field measurement method was given based on Helmholtz-Kirchhoff equation,at last,the discrete expression of the acoustic field parameters in near-field measurement method was derived according to the actual measurement conditions,and the simulation of the radiation field of the planar piston transducer was carried out..In chapter three,the hardware components of the whole system were selected and designed,then the composition of the mechanical structure,the parameters of the motion control card,the form of the transmitted signal and the selection of the received signal were introduced respectively.In chapter four,the software platform of underwater acoustic field measurement system was designed.The function of motion control and the process of sound field measurement were described in detail,and near-field measurement and acoustic field scanning function were integrated through the LabVIEW and MATLAB hybrid programming.In chapter five,the radiation field of planar piston transducer and focused transducer were measured,then the acoustic field distribution in the far field and focal point were predicted and reconstructed based on near-field measurement method,at last,the reliability of the near-field measurement method and the uncertainty of the system were analyzed.In chapter six,former chapters and pointed out the deficiencies were summarized.