Investigation On Acoustic Holography Technique For Main Sound Sources Identification Of The Targets Near Water Surface

Near field acoustic holography technology came into being in the 1980s. It is the technique of reconstructing acoustic quantities at any point in three-dimensional acoustic field by utilizing the measured acoustic pressure vector on the hologram surface, such as acoustic pressure, particle velocity, acoustic intensity directionality of farther field and so on. Because of such special features, the NAH technique becomes one of the most powerful tools to identify and locate sound sources and visualize sound field. At the present time, most of the research is focused on the reconstruction of sound radiation from the vibrating structure in no-boundary space (free acoustic field). However, in the engineering applications, there are a lot of noise sources in the semi-free space, such as the main sound source of the targets near water surface, NAH technology applying to free acoustic field can not realize the sound source identification and localization exactly. Therefore, the research on the acoustic field reconstruction under the semi-free acoustic field condition is very important for acoustic holography technology in the practical application.On the basis of the sufficient research on the boundary element theory and semi-free field acoustic holography technology, many problems on the sound source identification for targets near water surface have been studied in this dissertation, including deducing a theoretical model for semi-free space NAH based on BEM, developing a reconstruction algorithm program for semi-free acoustic field based on BEM, and the regularized treatment to solve ill-posed problem in the reconstruction process and the selection criteria for filtering parameter.In order to give reasonable suggestions to the parameter selection in the practical measurement, in this article, theoretic numerical verification for effectiveness of the algorithm to identify and locate the sound source was carried out by selecting a variety of different acoustic source models and the effects of different parameters to the sound field reconstruction precision was discussed. The feasibility and effectiveness of this theoretical model have also been verified through experiments. The research results show that it's an efficiency way for dealing with the problem of the affection of the reflected acoustic pressure from the boundary surface on acoustic field reconstruction by NAH in semi-space, and it makes this technique more useful in practice. Thus it expands the engineering application range and the practicability of the holography technology.