Investigation On Technique Of Underwater Noise Source Identification By NAH In Semi-Space

Near field acoustic holography technology is an efficient way for noise source identifying. The acoustic quantities, such as acoustic pressure, particle velocity, and acoustic intensity at any point in three-dimensional acoustic field and the radiated sound power can be reconstructed from the measurement of the complex acoustic pressure on the hologram near the sound source.At present, however, most of the research is focused on the reconstruction of sound radiation from the vibrating structure in no-boundary space (free acoustic field). In engineering application, most of the noise sources are set in semi-space, and the properties of the radiated sound field can't be exactly predicted by the technology of full space acoustic holography. Therefore, the research on the acoustic field reconstruction in semi-space is very important for its use in practical conditions.Based on the analysis of the internal and international development of near field acoustic holography, the NAH theory model in half-space has been constructed in this dissertation. The technology of half-space acoustic field reconstruction by NAH has been developed based on FFT in this paper. This method has been verified by numerical calculation. The affection of parameters, such as the location, size, and shape of hologram surfaces and distance between measurement points, on the error of the reconstructed field are analyzed by means of numerical simulation. The feasibility and accuracy of this theory model is validated by experiment. The 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.