海面ダクトモードの近似理論

概要

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Surface duct sound propagation in water is an important problem in underwater acoustics. There are many articles on this problem, but few ones consider the effect of lossy surface which represents an actual ocean surface with wind. In this report the general theory to obtain the approximate depth functions and eigenvalues taking account of the lossy surface is described. The depth function is expressed as a sum of perturbed terms with lossy parameters. In the case of a parabolic sound velocity profile and of a loss free surface, of which exact solutions can be easily obtained, these approximate solutions are compared with the exact ones. Except for the vicinity of the turning point, the present approximate solutions agree well with the exact ones. The effect of lossy surface to the depth functions is sensitive in the neibourhood of sea surface. The present analysis shows that the lossy surface is very important and can not be neglected to design the SONAR system and to predict the performance of SONAR system. It is assumed that the water layer is horizontally stratified medium, and the sound velocity profile is monotonously increasing function with the depth coordinate only. The latter is very important to analyze the effect of lossy surface to obtain the eigenvalues and the depth functions of surface-duct-trapping-mode, because the effect of sea bottom can be neglected by virtue of such profile.
社団法人日本音響学会の論文
1980-06-01