吸収性海底媒質による浅海面モード減衰

概要

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Recently theories for shallow water normal mode propagation of sound have been studied for low frequency and long rage problems and some experiments on mode enhancement have been reported. The normal mode theory contains mathematical difficulties in order to design model SONAR systems, and the ray theory, on the other hand, is not applicable for these problems. In this paper, based on the normal mode theory, some formulae are derived to design model SONAR systems and to analyze acoustic field in shallow water. Pekeris model is used for shallow water. Comparing approximate and exact solutions of vertical wave number eigenvalues for sand and mud bottoms, it is shown that approximate formulae are quite useful. Using theses approximate eigenvalues mode attenuation coefficients due to lossly bottom are derived and compared with the experimental values. They agree well with each other. It is also shown that higher modes decrease rapidly with the distance due to bottom absorption and therefore the dominant contribution of sound field at long range is the lower modes in real shallow water.
社団法人日本音響学会の論文
1980-06-01