Abstract

An experimental study aimed at the measurement of arrival times and effective velocities of acoustical pulses propagating approximately along the edge of the continental shelf was conducted in the Sea of Japan in early autumn. In a posteriori theoretical analysis and modeling of sound propagation in this experiment modal structure of acoustical field along the path was described and a number of general conclusions on the formation of such fields in course of sound propagation over distances of tens and hundreds of kilometers were formulated. An algorithm for predicting effective velocities of long-range propagation of acoustical pulses in shallow water was developed on the basis of these conclusions. The algorithm is based on the averaging of group velocities of the first modal component of the pulse over the entire track. It was shown that on the considered path of approximately 136 kilometers horizontal refraction is one of the major factors contributing to the dispersion of pulsed signals. This effect also causes additional delays as compared to the sound propagation along the respective geodesic path on the Earth’s surface. Implications of the importance of taking the horizontal refraction into account in estimation of arrival times in the modeling of long-range propagation and the solution of acoustical ranging problems are also discussed.

中文翻译：

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浅海沿架缘长距离传播声脉冲的到达时间和有效速度的实验和理论研究

摘要

初秋在日本海进行了一项旨在研究沿大陆架边缘传播的声脉冲的到达时间和有效速度的实验研究。在该实验的声音传播的后验理论分析和建模中，描述了沿路径的声场的模态结构，并就在数十公里和数百公里的距离内传播声音过程中形成这种场的一些一般性结论提出了一些结论。基于这些结论，提出了一种预测声脉冲在浅水中远距离传播的有效速度的算法。该算法基于整个轨迹上脉冲的第一模态分量的群速度的平均值。结果表明，在所考虑的大约136公里的路径上，水平折射是造成脉冲信号色散的主要因素之一。与沿地球表面上各自测地线路径传播的声音相比，此效应还会引起额外的延迟。还讨论了在远距离传播建模中考虑水平折射对到达时间的估计的重要性以及声学测距问题的解决方案。