Abstract

An underwater acoustic sensing system can be used to investigate the characteristics of manganese nodule deposits, such as the nodule size distribution and concentration. We numerically analyzed the relationship between the backscattering intensity obtained using a sub-bottom profiler (SBP) and the manganese nodule distribution by considering higher-order scattering terms among the nodules, in addition to the interaction between wave propagation and the combined effect of the manganese nodules and seafloor. Numerical experiments revealed that complex acoustic reflective waveforms and corresponding spectra increase in complexity with an increase in the sphere size. We categorized this scattering phenomenon with respect to several scattering regimes. As observed, the total reflection response can be attributed to the interference between the scattered waveforms from the nodules and the reflected waveforms from the seabed surface. The laboratory experiments were conducted using actual manganese nodules, and demonstrated a macroscopic decrease in reflectivity with an increase in the area ratio for different nodule sizes. It is, therefore, necessary to eliminate the wave interaction between manganese nodules and the seafloor to quantitatively estimate the density of the nodule distribution.

摘要

水声传感系统可用于研究锰结核矿床的特征，例如结核尺寸分布和浓度。除了波传播与锰结核的综合效应之间的相互作用之外，我们还考虑了结核之间的高阶散射项，对使用次底剖面仪（SBP）获得的后向散射强度与锰结核分布之间的关系进行了数值分析。结核和海底。数值实验表明，复杂的声反射波形和相应的频谱随着球体尺寸的增加而变得复杂。我们根据几种散射机制对这种散射现象进行了分类。据观察，全反射响应可归因于来自结核的散射波形与来自海底表面的反射波形之间的干扰。实验室实验是使用实际的锰结核进行的，结果表明，随着不同结核尺寸的面积比的增加，反射率会出现宏观下降。因此，有必要消除锰结核与海底之间的波相互作用，以定量估计锰结核分布的密度。