Holland Charles W
Applied Research Laboratory, The Pennsylvania State University, State College, Pennsylvania 16803, USA.
J Acoust Soc Am. 2010 Nov;128(5):2596-609. doi: 10.1121/1.3488348.
The ocean environment contains features affecting acoustic propagation that vary on a wide range of time and space scales. A significant body of work over recent decades has aimed at understanding the effects of water column spatial and temporal variability on acoustic propagation. Much less is understood about the impact of spatial variability of seabed properties on propagation, which is the focus of this study. Here, a simple, intuitive expression for propagation with range-dependent boundary properties and uniform water depth is derived. It is shown that incoherent range-dependent propagation depends upon the geometric mean of the seabed plane-wave reflection coefficient and the arithmetic mean of the cycle distance. Thus, only the spatial probability distributions (pdfs) of the sediment properties are required. Also, it is shown that the propagation over a range-dependent seabed tends to be controlled by the lossiest, not the hardest, sediments. Thus, range-dependence generally leads to higher propagation loss than would be expected, due for example to lossy sediment patches and/or nulls in the reflection coefficient. In a few instances, propagation over a range-dependent seabed can be calculated using range-independent sediment properties. The theory may be useful for other (non-oceanic) waveguides.
海洋环境包含影响声传播的各种特征，这些特征在广泛的时间和空间尺度上变化。近几十年来，大量的研究工作旨在了解水柱时空变化对声传播的影响。而对于海底特性的空间变化对传播的影响，人们了解得较少，这正是本研究的重点。在此，我们推导了一个关于具有距离依赖边界特性和均匀水深情况下传播的简单直观表达式。结果表明，非相干距离依赖传播取决于海底平面波反射系数的几何平均值和周期距离的算术平均值。因此，只需要沉积物特性的空间概率分布。此外，研究还表明，在距离依赖海底上的传播往往由损耗最大而非最坚硬的沉积物控制。因此，距离依赖性通常会导致比预期更高的传播损耗，例如由于损耗性沉积物斑块和/或反射系数中的零点。在少数情况下，可以使用与距离无关的沉积物特性来计算在距离依赖海底上的传播。该理论可能对其他（非海洋）波导也有用。
