Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
J Acoust Soc Am. 2012 Aug;132(2):680-93. doi: 10.1121/1.4726073.
Bistatic, long-range measurements of acoustic scattered returns from vertically extended, air-filled tubular targets were made during three distinct field experiments in fluctuating continental shelf waveguides. It is shown that Sonar Equation estimates of mean target-scattered intensity lead to large errors, differing by an order of magnitude from both the measurements and waveguide scattering theory. The use of the Ingenito scattering model is also shown to lead to significant errors in estimating mean target-scattered intensity in the field experiments because they were conducted in range-dependent ocean environments with large variations in sound speed structure over the depth of the targets, scenarios that violate basic assumptions of the Ingenito model. Green's theorem based full-field modeling that describes scattering from vertically extended tubular targets in range-dependent ocean waveguides by taking into account nonuniform sound speed structure over the target's depth extent is shown to accurately describe the statistics of the targets' scattered field in all three field experiments. Returns from the man-made targets are also shown to have a very different spectral dependence from the natural target-like clutter of the dominant fish schools observed, suggesting that judicious multi-frequency sensing may often provide a useful means of distinguishing fish from man-made targets.
在三个不同的波动大陆架波导现场实验中，对垂直延伸的充满空气的管状目标的声波散射回波进行了静态、远程测量。结果表明，声呐方程对平均目标散射强度的估计会导致很大的误差，与测量值和波导散射理论相差一个数量级。Ingenito 散射模型的使用也被证明会导致在现场实验中估计平均目标散射强度时出现显著误差，因为这些实验是在海洋环境中进行的，其中目标深度上的声速结构变化很大，这违反了 Ingenito 模型的基本假设。基于格林定理的全场建模，通过考虑目标深度上的非均匀声速结构，描述了在时变海洋波导中垂直延伸管状目标的散射，结果表明，该模型能够准确地描述所有三个现场实验中目标散射场的统计特性。结果还表明，人造目标的回波与观察到的主要鱼类群体的自然目标状杂波在谱依赖性上有很大的不同，这表明明智的多频感测通常可能是区分鱼类和人造目标的一种有用手段。
