Jackson Darrell, Olson Derek R
Applied Physics Laboratory, University of Washington, Seattle, Washington 98105, USA.
Oceanography Department, Naval Postgraduate School, Monterey, California 93943, USA.
J Acoust Soc Am. 2020 Jan;147(1):56. doi: 10.1121/10.0000470.
The small-slope approximation (SSA) for rough-interface scattering is most commonly applied to the upper boundary of either impenetrable media or uniform half-space media, but has been recently developed for layered media in the acoustic and electromagnetic cases. The present work gives an overview of three forms of the SSA for layered media. The first has been previously presented in the acoustics literature. The second is from the electromagnetics literature and in the present work is converted to the fluid-sediment problem. A missing proof is supplied of a key consistency condition demanded of the small-slope ansatz. As is usual, these small-slope results are expressed in k-space. A third SSA for layered seafloors follows from conversion of the usual half-space formulation from k-space to coordinate space. This form turns out to be useful for reverberation simulations. The three different approaches are compared with respect to scattering strength and the coherent reflection coefficient, but an assessment of their relative merits will require comparison with exact calculations.
粗糙界面散射的小斜率近似（SSA）最常用于不可穿透介质或均匀半空间介质的上边界，但最近已在声学和电磁学情况下针对分层介质进行了发展。本文概述了分层介质的三种SSA形式。第一种先前已在声学文献中提出。第二种来自电磁学文献，在本文中被转换为流体-沉积物问题。给出了小斜率假设所需的一个关键一致性条件的缺失证明。与通常情况一样，这些小斜率结果在k空间中表示。分层海底的第三种SSA是通过将通常的半空间公式从k空间转换到坐标空间得到的。这种形式对于混响模拟很有用。比较了这三种不同方法在散射强度和相干反射系数方面的情况，但对它们相对优点的评估将需要与精确计算进行比较。
