Dungan Michael R, Dowling David R
Department of Mechanical Engineering, University of Michigan, Ann Arbor 48109-2121, USA.
J Acoust Soc Am. 2002 Nov;112(5 Pt 1):1842-52. doi: 10.1121/1.1508787.
A time-reversing array (TRA) can retrofocus acoustic energy, in both time and space, to the original sound-source location without any environmental information. This paper presents results from an analytical and computational investigation into the effects that array orientation has on linear TRA retrofocusing in shallow water environments. A linear TRA has three limiting orthogonal orientations with respect to a distant sound source in a shallow water waveguide: vertical, endfire, and broadside. Here, TRA retrofocus characteristics are predicted for monochromatic sound propagation in a Pekeris waveguide using a modal sum Green's function and in a more realistic sound channel having vertical sound speed variation using a computed Green's function. Both analytical and computational results are compared for the three orthogonal array orientations with vertical arrays performing best. Differences in TRA retrofocusing performance in the three orientations are primarily determined by geometrical considerations and the extra mode-shape weighting inherent in the back-propagated field of horizontal TRAs.
时间反转阵列（TRA）能够在无需任何环境信息的情况下，在时间和空间上对声能进行反向聚焦，使其回到原始声源位置。本文展示了关于阵列取向对浅水环境中线性TRA反向聚焦效果的分析和计算研究结果。对于浅水波导中远处的声源，线性TRA有三个极限正交取向：垂直取向、端射取向和宽边取向。在此，使用模态求和格林函数预测了佩克里斯波导中单色声传播时TRA的反向聚焦特性，并使用计算得到的格林函数预测了在具有垂直声速变化的更实际声信道中的TRA反向聚焦特性。针对这三种正交阵列取向，对分析结果和计算结果进行了比较，其中垂直阵列的表现最佳。三种取向中TRA反向聚焦性能的差异主要由几何因素以及水平TRA反向传播场中固有的额外模式形状加权决定。
