Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA.
Scripps Institution of Oceanography, La Jolla, California 92093-0225, USA.
J Acoust Soc Am. 2019 Sep;146(3):1913. doi: 10.1121/1.5125427.
A significant aspect of bottom-interaction in deep water acoustic propagation, from point sources to point receivers, is the diffraction (or scattering) of energy from discrete seafloor locations along repeatable, deterministic paths in three-dimensions. These bottom-diffracted surface-reflected (BDSR) paths were first identified on the North Pacific acoustic laboratory experiment in 2004 (NPAL04) for a diffractor located on the side of a small seamount. On the adjacent deep seafloor, ambient noise and propagation in the ocean sound channel were sufficiently quiet that the BDSRs were the dominant arrival. The ocean bottom seismometer augmentation in the North Pacific (OBSANP) experiment in June-July 2013 studied BDSRs at the NPAL04 site in more detail. BDSRs are most readily identified by the arrival time of pulses as a function of range to the receiver for a line of transmissions. The diffraction points for BDSRs occur on the relatively featureless deep seafloor as well as on the sides of small seamounts. Although the NPAL04 and OBSANP experiments had very different geometries the same diffractor location is consistent with observed arrivals in both experiments within the resolution of the analysis. On OBSANP the same location excites BDSRs for 77.5, 155, and 310 Hz transmissions.
深海水声传播中，从点源到点接收器，底部相互作用的一个重要方面是能量从离散海底位置沿着三维可重复的、确定性路径的绕射（或散射）。这些底部绕射表面反射（BDSR）路径在 2004 年北太平洋声学实验室实验（NPAL04）中首次被识别出来，当时一个绕射器位于一个小海山的一侧。在相邻的深海海底，环境噪声和海洋声道中的传播足够安静，以至于 BDSR 是主要的到达信号。2013 年 6 月至 7 月进行的北太平洋海底地震仪增强（OBSANP）实验更详细地研究了 NPAL04 地点的 BDSR。BDSR 最容易通过脉冲的到达时间来识别，作为接收者到发射器的距离的函数。BDSR 的绕射点出现在相对无特征的深海海底以及小海山的侧面。尽管 NPAL04 和 OBSANP 实验的几何形状非常不同，但相同的绕射器位置与两个实验中的观测到达信号一致，在分析的分辨率范围内。在 OBSANP 上，相同的位置激发了 77.5、155 和 310Hz 传输的 BDSR。
