The Pennsylvania State University, Applied Research Laboratory, State College, Pennsylvania 16804, USA.
J Acoust Soc Am. 2012 Feb;131(2):1066-78. doi: 10.1121/1.3672696.
Seabed geoacoustic variability is driven by geological processes that occur over a wide spectrum of space-time scales. While the acoustics community has some understanding of horizontal fine-scale geoacoustic variability, less than O(10(0)) m, and large-scale variability, greater than O(10(3)) m, there is a paucity of data resolving the geoacoustic meso-scale O(10(0)-10(3)) m. Measurements of the meso-scale along an ostensibly "benign" portion of the outer shelf reveal three classes of variability. The first class was expected and is due to horizontal variability of layer thicknesses: this was the only class that could be directly tied to seismic reflection data. The second class is due to rapid changes in layer properties and/or boundaries, occurring over scales of meters to hundreds of meters. The third class was observed as rapid variations of the angle/frequency dependent reflection coefficient within a single observation and is suggestive of variability at scales of meter or less. Though generally assumed to be negligible in acoustic modeling, the second and third classes are indicative of strong horizontal geoacoustic variability within a given layer. The observations give early insight into possible effects of horizontal geoacoustic variability on long-range acoustic propagation and reverberation.
海底地球声学可变性是由在广泛的时空尺度上发生的地质过程驱动的。虽然声学界对水平细尺度的地球声学可变性（小于 O(10(0)) m）和大尺度可变性（大于 O(10(3)) m）有一定的了解，但对于 O(10(0)-10(3)) m 的地球声学中尺度的可变性数据却很少。在一个外陆架表面上看似“良性”的部分，对中尺度的测量揭示了三类可变性。第一类是预期的，是由于层厚度的水平变化引起的：这是唯一可以直接与地震反射数据联系起来的类别。第二类是由于层特性和/或边界的快速变化引起的，其发生的尺度为几米到几百米。第三类是在单个观测中观察到的角度/频率相关反射系数的快速变化，表明在米或更小的尺度上存在可变性。尽管在声学模型中通常被认为是可以忽略不计的，但第二和第三类都表明在给定的层内存在强烈的水平地球声学可变性。这些观测结果为水平地球声学可变性对远程声传播和混响的可能影响提供了早期的见解。
