Hopps-McDaniel Alexandra M, Neilsen Tracianne B, Knobles D P, Hodgkiss William S, Wilson Preston S, Sagers Jason D
Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA.
The Platt Institute, P.O. Box 27200, Austin, Texas 78755, USA.
J Acoust Soc Am. 2024 Oct 1;156(4):2265-2274. doi: 10.1121/10.0030467.
The very low-frequency noise from merchant ships provides a good broadband sound source to study the deep layers of the seabed. The nested striations that characterize ship time-frequency spectrograms contain unique acoustic features corresponding to where the waveguide invariant β becomes infinite. In this dataset, these features occur at frequencies between 20 and 80 Hz, where pairs of modal group velocities become equal. The goal of this study is to identify these β = ∞ frequencies in ship noise spectrograms and use them to perform statistical inference for the deep layer sound speeds and thicknesses in the New England Mudpatch for a larger number of ships and acoustic arrays over a larger geographical region than previously studied. Marginal probability distributions of the data indicate that using singular points for a feature-based inversion yields an estimate of the sound speed and a limiting value for the thickness of the first deep layer. Heterogeneity is examined by correlating spatial variability of the deep layer sound speeds with ship tracks.
商船产生的极低频噪声为研究海床深层提供了一个良好的宽带声源。表征船舶时频频谱图的嵌套条纹包含与波导不变量β变为无穷大的位置相对应的独特声学特征。在该数据集中，这些特征出现在20至80赫兹之间的频率处，此时模态群速度对变得相等。本研究的目标是在船舶噪声频谱图中识别这些β = ∞频率，并利用它们对新英格兰泥滩深层的声速和厚度进行统计推断，涉及的船舶数量和声学阵列比之前研究的更多，地理区域也更大。数据的边际概率分布表明，使用基于特征的反演中的奇点可得出声速估计值和第一深层厚度的极限值。通过将深层声速的空间变异性与船舶航迹相关联来检验非均匀性。
