Muzi Lanfranco, Siderius Martin, Quijano Jorge E, Dosso Stan E
Department of Electrical and Computer Engineering, Portland State University, 1900 Southwest 4th Avenue, Portland, Oregon 97201.
School of Earth and Ocean Sciences, University of Victoria, 3800 Finnerty Road, Victoria, British Columbia V8P 5C2, Canada.
J Acoust Soc Am. 2015 Jan;137(1):481-91. doi: 10.1121/1.4904508.
The seabed reflection loss (shortly "bottom loss") is an important quantity for predicting transmission loss in the ocean. A recent passive technique for estimating the bottom loss as a function of frequency and grazing angle exploits marine ambient noise (originating at the surface from breaking waves, wind, and rain) as an acoustic source. Conventional beamforming of the noise field at a vertical line array of hydrophones is a fundamental step in this technique, and the beamformer resolution in grazing angle affects the quality of the estimated bottom loss. Implementation of this technique with short arrays can be hindered by their inherently poor angular resolution. This paper presents a derivation of the bottom reflection coefficient from the ambient-noise spatial coherence function, and a technique based on this derivation for obtaining higher angular resolution bottom-loss estimates. The technique, which exploits the (approximate) spatial stationarity of the ambient-noise spatial coherence function, is demonstrated on both simulated and experimental data.
海底反射损耗（简称为“海底损耗”）是预测海洋中传输损耗的一个重要量。最近一种将海底损耗估计为频率和掠射角函数的被动技术，利用海洋环境噪声（起源于海面的破浪、风和雨）作为声源。在水听器垂直线列上对噪声场进行传统的波束形成是该技术的一个基本步骤，并且波束形成器在掠射角上的分辨率会影响估计的海底损耗的质量。短阵列实施该技术可能会受到其固有角分辨率差的阻碍。本文给出了从环境噪声空间相干函数推导海底反射系数的方法，以及基于该推导获得更高角分辨率海底损耗估计的技术。该技术利用了环境噪声空间相干函数的（近似）空间平稳性，并在模拟数据和实验数据上进行了验证。
