Marine Physical Laboratory, Scripps Institution of Oceanography University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0238, USA.
J Acoust Soc Am. 2013 Jan;133(1):62-71. doi: 10.1121/1.4768885.
In 2009, as part of PhilSea09, the instrument platform known as Deep Sound was deployed in the Philippine Sea, descending under gravity to a depth of 6000 m, where it released a drop weight, allowing buoyancy to return it to the surface. On the descent and ascent, at a speed of 0.6 m/s, Deep Sound continuously recorded broadband ambient noise on two vertically aligned hydrophones separated by 0.5 m. For frequencies between 1 and 10 kHz, essentially all the noise was found to be downward traveling, exhibiting a depth-independent directional density function having the simple form cos θ, where θ ≤ 90° is the polar angle measured from the zenith. The spatial coherence and cross-spectral density of the noise show no change in character in the vicinity of the critical depth, consistent with a local, wind-driven surface-source distribution. The coherence function accurately matches that predicted by a simple model of deep-water, wind-generated noise, provided that the theoretical coherence is evaluated using the local sound speed. A straightforward inversion procedure is introduced for recovering the sound speed profile from the cross-correlation function of the noise, returning sound speeds with a root-mean-square error relative to an independently measured profile of 8.2 m/s.
2009 年，作为 PhilSea09 的一部分，名为 Deep Sound 的仪器平台在菲律宾海部署，它在重力作用下下降到 6000 米的深度，在那里它释放了一个重物，让浮力将其带回水面。在下降和上升过程中，Deep Sound 以 0.6 m/s 的速度连续在两个垂直排列的水听器上记录宽带环境噪声，两个水听器之间的间隔为 0.5 m。对于 1 到 10 kHz 之间的频率，基本上所有的噪声都是向下传播的，表现出具有简单形式 cosθ的与深度无关的方向密度函数，其中θ≤90°是从天顶测量的极角。噪声的空间相干性和互谱密度在临界深度附近没有表现出特征变化，与局部风驱动的表面声源分布一致。相干函数与深水风成噪声的简单理论模型非常吻合，只要使用局部声速来评估理论相干性。本文介绍了一种从噪声互相关函数中恢复声速剖面的直接反演方法，从互相关函数中恢复的声速剖面与独立测量的剖面相比，均方根误差为 8.2 m/s。
