The National Oceanic and Atmospheric Administration/Earth System Research Laboratory, 325 Broadway, Boulder, Colorado 80303, USA.
J Acoust Soc Am. 2011 Jun;129(6):3590-7. doi: 10.1121/1.3533726.
Temporal coherence of acoustic signals propagating in a fluctuating ocean is important for many practical applications and has been studied intensively experimentally. However, only a few theoretical formulations of temporal coherence exist. In the present paper, a three-dimensional (3D) modal theory of sound propagation in a fluctuating ocean is used to derive closed-form equations for the spatial-temporal coherence function of a broadband signal. The theory is applied to the analysis of the temporal coherence of a monochromatic signal propagating in an ocean perturbed by linear internal waves obeying the Garrett-Munk (G-M) spectral model. In particular, the temporal coherence function is calculated for propagation ranges up to 10(4) km and for five sound frequencies: 12, 25, 50, 75, and 100 Hz. Then, the dependence of the coherence time (i.e., the value of the time lag at which the temporal coherence decreases by a factor of e) on range and frequency is studied. The results obtained are compared with experimental data and predictions of the path-integral theory.
在波动海洋中传播的声信号的时域相干性对于许多实际应用非常重要，并且已经进行了大量的实验研究。然而，目前仅有少数的时域相干性理论公式。本文利用波动海洋中的三维（3D）模态理论，推导出宽带信号的时空相干函数的封闭形式方程。该理论应用于分析线性内波调制的海洋中单色信号的时域相干性，内波符合 Garrett-Munk（G-M）谱模型。特别地，计算了传播范围高达 10^4 km 时的五个声频率（12、25、50、75 和 100 Hz）的相干函数。然后，研究了相干时间（即相干函数降低到 e 的倍数时的时间滞后值）与距离和频率的关系。将得到的结果与实验数据和路径积分理论的预测进行了比较。
