Harrison Chris H
NATO Undersea Research Centre, La Spezia, Italy.
J Acoust Soc Am. 2009 Jun;125(6):3511-3. doi: 10.1121/1.3126345.
The impulse response of the seabed can be extracted from sea surface ambient noise by cross-correlating the time series from an upward and a downward steered beam. When the steering for each beam is standard minimum variance adaptive beam forming it has been found that the impulse response for significant echoes appears to have the same amplitude but opposite sign. A mathematical explanation is offered for this strange phenomenon. Crucial contributing factors are that the cross-spectral density matrix for the vertical array typically consists of the sum of a Toeplitz matrix and a much weaker Hankel matrix and that it is ill-conditioned.
通过对向上和向下指向波束的时间序列进行互相关，可以从海面环境噪声中提取海底的脉冲响应。当每个波束的指向采用标准最小方差自适应波束形成时，已发现显著回波的脉冲响应似乎具有相同的幅度但符号相反。针对这一奇怪现象给出了数学解释。关键的促成因素是垂直阵列的互谱密度矩阵通常由一个托普利兹矩阵和一个弱得多的汉克尔矩阵之和组成，并且它是病态的。
