界面反射P-SV波转型超声散斑统计特性

对超声P波入射至强散射粗糙界面上时,反射声场中的转型SV波散斑的统计特性进行研究。根据Frensel-Huygens理论和自相关原理,得到了SV波散斑振幅概率密度函数的Rayleigh分布形式以及散斑平均横向尺寸的计算公式。进而又得到了,在使用具有一定尺寸孔径的横波探头时,所接收的SV波散斑的归一化声强的概率密度函数表达式,它与横波探头内接收到的平均散斑个数有关。在实验中,应用了两种不同孔径尺寸的横波探头对SV波的散斑声强进行测量。对测量所得的散斑合强度的数据进行统计分析的结果表明,实验值与理论值有较好的一致性。由此证实,上述理论分析的结果是正确的。

Statistical properties of P-SV mode conversional ultrasonic speckles reflected from an interface

The statistical properties of the mode conversional SV wave speckles in the back scattering space were studied as ultrasonic P waves were incident on a strongly scattering interface. Based on the Frensel-Huygens theory and the correlation principle, the Rayleigh distribution of the SV wave speckle amplitude and the formula for calculating the average transverse size of the SV wave speckles were obtained. Besides, the probability density function of the normalized intensity of the SV wave speckles received by a transverse wave probe with an aperture of some size was deduced. The probability density function was related to the average number of the speckles received by the probe. Two transverse wave probes with apertures in different size were used to measure the sound intensity of the SV wave speckles in the experiment. After the experimental data of the speckle intensity were analyzed statistically, it was shown that the experimental results were in good agreement with the theoretical ones. Thus, the theoretical conclusion described above was proved to be correct.