Acoustic scattering-based technique is one major approach for characterization purposes and non-destructive testing of structures. This paper investigates the acoustic scattering of a progressive plane wave from two-layered stainless steel/polymer cylindrical shell. The time–frequency techniques are used to study the acoustic scattering from the considered structure. The use of these techniques allows to extract the group velocity and cutoff frequency of circumferential waves. From a temporal signal it is difficult to identify the echoes of different circumferential waves due to the overlapping. To overcome this shortcoming, digital filtering is used to isolate the contribution of each circumferential wave to the total temporal acoustic signal. The time–frequency image of each wave is then constructed using Reassignment Smoothed Pseudo Wigner–Ville (RSPWV) and Reassignment Gabor Transform (RGT). The constructed image can be considered as an acoustic signature of the considered structure. The achieved results show that the time–frequency representation and plane of modal identification can be considered as an alternative of the proper modes theory which is practical in the case of homogeneous structures.

中文翻译：

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用于表征双层圆柱壳的圆周波信号处理技术

基于声学散射的技术是一种用于结构表征和非破坏性测试的主要方法。本文研究了来自两层不锈钢/聚合物圆柱壳的渐进平面波的声散射。时频技术用于研究所考虑结构的声学散射。这些技术的使用允许提取圆周波的群速度和截止频率。由于重叠，从时间信号中难以识别不同圆周波的回波。为了克服这个缺点，使用数字滤波来隔离每个圆周波对总时间声信号的贡献。然后使用重新分配平滑伪 Wigner-Ville (RSPWV) 和重新分配 Gabor 变换 (RGT) 构建每个波的时频图像。构建的图像可以被视为所考虑结构的声学特征。取得的结果表明，时频表示和模态识别平面可以被认为是适当模态理论的替代方案，这在均匀结构的情况下是实用的。