A new tool for impact-echo measurements: wavelet transform

摘要

Impact-echo is one of the conventional methods used for depth or thickness measurements of concrete structures. However, due to the anisotropic characteristics of concrete, received signals are noisy and multiple back-wall echoes are often very difficult to identify in the time domain. In frequency domain analysis, it is also frequently difficult to select the dominant frequency peak on an impact-echo spectrum to calculate a structure's depth. Wavelet transform is a newly developed powerful tool for signal analysis, compression and de-noising. With the assistance of this tool, received, noisy impact-echoes can be transformed, and periodic multiple echoes corresponding to back-wall echoes are indicated clearly on two-dimensional scalograms. Consequently, depth or thickness measurements for concrete structures can be made more reliable.