Distinction between crack echoes and rebar echoes based on Morlet Wavelet Transform of impact echo signals

In an Impact-Echo (IE) test, the Fast Fourier transform (FFT) of the impacted surface responses reveals frequency peaks of major periodical events and can be used to determine depth information, such as the thickness of a target specimen and the depth of a delaminated crack. Since rebar interfaces also result in comparable spectral frequencies but with different depth characteristics, IE testers might have difficulty to determine whether a...