Characterization of elastic shells by the use of the wavelet transform

The characterization of elastic targets immersed in a fluid and subjected to an acoustic impulse is discussed. The wavelet transform has been chosen for its particular properties, such as linearity and local analysis at Δf/f=c^ste. An algorithm based on the behavior of the phase of the transform has been developed. It allows the extraction of modulation laws (related to the dispersion law of the phase velocity), even for close echoes. In the case of spherical elastic shells, the method was used on both experimental and computer-generated signals, and the good relation between theoretical and experimental results is presented