The major task of imaging systems used in non-destructive testing is detection of defects (flaws, holes) echoes and evaluation or their dimensions and position. Images generated by direct imaging are poor quality due to diffraction, coherent echoes, limited capabilities of system, white noise. So acoustic images and optic images are very different. Solving these problems, numerical methods are used for signal processing and analysis. An application for ultrasonic signal processing of wavelet transformations was investigated in the work. The investigation was signals distortion type and level when wavelets transformation may give effective results. The investigation was performed using modeling and signal processing of the experimental signals.