Ultrasonic testing methods for concrete structures have got more and more common over the last few years. Beside the separation of the transient signal parts from the background-noise the second very important task is the analysis of the collected signals. The following paper deals with the analysis of signals with high background noise, collected from the wire break signal while breaking down a prestressed concrete structure. In addition to the usually applied signal analysis methods we used the Wavelet-Transformation to show that it is possible the get new important information's connecting the time scale and the frequency scale of the signal.