This study were looks at the effect of the initial cut length or stress concentration level, on the wave forms produced by crack propagation. The signals were collected, then classified visually for each type of sample. They were put into three classes according to their shapes in the time and frequency domain. Each class should domain signals which could be correlated to a certain micro-failure mechanism that occurs during the fatigue process. Classes of these signals compared, with each sample. To see if there were any classes common to the three samples. The fatigue test attempted to determine if the initial cut length has any influence on the type of signals.