The parameters of waveform that enable listeners to recognize repetition of patterns within a signal were explored by using four types of waveform called random-amplitude constant-period, constant-amplitude random-period, random-amplitude random-period cophasic, and random-amplitude random-period antiphasic. The measure used for comparison was the number of repetitions per signal required to differentiate signals containing repetitions from random waveforms that did not contain repetitions. In the first experiment reported, the subject's performance was kept at 75% correct differentiation by varying the number of repetitions per signal. The comparisons were made among all four types of waveforms at each of three sensation levels: 20, 50, and 80 dB. Signals with zero-crossing information (random period) and signals of medium sensation level appear best for recognition of the repetition of patterns. In the second experiment, the same type of signals were high-pass or low-pass filtered, and similar comparisons were run. Although absolute comparisons were not possible, it appears that high-frequency information is more useful than low to the auditory system in identifying the repetitions within signals. A third experiment explored the possibility that one type of signal waveform is more readily learned than another. To make the task more difficult, segments of either noise or silence were inserted between the repetitions of the patterns, and were introduced with the same spacing into the nonrepeated waveforms. Repetition of pattern was still too easily recognized by the subjects, and no evidence of any difference in rate of learning to recognize patterns was found for the different types of waveform.