Perception of pitch in pulse wave forms whose power spectra are flat

The time waveform of a stimulus was used to determine the upper limits of pitch perception in human subjects. Investigation of the short term spectrum of the random polarity pulse train reveals clues to the pulse rate even though the long term power spectrum is flat. One such clue is the different probability distribution of the amplitude peaks at frequencies of nfp/2 where fp is the pulse rate. This variability of amplitude distribution can be reduced, and the frequencies which then occur changed, by using polarity patterns randomly chosen from a certain set of patterns. However, experiments performed using pulse patterns showed little or no change in the subjects' ability to match.