Pitch strength of ripple noise

Abstract

Ripple noise is produced when a broadband noise is delayed (T) and either added to or subtracted from the original noise. The resulting waveform has a power spectrum in which power varies cosinusoidally as a function of frequency. Ripple noise has been used to study pitch perception and echo processing. In the present experiments subjects were asked to discriminate between two noises which differed in the amount of delay introduced (one stimulus continued a delay T the second stimulus a delay T + 0.09T). The discriminability of these two noises was studied as a function of the amount of attenuation added to the delayed noise. Discriminations between these two noises could be made when T ranged from 0.5 to 20 msec before the subjects could no longer make the discrimin-delayed noise when the delays were in the range from 2 to 5 msec before the subjects could no longer make the discriminations. More attenuation could be added to the delayed noise for threshold discrimination when it was added back to the original source than when it was subtracted from the original source than when it was subtracted from the original source. Discrimination did not change as a function of octave band filtering the ripple noise when the center frequency of the filters varied from 200 to 3200 Hz. The results will be discussed in terms of pitch perception, especially in regard to the concept of a spectral dominance region for pitch and pitch strength. The data will also be related to the echo processing abilities of the auditory system. [Work supported by NSF.]