If a series of equally spaced ac or dc pulses is delayed in time with respect to an identical series of pulses, a pitch will be heard corresponding to the reciprocal of the smallest delay between adjacent pulses. This study investigates the precision with which listeners are able to match the pitch of a pure tone to that produced by the time separation in a double pulse train. Ten listeners each made 50 pitch matches for six pulse delays at each pulse repetition rate of 25, 100, and 400 pps. The results indicate that the distribution of pitch matches is centered at the reciprocal of the pulse delay. The dispersion of this distribution seems remarkably small, but tends to widen as pulse delay is shortened, especially at the highest pulse repetition rate. Although the study was not designed for the investigation of all possibilities, no obvious spectral cue seems to exist which would account for the data. HE pitch associated with a signal whose waveform envelope shows marked periodic fluctuations has interested investigators for some time. B6k•sy, • Schouten, •' and Wever a have summarized early work in this area, while Small 4 and Licklider 5 have reviewed more recent studies. The pitch perception of this class of signals has proven difficult to include within the framework provided by a traditional place theory. A traditional place theory, i.e., one which accepts Ohm's acoustic law 6 and Gray's principle, 7 predicts that the predominant pitch would be associated with that frequency component having the greatest magnitude. For signals whose time envelope shows periodic fluctuations, • G. von B•k•sy, "Pitch Sensation and its Relation to the Periodicity of the Stimulus. Hearing and Skin Vibrations," J.
A situation is described wherein, contrary to previously findings, a pitch related to delay is perceived when a repetitive train of noise bursts is delayed with respect to an identical train, mixed together, and presented monaurally.
Time-separation pitch (TSP) is a pitch effect that arises from temporally separated, highly correlated waveforms and is related to the reciprocal of time delay between the leading edges of such waveforms. On the assumption that spectral cues are responsible for TSP perception, it was suggested that random triggering of dc pulse pairs with fixed time delay would render the spectrum unspecifiable in an exact sense, thereby degrading the performance of subjects matching pure tones in pitch to TSP. On the assumption that a time-analyzing mechanism is responsible for TSP perception, it was predicted that the presentation of single, nonrepetitive dc pulse pairs would make TSP difficult to perceive since minimum information on which to base a pitch judgment would be available per unit time. The results were not as predicted, i.e., the distributions of pitch matches were essentially the same for conditions of random triggering and single pulse pairs and were highly similar to those generated with regularly triggered dc pulse pairs. These results suggest that the amount of "information" available per unit time is not particularly important to TSP perception and, further, that the assumption concerning a spectral mechanism does not hold.
Previous research has shown that time separation pitch (TSP) is elicited by the monaural presentation of two ac or dc pulse trains, one train delayed with respect to the other, and is related to the reciprocal of time separation between leading edges of proximal pulses of the two trains. TSP has not been observed previously using uncorrelated noise pulses. On the assumption that TSP is mediated by an autocorrelational process, it was predicted that TSP would obtain using correlated-noise pulses that were produced by an "acoustic delay" system. Uncorrelated-noise pulses served as a control condition. Subjects matched the pitch of a pure tone to the pitches associated with the pulse trains. The results were as predicted. A TSPlike effect arising from continuous-noise samples was discussed and shown to be identical to TSP and, therefore, consonant with an autocorrelational theory. It was concluded that, at least for noise stimuli, temporally discrete waveforms are not necessary to elicit TSP perception; however, a high correlation between temporally adjacent waveforms is necessary to "trigger" TSP perception.
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