ジッタを含むパルス列のピッチ

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It is known that there are two kinds of cue in the pitch perception of complex tones, i. e. the temporal cue and spectral one. At a lower pitch the former is said to be dominant while at a higher pitch the latter is dominant. The influence of jitter on the pitch, therefore, may differ according to which cue dominants over the other. In this paper the effects of jitter on the pitch of pulse trains are investigated. Method of pitch-matching is adopted and the periodic pulse trains are used as the matching stimulus. The results obtained are as follows:(1) Accuracy of pitch-matching as a function of relative jitter shows different tendencies in accordance with whether the pulse-rate is in the lower pitch region or in the higher one. For stimuli with the pulse-rate below about 100 pps, even a small jitter deteriorates the accuracy of pitch perception. For higher pulse-rate stimuli with a relative jitter below 0. 1, however, the pitch of the stimulus of mono-polarity pattern brings about the same accuracy as for the periodic pulse train (Fig. 4). For an alternate-polarity pattern, a fairly accurate pitch-maching is obtained up to the condition of a larger amount of jitter(Fig. 5). (2) The accuracy in pitch-matching changes its tendency at a certain pulse-rate around 200〜250 pps for a mono-polarity pattern and at about 400 pps for an alternate-polarity pattern (Fig. 4 and Fig. 5). Since the fundamental frequency of an alternate-polarity pulse train is a half of the pulse-rate, the change of its tendency may occur at the fundamental frequency of about 200 Hz. (3) Judging from the power spectra of jittered pulse trains(Fig. 2 and Fig. 3), it may be concluded that the difference in the tendency comes from the difference in cues in pitch perception. In the higher frequency where the spectral peak is the cue in pitch perception, a fairly accurate pitch-matching is attained as long as the spectral peaks appear in the power spectrum. But in the lower frequency where the temporal information is a dominant cue, even a small jitter deteriorates the accuracy of pitch-matching regardless of the existence of spectral peaks. (4) For a random-polarity pattern whose power spectrum is nearly flat, the error in matching increases above the pulse-rate of about 200 pps(Fig. 8). (5) When the spectral information of jittered pulse trains is reduced by high-pass-filtering, the temporal information becomes a dominant cue in pitch perception up to a higher pulse-rate than in the unfiltered case(Fig. 9). (6) Accuracy of pitch-matching for a high-pass-filtered jittered pulse train becomes worse above 800 pps, and this value corresponds to the upper frequency limit of periodicity pitch perception(Fig. 10).
社団法人日本音響学会の論文
1973-06-01

ジッタを含むパルス列のピッチ

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