On the Role of Temporal Information in the Pitch Perception of Complex Tones

Abstract

An experiment was carried out in which subjects adjusted the frequency of pure tone to match the pitch of a complex tone consisting of short pulses. The experimental results shown in Fig. 5 indicate that the frequency of a pure tone having the same pitch as the complex tone was slightly lower than the fundamental frequency of the complex tone in the frequency range between 200 Hz and 2000 Hz and slightly higher than the fundamental frequency at 100 Hz. The following hypothesis was proposed for the purpose of accounting for the results: "As a cue for pitch perception, temporal information provides a different value from what is given by spatial information, especially it provides a lower value than spatial information above 200 Hz". In order to verify the hypothesis, experiments on the pitch of complex tones were carried out. If the hypothesis is reasonable, the pitch of the complex tone consisting of short pulses without the fundamental component is expected to become lower because of rejection of spatial information. The experimental results shown in Fig. 7 support the hypothesis. In the second experiment, the pitch of complex tones consisting of two frequency components (f_1, f_2) was investigated. Three kinds of complex tones were used as follows: (1) f_1=400 Hz, f_2=800 Hz. (2) f_1=800 Hz, f_2=1200 Hz. (3) f_1=1200 Hz, f_2=2800 Hz. Since spatial information is expected to show a decrease in order of the above number, the pitch of two-component complexes should become lower in this order according to the hypothesis. The experimental results shown in Fig 8 also support the hypothesis. On the other hand, interspike interval histograms of primary auditory neurons published by Rose et al. (1967) were examined in detail. As a result, the interspike interval was found to be longer than a period of a tone stimulus waveform above 200〜300 Hz as shown in Fig. 10. This may be physiological evidence to show that the hypothesis is reasonable.