On the Tempo Sensation of Burst Signals

Abstract

We can perceive the subjective tempo of a periodical burst signal train. With the Japanese language which involves a weak stress accent and relatively monotonical disposition of the syllables, the tempo sensation has a close relation with the speech quality. But it is not clear how the tempo sensation is affected by the physical characteristics of the signal, and which position of the signal wave corresponds to the tempo sensation. To answer these questions, we executed some phychological experiments on the tempo sensation using burst noise. The first experiment is concerned with subjective perception of the interrupted signal. As the pause time is increased, we can clearly perceive three sensation regions, i. e. continuous, ripply, and discrete sensation. These phenomena are due to the integral characteristics of the hearing mechanism. Using a psychological test procedure, the critical pause times corresponding to the boundary of the above sensation regions are examined. As the results, the critcal pause time change from the continuous to the ripply region is about 4 msec-6msec, and from the ripply to the discrete region is about 30 msec. Then it is examined how the tempo sesation affected by the difference of period, sound of timbre and duration of the burst signal. It is that only the effect of duration difference is highly significant. Holding the physical period of the signal constant, the subjective tempo is perceived faster as the duty cycle of the burst signal increase. This relaiton is shown in Fig. 8. The abscissa is the duty cycle and the ordinate is thepercent cycle of the period neccessary to match the same tempo sensation. Thirdly it is discussed, which position of the signal wave corresponds to the tempo sensation. As for the same form is repeated, we cannot obtain information in regard to the position on the same form. So, in this experiment, the burst signal constructed of rectangular and triangular waves the subject adjust the relative position to obtain uniform tempo sensation. As the result, it is formed that the corresponding position is neither the front nor the energy center of the signal, exists in an intermediate position between then