NTT Human Interface Labs., 1-2356 Take Yokosuka-shi, Kanagawa, 238-03 Japan
The thresholds of the switching period T[sub th]'s that produced the continuous or broken auditory apparent motion were measured, when the stimuli were successively presented by using three loudspeakers arranged in the horizontal plane. In the current experiment, the T[sub th]'s were investigated for amplitude-modulated broadband noise as a function of the modulation frequency f[sub m] (ranging between 4--64 Hz) and the modulation index m (ranging between 0.0--1.0). In agreement with the previous study that employed signals including bandpass noise, speech, etc. as stimuli [I. Kinoshita and S. Aoki, Tech. Rep. Hear. Acoust. Soc. Jpn. H93-2, 1--8 (1993)], the T[sub th]'s were diversified and generally larger than the one for an unmodulated (m=0.0) broadband noise; a monotonical increase in the T[sub th] was indicated with the modulation index (e.g., the T[sub th] ranged between 72--290 ms at a modulation frequency of 16 Hz), while the T[sub th] was reduced as the modulation frequency increased (e.g., the T[sub th] decreased from 360 to 135 ms at a modulation index of 1.0). These results indicate that the modulation causes the longer T[sub th]'s and will be discussed in terms of the temporal variation of stimuli.