Audible apparent movement in depth

Auditory apparent movement was studied for source distance in depth varying in both relative and absolute distance. The stimuli consisted of 50‐ms broadband noise pulses, each presented at an A‐weighted sound‐pressure level of 70 dB and at a fixed 0‐deg azimuth. Aural targets (ATs) were separated into three distances ranging from 24 to 170 in. The time from onset (interstimulus onset interval or ISOI) of the stimuli varied from 6 to 150 ms. Results indicate that aural apparent movement is readily source displayed in depth (i.e., delta movement). As in studies with apparent movement in lateral dimensions, the relative timing of stimuli is crucial for the appearance of apparent movement [f(8,32)=8.16, p<0.001]. The relative distance between speakers was also found to be a significant factor for the appearance of apparent movement [f(16,64)=3.66, p<0.001]. These findings will be discussed further as they relate to previous research conducted on motion in the auditory system.