Academic journal article Perception and Psychophysics

Localization of Moving Sound

Academic journal article Perception and Psychophysics

Localization of Moving Sound

Article excerpt

The final position of a moving sound source usually appears to be displaced in the direction of motion. We tested the hypothesis that this phenomenon, termed auditory representational momentum, is already emerging during, not merely after, the period of motion. For this purpose, we investigated the localization of a moving sound at different points in time. In a dark anechoic environment, an acoustic target moved along the frontal horizontal plane. In the initial, middle, or final phase of the motion trajectory, subjects received a tactile stimulus and determined the current position of the moving target at the moment of the stimulus by performing either relative-judgment or pointing tasks. Generally, in the initial phase of the auditory motion, the position was perceived to be displaced in the direction of motion, but this forward displacement disappeared in the further course of the motion. When the motion stimulus had ceased, however, its final position was again shifted in the direction of motion. The latter result suggests that representational momentum in spatial hearing is a phenomenon specific to the final point of motion. Mental extrapolation of past trajectory information is discussed as a potential source of this perceptual displacement.

The ability to localize objects in motion is a basic function of human perception. Up to now, the localization of moving objects has mostly been studied in the visual domain, whereas in the auditory domain, research has predominantly focused on questions of motion detection and discrimination (e.g., Lutfi & Wang, 1999; Strybel, Manligas, & Perrott, 1992; for a review, see Gilkey & Anderson, 1997) and of auditory motion aftereffects (e.g., Dong, Swindale, Zakarauskas, Hayward, & Cynader, 2000; Grantham, 1992; Neelon & Jenison, 2003). Only a few studies have investigated the localization of an acoustic object during its motion.

In an initial approach to this question, Perrott and Musicant (1977) presented a sound stimulus that rotated counterclockwise around the subject's head. Using a numerical scale, their subjects estimated the horizontal position of the sound source at the moment when the sound started (i.e., its onset position) and the moment when it ceased (i.e., its offset position). In the results, both the apparent onset and offset positions were mainly displaced in the direction of motion. The magnitude of onset displacement increased with the velocity of the sound source (between 90°/sec and 600°/sec), whereas the offset displacement did not follow a simple rule: In general, offset positions were less displaced than onset positions with shorter sound durations (50 and 100 msec), but more displaced with longer sound durations (150 and 300 msec).

In two recent studies, systematic mislocalizations of the onset and offset positions of moving sounds were found also with much lower target velocities than those used by Perrott and Musicant (1977). In both of these recent studies, subjects were presented with an acoustic target that moved from left to right or from right to left along the frontal horizontal plane, covering a distance of 36° or 40°, in a completely dark and anechoic environment. In Getzmann, Lewald, and Guski (2004), subjects pointed to the final position of targets moving at a constant velocity of 8°/sec or 16°/sec. In Getzmann (2005b), relative judgments were used to determine the perceived onset position of targets moving at 12°/sec. As hi Perrott and Musicant's study, both onset and offset positions were displaced in the direction of motion. These displacements have been related to analogous effects in the visual modality: the Fröhlich effect and representational momentum.

The Fröhlich effect (Fröhlich, 1923) is a systematic mislocalization of the onset position of a moving visual object, typically a displacement in the direction of motion (see, e.g., Müsseler & Aschersleben, 1998; Müsseler, Stork, & Kerzel, 2002). …

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