Sound Localization in the Coexistence of Visually Induced Self-Motion and Vestibular Information

During movement, the position of a sound object relative to an observer continuously changes. Nevertheless, the sound source position can be localized. Thus, self-motion information can possibly be used to perceive stable sound space. We investigated the effect of self-motion perception induced by visual stimuli, ie,, vection and/or vestibular information, on sound localization. To enable perception of vection, random dots moving laterally on a wide screen were presented. For presentation of vestibular stimuli, a three-degree of freedom (3 DOF) motion platform which inclines right or left was employed. Sound stimuli were presented behind a screen when an observer perceived self-motion induced by visual stimuli and/or the platform. The observer's task was to point to the position of the sound image on the screen. Experimental results showed that the perceived sound position shifted to the direction opposite the perceived self-motion induced by visual information, regardless of the direction of vestibular information. Moreover, this tendency was observed only on the side of the median sagittal plane whose direction was the same as that of the movement of visual information. Thus, auditory spatial perception is possibly changed by self-motion due to the coexistence of visually induced self-motion and vestibular information