This study investigated how auditory space was represented during linear self-motion. Participants were passively transported forward or backward at constant accelerations by a robotic wheelchair. A short noise burst (30 ms) was presented during self-motion via a loudspeaker aligned parallel with the traveling direction. In Experiment 1, the participants judged in which direction (incoming or outgoing) the noise burst was presented (i.e., two alternative forced choice task).
The auditory stimulus perceived to be aligned with the subjective coronal plane shifted in the traveling direction only during forward self-motion. The amount of shift increased with increasing acceleration. In Experiment 2, we examined the accuracy of sound localization during forward self-motion by employing a pointing method. Whereas the auditory stimulus located on the physical coronal plane was almost accurately perceived, those well located in the incoming space were perceived closer to the participants than the physical positions during forward self-motion. These results suggest that the representation of auditory space in the traveling direction was compressed during forward accelerations.