Localization of Turn Points in the Rhythmic Movement of Sound Image

The localization of start and turn points in rhythmic sound movement created through the modeling of binaural beats (BB) was investigated. The BB-modeled broadband stimuli consisted of stationary initial and final segments with a section of cyclic motion between them. Spatial effects were induced by changes in the interaural time difference (ITD). During the experiment, subjects assessed the position of the movement trajectory ends or the position of reference points using a graphic tablet. It was discovered that the perception of rhythmic movement of the sound image was significantly influenced by the integrative ability of the binaural auditory system. The results indicated that with instantaneous switching between stationary segments, the perceived positions of the trajectory ends (start point and turn point) matched the positions of the reference points. Conversely, the smooth movement between the same extreme values showed a displacement of the trajectory ends: the turn points were localized further from the reference points compared to the start points, at all trajectory positions in space. Localization of the trajectory end crucially depended on the time that the sound had stayed near the turning point. These patterns were expressed stronger in the central area of the acoustic space compared to the periphery.