Analysis of head rotation trajectories during a sound localization task

Dynamic changes of the Head-Related Transfer Function renderings as a function of head movement have been shown to be an important cue in sound localization. To investigate the cognitive process of dynamic sound localization, quantification of the characteristics of head movements is needed. In this study, trajectories of head rotation in a sound localization task were measured and analyzed. Listeners were asked to orient themselves towards the direction of active sound source via localization, being one of five loudspeakers located at 30 • intervals in the horizontal plane. A 1 s pink noise burst stimulus was emitted from different speakers in random order. The range of expected head rotations (EHR) for a given stimulus were, therefore, from 30 • to 120 •. Head orientation was measured with a motion capture system (yaw, pitch, and roll). Analysis examined angular velocity, overshoot, and reaction time (RT). Results show that angular velocity increased as EHR increased. No relationship between overshoot and EHR was observed. RT was almost constant (≈260 ms) regardless of EHR. This may suggest that dynamic sound localization studies could be difficult for a short stimulus with duration less than 260 ms.