Comparing the influence of several trajectories of head-tracked movements on the externalization of speech stimulus using non- individualized binaural synthesis

International audienceBinaural rendering uses headphones to (re)create an audio scene at the ears of the listener. In the real acoustic world, sound sources tend to be externalized (that is, perceived to be emanating from a source out in the world) rather than internalized (that is, perceived to be emanating from inside the head). Unfortunately, several studies report a collapse of externalization when listening with headphones to frontal or rear virtual sound sources using non-individualized head-related transfer functions (HRTFs). Previous experiments, conducted with both naive and expert listeners, revealed that this issue could be alleviated by large head-tracked movements (+/-90° continuous rotation of the head in the horizontal plane, with static evaluation immediately following the movement). The present study investigates whether enhanced externalization can also be observed when head movements are: 1) smaller (+/-50°), 2) in the vertical plane and 3) discontinuous (instantaneous shifts in head position). The three parameters under study ? amplitude, direction and continuity - were varied independently within a single experimental paradigm in order to: 1) determine whether optimized head-tracked movements can be defined, bringing highest externalization at the lowest cost in terms of efforts and time, 2) compare the contribution of binaural vs. monaural cues to externalization and 3) determine whether binaural/monaural cues have to vary continuously in order to enhance externalization