Sound and Motion

This thesis is concerned with the sense of self motion and orientation and how auditory cues from the surrounding soundscape contribute to these senses. It is known that vestibular, podokinetic and visual systems all contribute to our sense of self-motion in space and each provides the brain with different qualitative information in different reference frames. Sound exists all around us and human beings are highly accurate in localising the source of specific sounds. However, the contribution that hearing makes to human self-motion perception remains largely unexplored. The aim of this work was to explore how sound alters our perception of movement and how well a rotating soundscape can evoke audiokinetic vection; i.e. a sensation of rotation while stationary. The effects of sound on the vestibulo-ocular reflex (VOR) and the perception of movement are examined in chapter 2. Compared with silence and subject-fixed sound, room-fixed sound prolonged both the VOR and perception of movement during constant velocity rotation but in a speed-dependent and idiosyncratic way. Chapter 3 describes the development of a novel means of delivering an audiokinetic stimulus to stationary subjects to simulate what an individual would hear during actual rotation in a stationary soundscape. Chapters 4 and 5 are concerned with the illusion of rotation caused by a moving auditory environment. Chapter 4 uses the stimulus method developed to study audiokinetic vection – the illusion of motion generated by rotating the entire auditory “scene” around a subject. Healthy adult subjects were presented with a rotating auditory stimulus and reported feeling the sensation of self-motion at speeds similar to those reported with visual stimuli. Eye movements associated with audiokinetic vection are described in chapter 5. Subjects shifted gaze in the direction of perceived rotation, as is often observed during real movement. However, the slow eye movements that usually stabilise vision during motion were not observed. Chapter 6 concludes that sound does affect how human beings perceive self-motion but is given a lesser importance than other sensations