Follow the Sound : Design of mobile spatial audio applications for pedestrian navigation

Abstract

Auditory displays are slower than graphical user interfaces. We believe spatial audio can change that. Human perception can localize the position of sound sources due to psychoacoustical cues. Spatial audio reproduces these cues to produce virtual sound source position by headphones. The spatial attribute of sound can be used to produce richer and more effective auditory displays. In this work, there is proposed a set of interaction design guidelines for the use of spatial audio displays in a mobile context. These guidelines are inferred from psychoacoustical theory, design theory and experience with prototype development. The horizontal front arc is presented as the optimum area for sound localization, and the use of head- or body-tracking is stated to be highly beneficial. Blind and visually impaired pedestrians may use auditory displays on mobile devices as navigation aids. Such aids have the potential to give visually impaired access to the environment and independence of movement. Custom made hardware is not always needed, as today’s smartphones offer a powerful platform for specialized applications. The Sound Guide prototype application was developed for the Apple iPhone and offered route guidance through the spatial position of audio icons. Real-time directional guidance was achieved through the use of GPS, compass sensor and gyroscope sensor. Spatial audio was accomplished through the use of prefiltered audio tracks that represented a 360° horizontal circle around the user. The source code of this prototype is made available to the community. Field tests of the prototype were done with three participants and one pilot tester that were visually impaired. One route was navigated with the help of the prototype. Interviews were done to get background information on navigation for visually impaired pedestrians. This was done to see how the prototype was received by visually impaired test users and what can be done to improve the concept in later development. Even though the prototype suffered from technical instabilities during the field tests, the general responses were positive. The blind participants saw potential in this technology and how it could be used in providing directional information. A range of improvements on the concept has been proposed.