Echolocation in Virtual Reality DARREN ROBINSON 1 , GAVIN KEARNEY 2 1 Department of Electronics, University of York, United Kingdom e-mail: info@darrenrobinson.audio 2 Department of Electronics, University of York, United Kingdom e-mail: gavin.kearney@york.ac.uk September 23 rd 2016 Abstract It has been shown that echolocation in humans, while not as advanced as other species, is a viable method of navigation. Where guide dogs and canes are vital tools for many visually impaired individuals, as of yet there are very few tools developed to aid them navigate a space using auditory cues alone. Although possible, the learning process for echolocation can be difficult and dangerous if not done with adequate guidance, support, and supervision. This paper investigates the possibility of developing an accurate training simulator in a virtual audio environment to provide a safe environment for the visually impaired to develop this skill. This is achieved by investigating a number of audio source localization and distance cues in relation to echolocation, translating these cues into a virtual environment, and examining the best method of re-creating this environment for the user. 1 Introduction The understanding that the visually impaired have been able to detect the presence of obstacles in their vicinity has been written about since 1749 when Diderot wrote of his experiences with a blind acquaintance [1]. He believed this ability was due to sensitivity to different air currents and atmospheric change. Since then it was discovered that this obstacle sense was the result of detecting reflected sound [2][3]. While there was some degree of disagreement on the nature of obstacle sense or facial vision, whether it was due to perceiving variations in the ambient sound field as you traverse through it [4], or the listening to specific reflected sounds [5], this paper specifically examines echolocation where environmental information is gathered by producing a sound stimulus and listening to the reflections generated rather than gathering environmental information based on ambient sound. This paper investigates the possibility of reproducing echolocation in a Virtual Audio Environment (VAE) for the purpose of developing a training simulator for the blind to learn echolocation in a safe environment. 2 Sound Localization In order to entertain the concept of reproducing echolocation in a virtual audio environment, one must first examine the effects of sound perception and localization, both about the head and in distance perception, specifically how echolocation functions in humans. Along with adequate understanding of sound localization cues one must also examine the methods of generating these cues accurately in a virtual environment and the mediums of auralization to relay this information to a user. Although the mechanisms of directional sound localization have been well understood for many years and are widely accepted, in contrast, the mechanisms of depth perception are less understood. Although a number of cues have been suggested in varying levels of importance, it is still debated as to the role many of these cues play and their importance in perceiving depth in audio. Where in an open environment there is a 6 dB reduction in sound intensity with every doubling of distance according to the inverse distance law, the use of intensity change in distance perception would be limited to the threshold in detecting a change in loudness[6]. Brungart and Scott found that shouted speech is perceived to originate further than whispered speech, and is again perceived to be more distant when the intensity is reduced[7], this may be due to frequency changes in the audio signal rather than specific intensity levels as lower frequencies are given more weighting when the intensity level increases [6]. The effect of frequency response on the perception of distance is backed up by Coleman’s experiments in 1968 where he discovered that for otherwise identical sound sources, those low pass filtered at 7.68 kHz were judged to be more distant than those filtered from 10.56