Echolocation offers a promising approach to improve the quality of life of people with blindness although little is known about the factors influencing object localisation using a 'searching' strategy. In this paper, we describe a series of experiments using sighted and blind human listeners and a 'virtual auditory space' technique to investigate the effects of the distance and orientation of a reflective object and the effect of stimulus bandwidth on ability to identify the right-versus-left position of the object, with bands of noise and durations from 10-400ms. We found that performance reduced with increasing object distance. This was more rapid for object orientations where mirror-like reflection paths do not exist to both ears (i.e. most possible orientations); performance with these orientations was indistinguishable from chance at 1.8m for even the best performing listeners in other conditions. Above-chance performance extended to larger distances when the echo was artificially presented in isolation, as might be achieved in practice by an assistive device. We also found that performance was primarily based on information above 2kHz. Further research should extend these investigations to include other factors that are relevant to real-life echolocation.
Bibliographical noteFunding Information:
Hannah Holmes and Leah Evans were supported by EPSRC Vacation Bursaries; David Edwards was supported by a RCUK studentship through a Basic Technology Programme grant to the Bio-Inspired Acoustical Systems project ( www.biasweb.org ). Thanks to Rebekah White for help with data collection (Experiment 4b). Box-plots were created using a (modified) template produced by Vertex42 ( www.vertex42.com/ExcelTemplates/box-whisker-plot.html ). We are extremely grateful to Associate Editor Brian Moore and two anonymous reviewers for their many helpful comments that have improved this manuscript substantially.