Acoustic cues used by blind travelers

People with vision loss rely heavily on subtle environmental sound cues for safe and efficient travel (“Wayfinding”). Using our laboratory-developed instruments, the acoustic cues available to blind individuals, with and without hearing loss, during real-life pedestrian travel were recorded. Acoustic signals picked up by electret condenser microphones in the ear canals were fed to a wearable digital audio recorder. Head and body movements were monitored by accelerometers and gyroscopes mounted on the heads and torsos of subjects during typical travel situations such as walking along a corridor with an open doorway. A skilled wayfinder can detect the presence of an open doorway from the acoustic characteristics of the ambient sound field (the “acoustic signature”). The salient characteristics of the acoustic signature when passing an open door were found to be below 1500 Hz. These data confirm previous work regarding ambient room noise near a wall and an opening (Ashmead, 1999). Unlike previous work, the current study also measured the interaural characteristics of the acoustic signature. The results of this investigation will be used to develop the design requirements of a special-purpose hearing aid for people with both vision and hearing loss. (Funded by NIDRR and Smith-Kettlewell Eye Research Institute.)