Researchers from the University of Southampton (UK) have been investigating how blind and visually impaired people can use echolocation, the navigational sonar used by bats and dolphins, to determine the location of objects. The study appears in the journal Hearing Research.
For the study, the researchers worked with sighted and blind human listeners using a “virtual auditory space” to investigate the effects of the distance and orientation of a reflective object on ability to identify the right-versus-left position of the object. They used sounds with different bandwidths and durations as well as various audio manipulations to investigate which aspects of the sounds were important.
The virtual auditory space, created in an anechoic chamber, allowed the researchers to remove positional clues unrelated to echoes, such as footsteps and the placement of an object, and to manipulate the sounds in ways that wouldn’t be otherwise possible.
According to lead researcher Daniel Rowan, the results showed that both blind andsighted people with good hearing, even if completely inexperienced with echolocation, could use echoes to discern the location of objects. The researchers also established that high-frequency sounds (above 2 kHz) are required for good location performance.
“We also found that our ability to use echoes to locate an object gets rapidly worse with increasing distance from the object, especially when the object is not directly facing us,” Rowan said. “While our experiments purposely removed any influence of head movement, doing so might help extend ability to farther distances. Furthermore, some echo-producing sounds are better for determining where an object is than others, and the best sounds for locating an object probably aren’t the same as for detecting the object or determining what, and how far away, the object is.”
The research team says the knowledge gained from this study will help develop training programs and assistive devices for blind people and sighted people in low-vision situations. The team is also extending their research to investigate the finding of objects in three-dimensional space and why some blind people seem to be able to outperform others.
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