Blind People Can Learn To Use Their Inner Bat
May 21, 2013

Echolocation Can Be Used By Blind People To Locate Objects

April Flowers for - Your Universe Online

Researchers have known for a long time that blind and visually impaired people rely on other senses. A new study led by the University of Southampton, however, now shows that they have the potential to use echolocation, similar to that of bats and dolphins, to determine the location of an object.

The researchers examined how hearing, particularly the hearing of echoes, could help blind people with spatial awareness and navigation. They also investigated the possible effects of hearing impairment and how echolocation could be optimized in order to help improve the independence and quality of life for people with visual impairments.

Scientists from the University of Southampton's Institute of Sound and Vibration Research (ISVR) collaborated with researchers from the University of Cyprus to conduct a series of experiments with sighted and blind human listeners. They used a “virtual auditory space” technique 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.

Sounds with different bandwidths and durations - from 10—400 milliseconds - as well as various audio manipulations were used to investigate which aspects of the sounds were important. ISVR´s anechoic chamber was used to create the virtual auditory space, which allowed researchers to remove positional clues unrelated to echoes, such as footsteps and the placement of an object. They were also able to manipulate the sounds in ways that wouldn't be possible otherwise, such as getting rid of the emission and presenting the echo only.

According to Dr. Daniel Rowan, Lecturer in Audiology: "We wanted to determine unambiguously whether blind people, and perhaps even sighted people, can use echoes from an object to determine roughly where the object is located. We also wanted to figure out what factors facilitate and restrict people's abilities to use echoes for this purpose in order to know how to enhance ability in the real world."

The study findings reveal that both sighted and blind people with good hearing showed the potential to use echoes to tell where objects are located, even if they were completely inexperienced with echolocation. Hearing high high-frequency sounds (above 2 kHz) is required for good performance, the researchers found, suggesting that common forms of hearing impairment will probably cause major problems.

"Some people are better at this than others, and being blind doesn't automatically confer good echolocation ability, though we don't yet know why. Nevertheless, ability probably gets even better with extensive experience and feedback,” adds Dr. Rowan.

"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. 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 study findings will help other researchers to develop training programs and assistive devices for the blind and the sighted in low-vision situations. The team intends to continue their research to investigate finding of objects in three-dimensional space and why some blind people seem to be able to outperform others, including sighted people.

Findings of the study are published in the journal Hearing Research.