Human echolocation
Human echolocation is the ability of humans to detect objects in their environment by sensing echoes from those objects. This ability is used by some blind people to navigate within their environment. They actively create sounds, such as by tapping their canes, lightly stomping their foot or by making clicking noises with their mouths. It can however also be fed in to the human nervous system as a new sensory experience. Human echolocation is similar in principle to active sonar and to the animal echolocation employed by some animals, including bats and dolphins.
By interpreting the sound waves reflected by nearby objects, a person trained to navigate by echolocation can accurately identify the location and sometimes size of nearby objects and not only use this information to steer around obstacles and travel from place to place, but also detect small movements relative to objects.
However, in the case of human clicking, since humans make sounds with much lower frequencies and slower rates, such human echolocation can only picture comparatively much larger objects than other echolocating animals.
Contents
Background
Human echolocation has been known and formally studied since at least the 1950s.[1] In earlier times, human echolocation was sometimes described as "facial vision".[2][3][4] The field of human and animal echolocation was surveyed in book form as early as 1959.[5] See also White, et al., (1970)[6]
Some blind people have described the phenomenon not as a learned method of navigation, but as an inherent and intuitive extra sense. For example, a blind person could walk past a line of trees and feel a "pressure" at their side as they passed each tree. The cause of this would be the echo of the sound of their footsteps; however, they may not consciously be aware of this mechanism, only that the phenomenon exists and can often be relied upon to detect obstacles.
Mechanics
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Echoes and other sounds can convey spatial information that is comparable in many respects to that conveyed by light. With echoes, a blind traveler can perceive very complex, detailed, and specific information from distances far beyond the reach of the longest cane or arm. Echoes make information available about the nature and arrangement of objects and environmental features such as overhangs, walls, doorways and recesses, poles, ascending curbs and steps, planter boxes, pedestrians, fire hydrants, parked or moving vehicles, trees and other foliage, and much more. Echoes can give detailed information about location (where objects are), dimension (how big they are and their general shape), and density (how solid they are). Location is generally broken down into distance from the observer and direction (left/right, front/back, high/low). Dimension refers to the object's height (tall or short) and breadth (wide or narrow).
By understanding the interrelationships of these qualities, much can be perceived about the nature of an object or multiple objects. For example, an object that is tall and narrow may be recognized quickly as a pole. An object that is tall and narrow near the bottom while broad near the top would be a tree. Something that is tall and very broad registers as a wall or building. Something that is broad and tall in the middle, while being shorter at either end may be identified as a parked car. An object that is low and broad may be a planter, retaining wall, or curb. And finally, something that starts out close and very low but recedes into the distance as it gets higher is a set of steps. Density refers to the solidity of the object (solid/sparse, hard/soft). Awareness of density adds richness and complexity to one's available information. For instance, an object that is low and solid may be recognized as a table, while something low and sparse sounds like a bush; but an object that is tall and broad and very sparse is probably a fence.
- "Echolocating Distance by Moving and Stationary Listeners", Lawrence D. Rosenblum, Michael S. Gordon and Luis Jarquin, in Ecological Psychology, 2000, Vol. 12, No. 3, pages 181-206.
- "Evaluation of an echo-Mobility training program for Young blind people", Daniel Kish, Master Thesis. 1982, University of Southern California.
Notable individuals who employ echolocation
James Holman
One of the earliest documented cases of echolocation was "the blind traveler" James Holman (1786–1857), who used the sound of a tapping cane to travel the world. Journalist William Jerdan wrote, "From Marco Polo to Mungo Park, no three of the most famous travelers, grouped together, would exceed the extent and variety of countries traversed by our blind countryman."[citation needed]
Daniel Kish
Echolocation has been further developed by Daniel Kish, who works with the blind, leading blind teenagers hiking and mountain-biking through the wilderness and teaching them how to navigate new locations safely, through the non-profit organization World Access for The Blind.[7] Kish had his eyes removed at the age of 13 months due to retinal cancer.[8] He has developed a click-emitting device and trains other blind people in the use of echolocation and in what he calls "echo-mobility".[9][10][11]
Kish has taught many blind people to use echolocation and expand their mobility.[11][10][12]
Ben Underwood
Diagnosed with retinal cancer at the age of two, American Ben Underwood had his eyes removed at the age of three.[13]
He discovered echolocation at the age of five. He was able to detect the location of objects by making frequent clicking noises with his tongue. This case was explained in 20/20:medical mysteries.[14] He used it to accomplish such feats as running, basketball, rollerblading, playing foosball, and skateboarding.[15][16]
Though at first resistant to using a cane for mobility, seeing it as a "handi-capped" device, and considering himself "not handicapped at all", Daniel Kish demonstrated to Underwood how he used his white cane combined with echolocation to further expand his mobility, though Underwood never adopted this method.[12]
Underwood died on January 19, 2009 at the age of 16, from the same cancer that took his vision.[17]
Tom De Witte
Tom De Witte was born in 1979 in Belgium with bilateral congenital glaucoma in both eyes. It had seemed that De Witte would become a successful flautist until he had to give up playing music in 2008. De Witte has been completely blind since 2009 due to additional problems with his eyes.
He was taught echolocation by Daniel Kish and was given the nickname "Batman from Belgium" by the press.
Dr. Lawrence Scadden
Dr. Scadden has written of his experiences with blindness[18]. He was not born blind, but lost his sight due to illness. As a child, he learned to use facial vision well enough to ride a bicycle in traffic. (His parents thought that he still had some sight remaining.) He later participated in experiments in facial vision (White, et al. 1970). About 1998, he visited the Auditory Neuroethology Laboratory at the University of Maryland and was interviewed about his experience with facial vision. The researchers in the lab study bat echolocation and were aware of the Wiederorientierung phenomenon described by Griffin (1959), where bats, despite continuing to emit echolocation calls, use dead reckoning in familiar acoustic space. Dr. Scadden indicated that he found echolocation effortful, and would not use it to navigate in familiar areas unless he were alert for obstacles, thus providing insight into the bat behavior, and incidentally challenging Nagel's thesis[19].
The Regional Alliance of Science, Engineering and Mathematics for Students with Disabilities (RASEM) and the Science Education for Students With Disabilities (SESD), a Special Interest Group of the National Science Teachers Association (NSTA) have created the Lawrence A. Scadden Outstanding Teacher Award of the Year for Students With Disabilities in his honor.
Lucas Murray
Lucas Murray, from Poole, Dorset, was born blind. He is believed to be one of the first British people to learn to visualise his surroundings using echolocation, and was taught by Daniel Kish.
Kevin Warwick
In this experimentation, the scientist, Kevin Warwick fed in ultrasonic pulses, as an extra sensory input, via a neural implant, through electrical stimulation. In tests he was able to accurately discern distance to objects and to detect small movements of those objects[20].
See also
References
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- How to see with sound Article by Daniel Kish in the New Scientist
- Harvard historical study and bibliography
- World Access for the Blind
- Blind Kid Uses Echo Location! - CBS video from YouTube.
- Seeing with Sound project
- BBC Science item "Sound of the Future"
- Ben Underwood: A Variety of Sourcesde:Menschliche Echoortung
