Human echolocation is a technique involving echolocation used by some blind humans to navigate within their environment. It is similar in principle to active sonar and 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 identify the location and sometimes size of nearby objects, and use this information to steer around obstacles and travel from place to place.

The technique was developed and popularized by Daniel Kish. He is completely blind and taught himself to derive information about his surroundings by clicking his tongue and listening to the echo; using this technique, he is able to ride a bike and hike in unknown wilderness. He has developed a little click-emitting device and trains other blind people in the use of echolocation.

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 be consciously aware of this mechanism, only that the phenomenon exists and can often be relied upon to detect obstacles.

The most accomplished user of this technique is Ben Underwood. Diagnosed with retinal cancer at the age of two, he had his eyes removed at the age of three. He was taught about echolocation and now uses it to accomplish such feats as running, rollerblading, and skateboarding. He does not use a white cane but is able to detect not only the position, size and frequently composition of objects near him, but sometimes their shape.

See also

• Seeing with your ears

External links

• World Access for the Blind
• The Boy Who Sees with Sound (People.com)

Acoustics | Blindness | Perception

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