Daniel Kish, a lifelong blind man, is one of the few people in the world capable of doing active personal echolocation. By making clicking sounds with his mouth, he is able to hear the echo coming back from everyday objects and distinguish them from each other. And since this ability gives Kish great benefits in his personal life, he has started an institution that teaches echolocation to other blind people. In the latest New Scientist, Mr Kish explains how he performs the trick, how others can achieve the same, and provides a little history on the topic.
A snippet from the article:
Humans probably used to rely on echolocation far more in the days before artificial lighting, when we had to find our way round in the dark. The readiness with which people learn sonar suggests to me it may be an inbuilt skill.
The first documented case of a blind person using sonar dates back to the mid-18th century. The French philosopher Denis Diderot wrote in 1749 of a blind friend so sensitive to his surroundings that he could distinguish an open street from a cul-de-sac. In the 19th century, the famous “Blind Traveller”, James Holman, was reported to sense his surroundings by tapping his stick or listening to hoof beats.
At the time, no one understood the basis of this skill. Some thought it relied on the skin on the face and called it “facial vision”. Only in the 1940s did a series of experiments prove this ability relies on hearing echoes.