Daniel Kish has been completely blind ever since he was only 13-months-old, due to an aggressive form of cancer called retinoblastoma, which attacks the retina. Doctors removed both his eyes in order to save his life and replaced them with prosthetics. Kish has never seen a tree, a car, or another human being that he can recall, but after mastering echolocation, he's now able to perfectly navigate and even describe his surroundings in close detail. Continue reading for two videos and more information.
Every environment and surface has its own acoustic signature and he produces brief, sharp clicks with his tongue to identify them. The sound waves he creates travel at a speed of over 1,000 feet per second, bounce off every object that surrounds him, and returns to his ears at the same rate, though vastly decreased in volume, telling him exactly what everything is, and where it's located.
Daniel says there are two reasons echolocation, or FlashSonar, as he likes to call it, works so well for humans. The first is the positioning of our years on each side of the head. It's rare that we turn the wrong way when someone calls our name, because sound reaches the closer ear about a millisecond - a thousandth of a second - faster than the other, enough time for the auditory cortex to process the information. The second reason is our excellent hearing.