People can do amazing things

I forget where, but I think I saw someone doing this on TV, and it's really surprising how well it can work:

Like some bats and marine mammals, people can develop expert echolocation skills, in which they produce a clicking sound with their mouths and listen to the reflected sound waves to "see" their surroundings. A new study published in PLOS Computational Biology provides the first in-depth analysis of the mouth clicks used in human echolocation.

The research, performed by Lore Thaler of Durham University, U.K., Galen Reich and Michael Antoniou of Birmingham University, U.K., and colleagues, focuses on three blind adults who have been expertly trained in echolocation. Since the age of 15 or younger, all three have used echolocation in their daily lives. They use the technique for such activities as hiking, visiting unfamiliar cities, and riding bicycles.