Echolocation to "see" with sound

Daniel Kish is a blind psychologist who uses echolocation to "see." In New Scientist, Kish writes about his experience of "echo vision" and how he teaches others to do it:

Although our programme has many facets, we are best known for teaching FlashSonar. Its ability to give blind people a way to perceive their environment far beyond the reach of an arm or a cane is fast being recognised by people who work with blind people and in other disciplines. We are the first to develop a systematic, comprehensive way of teaching it.

We start by sensitising students to echoes, usually by having them detect and locate easy targets, such as large plastic panels or bowls. Once they can do this, we move on to learning to recognise more complex echoes by comparing them to familiar ones.

For example, when facing a hedge, a student might say, "It sounds solid?" I might reply, "As solid as the wall to your house?" "No, not that solid," she might say. "As sparse as the fence of your yard?" "No, more solid than that," she might answer. Now we have a range of relativity to work with. "Does it remind you of anything else near your house, maybe in the side yard?" "Bushes?" she might query. "But what seems different from those bushes?" "These are sort of flat like a fence." Ultimately, students verify what they hear by touching.

"Echo vision: The man who sees with sound"