In recent decades, a number of blind people have developed a bat-like method of determining their surroundings using tongue clicks. Following recent success in Berlin, the technique could become more widespread in Germany. Some even use "flash sonar" to ride bikes and go hiking in the mountains.

Two-and-a-half-year-old Juli merrily twirls around, holding a small white cane in her outstretched arm. Every so often, she makes a discreet clicking sound with her tongue. Doing so allows her to see with her ears, her parents say. She just needs more practice.

Four-and-a-half-year-old Frida already knows how it works. If someone holds out a pot lid at arm's length, she can locate it with a fair degree of precision. Using subtle tongue clicks, she scans the space in front of her face. "There it is!" she says. With a few more clicks, she can even determine the contours of the lid. The edge lies where the echo cuts off and she no longer hears a response.

The two girls are learning a method of echolocation known as "flash sonar," which resembles the type of active sonar used by bats. Both were born blind in Berlin, and both have parents who want to spare them from the typical life of a blind person.

"We spent a long time looking for a good replacement for vision," says Steffen Zimmermann, Juli's father. He believes that using flash sonar, blind people can get through life with a surprising degree of independence.

Mountain Biking Blind

This April two Americans came to Berlin to train Juli and Frida in flash sonar. They toured the city together, had them perform some initial exercises and explained to their parents what seeing with the ears is all about. One of the most important things is making the right sound: a snappy, dry click is best for locating things in the immediate vicinity.