Sight for the Blind The Growing Success of Seeing with Sound

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.

Bats navigate in a similar way. Using only echoes, they can flutter through thick foliage without incident, plucking insects off leaves with precision as they fly by. Though humans don't hear nearly as well, with a little effort they can make a surprising amount of progress with a similar technique.

One of the trainers is Juan Ruiz, a well-known flash-sonar expert. In several YouTube videos he can be seen riding a mountain bike through rough terrain.

Indeed, before making his way to Berlin, Ruiz made a stop in Italy, where he set a new Guinness World Record. A television studio in Milan was outfitted with an obstacle course featuring 10 columns, spread out over a 20-meter (66-foot) path. The cameras rolling, Ruiz mounted his bicycle and pedaled away, constantly clicking. The spellbound audience followed Ruiz's progress as he navigated his way forward guided by what seemed like a sleepwalker's instincts. One column after the next seemed to enter his field of vision. He curved to the left and to the right and, after 48.34 seconds, rolled over the finish line without a single mistake.

Measuring with Sound

Ruiz believes that anyone can learn to do what he does, including his young students in Berlin, Juli Schweizer and Frida Capellmann. "The girls are already doing quite well for their age," he says.

Juli, the youngest, lumbers fearlessly through her parents' apartment. For now, her discovery of the world of echoes is largely based on games. Her parents occasionally encourage her to use tongue clicks to detect a post or a ball, though it doesn't always work.

But Frida has aready become quite good at the method, her mother says. When she recently asked about an object they were passing in the city, Frida clicked a few times and answered: "Ah, a wall." When they were in a cemetery, she asked Frida to locate a rain barrel three meters away. Frida walked up to it, reached out her hand and patted the water. Another time Frida paused in front of a tree, clicking from the bottom up, tilting her head back as if she were taking a measurement. "How tall it is!" she exclaimed.

Even before the flash-sonar training, Frida had discovered the phenomenon of echoes. When she was crawling, she would slap her hands down on the floor and listen for reverberations. Later on, she made a habit of using a sharp, crow-like call to gauge her surroundings, whether in stairways, subway stations or stores. Since her training started, she prefers the tongue-clicking to the calls because it produces subtler echoes. Now other people's apartments have suddenly become exciting. "The first thing she does is check everything out," her mother says.

New to Germany

Ruiz, the flash-sonar trainer, was also a novice at one point. He learned the technique from Daniel Kish, a California native and pioneer in echolocation for the blind. As a young man, Kish climbed steep mountain trails alone, guided only by a walking stick and the echoes bouncing off his surroundings in response to his clicks. He learned to recognize shrubs, overhanging rocks, fences and sign posts (whose carved words he could then read with his fingers). His resourcefulness has already been documented by numerous television crews, and he goes by the nickname "Batman."

In recent years, Daniel Kish has taken on several assistants, most of whom are former students who now work as certified teachers for the blind. "So far, we have instructed 500 blind people and 5,000 teachers in 18 countries," Kish says.

Two years ago Kish spent a couple days working with then 7-year-old Lucas Murray in the southwestern British county of Dorset. Today, despite his blindness, Lucas enjoys playing basketball. The echoes tell him where the hoop is.

Other assignments have led Kish and his assistants to Mexico, France, Switzerland and Berlin. "Despite searching for a long time, we had never been able to find anyone teaching the method in Germany," says Steffen Zimmermann, Juli's father. Flash sonar is new to the country.

Before now, blind people were generally confined to the narrow circle tapped out by their white canes. But echoes expand the radius of this circle many times over. Loud clicking can yield signals from a building as far as 100 meters away. A parked car can be detected from five meters away. A large train station can be sounded out with a few good clicks in several directions. Someone well-practiced in flash sonar can locate the entrance to the tracks and the kiosks selling juice. The remote sensing technique is perfectly suited for unknown terrain.

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