Learn Echolocation

http://www.wired.com/wiredscience/2009/06/echolocation/

Make Like a Dolphin: Learn Echolocation

• By Hadley Leggett
• June 30, 2009 |
• 4:53 pm |
• Categories: Brains and Behavior
• 
  

With just a few weeks of training, you can learn to “see” objects in the dark using echolocation the same way dolphins and bats do.

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Ordinary people with no special skills can use tongue clicks to visualize objects by listening to the way sound echoes off their surroundings, according to acoustic experts at the University of Alcalá de Henares in Spain.

“Two hours per day for a couple of weeks are enough to distinguish whether you have an object in front of you,” Juan Antonio Martinez said in a press release. “Within another couple weeks you can tell the difference between trees and pavement.”

To master the art of echolocation, all you have to do is learn to make special clicks with your tongue and palate, and then learn to recognize slight changes in the way the clicks sound depending on what objects are nearby. Martinez and his colleagues are developing a system to teach people how to use echolocation, a skill that could be particularly useful for the blind and for people who work under dark or smoky conditions, like firefighters — or cat burglars.

Most animals that use echolocation have organs that are specifically adapted to emit and receive sonar signals, but we humans have to rely on our rather clumsy mouth and ears. For instance, while dolphins use a special structure in their nose to generate up to 200 clicks per second, people can make only three or four clicks per second.

By studying the physical properties of the many different sounds the human mouth can produce, the Spanish researchers hope to maximize the power of human echolocation. In their latest study, published in a recent issue of the journal Acta Acustica united with Acustica, the group taught 10 of their students and colleagues to use basic echolocation. Then they compared different noises and clicks to determine the best type of sound for “seeing” your surroundings.

“The almost ideal sound is the ‘palate click,’” said Martinez in a press release, “a click made by placing the tip of the tongue on the palate, just behind the teeth, and moving it quickly backwards.” The palate click is better than other sounds, because it can be made in a uniform way, works at a lower intensity, and doesn’t get drowned out by ambient noise.

But there are a few drawbacks to human echolocation – like cotton mouth. “The quality of the sound tends to degrade after a few minutes of constant performance,” the researchers wrote, “due to progressive dryness of the mouth.” Luckily, clicks cause less dryness than other sounds, because you don’t have to exhale to make a click – which also means the sound doesn’t interfere with breathing.

Martinez isn’t the first to recognize the potential for echolocation in humans. At least two examples of blind people who have taught themselves to echolocate have made headlines in the past few years, and audiologist Peter Scheifele of the University of Cincinnati has studied these unusual cases.

“Acoustically, according to laws of physics, it’s certainly possible to make a pulse that will tell you something about objects in front of you, such as fences, garbage cans or basketballs,” Scheifele said. How much detail a person can “see” with echolocation depends not only on the speed of their clicks, he said, but also on the frequency. The higher the frequency, the more precise details you can see.

Scheifele has only worked with blind people who can echolocate, but he agrees that others could probably learn the skill. “My gut tells me if you can do it if you’re blind, you can do it if you can see,” he said. “Half the battle is really trying to get yourself in the groove of ‘I can do this if I try.’ We tend to be more visual animals than acoustic, and people don’t usually do it because there’s not a need for it.”