Behind the science: How echo-location works

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The Independent Online

To use echo-location efficiently it takes many hours of practice and a huge amount of determination but in the space of just half an hour Visibility’s Alex Campbell was able to teach me the basics of how it works.

The first thing you have to learn is how to produce a decent tongue click. Place your tongue on the roof of your mouth, just behind your front teeth and create a suction vacuum. When that vacuum breaks, it should emit a short sharp click.

Echo-location tends to come easiest to people whose sight is completely impaired.

It’s often hard for sighted people to concentrate on just using their ears. Partially-sighted people are also, understandably, taught to make the most of what vision they have left so echo-location can take extra work.

To help me forget about what I was seeing with my eyes, Alex gave me a blindfold which helped filter out any distractions.

Human ears are incredibly sophisticated. In fact we hear much better than we see. Unlike many animals, our eyes can’t take in infra-red or ultra-violet. But our ears can cope with around ten octaves. Place yourself in what you think is a completely silent room and you will in fact notice that we’re never in silence – if the room is quiet enough you should be able to hear your heart beating.

The first object we tried to find using the clicks was a flat, plastic tea tray which every so often Alex would place in front of my face. I would emit clicks every couple of seconds and my task was to grab the tray when I thought it was in front of me.

Amazingly it worked almost every time. It’s difficult for sighted people to describe sounds in detail – it’s something we’re simply not used to doing. Part of what an echo-location instructor teaches you is the language of trying to understand what you hear.

But all I can say is that every time the tray was placed in front of me the sound changed and somehow I knew it was there.

Next we tried a solid wall. I had to walk towards the wall and stop without bumping into it. Unlike the tray I struggled to find the wall. So instead we tried walking into the corner of a room and that was much easier. With the sounds waves bouncing off two surfaces, it was much easier to spot when the wall was close.

Next I was told to walk alongside a wall and find the opening in a door. Again this was relatively simple to do. We then walked from a large room into a small room where the sound change, unsurprisingly, was particularly pronounced.

After that it’s simply a case of trial and error and learning to master as many sounds as possible. That’s when the hard work really begins.