Mobile phones to help humans echolocate

Published: 06 Jan 2014

Ever wonder how bats and dolphins are able to use sound to navigate? The active use of sonar (SOund Navigation And Ranging) is called echolocation. The ultrasonic echolocation calls usually range between 20 to 200 kHz in frequency, humans are not able to echolocate as easily as bats and dolphins because human hearing tops around 20kHz max.

Thankfully, what nature cannot give us, technology can. Humans could soon be echolocating with the help of their mobile phones. At the Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland, researchers have discovered a mathematical equation that allows ordinary microphones to locate a room by picking up ultrasonic sounds that bounce off the room walls. Sonar technology sends out sounds that bounce off the object making it easier to identify the location of that object. Underwater mammals such as dolphins and whales send out a ‘clicking’ sound that is reflected back as an echo from the object source. This is how dolphins are able to travel for miles underwater and find food.

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However, to imitate echolocation in microphones is not that easy. Ambient sounds in a room can interfere with echolocation call sounds and they can bounce off the wall many times over making it harder to identify the source of the sound. Another reason why microphone echolocation is challenging, is because computers cannot filter sounds like bats or even humans can. We have the ability to distinguish the sound sources. It’s easier for humans to identify where the sound originated from because our two ears hear slightly different things.

Ivan Dokmanic is a doctoral researcher and the lead author of the PNAS paper; he has been dedicatedly working on the microphone echolocation technology. To enable echolocation in mobiles, he is experimenting by using a grid of distances, treating each echo as a sound and grouping the echoes correctly to deduce the shape of a room. He believes that when the sound sources are properly identified, the mobile devices will be able to pick up emitted sounds better than they are able to when sound waves are just bouncing off the room walls.

There are many more theories that are being tested to enable mobile devices to work on fundamentals of echolocation. Martin Vetterli, professor of communications systems at EPFL said that mobile phones can be used to locate people more accurately. However, the challenge with that is, that only certain frequencies can penetrate building walls and GPS is not always precise. Echolocation is a highly sophisticated tool that is capable of measuring the distance between the user and their proximity to the room-walls.

Vetterli believes that there is still a lot to do before sonar technology can be integrated on mobile devices but it’s a certainly something on the radar.


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