App Lets You Map Rooms Like a Bat

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A new computer algorithm that could give humans the ability to map their environments with sound.
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Bats, whales and dolphins, among other animals, use echolocation -- emitting a sound and listening to the echo -- to create a mental map of their environment. They use this map to navigate and find food. Now, researchers have demonstrated a new computer algorithm that could soon give humans a similar ability to map their environments with sound.

The technology could be used to produce a more accurate sound experience in virtual spaces, fine-tune the acoustics of architectural designs and recreate room structure by using only audio files. Eventually, a person’s whereabouts could even be revealed via an echolocation app on her smartphone, down to the very room she occupies, since every room has a unique audio signature. Consider it a hyper-localized audio GPS.

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The system works by analyzing the echoes from a simple sound source, such as a person’s voice or finger snap. Those echoes are captured by a few microphones and then processed by the algorithm, which is able to reconstruct the 3-D geometry of complex room shapes.

“The algorithm relies on a certain acoustical model called image source model,” Ivan Dokmanic, of the Audiovisual Communications Laboratory at the Ecole Polytechnique Federale de Lausanne, told Discovery News. “It says that if you have an echo from a wall, you can model this echo -- this sound -- from a point source, which is like a mirror of the original source across a wall.”

Dokmanic said the algorithm he helped create is able to sort the echoes it receives and determine value. For example, due to a ricocheting effect, some echoes arrive at a microphone as a third or fourth echo, which are comparably diminished and less useful than “first-order echoes.”

“Combined with echo sorting, the algorithm can discard higher-order echoes and construct the walls from first-order echoes,” Dokmanic said.

These first order echoes help create a more authentic acoustic diagram -- one that’s just as important in the virtual world as it is the real world. Up until a couple years ago, Dokmanic says advances in virtual reality were mainly concentrated on the perception of visual space, not aural space. But he argues the sonic landscape is just as important because false representations of reverberations or echoes in the virtual world can easily confuse the brain.

To give an accurate impression of virtual space using sound, Dokmanic says it’s really important to provide the correct echoes. “If you’re starting your design of the space, then you could say ‘I know how I want my room to sound, so these are the acoustic properties I want it to have,’ ” he said. “The same thing applies to architectural acoustics.”

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