Submarines have used sonar for decades. Bats and dolphins have used it for millions of years. And thanks to a little math, humans could soon be echolocating with their mobile phones.
At the École Polytechnique Fédérale de Lausanne (EPFL), in Switzerland, experts in signal processing discovered a mathematical technique that allows ordinary microphones to "see" the shape of a room by picking up ultrasonic pulses as they bounce off the walls. The work was published in this week's edition of the journal Proceedings of the National Academy of Sciences (PNAS).
Microphone echolocation is harder than it sounds. Ambient noise in any room interferes with the sounds used to locate the walls, and the echoes sometimes bounce more than once. There is also the added challenge of figuring out which echoes are bouncing off which wall. [See also: "How Bats Stay on Target: Bio Sonar"]
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