We Can Now Map Rooms Down to the Millimeter with a Finger Snap

Bats do it, dolphins do it — even short-tailed shrews do it: I’m talking about echolocation, of course, or the use of sound to find and identify objects in your vicinity. When submarines do it, we call it sonar. And when Morgan Freeman’s character Lucius Fox does something like it in The Dark Knight, we call it pretty darned cool. [youtube=http://www.youtube.com/watch?&v=obYNbQXCnx8] Now imagine using a technique like that to map a room at high resolution. And I don’t mean in general terms, approximating metrics like the reverberative acoustics of a sound space or studio, as many modern audio products do — but zeroing in on a room’s spatial particulars with millimeter accuracy. How? Using just four microphones and a finger snap. Researchers at the École Polytechnique Fédérale de Lausanne’s School of Computer and Communications Sciences, located in Switzerland, claim to have pulled it off (or nearly so) using an algorithm that lets you spec the dimensions of an area with a few microphones and the snap of your fingers. “Imagine that you are blindfolded inside an unknown room,” write the researchers in a paper published in science journal PNAS. “You snap your fingers and listen to the room’s response. Can you hear the shape of the room? Some people can do it naturally, but can we design computer algorithms that hear rooms?” Apparently we can, and not just one that can map a boring old empty room, but, say, something as sonically complex as the sound space of the Lausanne Cathedral. That’s impressive. But how? The new technique computes the shape of a room by applying an algorithm — the algorithm is what’s groundbreaking here — that calculates the geometric relationships between the arrival times of echoes produced by something as simple-seeming as a finger snap, allowing what amounts to a “blindfolded” estimation of a room’s geometry. “Our software can build a 3D map of a simple, convex room with a precision of a few millimeters,” said graduate student Ivan Dokmanić, the study’s researcher lead, speaking to EPFL Mediacom. And since the algorithm can … Continue reading We Can Now Map Rooms Down to the Millimeter with a Finger Snap