'Seeing' with sound: There's an app for that

A team of researchers have developed an algorithm that can map a room based on acoustic echoes, essentially using echolocation like a bat. 

Photo Courtesy of École Polytechnique Fédérale de Lausanne
Scientists attempt to model the interior of Switzerland's Lausanne Cathedral based on how it echoes.

What is it like to be a bat? As Thomas Nagel persuasively argued in 1974, we will never know for sure what it feels like to navigate mainly by sonar, but a team of researchers could soon bring us the next best thing: an app for that.

In a study published in the current edition of the Proceedings of the National Academy of Sciences, scientists at Harvard University and the École Polytechnique Fédérale in Lausanne, Switzerland, describe how they have developed a software algorithm that builds a three-dimensional map of a room using just four microphones and a snap of the fingers.

The microphones pick up the echoes of the snap as they reverberate off the room's walls, and the algorithm measures the tiny lags between the sounds to measure the distance of the microphones from the source of the sound, as well as the distance from each of the walls. 

“Our software can build a 3D map of a simple, convex room with a precision of a few millimeters,” says Ivan Dokmanić, an École Polytechnique Fédérale doctoral student and the study's lead author, in a press release.

The researchers first tested their algorithm in an empty room with a movable wall. Pleased with the results, they moved on to something more ambitious: mapping an alcove in the Lausanne Cathedral, a floridly decorated Gothic church. The press release describes their efforts as yielding "good partial results."

In addition to helping us better identify with our chiropteran cousins, the researchers' algorithm promises a wide range of applications.

"Architects could use this to design rooms – for example concert halls or auditoriums – based upon the specific acoustics they would like to create,” says Mr. Dokmanić.

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