Room mapping system delivers with a click of the fingers and 4 mics

AUTHOR: Inavate

Details of a room mapping system that uses algorithms and just four microphones to perceive the contours of a room have been published by EPFL's School of Computer and Communications Sciences. The algorithm can map a room from a finger click that is picked up by the randomly placed microphones. Developers believe the system could be used to help architects design rooms based on specific acoustics they want to create.

The development team, from the Audiovisual Communications Laboratory (LCAV) and led by Professor Martin Vetterli, published its findings in the Proceedings of the National Academy of Sciences (PNAS). 

“Our software can build a 3D map of a simple, convex room with a precision of a few millimeters,” says PhD student Ivan Dokmanic.

“Each microphone picks up the direct sound from the source, as well as the echoes arriving from various walls,” Dokmanic adds. “The algorithm then compares the signal from each microphone. The infinitesimal lags that appear in the signals are used to calculate not only the distance between the microphones, but also the distance from each microphone to the walls and the sound source.”

The researchers claim that each echo’s signal can be analysed using “Euclidean distance matrices,” and the system can tell whether the echo is rebounding for the first or second time, and determine the unique “signature” of each of the walls.

After initial tests in an empty room with a movable wall, the researchers moved to an alcove in the Lausanne Cathedral. They described the results and good and new tests using more microphones are likely to yield improved results.

“Architects could use this to design rooms – for example concert halls or auditoriums – based upon the specific acoustics they would like to create,” concludes Dokmanic.