New Echolocation Technique Can Map a Room with the Snap of a Finger

Bats and dolphins are known to use echolocation to navigate, and there have been reports of some blind people being able to "see" the contours of a room based on how sound travels around. Now, researchers have developed a methodology that they believe will take the concept of echolocation to the next level.

By using only four microphones and a new computer algorithm, researcher are able to create an accurate three-dimensional map of a room with just noise from a snap of a finger. The team at Switzerland's Ecole Polytechnique Federale de Lausanne (EPFL) where the system was developed says the technology can lead to promising breakthroughs, including advances in architectural design and even forensic science.

"Architects could use this to design rooms - for example concert halls or auditoriums - based upon the specific acoustics they would like to create," Ivan Dokmanić, a PhD student working on the project said in a statement.

Dokmanić said the software can build a 3D map of a simple, convex room with a precision of a few millimeters.

"Each microphone picks up the direct sound from the source, as well as the echoes arriving from various walls," Dokmanić explains. "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 ability to "sort out" various echoes picked up by the microphones is itself a breakthrough. The system can differentiate among echoes and also tell whether the echoes are being reflected for the first time or not based on the unique "signature" of the individual walls.

The researchers offered the possibility of the technology being used in crime investigation, as an analysis of audio waves in a room could reveal information not readily apparent to the eyes. Another example of future application was to trace the origin of a phone call based on the analysis of sounds coming from a person walking around a room while speaking.

Another potential application is using the system to deduce location information in spaces where GPS signals are not available.

"There are already many applications, and we foresee many more. This is only the beginning!" Dokmanić said.

The research will be published in the journal Proceedings of the National Academy of Sciences (PNAS) later this week.