He’s a microphone, but he doesn’t listen to: he looks. The Beijing Institute of Technology team has developed a system that captures sounds not thanks to acoustic waves, but via light. Their “visual microphone” is based on a simple idea: when a sound strikes a light surface, like a sheet, a piece of paper, a plastic cup, it causes micro-vibrations invisible to the naked eye. By projecting light on this surface and analyzing the intensity variations of the reflection, researchers can reconstruct the original sound!
A microphone watching instead of listening
So far, this kind of technology required advanced equipment: lasers, very high speed cameras … In short, it was expensive and not very transportable. Major innovation therefore comes from the method used: unique pixel imaging. It is based on a single light sensor associated with luminous patterns projected on the object. An algorithm then takes care of reconstructing the vibrations, then the sound.
« Our method simplifies and reduces the cost of using light to capture sounds, while allowing it to be used where a classic microphone would be useless, as through a window “Explains Professor Xu-Ri Yao, team director.
To validate their system, the researchers have placed objects 50 centimeters from a speaker diffusing a musical sequence (in this case, The letter to Élise) and series of figures in English and Chinese. Result: the sheet of paper made it possible to reconstruct an intelligible sound, especially in the low frequencies. The treble, they were a little more distorted, but partially corrected thanks to a signal processing filter.
One of the advantages of this technology is its computer lightness: the generated data flow remains low (4 MB/s), which authorizes continuous, locally or cloud records. Ultimately, the system could be miniaturized and integrated into everyday devices: phones, drones, even security cameras.
And this is where use cases are multiplying. One can imagine its use in the rescue (listen to the voices under the rubble), in the industry (diagnose a machine from a distance) or even in medicine (measure the heartless heart rate). But the question of privacy is never far away: this device can also capture a conversation without microphone, wire, nor physical presence. Just see, to hear.
Researchers assure not wanting to create a espionage tool, but a measurement tool in hostile environments. They are now working on improving sensitivity and lengthening the scope, for use in real conditions.
🟣 To not miss any news on the Geek newspaper, subscribe to Google News and on our WhatsApp. And if you love us, .
