If you are afraid that digital home assistants such as Alexa or Roomba are listening and recording the conversations at home, now you will need to add light bulbs to the list of things to be afraid of. A team of Israeli security experts has demonstrated that it is possible to eavesdrop on conversations in a room from far away, using a standard light bulb, a telescope, and several scientific instruments.
Theoretically, it is possible to record sound waves in a room by watching a light bulb vibrate in response to sound waves. With a telescope and a sensitive electro-optical sensor, these vibrations can be monitored and recorded from afar and then converted into sound.
To test this theory, the security team attempted to record conversations inside an acoustically closed room 25 meters away, simply by watching a light bulb through the window glass. The vibrations of the filament inside the bulb were recorded and then converted into data with an analog-to-digital converter and analyzed with a pre-made algorithm.
According to the article describing the test, with this technique, sounds can be understood with remarkable clarity. Although the converted sound is extremely parasitic and muffled, the spoken words can be understood. So much so that it can even be understood and converted by Google’s Automatic Voice Recognition feature.
The researchers say that these vibrations, even at a few millidegrees, can be recorded and converted into sound. Of course, it is not possible to say that this technique is 100% successful. For example, it doesn’t work with fluorescent bulbs. For it to work, the bulb must be lit, close to the people talking, and there must be no obstructions in between.
You can watch this interesting espionage test in the video below:
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