They get to know the sound coming out of a loudspeaker by “just” analyzing the flashes of the indicator LED.

Surely if you have speakers at home, you have noticed that in many cases these include a small alert LED that alerts us if the speaker is on or not. An LED that we know now can be a weapon that allows, with the appropriate means, to know the sound that comes out of the speakers.

While it might not sound like it, such a small light is capable of generating a large amount of information and this is what a team of Israeli researchers found when analyzing the flicker of the speaker’s LEDs. . This way, they were able to decipher the sound coming out of the speaker.

Much more than a warning LED

The team of Ben Nassi, Yaron Pirutin, Tomer Cohen Galor, Yuval Elovici and Boris Zadov were able to “hack” the speaker by analyzing the flicker of the speaker LEDs. And it is that although it is imperceptible to the human eye, the small LED emits a series of flashes which are the key to this discovery.

Based on these flashes, Ben Nassi and his colleagues learned what the speaker is playing. Consequently, these flashes are used to know a lot of information and do not remain just a simple alert system.

The basis of the experiment is that the speaker flickers are related to the increase and decrease of the electromagnet inside the speaker to create the vibrations responsible for the generation of sound. Therefore, the increase or decrease in vibration is related to the decrease or increase in the brightness intensity of the LED.

For the experiment, they used an electroscopic sensor capable of recording these blinks, which, as they say, are not perceptible to the human eye. With these changes in the LED recorded, it is a matter of analyzing and deciphering the flashes, relating these changes in light to an increase or decrease in the vibrations of the speaker. It suffices from there to decode the wave signal into audio.

According to the researchers, with this system, they were able to capture and decipher the sounds reproduced in speakers at distances of up to 35 meters. All they needed was to be able to clearly and clearly observe the brightness of the speaker LED and while the result is not perfect, it does offer enough clues as to the sound coming out of the speaker.

And since even a simple LED on the speaker can be a “sneak”, the question remains how to protect yourself. We have no choice but to use the same system as with webcams and cover the LED so that no device can analyze the flickers.

Although this may sound like something new, it is not something new to these researchers, since a year ago they managed to analyze the brightness of a light bulb in a room with a telescope at tens. meters in order, using the data collected, to decipher the conversation. . The method was called “lampphone” and it was dribbled in that music or any other sound produced vibrations on surrounding objects.

Via | Hackday
More information | Ben nassi

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