A team of experts from the Tokyo University of Telecommunications (Japan) and the University of Michigan (USA) have developed a method that allows digital assistants to send silent voice commands using a laser.
It all started when a researcher at Tokyo University of Telecommunications Takeshi Sugawara discovered strange behavior on his iPad. As it turned out, when the tablet microphone was exposed to a powerful laser, for some unknown reason, it perceived it as sound. By varying the intensity of a sinusoidal laser at 1000 vibrations per second over time, Sugawara created a high-frequency sound wave that the iPad's microphone picked up and transformed into an electrical signal.
After six months of research, Sugawara and a team of researchers at the University of Michigan turned the above photoacoustic effect into something more serious. Scientists have learned using a laser to "talk" with any device capable of receiving voice commands, including smartphones, smart speakers Amazon Echo, Google Home, devices supporting video calls Facebook Portal, etc. Researchers were able to send them at a distance of hundreds of meters light commands and with their help open garages, shop on the Internet, etc.
Experiments have found that if you aim a laser at a microphone and change its intensity at an exact frequency, the light will somehow cause the membrane of the microphone to vibrate at the same frequency. Over time, researchers have varied the intensity of the laser to match the frequency of the human voice. As a result, the microphone transformed the light waves into an electrical signal like sound waves and received silent voice commands. If you use an infrared laser, then the attack on the microphone of the devices will be not only inaudible, but also invisible.
