The solid white bracelet is equipped with 23 ultrasonic transmitters, and a microprocessor, a signal generator, and a battery are installed inside. You can activate the device using the switch on the housing. During the operation of the device, the transmitters emit ultrasound with a frequency of 24 to 26 kilohertz, which are distributed throughout the room.
When this sound hits a working microphone, it is converted to sound, overcoming the ultrasonic frequency filter, which is usually equipped with microphones from smartphones, smart speakers and other gadgets. Thus, a working bracelet creates a loud noise for microphones, which does not allow you to pick up and recognize speech.
It is not the first development of this type. Last January, Danish engineers Björn Karmann and Tore Knudsen created a special 3D printed nozzle for smart speakers, which is a kind of socket for the built-in microphone. Externally, a device called Alias looks like a frozen foam hat, and its essence is that the column does not exactly hear the owner in standby mode.