$20 Bracelet Jams Nearby Smart Speakers With Ultrasonic Static

University of Chicago researchers built a wearable cuff with 24 ultrasonic transducers that jams microphones within about three feet. The roughly $20 prototype exploits microphone nonlinearity to turn recorded speech into unintelligible static.

• 24 ultrasonic transducers in two rings of 12, about $20 in parts
• Effective jamming radius is roughly three feet
• 25 kHz signal is inaudible to humans but overloads commodity microphones
• Prototype has no commercial launch date; experts warn of an arms race