The bracelet of secrecy...

Researchers at the University of Chicago have delivered one in the ear to voice assistants (and, indeed, all covert listening devices) by designing a bracelet which, when activated, ‘jams’ all microphones in the area. It works by emitting white noise at 24kHz to 26kHz from transducers around the bracelet. Although this is above the frequencies within human hearing range, commodity microphones such as those in voice assistants will leak this ultrasound into the audible band, where it effectively masks speech. Previous jamming attempts have been highly directional and subject to blind spots; the bracelet’s ring of transducers overcomes the first issue, while the device being wearable improves the second by introducing motion through natural hand movements, which shifts any blind spots constantly. The bracelet is only a prototype, but could be manufactured quite cheaply, says the Chicago team of researchers.

▼▼ Activating the prototype bracelet jams microphones in the area using directional beams of ultrasound.