The very topic of digital assistants and home smart devices sporting microphones and the potential for the outside world to listen in on recordings is not a comfortable one, to say the least.

It's no longer a simple case of who is listening but what is listening in the connected world of devices in the home and beyond.

A University of Chicago team has come up with a wearable microphone jammer in the form of a bracelet, and it can disable microphones in a person's surroundings.

The wearable jammer does its job against nearby and hidden microphones, thanks to researchers at the school's SAND Lab and the Human Computer Integration Lab.

The HCI lab does research focused on questions: what if interfaces would share part of our body? And, what new interface paradigm comes after wearable devices?

The SAND Lab (Systems, Algorithms, Networking and Data) at the university does research that spans such topics as security and modeling.

The bracelet works because it emits ultrasonic noise to disable the microphones.

Government Technology said the device randomly emits white noise within a range of 24 kHz to 26 kHz.

"We engineered a wearable microphone jammer that is capable of disabling microphones in its user's surroundings, including hidden microphones. Our device is based on a recent exploit that leverages the fact that when exposed to ultrasonic noise, commodity microphones will leak the noise into the audible range."

Two people talk in a video demo.

"So, tell me how it works."

"Sure. I can tell you how it works. But it's confidential."

This is a the sample conversation in a Feb 14 video on YouTube called "Wearable Microphone Jamming" from the HCI lab. The video shows the instances of how there is total silence at times when the bracelet is cutting out her description of how her secret project works. The transducers in the ring layout block out everything.

The bracelet jams microphones in speakers, smartwatches, and smartphones. The wearable even works if microphones are covered by paper or cloth,

Davd Nield in New Atlas further talked about how it works. The device is "crammed with 24 separate transducers that emit ultrasonic waves that interfere with microphones in all directions, even if they're hidden. By transmitting white noise randomly in the 24 to 26 kHz frequency range, mics in the immediate vicinity are only able to pick up static rather than spoken words."

The team prepared a paper for ACM CHI 2020, titled "Wearable Microphone Jamming" by Yuxin Chen, Huiying Li, Shan-Yuan Teng, Steven Nagels, Pedro Lopes, Ben Zhao and Haitao Zheng.

"Despite the initial excitement around voice-based smart devices," the authors said, " consumers are becoming increasingly nervous with the fact that these interactive devices are, by default, always listening, recording, and possibly saving sensitive personal information. Therefore, it is critical to build tools that protect users against the potential compromise or misuse of microphones in the age of voice-based smart devices."

It's only a prototype for now, said Nield.

There is reason to believe that we might hear about this at a later stage. Tyler Lee in Ubergizmo: "However, its creators believe that they could manufacture it for as little as $20, and that some of their investors have approached them with the idea to commercialize it."

In terms of commercializing it, one can see that it is not yet ready for the fashion runways; it has a lab prototype look of a bracelet in a kid's sci-fi movie but that could be addressed later on if they wish to address it.

Why their research matters: They made a wearable jammer that, according to their report, outperforms existing approaches with improved coverage and less blind spots.

In the past, ultrasonic transducers have been "heavily directional, thus requiring users to point the jammer precisely at the location where the microphones are." This had its limits. The team realized that "This is not only impractical, as it interferes with the users' primary task, but is also often impossible when microphones are hidden."

Another limitation with these devices, they said, was where multiple transducers enlarge jamming coverage but introduce blind spots.

They discussed their results. "We confirmed that an ultrasonic microphone jammer is superior to state-of-the-art and commercial stationary jammers by conducting a series of technical evaluations and a user study. These demonstrated that: (1) our wearable jammer outperformed static jammers in jamming coverage; (2) its jamming is effective even if the microphones are hidden and covered by various materials, such as cloths or paper sheets; and, (3) in a life-like situation our study participants felt that our wearable protected the privacy of their voice."

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More information: Yuxin Chen, Huiying Li, Shan-Yuan Teng, Steven Nagels, Zhijing Li, Pedro Lopes, Ben Y. Zhao, and Haitao Zheng. 2020. Wearable Microphone Jamming. In Proceedings of CHI Conference on Human Factors in Computing Systems 2020 (CHI'2020). https://doi.org/10.1145/3313831.3376304 (PDF)

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