Skip to main content
Move the World.
audio jammer

Lead image design by Andrew Brumagen.

Oh, Alexa is definitely listening. Perched there, with unmatched patience and a microphone, waiting on the magic words.

Not willing to break it off, you wonder how to stop Alexa from listening when you don't want her to. An audio jammer developed by researchers at the University of Chicago just may be your most practical —and fabulous — option. Looking like a rolled-up, inside-out octopus arm, a bracelet studded with off-the-shelf transducers is more than a bold bangle; it's an ultrasonic audio jammer that can give you some Get Smart-style privacy.

Microphones are everywhere, explains Heather Zheng, a computer science professor at UChicago and the primary researcher behind the dramatically-dubbed "bracelets of silence." Mics are embedded in smartphones, digital assistants, laptops, tablets, watches, even doorbells. It's a whole invisible intelligence agency; the Internet of Things that may be bugging you at any given time. When her husband brought an Echo into their home, the couple told the New York Times, Zheng's distaste for the device led to their lab making the microphone jammer.

Audio jammer equipment is already available, Zheng says, including the kind of ultrasonic audio jammer category that the bracelet falls into. But they are expensive, directional, and stationary, making them impractical as personal privacy measures.

"They can only jam a specific direction," Zheng says. "You have to point to the microphone that you have detected to jam it."

An Audio Jammer Accessory

A directional ultrasonic audio jammer isn't only inconvenient in that it can only jam one mic at a time — and there's usually a lot of them hanging around — but it's also useless if you don't know where the microphone actually is. Zheng's lab wanted to create a device that could create a bubble of privacy for the user — and provide some agency when it comes to just who is listening.

audio jammer

Studded with ultrasonic frequency emitting transducers, this bracelet acts as an audio jammer, obscuring words with ultrasonic white noise to fool machine learning powered microphones. Photo courtesy of UChicago CS research groups SAND Lab and the Human Computer Integration Lab.

Built with the help of assistant computer science professor Pedro Lopes, the concept behind the bracelet of silence is simple. The octopus sucker-looking studs contain the transducers, which emit ultrasonic frequencies, acting as a microphone jammer. This takes advantage of a weird artifact in the microphone's design. Some microphones mechanically slow down ultrasonic noise — which the human ear cannot hear — into the audio range, making it audible to someone (or something) on the other end of the mic.

The bracelet only needs to block enough of the words to confuse an algorithm. The algorithm doesn’t have the benefit of human understanding and intuition when it comes to language.

The audio jammer doesn't block out everything you say perfectly, Zheng says. Since many of the microphones utilize machine learning algorithms to "hear" what you are saying, it only needs to block enough of the words to confuse an algorithm. The algorithm doesn't have the benefit of human understanding and intuition when it comes to language.

A human listener "could probably make out something if you have very good hearing," Zheng says. So the bracelet of silence isn't the best choice to keep your conversation private from whoever's in that flower delivery van that's been sitting outside your house for days.

But they can keep microphones from picking up every little word you say within a roughly three-foot bubble — which means other people's devices, like watches and phones, but hearing aids, too. That's why the device is easy to toggle between off and on, Zheng says. (And its battery lasts for just four hours of continuous jamming, so make sure your undercover mission budgets properly.)

Talk With Your Hands: Beating the Blind Spots

The key to the ultrasonic audio jammer's success is that it is wearable. This not only makes it more convenient, but it actually makes the microphone jammer more effective.

When the transducer's signals overlap in a specific way, their signals can interact so that they cancel each other out. Imagine ripples emanating all around you.

"Those multiple signals being generated, they are going to interfere with each other," says Mostafa Nouh, director of the Sound and Vibrations Lab at the University at Buffalo. "When they interfere with each other, they sometimes destructively interfere."

This can cause the signals to cancel each other out. Within that gap, the ultrasonic audio jammer has its frequency reduced, and it no longer works.

But the simple physical motion your body engages in provides enough disruption to the signals to help eliminate those blind spots. "When you make a tiny movement, the wave changes," Zheng says, "and they erase the blind spot."

In addition to blind spots and humans on the other end of the line, the jammer can also be thwarted by microphones that do not have the ultrasonic reduction artifact. Microphones will keep developing, Nouh says, "and therefore this thing that they are trying to exploit right now might not eventually be there."

Thick plastic can be an issue too. The material makes the ultrasonic audio jammer frequency degrade faster than an audible frequency does. But for the most part, it seems to work well against the devices most likely to be listening.

Creating a usable, multi-directional audio jammer was important for offering people a choice when it comes to technological eavesdropping, Zheng says.

"We wanted to achieve the balance of usability, effectiveness, the appropriate level of privacy protection, and user agency."

Up Next

Challengers
Meet the Startup Developing Human-Level Artificial Intelligence
Meet the Startup Developing Human-Level Artificial Intelligence
Challengers
Meet the Startup Developing Human-Level Artificial Intelligence
The story of Vicarious' mission to build the world's first human-level artificial intelligence and use it to help...
By Mike Riggs

The story of Vicarious' mission to build the world's first human-level artificial intelligence and use it to help humanity thrive.

Bionics
Building an Artificially Intelligent, Open-Source Prosthetic Leg
prosthetic leg
Bionics
Building an Artificially Intelligent, Open-Source Prosthetic Leg
We've come a long way since the first prosthetic leg, and "smart" limbs, equipped with computing capabilities and...

We've come a long way since the first prosthetic leg, and "smart" limbs, equipped with computing capabilities and artificial intelligence, are on the horizon. But for a team of engineers at the University of Michigan and Shirley Ryan AbilityLab, advances still aren't happening fast enough. To move things along, they are giving away the plans to an AI prosthetic leg — hoping researchers will piggyback off each other's work,...

Challengers
You Should Start Learning About Artificial Intelligence. Here's How.
You Should Start Learning About Artificial Intelligence. Here's How.
Challengers
You Should Start Learning About Artificial Intelligence. Here's How.
There are a lot of different levels of artificial intelligence being applied in a lot of different ways. Here's a...
By Mike Riggs

There are a lot of different levels of artificial intelligence being applied in a lot of different ways. Here's a primer for starting to wrap your head around it all.

Neuroscience
Dopamine and Serotonin May Do More Than We Thought
dopamine and serotonin
Neuroscience
Dopamine and Serotonin May Do More Than We Thought
Dopamine and serotonin are crucial brain chemicals. A new study that measured them simultaneously in active brains suggests they may do more than we think.

Dopamine and serotonin are crucial brain chemicals. A new study that measured them simultaneously in active brains suggests they may do more than we think.

Healthcare
Using Smartphone Cameras to Detect Diabetes
Detect Diabetes
Healthcare
Using Smartphone Cameras to Detect Diabetes
A new algorithm can detect diabetes using data collected by a smartphone’s camera, offering a way to address the problem of undiagnosed diabetes.

A new algorithm can detect diabetes using data collected by a smartphone’s camera, offering a way to address the problem of undiagnosed diabetes.

Dispatches
Brains Store Memories in a Temporary "Cache" (and We Can Read It)
What Part of the Brain Stores Memory?
Dispatches
Brains Store Memories in a Temporary "Cache" (and We Can Read It)
Like the day’s newspaper, the brain has a temporary way to keep track of events.
By Kelsey Tyssowski

Like the day’s newspaper, the brain has a temporary way to keep track of events.

Medicine
Could Growing Vaccines in Plants Save Lives?
Could Growing Vaccines in Plants Save Lives?
Watch Now
Medicine
Could Growing Vaccines in Plants Save Lives?
Vaccines for influenza, polio, smallpox, even Ebola have all be grown … in plants.
Watch Now

This flu season has been nasty in large part because the vaccine didn’t work as well as past versions. So scientists like Professor George Lomonossoff of the John Innes Centre are on the hunt for new ways to make better vaccines and think they might have found one -- by growing them in plants.

On The Fringe
Growing Human Organs in Pigs
Growing Human Organs in Pigs
Watch Now
On The Fringe
Growing Human Organs in Pigs
Twenty people die every day in the U.S. waiting for an organ transplant. There aren’t enough organs for the 100,000...
Watch Now

Twenty people die every day in the U.S. waiting for an organ transplant. There aren’t enough organs for the 100,000 people waiting for one. And there likely never will be… unless we can find a better way to source them. Enter: the pigs. A team of scientists has figured out how to grow human organs in pigs. It might make you feel weird. But it also might save countless lives.

Coded
Coded Trailer
Coded Trailer
Watch Now
Coded
Coded Trailer
Meet the programmers on the frontlines of the war over security and privacy.
Watch Now

There’s an invisible war being waged. Foreign governments are hacking major corporations. Major corporations are collecting massive amounts of consumer data. And the NSA is listening to everything. But a new generation of programmers armed with powerful technology is rising up and fighting back.