Date : 17-6-2025
News : How Everyday Microphones May Be Spying on You
Your laptop mic might be leaking your conversations through walls via radio wave emissions that anyone can pick up with an FM receiver
The small size, low power usage, and affordability of micro-electromechanical systems (MEMS) microphones have made them a standard component in devices like laptops, smartphones, and smart speakers. In fact, it's likely there are several MEMS microphones within a few feet of you right now. These tiny microphones help us communicate easily with friends, family, and our digital assistants,but a recent discovery by researchers at the University of Florida and the University of Electro-Communications might change how you feel about them.
The researchers have uncovered a new side-channel attack that allows for remote eavesdropping on conversations picked up by MEMS microphones. The alarming part? This exploit doesn't require any changes to the hardware or software, any device equipped with such a microphone is vulnerable straight out of the box. Even more concerning, the microphone might be active without your knowledge, as popular apps like Spotify, YouTube, Amazon Music, and Google Drive can trigger it under certain conditions.
The attack, dubbed Sound of Interference, exploits the way MEMS microphones process sound using digital signal techniques. Specifically, these microphones rely on pulse-density modulation to convert audio into streams of digital pulses. During this process, they unintentionally emit weak electromagnetic (EM) signals. Despite their low power, these EM emissions can still carry acoustic information — and with the right tools, they can be intercepted and decoded using a nearby FM radio receiver.
In experiments conducted by the research team, the entire setup cost less than $100. Using only a basic copper antenna and an off-the-shelf FM receiver, they were able to capture intelligible speech—even through concrete walls up to 25 centimeters thick. In one striking example, the system picked up clear fragments of speech like “Glue the sheet to the dark blue background” from the surrounding noise. The researchers also achieved over 94% accuracy in recognizing spoken digits from a distance of up to two meters.
To make sense of the noisy EM data, the team employed sophisticated machine learning models along with commercial transcription tools from companies like OpenAI and Microsoft. Though these tools are designed for traditional audio input, they were still remarkably effective,producing transcriptions with error rates as low as 14%, even without being specifically trained to interpret electromagnetic signals.
Micro-electromechanical systems (MEMS) microphones have become nearly ubiquitous thanks to their small size, low power consumption, and affordability. They’re found in everything from smartphones and laptops to smart speakers. In fact, there’s a good chance a few are within arm’s reach of you right now. These tiny devices help us stay connected and interact seamlessly with our digital environments but a recent discovery may cause you to think twice about their presence.
Researchers at the University of Florida and the University of Electro-Communications have uncovered a new side-channel attack that makes it possible to remotely eavesdrop on conversations captured by MEMS microphones. Alarmingly, this attack doesn’t require any modifications to hardware or software. Any device equipped with a MEMS microphone right out of the box is potentially vulnerable. Worse still, the microphone doesn’t even need to be explicitly activated by the user. Popular apps like Spotify, YouTube, Amazon Music, and Google Drive can activate the microphone under certain conditions without obvious user consent.
The attack, named Sound of Interference, exploits the way MEMS microphones perform digital signal processing. These microphones use a method called pulse-density modulation to convert sound waves into streams of digital pulses. During this conversion, they emit faint electromagnetic (EM) signals. Though weak, these signals carry trace amounts of acoustic data, which can be intercepted and decoded by a nearby FM radio receiver.
In practical tests, the research team used a basic setup costing less than $100. a simple copper antenna and a commercial FM radio receiver. With this setup, they managed to capture intelligible speech through concrete walls up to 25 centimeters thick. In one case, phrases like “Glue the sheet to the dark blue background” could be heard clearly through the static. The system also demonstrated over 94% accuracy when recognizing spoken digits within a two-meter range.
To extract useful data from the noisy EM signals, the team applied advanced machine learning algorithms and transcription services from companies like OpenAI and Microsoft. Even though these tools were originally designed for conventional audio input, they still achieved surprisingly low error rates just 14% in some cases despite no prior training on electromagnetic data.
While the findings are concerning, they don’t mean we need to abandon MEMS microphones entirely. The researchers outlined several defenses that could be adopted by manufacturers. For example, moving the microphones closer to the main circuit board could reduce the length of conductive traces, which otherwise act as antennas. Modifying audio processing protocols might also make it harder for attackers to extract meaningful signals. Another proposed solution involves hardware-level protections such as clock randomization, which would scramble the timing of the emissions and make decoding far more difficult.
For now, it’s unclear whether these countermeasures will be implemented in future devices. Until then, it’s worth remembering that the same microphones enabling convenient voice features may also be silently transmitting sensitive conversations , accessible to anyone with a basic radio and a bit of technical skill
Summary :
Micro-electromechanical systems (MEMS) microphones have quietly become a core part of modern technology. Found in smartphones, laptops, smart speakers, and other devices, these tiny components are valued for their compact size, low power use, and affordability. Chances are, there are several MEMS microphones within a few feet of you right now. While they enable seamless communication and voice control, recent research has revealed a hidden vulnerability that could turn them into unexpected eavesdropping tools.
Researchers at the University of Florida and the University of Electro-Communications have discovered a side-channel attack that targets MEMS microphones—no hardware tampering or software manipulation required. Dubbed "Sound of Interference," the exploit allows attackers to remotely listen in on conversations by capturing faint electromagnetic (EM) signals unintentionally emitted by these microphones during audio processing.
How the Attack Works
MEMS microphones convert sound into digital data using a technique known as pulse-density modulation. During this process, they generate weak but detectable EM emissions. These emissions carry traces of the captured sound and can be picked up using simple radio equipment. With nothing more than a copper antenna and a standard FM radio receiver—costing less than $100—researchers successfully captured intelligible speech through walls up to 25 cm thick.
In one demonstration, clear phrases like “Glue the sheet to the dark blue background” emerged from the radio static. Within a two-meter range, the system achieved over 94% accuracy in identifying spoken digits—making the threat not just theoretical but highly practical.
Decoding the Data
To interpret the noisy EM signals, the research team employed advanced machine learning models and commercial transcription services from companies such as OpenAI and Microsoft. Surprisingly, these tools—though designed for standard audio inputs—were still able to transcribe the intercepted speech with error rates as low as 14%, even without being specifically trained on electromagnetic data.
Why You Should Be Concerned
What makes this attack especially concerning is that the microphone doesn't even need to be intentionally activated by the user. Apps like Spotify, YouTube, Amazon Music, and Google Drive can trigger microphone access under certain conditions—leaving users unaware that their conversations may be at risk.
Can This Be Prevented?
Fortunately, the researchers have proposed several countermeasures manufacturers could implement to prevent this type of surveillance:
Relocate microphones closer to the device's main circuit board to shorten conductive traces that act like EM antennas.
Adjust audio processing protocols to introduce noise or encryption that confuses EM signal extraction.
Use hardware-level protections like clock randomization to disrupt the timing coherence of EM emissions.
Final Thoughts
At present, it’s unclear whether hardware makers will adopt these defenses. Until then, users should be aware that the same microphones that power our smart devices may also be silently leaking our conversations to anyone with a simple radio and some technical know-how. The convenience of MEMS microphones has come with a hidden cost—and now, it's time we started paying attention.
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