A team of researchers based in China has demonstrated a method to capture audio from headphones and similar analog devices from up to 30 meters away, including through walls, by using electromagnetic injection techniques. The approach, detailed in a paper presented at the USENIX Security 2026 conference, involves actively modulating signals through non-linear components in consumer electronics to induce side-channel leakage.

The technique, called InjectEave, was developed by Yan Long, an assistant professor at The Hong Kong University of Science and Technology, along with co-authors from HKUST and The Hong Kong Polytechnic University. In an email to The Register, Long stated that the method allows recovery of audio from headphones and landline handsets using electromagnetic signals transmitted in the 0-9 MHz range. The researchers tested the approach on 11 commercially available devices, including wired and wireless headphones from Sony, HP, and Philips, as well as smart fans, lamps, and VoIP landline units.

Testing showed successful audio recovery at distances of 1 to 6 meters under typical conditions, with extended range of up to 30 meters achieved using an RF amplifier. The researchers demonstrated scenarios where eavesdropping could occur through hotel room walls or using equipment concealed in luggage or office furniture. Devices tested included Sony ZX110AP wired headphones (2014), Apple Earbuds (2016), various wireless headphones from HP, Philips, and Xiaomi (2023–2025), Flyingvoice P23GW VoIP landline units (2023), and smart home devices such as OIDIRE ODI-MF10A fans and Xiaomi 1S lamps.

The attack exploits non-linear components such as amplifiers, analog-to-digital converters, and switching MOSFETs found in electronic systems. According to the paper, the method bypasses digital security measures like encryption and masking, as the leakage occurs through the analog signal path. The researchers noted that while hardware-based mitigations such as shielding and twisted-pair wiring could reduce vulnerability, they do not eliminate it entirely.

The findings highlight a potential risk in the widespread use of analog audio components in consumer devices, particularly in environments where signal interception might occur. The researchers emphasized that their work underscores the importance of hardware-level security considerations in device design.