Spies Can Eavesdrop on Phone Calls by...

 ... sensing vibrations with radar.

An off-the-shelf millimetre wave sensor can pick out the tiny vibrations made by a smartphone's speaker, enabling an AI model to transcribe the conversation, even at a distance in a noisy room.

Spies can eavesdrop on conversations by using radar to detect tiny vibrations in smartphones and employing artificial intelligence to accurately transcribe them. The trick even works in noisy rooms, as the radar homes in on the phone’s movement and is entirely unaffected by background hubbub.

Millimetre wave sensing is a form of radar that can measure movements of less than 1 mm by transmitting pulses of electromagnetic wave energy and detecting the reflected beams.

Suryoday Basak at Pennsylvania State University and his colleagues used a commercially available sensor operating between 77 and 81 gigahertz to pick up the tiny vibrations in a Samsung Galaxy S20 earpiece speaker playing audio clips. They then converted the signal to audio and passed it through an AI speech recognition model, which transcribed the speech. more$