Sound is continuously passing through space, even if we can’t hear it. As sound waves pass through physical objects, a unique sound signature is generated.

Researchers at the Electronics Telecommunications Research Institute in South Korea built a system to map the bioacoustic signatures created as sound waves pass through humans. The machine uses a transducer that gently vibrates (and, as a result, generate sound waves even if they’re not detectable to human ears).

After the sound waves pass through a person’s skin, bones and soft tissues, a unique bioacoustic signature is created. Using these signatures, they can now discreetly and non-invasively determine a person’s identity.