The privacy arms race. When your voice betrays you.

Like a fingerprint or an iris scan, every voice is unique. Security companies have embraced voice recognition—in which a segment of speech is recorded and the frequencies at which the sound is concentrated are analyzed—as a convenient new layer of authentication. Physical and behavioral traits of the speaker create a unique spectral signature, and demand for the technology is now skyrocketing. But experts worry that voiceprints could be used to identify speakers without their consent and compromise their anonymity, infringing on their privacy and freedom of speech. How and when voiceprints can be captured legally is still murky at best.