Researchers analyze the sounds of someone typing on a keyboard for 10 minutes and piece together as much as 96 percent of what’s been typed. The technique works because the sound of someone striking the “A” key is different from the sound the “T” key makes. Researchers were able to guess 90 percent of the five-character passwords subjects generated within 20 tries. A noisy environment can conceal what keyboard users are typing, according to computer science professor Doug Tygar of the University of California, Berkeley.”]
Source: https://www.csoonline.com/article/2118943/hearing-is-seeing.html