Researchers reveal technology called SpiKey that can listen to the clicks a key makes in a lock and create a duplicate from the sounds. A team at the National University of Singapore developed the attack, which is the brainchild of Soundarya Ramesh, a first year Ph.D. student in computer science at the university. The attack leverages any basic recording technology and pairs it with signal processing software that can listen to the time difference between audible clicks of a key to determine its particular shape. That shape can then be transformed to a computer model that can be 3D-printed.
Source: https://threatpost.com/the-sounds-a-key-make-can-produce-3d-printed-replica/158457/