Researchers hack phone vibration motor to act as a microphone
“On the list of things that might be eavesdropping on your day-to-day conversations, the tiny motor that makes your phone buzz isn’t necessarily the first one that comes to mind. But that is exactly what happens with the VibraPhone — a proof-of-concept device created by two researchers from the University of Illinois at Urbana-Champaign to show that the motor in your smartphone or fitness tracker can be re-wired to act as a serviceable microphone.
The concept is fairly simple: the motor uses electric current to change a magnetic field that makes the vibrating mass move, like a clunky, low-frequency speaker. A microphone does the reverse by translating sound wave vibrations into electrical current with a magnetic diaphragm. In their research, Nirupam Roy and Romit Roy Choudhury of the University of Illinois at Urbana-Champaign show that the vibration motor can be similarly affected by sound wave vibrations in the air.”