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.
Now, before anybody starts ripping the vibrating motors out of their phones, TechCrunch is quick to point out that this hack currently requires someone physically take apart a phone and rewire the motor to connect it to the phone’s audio system. But, as Roy explained, it may also be possible hack the power controller chip to collect the necessary voltage information to rebuild an audible waveform. And there’s also the possibility of hijacking the feedback motor in other devices like fitness monitors.
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