«MIT researchers have developed a computer interface that can transcribe words that the user verbalizes internally but does not actually speak aloud.The system consists of a wearable device and an associated computing system. Electrodes in the device pick up neuromuscular signals in the jaw and face that are triggered by internal verbalizations — saying words “in your head” — but are undetectable to the human eye. The signals are fed to a machine-learning system that has been trained to correlate particular signals with particular words».

Source : Computer system transcribes words users “speak silently” | MIT News