Silent Speech
From: NASA Tech Briefs - 12/01/2014

Sub-audible speech recognition based on electromyographic signals

An alternative way of communicating is based on the direct interpretation of
nervous system control signals sent to speech muscles by the brain. New ways
have been developed using ElectroMyographic Signals (EMGs) to perform common
interface functions such as joystick control, keyboard typing, and simple
speech command interfacing when reading or speaking to oneself with or
without actual lip or facial movements.

This work is led by Dr. Charles Jorgensen. With this technology EMG
electrodes are placed upon the throat to measure throat and tongue muscle
movements. These movements can then be translated into a limited vocabulary.
This capability allows for silent communication and speech augmentation in
extremely noisy environments such as the space station.

Read the entire article at:
http://www.techbriefs.com/dl/HOT100/SilentSpeech.pdf