Non-acoustic sensors detect speech without sound
10:30 09 April 2005
NewScientist.com news service
David HamblingJust think how eerie it would be, yet also how peaceful - people all around having conversations on their mobile phones, but without uttering a sound.
Thanks to some military research, this social nirvana just might come true. DARPA, the US Department of Defense's research agency, is working on a project known as Advanced Speech Encoding, aimed at replacing microphones with non-acoustic sensors that detect speech via the speaker's nerve and muscle activity, rather than sound itself.
One system, being developed for DARPA by Rick Brown of Worcester Polytechnic Institute in Massachusetts, relies on a sensor worn around the neck called a tuned electromagnetic resonator collar (TERC). Using sensing techniques developed for magnetic resonance imaging, the collar detects changes in capacitance caused by movement of the vocal cords, and is designed to allow speech to be heard above loud background noise.
DARPA is also pursuing an approach first developed at NASA's Ames lab, which involves placing electrodes called electromyographic sensors on the neck, to detect changes in impedance during speech. A neural network processes the data and identifies the pattern of words. The sensor can even detect subvocal or silent speech. The speech pattern is sent to a computerised voice generator that recreates the speaker's words.
DARPA envisages issuing the technology to soldiers on covert missions, crews in noisy vehicles or divers working underwater. But one day civilians might use a refined version to be heard over the din of a factory or engine room, or a loud bar or party. More importantly, perhaps, the technology would allow people to use phones in places such as train carriages, cinemas or libraries without disturbing others. Brown has produced a TERC prototype, and an electromyographic prototype is expected in 2008.
However, both systems come at a cost. Because the words are produced by a computer, the receiver of the call would hear the speaker talking with an artificial voice. But for some that may be a price worth paying for a little peace and quiet.