Just 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...