Japanese scientists have recently invented a gun that can painlessly force people to stop talking. Kazutaka Kurihara of the National Institute of Advanced Industrial Science and Technology, and Koji Tsukada of Ochanomizu University, developed a handheld "SpeechJammer" gun that can force people to be silent from over 30 meters away.
The gun works by recording a target's speech, and then "shooting" it back at them with a 0.2-second delay. This causes the brain's cognitive processes to malfunction, and the victim stutters a bit, before going completely silent. Kurihara and Tsukada wrote a paper on the device, stating "in general, human speech is jammed by giving back to the speakers their own utterances at a delay of a few hundred milliseconds. This effect can disturb people without any physical discomfort, and disappears immediately by stopping speaking."
The builders of the device discovered that the gun works better on people who are reading at a pace, than with those who are engaged in "spontaneous speech." Also, if someone is making a long, meaningless sound, like "ahhhhhhhhhhhh," the gun won't work.
The inventors have suggested that the gun would be good for silencing chatty people in libraries, or to make people delivering boring speeches to be quiet, adding that "there are still many cases in which the negative aspects of speech become a barrier to the peaceful resolution of conflicts."