Speech stopping ray
If you have ever been annoyed by someone chatting in a meeting, or even in a concert, help might be on its way.
Kazutaka Kurihara and collegues have built a device which can stop someone speaking from across a room. It takes advantage of an effect you may have noticed when talking on a very bad phone line - if there is a delay of about a quarter of a second between you saying something and hearing yourself it is almost impossible to talk, because your brain is listening to your speech as you are talking, and using that to control that speech. If you hear yourself slightly delayed the whole system gets confused and you start to stutter, and find it very difficult to talk at all.
So they have mounted a very directional microphone next to a very directional loudspeaker with a laser pointer for aiming. When they point the device at someone speaking, it picks up the noise coming from that direction, and then plays the sound back at them with a delay adjusted for the time sound takes to travel that distance, causing the speaker to stutter and have great difficulty talking.
They are not intending to manufacture these devices but the technology is very simple so it is inevitable that someone will, which brings up interesting ethical issues as it would be possible to point it at a lecturer for a laugh or more sinisterly use the device at a political meeting to silence a competitor.