The concept is quite simple. The device works by recording a person's voice as they speak via the directional mike. When the laser pointer is aimed at the speaker and the trigger pulled, their own voice is played back to them with a delay of 0.2 seconds.

Kurihara and Tsukada's tests have revealed some interesting phenomena. The device is most effective against people reading aloud compared to those engaged in conversational, spontaneous speech. It is not as effective toward nonsense sequences, such as "ahhh" or "arghh" (which unfortunately accompany many of those cell phone conversations that so irk us).

The researchers suggest that the gun could be used to silence noisy speakers in public places (mental image of black-clad librarians darting between the stacks, anybody?), or to facilitate proper group discussion and turn-taking. "There are still many cases in which the negative aspects of speech become a barrier to the peaceful resolution of conflicts," say Kurihara and Tsukada.

Let's get back to the science behind the device. Why is this sound delay so powerful in silencing someone who is speaking?

Have you ever spoken over the phone or video-chatted with someone and you can hear your voice echo on the . . . More