The thing that has impressed me the most is this gadget they have. I dunno what you'd call it, but what it does is project sound from a distance. When I say a distance I mean a long way, few hundred meters or so. Typically they use it to project voice, and this thing penetrates through most matter including; glass!, gyp-rock walls! Don't confuse a megaphone with this. It's entirely different. I get the impression that, once the projected acoustics hit an object that is not penetrable, or it looses range - that's when you hear the sound. It hits the object, boom! - this energy explodes and translates into audible sound.

So, for example, if there's 2 people standing 500 meters apart - (we'll call these two people a & b respectively) - and there's a 3rd person in between them, person a can use this contraption, pointed at person b's head to transmit their voice to them, all with the person in the middle being none the wiser! I did a bit on sound & acoustics at Tafe many years ago, this thing has me baffled as to how it works.

Any thoughts?