Here in central New York we have a great many retired farmsteads with silos all over the place. In my youth when I was as prone to play with explosives as guitars I would devise small noise makers to go off in these structures. The band and subsequent echo tended to be awe inspiring. Then I learned to to yodel. That too was a kick in the silos.More recently I was building a deck and chatting with a neighbor, nothing odd there until I realized he was over 100 feet away and we were conversing as if across a table. He was adjusting the reciever on his TV dish which was aimed at me. The shape of the disc concentrated his words and sent them my way. At the same time it concentrated and gathered my speach for him. I have wondered if 2 or 3 discs, placed correctly would be the accoustic grail we have searched for for years, balanced volume without feed back.
Don Meixner