Sound Mirrors

This is an interesting archeology site during the war time, sound mirrors.

“Sound mirrors” were built between the world wars (here pictured on the Kent Coast in the UK) as listening devices to detect incoming enemy airplanes. These reflectors fell into disuse with the advent of radar and remain as historic relics of an auditory past.
The Sound Mirror Project has proposed the revival of these devices for communication across the English Channel: “Visitors to the new mirrors will be able to climb up to a listening platform in front of the mirror in the manner of the orignal listeners at the historic mirrors. Rather than straining for the sound of distant aeroplane engines, people will be listening to the sounds of the sea, as well as for voices speaking to them from across the Channel.
A new advanced acoustic technology will allow transmitted sounds from the other mirror to be audible only at a particular focal point in front of the dish — focused at the small area around the listener’s head. The person standing at the focus point will hear a complete “holographic” binaural sound image which will appear to becoming from the air all around them.”

http://soundandsite.com/archives/category/architecture