Akustischer Parabolspiegel
In a whisper across the whole exhibition
Select one of the paraboloids and try to communicate with a visitor standing at the other one. Sound propagates in all directions but is reflected from solid objects. A sound mirror shaped as a paraboloid is able to send sound in a single direction if we position the sound source at its focus. If we place another paraboloid in the way of the resulting concentrated flow of sound, the sound will be reflected and will concentrate at its focus. So, if your friend whispers in the focus of one paraboloid, and you put your ear to the focus of the other paraboloid, you will clearly hear him. In other locations you can hardly hear anything at all. The principle of sound reflection and radio waves is used in the operation of satellite antennas, radio telescopes, seismic sensors or espionage technology.
