Monday, September 1, 2014

Sound Mirror

This one is a little bit of acoustics and a little bit of calculus. The British military experimented with acoustic detection of approaching aircraft. These parabolic concrete plinths (Called Sound Mirrors) were built as the predecessor to radar during World War I. Many mirrors can be found on the coasts of England, and many more would have been built but for the invention of radar

The concept of operation is that a listener or microphone would be placed at the focus of the mirror. Due to the definition of a parabola, all sound coming from long distance (infinity) would reflect off of the mirror, and be directed toward the listener. In effect, this is a very simple means of amplifying and detecting plane engine noise from long distances. Similar equipment (albeit more compact and portable) is still used today as a means of spying on people or listening to the sounds of the NFL

This exhibit at Brooklyn's SIGNAL Gallery is a recreation of these mirrors with microphones embedded in their center. Two such mirrors are facing each other to create an interactive experience in the large gallery space. The sound picked up by the microphones is then played throughout the space via speaker.