Military Wednesday – Acoustic Mirrors

An acoustic mirror is a passive device used to reflect and perhaps to focus (concentrate) sound waves.

Prior to World War II and the invention of radar, acoustic mirrors were built as early warning devices around the coasts of Great Britain, with the aim of detecting airborne invasions. Acoustic mirrors had a limited effectiveness, and the increasing speed of aircraft in the 1930s meant that they would already be too close to deal with by the time they had been detected. The development of radar put an end to further experimentation with the technique.