Acoustic

An acoustic mirror is a large, concave structure typically made of concrete or metal that was used in the early 20th century to amplify and capture sound. Designed to reflect incoming sound waves towards a central point, acoustic mirrors were often used for detecting incoming enemy aircraft before the invention of radar. These structures were strategically placed along coastlines and in open spaces to provide early warning of potential attacks. Today, acoustic mirrors can still be found as historical landmarks, serving as a reminder of the innovative technology used in early defense systems.