Sound Mirrors Tacita Dean, 1999

The sound mirrors were conceived during the First World War when the concept of an air attack became the new danger to national security. They were built between 1928 and 1930 at Denge, near Dungeness as well as at two other sites along the Kent coast, as huge listening devices designed to pick up the sound of approaching planes, but were quickly proved unreliable when they could not discriminate between a passing boat or local traffic, and were then abandoned in favour of radar. However the sound they continue to hear is extraordinary, and the soundtrack to this film is entirely recorded within the 200 ft mirror.