“A forerunner of radar, acoustic mirrors were built on the south and northeast coasts of England between about 1916 and the 1930s. The ‘listening ears’ were intended to provide early warning of incoming enemy aeroplanes and airships about to attack coastal towns. With the development of faster aircraft the sound mirrors became less useful, as an aircraft would be within sight by the time it had been located, and radar finally rendered the mirrors obsolete.”
from Andrew Grantham’s catalogue of sound mirrors
http://www.andrewgrantham.co.uk/soundmirrors
I’ve heard of these before and recently read of them as an inspiration in the crafting of the Invisible Cinema, the early 1970s location of Anthology Film Archive’s screenings. They had seats built with a wrap-around hood to them, in order to better block out distractions and capture the sound of the film…