Sound walls were architectures created during the 1WW on the south and east cost of England to detect enemy aircraft. This was practically the system implemented before the to introduction of radar technology, which made it quickly obsolete.
Some of them have been demolished over time, nonetheless the ones that remain are stille huge monuments of memory.
From left to right: Abbot's Cliff, Joe Pettet-Smith; A sound mirror in use, National Trust; sound mirrors in Dungeness, Kant, Lawrence Mayes; Dungeness, Andrew Grantham.