insidehistorySpecial units used a technique called “sound ranging” to try and determine where the enemy fire was coming from. To do so, technicians set up strings of microphones into the ground and then used a piece of photographic film to visually record noise intensity.The effect is similar to the way a seismometer records an earthquake. Using that data and the time between when a shot was fired and when it hit, they could then triangulate where enemy artillery was located and adjust their own artillery accordingly.At least one bit of that “sound ranging” film survived the WW1 — the film recording the last few minutes when the fighting finally fell silent at the River Moselle on the American Front.Like our content? Follow 👉🏼 @insidehistory(Via: @imperialwarmuseums)