This dual-mounted listening device served as an aircraft detection device before the invention of radar in 1935.
The Dutch military used the elephant-looking ears to detect approaching enemy aircraft by listening afar for engine sounds.
There were various iterations of the acoustic locators.
The Germans created a dual sight and sound system in 1917 that combined sound-ranging capabilities with binoculars to scope out aircraft.
The Imperial Japanese army used massive war tubas (resembling the musical tuba instrument) in World War I to detect the sound of incoming aircraft.
The Dutch also created acoustic horns in 1935 that were double the size of the personal sound locator. They offered passive detection of enemy aircraft by listening for incoming engine noise.
England built concrete acoustic mirrors around its coasts up until 1935.
Learn more about pre-radar objects here.