Acoustic Location (Sound Mirror Devices)”>Acoustic Location (Sound Mirror Devices)
Acoustic location was originally applied to determining the presence and position of ships in fog.
Such devices (as well as sound mirros) were used from mid-WW1 to the early years of WW2 for the passive detection of aircraft by picking up the noise of the engines.
Of course this technologies were rendered obsolete before and during WW2 by the introduction of radar, which was far more effective. More of those strange devices can be found here , and focusing on the german ones is this site.
There is a strange beauty in such images depicting technological achievements of the past, and although they might seem funny nowadays, there’s a lesson there too I believe, concerning our notions of greatness and achievement (as a race) when put to the test of time.