Acoustic locators

Acoustic locators in Japan: 1930s. To the right, one of the figures is the Japanese emperor Horohito

Acoustic location was originally applied to determining the presence and position of ships in fog.

Acoustic location was used from mid-WW1 to the early years of WW2 for the passive detection of aircraft by picking up the noise of the engines. It was rendered obsolete before and during WW2 by the introduction of radar, which was far more effective.
Left: Jean Auscher's maritime acoustic locator.
This remarkable device was invented by Frenchman Jean Auscher as an acoustic navigation device in case of radar failure on small vessels. Shown at the 1960 Brussels Inventor's Fair, and, one suspects, nowhere else ever again.

more acoustic locators here, here and here
digged by issi noho