“Acoustic Radars” and Listening Trumpets

Before the advent of radar and hearing aids, hearing “trumpets” and the like were used to amplify distant sounds. Acoustic radars were invented during war time to locate ships in the fog and approaching airplanes. These listening devices not only enabled the listener to hear subtle, distant sounds, but also allowed for great accuracy in pinpointing the direction of the sound source due to the increased spacing and size of the giant “ears.” Some of these devices are very accurate, for example, the German RRH is able to detect the size of an approaching aircraft formation 8 miles away with the directional accuracy of 2 degrees.

Two-horn listening device at Bolling Field, USA in 1921

The experiments of Rev J M Bacon 1898 in London

Quad hearing trupet on wheels

Czech four-horn acoustic locator from the 1920s

Japanese acoustic radars from the 1930s

French hexagonal acoustic locator from the 1930s

German Ringtrichterrichtungshoerer (RRH) acoustic radar

Read more about each picture here: Acoustic Location and Sound Mirrors