Where did that noise come from? It's a question people have been asking for millennia, but in the past century we started to build machines that would help us find out. Here are some of the most insane moments in the history of sound-location technology.
(via Google Patents/US224199)
A junior officer and NCO from an unidentified Feldartillerie regiment wearing a portable sound locating apparatus, c. 1917
A two-horn system at Bolling Field, USA, near the Army War College at Fort McNair (in the background), 1921
A Dutch device, built from 1934 for the Engineers Regiment and the Netherlands Army in the East Indies.