Bolling Field Air Force Base, Washington DC, USA
(Unknown / Getty)
These sound amplifiers, at Bolling Field Air Force Base, were a response to the increasing impact of aerial warfare. The sound volume of an aircraft was sufficient to be detected at large distances, providing, in theory, sufficient time for a defensive response.
With the advent of radar, devices such as these β essentially an elaborate equivalent of a cupped hand β became obsolete.
βIn one day, recently, sixty-three German guns were located by this means, and destroyed by airplane bombs, although many of them had been so successfully camouflaged that probably they never would have been discovered by any other means.β
Popular Science, December 1918
