In the early 20th century, sound locators were dreamed up to provide early warning of incoming enemy aircraft. After the invention of radar, the technology was cast aside. But now, innovators in Ukraine have revived the idea of acoustic detection with surprising success. In this episode, we explore the history of the technology and the reasons it has recently proved so effective at helping Ukraine foil Russian aerial attacks. Will other countries follow suit?

Host: Kenneth Cukier, The Economist's deputy executive editor. Contributors: Gascia Ouzounian of the University of Oxford; Tom Withington of RUSI; Ben Sutherland of The Economist; Kunal Patel, producer of “Babbage”.

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