ANSWERS TO CORRESPONDENTS: Were concrete acoustic ears, built to capture the sound of aircraft, effective?
Before radar, nations relied on sound to detect incoming aircraft. Devices such as acoustic horns were developed during the First World War to amplify and locate the noise of aeroplane engines.
Before radar, nations relied on sound to detect incoming aircraft. Devices such as acoustic horns were developed during the First World War to amplify and locate the noise of aeroplane engines.
