To give early warning of raids, large concrete reflectors, or sound mirrors were built on the coast, to pick up the sound of airship engines with a microphone relaying the results to a nearby listener.
One sound mirror can be seen near Fulwell windmill in Sunderland.
Source: When war in the air came to the North East, Tony Henderson, The Journal, 3 February 2015.
There is an interesting article about Electronic Warfare in WW1 on the Landships website, in which Robert Robinson describes a somewhat obscure aspect of the Great War.
There is a common misconception that electronic warfare began with the Second World War but, even if it was not so labelled, it played a significant part in the First World War at both a strategic and a tactical level.
Fans of sound mirrors might be interested in the tale of how the Eiffel Tower was used to confuse Zeppelins.