Acoustic Engineering and the First World War
WW1 Sound Mirrors were originally carved into the chalk cliff face as ‘listening ears’ intended to provide early warning of incoming enemy aeroplanes and airships about to attack coastal towns. These worked by focusing the sound from the plane’s engine so it could be heard before it was visible. Later, they were made out of concrete and specialist training was given to the operator using a stethoscope to interpret different sounds.
Nowadays, you can visit preserved sound mirrors up and down the British Coastline and a modern take on the sound mirror, according to Andrew Grantham, are sonic marshmallows!