Note: Probably filmed in the Pathe studio.
M/S's of large Vickers artillery piece being loaded. L/S of the gun being fired. With the aid of reconstruction the commentator gives a brief history of how sounds have been used down the years to signal trouble or danger, including someone dressed as Robin Hood, a town crier with a rattle and a native African banging drums.
Various shots of other people from their native countries demonstrating their instruments including a large gong, a warning fire bell from the great fire of London. More shots of other sounds including trombones dogs barking and diagrams of radios playing. Several diagrammatic shots showing how peoples ears pick up sounds. The commentator says that with the right sound frequency it is possible to create a silent bomber. L/S of aeroplane flying silently in the air with a question mark superimposed over the top.