Naval traditions and culture encompass a wide range of activities, events, and objects, often unique to naval service. Some, like the ?crossing the line? (meaning, the equator) ceremony, are old and well-established, while others, such as gun shield art, related directly to Second World War experiences. Many reflect companionship, commemoration, recreation, or esprit de corps.
The bosun's (or boatswain's) call, also called a whistle, has traditionally been used to signal and command sailors.
By varying the force used to blow into the call, and by using fingers to control the amount of air escaping from the top of the spherical "buoy" (left), different notes can be sounded. Various combinations of notes can be used to issue different commands.
Bosun's Call
CWM 20070025-015