Muster drill

A muster drill (sometimes called lifeboat drill) is a practice event which usually takes place on holiday cruise ships. The purpose of a muster drill is to show passengers what to do if there was a real emergency. The muster station leaders tell passengers about how to put on a life jacket, where the muster stations are and also explains other emergency information on the ship. The drill itself has to be completed before the ship leaves. Muster drills are not required on ferries, but safety announcements are made before the ferry departs. There was a rule where life jackets were needed to be worn at the drill but there has been some changes to the rules and most cruise liners do not require life jackets at the drill. 
General emergency alarm signal.
Before a muster drill starts, the captain announces over a loud speaker 30 minutes before, 15 minutes before and when the emergency alarm signal is about be sounded. The general emergency alarm is seven short blasts followed by one long blast of the ships horn/whistle and alarms that are built into the ship. The alarm inside the ship is usually a musical note which is sometimes joined with another to make a nicer sound. 
Signal: 7 short and 1 long: