Operators of pleasure craft sometimes use sound signals.
Sound signals can be used to communicate manoeuvring plans, to alert others of your presence in restricted visibility and to draw attention in emergencies. Boaters need to know that various sound signals exist to attract attention and indicate a vessel’s intention.
Boats of less than 12 m. shall carry an effective sound-signaling device (such as a pealess whistle or a compressed gas or electric horn) or a sound-signaling appliance. Boats of 12 m. or more shall carry asound-signaling appliance such as a fitted whistle. Boats 20 m. or more must be provided with a bell in addition to a whistle.
Day or night, a boat in or near an area of restricted visibility should sound a combination of prolonged and short blasts with a whistle or othersound-signaling appliance. Here is what some common combinations of long and short blasts mean:
One short blast every two minutes: I am altering course to Starboard. Two short blasts every two minutes: I am altering course to Port.
Three short blasts every two minutes: My engines are going astern.
Five short blasts every two minutes: I am in doubt about your action taken to avoid collision!