Sound Signals – Navigation

There are no lines on the water as on roadways. Operators have to understand both sound and light signals to communicate to others what they are about to do and understand what other operators are going to do.

Sound signals are frequently used by commercial-type vessels (i.e. cargo ships, ferries etc.) operating in busy waterways and/or ports.

Sound signals consist of short (1 second) and prolonged (4-6 seconds) blasts of a vessel’s horn or whistle.


The following are some basic examples of some common sound signals and their meanings:

One short blast“I am altering my course to starboard”
Two short blasts“I am altering my course to port”
Three short blasts“My engine is in reverse”
One prolonged blast“Warning – departing dock or entering/exiting blind spot”
Five short blasts“Danger – I do not understand your intentions”
REMEMBER: Five short blasts means “Danger – the vessel operator does not understand your intentions”