Sound signals can be made by either a horn that is built into the boat or a handheld air horn. There are two types of basic signals, a short and a long blast. A short blast is about 1 second and is sometimes called a toot. A long blast lasts around 4 to 6 seconds.
Communicating intentions increases safety any time there is a chance of collision, but is even more critical in conditions of limited visibility (i.e., fog). As already mentioned, when two boats meet head on, the convention is for both to turn to starboard, but relying on another boat to act and/or to know your intended actions is dangerous.
Sound Signals
Note that there is a subtle difference between international/coastal standards and inland standards in the meaning of the action signals. The coastal convention is to signal your intention, wait for confirmation, then act. A signal is confirmed as received, understood, and agreed to by the receiving boat repeating the signal. Conversely, the inland standard is to signal your action as you are taking it, rather than to wait for confirmation.
