BOATsmart! USA Knowledge Base

Sound signals are used to attract the attention of other boaters and to aid with navigation. A sound signaling device can be a whistle, a bell, a horn or a gong. All of these devices must be capable of sounding a four second-long blast.

The bell or gong may be replaced by other sound equipment that has the same sound characteristics, such as a horn.

Additionally, you must know the difference between a ’short blast’ and a ‘prolonged blast’:

• A ‘short blast’ = a duration of one second.
• A ‘prolonged blast’ = a duration of four to six seconds.

Sound signals are also used to signal your distress to other boaters during an emergency. The ‘S.O.S.’ emergency sound signal is three prolonged whistle blasts—then three short blasts—then three prolonged blasts—then pause and repeat.