Sound signals used on the waterways are like the turn light indicators used to signal intentions on the highways. Sound signals are also like an automobile’s horn used to let other drivers know you are near or to alert them of danger. All boaters should know proper sound signals, especially those boaters operating near commercial vessel traffic.
Sound signals are composed of short and prolonged blasts and must be audible for at least one-half mile:
- Short blast—about one second in duration
- Prolonged blast—4–6 seconds in duration
Sound signals can communicate a change in direction to other boaters.
- One short blast tells other boaters, “I intend to pass you on my port (left) side.”
- Two short blasts tell other boaters, “I intend to pass you on my starboard (right) side.”
- Three short blasts tell other boaters, “I am operating astern propulsion.” For some vessels, this tells other boaters, “I am backing up.”