Common Sound Signals

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 0.80 km (one-half mile):

• Short blast—about one second in duration
• Prolonged blast—4-6 seconds in duration

Some common sound signals that you should be familiar with as a pleasure craft operator are as follows.

Changing Direction

• One short blast tells other boaters "I intend to pass you on my left (port) side."
• Two short blasts tell other boaters "I intend to pass you on my right (starboard) side."
• Three short blasts tell other boaters "I am backing up (operating astern propulsion)."

Restricted Visibility

• One prolonged blast at intervals of not more than two minutes is the signal used by power-driven vessels when making way.
• One prolonged blast plus two short blasts at intervals of not more than two minutes is the signal used by sailboats.

Warning

• One prolonged blast is a warning signal (for example, used when coming around a blind bend or leaving a dock).
• Five (or more) short, rapid blasts signal danger or signal that you do not understand or that you disagree with the other boater's intentions.