It is essential for boaters to have the proper sound producing devices on board --- and to know how to use them. The common maneuvers below require short blasts of approximately one second each. (The duration of a prolonged blast is approximately four to six seconds.)

• One Short Blast:
  Tells other boats, "I intend to pass you on my port (left) side." In other words, when you're approaching another vessel --- either head-on or from behind --- you will maneuver to leave them on your left side as you pass. If the other vessel is in agreement, they should sound the same signal in response.
• Two Short Blasts:
  Tells other boats, "I intend to pass you on my starboard (right) side." In other words, when you're approaching another vessel --- either head-on or from behind --- you will maneuver to leave them on your right side as you pass. If the other vessel is in agreement, they should sound the same signal in response.
• Three Short Blasts:
  Tells other boaters, "I'm backing up" or "I'm using astern propulsion."

Boats less than 39.4 feet long need to have a whistle, a bell or an air horn on board. Boats between 39.4 feet and 65.6 feet long must carry a whistle that is audible for ½ nautical mile and a bell with a minimum mouth diameter of 7.87 inches.

Want more? Learn about additional sound signals here.

NOAA recently released ASSIST, a new system for submitting questions and reporting nautical chart errors to the Office of Coast Survey.  ASSIST allows users to tag submissions on satellite imagery, NOAA charts, or maps from any device including cell phones.

NOAA Makes it Easier to Submit a Comment or Report a Nautical Chart Error. [Web blog post]. (November 16, 2018).