In periods of reduced visibility or whenever a vessel operator needs to signal his or her intentions or position, a sound-producing device is essential. Navigation rules for meeting head-on, crossing, and overtaking situations are examples of when sound signals are required. The sound-producing device may be a whistle, horn, or bell that is audible for one-half mile.
- If boating on California state waters, the requirements for sound devices are:
- Vessels less than 39.4 feet (12 meters) in length, which includes PWC, are required to have some means to make an efficient sound signal but are not required to carry a whistle or a bell.
- Vessels that are 39.4 feet or more in length are required to carry on board a whistle and a bell.
- If boating on federally controlled waters, the requirements for sound producing devices are:
- Vessels less than 39.4 feet (12 meters), which includes PWC, must have some way of making an efficient sound signal. Examples are a handheld air horn, an athletic whistle, an installed horn, etc. A human voice is not acceptable.
- Vessels that are 39.4 feet (12 meters) or more in length must have a sound-producing device that can produce an efficient sound signal. The sound signal should be audible for one-half mile and should last for 4 to 6 seconds.