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. The navigation rules for meeting head-on, crossing, and overtaking situations are examples of when sound signals are required.
On Montana state waters, the requirements for sound-producing devices are:
- Vessels less than 16 feet long are not required to have a sound-producing device, but it is strongly recommended that these vessels carry a horn or whistle on board.
- Vessels 16 feet to 26 feet long are required to carry on board a whistle, horn, or other sound-producing device that is audible for at least one-half (1/2) mile.
- Vessels longer than 26 feet are required to carry on board a bell and a whistle or horn that is audible for at least one (1) mile.
On federally controlled waters, the requirements for sound-producing devices are:
- Vessels less than 39.4 feet (12 meters) in length, 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.