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. For example, sound signals are required when meeting head-on, crossing, or overtaking. Unnecessary sounding of whistles, horns, bells, or other sound-producing devices is prohibited.
- On Illinois state waters, all motorized vessels must have a mouth-, hand-, or power-operated whistle or other device capable of producing a blast that is two seconds or more in duration and audible for at least one-half mile.
- These requirements apply to vessels operating on federally controlled waters.
- 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.
- No vessel may be equipped with a siren, except law enforcement and emergency vessels.