A boat horn emits an audible signal. Its sound is higher pitched and softer than that of a ship's horn.
The boat horn offers a means of communication using short and long blasts. It is used particularly in low-visibility situations to communicate a vessel's situation or intentions.
Boat horns signals usually are audible up to a half mile. Both electric and compressed air models exist.
Boat dimensions will determine necessary signal intensity of the horn. Appendix III of the IRPC regulations describes requirements for marine sound signal devices.