In times of less perceptibility or when a vessel operator needs to signal his intention or position a sound producing device is essential. If on state waters, Vessel 16 feet up to 26 feet long and engine power must have a whistle proficient of generating a blast of two seconds or more and audible for at least one half mile is obligatory and vessel 26 feet long or longer and under engine power must have a whistle proficient of making a blast of two seconds or more and audible for at least one mile is obligatory.If on federally controlled water, Vessel less than 65.6 feet long comprise PWCs must have a whistle or horn audible for at minimum one half mile is required and vessel 65.6 feet long or longer must have a whistle or horn and bell audible for at minimum one mile is required.