Vessels LESS THAN ___ METERS may use anything to make an EFFECTIVE SOUND signal?

Vessels less than 12 meters in length are permitted to use any means to produce an effective sound signal, which can include devices like whistles, horns, or even clapping, as long as the signal is audible and meets the requirements for being effective. This regulation is in place to ensure that smaller vessels can signal their presence effectively in various maritime scenarios, despite potentially having limitations in size or the capacity for more sophisticated signaling equipment.

Other lengths are not applicable because larger vessels have stricter standards and requirements for sound signaling due to their increased risk and visibility concerns on the water. Therefore, the 12-meter mark is a clear choice, as vessels below this length are recognized for their flexibility in sound signaling methods while still adhering to maritime safety regulations.