For vessels of less than 20 meters in length, what is the minimum frequency that must be maintained for signal audibility?

For vessels under 20 meters in length, maintaining signal audibility is crucial for safety, especially in distress situations. The minimum frequency of 180 Hz is established as it helps ensure that signals can be heard clearly without being dampened by ambient noise or distance. Frequencies lower than this may not be adequately transmitted over the needed distances, especially in challenging marine environments, where noise levels can vary significantly. Hence, opting for 180 Hz strikes a balance between audibility and the practical limitations of equipment typically used on smaller vessels.