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

The minimum frequency that must be maintained for signal audibility for vessels of less than 20 meters in length is indeed 180 Hz. This frequency is specified to ensure that distress signals are effectively heard in various conditions, including background noise that can be present near water.

Signals below this frequency may not be easily detectable by the human ear, especially in challenging environmental conditions. Therefore, adhering to the 180 Hz standard ensures greater reliability in communication, particularly in emergency situations where prompt and clear signaling is crucial for safety and prompt assistance.

This requirement aligns with international maritime safety standards designed to enhance the ability of nearby vessels or shoreside authorities to recognize and respond to distress signals.