What is the function of sound signals at sea?

The function of sound signals at sea is primarily to communicate intentions or warnings to other vessels. This is crucial for ensuring safety in maritime navigation, as vessels need to convey their movements or alert others to potential dangers. For example, a ship may use specific sound signals to indicate actions such as overtaking, turning, or responding to another vessel's maneuvers. This communication is especially important in conditions of limited visibility, such as fog, where visual signals cannot be relied upon.

Other given options do not align with the primary functions of sound signals in maritime practice. Sound signals are not designed to measure distance, detect underwater currents, or serve as reminders for crew maintenance schedules, thus reinforcing that option B encapsulates the essential purpose of sound signals in the maritime context.