Which situation does not require a sound signal under international rules?

When considering situations where sound signals are required under international rules, it's important to understand the specific contexts in which they are mandated. The correct answer highlights that meeting or crossing international does not explicitly require a sound signal.

In maritime navigation, sound signals are primarily used as communication tools to ensure safety and coordination between vessels. The International Regulations for Preventing Collisions at Sea (COLREGs) outline specific requirements for sound signals that are generally focused on situations involving the proximity of other vessels, particularly in narrow channels or during overtaking maneuvers.

While operating in narrow channels and overtaking other vessels both necessitate specific sound signals to alert other vessels of your intentions and to prevent collisions, meeting or crossing international waters is generally not defined as a scenario that requires such action. This is largely because the rules governing sound signals pertain more directly to the interactions between vessels rather than their passage through open waters or international boundaries.

In restricted visibility, sound signals are also required to make vessels aware of each other’s presence despite reduced visual range. However, the situation of meeting or crossing into international waters does not involve direct interaction with another vessel that necessitates an immediate sound signal, allowing for navigation without that specific requirement.