What is the directional property of a whistle in terms of decibel levels?

The correct answer highlights that a whistle used in maritime distress signaling should not produce a sound that is more than 15 dB below the prescribed level. This specific requirement ensures that the whistle remains effective in alerting nearby vessels or individuals to a distress situation. The prescribed level is established to ensure that the sound can be heard over background noise and at a sufficient distance, which is crucial for effective communication during emergencies at sea.

In a distress situation, the ability for a whistle to reach the prescribed sound level creates a significant difference in whether or not assistance can be summoned. If the sound produced by the whistle falls below this threshold, it may not be heard by those who could provide help, thus failing its critical function. Therefore, maintaining sound levels within this standard is essential for safety and compliance with maritime regulations.