COLREGs-72 Sound Signals: Interactive Whistle Simulator, Audio Directory & Exam Trainer
Flawless acoustic identification of navigational signals is a mandatory statutory competency governed by Part D of the International Regulations for Preventing Collisions at Sea (COLREGs-72) and the STCW Convention. In restricted visibility conditions such as fog, heavy rain, or blinding snow, or when negotiating narrow fairways where vessels are obscured, the vessel's whistle, bell, and gong serve as vital audible lines of defense against catastrophic collisions.
The NavLib Sound Signals Simulator generates mathematically synthesized maritime acoustics via the Web Audio API without relying on pre-recorded external audio clips. The training module allows deck officers and cadets to master sound signal patterns under Rules 32, 34, 35, and 36, undertake randomized listening recognition tests with streak scoring, and practice physical blast timing on a bridge-style interactive whistle lever.
Frequently Asked Questions: COLREGs Sound Signals (FAQ)
What are the exact durations of a short blast and a prolonged blast?
- Short blast: a blast of about 1 second's duration.
- Prolonged blast: a blast of from 4 to 6 seconds' duration.
- Interval between blasts: about 1 second between successive blasts in a single sequence (except Rule 35(b) where the interval between two prolonged blasts is about 2 seconds).
How do fog signals differ between a power-driven vessel making way and one stopped?
- Power-driven vessel making way through the water (Rule 35(a)): sounds 1 prolonged blast at intervals of not more than 2 minutes.
- Power-driven vessel underway but stopped and making no way (Rule 35(b)): sounds 2 prolonged blasts in succession, separated by an interval of about 2 seconds, at intervals of not more than 2 minutes.
Which vessels sound "one prolonged blast followed by two short blasts" in restricted visibility?
What sound signals are required for vessels at anchor and aground in fog?
- At anchor (< 100 m): ring the bell rapidly in the forepart of the vessel for about 5 seconds at intervals of not more than 1 minute. Additionally, may sound 1 short, 1 prolonged, 1 short (● ▬ ●) on the whistle.
- At anchor (≥ 100 m): ring the bell forward (5 s), followed immediately by the rapid sounding of the gong aft (5 s).
- Aground (< 100 m): give 3 separate and distinct strokes on the bell + rapid bell ringing (5 s) + 3 separate and distinct strokes on the bell.
- Aground (≥ 100 m): bell signal forward followed by gong signal aft, preceded and followed by 3 distinct strokes on the bell.