Underwater Radiated Noise (URN)
MEPC 84 agreed in principle to extend the URN experience-building phase to end-2028; the Revised Guidelines remain voluntary.
Operational Explanation
Underwater radiated noise can affect marine life. Propellers, cavitation, hull and machinery contribute differently: consider the ship and its operating profile. The IMO Revised Guidelines remain voluntary. MEPC 84 agreed in principle to extend the experience-building phase (EBP) to the end of 2028; this does not create a new mandatory certificate.
Regulatory Reference
MEPC.1/Circ.906/Rev.1 — Revised URN Guidelines; MEPC.1/Circ.924 — 7 July 2026, design and retrofit; MEPC 84 — EBP.
Scope of Application
The guidance addresses design, modifications and operation; it does not address sonar, seismic activities or noise from warships and naval auxiliaries. Distinguish underwater noise from noise in onboard spaces regulated under SOLAS/MLC. Also check local provisions, routeing measures and port-programme conditions.
Procedure / How to Complete It
- Define operating conditions, sources and a method for a comparable baseline.
- Choose ship-specific targets and actions; verify results and review the plan.
- For design or retrofit, assess acoustic and energy performance together over the actual profile, not only at maximum speed.
Practical Example
A Company may adopt a voluntary URN management plan during EBP without calling it a certificate requirement.
What Typically Goes Wrong
Writing EBP until 2026, possible extension, or turning the extension into a mandatory obligation.
Common Mistakes Mistake Library
| Mistake | Consequence | How to Avoid It |
|---|---|---|
| Writing EBP until 2026, possible extension, or turning the extension into a mandatory obligation. | Non-compliant decision or treatment | Follow the approved arrangement and applicable sources |
What the PSCO Checks
Operational Tips
- Compare measurements with stated conditions, frequency bands and method.
- Lower fuel consumption alone does not demonstrate lower URN; assess retrofit benefits and trade-offs.
- Do not transfer savings percentages or dB reductions from an individual case directly to your ship.
Preparation checklist
- Voluntary status
- 2028 in principle
- Method declared
- No mandatory inference
FAQ
Related Topics
Last substantive revision of this page: 15 September 2026 · page fingerprint 2b0cc53b402d