Class 1 (Chief Engineer) Engineering Management 📅 Apr 2025

Exam Question

(a) Explain the concept of underwater radiated noise (URN) generated by ships. Identify its primary sources and discuss the effects of such noise on marine life. (8)

(b) Describe the international guidelines and best practices aimed at reducing underwater noise (e.g., IMO MEPC/Circ. 833). What operational, design, and maintenance measures can be implemented to minimize underwater noise? Also, explain the role of the Chief Engineer in ensuring compliance. (8)

Reference Answer

### (a) Underwater Radiated Noise (URN): Concept, Sources, and Effects
#### Concept of Underwater Radiated Noise (URN)
Underwater Radiated Noise (URN) is the unintentional acoustic energy emitted from a ship into the marine environment during its operation. This noise propagates efficiently through water over vast distances, contributing significantly to the overall ambient noise level of the oceans. It is often referred to as 'acoustic smog,' a pervasive form of pollution that degrades the marine habitat. The cumulative effect of global shipping has led to a consistent increase in low-frequency ocean noise, with levels in some major shipping lanes reportedly doubling each decade over the last 60 years. This noise interferes with the natural acoustic environment crucial for marine life.
#### Primary Sources of URN

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