Making underwater radiated noise measurement practical for the world fleet

The International Maritime Organization (IMO) is working to make underwater radiated noise (URN) measurement practical and affordable for the global fleet. This proposal, co-sponsored by the International Chamber of Shipping (ICS), the International Pollution Interventions Association (IPTA), and the International Association of Classification Societies (IACS), aims to be included in the IMO's MEPC 85 guidelines.

Currently, dedicated sea trials for URN measurement can cost between USD 30,000 and 50,000 per ship, with an additional USD 40,000 to 250,000 accounting for lost revenue and diversion costs. For a fleet of around 100,000 ships, this could amount to USD 4 to 25 billion for one round of measurements. Global capacity for dedicated trials is only around 50 per year, highlighting the urgency for a more efficient solution.

A proposed network of autonomous measurement facilities at key maritime chokepoints, such as the Suez Canal, Panama Canal, Gibraltar, Malacca Strait, Taiwan Strait, and the English Channel, could measure ships during normal operations. This network would require a capital investment of approximately USD 0.8 to 1.8 million and an annual operational cost of USD 0.7 to 1.4 million. Including ship-specific data checking and reporting adds around USD 4,424 per ship.

The establishment of the network could be completed in about four years. While autonomous facilities will not cover every ship, such as short-sea vessels, onboard measurement, drone-deployed sensors, and predictive modeling remain viable options. The IMO's Revised Guidelines (MEPC.1/Circ.906/Rev.1) already favor direct measurement for establishing a ship's URN baseline, which is typically required by class society quiet ship notations.

Affordable URN baselines would make environmental incentive schemes financially beneficial and allow shipowners to verify the effectiveness of noise-reduction measures. The co-sponsors are urging the IMO to recognize the importance of affordable, accessible URN measurements and invite further proposals for feasible approaches. Any discussions under the IMO's URN Working Group should cover practical, affordable baselining options and timelines.