Addressing underwater radiated noise in construction of ships with ice-class

Ice-class ships are vessels specifically reinforced to navigate and operate in icy environments in accordance with "Ice-Class" regulations. While the highest ice-class ships possess the capability to break ice, it is important to distinguish them from icebreakers, which are specialised vessels designed exclusively for icebreaking purposes. In the design of vessels intended for operation in icy environments, it is essential toaccount for the impact of prevailing weather conditions according to ice-class regulations, which might have impact on underwater radiated noise (URN). Ice-class related design requirements may impact to underwater radiated noise in conflicting ways, and the effects of structural detail modifications are not necessarily predictable for practical cases. Therefore, a simulation-based approach is necessary for actual ship structures. When an ice-class strengthened ship structure is defined, specific simulation software enables calculations of the relevant properties, such as vibrations and hydrodynamics in a straightforward manner.

Some vibration reduction measures, including engine mounting and general machinery isolation, are typically applicable to ice-class ships without major constraints. Noise due to hydrodynamics is somewhat affected by the ice-class related requirements. Several propulsor concepts are effective in open-water conditions but may be less suitable for reducing underwater radiated noise in icy waters due to structural, operational, or acoustic limitations. For instance, CLT, tip-rake, high skew, and highly optimized low cavitation propellers cannot generally be used in ice-class ships. Some URN reduction measures, such as propeller optimization, have limited use in ice-class ships owing to structural and operational restrictions. This suggests that guidelines on URN reduction should be applied flexibly, depending on ship type and operating environment.