5 Predicting underwater noise levels
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Statutory Documents - IMO Publications and Documents - Circulars - Marine Environment Protection Committee - MEPC.1/Circular.833 – Guidelines for the Reduction Of Underwater Noise From Commercial Shipping to Address Adverse Impacts on Marine Life – (07 April 2014) - Annex – Guidelines for the Reduction Of Underwater Noise From Commercial Shipping to Address Adverse Impacts on Marine Life - 5 Predicting underwater noise levels

5 Predicting underwater noise levels

  5.1 Underwater noise computational models may be useful for both new and existing ships in understanding what reductions might be achievable for certain changes in design or operational behaviour. Such models may be used to analyse the noise sources on the ship, the noise transmission paths through the ship and estimate the total predicted noise levels. This analysis can help shipowners, shipbuilders and designers, to identify noise control measures that could be considered for the specific application, taking into account expected operational conditions. Such measures may include amongst others: vibration isolation mounts (i.e. resilient mounts) for machinery and other equipment, dynamic balancing, structural damping, acoustical absorption and insulation, hull appendages and propeller design for noise reduction.

  5.2 Types of computational models that may assist in reducing underwater noise include:

  • .1 Computational Fluid Dynamics (CFD) can be used to predict and visualize flow characteristics around the hull and appendages, generating the wake field in which the propeller operates;

  • .2 Propeller analysis methods such as lifting surface methods or CFD can be used for predicting cavitation;

  • .3 Statistical Energy Analysis (SEA) can be used to estimate high-frequency transmitted noise and vibration levels from machinery; and

  • .4 Finite Element Analysis (FEA) and Boundary Element Method (BEM) may contribute to estimate low-frequency noise and vibration levels from the structure of the ship excited by the fluctuating pressure of propeller and machinery excitation.

  5.3 The value of a modelling exercise is enhanced if its predictive capabilities are assessed in case studies under various operational conditions.

Parent topic: Annex – Guidelines for the Reduction Of Underwater Noise From Commercial Shipping to Address Adverse Impacts on Marine Life
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