Modelling the outdoor noise propagation for different ship types

Airborne noise emissions from ships can be a significant source of annoyance. Therefore, it is important to accurately predict ship noise in order to get an effective environmental noise control in planning new ports, or in widening existing harbor, or in locating new mooring positions. To test the reliability of current commercial simulators in predicting the noise field from complex sources such as ships, in the present work the airborne noise propagation from two different vessels was modelled: a Multipurpose Ship and a Fishing Research Vessel. The development of the model for both ships was performed in five steps: acquisition of the input data; modelling of the ship in the sound propagation software; definition of the noise sources; model validation; output data generation. Simulated data were then compared with on field measurements. The obtained results rise some questions about the measurement techniques adopted to characterize the source levels and the validation data, the simplifications made on the ship surface and the typologies of sources utilized in the study. Future developments in numerical simulators are needed in order to better describe outdoor noise propagation from ships, taking into account the specific nature and complexity of such sources.