Measurements of airborne noise emitted by a ship at quay

The problem of the impact of airborne noise emitted by commercial ships moored at quay is gaining attention by Regulatory Bodies. The question is often raised by citizens sending complaints to the municipalities of port cities in which the harbour is located inside the town. The problem may be even more important in the case of pleasure crafts accessing protected areas and mooring there. Limit levels for airborne noise emissions started therefore to be fixed in normative as well as contract requirements. In the light of what above, an effective measurement procedure to characterise the noise emissions from ships and compare them to limits plays an important role. The procedure needs to take into account aspects linked to the ship source characteristics (dimensions, complexity, directivity) as well as related to the surrounding environment, which is often represented by the shipyard where the ship is built. The latter aspect includes the presence of obstacles and reflecting surfaces around the ship, as well as significant components of background noise. The paper recalls the background of a measurement procedure that was defined within the project SILENV of the 7th Framework Programme specifically for the purpose of the characterisation of ships as airborne noise sources and reports a trial application of this procedure to a ship moored at a yard quay. Instrumentation used and data post processing are discussed, together with practical problems encountered and solutions found in order to carry out measurements.