Evaluation of airborne noise due to navigation and manoeuvring of large vessels

Airborne noise produced by large vessels during navigation procedures and manoeuvres while approaching harbours could be critical when the surrounding areas are residential or naturalistic, e.g. harbours situated inside lagoons or on wide rivers. The characterization of sound power emitted by large vessels is important also when noise predictions need to be made. Noise measurements during transit should define the main sound sources of the vessels, where they are located and their directivity. This is generally quite difficult due to several aspects related to the distance and the height of the reception positions required for the correct evaluation of the directivity of the source and the presence of residual noise determined by other sources. Technical standards are not useful in these cases because they aim to define the evaluation procedure for specific types of ships, mainly small, during mooring or manoeuvring at a short distance from the pier. In the present paper an analysis of experimental measurements for the evaluation of airborne noise due to navigation and manoeuvring of large vessels is reported, with particular reference to cruise ship pass-bys observed from different monitoring positions.