Measurements of ship noise using an acoustic camera: A first survey

While the acoustic impact of harbours is becoming an increasingly important issue, to the point of limiting their growth, the measurement of noise from ships and port operations is still rough. Two of the main problems that are commonly encountered are source overlapping and large distance from the emitting sources. Source overlapping prevents from identifying the specific contribution coming from each acoustic source. The large distance from the emitting sources, for instance the funnel of a ship or the engine of a transtainer crane, makes the measurement inaccurate. By using the acoustic camera it is possible to tackle these two problems at the same time. Noise measurements can be made with equipment far from noise source, while distinguishing the contribution from each single source emitting within the sound field. The paper demonstrates this enhanced measurement technique through a set of surveys performed inside French and Italian ports. The ship emissions are analyzed through the acoustic camera for ship on the way, maneuvering inside the harbour, and berthed at wharf. The effectiveness of beamforming technique is discussed, investigating the measurements accuracy, their qualitative and quantitative significance, and the possibility to introduce specific measurement standards for ships based on this methodology.