Airborne Sound Propagation Induced by a Cruise Ship Through Simulation and Correlation with Real Measurements

Abstract

The publication of the Lloyd’s Register notation [1], in addition to port and civil regulations, may in the future result in shipowners requesting certification of the airborne noise levels emitted by their vessels, necessary to access areas of natural interest or certain ports [2]. This study models the sound propagation induced by a cruise ship using a software tools, starting with a database of measurements and calculations on the sound power generated by the main sources in accordance with ISO 9614-1 [3] and 9614-2 [4]. The results compared with real measurements in the far field showed the need to calibrate the model through a campaign of measurements of on-board sources in terms of sound power and pressure. The experimental measurements of sound pressure and power were used as input for the numerical models that were developed using a commercial software package, estimating in advance the noise levels measured at different distances from the vessel. In a subsequent phase of the study, the estimated data were compared with those calculated through a second experimental measurement campaign performed under the operating conditions indicated by the Lloyd’s Register Class Notation and at progressive distances from the vessel. The simulations allow to estimate the contribution of the individual sources for any desired point and the interventions ad hoc to improve comfort levels in specific positions on board that can be obtained by optimising interventions on the sources to a minimum. The development of this approach has resulted in a predictive tool with a degree of accuracy in the range required by ISO 9613 [5] and therefore capable of assessing the airborne noise emitted, comparing it with the limits imposed by the LR’s regulations or, in general, by port and civil regulations. This approach is also a useful tool for estimating the noise level in external passenger areas and therefore for a project aimed at improving on-board comfort.