Propellers are one of the most important noise sources on board ships. They produce both structureborne and radiated noise with a spectrum that usually covers a wide range of frequencies, with both tonal (blade passage related) and broadband components.

Tonal noise mostly affects the low frequency range. It generally features narrow peaks in the noise spectrum and contributes importantly to the ship acoustic signature. Broadband noise covers a wide frequency range, up to 10 kHz; it is due to a number of different phenomena, cavitation playing a major role as an effect of the collapse of cavitation bubbles, which generates high frequency acoustic waves. 

The prediction of propeller noise is a relevant issue and still an open one as numerical methods to predict noise levels radiated by propellers are not yet satisfactorily accurate. On the other hand, an increasing sensitivity to environmental issues is likely to bring about new, more restrictive regulations concerning noise levels from ships, with the subsequent need to make accurate prediction of propeller noise at the design stage.

In this frame, Fincantieri and CETENA are devoting efforts to develop tools and methodologies to effectively support the design of silent propellers. 

The proposed paper presents a methodology to predict tonal noise from propellers. The methodology involves a full hydrodynamic characterisation of the propeller, the identification of propeller equivalent noise sources and the computation of the propeller acoustic field with a BEM method. Besides discussing the methodology, the paper will present an application of the methodology to the prediction of the propeller tonal noise radiated by a Fincantieri vessel.