Evaluation of a semi-empirical method for the propeller noise spectrum of a fisheries research vessel

The underwater noise created by commercial shipping significantly contributes to the ambient noise levels of the world seas; therefore the rising environmental awareness concerning the commercial shipping emissions has recently targeted the noise radiated from commercial vehicles. Within this framework this paper presents the evaluation of a semi-empirical method and associated computer code, PROS-SPEC (Propeller Noise Spectrum Program), to predict the propeller underwater noise spectrum of ships by making use of an available model and full-scale noise data for a Fisheries Research Vessel (FRV). The full-scale noise spectra data are first obtained by the extrapolation of the noise measurements made in the Emerson Cavitation Tunnel of Newcastle University, which is a middle size cavitation tunnel, and compared with the full-scale trials of the FRV. Hence the details of this extrapolation procedure are first given in the paper. This is followed by an in-depth review of the semi-empirical method, which is used as the basis in the PRO-SPEC code, with a view to its potential application to wider ship types using a larger database. In this respect initially the conceptualization of the noise spectra into its cavitating and non-cavitating components are made and a critical review of the database is presented by scrutinising the regression analysis and its dominant parameters representing the data base. Following this critical review the semi-empirical method is evaluated to predict the noise spectra of the subject FRV for which both the model test based extrapolations and full-scale measurements are used. The comparison of the predicted noise spectra with the extrapolated data and full-scale measurements present reasonable accuracy with a useful insight into the cavitating and non-cavitating contributions and indicating the useful potential of the method to wider applications.which are further discussed in the paper.