Merchant ship-radiated noise source levels

Ship-radiated noise is the principal source of noise in the 20–300 Hz frequency regime. This presentation provides a review of the issues relating to measuring ship-radiated noise source levels and predicting the source levels from ship parameters. The process of measuring and calculating the source levels is covered, including a discussion of propagation effects and source representation. Based on measurement results it is shown that, contrary to the classical model of shipping source levels, there is a negligible correlation between the source levels of an ensemble of ships and the transiting speeds and lengths of those ships. Issues concerning using the source level model in a modeling environment are discussed, including some effects of changing speed and source depth. Additionally, evidence is presented that predictions of increases in the source levels of the world’s ships based on increases in their speeds is not justified, while increases due to size (length) are not trivial. [Work supported by the ONR through NRL-base funding.]