MARINE VESSEL NOISE MEASUREMENT
Active research and software development have been carried out in recent years to calculate the broadband noise emitted from a cavitating propeller and the frequency content of this noise at the propeller rotation speed. Field measurement data has been collected and used to evaluate the patterns of noise emitted from different types of vessels and to impute impact on the broader environment.
Challenges encountered in this work include that available measurement data has often not been well enough associated with the specific vessel meta data that is needed as input for the validation of URN prediction methods. The resulting URN analysis then lacks reference to the more detailed modeling of the ship hull form, propeller, interaction of hull and propeller, and machinery configuration. Simplified methods for obtaining fast comparative evaluations at the vessel early design stage are therefore not able to produce the full sought after benefits due to the lack of aggregation of this associated vessel information.
The approach taken by eSonar together with ABS and Memorial University has been to design a fully integrated data collection plan that encompasses both onboard measurements of vibration at key locations including directly at the engine beds, and internally on hull plates proximate to the propellers to capture both cavitation and propulsion generated vibration. This data is then analysed to provide guidance to the vessel crew by linking thrust and speed to generated noise, allowing actions to be taken when quiete running is required.