What is ISO 20233-2 - Noise source localization about?
ISO 20233-2 is the second part of the ISO 20233 series of standards that specifies a model test method for propeller cavitation noise evaluation in ship design, focusing mainly on noise source localization. The procedure comprises the model test set-up, noise measurements, data processing and source localization. The target noise source being propeller cavitation, ISO 20233-2 describes the test set-up and conditions to reproduce the cavitation patterns of the ship, which is the same as in ISO 20233-1. The noise measurements are performed using a hydrophone array for the source localization. Therefore, the instrumentation of the hydrophone array is also addressed, as well as a suitable array signal processing of the measured data. Finally, a method to visualize and interpret the results is presented.
Note: ISO 20233-1 also serves to provide an example of protocols for acoustic localization which is a relatively new research area.
Who is ISO 20233-2- Noise source localization for?
ISO 20233-2 on ship propulsion systems is useful for:
- Ship manufacturers
- Ship design engineers
- Propeller manufacturers
- Quality control personnel
Why should you use ISO 20233-2 - Noise source localization?
Propeller cavitation is the major noise source in commercial ships. The propeller cavitation noise can be assessed by experimental and/or numerical methods in propeller design stage. The numerical methods, such as computational fluid dynamics (CFD) or empirical formulae, might be a good alternative to propeller cavitation noise evaluations. However, the model tests are still used widely for research on propeller cavitation noise. The objective of the model test is to reduce the propeller noise in ship design by evaluating propeller cavitation noise characteristics at the design phase. Localizing the noise sources in the design stage, as well as predicting its noise levels, might be very helpful. ISO 20233-1 addresses the prediction of propeller noise levels. In order to specify the location of noise source, visual observation of cavitation is the most practical way in view of spatial resolution and efficiency, as the main source of hydrodynamic noise in merchant ship is cavitation. In addition to this observation, noise source localization technique using hydrophone array is under development for verifying the observed noise source location. Thus ISO 20233-1 devotes to the source localization method as a new part of a model test method for propeller cavitation noise evaluation in ship design.
