Experimental methodologies for noise source diagnostics in marine and naval engineering

The present paper describes two "unconventional" approaches to experimentally address the diagnostics, analysis and solution of hydroacoustic problems in naval engineering. The first approach, based on direct pressure fluctuation measurements combined with detailed flow measurements in the proximity of the noise source, provides a direct estimate of the flow phenomena at the origin of sound generation and emission. The second approach concerns the use of an acoustic analogies in combination with a time resolved velocimetry technique capable of resolving all the velocity gradients at an instant. The abilities of the two approaches are investigated with reference to the analysis of the noise sources in some reference case studies.