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g. Modulation Analysis of Cavitation Noise

Cavitation noise is produced by the formation and collapse of bubbles on the surface of underwater propellers. Acoustic recordings of cavitation noise are broadband and noise-like, yet distinctly rhythmic as the propeller blades rotate through water flow inhomogeneities. With Prof. Les Atlas (UWEE) and Dr. Ivars Kirsteins (NUWC), our goal is to develop maximum-likelihood demodulation algorithms for characterizing the rhythmic components of cavitation noise. By treating the carrier as a stationary noise signal, the maximum-likelihood approach precisely defines what modulations can and can't be detected from a random process.

  • P. Clark, I.P. Kirsteins, and L. Atlas, "Existence and estimation of impropriety in real rhythmic signals," Proc. IEEE ICASSP, Kyoto, Japan: 2012. [pdf]
  • P. Clark, I. Kirsteins and L. Atlas, "Multiband analysis for colored amplitude-modulated ship noise," Proc. IEEE ICASSP, Dallas, TX, 2010. [poster (PDF)]
Photographs of cavitating propellers.

Modulation spectrum of actual cavitation data, showing the fundamental propeller rate of 2.8 Hz with varying intensity depending on carrier (acoustic) frequency.