CHARACTERISING CAVITATION NOISE BY WAVELET PACKET REPRESENTATION

Y. Wen, M. Henry

Abstract

Cavitation noise is comprised of burst waveforms resulting from the collapse of cavitating bubbles. Any burst is the mixture of impulses from individual bubbles collapsing in close proximity. A single bubble collapse contributes either to the duration or to the amplitude or to both in the actual mixed burst. Generally, as the severity of cavitation rises, both the amplitude and the duration of impulses in the bursts increase. In any practical system, the vibroacoustic signal of cavitation is blurred by unwanted noise. As the vibroacoustic burst of cavitation is time-frequency concentrated, the orthogonal wavelet packet bases are used to represent cavitation noise. The cavitation bursts are represented as the linear combination of the chosen wavelet packet bases. The wavelet packet coefficients describe cavitation in different frequency components and can discriminate individual bursts in raw data. Furthermore, the wavelet packet decomposition divides the signal into different frequency subbands. Thus the blurred noise can be treated as independently random variables in subbands and is suppressed by thresholding the coefficients.

Keywords

acoustic measurement, cavitation, wavelet packet

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IMEKO-WC-2000-TC10-P282.pdf

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IMEKO TC

TC10 - Measurement for Diagnostics, Optimization and Control

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