Acoustic characterization of laboratory breaking waves in fresh and salt water

Abstract

Results of a laboratory experiment to characterize the underwater acoustic noise radiated from breaking waves in fresh and salt water are described. The underwater sound field radiated by various breaking waves intensities in fresh water in the range from 0.1 to 20 kHz were reported earlier [A. R. Kolaini and L. A. Crum, J. Acoust. Soc. Am. (in press); 92, 2349(A) (1992)]. These waves were generated by a computer-controlled plunging-type wavemaker and propagated along a 12.7-m-long channel where they were made to break at the midsurface of a 3.6-×3.6-×2.4-m anechoic tank. Specific attention is given to a comparison of the results obtained in salt and fresh water. The sources of acoustic radiation from bubble clouds, the average sound-pressure level, bubble clouds shape, bubble concentration, and size distribution in these medium are discussed. These results may provide considerable insight into the likely source mechanisms for ocean ambient noise.