Modelling Wind Dependent Acoustic Transmission Loss due to Bubbles in Shallow Water

  • Hans G. Schneider

Abstract

The acoustic transmission loss data from 1 to 8 kHz reported by Wille et al. (preceding paper) over a wide range of windspeeds in shallow water of 30 m depth exhibits a significant loss component which is attributed to bubbles. Indeed, the standard loss mechanisms, losses due to spreading, medium attenuation, bottom absorption and rough surface scattering are not sufficient to explain the data. Hence an absorbing layer of bubbles beneath the sea surface is additionally included into a stochastic ray-tracing routine to model the transmission loss. From the fitted attenuation coefficients a bubble density is estimated with a slope of -3.5 versus bubble radius which is in agreement with literature. In an intermediate range of windspeeds and waveheights the attenuation due to rough sea surface scattering is of equal importance to the transmission loss as the attenuation by bubbles, while at sufficiently high windspeeds the transmission loss is rather insensitive to the significant waveheight which is also observed in the measured data.

An extrapolation to 120 m waterdepth yields basically the same results, except for the insensitivity of the TL to waveheight at high windspeeds.

Keywords

Clay Attenuation Cavitation Acoustics 

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References

  1. Clay, C.S. and H. Medwin, 1977, “Acoustical Oceanography” J. Wiley & Sons, New York.Google Scholar
  2. Lovik, A., 1980, Acoustic Measurements of the Gas Bubble Spectrum in Water, in “Cavitation and Inhomogeneties in Underwater Acoustics”, W. Lauterborn, ed., Springer-Verlag, 1980.Google Scholar
  3. Novarini, J.C., and D.R. Bruno, 1982, Effects of the sub-surface bubble layer on sound propagation, J. Acoust. Soc. Am. 72 (2), Aug 1982, p. 510.ADSCrossRefGoogle Scholar
  4. Schneider, H.G., 1976, Rough Boundary Scattering in Ray-Tracing Computations, ACUSTICA Vol. 35 (1), 1976, p. 18–25.ADSGoogle Scholar
  5. Wille, P.C., D. Geyer, L. Ginzkey, E. Schunk, 1986, Measurement of Wind Dependent Acoustic Transmission Loss in Shallow Water Under Breaking Waveconditions, presented at 12 ICA Associated Symposium on Underwater Acoustics (this book, preceding paper).Google Scholar
  6. Wu, J., 1981, Bubble Population and Spectra in Near-Surface-Ocean: Summary and Review of Field Measurements, J. Geophys. Res. Vol. 86, No. CI, p. 457.ADSCrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1987

Authors and Affiliations

  • Hans G. Schneider
    • 1
  1. 1.Forschungsanstalt der Bundeswehr fur Wasserschall und GeophysikKiel 14Germany

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