A model for variations in the range and depth dependence of the sound speed and attenuation induced by bubble clouds under wind-driven sea surfaces

• Published in: IEEE journal of oceanic engineering Vol. 23; no. 4; pp. 423 - 438
• Main Authors: Novarini, J.C., Keiffer, R.S., Norton, G.V.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.10.1998; Institute of Electrical and Electronics Engineers
• Subjects: Acoustic measurements; Acoustic propagation; Attenuation; Clouds; Earth, ocean, space; Exact sciences and technology; External geophysics; Marine; Marine optics and underwater sound; Oceans; Physics of the oceans; Reverberation; Sea measurements; Sea surface; Underwater acoustics; Underwater sound; Velocity measurement; Sea surface; Wave attenuation; Sound propagation; Depth profile; Wind driven sea; Theoretical study; Models; Air bubble; Sound velocity
• ISSN: 0364-9059; 1558-1691
• DOI: 10.1109/48.725236

When modeling sound propagation through the uppermost layers of the ocean, the presence of bubble clouds cannot be ignored. Their existence can convert a range-independent sound propagation problem into a range-dependent one. Measurements show that strong changes in sound speed and attenuation are produced by the presence of swarms of microbubbles which can be depicted as patchy clouds superimposed on a very weak background layer. While models suitable for use in acoustic calculations are available for the homogeneous bubble layer (which results from long time averages of the total bubble population), no similar parameterizations are available for the more realistic inhomogeneous bubble layer. Based on available information and within the framework of a classification scheme for bubble plumes proposed by Monahan, a model for the range and depth dependence of the bubbly environment is developed to fill this void. This model, which generates a possible realization of the bubbly environment, is then used to calculate the frequency-dependent change in the sound speed and attenuation induced by the presence of the bubble plumes. Time evolution is not addressed in this work.