Research Required to Support Comprehensive Nuclear Test Ban Treaty Monitoring (1997) / Chapter Skim
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Appendix E: Hydroacoustics
Appendix E: Hydroacoustics
Pages 121-124
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From page 121... ...
In shallow waters or at distances from a deep water source comparable to the water depth, the wavefront expands cylindrically, and sound pressure geometric loss is proportional to 1/r. In practice, transmission losses are usually calculated more precisely by a variety of numerical solutions of the scalar wave equation.
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From page 122... ...
In the spectral region between 10 and 100 Hz the noise field is dominated by worldwide ocean shipping and by wind-driven breaking waves. These higher-frequency sources create a more or less continuous red noise spectrum, high at the lowest frequencies and decreasing at 8 to 10 dB per octave up to about 20 Hz, where the spectrum flattens somewhat due to the influence of shipping noise.
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From page 123... ...
As the bubble expands, the pressure inside decreases. The momentum of the water continues the expansion of the bubble beyond the point at which the internal pressure falls below the external hydrostatic pressure, and the bubble contracts, thereby compressing the gas until its pressure is sufficient to halt the motion of the water, whereupon the cycle repeats, each time with diminished intensity.
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