Sound Speed Dispersion Research Articles

Counting bubbles acoustically: a review

The acoustical resonance characteristics of bubbles are the key to their detection by backscatter, excess attenuation and sound speed dispersion in bubbly liquids. The linear, lumped-constant, behaviour of single bubbles is reviewed and formulated in terms of the physical constants of the medium liquid, the bubble gas and the interface between. Acoustical techniques for bubble counting are discussed using in-situ experiments at sea as an example.

Sound Speed Dispersion and Fluctuations in the Upper Ocean: Project BASS

supported by Code 302, Naval Ship Systems Command, and the Royal Australian Naval Research Laboratory

Acoustic miniprobing for ocean microstructure and bubbles

Analysis of sound phase and amplitude fluctuations over a 1-m range has provided in situ statistics that can be used to infer the statistics of the ocean microstructure. A particularly fruitful use of such a simple acoustic miniprobe is the study of the sound phase fluctuations near the sea surface. With the aid of simultaneous statistics of temperature and wave height the observed sound phase fluctuations have been used to calculate bubble statistics at sea. At sound frequencies less than about 25 kHz the sound speed dispersion and its fluctuations reveal the bubble volume fraction and its standard deviation, respectively. At higher sound frequencies a large resonant bubble population can be identified by a cross correlation of sound phase and ocean wave height. In this case the predominant part of the sound phase modulation is caused by the changing bubble radius due to the fluctuating wave height. The spectrum of the sound phase modulation then mimics the ocean wind wave spectrum, and its change with depth can be used to infer the change of number of resonant bubbles with depth.

Sound-speed dispersion in liquid cylinders: Del Grosso, V.A., McGill, R.E. Vol 48, No 5 (November 1970) pp1294–1296

Sound-speed dispersion in liquid cylinders: Del Grosso, V.A., McGill, R.E. Vol 48, No 5 (November 1970) pp1294–1296

Light Scattering from Chemically Reactive Fluids. IV. Intensity Calculations for the Eulerian Fluid with One Reaction

The hydrodynamic equations for the reactive Eulerian fluid (zero transport coefficients, one chemical reaction) have been used in the thermodynamic approach to calculate in detail the spectrum of scattered light. The mathematical technique employed was the matrix eigenvalue formulation previously introduced [L. Blum and Z. W. Salsburg, J. Chem. Phys. 48, 2292 (1968)]. The method focuses on a particular matrix which is easily derived from the linearized hydrodynamic equations. The fluctuations of the set of independent variables are resolved into normal modes of relaxation. Each mode contributes one peak to the spectrum; the position and half-width of the peak are furnished directly by the eigenvalue, while the intensity is calculated from the corresponding normal mode projection matrix. Some general relationships between positions and half-widths are derived. The Rayleigh peak due primarily to chemical reaction relaxation is considered in detail. Various intensity ratios involving this peak are calculated, and simple criteria are set forth for determining whether it will be intense enough to be experimentally observed. If it is observable, the reaction rate constant can be obtained from measurements of its half-width. Two other chemical relaxation effects, dispersion of the sound speed and skewing of the Brillouin peaks, are also examined. For small scattering angles and very fast reactions, the rate constant may be extracted from measurements of the sound speed dispersion. The range of relaxation times for which experiments seem feasible is 10−4–10−11 sec.

Sound-Speed Dispersion in Liquid Cylinders

An inversion of the ordinate in the usual plot of the dispersion curves for axial acoustic propagation in liquid cylinders permits tracking the modes from their evanescent region for proper ordering and greater confidence in their use for acoustic waveguide mode analysis.