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The phase velocity of ultrasound was measured in suspensions of spherical glass particles in water with particle size parameters (particle size / wavelength) ranging from ca. 0,01 to 40. Two different measurement techniques have been tested: i) A narrow-band tone-burst (tb) setup with comparison of the signals that have run through the suspension with the pure fluid signals, and ii) a continuous-wave (cw) technique that evaluates the phase-shift between the transmitted and the received wave. In both cases, phase velocity could be measured with attenuations of up to 80 dB, allowing for particle concentrations of up to 30% by volume. As far as the authors know, measurements in this combination of wavelength and concentration have never been published before. Although the two methods bear out quite different results, none of them has to be wrong; the stationary phase velocity, measurable with the cw-technique, might differ from the transient phase velocity. The experimental results are compared with two theoretical models, one for the range of intermediate particle size parameters, where viscous drag and pressure gradient forces are the dominant particle-wave interaction mechanisms, and one for the scattering dominated regime of wavelength ≤ particle sizes. The best fit is obtained with the tone-burst technique and a newly developed model based on the dispersion equation.
Document Type: Research Article
Publication date: November 1, 1999
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Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.