High-Frequency Sound-Speed, Attenuation, and Reflection Measurements Using Water-Saturated Glass Beads of Different Sizes

Sound propagation in water-saturated glass beads was studied under controlled laboratory conditions over a frequency range from 200 to 900 kHz for sound-speed measurements and from 200 to 800 kHz for attenuation measurements. The influence of the grain size on both p-wave speed and attenuation was studied using three kinds of glass beads. A strong negative dispersion of the sound speed over the whole frequency range studied was observed with the three different populations of beads used in this experiment (mean grain size: 272 μm, 520 μm, and 1.33 mm). In addition, it was found that not only does the attenuation increase nonlinearly with frequency, but it also depends on the size of the beads. These results are consistent with earlier measurements performed by other researchers over the same frequency range with glass beads of about the same sizes. In this paper, we also discuss the results of the measurement (over a wide frequency range: 200 kHz-1.5 MHz) of the reflection coefficient of a thick slab of glass beads whose surface was smoothed, as well as the correlation between the behavior of this reflection coefficient and the negative dispersion of the sound speed. For this experiment, five populations of beads (91 μm, 272 μm, 520 μm, 133 mm, and 2.98 mm) were used.