Acoustical Properties of Water-Filled Sands

Abstract

Experimental studies were made of the propagation of longitudinal waves in several mixtures of water with quartz sands fractionated as to particle size. The most probable particle size in the several samples ranges from 0.01 to 0.07 cm. The experimental frequencies were approximately 400 to 1000 kc/sec. Additional measurements in the same frequency range cover the reflection and scattering of underwater sound from essentially plane surfaces of these aggregates. The velocity and attenuation data are related satisfactorily to a well-known analysis for a porous acoustical material having a pliable skeleton. The reflected signal, as a function of angle of incidence, behaves approximately as expected from the conditions for continuity at the plane surface, when the appropriate complex index of refraction is used. The scattering data are compared with the analysis based on a random distribution of scattering amplitude per unit volume, with autocorrelation distance proportional to the particle size. The analysis predicts the limiting behavior of scattering coefficient with respect to particle size and frequency, but predicts a more rapid fall of scattering amplitude beyond the critical angle than was observed. The magnitude and autocorrelation properties of the fluctuations in scattered signal as the apparatus was translated to scan the sand surface were observed, and found to correspond approximately to a model based on a Gaussian distribution of local scattering amplitude.

High-frequency dispersion from viscous drag at the grain-grain contact in water-saturated sand

“…Their measurements show speed decreasing as f −3 and attenuation increasing as f 4 ; their models approximately fit the data, although they predicted a speed decrease that goes as f −2 . Attenuation in well-sorted, vibrationcompacted, water-saturated sand between 100 kHz and 1 MHz measured by Nolle et al 7 increased as f 1/2 , consistent with a viscous loss model due to relative motion between pore fluid and the sand grains, similar to Biot's theory. Speed dispersion was not addressed in the experimental measurements.…”

Normal incidence reflection loss from a sandy sediment

“…The laboratory measurements by Nolle, Hoyer, Mifsud, Runyan and Ward [7] were made at 500 kHz and 1 MHz, using graded, cleaned, degassed and packed sands: Four samples, with mean grain diameters, 0.64,0.4,0.17 and 0.12 mm, were used. The reflection loss was found to be 11 dB, with an error of ±0.5 dB, independent of grain size and frequency.…”

High frequency measurements of sound speed and attenuation in water-saturated glass-beads of varying size

“…The measurements are compared with earlier measurements obtained by four research groups [4][5][6][7] to see how they match. The laboratory measurements by NHMRW (Ref.…”

“…5) is found in literature, their objective was to confirm the validity of Biot theory using their measurements. In this paper, the authors focus in analyzing the dispersion relation of the measured data as a function of frequency and mean grain size, and comparing with earlier measurements obtained, respectively, by Nolle, Hoyer, Mifsud, Runyan, and Ward (NHMRW), 4 SS, 5 Schwartz and Plona (SP), 6 and Lee, Humphrey, Kim, and Yoon (LHKY). 7 Section 2 describes the experimental setup including the sediment preparation along with measurement techniques.…”

“…However, few studies 4,5 have been made around the frequency range of a few hundred kilohertz and/or with a wide selection of granular media categorized by its mean grain size.…”