Attenuation Of Sound Waves Research Articles

Broadband Ultrasound Attenuation Predicts Fractures Strongly and Independently of Densitometry in Older Women

<h3>Background:</h3> Quantitative ultrasound of bone is a new radiation-free technique that measures bone mass and may assess bone quality. Retrospective studies have suggested that low-bone ultrasound of the calcaneus is associated with an increased risk for hip and other fractures in older women. <h3>Objectives:</h3> To establish the utility of calcaneal quantitative ultrasound of bone for the prediction of fractures and to compare quantitative ultrasound of bone with bone mineral densitometry by performing a prospective cohort study within the Study of Osteoporotic Fractures. <h3>Subjects and Methods:</h3> We studied 6189 postmenopausal women older than 65 years at 4 US clinical centers. Broadband ultrasound attenuation (BUA), a measurement of the differential attenuation of sound waves transmitted through the calcaneus, and bone mineral density of the calcaneus and hip were measured. Subsequent hip and other nonspine fractures were documented during a mean follow-up of 2.0 years. <h3>Results:</h3> In age- and clinic-adjusted analyses, each SD reduction in calcaneal BUA was associated with a doubling of the risk for hip fractures (relative risk [RR], 2.0; 95% confidence interval [CI], 1.5-2.7); a similar relationship was observed with bone mineral density of the calcaneus (RR, 2.2; 95% CI, 1.9-3.0) and femoral neck (RR, 2.6; 95% CI, 1.9-3.8). After adjustment for bone mineral density of the femoral neck, BUA was still associated with an increased risk for hip fracture (RR, 1.5; 95% CI, 1.0-2.1). Intertrochanteric fractures in particular were strongly associated with a low BUA measurement (RR, 3.3; 95% CI, 2.0-5.5). <h3>Conclusions:</h3> Broadband ultrasound attenuation predicts the occurrence of fractures in older women and is a useful diagnostic test for osteoporosis. The strength of the association between BUA and fracture is similar to that observed with bone mineral density. Arch Intern Med. 1997;157:629-634

PHYSICAL ACTIVITY, BONE QUALITY AND BONE QUANTITY IN PRE- AND PERI-MENOPAUSAL WOMEN 13

Ultrasonic analysis of bone measures the attenuation of sound waves (BUA) and the speed of sound (SOS) waves passed through the calcaneus. Although correlated with bone mineral density (BMD), these parameters are thought to also assess architectural properties of bone that may be independent of bone mass. Physical activity is positively related to bone mass but few studies have examined its relationship to bone ultrasound parameters. This cross-sectional study of 250 women aged 45-52 examined the relationships between leisure-time physical activity (LTPA), bone quality as measured by a bone ultrasound analyzer (Walker-Sonix 575) and femoral neck and lumbar BMD as measured by dual-energy x-ray absorptiometry (Hologic,Inc.). Past-week LTPA was assessed by an interviewer-administered questionnaire. LTPA was correlated with SOS (r=.18, p<.01), BUA (r=.12, p=.06), and femoral neck BMD (r=.13, p<.05) but not lumbar BMD (r=.01). Women in higher quartiles of physical activity had higher bone quality (BUA and SOS) and BMD adjusted for body mass index (BMI), (see table). Controlling for BMI, race, age, and menopausal status, multiple linear regression indicated that physical activity is a significant predictor of SOS, BUA and femoral neck BMD but not lumbar BMD. The relationship between physical activity and SOS was also significant in models controlling for BMD. These results suggest that higher levels of physical activity are positively associated with bone quality as measured by BUA and SOS in pre- and peri-menopausal women.

Low‐temperature Magnetic Properties of Terbium Orthoferrite Single Crystals

AbstractSpontaneous and by an external magnetic field induced magnetic phase transitions in TbFeO3 have been experimentally studied. Precision investigations of velocities of transmission and attenuation of sound wave were made, the processes of formation and rearrangement of magnetic structure examined and its change under the influence of external magnetic field explored. This has been made possible by the development of methods of controlled growth of rare‐earth orthoferrites resulting in the formation of high‐quality single crystals of required size with reproducible physical properties. The measurements were taken in the temperature range from 0.45 to 8.0 K. From the threshold Geld values a Ha  T phase diagram for TbFeO3 has been plotted.

Design and Test of a Sonic Permeameter for Dry Unconsolidated Porous Materials

We developed a sonic permeameter that can quickly measure the intrinsic permeability of dry unconsolidated porous materials in the laboratory. It consists of a control box, a loudspeaker, and an external waveguide filled with the sample. Sound wave attenuation and dispersion are measured by two microphones recessed in the inner wall of the waveguide. They receive a sound pulse that is sent down to the waveguide from the loudspeaker. The permeability of the sample is then calculated from the attenuation and dispersion spectra using our mathematical model. Test results obtained over several dry Ottawa sand and glass bead samples agree very well with the results obtained using a conventional constant‐head permeameter. The advantage of this apparatus is its rapid and automated measurement, easy operation, and potential workability in the field. Theoretical analysis is also extended to a hypothetical case where the porous material is totally saturated with water.

Third sound in He films on copper substrates

We have performed simultaneous measurements of the speed and attenuation of a third sound wave on a glass and on a copper resonator. The third sound wave on the copper substrate is much more difficult to excite with a thermal method, and we can only see third sound waves on the copper substrate for helium films thicker than 14 atomic layers. The measurements were done to prepare for third sound measurements in3He films on a copper substrate below 1 mK. A cell has been prepared to use electromechanical excitation of the third sound waves which is suitable for these thicker films, and which avoids the extra heat input of the thermal excitation. With a small vibrating wire the difference in superfluid transition temperature between bulk3H and3He films can be determined.

Elastic and Dissipative Properties of Solid C60

Elastic and dissipative properties of solid C 60 in the face centered cubic (fcc) and high pressure induced phases were measured on the same specimens. The high pressure phase was synthesized in our experiments by the thermobaric treatment of specimens at temperature of 350 °C and under pressure of 2 GPa. The structure investigations revealed the origination of the chemical bonding between C 60 molecules in that phase. The measurements of attenuation and velocities of longitudinal and transverse sound waves were carried out in the temperature range from 4.2 to 300 K at at the frequencies of 5 and 10 Mhz by echo pulse and high frequency resonance methods. It was found that the values of elastic moduli of the new phase, measured at room temperature, appeared two times higher and their temperature dependences two times weaker than corresponding ones of the pristine C 60 . The internal friction spectrum of fcc phase differs significantly from that of hpp phase. The phenomena observed are discussed in terms of model taking into account the formation of polymer chains in the structure of the new pressure-induced phase of solid C 60 .

Broadband study of the scattering of ultrasound by polystyrene‐latex‐in‐water suspensions

AbstractUltrasonic absorption spectra have been measured between 0.1 and 2000 MHz of aqueous suspensions of polystyrene latex globules. Samples of different diameter (60 to 100 nm) and different concentration of the polystyrene latex particles (volume fraction between 0.05 and 0.38) have been studied. The broadband spectra exhibit a Debye‐type relaxation term in the frequency range around some MHz and a contribution with special characteristics at higher frequencies. The former term is assumed to be due to counterion effects in the surface layer of the globules. No special attention is payed to this effect. The latter contribution is attributed to scattering and mode conversion mechanisms. An approximate explicit and an exact formulation of the theoretical description of the sound wave attenuation by the scattering process are discussed. The explicit formulation enables valuable insights into the mode conversion mechanisms but does not allow for a complete representation of the measured spectra. Application of the exact version leads to the conclusion that in the frequency range under consideration monopole and quadrupole oscillations of the polystyrene latex globules are the dominant cause of ultrasonic wave attenuation. It is found that even at the elevated concentrations used effects of multiple scattering are of minor importance here.

On the propagation of third sound in 4He films

A detailed theory on the propagation of third sound along planar 4He films is presented. The treatment follows the lines set out by Bergman, later also pursued by van Beelen and Bannink, in taking the accompanying waves in vapour and substrate fully into account but omitting the non-linear regime near the onset points of superfluidity of the films. The theory results in a basic set of five linear homogeneous equations for five unknown amplitudes, three of the film variables and two of the vapour. The set is solved numerically for given frequency and substrate properties, yielding values for the speed, attenuation and amplitude ratios of the third sound waves, as functions of film thickness and temperature. The theory is applied to the parallel-plate geometry, in which case each equation can be split into two, yielding two independent sets, one for the symmetric and one for the antisymmetric mode of propagation. The role of the spacing between the plates is illustrated numerically in some examples. It appears that for small spacings the sound wave in the vapour plays an important role for the third-sound propagation, a feature that was not recognized by Bergman. It is also demonstrated that for a narrow spacing, increasing the temperature causes a cross-over from the so-called modified Putterman limit to the vapour dominated limit, which might explain the observed behaviour of the amplitude ratio of film thickness and temperature, recently reported by Laheurte et al. It is finally mentioned that the described treatment could be extended to other geometries by introducing the appropriate geometry-dependent coefficients into the basic set of linear equations.

The damping of flexural and acoustic waves by a bias-flow perforated elastic plate

An analysis is made of the damping of sound and structural vibrations by vorticity production in the apertures of a bias flow, perforated elastic plate. Unsteady motion causes vorticity to be generated at the aperture edges; the vorticity and its energy are swept away by the bias flow and result in a net loss of acoustic and vibrational energy. In this paper we investigate the interaction of an arbitrary fluid-structure disturbance with a small circular aperture in the presence of a high Reynolds number, low Mach number bias flow. By considering the limit in which the aperture is small compared to the length scale of the impinging disturbance, it is shown that the effect of the interaction can be represented by a concentrated source in the plate bending wave equation consisting of a delta function and two of its axisymmetric derivatives. A generalized bending wave equation is then formulated for a plate perforated with an homogeneous distribution of small, bias flow circular apertures. This equation is used to predict the attenuation of sound and resonant bending waves by vorticity production. Acoustic damping is found to be significant provided the fluid loading is sufficiently small for the plate to be regarded as rigid (e.g. for an aluminium plate in air when the frequency is not too small). On the other hand, a bending wave is effectively damped only when the fluid loading is large enough for the wave to produce a substantial pressure drop across the plate; when this occurs the predicted attenuations are comparable with those usually achieved by the application of elastomeric damping materials. Numerical predictions are presented for steel and aluminium plates in air and water.

Experiments on nonlinear acoustics in3He-B

Observations and applications of nonlinear acoustic phenomena in superfluid3He-B are reported. Two-phonon absorption (TPA) by the real squashing (rsq) mode has been detected under several experimental conditions below p = 3.5 bar, using two coincident sound pulses. The attenuation peak height has been investigated as a function of the energy densities of the two sound waves. We discovered the five-fold Zeeman splitting of TPA by parallel sound pulses in an applied magnetic field and the two-fold dispersion splitting due to the finite wave vector of the mode when the two sound pulses are mutually perpendicular. The dispersion relation of the real squashing mode has been investigated at zero pressure and in zero magnetic field by exciting the mode with two parallel, perpendicular, or antiparallel sound waves. Experimental values for the parameters that determine the collective-mode velocities have been extracted from the positions of the observed attenuation maxima. An anomalous structure has been observed in the attenuation and phase velocity spectra of a single high-intensity sound wave near the threshold for pair breaking by two phonons; in an applied magnetic field the phase velocity anomaly splits into a triplet.

The low energy collective excitations in dielectric glasses. The attenuation of sound waves at ultra low temperatures

The up-down interaction between two-level systems in dielectric glasses leads to arising of space-delocalized low-energy excitations subsystem. In the case of ultra low temperatures when the phonons are significantly frozen out the relaxation processes will be defined by the excitations of that subsystem. The low-frequency sound attenuation is studied. It is shown that the attenuation coefficient demonstrates crossover from the known phonon-induced behaviour α ∼ T 3 to α ∼ T at sufficiently low temperature. This behaviour was recently discovered in amorphous SiO 2 [1].

Line shapes in giant quantum attenuation of sound waves in bismuth

The giant quantum attenuation in semi-metals, which was predicted by Gurevich, Skobov, and Firsov, is affected by the deformation potential. In a strong magnetic field, the deformation potential strongly depends on the density of states. We have calculated the curves of attenuation coefficient in bismuth taking the density-of-states dependence of deformation potentials into account. The satisfactory result which quantitatively agrees with the experimentally observed line shapes of sound attenuation is obtained.

Attenuation of sound waves in drill strings

During drilling of deep wells, digital data are often transmitted from sensors located near the drill bit to the surface. Development of a new communication system with increased data capacity is of paramount importance to the drilling industry. Since steel drill strings are used, transmission of these data by elastic carrier waves traveling within the drill pipe is possible, but the potential communication range is uncertain. The problem is complicated by the presence of heavy-threaded tool joints every 10 m, which form a periodic structure and produce classical patterns of passbands and stop bands in the wave spectra. In this article, field measurements of the attenuation characteristics of a drill string in the Long Valley Scientific Well in Mammoth Lakes, California are presented. Wave propagation distances approach 2 km. A theoretical model is discussed which predicts the location, width, and attenuation of the passbands. Mode conversion between extensional and bending waves, and spurious reflections due to deviations in the periodic spacings of the tool joints are believed to be the sources of this attenuation. It is estimated that attenuation levels can be dramatically reduced by rearranging the individual pipes in the drill string according to length.

The effect of heat treatment on the elastic and dissipative properties of copper with the submicrocrystalline structure

The effect of the heat treatment on the attenuation and velocity of sound waves of different types, measured at frequencies ∼ 15 Hz, 100 kHz and 5 MHz, has been studied in submicrocrystalline copper of different purity. The samples with grain size of 0.2 μm were obtained by equichannel angular pressing method. A drastic irreversible increase of velocity values after annealings above some characteristic temperature T 0 was observed. T 0, according to electron microscopy studies, coincided with the temperature of primary recrystallization. The temperature dependences of sound velocity and internal friction in as-prepared samples display the internal friction peak and corresponding sound velocity jump near T 0, the peak temperature being independent of frequency. The results obtained are considered in terms of models which describe the influence of structure defects on the elastic and dissipative properties of crystals.

Quantum fluctuations and ultrasonic attenuation in tunnel junctions

The general problem of tunnelling, for arbitrary temperatures and voltages in ordinary long and narrow tunnel junctions, when a longitudinal ultrasonic wave propagates through normal tunnel junctions perpendicular to the barrier plane, has been investigated. The peculiarities of the constant and alternating tunnel current (TC) and the sound attenuation, connected with the quantum fluctuations of the voltage, have been considered and the question of the experimental measurement of sound wave attenuation and amplification in superconductor junctions has been discussed.

Thermal attenuation and dispersion of sound in a periodic emulsion.

We investigate the attenuation and dispersion of sound waves in suspensions and emulsions caused by the thermal-transport process. They combine to constitute the effective compressibility of the system. We begin with an attempt to justify the Isakovich formula for calculating the effective compressibility. The formula is then rewritten in terms of the interfacial heat flux. Isakovich's analysis is simply an independent-particle approximation. It is the purpose of this paper to consider the effect of interparticle interactions. The effective compressibility is calculated for an array of spherical particles or droplets centered at the points of a periodic lattice, immersed in a fluid of different species. Ewald's method of fast-convergent lattice sums in electrostatics is extended to a technique for the heat-conduction problem in a periodic emulsion. The computation for cubic lattices reveals that the interparticle interactions act to reduce, in the lower-frequency range, both the attenuation coefficient and the departure of the sound velocity from its high-frequency limit. The striking feature is that a drastic change in attenuation occurs when the thermal conductivity of the particle is substantially larger than that of the ambient fluid.

Longitudinal viscosity of liquid alkali metals

The viscosity coefficient entering sound wave attenuation is evaluated for the liquid alkali metals in an ion-electron plasma approach. It is shown that the contribution from electrical conduction, though small, is by no means negligible. The calculated longitudinal viscosity is very close to the measured shear viscosity contribution, the bulk viscosity being expected to be small in the present approach.

Observation of high-gain nonlinear acousto-optic amplification

We describe a procedure by which the optical and acoustic waves present in an acousto-optic beam deflector are strongly amplified through nonlinear optical pumping. This amplification is manifested as an increase in the diffraction efficiency of an acousto-optic beam deflector. In particular, we describe the design and experimental test of a prototype TeO(2) device in which this diffraction efficiency was increased by more than 2 orders of magnitude under pulsed laser illumination. This high degree of amplification results from an acoustic gain mechanism that counteracts the usual attenuation of sound waves propagating in an acousto-optic medium. We discuss possible applications of this gain mechanism in a new class of nonlinear acousto-optic device.

Attenuation of sound waves in lattice gases

Abstract The theoretical expression for the attenuation of plane waves for a two-dimensional FHP lattice gas with zero average velocity is derived and compared with simulation results.

A pairwise interaction theory for determining the linear acoustic properties of dilute bubbly liquids

The problem of determining the acoustic properties of dilute bubbly liquids is examined using the method of ensemble-averaged equations and pairwise interactions. The phase speed and attenuation of sound waves in the small-amplitude regime are determined as a function of frequency of sound waves including the effects of finite surface tension, small viscosity of the liquid, and non-adiabatic thermal changes, and compared with the experimental data available in the literature. An excellent agreement is found for frequencies smaller than about 1.3 times the natural frequency of the bubbles, but the discrepancy is substantial at larger frequencies.