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Sample records for acoustic tiltedti media

  1. Finite Difference Modeling of Wave Progpagation in Acoustic TiltedTI Media

    SciTech Connect

    Zhang, Linbin; Rector III, James W.; Hoversten, G. Michael

    2005-03-21

    Based on an acoustic assumption (shear wave velocity is zero) and a dispersion relation, we derive an acoustic wave equation for P-waves in tilted transversely isotropic (TTI) media (transversely isotropic media with a tilted symmetry axis). This equation has fewer parameters than an elastic wave equation in TTI media and yields an accurate description of P-wave traveltimes and spreading-related attenuation. Our TTI acoustic wave equation is a fourth-order equation in time and space. We demonstrate that the acoustic approximation allows the presence of shear waves in the solution. The substantial differences in traveltime and amplitude between data created using VTI and TTI assumptions is illustrated in examples.

  2. ACOUSTIC RECTIFICATION IN DISPERSIVE MEDIA

    SciTech Connect

    Cantrell, John H.

    2009-03-03

    It is shown that the shapes of acoustic radiation-induced static strain and displacement pulses (rectified acoustic pulses) are defined locally by the energy density of the generating waveform. Dispersive properties are introduced analytically by assuming that the rectified pulses are functionally dependent on a phase factor that includes both dispersive and nonlinear terms. The dispersion causes an evolutionary change in the shape of the energy density profile that leads to the generation of solitons experimentally observed in fused silica.

  3. Acoustic Rectification in Dispersive Media

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.

    2008-01-01

    It is shown that the shapes of acoustic radiation-induced static strain and displacement pulses (rectified acoustic pulses) are defined locally by the energy density of the generating waveform. Dispersive properties are introduced analytically by assuming that the rectified pulses are functionally dependent on a phase factor that includes both dispersive and nonlinear terms. The dispersion causes an evolutionary change in the shape of the energy density profile that leads to the generation of solitons experimentally observed in fused silica.

  4. Nonlinear acoustics of micro-inhomogeneous media

    NASA Astrophysics Data System (ADS)

    Nazarov, Veniamin E.; Ostrovsky, Lev A.; Soustova, Irina A.; Sutin, Aleksandr M.

    1988-01-01

    Acoustic waves can interact in micro-inhomogeneous media much more intensively than in homogeneous media. This has been repeatedly observed in experiments with ground species, marine sediments, porous materials and metals. This paper considers two models of such media which seem to be applicable to the description of these results. One of them is based on the consideration of nonlinear sound scattering by separate spherical cavities in liquids and solids. The second model is based on the phenomenological stress-deformation relation in solids with microplasticity which often has hysteresis (heritage) properties associated with the micro-inhomogeneities. In metals, for example, it is caused by the movement of dislocations. Different nonlinear effects in such media (harmonic and combination frequency generation, nonlinear, variations of resonance frequency amplitude-dependent losses) are considered. Some results of experiments with metallic resonators supporting the theory developed here are also presented. These mechanisms may determine the nonlinear properties of real soils and rocks summarized in a table given in the paper.

  5. Acoustic field in unsteady moving media

    NASA Technical Reports Server (NTRS)

    Bauer, F.; Maestrello, L.; Ting, L.

    1995-01-01

    In the interaction of an acoustic field with a moving airframe the authors encounter a canonical initial value problem for an acoustic field induced by an unsteady source distribution, q(t,x) with q equivalent to 0 for t less than or equal to 0, in a medium moving with a uniform unsteady velocity U(t)i in the coordinate system x fixed on the airframe. Signals issued from a source point S in the domain of dependence D of an observation point P at time t will arrive at point P more than once corresponding to different retarded times, Tau in the interval (0, t). The number of arrivals is called the multiplicity of the point S. The multiplicity equals 1 if the velocity U remains subsonic and can be greater when U becomes supersonic. For an unsteady uniform flow U(t)i, rules are formulated for defining the smallest number of I subdomains V(sub i) of D with the union of V(sub i) equal to D. Each subdomain has multiplicity 1 and a formula for the corresponding retarded time. The number of subdomains V(sub i) with nonempty intersection is the multiplicity m of the intersection. The multiplicity is at most I. Examples demonstrating these rules are presented for media at accelerating and/or decelerating supersonic speed.

  6. Acoustic Energy Estimates in Inhomogeneous Moving Media

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Farris, Mark

    1999-01-01

    In ducted fan engine noise research, there is a need for defining a simple and easy to use acoustic energy conservation law to help in quantification of noise control techniques. There is a well known conservation law relating acoustic energy and acoustic energy flux in the case of an isentropic irrotational flow. Several different approaches have been taken to generalize this conservation law. For example, Morfey finds an identity by separating out the irrotational part of the perturbed flow. Myers is able to find a series of indentities by observing an algebraic relationship between the basic conservation of energy equation for a background flow and the underlying equations of motion. In an approximate sense, this algebraic relationship is preserved under perturbation. A third approach which seems to have not been pursued in the literature is a result known as Noether's theorem. There is a Lagrangian formulation for the Euler equation of fluid mechanics. Noether's theorem says that any group action that leaves the Lagrangian action invariant leads to a conserved quantity. This presentation will include a survey of current results regarding acoustic energy and preliminary results on the symmetries of the Lagrangian.

  7. Acoustically driven filtration of particulate suspensions in porous media

    NASA Astrophysics Data System (ADS)

    Gupta, Sanjay

    1997-12-01

    A novel method of filtration of liquid suspensions containing micron to millimeter size particles has been developed. A resonant ultrasonic field, applied across a highly porous medium, has been used to trap fine particles inside the large pores (relative to the particle size) of the medium. Three types of porous media, unconsolidated bed of 3 mm glass beads, consolidated open pore aluminum mesh, and reticulated polyester polyurethane foam were investigated as the test media. Reasonable filtration efficiencies were achieved for model aqueous suspensions of 325 mesh polystyrene particles in all three porous media. The expected trends of filtration performance with respect to suspension flow rate, its concentration, and the acoustic field intensity were confirmed. The Filtration phenomena was found to be limited by non-physical saturation of porous media. At saturation, the particles collected inside the media were found to exhibit macroscopic vibrations which allows them to escape with the carrier fluid. The highly porous POLY foam (95% porosity) was found to be the best media for suspension studied in terms of the duration of particle retention and percentage filtration efficiencies. The aluminum mesh performed slightly poorer. The unconsolidated porous media collected the least amount of solids. A simple theoretical development based on particle trajectory around an infinitely long cylindrical fiber, in the presence of acoustic field, has been initiated. In principle, the new filtration method is similar to high gravity magnetic separation but the acoustic method has a wider scope due to inherent acoustic contrast present in most suspensions. The low pressure drop, ease of operation, amenability to large scale operation and reasonable filtration efficiency make the new method highly attractive and suitable for practical applications.

  8. Acoustic invisibility cloaks of arbitrary shapes for complex background media

    NASA Astrophysics Data System (ADS)

    Zhu, Jian; Chen, Tianning; Liang, Qingxuan; Wang, Xiaopeng; Xiong, Jie; Jiang, Ping

    2016-04-01

    We report on the theoretical investigation of the acoustic cloaks working in complex background media in this paper. The constitutive parameters of arbitrary-shape cloaks are derived based on the transformation acoustic theory and coordinate transformation technique. The detailed analysis of boundaries conditions and potential applications of the cloaks are also presented in our work. To overcome the difficulty of achieving the materials with ideal parameters in nature, concentric alternating layered isotropic materials is adopted to approximate the required properties of the cloak. Theoretical design and excellent invisibility are demonstrated by numerical simulations. The inhomogeneous medium and arbitrary-shape acoustic cloaks grow closer to real application and may be a new hot spot in future.

  9. A unidirectional acoustic cloak for multilayered background media with homogeneous metamaterials

    NASA Astrophysics Data System (ADS)

    Zhu, Jian; Chen, Tianning; Liang, Qingxuan; Wang, Xiaopeng; Xiong, Jie; Jiang, Ping

    2015-08-01

    The acoustic cloak, which can make an object hard to detect acoustically in a homogeneous background, has attracted great attention from researchers in recent years. The inhomogeneous background media were considered in this paper. The relative constitutive parameters were derived for acoustic cloaks working in multilayered media. And a unidirectional acoustic cloak for layered background media was proposed, designed and implemented successfully in a wide frequency range. In water and NaCl aqueous solution, the acoustic cloak was designed and realized with homogeneous metamaterials which were composed of steel and porous materials. The effective parameters of the unit cells of the cloak were determined by using the effective medium theory. Numerical results demonstrated excellent cloaking performance and showed that such a device could be physically realized with natural materials which will greatly promote the real applications of an invisibility cloak in inhomogeneous backgrounds.

  10. Measurement of the Acoustic Nonlinearity Parameter for Biological Media.

    NASA Astrophysics Data System (ADS)

    Cobb, Wesley Nelson

    In vitro measurements of the acoustic nonlinearity parameter are presented for several biological media. With these measurements it is possible to predict the distortion of a finite amplitude wave in biological tissues of current diagnostic and research interest. The measurement method is based on the finite amplitude distortion of a sine wave that is emmitted by a piston source. The growth of the second harmonic component of this wave is measured by a piston receiver which is coaxial with and has the same size as the source. The experimental measurements and theory are compared in order to determine the nonlinearity parameter. The density, sound speed, and attenuation for the medium are determined in order to make this comparison. The theory developed for this study accounts for the influence of both diffraction and attenuation on the experimental measurements. The effects of dispersion, tissue inhomogeneity and gas bubbles within the excised tissues are studied. To test the measurement method, experimental results are compared with established values for the nonlinearity parameter of distilled water, ethylene glycol and glycerol. The agreement between these values suggests that the measurement uncertainty is (+OR-) 5% for liquids and (+OR-) 10% for solid tissues. Measurements are presented for dog blood and bovine serum albumen as a function of concentration. The nonlinearity parameters for liver, kidney and spleen are reported for both human and canine tissues. The values for the fresh tissues displayed little variation (6.8 to 7.8). Measurements for fixed, normal and cirrhotic tissues indicated that the nonlinearity parameter does not depend strongly on pathology. However, the values for fixed tissues were somewhat higher than those of the fresh tissues.

  11. Laser-speckle-visibility acoustic spectroscopy in soft turbid media

    NASA Astrophysics Data System (ADS)

    Wintzenrieth, Frédéric; Cohen-Addad, Sylvie; Le Merrer, Marie; Höhler, Reinhard

    2014-01-01

    We image the evolution in space and time of an acoustic wave propagating along the surface of turbid soft matter by shining coherent light on the sample. The wave locally modulates the speckle interference pattern of the backscattered light, which is recorded using a camera. We show both experimentally and theoretically how the temporal and spatial correlations in this pattern can be analyzed to obtain the acoustic wavelength and attenuation length. The technique is validated using shear waves propagating in aqueous foam. It may be applied to other kinds of acoustic waves in different forms of turbid soft matter such as biological tissues, pastes, or concentrated emulsions.

  12. Laser speckle visibility acoustic spectroscopy in soft turbid media

    NASA Astrophysics Data System (ADS)

    Wintzenrieth, Frédéric; Cohen-Addad, Sylvie; Le Merrer, Marie; Höhler, Reinhard

    2014-03-01

    We image the evolution in space and time of an acoustic wave propagating along the surface of turbid soft matter by shining coherent light on the sample. The wave locally modulates the speckle interference pattern of the backscattered light and the speckle visibility[2] is recorded using a camera. We show both experimentally and theoretically how the temporal and spatial correlations in this pattern can be analyzed to obtain the acoustic wavelength and attenuation length. The technique is validated using shear waves propagating in aqueous foam.[3] It may be applied to other kinds of acoustic wave in different forms of turbid soft matter, such as biological tissues, pastes or concentrated emulsions. Now at Université Lyon 1 (ILM).

  13. Focused optical and acoustic beams in media with nonlinear absorption

    NASA Astrophysics Data System (ADS)

    Rudenko, O. V.; Sukhorukov, A. A.

    1996-11-01

    Optical and acoustic beams are known to be useful for medical and biological applications, such as diagnostics, surgery, etc. At high intensities both nonlinear lens effects and nonlinear absorption can be significant for the beams. The nonlinear absorption arises due to two-photon optical processes or acoustic shock wave formation. The present work is devoted to the theoretical description of nonlinear beam propagation and focal spot formation taking into account the competition between focusing, diffraction and absorption. We derived a new nonlinear integro- differential equation describing the spatial evolution of the beam width. The general analytical solution of this equation is obtained for arbitrary boundary conditions. The simple formulas are derived for the angle divergence in the far field, as well as for beam width at nonlinear waist. The results of the analysis of these key parameters in different situations are presented.

  14. Acoustic Wave Monitoring of Biofilm Development in Porous Media

    EPA Science Inventory

    Biofilm development in porous media can result in significant changes to the hydrogeological properties of subsurface systems with implications for fluid flow and contaminant transport. As such, a number of numerical models and simulations have been developed in an attempt to qua...

  15. One-way acoustic mirror based on anisotropic zero-index media

    SciTech Connect

    Gu, Zhong-ming; Liang, Bin E-mail: jccheng@nju.edu.cn; Yang, Jing; Cheng, Jian-chun E-mail: jccheng@nju.edu.cn; Zou, Xin-ye; Li, Yong; Yang, Jun

    2015-11-23

    We have designed a one-way acoustic mirror comprising anisotropic zero-index media. For acoustic beam incident at a particular angle, the designed structure behaves like a high-efficient mirror that redirects almost all the incident energy into another direction predicted by the Snell's law, while becoming virtually transparent to beams propagating reversely along this output path. Furthermore, the mirror can be tailored to work at arbitrary incident angle by simply adjusting its geometry. Our design, with undirectional reflection functionality and flexible working angle, may offer possibilities in space isolations and have deep implication in various scenarios like ultrasound imaging or noise control.

  16. Acoustic emissions (AE) during failure of granular media

    NASA Astrophysics Data System (ADS)

    Michlmayr, Gernot; Or, Dani

    2014-05-01

    The release of shallow landslides and other geological mass movements is the result of progressive failure accumulation. Mechanical failure in disordered geologic materials occurs in intermittent breakage episodes marking the disintegration or rearrangement of load-bearing elements. Abrupt strain energy release in such breakage episodes is associated with generation of elastic waves measurable as high-frequency (kHz range) acoustic emissions (AE). The close association of AE with progressive failure events hold a promise for using such noninvasive methods to assess the mechanical state of granular Earth materials or for the development early warning methods for shallow landslides. We present numerical simulations that incorporate damage accumulation and associated stress redistribution using a fiber-bundle model. The stress released from element failure (fibers) is redistributed to the surrounding elements and eventually triggers larger failure avalanches. AE signals generated from such events and eventually hitting a virtual sensor are modeled using visco-elastic wave propagation laws. The model captures the characteristic saw-tooth shape of the observed stress-strain curves obtained from strain-controlled experiments with glass beads, including large intermittent stress release events that stem from cascading failure avalanches. The model also reproduces characteristics of AE signatures and yield a good agreement between simulation results and experimental data. Linking mechanical and AE information in the proposed modeling framework offer a solid basis for interpretation of measured field data.

  17. Acoustical determination of the parameters governing thermal dissipation in porous media.

    PubMed

    Olny, Xavier; Panneton, Raymond

    2008-02-01

    In this paper, the question of the acoustical determination of macroscopic thermal parameters used to describe heat exchanges in rigid open-cell porous media subjected to acoustical excitations is addressed. The proposed method is based on the measurement of the dynamic bulk modulus of the material, and analytical inverse solutions derived from different semiphenomenological models governing the thermal dissipation of acoustic waves in the material. Three models are considered: (1) Champoux-Allard model [J. Appl. Phys. 20, 1975-1979 (1991)] requiring knowledge of the porosity and thermal characteristic length, (2) Lafarge et al. model [J. Acoust. Soc. Am. 102, 1995-2006 (1997)] using the same parameters and the thermal permeability, and (3) Wilson model [J. Acoust. Soc. Am. 94, 1136-1145 (1993)] that requires two adjusted parameters. Except for the porosity that is obtained from direct measurement, all the other thermal parameters are derived from the analytical inversion of the models. The method is applied to three porous materials-a foam, a glass wool, and a rock wool-with very different thermal properties. It is shown that the method can be used to assess the validity of the descriptive models for a given material. PMID:18247886

  18. The effects of fracture permeability on acoustic wave propagation in the porous media: A microscopic perspective.

    PubMed

    Wang, Ding; Wang, Liji; Ding, Pinbo

    2016-08-01

    An illustrative theory is developed to analyze the acoustic wave propagation characteristics in the porous media with anisotropic permeability. We focus here on the role of fracture permeability in the unconsolidated porous media, looking in particular at the compressional P-wave phase velocity and attenuation. Two fluid pressure equilibration characteristic time factors are defined, which are corresponding to crack-pore system and crack-crack system, respectively. The theoretical results show that the dispersion and attenuation characteristics of acoustic wave are affected by porous matrix and fracture permeability simultaneously. Due to the fluid exchange that takes place between fractures and pores dominantly, the influence of the fracture connectivity on the wave propagation is very weak when the permeability of background medium is relatively high. However, correlation between wave propagation and fracture permeability is significant when the matrix permeability at a low level. A second attenuation peak occurs for the fluid flow within fractures in high-frequency region for more and more higher fracture permeability. The exact analytical solutions that are compared to numerical forward modeling of wave propagation in fractured media allow us to verify the correctness of the new model. If there exists another approach for obtaining the connectivity information of background media, we can use this model to analyze qualitatively the permeability of fractures or afford an indicator of in-situ permeability changes in a oil reservoir, for example, fracturing operations. PMID:27259119

  19. Laplace-domain waveform modeling and inversion for the 3D acoustic-elastic coupled media

    NASA Astrophysics Data System (ADS)

    Shin, Jungkyun; Shin, Changsoo; Calandra, Henri

    2016-06-01

    Laplace-domain waveform inversion reconstructs long-wavelength subsurface models by using the zero-frequency component of damped seismic signals. Despite the computational advantages of Laplace-domain waveform inversion over conventional frequency-domain waveform inversion, an acoustic assumption and an iterative matrix solver have been used to invert 3D marine datasets to mitigate the intensive computing cost. In this study, we develop a Laplace-domain waveform modeling and inversion algorithm for 3D acoustic-elastic coupled media by using a parallel sparse direct solver library (MUltifrontal Massively Parallel Solver, MUMPS). We precisely simulate a real marine environment by coupling the 3D acoustic and elastic wave equations with the proper boundary condition at the fluid-solid interface. In addition, we can extract the elastic properties of the Earth below the sea bottom from the recorded acoustic pressure datasets. As a matrix solver, the parallel sparse direct solver is used to factorize the non-symmetric impedance matrix in a distributed memory architecture and rapidly solve the wave field for a number of shots by using the lower and upper matrix factors. Using both synthetic datasets and real datasets obtained by a 3D wide azimuth survey, the long-wavelength component of the P-wave and S-wave velocity models is reconstructed and the proposed modeling and inversion algorithm are verified. A cluster of 80 CPU cores is used for this study.

  20. Codetection of acoustic emissions during failure of heterogeneous media: New perspectives for natural hazard early warning

    NASA Astrophysics Data System (ADS)

    Faillettaz, Jerome; Or, Dani; Reiweger, Ingrid

    2016-02-01

    A simple method for real-time early warning of gravity-driven rupture that considers both the heterogeneity of natural media and characteristics of acoustic emissions attenuation is proposed. The method capitalizes on codetection of elastic waves emanating from microcracks by multiple and spatially separated sensors. Event codetection is considered as surrogate for large event size with more frequent codetected events marking imminence of catastrophic failure. Using a spatially explicit fiber bundle numerical model with spatially correlated mechanical strength and two load redistribution rules, we constructed a range of mechanical failure scenarios and associated failure events (mapped into acoustic emission) in space and time. Analysis considering hypothetical arrays of sensors and consideration of signal attenuation demonstrate the potential of the codetection principles even for insensitive sensors to provide early warning for imminent global failure.

  1. Dispersion and attenuation of acoustic guided waves in layered fluid-filled porous media

    SciTech Connect

    Parra, J.O.; Xu, P. )

    1994-01-01

    The analysis of acoustic wave propagation in fluid-filled porous media based on Biot and homogenization theories has been adapted to calculate dispersion and attenuation of guided waves trapped in low-velocity layered media. Constitutive relations, the balance equation, and the generalized Darcy law of the modified Biot theory yield a coupled system of differential equations which governs the wave motion in each layer. The displacement and stress fields satisfy the boundary conditions of continuity of displacements and tractions across each interface, and the radiation condition at infinity. To avoid precision problems caused by the growing exponential in individual matrices for large wave numbers, the global matrix method was implemented as an alternative to the traditional propagation approach to determine the periodic equations. The complex wave numbers of the guided wave modes were determined using a combination of two-dimensional bracketing and minimization techniques. The results of this work indicate that the acoustic guided wave attenuation is sensitive to the [ital in] [ital situ] permeability. In particular, the attenuation changes significantly as the [ital in] [ital situ] permeability of the low-velocity layer is varied at the frequency corresponding to the minimum group velocity (Airy phase). Alternatively, the attenuation of the wave modes are practically unaffected by those permeability variations in the layer at the frequency corresponding to the maximum group velocity.

  2. Scattering reduction for an acoustic sensor using a multilayered shell comprising a pair of homogeneous isotropic single-negative media

    NASA Astrophysics Data System (ADS)

    Xu, Tao; Zhu, Xue-Feng; Liang, Bin; Li, Yong; Zou, Xin-Ye; Cheng, Jian-Chun

    2012-07-01

    We have designed a cylindrical multilayered structure to reduce scattering for an acoustic sensor while allowing it to receive external information. The proposed structure consists of two alternately arranged complementary media with homogeneous isotropic single-negative parameters. Numerical results show that the acoustic scattering from the sensor is suppressed considerably when the number of bilayers is large enough and the thickness of each bilayer is much smaller than the incident wavelength. This may be particularly significant for practical applications where acoustic measurements would otherwise be disturbed by the insertion of sensors.

  3. A high-order discontinuous Galerkin method for wave propagation through coupled elastic-acoustic media

    SciTech Connect

    Wilcox, Lucas C.; Stadler, Georg; Burstedde, Carsten; Ghattas, Omar

    2010-12-10

    We introduce a high-order discontinuous Galerkin (dG) scheme for the numerical solution of three-dimensional (3D) wave propagation problems in coupled elastic-acoustic media. A velocity-strain formulation is used, which allows for the solution of the acoustic and elastic wave equations within the same unified framework. Careful attention is directed at the derivation of a numerical flux that preserves high-order accuracy in the presence of material discontinuities, including elastic-acoustic interfaces. Explicit expressions for the 3D upwind numerical flux, derived as an exact solution for the relevant Riemann problem, are provided. The method supports h-non-conforming meshes, which are particularly effective at allowing local adaptation of the mesh size to resolve strong contrasts in the local wavelength, as well as dynamic adaptivity to track solution features. The use of high-order elements controls numerical dispersion, enabling propagation over many wave periods. We prove consistency and stability of the proposed dG scheme. To study the numerical accuracy and convergence of the proposed method, we compare against analytical solutions for wave propagation problems with interfaces, including Rayleigh, Lamb, Scholte, and Stoneley waves as well as plane waves impinging on an elastic-acoustic interface. Spectral rates of convergence are demonstrated for these problems, which include a non-conforming mesh case. Finally, we present scalability results for a parallel implementation of the proposed high-order dG scheme for large-scale seismic wave propagation in a simplified earth model, demonstrating high parallel efficiency for strong scaling to the full size of the Jaguar Cray XT5 supercomputer.

  4. A high-order discontinuous Galerkin method for wave propagation through coupled elastic-acoustic media

    NASA Astrophysics Data System (ADS)

    Wilcox, Lucas C.; Stadler, Georg; Burstedde, Carsten; Ghattas, Omar

    2010-12-01

    We introduce a high-order discontinuous Galerkin (dG) scheme for the numerical solution of three-dimensional (3D) wave propagation problems in coupled elastic-acoustic media. A velocity-strain formulation is used, which allows for the solution of the acoustic and elastic wave equations within the same unified framework. Careful attention is directed at the derivation of a numerical flux that preserves high-order accuracy in the presence of material discontinuities, including elastic-acoustic interfaces. Explicit expressions for the 3D upwind numerical flux, derived as an exact solution for the relevant Riemann problem, are provided. The method supports h-non-conforming meshes, which are particularly effective at allowing local adaptation of the mesh size to resolve strong contrasts in the local wavelength, as well as dynamic adaptivity to track solution features. The use of high-order elements controls numerical dispersion, enabling propagation over many wave periods. We prove consistency and stability of the proposed dG scheme. To study the numerical accuracy and convergence of the proposed method, we compare against analytical solutions for wave propagation problems with interfaces, including Rayleigh, Lamb, Scholte, and Stoneley waves as well as plane waves impinging on an elastic-acoustic interface. Spectral rates of convergence are demonstrated for these problems, which include a non-conforming mesh case. Finally, we present scalability results for a parallel implementation of the proposed high-order dG scheme for large-scale seismic wave propagation in a simplified earth model, demonstrating high parallel efficiency for strong scaling to the full size of the Jaguar Cray XT5 supercomputer.

  5. Acoustic Effects on Colloid/Surface Interactions and Porous-Media Permeability

    NASA Astrophysics Data System (ADS)

    Roberts, P. M.; Abdel-Fattah, A. I.; Duran, J.

    2004-12-01

    Acoustic and seismic waves have been observed to influence porous fluid-flow behavior in the Earth and geomaterials over a wide range of scale lengths (microns to kilometers). Examples include oil reservoir production increases induced by seismic (1 to 500 Hz) waves, and mobilizing colloidal clays in sandstone cores by ultrasonic (10 to 50 kHz) energy. The effects of stress-wave propagation on both colloid electrokinetics and fluid-flow dynamics in porous media are not understood. In particular, the coupling of acoustic and seismic waves with colloid behavior is an important mechanism to understand because the distribution of colloids in a porous medium will directly affect its permeability. Recent experimental observations indicate that very-high-frequency (0.5 to 5 MHz) acoustic energy can induce attachment and detachment of micron-size colloids at solid surfaces. Using a microscopic, video image-processing system focused on a glass flow-visualization cell, the behavior of 0.5- to 3-micron diameter polystyrene spheres suspended in 0 to 0.1 M aqueous solution was observed. Initial image-processing-based analysis of acoustically-induced colloid/surface detachment events indicates that very-high-frequency acoustics not only increases particle detachment, but may also permanently "deactivate" colloid attachment (or "active") sites on the glass cell surface. The ability of acoustics to attach or detach colloids also appears to depend on the colloid size and ionic strength of the suspending solution. Other experiments show that seismic-band (1 to 1000 Hz) mechanical stress oscillations can change the permeability of centimeter-size sandstone cores due to mobilization of micron-size colloids contained in the pore space. A unique core-holder apparatus that mechanically strains 2.54-cm-diameter porous rock samples during constant-rate fluid flow was used for these experiments. During single-phase brine flow through sandstone, axial stress oscillations at 50 Hz mobilized

  6. Dynamic Properties of Tympanic Membrane in a Chinchilla Otitis Media Model Measured With Acoustic Loading.

    PubMed

    Yokell, Zachary; Wang, Xuelin; Gan, Rong Z

    2015-08-01

    Otitis media is the most common infectious disease in young children, which results in changes in the thickness and mechanical properties of the tympanic membrane (TM) and induces hearing loss. However, there are no published data for the dynamic properties of the TM in otitis media ears, and it is unclear how the mechanical property changes are related to TM thickness variation. This paper reports a study of the measurement of the dynamic properties of the TM in a chinchilla acute otitis media (AOM) model using acoustic loading and laser Doppler vibrometry (LDV). AOM was created through transbullar injection of Haemophilus influenzae into the middle ear, and AOM samples were prepared 4 days after inoculation. Vibration of the TM specimen induced by acoustic loading was measured via LDV over a frequency range of 0.1-8 kHz. The experiment was then simulated in a finite element (FE) model, and the inverse-problem solving method was used to determine the complex modulus in the frequency domain. Results from 12 ears (six control and six AOM) show that the storage modulus of the TM from AOM ears was on average 53% higher than that of control ears, while the loss factor was 17.3% higher in control ears than in AOM ears at low-frequency (f < 1 kHz). At high-frequency (e.g., 8000 Hz), there was a mean 40% increase in storage modulus of the TM from AOM compared to control samples. At peak frequency (e.g., 3 kHz), there was a 19.5% increase in loss factor in control samples compared to AOM samples. These findings quantify the changes induced by AOM in the chinchilla TM, namely, a significant increase in both the storage and loss moduli. PMID:25902287

  7. Sources and characteristics of acoustic emissions from mechanically stressed geologic granular media — A review

    NASA Astrophysics Data System (ADS)

    Michlmayr, Gernot; Cohen, Denis; Or, Dani

    2012-05-01

    The formation of cracks and emergence of shearing planes and other modes of rapid macroscopic failure in geologic granular media involve numerous grain scale mechanical interactions often generating high frequency (kHz) elastic waves, referred to as acoustic emissions (AE). These acoustic signals have been used primarily for monitoring and characterizing fatigue and progressive failure in engineered systems, with only a few applications concerning geologic granular media reported in the literature. Similar to the monitoring of seismic events preceding an earthquake, AE may offer a means for non-invasive, in-situ, assessment of mechanical precursors associated with imminent landslides or other types of rapid mass movements (debris flows, rock falls, snow avalanches, glacier stick-slip events). Despite diverse applications and potential usefulness, a systematic description of the AE method and its relevance to mechanical processes in Earth sciences is lacking. This review is aimed at providing a sound foundation for linking observed AE with various micro-mechanical failure events in geologic granular materials, not only for monitoring of triggering events preceding mass mobilization, but also as a non-invasive tool in its own right for probing the rich spectrum of mechanical processes at scales ranging from a single grain to a hillslope. We review first studies reporting use of AE for monitoring of failure in various geologic materials, and describe AE generating source mechanisms in mechanically stressed geologic media (e.g., frictional sliding, micro-crackling, particle collisions, rupture of water bridges, etc.) including AE statistical features, such as frequency content and occurrence probabilities. We summarize available AE sensors and measurement principles. The high sampling rates of advanced AE systems enable detection of numerous discrete failure events within a volume and thus provide access to statistical descriptions of progressive collapse of systems

  8. Direct opto-acoustic in vitro measurement of the spatial distribution of laser radiation in biological media

    SciTech Connect

    Pelivanov, Ivan M; Belov, Sergej A; Solomatin, Vladimir S; Khokhlova, Tanya D; Karabutov, Aleksander A

    2006-12-31

    The problem of opto-acoustic (AO) diagnostics of light scattering and absorption in biological media is considered. The objects under study were milk, bovine and porcine liver, and bovine muscle tissue. The forward and backward schemes for recording acoustic signals were used in experiments. The spatial distribution of the light intensity was measured for each biological medium from the temporal profile of the excited OA pulse and the absorption coefficient and reduced scattering coefficient were determined. Opto-acoustic signals were excited by a 1064-nm pulsed Nd:YAG laser and a tunable Ti:sapphire laser at 779 nm. It is shown that the proposed method can be used for obtaining a priori information on a biological medium in problems of optical and AO tomography. (special issue devoted to multiple radiation scattering in random media)

  9. Nonlinear acoustics: Reflection and refraction, scattering of sound by sound, and periodic media

    NASA Astrophysics Data System (ADS)

    Blackstock, David T.

    1988-07-01

    Research on three topics in nonlinear acoustics is described: (1) reflection and refraction at a plane interface between two fluids. Previously a modified form of Snell's law was derived; theoretical work is underway to investigate assumptions on which the derivation was based, (2) scattering of sound by sound. Work on a single beam experiment and a crossed-beams experiment is in progress, and (3) propagation in periodic media. An experiment is being designed to measure finite-amplitude distortion in a plane wave tube loaded periodically with reactive branch elements. Other work, on noncollinear interaction and on biomedical ultrasonics, is described briefly. Two journal articles, five oral papers, and one technical report are listed.

  10. Effects of acoustic waves on stick-slip in granular media and implications for earthquakes

    USGS Publications Warehouse

    Johnson, P.A.; Savage, H.; Knuth, M.; Gomberg, J.; Marone, C.

    2008-01-01

    It remains unknown how the small strains induced by seismic waves can trigger earthquakes at large distances, in some cases thousands of kilometres from the triggering earthquake, with failure often occurring long after the waves have passed. Earthquake nucleation is usually observed to take place at depths of 10-20 km, and so static overburden should be large enough to inhibit triggering by seismic-wave stress perturbations. To understand the physics of dynamic triggering better, as well as the influence of dynamic stressing on earthquake recurrence, we have conducted laboratory studies of stick-slip in granular media with and without applied acoustic vibration. Glass beads were used to simulate granular fault zone material, sheared under constant normal stress, and subject to transient or continuous perturbation by acoustic waves. Here we show that small-magnitude failure events, corresponding to triggered aftershocks, occur when applied sound-wave amplitudes exceed several microstrain. These events are frequently delayed or occur as part of a cascade of small events. Vibrations also cause large slip events to be disrupted in time relative to those without wave perturbation. The effects are observed for many large-event cycles after vibrations cease, indicating a strain memory in the granular material. Dynamic stressing of tectonic faults may play a similar role in determining the complexity of earthquake recurrence. ??2007 Nature Publishing Group.

  11. Effects of acoustic waves on stick-slip in granular media and implications for earthquakes.

    PubMed

    Johnson, Paul A; Savage, Heather; Knuth, Matt; Gomberg, Joan; Marone, Chris

    2008-01-01

    It remains unknown how the small strains induced by seismic waves can trigger earthquakes at large distances, in some cases thousands of kilometres from the triggering earthquake, with failure often occurring long after the waves have passed. Earthquake nucleation is usually observed to take place at depths of 10-20 km, and so static overburden should be large enough to inhibit triggering by seismic-wave stress perturbations. To understand the physics of dynamic triggering better, as well as the influence of dynamic stressing on earthquake recurrence, we have conducted laboratory studies of stick-slip in granular media with and without applied acoustic vibration. Glass beads were used to simulate granular fault zone material, sheared under constant normal stress, and subject to transient or continuous perturbation by acoustic waves. Here we show that small-magnitude failure events, corresponding to triggered aftershocks, occur when applied sound-wave amplitudes exceed several microstrain. These events are frequently delayed or occur as part of a cascade of small events. Vibrations also cause large slip events to be disrupted in time relative to those without wave perturbation. The effects are observed for many large-event cycles after vibrations cease, indicating a strain memory in the granular material. Dynamic stressing of tectonic faults may play a similar role in determining the complexity of earthquake recurrence. PMID:18172496

  12. Acoustics

    NASA Astrophysics Data System (ADS)

    The acoustics research activities of the DLR fluid-mechanics department (Forschungsbereich Stroemungsmechanik) during 1988 are surveyed and illustrated with extensive diagrams, drawings, graphs, and photographs. Particular attention is given to studies of helicopter rotor noise (high-speed impulsive noise, blade/vortex interaction noise, and main/tail-rotor interaction noise), propeller noise (temperature, angle-of-attack, and nonuniform-flow effects), noise certification, and industrial acoustics (road-vehicle flow noise and airport noise-control installations).

  13. Full-Wave Iterative Image Reconstruction in Photoacoustic Tomography With Acoustically Inhomogeneous Media

    PubMed Central

    Huang, Chao; Wang, Kun; Nie, Liming; Wang, Lihong V.; Anastasio, Mark A.

    2014-01-01

    Existing approaches to image reconstruction in photoacoustic computed tomography (PACT) with acoustically heterogeneous media are limited to weakly varying media, are computationally burdensome, and/or cannot effectively mitigate the effects of measurement data incompleteness and noise. In this work, we develop and investigate a discrete imaging model for PACT that is based on the exact photoacoustic (PA) wave equation and facilitates the circumvention of these limitations. A key contribution of the work is the establishment of a procedure to implement a matched forward and backprojection operator pair associated with the discrete imaging model, which permits application of a wide-range of modern image reconstruction algorithms that can mitigate the effects of data incompleteness and noise. The forward and backprojection operators are based on the k-space pseudospectral method for computing numerical solutions to the PA wave equation in the time domain. The developed reconstruction methodology is investigated by use of both computer-simulated and experimental PACT measurement data. PMID:23529196

  14. Stability analysis for acoustic wave propagation in tilted TI media by finite differences

    NASA Astrophysics Data System (ADS)

    Bakker, Peter M.; Duveneck, Eric

    2011-05-01

    Several papers in recent years have reported instabilities in P-wave modelling, based on an acoustic approximation, for inhomogeneous transversely isotropic media with tilted symmetry axis (TTI media). In particular, instabilities tend to occur if the axis of symmetry varies rapidly in combination with strong contrasts of medium parameters, which is typically the case at the foot of a steeply dipping salt flank. In a recent paper, we have proposed and demonstrated a P-wave modelling approach for TTI media, based on rotated stress and strain tensors, in which the wave equations reduce to a coupled set of two second-order partial differential equations for two scalar stress components: a normal component along the variable axis of symmetry and a lateral component of stress in the plane perpendicular to that axis. Spatially constant density is assumed in this approach. A numerical discretization scheme was proposed which uses discrete second-derivative operators for the non-mixed second-order derivatives in the wave equations, and combined first-derivative operators for the mixed second-order derivatives. This paper provides a complete and rigorous stability analysis, assuming a uniformly sampled grid. Although the spatial discretization operator for the TTI acoustic wave equation is not self-adjoint, this operator still defines a complete basis of eigenfunctions of the solution space, provided that the solution space is somewhat restricted at locations where the medium is elliptically anisotropic. First, a stability analysis is given for a discretization scheme, which is purely based on first-derivative operators. It is shown that the coefficients of the central difference operators should satisfy certain conditions. In view of numerical artefacts, such a discretization scheme is not attractive, and the non-mixed second-order derivatives of the wave equation are discretized directly by second-derivative operators. It is shown that this modification preserves

  15. Acoustics

    NASA Technical Reports Server (NTRS)

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

  16. Laser-Doppler acoustic probing of granular media with in-depth property gradient and varying pore pressures

    SciTech Connect

    Bodet, L.; Dhemaied, A.; Mourgues, R.; Tournat, V.; Rejiba, F.

    2012-05-24

    Non-contacting ultrasonic techniques recently proved to be efficient in the physical modeling of seismic-wave propagation at various application scales, as for instance in the context of geological analogue and seismic modeling. An innovative experimental set-up is proposed here to perform laser-Doppler acoustic probing of unconsolidated granular media with varying pore pressures. The preliminary experiments presented here provide reproducible results and exploitable data, thus validating both the proposed medium preparation and pressure gradient generation procedure.

  17. Acoustic wave propagation in heterogeneous two-dimensional fractured porous media

    NASA Astrophysics Data System (ADS)

    Hamzehpour, Hossein; Asgari, Mojgan; Sahimi, Muhammad

    2016-06-01

    This paper addresses an important fundamental question: the differences between wave propagation in fractured porous media with a uniform matrix (constant bulk modulus) and those in which the matrix is heterogeneous with its bulk modulus distributed spatially. The analysis of extensive experimental data [Phys. Rev. E 71, 046301 (2005), 10.1103/PhysRevE.71.046301] indicated that such distributions are self-affine and induce correlations at all the relevant length scales. The comparison is important from a practical view point because in many of the traditional models of fractured rock, particularly those that are used to study wave propagation or fit some data, the matrix is assumed to be uniform. Using extensive numerical simulation of propagation of acoustic waves, we present strong evidence indicating that the waves' amplitude in a fractured porous medium with a heterogeneous matrix decays exponentially with the distance from the source. This is in sharp contrast with a fractured porous medium with a uniform matrix in which not only the waves' amplitude decays with the distance as a stretched exponential function, but the exponent that characterizes the function is also dependent upon the fracture density. The localization length depends on the correlations in the spatial distribution of the bulk modulus, as well as the fracture density. The mean speed of the waves varies linearly with the fractures' mean orientation.

  18. Acoustic wave propagation in heterogeneous two-dimensional fractured porous media.

    PubMed

    Hamzehpour, Hossein; Asgari, Mojgan; Sahimi, Muhammad

    2016-06-01

    This paper addresses an important fundamental question: the differences between wave propagation in fractured porous media with a uniform matrix (constant bulk modulus) and those in which the matrix is heterogeneous with its bulk modulus distributed spatially. The analysis of extensive experimental data [Phys. Rev. E 71, 046301 (2005)PLEEE81539-375510.1103/PhysRevE.71.046301] indicated that such distributions are self-affine and induce correlations at all the relevant length scales. The comparison is important from a practical view point because in many of the traditional models of fractured rock, particularly those that are used to study wave propagation or fit some data, the matrix is assumed to be uniform. Using extensive numerical simulation of propagation of acoustic waves, we present strong evidence indicating that the waves' amplitude in a fractured porous medium with a heterogeneous matrix decays exponentially with the distance from the source. This is in sharp contrast with a fractured porous medium with a uniform matrix in which not only the waves' amplitude decays with the distance as a stretched exponential function, but the exponent that characterizes the function is also dependent upon the fracture density. The localization length depends on the correlations in the spatial distribution of the bulk modulus, as well as the fracture density. The mean speed of the waves varies linearly with the fractures' mean orientation. PMID:27415385

  19. Representation theorems and Green's function retrieval for scattering in acoustic media.

    PubMed

    Vasconcelos, Ivan; Snieder, Roel; Douma, Huub

    2009-09-01

    Reciprocity theorems for perturbed acoustic media are provided in the form of convolution- and correlation-type theorems. These reciprocity relations are particularly useful in the general treatment of both forward and inverse-scattering problems. Using Green's functions to describe perturbed and unperturbed waves in two distinct wave states, representation theorems for scattered waves are derived from the reciprocity relations. While the convolution-type theorems can be manipulated to obtain scattering integrals that are analogous to the Lippmann-Schwinger equation, the correlation-type theorems can be used to retrieve the scattering response of the medium by cross correlations. Unlike previous formulations of Green's function retrieval, the extraction of scattered-wave responses by cross correlations does not require energy equipartitioning. Allowing for uneven energy radiation brings experimental advantages to the retrieval of fields scattered by remote lossless and/or attenuative scatterers. These concepts are illustrated with a number of examples, including analytic solutions to a one-dimensional scattering problem, and a numerical example in the context of seismic waves recorded on the ocean bottom. PMID:19905236

  20. Can trained nurses exclude acute otitis media with tympanometry or acoustic reflectometry in symptomatic children?

    PubMed Central

    Tähtinen, Paula A.; Ruuskanen, Olli; Löyttyniemi, Eliisa; Ruohola, Aino

    2015-01-01

    Objective Since acute otitis media (AOM) is the most prevalent bacterial infection in young children, the reliable exclusion of AOM by nurses might save physicians’ time for other duties. The study aim was to determine whether nurses without otoscopic experience can reliably use tympanometry or spectral gradient acoustic reflectometry (SG-AR) to exclude AOM. Design Three nurses were trained, who performed examinations with tympanometry and SG-AR. Pneumatic otoscopy by the study physician served as the diagnostic standard. Setting Study clinic at primary health care level. Patients. 281 children 6–35 months of age. Main outcome measures Predictive values (with 95% confidence interval) for tympanometry and SG-AR, and the clinical usefulness, i.e. the proportion of visits where nurses obtained the exclusive test result from both ears of the child. Results At 459 visits, the negative predictive value of type A and C1 tympanograms (tympanometric peak pressure >–200 daPa) was 94% (91–97%). Based on type A and C1 tympanograms, the nurse could exclude AOM at 94/459 (20%) of visits. The negative predictive value of SG-AR level 1 result (>95°) was 94% (89–97%). Based on the SG-AR level 1 result, the nurse could exclude AOM at 36/459 (8%) of visits. Conclusion Type A and C1 tympanograms and SG-AR level 1 results obtained by nurses are reliable test results in excluding AOM. However, the clinical usefulness of these test results is limited by their rarity. Type A and C1 tympanograms were obtained by nurses from both ears of the child only at one-fifth of the symptomatic visits.Key PointsAcute otitis media (AOM) is the most prevalent bacterial infection in young children. Nurses’ role in excluding AOM is unknown.Type A and C1 tympanograms (tympanometric peak pressure >–200 daPa) obtained by nurses are reliable test results in excluding AOM.With type A and C1 tympanograms, nurses could exclude AOM only at one-fifth of the symptomatic visits.The clinical usefulness

  1. Reflection of no equilibrium two Phase Processes of Filtration in heterogeneous Media in the active seism acoustic borehole monitoring Data

    NASA Astrophysics Data System (ADS)

    Hachay, Olga; Dryagin, Veniamin; Igolkina, Galina; Khachay, Oleg

    2013-04-01

    It is provided a comparison of no equilibrium effects by independent hydro dynamical and seism acoustic influence on an oil layer. It is known, that by drainage and steeps the hysteresis effect on curves of the relative phase permeability in dependence from porous medium water saturation by some cycles of influence: drainage-steep-drainage is observed. In earlier papers the analysis of the seism acoustic monitoring data in regimes of phone radiation, response on the first influence of given frequency and on the second influence is developed. For the analysis of seism acoustic response in time on fixed intervals along the borehole an algorithm of phase diagrams of the state of many phase medium is suggested In that paper on the base of developed algorithm a new algorithm of analyze of space, but integral in time for equal observation periods changing by the method of phase diagram state of many phase medium in the oil layer is developed. The paper was supported by the Program of Presidium UB RAS 2012-2014. Key words: Oil and gas deposits, seism acoustic borehole monitoring data, new method of processing, reflection of no equilibrium two phase processes, heterogeneous media.

  2. Microbial-Induced Heterogeneity in the Acoustic Properties of Porous Media

    EPA Science Inventory

    Acoustic wave data were acquired over a two-dimensional region of a microbial-stimulated sand column and an unstimulated sand column to assess the spatiotemporal changes in a porous medium caused by microbial growth and biofilm formation. The acoustic signals from the unstimulate...

  3. Effects of signal attenuation in natural media on interpretation of acoustic emissions in the context early warning systems

    NASA Astrophysics Data System (ADS)

    Faillettaz, Jerome; Or, Dani

    2015-04-01

    Gravity driven instabilities in natural media such as rockfalls, landslides, snow avalanches or glacier break-offs represent a significant class of natural hazards. Reliable prediction of imminence of such events combined with timely evacuation remain a challenge because material failure is a non linear process involving inherent heterogeneities affecting the outcome. Nevertheless, such materials break gradually with the weakest parts breaking first, producing precursory "micro-cracks" and associated elastic waves traveling in the material. The monitoring of such acoustic/micro-seismic activity offers valuable information on the progression of damage and imminence of global failure. The main challenge is that acoustic waves are strongly attenuated during their travel through natural media thereby introducing ambiguity in the interpretation of the magnitude (severity) or leading to loss of detection for faraway events. For example, a micro-crack event would be measured as a large event if occurring close to the sensor, and as a small event if far from the sensor ( or may not be detected at all). A more complete picture of acoustic emissions or micro- seismic activity requires deployment of a dense network of sensors that enables localization of sources and thus the determination of initial energy released with each event. However, such networks are prohibitively costly difficult to analyze in real time over scales of interest. Is it possible to find a way to analyze directly in real time the measured micro-seismic activity to infer the slope mechanical status? Following a qualitative description of the observation problem and the processes leading to attenuation, a quantitative analysis is performed using a numerical model based on the classical Fiber Bundle Model. Introducing a basic attenuation law in such simple models enables to directly compare un-attenuated and attenuated acoustic activity (and also avalanche size-frequency distribution) at any location

  4. A method to determine the acoustic reflection and absorption coefficients of porous media by using modal dispersion in a waveguide.

    PubMed

    Prisutova, Jevgenija; Horoshenkov, Kirill; Groby, Jean-Philippe; Brouard, Bruno

    2014-12-01

    The measurement of acoustic material characteristics using a standard impedance tube method is generally limited to the plane wave regime below the tube cut-on frequency. This implies that the size of the tube and, consequently, the size of the material specimen must remain smaller than a half of the wavelength. This paper presents a method that enables the extension of the frequency range beyond the plane wave regime by at least a factor of 3, so that the size of the material specimen can be much larger than the wavelength. The proposed method is based on measuring of the sound pressure at different axial locations and applying the spatial Fourier transform. A normal mode decomposition approach is used together with an optimization algorithm to minimize the discrepancy between the measured and predicted sound pressure spectra. This allows the frequency and angle dependent reflection and absorption coefficients of the material specimen to be calculated in an extended frequency range. The method has been tested successfully on samples of melamine foam and wood fiber. The measured data are in close agreement with the predictions by the equivalent fluid model for the acoustical properties of porous media. PMID:25480044

  5. Acoustic experimental investigation of interaction femtosecond laser pulses with gas-aerosol media and biological tissues

    NASA Astrophysics Data System (ADS)

    Bochkarev, N. N.; Kabanov, A. M.; Stepanov, A. N.

    2008-02-01

    Using two optical acoustic approaches we experimentally investigated spatial location of filament zone of propagation channel of focused laser radiation. For femtosecond pulses passing in air it was shown that nonlinear focus length had spatial scale of 1/P at initial power P moderate for self-focusing and at optical system focus distance significantly lower than Rayleigh beam length. The results of experimental optical acoustic investigation of femto- and nanosecond pulses attenuation by some biological tissues (muscular tissue, adipose tissue, cutaneous covering, milk) and optical breakdown thresholds on these one are presented. It was shown that penetration depth of short laser pulse radiation into biological tissues is the same as for longer one. However, amplitude of acoustic response to a process of interaction of femtosecond laser pulse with biological tissue is larger in several times than that to interaction with nanosecond pulses of the same power and spectral distribution. The obtained of threshold values can be interesting for tabulation of limit allowable levels of irradiation at work with laser radiation. Such values are unknown for femtosecond laser pulses today.

  6. Mechanisms for Acoustic Absorption in Dry and Weakly Wet Granular Media

    SciTech Connect

    Brunet, Th.; Jia, X.; Mills, P.

    2008-09-26

    The dissipation of an elastic wave in dry and wet glass bead packings is measured using multiple sound scattering. The interplay of a linear viscoelastic loss and a nonlinear frictional one is observed in dry media. The Mindlin model provides a qualitative description of the experiment, but fails to quantitatively account for the data due to grain roughness. In weakly wet media, we find that the dissipation is dominated by a linear viscous loss due to the liquid films trapped at the grain surface asperities. Adding more liquid enables us to form the capillary menisci but does not increase the energy loss.

  7. Time-domain simulation of constitutive relations for nonlinear acoustics including relaxation for frequency power law attenuation media modeling

    NASA Astrophysics Data System (ADS)

    Jiménez, Noé; Camarena, Francisco; Redondo, Javier; Sánchez-Morcillo, Víctor; Konofagou, Elisa E.

    2015-10-01

    We report a numerical method for solving the constitutive relations of nonlinear acoustics, where multiple relaxation processes are included in a generalized formulation that allows the time-domain numerical solution by an explicit finite differences scheme. Thus, the proposed physical model overcomes the limitations of the one-way Khokhlov-Zabolotskaya-Kuznetsov (KZK) type models and, due to the Lagrangian density is implicitly included in the calculation, the proposed method also overcomes the limitations of Westervelt equation in complex configurations for medical ultrasound. In order to model frequency power law attenuation and dispersion, such as observed in biological media, the relaxation parameters are fitted to both exact frequency power law attenuation/dispersion media and also empirically measured attenuation of a variety of tissues that does not fit an exact power law. Finally, a computational technique based on artificial relaxation is included to correct the non-negligible numerical dispersion of the finite difference scheme, and, on the other hand, improve stability trough artificial attenuation when shock waves are present. This technique avoids the use of high-order finite-differences schemes leading to fast calculations. The present algorithm is especially suited for practical configuration where spatial discontinuities are present in the domain (e.g. axisymmetric domains or zero normal velocity boundary conditions in general). The accuracy of the method is discussed by comparing the proposed simulation solutions to one dimensional analytical and k-space numerical solutions.

  8. Hydrodynamic, Heat and Acoustic Processes Modelling in Tranport of Rheologically Complex Viscous Media Technology in Pipelines

    NASA Astrophysics Data System (ADS)

    Kharlamov, Sergey N.; Kudelin, Nikita S.; Dedeyev, Pavel O.

    2014-08-01

    The paper describes the results of mathematical modelling of acoustic processes, hydrodynamics and heat exchange in case of oil products transportation in pipelines with constant and variable cross-section. The turbulence model features of RANS approach and intensification of heat exchange in substances with anomalous rheology are reviewed. It is shown that statistic second order models are appropriate to use for forecasting details of the pulsating flows. The paper states the numerical integration features of determining equations. The properties of vibratory effect influence are determined. Vortex and heat perturbations, rheological changes impact on resistance regularities and intensity of heat exchange are analyzed.

  9. A dynamic pressure view cell for acoustic stimulation of fluids—Micro-bubble generation and fluid movement in porous media

    NASA Astrophysics Data System (ADS)

    Stewart, Robert A.; Shaw, J. M.

    2015-09-01

    The development and baseline operation of an acoustic view cell for observing fluids, and fluid-fluid and fluid-solid interfaces in porous media over the frequency range of 10-5000 Hz is described. This range includes the industrially relevant frequency range 500-5000 Hz that is not covered by existing devices. Pressure waveforms of arbitrary shape are generated in a 17.46 mm ID by 200 mm and 690.5 mm long glass tubes at flow rates up to 200 ml/min using a syringe pump. Peak-to-peak amplitudes exceeding 80 kPa are readily realized at frequencies from 10 to 5000 Hz in bubble free fluids when actuated with 20 Vpp as exemplified using castor oil. At resonant frequencies, peak-to-peak pressure amplitudes exceeding 500 kPa were obtained (castor oil at 2100 Hz when actuated with 20 Vpp). Impacts of vibration on macroscopic liquid-liquid and liquid-vapour interfaces and interface movement are illustrated. Pressure wave transmission and attenuation in a fluid saturated porous medium, randomly packed 250-330 μm spherical silica beads, is also demonstrated. Attenuation differences and frequency shifts in resonant peaks are used to detect the presence and generation of dispersed micro-bubbles (<180 μm diameter), and bubbles within porous media that are not readily visualized. Envisioned applications include assessment of the impacts of vibration on reaction, mass transfer, and flow/flow pattern outcomes. This knowledge will inform laboratory and pilot scale process studies, where nuisance vibrations may affect the interpretation of process outcomes, and large scale or in situ processes in aquifers or hydrocarbon reservoirs where imposed vibration may be deployed to improve aspects of process performance. Future work will include miscible interface observation and quantitative measurements in the bulk and in porous media where the roles of micro-bubbles comprise subjects of special interest.

  10. A dynamic pressure view cell for acoustic stimulation of fluids--Micro-bubble generation and fluid movement in porous media.

    PubMed

    Stewart, Robert A; Shaw, J M

    2015-09-01

    The development and baseline operation of an acoustic view cell for observing fluids, and fluid-fluid and fluid-solid interfaces in porous media over the frequency range of 10-5000 Hz is described. This range includes the industrially relevant frequency range 500-5000 Hz that is not covered by existing devices. Pressure waveforms of arbitrary shape are generated in a 17.46 mm ID by 200 mm and 690.5 mm long glass tubes at flow rates up to 200 ml/min using a syringe pump. Peak-to-peak amplitudes exceeding 80 kPa are readily realized at frequencies from 10 to 5000 Hz in bubble free fluids when actuated with 20 Vpp as exemplified using castor oil. At resonant frequencies, peak-to-peak pressure amplitudes exceeding 500 kPa were obtained (castor oil at 2100 Hz when actuated with 20 Vpp). Impacts of vibration on macroscopic liquid-liquid and liquid-vapour interfaces and interface movement are illustrated. Pressure wave transmission and attenuation in a fluid saturated porous medium, randomly packed 250-330 μm spherical silica beads, is also demonstrated. Attenuation differences and frequency shifts in resonant peaks are used to detect the presence and generation of dispersed micro-bubbles (<180 μm diameter), and bubbles within porous media that are not readily visualized. Envisioned applications include assessment of the impacts of vibration on reaction, mass transfer, and flow/flow pattern outcomes. This knowledge will inform laboratory and pilot scale process studies, where nuisance vibrations may affect the interpretation of process outcomes, and large scale or in situ processes in aquifers or hydrocarbon reservoirs where imposed vibration may be deployed to improve aspects of process performance. Future work will include miscible interface observation and quantitative measurements in the bulk and in porous media where the roles of micro-bubbles comprise subjects of special interest. PMID:26429474

  11. Effects of nonlinearity on the propagation of acoustic pulses in random media

    NASA Astrophysics Data System (ADS)

    Cleveland, Robin; Dallois, Laurent; Blanc-Benon, Philippe

    2002-11-01

    We conducted a numerical investigation into the propagation of finite-amplitude pulses in media with inhomogeneous random sound speed. An N wave (idealized sonic boom) was used as the pulse shape. Initial simulations considered a medium with a single spherical scattering object with a slow sound speed. This object acted as a focusing lens. As the amplitude of the N wave was increased nonlinear effects initially led to enhancement of focusing, reduction in shock risetime, and a shift of the peak away from the object. However, for high amplitude, energy loss at the shock led to a dramatic reduction in the amplitude of the focus and a shift towards the object. Simulations were then carried out in a two-dimensional random media. The sound speed in the random media was constructed using a Fourier mode decomposition with parameters appropriate for turbulence in the atmospheric boundary layer. For low amplitude waves the N wave was focused and defocused by regions of low and high sound speed, respectively. However, the presence of multiple paths means that the wave form no longer resembled an N-wave after propagating about 10 wavelengths. As the amplitude was increased the focusing was enhanced and more localized.

  12. Wave theory of turbulence in compressible media (acoustic theory of turbulence)

    NASA Technical Reports Server (NTRS)

    Kentzer, C. P.

    1975-01-01

    The generation and the transmission of sound in turbulent flows are treated as one of the several aspects of wave propagation in turbulence. Fluid fluctuations are decomposed into orthogonal Fourier components, with five interacting modes of wave propagation: two vorticity modes, one entropy mode, and two acoustic modes. Wave interactions, governed by the inhomogeneous and nonlinear terms of the perturbed Navier-Stokes equations, are modeled by random functions which give the rates of change of wave amplitudes equal to the averaged interaction terms. The statistical framework adopted is a quantum-like formulation in terms of complex distribution functions. The spatial probability distributions are given by the squares of the absolute values of the complex characteristic functions. This formulation results in nonlinear diffusion-type transport equations for the probability densities of the five modes of wave propagation.

  13. Media.

    ERIC Educational Resources Information Center

    Allen, Lee E., Ed.

    1974-01-01

    Intended for secondary English teachers, the materials and ideas presented here suggest ways to use media in the classroom in teaching visual and auditory discrimination while enlivening classes and motivating students. Contents include "Media Specialists Need Not Apply," which discusses the need for preparation of media educators with…

  14. Acoustic probing of elastic behavior and damage in weakly cemented granular media

    NASA Astrophysics Data System (ADS)

    Langlois, V.; Jia, X.

    2014-02-01

    We investigate the elastic behavior and damage of weakly cemented granular media under external load with ultrasound. The cementation controlled experiments are performed by freezing the capillary liquid at the bead contact in a dense glass or polymeric [poly(methyl methacrylate)] bead pack wet by tetradecane of volume fraction ϕ = 0.1%-4%. When the pendular rings are solidified, an abrupt increase by a factor of 2 in the compressional wave velocity is observed. We interpret the data in terms of effective medium models in which the contact stiffnesses are derived by either a bonded contact model [P. J. Digby, J. Appl. Mech. 48, 803 (1981), 10.1115/1.3157738] or a cemented contact model [J. Dvorkin, A. Nur, and H. Yin, Mech. Mater. 18, 351 (1994), 10.1016/0167-6636(94)90044-2]. The former fails to quantitatively account for the results with a soft cement relative to the grain, whereas the latter considering the mechanical properties of the cement does apply. Moreover, we monitor the irreversible behavior of the cemented granular packs under moderate uniaxial loading (<1.3 MPa) with the correlation method of ultrasound scattering. The damage of the cemented materials is accompanied by a compressional wave velocity decrease up to 60%, likely due to the fractures induced at the grain-cement interfaces.

  15. Acoustic probing of elastic behavior and damage in weakly cemented granular media.

    PubMed

    Langlois, V; Jia, X

    2014-02-01

    We investigate the elastic behavior and damage of weakly cemented granular media under external load with ultrasound. The cementation controlled experiments are performed by freezing the capillary liquid at the bead contact in a dense glass or polymeric [poly(methyl methacrylate)] bead pack wet by tetradecane of volume fraction ϕ = 0.1%-4%. When the pendular rings are solidified, an abrupt increase by a factor of 2 in the compressional wave velocity is observed. We interpret the data in terms of effective medium models in which the contact stiffnesses are derived by either a bonded contact model [P. J. Digby, J. Appl. Mech. 48, 803 (1981)] or a cemented contact model [J. Dvorkin, A. Nur, and H. Yin, Mech. Mater. 18, 351 (1994)]. The former fails to quantitatively account for the results with a soft cement relative to the grain, whereas the latter considering the mechanical properties of the cement does apply. Moreover, we monitor the irreversible behavior of the cemented granular packs under moderate uniaxial loading (1.3 MPa) with the correlation method of ultrasound scattering. The damage of the cemented materials is accompanied by a compressional wave velocity decrease up to 60%, likely due to the fractures induced at the grain-cement interfaces. PMID:25353594

  16. [Influence of changed gas media on acoustic parameters of human forced exhalation].

    PubMed

    D'iachenko, A I; Korenbaum, V I; Shulagin, Iu A; Osipova, A A; Mikhaĭlovskaia, A N; Popova, Iu A; Kir'ianova, E V; Kostiv, A E; Mokerova, E S; Shin, S N; Pochekutova, I A

    2012-01-01

    In previous study it was shown that duration of tracheal forced expiratory noises is promising to reveal negative changes of lung function after dive. The objective is a study of parameters of tracheal forced expiratory noises in changed gas media. The first experiment involved 25 volunteers (22-60 years), performed forced exhalation under normal pressure with air, oxygen-helium and oxygen-krypton mixtures. The second experiment in the chamber involved 6 volunteers (25-46 years), which performed forced exhalation with air under normal pressure (0.1 MPa), and under elevated pressure 0.263 MPa with air and oxygen-helium mixture. In the first experiment the direct linear dependence on gas density was found for forced expiratory noises common duration in the band of 200-2000 Hz and for its durations in narrow 200-Hz bands, excluding high frequency range 1400-2000 Hz. In the second experiment a significant reversed dependence of high frequency durations and spectral energies in 200-Hz bands (1600-2000 Hz) on adiabatic gas compressibility. Individual dynamics of common duration of tracheal forced expiratory noises under model dive of 16.3 m (0.263 MPa) is more then the diagnostic threshold of this parameter for lung function decrease, previously obtained for divers under normal pressure. PMID:22567842

  17. High-order Hybridized Discontinuous Galerkin (HDG) method for wave propagation simulation in complex geophysical media (elastic, acoustic and hydro-acoustic); an unifying framework to couple continuous Spectral Element and Discontinuous Galerkin Methods

    NASA Astrophysics Data System (ADS)

    Terrana, Sebastien; Vilotte, Jean-Pierre; Guillot, Laurent; Mariotti, Christian

    2015-04-01

    Today seismological observation systems combine broadband seismic receivers, hydrophones and micro-barometers antenna that provide complementary observations of source-radiated waves in heterogeneous and complex geophysical media. Exploiting these observations requires accurate and multi-physics - elastic, hydro-acoustic, infrasonic - wave simulation methods. A popular approach is the Spectral Element Method (SEM) (Chaljub et al, 2006) which is high-order accurate (low dispersion error), very flexible to parallelization and computationally attractive due to efficient sum factorization technique and diagonal mass matrix. However SEMs suffer from lack of flexibility in handling complex geometry and multi-physics wave propagation. High-order Discontinuous Galerkin Methods (DGMs), i.e. Dumbser et al (2006), Etienne et al. (2010), Wilcox et al (2010), are recent alternatives that can handle complex geometry, space-and-time adaptativity, and allow efficient multi-physics wave coupling at interfaces. However, DGMs are more memory demanding and less computationally attractive than SEMs, especially when explicit time stepping is used. We propose a new class of higher-order Hybridized Discontinuous Galerkin Spectral Elements (HDGSEM) methods for spatial discretization of wave equations, following the unifying framework for hybridization of Cockburn et al (2009) and Nguyen et al (2011), which allows for a single implementation of conforming and non-conforming SEMs. When used with energy conserving explicit time integration schemes, HDGSEM is flexible to handle complex geometry, computationally attractive and has significantly less degrees of freedom than classical DGMs, i.e., the only coupled unknowns are the single-valued numerical traces of the velocity field on the element's faces. The formulation can be extended to model fractional energy loss at interfaces between elastic, acoustic and hydro-acoustic media. Accuracy and performance of the HDGSEM are illustrated and

  18. High-Order Hybridized Discontinuous Galerkin (HDG) Method for Wave Propagation Simulation in Complex Geophysical Media - Elastic, Acoustic and Hydro-Acoustic - an Unifying Framework to Couple Continuous Spectral Element and Discontinuous Galerkin Methods.

    NASA Astrophysics Data System (ADS)

    Sébastien, T.; Vilotte, J. P.; Guillot, L.; Mariotti, C.

    2014-12-01

    Today seismological observation systems combine broadband seismic receivers, hydrophones and micro-barometers antenna that provide complementary observations of source-radiated waves in heterogeneous and complex geophysical media. Exploiting these observations requires accurate and multi-physics - elastic, hydro-acoustic, infrasonic - wave simulation methods. A popular approach is the Spectral Element Method (SEM) (Chaljub et al, 2006) which is high-order accurate (low dispersion error), very flexible to parallelization and computationally attractive due to efficient sum factorization technique and diagonal mass matrix. However SEMs suffer from lack of flexibility in handling complex geometry and multi-physics wave propagation. High-order Discontinuous Galerkin Methods (DGMs), i.e. Dumbser et al (2006), Etienne et al. (2010), Wilcox et al (2010), are recent alternatives that can handle complex geometry, space-and-time adaptativity, and allow efficient multi-physics wave coupling at interfaces. However, DGMs are more memory demanding and less computationally attractive than SEMs, especially when explicit time stepping is used. We propose a new class of higher-order Hybridized Discontinuous Galerkin Spectral Elements (HDGSEM) methods for spatial discretization of wave equations, following the unifying framework for hybridization of Cockburn et al (2009) and Nguyen et al (2011), which allows for a single implementation of conforming and non-conforming SEMs. When used with energy conserving explicit time integration schemes, HDGSEM is flexible to handle complex geometry, computationally attractive and has significantly less degrees of freedom than classical DGMs, i.e., the only coupled unknowns are the single-valued numerical traces of the velocity field on the element's faces. The formulation can be extended to model fractional energy loss at interfaces between elastic, acoustic and hydro-acoustic media. Accuracy and performance of the HDGSEM are illustrated and

  19. The Effects of Acoustic Waves on Stick Slip Behavior in Sheared Granular Media and Their Implications for Earthquake Recurrence and Dynamic Triggering

    NASA Astrophysics Data System (ADS)

    Johnson, P. A.; Marone, C.; Gomberg, J.; Savage, H.; Knuth, M.; Behringer, B.; Carpenter, B.

    2008-12-01

    To better understand the physics of dynamic triggering and the influence of dynamic stressing on earthquake recurrence, we are conducting laboratory studies of stick slip in granular media with and without applied acoustic vibrations. In our 3-D experiments, glass beads are used to simulate granular fault zone wear material, sheared in a double-direct configuration under constant normal stress, while subject to transient or continuous perturbations by acoustic waves. We observe both instantaneous and delayed triggering when vibration is applied. Vibrations also cause significant disruption in the recurrence rate. The effects of vibration are observed for many major-event cycles after vibrations cease, indicating a strain memory in the granular material. Vibration-induced disruption of periodic stick slip is linked to failure of granular force chains. In 2-D experiments we are applying photoelastic discs in stick slip measurements in order to visualize the evolution of the force chain network. Photoelastic measurements provide insight into failure, and in particular small adjustments in the force chains network that presage failure. Our results should lead to a new understanding of the importance of seismic energy on earthquake physics and more generally, we anticipate that it will have broad impact on unexpected material failure induced by moderate-amplitude elastic waves, including avalanches, landslide and failure of incipient damage in solids.

  20. Multiscale analysis of waves reflected by granular media: Acoustic experiments on glass beads and effective medium theories

    NASA Astrophysics Data System (ADS)

    Le Gonidec, Yves; Gibert, Dominique

    2007-05-01

    The wavelet response is a multiscale method based on the continuous wavelet transform. We use it to characterize the acoustic reflectivity of a layer of glass beads with diameter d = 1 mm randomly arranged in water. The volumetric concentration is ϕ ≃ 63% of spherical inclusions. The wavelet response is measured over a large frequency range (100 kHz ≤ f ≤ 5 MHz) where five different acoustic regimes are identified on the basis of scattering phenomena. A strong decrease in the reflectivity occurs when the wavelength of the incident wave is twice the bead diameter, a situation where lateral scattering is dominant. The energy ratio of the ballistic and the coda parts of the wavelet response reveals a clear transition from a ballistic propagation regime to a diffusion regime where multiple scattering occurs. The experimental data are explained with an effective medium theory approach: the reflectivity data in the low-frequency domain of the spanned frequency range are correctly reproduced with quasi-static models. For higher frequencies, more sophisticated models accounting for multiple scattering must be used. The high-frequency part of the experimental reflectivity curve may be explained by strong multiple scattering at the top of the glass beads located at the surface of the layer and corresponds to the optical geometric limit.

  1. The subgrid modeling of propagation of acoustic waves in heterogeneous media with multiscale isotropic random elastic stiffness and density

    NASA Astrophysics Data System (ADS)

    Soboleva, O. N.; Kurochkina, E. P.

    2016-01-01

    The effective coefficients in the problem of the acoustic wave propagation have been calculated for a multiscale 3D isotropic medium using a subgrid modeling approach. The density and the elastic stiffness have been represented mathematically by the Kolmogorov multiplicative cascades, which, to date, appear to be the only mechanisms for generating a stationary multifractal fields with a log-stable probability distribution. The fields with the stable distribution are described with the help of linear combination random values ?, ? and weight coefficients ?, ?, which satisfy certain conditions in the nodes of spatial grid ?. The parameters of the stable distribution of the random values ?, ? are equal: ?, ?, ?, ?. The wavelength is assumed to be large as compared with the scale of heterogeneities of the medium. We consider the regime in which the waves propagate over a distance of the typical wave length in source. The theoretical results obtained in this paper are compared with the results of a direct 3D numerical simulation.

  2. Acoustic neuroma

    MedlinePlus

    Vestibular schwannoma; Tumor - acoustic; Cerebellopontine angle tumor; Angle tumor ... Acoustic neuromas have been linked with the genetic disorder neurofibromatosis type 2 (NF2). Acoustic neuromas are uncommon.

  3. ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Cellular Automaton Simulations for Target Waves in Excitable Media

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Sheng; Deng, Min-Yi; Kong, Ling-Jiang; Liu, Mu-Ren; Tang, Guo-Ning

    2010-01-01

    Using the Greenberg-Hasting cellular automata model, we study the properties of target waves in excitable media under the no-flux boundary conditions. For the system has only one excited state, the computer simulation and analysis lead to the conclusions that, the number of refractory states does not influence the wave-front speed; the wave-front speed decreases as the excitation threshold increases and increases as the neighbor radius increases; the period of target waves is equal to the number of cell states; the excitation condition for target waves is that the wave-front speed must be bigger than half of the neighbor radius.

  4. Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

    NASA Astrophysics Data System (ADS)

    Ambroziński, Łukasz; Pelivanov, Ivan; Song, Shaozhen; Yoon, Soon Joon; Li, David; Gao, Liang; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew

    2016-07-01

    A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phase-sensitive (PhS)-optical coherence tomography system is used to track/image the mechanical wave. The reconstructed transient displacement of the mechanical wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements in delicate soft tissues and organs in bio-medicine, in particular.

  5. Seismic inversion with generalized Radon transform based on local second-order approximation of scattered field in acoustic media

    NASA Astrophysics Data System (ADS)

    Ouyang, Wei; Mao, Weijian; Li, Xuelei; Li, Wuqun

    2014-08-01

    Sound velocity inversion problem based on scattering theory is formulated in terms of a nonlinear integral equation associated with scattered field. Because of its nonlinearity, in practice, linearization algorisms (Born/single scattering approximation) are widely used to obtain an approximate inversion solution. However, the linearized strategy is not congruent with seismic wave propagation mechanics in strong perturbation (heterogeneous) medium. In order to partially dispense with the weak perturbation assumption of the Born approximation, we present a new approach from the following two steps: firstly, to handle the forward scattering by taking into account the second-order Born approximation, which is related to generalized Radon transform (GRT) about quadratic scattering potential; then to derive a nonlinear quadratic inversion formula by resorting to inverse GRT. In our formulation, there is a significant quadratic term regarding scattering potential, and it can provide an amplitude correction for inversion results beyond standard linear inversion. The numerical experiments demonstrate that the linear single scattering inversion is only good in amplitude for relative velocity perturbation () of background media up to 10 %, and its inversion errors are unacceptable for the perturbation beyond 10 %. In contrast, the quadratic inversion can give more accurate amplitude-preserved recovery for the perturbation up to 40 %. Our inversion scheme is able to manage double scattering effects by estimating a transmission factor from an integral over a small area, and therefore, only a small portion of computational time is added to the original linear migration/inversion process.

  6. Modeling and analysis of multiple scattering of acoustic waves in complex media: application to the trabecular bone.

    PubMed

    Wojcik, J; Litniewski, J; Nowicki, A

    2011-10-01

    The integral equations that describe scattering in the media with step-rise changing parameters have been numerically solved for the trabecular bone model. The model consists of several hundred discrete randomly distributed elements. The spectral distribution of scattering coefficients in subsequent orders of scattering has been presented. Calculations were carried on for the ultrasonic frequency ranging from 0.5 to 3 MHz. Evaluation of the contribution of the first, second, and higher scattering orders to total scattering of the ultrasounds in trabecular bone was done. Contrary to the approaches that use the μCT images of trabecular structure to modeling of the ultrasonic wave propagation condition, the 3D numerical model consisting of cylindrical elements mimicking the spatial matrix of trabeculae, was applied. The scattering, due to interconnections between thick trabeculae, usually neglected in trabecular bone models, has been included in calculations when the structure backscatter was evaluated. Influence of the absorption in subsequent orders of scattering is also addressed. Results show that up to 1.5 MHz, the influence of higher scattering orders on the total scattered field characteristic can be neglected while for the higher frequencies, the relatively high amplitude interference peaks in higher scattering orders clearly occur. PMID:21973345

  7. Acoustic Neuroma

    MedlinePlus

    An acoustic neuroma is a benign tumor that develops on the nerve that connects the ear to the brain. ... can press against the brain, becoming life-threatening. Acoustic neuroma can be difficult to diagnose, because the ...

  8. Acoustic Seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  9. Acoustic seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  10. Surface Acoustic Wave Microfluidics

    NASA Astrophysics Data System (ADS)

    Yeo, Leslie Y.; Friend, James R.

    2014-01-01

    Fluid manipulations at the microscale and beyond are powerfully enabled through the use of 10-1,000-MHz acoustic waves. A superior alternative in many cases to other microfluidic actuation techniques, such high-frequency acoustics is almost universally produced by surface acoustic wave devices that employ electromechanical transduction in wafer-scale or thin-film piezoelectric media to generate the kinetic energy needed to transport and manipulate fluids placed in adjacent microfluidic structures. These waves are responsible for a diverse range of complex fluid transport phenomena - from interfacial fluid vibration and drop and confined fluid transport to jetting and atomization - underlying a flourishing research literature spanning fundamental fluid physics to chip-scale engineering applications. We highlight some of this literature to provide the reader with a historical basis, routes for more detailed study, and an impression of the field's future directions.

  11. Topological acoustics.

    PubMed

    Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile

    2015-03-20

    The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers. PMID:25839273

  12. Topological Acoustics

    NASA Astrophysics Data System (ADS)

    Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile

    2015-03-01

    The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers.

  13. Acoustic neuroma

    MedlinePlus

    Vestibular schwannoma; Tumor - acoustic; Cerebellopontine angle tumor; Angle tumor ... 177. Battista RA. Gamma knife radiosurgery for vestibular schwannoma. Otolaryngol Clin North Am . 2009;42:635-654. ...

  14. Acoustic asymmetric transmission based on time-dependent dynamical scattering

    PubMed Central

    Wang, Qing; Yang, Yang; Ni, Xu; Xu, Ye-Long; Sun, Xiao-Chen; Chen, Ze-Guo; Feng, Liang; Liu, Xiao-ping; Lu, Ming-Hui; Chen, Yan-Feng

    2015-01-01

    An acoustic asymmetric transmission device exhibiting unidirectional transmission property for acoustic waves is extremely desirable in many practical scenarios. Such a unique property may be realized in various configurations utilizing acoustic Zeeman effects in moving media as well as frequency-conversion in passive nonlinear acoustic systems and in active acoustic systems. Here we demonstrate a new acoustic frequency conversion process in a time-varying system, consisting of a rotating blade and the surrounding air. The scattered acoustic waves from this time-varying system experience frequency shifts, which are linearly dependent on the blade’s rotating frequency. Such scattering mechanism can be well described theoretically by an acoustic linear time-varying perturbation theory. Combining such time-varying scattering effects with highly efficient acoustic filtering, we successfully develop a tunable acoustic unidirectional device with 20 dB power transmission contrast ratio between two counter propagation directions at audible frequencies. PMID:26038886

  15. Musical Acoustics

    NASA Astrophysics Data System (ADS)

    Gough, Colin

    This chapter provides an introduction to the physical and psycho-acoustic principles underlying the production and perception of the sounds of musical instruments. The first section introduces generic aspects of musical acoustics and the perception of musical sounds, followed by separate sections on string, wind and percussion instruments.

  16. Acoustic transducer for nuclear reactor monitoring

    DOEpatents

    Ahlgren, Frederic F.; Scott, Paul F.

    1977-01-01

    A transducer to monitor a parameter and produce an acoustic signal from which the monitored parameter can be recovered. The transducer comprises a modified Galton whistle which emits a narrow band acoustic signal having a frequency dependent upon the parameter being monitored, such as the temperature of the cooling media of a nuclear reactor. Multiple locations within a reactor are monitored simultaneously by a remote acoustic receiver by providing a plurality of transducers each designed so that the acoustic signal it emits has a frequency distinct from the frequencies of signals emitted by the other transducers, whereby each signal can be unambiguously related to a particular transducer.

  17. An efficient high-order Nyström scheme for acoustic scattering by inhomogeneous penetrable media with discontinuous material interface

    NASA Astrophysics Data System (ADS)

    Anand, Akash; Pandey, Ambuj; Rathish Kumar, B. V.; Paul, Jagabandhu

    2016-04-01

    This text proposes a fast, rapidly convergent Nyström method for the solution of the Lippmann-Schwinger integral equation that mathematically models the scattering of time-harmonic acoustic waves by inhomogeneous obstacles, while allowing the material properties to jump across the interface. The method works with overlapping coordinate charts as a description of the given scatterer. In particular, it employs "partitions of unity" to simplify the implementation of high-order quadratures along with suitable changes of parametric variables to analytically resolve the singularities present in the integral operator to achieve desired accuracies in approximations. To deal with the discontinuous material interface in a high-order manner, a specialized quadrature is used in the boundary region. The approach further utilizes an FFT based strategy that uses equivalent source approximations to accelerate the evaluation of large number of interactions that arise in the approximation of the volumetric integral operator and thus achieves a reduced computational complexity of O (Nlog ⁡ N) for an N-point discretization. A detailed discussion on the solution methodology along with a variety of numerical experiments to exemplify its performance are presented in this paper.

  18. Underwater Acoustics

    NASA Astrophysics Data System (ADS)

    Kuperman, William A.; Roux, Philippe

    It is well underwater established that sound waves, compared to electromagnetic waves, propagate long distances in the ocean. Hence, in the ocean as opposed to air or a vacuum, one uses sound navigation and ranging (SONAR) instead navigation and ranging (SONAR) of radar, acoustic communication instead of radio, and acoustic imaging and tomography instead of microwave or optical imaging or X-ray tomography. Underwater acoustics is the science of sound in water (most commonly in the ocean) and encompasses not only the study of sound propagation, but also the masking of sound signals by interfering phenomenon and signal processing for extracting these signals from interference. This chapter we will present the basics physics of ocean acoustics and then discuss applications.

  19. Room Acoustics

    NASA Astrophysics Data System (ADS)

    Kuttruff, Heinrich; Mommertz, Eckard

    The traditional task of room acoustics is to create or formulate conditions which ensure the best possible propagation of sound in a room from a sound source to a listener. Thus, objects of room acoustics are in particular assembly halls of all kinds, such as auditoria and lecture halls, conference rooms, theaters, concert halls or churches. Already at this point, it has to be pointed out that these conditions essentially depend on the question if speech or music should be transmitted; in the first case, the criterion for transmission quality is good speech intelligibility, in the other case, however, the success of room-acoustical efforts depends on other factors that cannot be quantified that easily, not least it also depends on the hearing habits of the listeners. In any case, absolutely "good acoustics" of a room do not exist.

  20. Acoustic Neuroma

    MedlinePlus

    ... slow growing tumor which arise primarily from the vestibular portion of the VIII cranial nerve and lie ... you have a "brain tumor" called acoustic neuroma (vestibular schwannoma). You think you are the only one ...

  1. Opto-acoustic cell permeation

    SciTech Connect

    Visuri, S R; Heredia, N

    2000-03-09

    Optically generated acoustic waves have been used to temporarily permeate biological cells. This technique may be useful for enhancing transfection of DNA into cells or enhancing the absorption of locally delivered drugs. A diode-pumped frequency-doubled Nd:YAG laser operating at kHz repetition rates was used to produce a series of acoustic pulses. An acoustic wave was formed via thermoelastic expansion by depositing laser radiation into an absorbing dye. Generated pressures were measured with a PVDF hydrophone. The acoustic waves were transmitted to cultured and plated cells. The cell media contained a selection of normally- impermeable fluorescent-labeled dextran dyes. Following treatment with the opto-acoustic technique, cellular incorporation of dyes, up to 40,000 Molecular Weight, was noted. Control cells that did not receive opto-acoustic treatment had unremarkable dye incorporation. Uptake of dye was quantified via fluorescent microscopic analysis. Trypan Blue membrane exclusion assays and fluorescent labeling assays confirmed the vitality of cells following treatment. This method of enhanced drug delivery has the potential to dramatically reduce required drug dosages and associated side effects and enable revolutionary therapies.

  2. Acoustic biosensors.

    PubMed

    Fogel, Ronen; Limson, Janice; Seshia, Ashwin A

    2016-06-30

    Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of cost, size and scalability, as well as potential additional features including integration with microfluidics and electronics, scaled sensitivities associated with smaller dimensions and higher operational frequencies, the ability to multiplex detection across arrays of hundreds of devices embedded in a single chip, increased throughput and the ability to interrogate a wider range of modes including within the same device. Additionally, device fabrication is often compatible with semiconductor volume batch manufacturing techniques enabling cost scalability and a high degree of precision and reproducibility in the manufacturing process. Integration with microfluidics handling also enables suitable sample pre-processing/separation/purification/amplification steps that could improve selectivity and the overall signal-to-noise ratio. Three device types are reviewed here: (i) bulk acoustic wave sensors, (ii) surface acoustic wave sensors, and (iii) micro/nano-electromechanical system (MEMS/NEMS) sensors. PMID:27365040

  3. Acoustic biosensors

    PubMed Central

    Fogel, Ronen; Seshia, Ashwin A.

    2016-01-01

    Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of cost, size and scalability, as well as potential additional features including integration with microfluidics and electronics, scaled sensitivities associated with smaller dimensions and higher operational frequencies, the ability to multiplex detection across arrays of hundreds of devices embedded in a single chip, increased throughput and the ability to interrogate a wider range of modes including within the same device. Additionally, device fabrication is often compatible with semiconductor volume batch manufacturing techniques enabling cost scalability and a high degree of precision and reproducibility in the manufacturing process. Integration with microfluidics handling also enables suitable sample pre-processing/separation/purification/amplification steps that could improve selectivity and the overall signal-to-noise ratio. Three device types are reviewed here: (i) bulk acoustic wave sensors, (ii) surface acoustic wave sensors, and (iii) micro/nano-electromechanical system (MEMS/NEMS) sensors. PMID:27365040

  4. Theory and modeling of cylindrical thermo-acoustic transduction

    NASA Astrophysics Data System (ADS)

    Tong, Lihong; Lim, C. W.; Zhao, Xiushao; Geng, Daxing

    2016-06-01

    Models both for solid and thinfilm-solid cylindrical thermo-acoustic transductions are proposed and the corresponding acoustic pressure solutions are obtained. The acoustic pressure for an individual carbon nanotube (CNT) as a function of input power is investigated analytically and it is verified by comparing with the published experimental data. Further numerical analysis on the acoustic pressure response and characteristics for varying input frequency and distance are also examined both for solid and thinfilm-solid cylindrical thermo-acoustic transductions. Through detailed theoretical and numerical studies on the acoustic pressure solution for thinfilm-solid cylindrical transduction, it is concluded that a solid with smaller thermal conductivity favors to improve the acoustic performance. In general, the proposed models are applicable to a variety of cylindrical thermo-acoustic devices performing in different gaseous media.

  5. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, Butrus T.; Chou, Ching H.

    1990-01-01

    A shear acoustic transducer-lens system in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens.

  6. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, B.T.; Chou, C.H.

    1990-03-20

    A shear acoustic transducer-lens system is described in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens. 9 figs.

  7. Medical Acoustics

    NASA Astrophysics Data System (ADS)

    Beach, Kirk; Dunmire, Barbrina

    Medical acoustics can be subdivided into diagnostics and therapy. Diagnostics are further separated into auditory and ultrasonic methods, and both employ low amplitudes. Therapy (excluding medical advice) uses ultrasound for heating, cooking, permeablizing, activating and fracturing tissues and structures within the body, usually at much higher amplitudes than in diagnostics. Because ultrasound is a wave, linear wave physics are generally applicable, but recently nonlinear effects have become more important, even in low-intensity diagnostic applications.

  8. Acoustic chaos

    SciTech Connect

    Lauterborn, W.; Parlitz, U.; Holzfuss, J.; Billo, A.; Akhatov, I.

    1996-06-01

    Acoustic cavitation, a complex, spatio-temporal dynamical system, is investigated with respect to its chaotic properties. The sound output, the {open_quote}{open_quote}noise{close_quote}{close_quote}, is subjected to time series analysis. The spatial dynamics of the bubble filaments is captured by high speed holographic cinematography and subsequent digital picture processing from the holograms. Theoretical models are put forward for describing the pattern formation. {copyright} {ital 1996 American Institute of Physics.}

  9. Acoustic Tooth Cleaner

    NASA Technical Reports Server (NTRS)

    Heyman, J. S.

    1984-01-01

    Acoustically-energized water jet aids in plaque breakdown. Acoustic Wand includes acoustic transducer 1/4 wave plate, and tapered cone. Together elements energize solution of water containing mild abrasive injected into mouth to help prevent calculous buildup.

  10. Sonification of acoustic emission data

    NASA Astrophysics Data System (ADS)

    Raith, Manuel; Große, Christian

    2014-05-01

    While loading different specimens, acoustic emissions appear due to micro crack formation or friction of already existing crack edges. These acoustic emissions can be recorded using suitable ultrasonic transducers and transient recorders. The analysis of acoustic emissions can be used to investigate the mechanical behavior of different specimens under load. Our working group has undertaken several experiments, monitored with acoustic emission techniques. Different materials such as natural stone, concrete, wood, steel, carbon composites and bone were investigated. Also the experimental setup has been varied. Fire-spalling experiments on ultrahigh performance concrete and pullout experiments on bonded anchors have been carried out. Furthermore uniaxial compression tests on natural stone and animal bone had been conducted. The analysis tools include not only the counting of events but the analysis of full waveforms. Powerful localization algorithms and automatic onset picking techniques (based on Akaikes Information Criterion) were established to handle the huge amount of data. Up to several thousand events were recorded during experiments of a few minutes. More sophisticated techniques like moment tensor inversion have been established on this relatively small scale as well. Problems are related to the amount of data but also to signal-to-noise quality, boundary conditions (reflections) sensor characteristics and unknown and changing Greens functions of the media. Some of the acoustic emissions recorded during these experiments had been transferred into audio range. The transformation into the audio range was done using Matlab. It is the aim of the sonification to establish a tool that is on one hand able to help controlling the experiment in-situ and probably adjust the load parameters according to the number and intensity of the acoustic emissions. On the other hand sonification can help to improve the understanding of acoustic emission techniques for training

  11. Tungsten Oxide Layers of High Acoustic Impedance for Fully Insulating Acoustic Reflectors.

    PubMed

    DeMiguel-Ramos, M; Diaz-Duran, Barbara; Munir, Junaid; Clement, Marta; Mirea, Teona; Olivares, Jimena; Iborra, Enrique

    2016-07-01

    Gravimetric sensors based on solidly mounted resonators require fully insulating acoustic reflectors to avoid parasitics when operating in liquid media. In this work, we propose a new high-acoustic impedance material, tungsten oxide ([Formula: see text]), for acoustic reflectors. We have optimized the sputtering conditions of [Formula: see text] to obtain nonconductive layers with mass density around [Formula: see text] and acoustic velocities for the shear and the longitudinal modes up to 2700 and 4500 m/s, respectively. Compared to other conventionally used high impedance layers, [Formula: see text] films display several manufacture advantages, such as high deposition rates, great reproducibility, and good adhesion to underlying substrates. We have demonstrated the applicability of [Formula: see text] in practical shear mode bulk acoustic wave resonators that display good performance in liquid environments. PMID:26571521

  12. Acoustic behaviors of unsaturated soils

    NASA Astrophysics Data System (ADS)

    Lu, Z.

    2011-12-01

    Soils are unconsolidated granular materials, consisting of solid particles, water and air. Their mechanical and dynamic behaviors are determined by the discrete nature of the media as well as external and inter-particle forces. For unsaturated soils, two factors significantly affect soils acoustic/seismic responses: external pressure and internal water potential/matric suction. In triaxial cell tests, unsaturated soils were subjected to predefined stress paths to undergo stages of normal consolidation, unload-reload cycles, and failure. The stress deformation curve and stress-P-wave velocity were measured and compared. The study revealed that soil's dynamic response to external pressure are similar to those of the load-deformation behaviors and demonstrated that acoustic velocity can be used to monitor the state of stress of soils. In a long term field soil survey, the P-wave velocities were found to be correlated with water potential as expressed as a power-law relationship. The above phenomena can be understood by using the Terzaghi' s the principle of effective stress. The measured results were in good agreement with Brutsaert theory. The effective stress concept can also be applied to explain the observations in a soil pipe flow study in which soil internal erosion processes were monitored and interpreted by the temporal evolution of the P-wave velocity. In addition to above linear acoustic behaviors, soils, like other earth materials, exhibit astonishing non-classical nonlinear behaviors such as end-point memory, hysteresis, strain -dependent shear modulus, resonant frequency shift, and phase shift, harmonics generation, etc. A nonlinear acoustic study of a soil as a function of water content showed that the nonlinear acoustic parameter are much sensitive to the variations of soil water content than that of the acoustic velocity.

  13. Acoustic transducer

    DOEpatents

    Drumheller, D.S.

    1997-12-30

    An acoustic transducer is described comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2,000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers. 4 figs.

  14. Acoustic transducer

    DOEpatents

    Drumheller, Douglas S.

    1997-01-01

    An acoustic transducer comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers.

  15. Envelope Solitons in Acoustically Dispersive Vitreous Silica

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.; Yost, William T.

    2012-01-01

    Acoustic radiation-induced static strains, displacements, and stresses are manifested as rectified or dc waveforms linked to the energy density of an acoustic wave or vibrational mode via the mode nonlinearity parameter of the material. An analytical model is developed for acoustically dispersive media that predicts the evolution of the energy density of an initial waveform into a series of energy solitons that generates a corresponding series of radiation-induced static strains (envelope solitons). The evolutionary characteristics of the envelope solitons are confirmed experimentally in Suprasil W1 vitreous silica. The value (-11.9 plus or minus 1.43) for the nonlinearity parameter, determined from displacement measurements of the envelope solitons via a capacitive transducer, is in good agreement with the value (-11.6 plus or minus 1.16) obtained independently from acoustic harmonic generation measurements. The agreement provides strong, quantitative evidence for the validity of the model.

  16. Nonlinear propagation and control of acoustic waves in phononic superlattices

    NASA Astrophysics Data System (ADS)

    Jiménez, Noé; Mehrem, Ahmed; Picó, Rubén; García-Raffi, Lluís M.; Sánchez-Morcillo, Víctor J.

    2016-05-01

    The propagation of intense acoustic waves in a one-dimensional phononic crystal is studied. The medium consists in a structured fluid, formed by a periodic array of fluid layers with alternating linear acoustic properties and quadratic nonlinearity coefficient. The spacing between layers is of the order of the wavelength, therefore Bragg effects such as band gaps appear. We show that the interplay between strong dispersion and nonlinearity leads to new scenarios of wave propagation. The classical waveform distortion process typical of intense acoustic waves in homogeneous media can be strongly altered when nonlinearly generated harmonics lie inside or close to band gaps. This allows the possibility of engineer a medium in order to get a particular waveform. Examples of this include the design of media with effective (e.g., cubic) nonlinearities, or extremely linear media (where distortion can be canceled). The presented ideas open a way towards the control of acoustic wave propagation in nonlinear regime. xml:lang="fr"

  17. Acoustic hemostasis

    NASA Astrophysics Data System (ADS)

    Crum, L.; Andrew, M.; Bailey, M.; Beach, K.; Brayman, A.; Curra, F.; Kaczkowski, P.; Kargl, S.; Martin, R.; Vaezy, S.

    2003-04-01

    Over the past several years, the Center for Industrial and Medical Ultrasound (CIMU) at the Applied Physics Laboratory in the University of Washington has undertaken a broad research program in the general area of High Intensity Focused Ultrasound (HIFU). Our principal emphasis has been on the use of HIFU to induce hemostasis; in particular, CIMU has sought to develop a small, lightweight, portable device that would use ultrasound for both imaging and therapy. Such a technology is needed because nearly 50% of combat casualty mortality results from exsanguinations, or uncontrolled bleeding. A similar percentage occurs for civilian death due to trauma. In this general review, a presentation of the general problem will be given, as well as our recent approaches to the development of an image-guided, transcutaneous, acoustic hemostasis device. [Work supported in part by the USAMRMC, ONR and the NIH.

  18. Acoustic cryocooler

    DOEpatents

    Swift, Gregory W.; Martin, Richard A.; Radenbaugh, Ray

    1990-01-01

    An acoustic cryocooler with no moving parts is formed from a thermoacoustic driver (TAD) driving a pulse tube refrigerator (PTR) through a standing wave tube. Thermoacoustic elements in the TAD are spaced apart a distance effective to accommodate the increased thermal penetration length arising from the relatively low TAD operating frequency in the range of 15-60 Hz. At these low operating frequencies, a long tube is required to support the standing wave. The tube may be coiled to reduce the overall length of the cryocooler. One or two PTR's are located on the standing wave tube adjacent antinodes in the standing wave to be driven by the standing wave pressure oscillations. It is predicted that a heat input of 1000 W at 1000 K will maintian a cooling load of 5 W at 80 K.

  19. Acoustic transducer

    DOEpatents

    Drumheller, Douglas S.

    2000-01-01

    An active acoustic transducer tool for use down-hole applications. The tool includes a single cylindrical mandrel including a shoulder defining the boundary of a narrowed portion over which is placed a sandwich-style piezoelectric tranducer assembly. The piezoelectric transducer assembly is prestressed by being placed in a thermal interference fit between the shoulder of the mandrel and the base of an anvil which is likewise positioned over the narrower portion of the mandrel. In the preferred embodiment, assembly of the tool is accomplished using a hydraulic jack to stretch the mandrel prior to emplacement of the cylindrical sandwich-style piezoelectric transducer assembly and anvil. After those elements are positioned and secured, the stretched mandrel is allowed to return substantially to its original (pre-stretch) dimensions with the result that the piezoelectric transducer elements are compressed between the anvil and the shoulder of the mandrel.

  20. Acoustic telemetry.

    SciTech Connect

    Drumheller, Douglas Schaeffer; Kuszmaul, Scott S.

    2003-08-01

    Broadcasting messages through the earth is a daunting task. Indeed, broadcasting a normal telephone conversion through the earth by wireless means is impossible with todays technology. Most of us don't care, but some do. Industries that drill into the earth need wireless communication to broadcast navigation parameters. This allows them to steer their drill bits. They also need information about the natural formation that they are drilling. Measurements of parameters such as pressure, temperature, and gamma radiation levels can tell them if they have found a valuable resource such as a geothermal reservoir or a stratum bearing natural gas. Wireless communication methods are available to the drilling industry. Information is broadcast via either pressure waves in the drilling fluid or electromagnetic waves in the earth and well tubing. Data transmission can only travel one way at rates around a few baud. Given that normal Internet telephone modems operate near 20,000 baud, these data rates are truly very slow. Moreover, communication is often interrupted or permanently blocked by drilling conditions or natural formation properties. Here we describe a tool that communicates with stress waves traveling through the steel drill pipe and production tubing in the well. It's based on an old idea called Acoustic Telemetry. But what we present here is more than an idea. This tool exists, it's drilled several wells, and it works. Currently, it's the first and only acoustic telemetry tool that can withstand the drilling environment. It broadcasts one way over a limited range at much faster rates than existing methods, but we also know how build a system that can communicate both up and down wells of indefinite length.

  1. Media Clips

    ERIC Educational Resources Information Center

    Vennebush, G. Patrick

    2004-01-01

    Media Clips aims to offer readers contemporary, authentic applications of quantitative reasoning based on print or electronic media. Clips may be in text or graphic format, and clip sources may be either print or electronic media.

  2. Acoustic Microfluidics for Bioanalytical Application

    NASA Astrophysics Data System (ADS)

    Lopez, Gabriel

    2013-03-01

    This talk will present new methods the use of ultrasonic standing waves in microfluidic systems to manipulate microparticles for the purpose of bioassays and bioseparations. We have recently developed multi-node acoustic focusing flow cells that can position particles into many parallel flow streams and have demonstrated the potential of such flow cells in the development of high throughput, parallel flow cytometers. These experiments show the potential for the creation of high throughput flow cytometers in applications requiring high flow rates and rapid detection of rare cells. This talk will also present the development of elastomeric capture microparticles and their use in acoustophoretic separations. We have developed simple methods to form elastomeric particles that are surface functionalized with biomolecular recognition reagents. These compressible particles exhibit negative acoustic contrast in ultrasound when suspended in aqueous media, blood serum or diluted blood. These particles can be continuously separated from cells by flowing them through a microfluidic device that uses an ultrasonic standing wave to align the blood cells, which exhibit positive acoustic contrast, at a node in the acoustic pressure distribution while aligning the negative acoustic contrast elastomeric particles at the antinodes. Laminar flow of the separated particles to downstream collection ports allows for collection of the separated negative contrast particles and cells. Separated elastomeric particles were analyzed via flow cytometry to demonstrate nanomolar detection for prostate specific antigen in aqueous buffer and picomolar detection for IgG in plasma and diluted blood samples. This approach has potential applications in the development of rapid assays that detect the presence of low concentrations of biomarkers (including biomolecules and cells) in a number of biological sample types. We acknowledge support through the NSF Research Triangle MRSEC.

  3. Acoustic hemostasis

    NASA Astrophysics Data System (ADS)

    Crum, Lawrence; Beach, Kirk; Carter, Stephen; Chandler, Wayne; Curra, Francesco; Kaczkowski, Peter; Keilman, George; Khokhlova, Vera; Martin, Roy; Mourad, Pierre; Vaezy, Shahram

    2000-07-01

    In cases of severe injury, physicians speak of a "golden hour"—a brief grace period in which quickly applied, proper therapy can save the life of the patient. Much of this mortality results from exsanguination, i.e., bleeding to death—often from internal hemorrhage. The inability of a paramedic to treat breaches in the vascular system deep within the body or to stem the loss of blood from internal organs is a major reason for the high level of mortality associated with blunt trauma. We have undertaken an extensive research program to treat the problem of internal bleeding. Our approach is as follows: (a) We use scanning ultrasound to identify internal bleeding and hemorrhage, (b) we use ultrasound imaging to locate specific breaches in the vascular system, both from damaged vessels and gross damage to the capillary bed, and (c) we use High Intensity Focused Ultrasound (HIFU) to treat the damaged region and to induce hemostasis. We present a general review of this research with some emphasis on the role of nonlinear acoustics.

  4. Acoustic source for generating an acoustic beam

    DOEpatents

    Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian

    2016-05-31

    An acoustic source for generating an acoustic beam includes a housing; a plurality of spaced apart piezo-electric layers disposed within the housing; and a non-linear medium filling between the plurality of layers. Each of the plurality of piezoelectric layers is configured to generate an acoustic wave. The non-linear medium and the plurality of piezo-electric material layers have a matching impedance so as to enhance a transmission of the acoustic wave generated by each of plurality of layers through the remaining plurality of layers.

  5. Acoustic Holography

    NASA Astrophysics Data System (ADS)

    Kim, Yang-Hann

    One of the subtle problems that make noise control difficult for engineers is the invisibility of noise or sound. A visual image of noise often helps to determine an appropriate means for noise control. There have been many attempts to fulfill this rather challenging objective. Theoretical (or numerical) means for visualizing the sound field have been attempted, and as a result, a great deal of progress has been made. However, most of these numerical methods are not quite ready for practical applications to noise control problems. In the meantime, rapid progress with instrumentation has made it possible to use multiple microphones and fast signal-processing systems. Although these systems are not perfect, they are useful. A state-of-the-art system has recently become available, but it still has many problematic issues; for example, how can one implement the visualized noise field. The constructed noise or sound picture always consists of bias and random errors, and consequently, it is often difficult to determine the origin of the noise and the spatial distribution of the noise field. Section 26.2 of this chapter introduces a brief history, which is associated with "sound visualization," acoustic source identification methods and what has been accomplished with a line or surface array. Section 26.2.3 introduces difficulties and recent studies, including de-Dopplerization and de-reverberation methods, both essentialfor visualizing a moving noise source, such as occurs for cars or trains. This section also addresses what produces ambiguity in realizing real sound sources in a room or closed space. Another major issue associated with sound/noise visualization is whether or not we can distinguish between mutual dependencies of noise in space (Sect. 26.2.4); for example, we are asked to answer the question, "Can we see two birds singing or one bird with two beaks?"

  6. Acoustic Holography

    NASA Astrophysics Data System (ADS)

    Kim, Yang-Hann

    One of the subtle problems that make noise control difficult for engineers is the invisibility of noise or sound. A visual image of noise often helps to determine an appropriate means for noise control. There have been many attempts to fulfill this rather challenging objective. Theoretical (or numerical) means for visualizing the sound field have been attempted, and as a result, a great deal of progress has been made. However, most of these numerical methods are not quite ready for practical applications to noise control problems. In the meantime, rapid progress with instrumentation has made it possible to use multiple microphones and fast signal-processing systems. Although these systems are not perfect, they are useful. A state-of-the-art system has recently become available, but it still has many problematic issues; for example, how can one implement the visualized noise field. The constructed noise or sound picture always consists of bias and random errors, and consequently, it is often difficult to determine the origin of the noise and the spatial distribution of the noise field. Section 26.2 of this chapter introduces a brief history, which is associated with sound visualization, acoustic source identification methods and what has been accomplished with a line or surface array. Section 26.2.3 introduces difficulties and recent studies, including de-Dopplerization and de-re verberation methods, both essential for visualizing a moving noise source, such as occurs for cars or trains. This section also addresses what produces ambiguity in realizing real sound sources in a room or closed space. Another major issue associated with sound/noise visualization is whether or not we can distinguish between mutual dependencies of noise in space (Sect. 26.2.4); for example, we are asked to answer the question, Can we see two birds singing or one bird with two beaks?

  7. What Is an Acoustic Neuroma

    MedlinePlus

    ... Acoustic Neuroma An acoustic neuroma, also called a vestibular schwannoma, is a rare benign tumor of the ... Acoustic Neuroma? An acoustic neuroma, known as a vestibular schwannoma, is a benign (non-cancerous) growth that ...

  8. Canonical Acoustics and Its Application to Surface Acoustic Wave on Acoustic Metamaterials

    NASA Astrophysics Data System (ADS)

    Shen, Jian Qi

    2016-08-01

    In a conventional formalism of acoustics, acoustic pressure p and velocity field u are used for characterizing acoustic waves propagating inside elastic/acoustic materials. We shall treat some fundamental problems relevant to acoustic wave propagation alternatively by using canonical acoustics (a more concise and compact formalism of acoustic dynamics), in which an acoustic scalar potential and an acoustic vector potential (Φ ,V), instead of the conventional acoustic field quantities such as acoustic pressure and velocity field (p,u) for characterizing acoustic waves, have been defined as the fundamental variables. The canonical formalism of the acoustic energy-momentum tensor is derived in terms of the acoustic potentials. Both the acoustic Hamiltonian density and the acoustic Lagrangian density have been defined, and based on this formulation, the acoustic wave quantization in a fluid is also developed. Such a formalism of acoustic potentials is employed to the problem of negative-mass-density assisted surface acoustic wave that is a highly localized surface bound state (an eigenstate of the acoustic wave equations). Since such a surface acoustic wave can be strongly confined to an interface between an acoustic metamaterial (e.g., fluid-solid composite structures with a negative dynamical mass density) and an ordinary material (with a positive mass density), it will give rise to an effect of acoustic field enhancement on the acoustic interface, and would have potential applications in acoustic device design for acoustic wave control.

  9. Media education.

    PubMed

    Strasburger, Victor C

    2010-11-01

    The American Academy of Pediatrics recognizes that exposure to mass media (eg, television, movies, video and computer games, the Internet, music lyrics and videos, newspapers, magazines, books, advertising) presents health risks for children and adolescents but can provide benefits as well. Media education has the potential to reduce the harmful effects of media and accentuate the positive effects. By understanding and supporting media education, pediatricians can play an important role in reducing harmful effects of media on children and adolescents. PMID:20876180

  10. Acoustic Purification of Extracellular Microvesicles

    PubMed Central

    Lee, Kyungheon; Shao, Huilin; Weissleder, Ralph; Lee, Hakho

    2015-01-01

    Microvesicles (MVs) are an increasingly important source for biomarker discovery and clinical diagnostics. The small size of MVs and their presence in complex biological environment, however, pose practical technical challenges, particularly when sample volumes are small. We herein present an acoustic nano-filter system that size-specifically separates MVs in a continuous and contact-free manner. The separation is based on ultrasound standing waves that exert differential acoustic force on MVs according to their size and density. By optimizing the design of the ultrasound transducers and underlying electronics, we were able to achieve a high separation yield and resolution. The “filter size-cutoff” can be controlled electronically in situ and enables versatile MV-size selection. We applied the acoustic nano-filter to isolate nanoscale (<200 nm) vesicles from cell culture media as well as MVs in stored red blood cell products. With the capacity for rapid and contact-free MV isolation, the developed system could become a versatile preparatory tool for MV analyses. PMID:25672598

  11. Acoustic purification of extracellular microvesicles.

    PubMed

    Lee, Kyungheon; Shao, Huilin; Weissleder, Ralph; Lee, Hakho

    2015-03-24

    Microvesicles (MVs) are an increasingly important source for biomarker discovery and clinical diagnostics. The small size of MVs and their presence in complex biological environment, however, pose technical challenges in sample preparation, particularly when sample volumes are small. We herein present an acoustic nanofilter system that size-specifically separates MVs in a continuous and contact-free manner. The separation uses ultrasound standing waves to exert differential acoustic force on MVs according to their size and density. By optimizing the design of the ultrasound transducers and underlying electronics, we were able to achieve a high separation yield and resolution. The "filter size-cutoff" can be controlled electronically in situ, which enables versatile MV-size selection. We applied the acoustic nanofilter to isolate nanoscale (<200 nm) vesicles from cell culture media as well as MVs in stored red blood cell products. With the capacity for rapid and contact-free MV isolation, the developed system could become a versatile preparatory tool for MV analyses. PMID:25672598

  12. A theoretical study of the feasibility of acoustical tweezer: Ray acoustics approach

    NASA Astrophysics Data System (ADS)

    Lee, Jungwoo; Shung, Kirk

    2005-04-01

    Optical tweezer has been found to have many biomedical applications in trapping macromolecules and cells. For the trapping mechanism, there has to be a sharp spatial change in axial optical intensity and the particle size must be much greater than the wavelength. Similar phenomenon may exist in acoustics. This work was undertaken to demonstrate theoretically that it is possible to acoustically trap particles near the focal point if certain conditions are met. Acoustic force exerted on fat tissue in ultrasonic fields is analyzed in ray acoustics regime where the wavelength of acoustic beam is much smaller than the size of the particle. In this paper, the analysis is therefore based on the field pattern produced by a strongly focused 100 MHz ultrasonic transducer with Gaussian intensity distribution. The magnitude of force and Fresnel coefficients at various positions are calculated. According to the simulation results, acoustical tweezer works particularly when the beam width at focus is one wavelength and the tolerance of acoustic impedance mismatch between two media lies within 6.7%. [Work supported by NIH Grant P41-EB2182.

  13. Symptoms of Acoustic Neuroma

    MedlinePlus

    ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ...

  14. Acoustic emission frequency discrimination

    NASA Technical Reports Server (NTRS)

    Sugg, Frank E. (Inventor); Graham, Lloyd J. (Inventor)

    1988-01-01

    In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered.

  15. Tutorial on architectural acoustics

    NASA Astrophysics Data System (ADS)

    Shaw, Neil; Talaske, Rick; Bistafa, Sylvio

    2002-11-01

    This tutorial is intended to provide an overview of current knowledge and practice in architectural acoustics. Topics covered will include basic concepts and history, acoustics of small rooms (small rooms for speech such as classrooms and meeting rooms, music studios, small critical listening spaces such as home theatres) and the acoustics of large rooms (larger assembly halls, auditoria, and performance halls).

  16. Laser-induced acoustic imaging of underground objects

    NASA Astrophysics Data System (ADS)

    Li, Wen; DiMarzio, Charles A.; McKnight, Stephen W.; Sauermann, Gerhard O.; Miller, Eric L.

    1999-02-01

    This paper introduces a new demining technique based on the photo-acoustic interaction, together with results from photo- acoustic experiments. We have buried different types of targets (metal, rubber and plastic) in different media (sand, soil and water) and imaged them by measuring reflection of acoustic waves generated by irradiation with a CO2 laser. Research has been focused on the signal acquisition and signal processing. A deconvolution method using Wiener filters is utilized in data processing. Using a uniform spatial distribution of laser pulses at the ground's surface, we obtained 3D images of buried objects. The images give us a clear representation of the shapes of the underground objects. The quality of the images depends on the mismatch of acoustic impedance of the buried objects, the bandwidth and center frequency of the acoustic sensors and the selection of filter functions.

  17. Soft 3D acoustic metamaterial with negative index.

    PubMed

    Brunet, Thomas; Merlin, Aurore; Mascaro, Benoit; Zimny, Kevin; Leng, Jacques; Poncelet, Olivier; Aristégui, Christophe; Mondain-Monval, Olivier

    2015-04-01

    Many efforts have been devoted to the design and achievement of negative-refractive-index metamaterials since the 2000s. One of the challenges at present is to extend that field beyond electromagnetism by realizing three-dimensional (3D) media with negative acoustic indices. We report a new class of locally resonant ultrasonic metafluids consisting of a concentrated suspension of macroporous microbeads engineered using soft-matter techniques. The propagation of Gaussian pulses within these random distributions of 'ultra-slow' Mie resonators is investigated through in situ ultrasonic experiments. The real part of the acoustic index is shown to be negative (up to almost - 1) over broad frequency bandwidths, depending on the volume fraction of the microbeads as predicted by multiple-scattering calculations. These soft 3D acoustic metamaterials open the way for key applications such as sub-wavelength imaging and transformation acoustics, which require the production of acoustic devices with negative or zero-valued indices. PMID:25502100

  18. New Media.

    ERIC Educational Resources Information Center

    Downtown Business Quarterly, 1998

    1998-01-01

    This theme issue explores lower Manhattan's burgeoning "New Media" industry, a growing source of jobs in lower Manhattan. The first article, "New Media Manpower Issues" (Rodney Alexander), addresses manpower, training, and workforce demands faced by new media companies in New York City. The second article, "Case Study: Hiring @ Dynamid" (John…

  19. Media Panel.

    ERIC Educational Resources Information Center

    Marklund, Inger, Ed.; Hanse, Mona-Britt, Ed.

    1984-01-01

    The Swedish Media Panel is a research program about children and young persons and their use of mass media. The aim of the ten-year (1975-1985) project is to explain how media habits originate, how they change as children grow older, what factors on the part of children themselves and in their surroundings may be connected with a certain use of…

  20. AST Launch Vehicle Acoustics

    NASA Technical Reports Server (NTRS)

    Houston, Janice; Counter, D.; Giacomoni, D.

    2015-01-01

    The liftoff phase induces acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are then used in the prediction of internal vibration responses of the vehicle and components which result in the qualification levels. Thus, predicting these liftoff acoustic (LOA) environments is critical to the design requirements of any launch vehicle. If there is a significant amount of uncertainty in the predictions or if acoustic mitigation options must be implemented, a subscale acoustic test is a feasible pre-launch test option to verify the LOA environments. The NASA Space Launch System (SLS) program initiated the Scale Model Acoustic Test (SMAT) to verify the predicted SLS LOA environments and to determine the acoustic reduction with an above deck water sound suppression system. The SMAT was conducted at Marshall Space Flight Center and the test article included a 5% scale SLS vehicle model, tower and Mobile Launcher. Acoustic and pressure data were measured by approximately 250 instruments. The SMAT liftoff acoustic results are presented, findings are discussed and a comparison is shown to the Ares I Scale Model Acoustic Test (ASMAT) results.

  1. Acoustic Translation of an Acoustically Levitated Sample

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Allen, J. L.

    1986-01-01

    Acoustic-levitation apparatus uses only one acoustic mode to move sample from one region of chamber to another. Sample heated and cooled quickly by translation between hot and cold regions of levitation chamber. Levitated sample is raised into furnace region by raising plunger. Frequency of sound produced by transducers adjusted by feedback system to maintain (102) resonant mode, which levitates sample midway between transducers and plunger regardless of plunger position.

  2. Reflection and Scattering of Acoustical Waves from a Discontinuity in Absorption

    NASA Astrophysics Data System (ADS)

    Jones, J. P.; Leeman, S.; Nolan, E.; Lee, D.

    The reflection and transmission of a plane acoustical wave from a planar boundary at the interface between two homogeneous media of different acoustical properties is a classical problem in acoustics that has served as a basis for many developments in acoustics for over 100 years. This problem, detailed in virtually every textbook on acoustics, provides us with the acoustical analogue to Snell's Law in optics and gives us correspondingly simple results. Classical acoustics predicts that a reflection from a boundary occurs only if the characteristic acoustical impedances of the two media are different. Here we show that a reflection also occurs if the media have the same impedances but different absorption coefficients. Our analysis yields some surprising results. For example, a reflection will occur at a discontinuity in absorption even if the impedance is uniform and continuous across the interface. In addition, a discontinuity in impedance at an interface between two media that have constant and equal, but non-zero absorption, results in a reflection coefficient that is dependent on absorption as well as impedance. In general, reflection coefficients now become frequency dependent. To experimentally test our results, we measured the reflection at the interface between water and castor oil, two liquids with similar impedances but very different absorption coefficients. Measurement of the reflection coefficient between 1 and 50 MHz demonstrated a frequency dependence that was in good agreement with our analysis.

  3. Acoustic metamaterial design and applications

    NASA Astrophysics Data System (ADS)

    Zhang, Shu

    The explosion of interest in metamaterials is due to the dramatically increased manipulation ability over light as well as sound waves. This material research was stimulated by the opportunity to develop an artificial media with negative refractive index and the application in superlens which allows super-resolution imaging. High-resolution acoustic imaging techniques are the essential tools for nondestructive testing and medical screening. However, the spatial resolution of the conventional acoustic imaging methods is restricted by the incident wavelength of ultrasound. This is due to the quickly fading evanescent fields which carry the subwavelength features of objects. By focusing the propagating wave and recovering the evanescent field, a flat lens with negative-index can potentially overcome the diffraction limit. We present the first experimental demonstration of focusing ultrasound waves through a flat acoustic metamaterial lens composed of a planar network of subwavelength Helmholtz resonators. We observed a tight focus of half-wavelength in width at 60.5 KHz by imaging a point source. This result is in excellent agreement with the numerical simulation by transmission line model in which we derived the effective mass density and compressibility. This metamaterial lens also displays variable focal length at different frequencies. Our experiment shows the promise of designing compact and light-weight ultrasound imaging elements. Moreover, the concept of metamaterial extends far beyond negative refraction, rather giving enormous choice of material parameters for different applications. One of the most interesting examples these years is the invisible cloak. Such a device is proposed to render the hidden object undetectable under the flow of light or sound, by guiding and controlling the wave path through an engineered space surrounding the object. However, the cloak designed by transformation optics usually calls for a highly anisotropic metamaterial, which

  4. Nonlinear Acoustics in Fluids

    NASA Astrophysics Data System (ADS)

    Lauterborn, Werner; Kurz, Thomas; Akhatov, Iskander

    At high sound intensities or long propagation distances at in fluids sufficiently low damping acoustic phenomena become nonlinear. This chapter focuses on nonlinear acoustic wave properties in gases and liquids. The origin of nonlinearity, equations of state, simple nonlinear waves, nonlinear acoustic wave equations, shock-wave formation, and interaction of waves are presented and discussed. Tables are given for the nonlinearity parameter B/A for water and a range of organic liquids, liquid metals and gases. Acoustic cavitation with its nonlinear bubble oscillations, pattern formation and sonoluminescence (light from sound) are modern examples of nonlinear acoustics. The language of nonlinear dynamics needed for understanding chaotic dynamics and acoustic chaotic systems is introduced.

  5. Form Follows Function: Redesigning the School Library Media Center.

    ERIC Educational Resources Information Center

    Perry, Karen

    1997-01-01

    Discusses factors in redesigning school library media centers: electronic resources, electricity, furniture, lighting, and acoustics. Presents a case study of Wake County (North Carolina) Schools and describes the county standards for media center design and renovation for elementary, middle, and high schools. (PEN)

  6. Localized acoustic surface modes

    NASA Astrophysics Data System (ADS)

    Farhat, Mohamed; Chen, Pai-Yen; Bağcı, Hakan

    2016-04-01

    We introduce the concept of localized acoustic surface modes. We demonstrate that they are induced on a two-dimensional cylindrical rigid surface with subwavelength corrugations under excitation by an incident acoustic plane wave. Our results show that the corrugated rigid surface is acoustically equivalent to a cylindrical scatterer with uniform mass density that can be represented using a Drude-like model. This, indeed, suggests that plasmonic-like acoustic materials can be engineered with potential applications in various areas including sensing, imaging, and cloaking.

  7. Low frequency acoustic microscope

    DOEpatents

    Khuri-Yakub, Butrus T.

    1986-11-04

    A scanning acoustic microscope is disclosed for the detection and location of near surface flaws, inclusions or voids in a solid sample material. A focused beam of acoustic energy is directed at the sample with its focal plane at the subsurface flaw, inclusion or void location. The sample is scanned with the beam. Detected acoustic energy specularly reflected and mode converted at the surface of the sample and acoustic energy reflected by subsurface flaws, inclusions or voids at the focal plane are used for generating an interference signal which is processed and forms a signal indicative of the subsurface flaws, inclusions or voids.

  8. Acoustic dispersive prism

    PubMed Central

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R.

    2016-01-01

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz–1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium. PMID:26739504

  9. Acoustic dispersive prism

    NASA Astrophysics Data System (ADS)

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R.

    2016-01-01

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz-1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium.

  10. Acoustic dispersive prism.

    PubMed

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R

    2016-01-01

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz-1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium. PMID:26739504

  11. The challenge of acoustics

    NASA Astrophysics Data System (ADS)

    Lord, P.

    1981-01-01

    The various applications of acoustics, including sonar, ultrasonic examination of unborn foetuses and architectural applications, are briefly reviewed. Problems in traffic and industrial noise, auditorium design and explosive noise are considered in more detail. The educational aspects of acoustical science and technology are briefly considered.

  12. Acoustics Critical Readiness Review

    NASA Technical Reports Server (NTRS)

    Ballard, Kenny

    2010-01-01

    This presentation reviews the status of the acoustic equipment from the medical operations perspective. Included is information about the acoustic dosimeters, sound level meter, and headphones that are planned for use while on orbit. Finally there is information about on-orbit hearing assessments.

  13. Broadband metamaterial for nonresonant matching of acoustic waves

    NASA Astrophysics Data System (ADS)

    D'Aguanno, G.; Le, K. Q.; Trimm, R.; Alù, A.; Mattiucci, N.; Mathias, A. D.; Aközbek, N.; Bloemer, M. J.

    2012-03-01

    Unity transmittance at an interface between bulk media is quite common for polarized electromagnetic waves incident at the Brewster angle, but it is rarely observed for sound waves at any angle of incidence. In the following, we theoretically and experimentally demonstrate an acoustic metamaterial possessing a Brewster-like angle that is completely transparent to sound waves over an ultra-broadband frequency range with >100% bandwidth. The metamaterial, consisting of a hard metal with subwavelength apertures, provides a surface impedance matching mechanism that can be arbitrarily tailored to specific media. The nonresonant nature of the impedance matching effectively decouples the front and back surfaces of the metamaterial allowing one to independently tailor the acoustic impedance at each interface. On the contrary, traditional methods for acoustic impedance matching, for example in medical imaging, rely on resonant tunneling through a thin antireflection layer, which is inherently narrowband and angle specific.

  14. Acoustic gaps in a chain of magnetic spheres.

    PubMed

    Sierra-Valdez, F J; Pacheco-Vázquez, F; Carvente, O; Malloggi, F; Cruz-Damas, J; Rechtman, R; Ruiz-Suárez, J C

    2010-01-01

    Acoustic gaps are normally observed in granular inhomogeneous structures made of composite materials. The modulation of the elastic properties in such media creates the coherent effects of scattering and interference that ultimately lead to frequency intervals where sound propagation is forbidden. Contrastingly, we report here an experimental observation of acoustic gaps in homogeneous media; specifically, in granular chains. The beads used in our study are magnetic. Therefore, instead of modulating the elastic properties of the chain, we modulate the magnetization (i.e., the contact forces). We also observe that the propagation speed of acoustic signals through the magnetic chains used in this study is at odds with the speed predicted by Hertz's law. PMID:20365362

  15. Ocean acoustic hurricane classification.

    PubMed

    Wilson, Joshua D; Makris, Nicholas C

    2006-01-01

    Theoretical and empirical evidence are combined to show that underwater acoustic sensing techniques may be valuable for measuring the wind speed and determining the destructive power of a hurricane. This is done by first developing a model for the acoustic intensity and mutual intensity in an ocean waveguide due to a hurricane and then determining the relationship between local wind speed and underwater acoustic intensity. From this it is shown that it should be feasible to accurately measure the local wind speed and classify the destructive power of a hurricane if its eye wall passes directly over a single underwater acoustic sensor. The potential advantages and disadvantages of the proposed acoustic method are weighed against those of currently employed techniques. PMID:16454274

  16. Acoustic Remote Sensing

    NASA Astrophysics Data System (ADS)

    Dowling, David R.; Sabra, Karim G.

    2015-01-01

    Acoustic waves carry information about their source and collect information about their environment as they propagate. This article reviews how these information-carrying and -collecting features of acoustic waves that travel through fluids can be exploited for remote sensing. In nearly all cases, modern acoustic remote sensing involves array-recorded sounds and array signal processing to recover multidimensional results. The application realm for acoustic remote sensing spans an impressive range of signal frequencies (10-2 to 107 Hz) and distances (10-2 to 107 m) and involves biomedical ultrasound imaging, nondestructive evaluation, oil and gas exploration, military systems, and Nuclear Test Ban Treaty monitoring. In the past two decades, approaches have been developed to robustly localize remote sources; remove noise and multipath distortion from recorded signals; and determine the acoustic characteristics of the environment through which the sound waves have traveled, even when the recorded sounds originate from uncooperative sources or are merely ambient noise.

  17. Acoustic integrated extinction

    PubMed Central

    Norris, Andrew N.

    2015-01-01

    The integrated extinction (IE) is defined as the integral of the scattering cross section as a function of wavelength. Sohl et al. (2007 J. Acoust. Soc. Am. 122, 3206–3210. (doi:10.1121/1.2801546)) derived an IE expression for acoustic scattering that is causal, i.e. the scattered wavefront in the forward direction arrives later than the incident plane wave in the background medium. The IE formula was based on electromagnetic results, for which scattering is causal by default. Here, we derive a formula for the acoustic IE that is valid for causal and non-causal scattering. The general result is expressed as an integral of the time-dependent forward scattering function. The IE reduces to a finite integral for scatterers with zero long-wavelength monopole and dipole amplitudes. Implications for acoustic cloaking are discussed and a new metric is proposed for broadband acoustic transparency. PMID:27547100

  18. Highly directional acoustic receivers.

    PubMed

    Cray, Benjamin A; Evora, Victor M; Nuttall, Albert H

    2003-03-01

    The theoretical directivity of a single combined acoustic receiver, a device that can measure many quantities of an acoustic field at a collocated point, is presented here. The formulation is developed using a Taylor series expansion of acoustic pressure about the origin of a Cartesian coordinate system. For example, the quantities measured by a second-order combined receiver, denoted a dyadic sensor, are acoustic pressure, the three orthogonal components of acoustic particle velocity, and the nine spatial gradients of the velocity vector. The power series expansion, which can be of any order, is cast into an expression that defines the directivity of a single receiving element. It is shown that a single highly directional dyadic sensor can have a directivity index of up to 9.5 dB. However, there is a price to pay with highly directive sensors; these sensors can be significantly more sensitive to nonacoustic noise sources. PMID:12656387

  19. Virtual acoustics displays

    NASA Technical Reports Server (NTRS)

    Wenzel, Elizabeth M.; Fisher, Scott S.; Stone, Philip K.; Foster, Scott H.

    1991-01-01

    The real time acoustic display capabilities are described which were developed for the Virtual Environment Workstation (VIEW) Project at NASA-Ames. The acoustic display is capable of generating localized acoustic cues in real time over headphones. An auditory symbology, a related collection of representational auditory 'objects' or 'icons', can be designed using ACE (Auditory Cue Editor), which links both discrete and continuously varying acoustic parameters with information or events in the display. During a given display scenario, the symbology can be dynamically coordinated in real time with 3-D visual objects, speech, and gestural displays. The types of displays feasible with the system range from simple warnings and alarms to the acoustic representation of multidimensional data or events.

  20. Cochlear bionic acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Ma, Fuyin; Wu, Jiu Hui; Huang, Meng; Fu, Gang; Bai, Changan

    2014-11-01

    A design of bionic acoustic metamaterial and acoustic functional devices was proposed by employing the mammalian cochlear as a prototype. First, combined with the experimental data in previous literatures, it is pointed out that the cochlear hair cells and stereocilia cluster are a kind of natural biological acoustic metamaterials with the negative stiffness characteristics. Then, to design the acoustic functional devices conveniently in engineering application, a simplified parametric helical structure was proposed to replace actual irregular cochlea for bionic design, and based on the computational results of such a bionic parametric helical structure, it is suggested that the overall cochlear is a local resonant system with the negative dynamic effective mass characteristics. There are many potential applications in the bandboard energy recovery device, cochlear implant, and acoustic black hole.

  1. Media Now.

    ERIC Educational Resources Information Center

    Curtis, Ron

    Developed by the Southwest Iowa Learning Resources Center, Media Now is a course for secondary students in media studies. Curriculum concentration is on television, film, radio, and recorded sound. Individualization of instruction, behavioral science, and mediated learning packages are employed with each module interrelated through printed…

  2. Earned Media

    ERIC Educational Resources Information Center

    Sunshine, Alice

    2011-01-01

    "Earned media" is exactly what one thinks it is. The people who do the necessary work to earn coverage of their issue or battle are the ones who will get their story out to the public. Earning media coverage involves giving careful attention to the mechanics of reaching out to news outlets. Most people can learn the mechanics through workshops,…

  3. Mixed Media

    ERIC Educational Resources Information Center

    Peterson, Erin

    2010-01-01

    While institutions do not often have a hook as compelling as an eagerly awaited movie, great content is critical for media relations success--and coupling it with the right distribution channel can ensure the story finds the right audience. Even better, retooling it for several media platforms can extend the life and reach of a story. The changes…

  4. Media Literacy.

    ERIC Educational Resources Information Center

    Potter, W. James

    Written to appeal to a general audience that wants to think more deeply about the nature of the media, their messages, and their effects on both individuals and society, this book serves as a broad introduction to the thinking that ties educators together in the common goal of educating a media literate generation. It is written from a critical…

  5. Ocean seismo-acoustics. Low-frequency underwater acoustics

    SciTech Connect

    Akal, T.; berkson, J.M.

    1986-01-01

    This book presents information on seismo-acoustic propagation in seawater and sea beds that includes theoretical developments, modelling and experiments, and fluctuations. Boundary scatteiring, seismo-acoustic waves and seismo-acoustic noise are discussed. Technology and new approaches in seismo-acoustic measurements are presented.

  6. Refraction of acoustic duct waveguide modes by exhaust jets.

    NASA Technical Reports Server (NTRS)

    Mani, R.

    1973-01-01

    The refraction of acoustic duct waveguide modes emitted from the open end of a semiinfinite rectangular duct by a jet-like exhaust flow is studied theoretically. The problem is formulated as a Wiener-Hopf problem and is ultimately solved by an approximate method due to Carrier and Koiter. Continuity of transverse acoustic particle displacement and of acoustic pressure is assumed at the jet/still-air interface. The solution exhibits several features of the acoustics of moving media such as a source convection effect, zones of relative silence, and simple refraction. Plots of far-field directivity patterns are presented for several cases and show refraction effects to be important even at modest exhaust Mach numbers of order 0.3. Only subsonic exhaust Mach numbers are considered.

  7. Media Publics and Media Trust.

    ERIC Educational Resources Information Center

    Gaziano, Cecilie; McGrath, Kristin

    To gain a perspective on the kinds of people who find newspapers and television to be high or low in credibility, a two-phase study combined demographic and other characteristics, media behavior, and attitudes toward the media. The first phase involved a series of focused group discussions, while the second was a national, representative sampling…

  8. Media violence.

    PubMed

    Cantor, J

    2000-08-01

    Research on the effects of media violence is not well understood by the general public. Despite this fact, there is an overwhelming consensus in the scientific literature about the unhealthy effects of media violence. Meta-analyses show that media-violence viewing consistently is associated with higher levels of antisocial behavior, ranging from the trivial (imitative violence directed against toys) to the serious (criminal violence), with many consequential outcomes in between (acceptance of violence as a solution to problems, increased feelings of hostility, and the apparent delivery of painful stimulation to another person). Desensitization is another well-documented effect of viewing violence, which is observable in reduced arousal and emotional disturbance while witnessing violence, the reduced tendency to intervene in a fight, and less sympathy for the victims of violence. Although there is evidence that youth who are already violent are more likely to seek out violent entertainment, there is strong evidence that the relationship between violence viewing and antisocial behavior is bidirectional. There is growing evidence that media violence also engenders intense fear in children which often lasts days, months, and even years. The media's potential role in solutions to these problems is only beginning to be explored, in investigations examining the uses and effects of movie ratings, television ratings, and the V-chip, and the effects of media literacy programs and public education efforts. Future research should explore important individual differences in responses to media violence and effective ways to intervene in the negative effects. PMID:10904203

  9. Acoustic cooling engine

    DOEpatents

    Hofler, Thomas J.; Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1988-01-01

    An acoustic cooling engine with improved thermal performance and reduced internal losses comprises a compressible fluid contained in a resonant pressure vessel. The fluid has a substantial thermal expansion coefficient and is capable of supporting an acoustic standing wave. A thermodynamic element has first and second ends and is located in the resonant pressure vessel in thermal communication with the fluid. The thermal response of the thermodynamic element to the acoustic standing wave pumps heat from the second end to the first end. The thermodynamic element permits substantial flow of the fluid through the thermodynamic element. An acoustic driver cyclically drives the fluid with an acoustic standing wave. The driver is at a location of maximum acoustic impedance in the resonant pressure vessel and proximate the first end of the thermodynamic element. A hot heat exchanger is adjacent to and in thermal communication with the first end of the thermodynamic element. The hot heat exchanger conducts heat from the first end to portions of the resonant pressure vessel proximate the hot heat exchanger. The hot heat exchanger permits substantial flow of the fluid through the hot heat exchanger. The resonant pressure vessel can include a housing less than one quarter wavelength in length coupled to a reservoir. The housing can include a reduced diameter portion communicating with the reservoir. The frequency of the acoustic driver can be continuously controlled so as to maintain resonance.

  10. Acoustic mapping velocimetry

    NASA Astrophysics Data System (ADS)

    Muste, M.; Baranya, S.; Tsubaki, R.; Kim, D.; Ho, H.; Tsai, H.; Law, D.

    2016-05-01

    Knowledge of sediment dynamics in rivers is of great importance for various practical purposes. Despite its high relevance in riverine environment processes, the monitoring of sediment rates remains a major and challenging task for both suspended and bed load estimation. While the measurement of suspended load is currently an active area of testing with nonintrusive technologies (optical and acoustic), bed load measurement does not mark a similar progress. This paper describes an innovative combination of measurement techniques and analysis protocols that establishes the proof-of-concept for a promising technique, labeled herein Acoustic Mapping Velocimetry (AMV). The technique estimates bed load rates in rivers developing bed forms using a nonintrusive measurements approach. The raw information for AMV is collected with acoustic multibeam technology that in turn provides maps of the bathymetry over longitudinal swaths. As long as the acoustic maps can be acquired relatively quickly and the repetition rate for the mapping is commensurate with the movement of the bed forms, successive acoustic maps capture the progression of the bed form movement. Two-dimensional velocity maps associated with the bed form migration are obtained by implementing algorithms typically used in particle image velocimetry to acoustic maps converted in gray-level images. Furthermore, use of the obtained acoustic and velocity maps in conjunction with analytical formulations (e.g., Exner equation) enables estimation of multidirectional bed load rates over the whole imaged area. This paper presents a validation study of the AMV technique using a set of laboratory experiments.

  11. Acoustic levitation methods for density measurements

    NASA Astrophysics Data System (ADS)

    Trinh, E. H.; Hsu, C. J.

    1986-12-01

    The capability of ultrasonic levitators operating in air to perform density measurements has been demonstrated. The remote determination of the density of ordinary liquids as well as low density solid metals can be carried out using levitated samples with size on the order of a few millimeters and at a frequency of 20 kHz. Two basic methods may be used. The first one is derived from a previously known technique developed for acoustic levitation in liquid media, and is based on the static equilibrium position of levitated samples in the earth's gravitational field. The second approach relies on the dynamic interaction between a levitated sample and the acoustic field. The first technique appears more accurate (1 percent uncertainty), but the latter method is directly applicable to a near gravity-free environment such as that found in space.

  12. Acoustic levitation methods for density measurements

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Hsu, C. J.

    1986-01-01

    The capability of ultrasonic levitators operating in air to perform density measurements has been demonstrated. The remote determination of the density of ordinary liquids as well as low density solid metals can be carried out using levitated samples with size on the order of a few millimeters and at a frequency of 20 kHz. Two basic methods may be used. The first one is derived from a previously known technique developed for acoustic levitation in liquid media, and is based on the static equilibrium position of levitated samples in the earth's gravitational field. The second approach relies on the dynamic interaction between a levitated sample and the acoustic field. The first technique appears more accurate (1 percent uncertainty), but the latter method is directly applicable to a near gravity-free environment such as that found in space.

  13. Some Problems of modern acoustics

    NASA Technical Reports Server (NTRS)

    Stan, A.

    1974-01-01

    The multidisciplinary and interdisciplinary character of acoustics is considered and its scientific, technological, economical and social implications, as well as the role of acoustics in creating new machines and equipment and improving the quality of products are outlined. Research beyond audible frequencies, as well as to extremely high acoustic intensities, which requires the development of a nonlinear acoustics is elaborated.

  14. Acoustic rotation control

    NASA Technical Reports Server (NTRS)

    Elleman, D. D.; Croonquist, A. P.; Wang, T. G. (Inventor)

    1983-01-01

    A system is described for acoustically controlled rotation of a levitated object, which avoids deformation of a levitated liquid object. Acoustic waves of the same wavelength are directed along perpendicular directions across the object, and with the relative phases of the acoustic waves repeatedly switched so that one wave alternately leads and lags the other by 90 deg. The amount of torque for rotating the object, and the direction of rotation, are controlled by controlling the proportion of time one wave leads the other and selecting which wave leads the other most of the time.

  15. PRSEUS Acoustic Panel Fabrication

    NASA Technical Reports Server (NTRS)

    Nicolette, Velicki; Yovanof, Nicolette P.; Baraja, Jaime; Mathur, Gopal; Thrash, Patrick; Pickell, Robert

    2011-01-01

    This report describes the development of a novel structural concept, Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS), that addresses the demanding fuselage loading requirements for the Hybrid Wing or Blended Wing Body (BWB) airplane configuration with regards to acoustic response. A PRSEUS panel was designed and fabricated and provided to NASA-LaRC for acoustic response testing in the Structural Acoustics Loads and Transmission (SALT) facility). Preliminary assessments of the sound transmission characteristics of a PRSEUS panel subjected to a representative Hybrid Wing Body (HWB) operating environment were completed for the NASA Environmentally Responsible Aviation (ERA) Program.

  16. Acoustic well cleaner

    DOEpatents

    Maki, Jr., Voldi E.; Sharma, Mukul M.

    1997-01-21

    A method and apparatus are disclosed for cleaning the wellbore and the near wellbore region. A sonde is provided which is adapted to be lowered into a borehole and which includes a plurality of acoustic transducers arranged around the sonde. Electrical power provided by a cable is converted to acoustic energy. The high intensity acoustic energy directed to the borehole wall and into the near wellbore region, redissolves or resuspends the material which is reducing the permeability of the formation and/or restricting flow in the wellbore.

  17. Acoustical heat pumping engine

    DOEpatents

    Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1983-08-16

    The disclosure is directed to an acoustical heat pumping engine without moving seals. A tubular housing holds a compressible fluid capable of supporting an acoustical standing wave. An acoustical driver is disposed at one end of the housing and the other end is capped. A second thermodynamic medium is disposed in the housing near to but spaced from the capped end. Heat is pumped along the second thermodynamic medium toward the capped end as a consequence both of the pressure oscillation due to the driver and imperfect thermal contact between the fluid and the second thermodynamic medium.

  18. Acoustical heat pumping engine

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1983-08-16

    The disclosure is directed to an acoustical heat pumping engine without moving seals. A tubular housing holds a compressible fluid capable of supporting an acoustical standing wave. An acoustical driver is disposed at one end of the housing and the other end is capped. A second thermodynamic medium is disposed in the housing near to but spaced from the capped end. Heat is pumped along the second thermodynamic medium toward the capped end as a consequence both of the pressure oscillation due to the driver and imperfect thermal contact between the fluid and the second thermodynamic medium. 2 figs.

  19. From Augmentation Media to Meme Media.

    ERIC Educational Resources Information Center

    Tanaka, Yuzuru

    Computers as meta media are now evolving from augmentation media vehicles to meme media vehicles. While an augmentation media system provides a seamlessly integrated environment of various tools and documents, meme media system provides further functions to edit and distribute tools and documents. Documents and tools on meme media can easily…

  20. Media violence.

    PubMed

    Willis, E; Strasburger, V C

    1998-04-01

    American media are the most violent in the world, and American society is now paying a high price in terms of real life violence. Research has confirmed that mass media violence contributes to aggressive behavior, fear, and desensitization of violence. Television, movies, music videos, computer/video games are pervasive media and represent important influences on children and adolescents. Portraying rewards and punishments and showing the consequences of violence are probably the two most essential contextual factors for viewers as they interpret the meaning of what they are viewing on television. Public health efforts have emphasized public education, media literacy campaign for children and parents, and an increased use of technology to prevent access to certain harmful medial materials. PMID:9568012

  1. Acoustics lecturing in Mexico

    NASA Astrophysics Data System (ADS)

    Beristain, Sergio

    2002-11-01

    Some thirty years ago acoustics lecturing started in Mexico at the National Polytechnic Institute in Mexico City, as part of the Bachelor of Science degree in Communications and Electronics Engineering curricula, including the widest program on this field in the whole country. This program has been producing acoustics specialists ever since. Nowadays many universities and superior education institutions around the country are teaching students at the B.Sc. level and postgraduate level many topics related to acoustics, such as Architectural Acoustics, Seismology, Mechanical Vibrations, Noise Control, Audio, Audiology, Music, etc. Also many institutions have started research programs in related fields, with participation of medical doctors, psychologists, musicians, engineers, etc. Details will be given on particular topics and development.

  2. Acoustic Neuroma Association

    MedlinePlus

    ... Platinum Sponsors More from this sponsor... Platinum Sponsor Gold Sponsor University of Colorado Acoustic Neuroma Program Rocky Mountain Gamma Knife Center Gold Sponsor NYU Langone Medical Center Departments of Neurosurgery ...

  3. Compact acoustic refrigerator

    DOEpatents

    Bennett, Gloria A.

    1992-01-01

    A compact acoustic refrigeration system actively cools components, e.g., electrical circuits (22), in a borehole environment. An acoustic engine (12, 14) includes first thermodynamic elements (12) for generating a standing acoustic wave in a selected medium. An acoustic refrigerator (16, 26, 28) includes second thermodynamic elements (16) located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements (16) and a relatively hot temperature at a second end of the second thermodynamic elements (16). A resonator volume (18) cooperates with the first and second thermodynamic elements (12, 16) to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements (12, 16), first heat pipes (24, 26) transfer heat from the heat load (22) to the second thermodynamic elements (16) and second heat pipes (28, 32) transfer heat from first and second thermodynamic elements (12, 16) to the borehole environment.

  4. Compact acoustic refrigerator

    DOEpatents

    Bennett, G.A.

    1992-11-24

    A compact acoustic refrigeration system actively cools components, e.g., electrical circuits, in a borehole environment. An acoustic engine includes first thermodynamic elements for generating a standing acoustic wave in a selected medium. An acoustic refrigerator includes second thermodynamic elements located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements and a relatively hot temperature at a second end of the second thermodynamic elements. A resonator volume cooperates with the first and second thermodynamic elements to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements, first heat pipes transfer heat from the heat load to the second thermodynamic elements and second heat pipes transfer heat from first and second thermodynamic elements to the borehole environment. 18 figs.

  5. Compact acoustic refrigerator

    SciTech Connect

    Bennett, G.A.

    1991-12-31

    This invention is comprised of a compact acoustic refrigeration system that actively cools components, e.g., electrical circuits, in a borehole environment. An acoustic engine includes first thermodynamic elements for generating a standing acoustic wave in a selected medium. An acoustic refrigerator includes second thermodynamic elements located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements and a relatively hot temperature at a second end of the second thermodynamic elements. A resonator volume cooperates with the first and second thermodynamic elements to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements, first heat pipes transfer heat from the heat load to the second thermodynamic elements and second heat pipes transfer heat from first and second thermodynamic elements to the borehole environment.

  6. Acoustic imaging system

    DOEpatents

    Smith, Richard W.

    1979-01-01

    An acoustic imaging system for displaying an object viewed by a moving array of transducers as the array is pivoted about a fixed point within a given plane. A plurality of transducers are fixedly positioned and equally spaced within a laterally extending array and operatively directed to transmit and receive acoustic signals along substantially parallel transmission paths. The transducers are sequentially activated along the array to transmit and receive acoustic signals according to a preestablished sequence. Means are provided for generating output voltages for each reception of an acoustic signal, corresponding to the coordinate position of the object viewed as the array is pivoted. Receptions from each of the transducers are presented on the same display at coordinates corresponding to the actual position of the object viewed to form a plane view of the object scanned.

  7. Numerical Techniques in Acoustics

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J. (Compiler)

    1985-01-01

    This is the compilation of abstracts of the Numerical Techniques in Acoustics Forum held at the ASME's Winter Annual Meeting. This forum was for informal presentation and information exchange of ongoing acoustic work in finite elements, finite difference, boundary elements and other numerical approaches. As part of this forum, it was intended to allow the participants time to raise questions on unresolved problems and to generate discussions on possible approaches and methods of solution.

  8. Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface.

    PubMed

    Xie, Yangbo; Wang, Wenqi; Chen, Huanyang; Konneker, Adam; Popa, Bogdan-Ioan; Cummer, Steven A

    2014-01-01

    Metasurfaces are a family of novel wavefront-shaping devices with planar profile and subwavelength thickness. Acoustic metasurfaces with ultralow profile yet extraordinary wave manipulating properties would be highly desirable for improving the performance of many acoustic wave-based applications. However, designing acoustic metasurfaces with similar functionality to their electromagnetic counterparts remains challenging with traditional metamaterial design approaches. Here we present a design and realization of an acoustic metasurface based on tapered labyrinthine metamaterials. The demonstrated metasurface can not only steer an acoustic beam as expected from the generalized Snell's law, but also exhibits various unique properties such as conversion from propagating wave to surface mode, extraordinary beam-steering and apparent negative refraction through higher-order diffraction. Such designer acoustic metasurfaces provide a new design methodology for acoustic signal modulation devices and may be useful for applications such as acoustic imaging, beam steering, ultrasound lens design and acoustic surface wave-based applications. PMID:25418084

  9. Acoustic flowmeters: Their applications in hydraulics

    NASA Astrophysics Data System (ADS)

    Nitzsche, Ulf

    Flowmeter installations for viscous and high hydrostatic pressure media are developed. Their usability is considered for characteristic measuring tasks in the field of oil hydraulics. The properties of flow sensors are evaluated by system analysis. Acoustic measuring systems are preferred. Two ultrasonic flowmeters are realized. Simulation models, installation with piezoceramic material parameters, and sound visualization support these developments. A computer aided hydraulic test stand is developed in order to detect the measuring characteristics of this system. Flowmeter applications are shown using the identification of the static and dynamic parameters of an electrohydraulic pilot valve.

  10. Acoustic communication by ants

    NASA Astrophysics Data System (ADS)

    Hickling, Robert

    2002-05-01

    Many ant species communicate acoustically by stridulating, i.e., running a scraper over a washboard-like set of ridges. Ants appear to be insensitive to airborne sound. Consequently, myrmecologists have concluded that the stridulatory signals are transmitted through the substrate. This has tended to diminish the importance of acoustic communication, and it is currently believed that ant communication is based almost exclusively on pheromones, with acoustic communication assigned an almost nonexistent role. However, it can be shown that acoustic communication between ants is effective only if the medium is air and not the substrate. How, then, is it possible for ants to appear deaf to airborne sound and yet communicate through the air? An explanation is provided in a paper [R. Hickling and R. L. Brown, ``Analysis of acoustic communication by ants,'' J. Acoust. Soc. Am. 108, 1920-1929 (2000)]. Ants are small relative to the wavelengths they generate. Hence, they create a near field, which is characterized by a major increase in sound velocity (particle velocity of sound) in the vicinity of the source. Hair sensilla on the ants' antennae respond to sound velocity. Thus, ants are able to detect near-field sound from other ants and to exclude extraneous airborne sound.

  11. Ocean acoustic reverberation tomography.

    PubMed

    Dunn, Robert A

    2015-12-01

    Seismic wide-angle imaging using ship-towed acoustic sources and networks of ocean bottom seismographs is a common technique for exploring earth structure beneath the oceans. In these studies, the recorded data are dominated by acoustic waves propagating as reverberations in the water column. For surveys with a small receiver spacing (e.g., <10 km), the acoustic wave field densely samples properties of the water column over the width of the receiver array. A method, referred to as ocean acoustic reverberation tomography, is developed that uses the travel times of direct and reflected waves to image ocean acoustic structure. Reverberation tomography offers an alternative approach for determining the structure of the oceans and advancing the understanding of ocean heat content and mixing processes. The technique has the potential for revealing small-scale ocean thermal structure over the entire vertical height of the water column and along long survey profiles or across three-dimensional volumes of the ocean. For realistic experimental geometries and data noise levels, the method can produce images of ocean sound speed on a smaller scale than traditional acoustic tomography. PMID:26723303

  12. Acoustic detection of pneumothorax

    NASA Astrophysics Data System (ADS)

    Mansy, Hansen A.; Royston, Thomas J.; Balk, Robert A.; Sandler, Richard H.

    2003-04-01

    This study aims at investigating the feasibility of using low-frequency (<2000 Hz) acoustic methods for medical diagnosis. Several candidate methods of pneumothorax detection were tested in dogs. In the first approach, broadband acoustic signals were introduced into the trachea during end-expiration and transmitted waves were measured at the chest surface. Pneumothorax was found to consistently decrease pulmonary acoustic transmission in the 200-1200-Hz frequency band, while less change was observed at lower frequencies (p<0.0001). The ratio of acoustic energy between low (<220 Hz) and mid (550-770 Hz) frequency bands was significantly different in the control (healthy) and pneumothorax states (p<0.0001). The second approach measured breath sounds in the absence of an external acoustic input. Pneumothorax was found to be associated with a preferential reduction of sound amplitude in the 200- to 700-Hz range, and a decrease of sound amplitude variation (in the 300 to 600-Hz band) during the respiration cycle (p<0.01 for each). Finally, chest percussion was implemented. Pneumothorax changed the frequency and decay rate of percussive sounds. These results imply that certain medical conditions may be reliably detected using appropriate acoustic measurements and analysis. [Work supported by NIH/NHLBI #R44HL61108.

  13. Phase behaviour and phase separation kinetics measurement using acoustic arrays

    NASA Astrophysics Data System (ADS)

    Khammar, M.; Shaw, J. M.

    2011-10-01

    Speed of sound and acoustic wave attenuation are sensitive to fluid phase composition and to the presence of liquid-liquid interfaces. In this work, the use of an acoustic array comprising 64 elements as a non-intrusive sensor for liquid-liquid interface, phase separation kinetics measurement in bulk fluids, and local composition measurement in porous media is illustrated. Three benchmark examples: the phase behaviour of methanol + mixed hexanes and methanol + heptane mixtures at 25.0 °C and 1 bar, and Athabasca bitumen + heptane in a synthetic silica porous medium at 22.5 °C and 1 bar, illustrate the accuracy of liquid-liquid interface and potential research and industrial applications of the technique. Liquid-liquid interfaces can be detected independently using both speed of sound and acoustic wave attenuation measurements. The precision of the interface location measurement is 300 μm. As complete scans can be performed at a rate of 1 Hz, phase separation kinetics and diffusion of liquids within porous media are readily tracked. The technique is expected to find application where the fluids or porous media are opaque to visible light and where other imaging techniques are not readily applied, or are too costly. A current limitation is that the acoustic probes must be cooled to less than 315 K in order for them to operate.

  14. Acoustic calibration apparatus for calibrating plethysmographic acoustic pressure sensors

    NASA Technical Reports Server (NTRS)

    Zuckerwar, Allan J. (Inventor); Davis, David C. (Inventor)

    1995-01-01

    An apparatus for calibrating an acoustic sensor is described. The apparatus includes a transmission material having an acoustic impedance approximately matching the acoustic impedance of the actual acoustic medium existing when the acoustic sensor is applied in actual in-service conditions. An elastic container holds the transmission material. A first sensor is coupled to the container at a first location on the container and a second sensor coupled to the container at a second location on the container, the second location being different from the first location. A sound producing device is coupled to the container and transmits acoustic signals inside the container.

  15. Program in acoustics. [aeroacoustics, aircraft noise, and noise suppression

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Relevant research projects conducted by faculty and graduate students in the general area of aeroacoustics to further the understanding of noise generation by aircraft and to aid in the development of practical methods for noise suppression are listed. Special activities summarized relate to the nonlinear acoustic wave theory and its application to several cases including that of the acoustic source located at the throat of a near-sonic duct, a computer program developed to compute the nonlinear wave theory, and a parabolic approximation for propagation of sounding in moving stratified media.

  16. Measuring acoustic habitats

    PubMed Central

    Merchant, Nathan D; Fristrup, Kurt M; Johnson, Mark P; Tyack, Peter L; Witt, Matthew J; Blondel, Philippe; Parks, Susan E

    2015-01-01

    1. Many organisms depend on sound for communication, predator/prey detection and navigation. The acoustic environment can therefore play an important role in ecosystem dynamics and evolution. A growing number of studies are documenting acoustic habitats and their influences on animal development, behaviour, physiology and spatial ecology, which has led to increasing demand for passive acoustic monitoring (PAM) expertise in the life sciences. However, as yet, there has been no synthesis of data processing methods for acoustic habitat monitoring, which presents an unnecessary obstacle to would-be PAM analysts. 2. Here, we review the signal processing techniques needed to produce calibrated measurements of terrestrial and aquatic acoustic habitats. We include a supplemental tutorial and template computer codes in matlab and r, which give detailed guidance on how to produce calibrated spectrograms and statistical analyses of sound levels. Key metrics and terminology for the characterisation of biotic, abiotic and anthropogenic sound are covered, and their application to relevant monitoring scenarios is illustrated through example data sets. To inform study design and hardware selection, we also include an up-to-date overview of terrestrial and aquatic PAM instruments. 3. Monitoring of acoustic habitats at large spatiotemporal scales is becoming possible through recent advances in PAM technology. This will enhance our understanding of the role of sound in the spatial ecology of acoustically sensitive species and inform spatial planning to mitigate the rising influence of anthropogenic noise in these ecosystems. As we demonstrate in this work, progress in these areas will depend upon the application of consistent and appropriate PAM methodologies. PMID:25954500

  17. 2-D acoustic VTI full waveform inversion for CCS monitoring

    NASA Astrophysics Data System (ADS)

    KIM, S.; Kim, W. K.; Min, D. J.; Jeong, W.; OH, J. W.

    2014-12-01

    These days many geophysicists have been working not only for oil and gas exploration but also for CO2 monitoring for CCS (Carbon Capture and storage). When CO2 is injected and stored to the target layer, it changes the physical properties of subsurface media like p-wave velocity, density and so on. Seismic method is one of the most widely used geophysical methods for CO2 monitoring, because it can delineate physical properties of subsurface media. To prevent CO2 from leaking out of reservoirs, most target areas require caprocks, and shale often acts as a caprock. However, shale has a strong anisotropic property. Without considering the anisotropic property of subsurface media, interpretations of seismic monitoring data can distort the CO2distribution or movement in the subsurface media. For computational efficiency, seismic data interpretation based on acoustic VTI (Vertical Transversely Isotropic) wave equations has been commonly done although it does not consider the shear waves. To investigate the importance of considering anisotropic properties in acoustic FWI (full waveform inversion) for CO2 monitoring, we compare results obtained by the acoustic VTI FWI with those of the conventional acoustic FWI for isotropic case in the frequency domain. Both methods are based on the node-based finite-element method. Numerical examples show that neglecting anisotropic properties of subsurface media can distort distribution of CO2 and degrade reliability of subsurface image obtained by FWI. Acknowledgements This work was supported by the Human Resources Development program (No. 20134010200510) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korean government Ministry of Trade, Industry, and Energy and by the "Development of Technology for CO2 Marine Geological Storage" grant funded by the Ministry of Oceans and Fisheries of Korea.

  18. Media Training

    SciTech Connect

    2009-12-11

    With the LHC starting up soon, the world's media are again turning their attention to CERN. We're all likely to be called upon to explain what is happening at CERN to media, friends and neighbours. The seminar will be given by BBC television news journalists Liz Pike and Nadia Marchant, and will deal with the kind of questions we're likely to be confronted with through the restart period. The training is open for everybody. Make sure you arrive early enough to get a seat - there are only 200 seats in the Globe. The session will also be webcast: http://webcast.cern.ch/

  19. Media Training

    ScienceCinema

    None

    2011-10-06

    With the LHC starting up soon, the world's media are again turning their attention to CERN. We're all likely to be called upon to explain what is happening at CERN to media, friends and neighbours. The seminar will be given by BBC television news journalists Liz Pike and Nadia Marchant, and will deal with the kind of questions we're likely to be confronted with through the restart period. The training is open for everybody. Make sure you arrive early enough to get a seat - there are only 200 seats in the Globe. The session will also be webcast: http://webcast.cern.ch/

  20. Acoustics and precondensation phenomena in gas-vapor saturated mixtures.

    PubMed

    Guianvarc'h, C; Bruneau, M; Gavioso, R M

    2014-02-01

    Starting from fundamental hydrodynamics and thermodynamics equations for thermoviscous fluids, a new modeling procedure, which is suitable to describe acoustic propagation in gas mixtures, is presented. The model revises the boundary conditions which are appropriate to describe the condensation-evaporation processes taking place on a solid wall when one component of the mixture approaches saturation conditions. The general analytical solutions of these basic equations now give a unified description of acoustic propagation in an infinite, semi-infinite, or finite medium, throughout and beyond the boundary layers. The solutions account for the coupling between acoustic propagation and heat and concentration diffusion processes, including precondensation on the walls. The validity of the model and its predictive capability have been tested by a comparison with the description available in the literature of two particular systems (precondensation of propane and acoustic attenuation in a duct filled with an air-water vapor saturated mixture). The results of this comparison are discussed to clarify the relevance of the various physical phenomena that are involved in these processes. The model proposed here might be useful to develop methods for the acoustic determination of the thermodynamic and transport properties of gas mixtures as well as for practical applications involving gas and gas-vapor mixtures like thermoacoustics and acoustics in wet granular or porous media. PMID:25353596

  1. Acoustics and precondensation phenomena in gas-vapor saturated mixtures

    NASA Astrophysics Data System (ADS)

    Guianvarc'h, C.; Bruneau, M.; Gavioso, R. M.

    2014-02-01

    Starting from fundamental hydrodynamics and thermodynamics equations for thermoviscous fluids, a new modeling procedure, which is suitable to describe acoustic propagation in gas mixtures, is presented. The model revises the boundary conditions which are appropriate to describe the condensation-evaporation processes taking place on a solid wall when one component of the mixture approaches saturation conditions. The general analytical solutions of these basic equations now give a unified description of acoustic propagation in an infinite, semi-infinite, or finite medium, throughout and beyond the boundary layers. The solutions account for the coupling between acoustic propagation and heat and concentration diffusion processes, including precondensation on the walls. The validity of the model and its predictive capability have been tested by a comparison with the description available in the literature of two particular systems (precondensation of propane and acoustic attenuation in a duct filled with an air-water vapor saturated mixture). The results of this comparison are discussed to clarify the relevance of the various physical phenomena that are involved in these processes. The model proposed here might be useful to develop methods for the acoustic determination of the thermodynamic and transport properties of gas mixtures as well as for practical applications involving gas and gas-vapor mixtures like thermoacoustics and acoustics in wet granular or porous media.

  2. Ultrasound-modulated optical tomography with intense acoustic bursts

    NASA Astrophysics Data System (ADS)

    Zemp, Roger J.; Kim, Chulhong; Wang, Lihong V.

    2007-04-01

    Ultrasound-modulated optical tomography (UOT) detects ultrasonically modulated light to spatially localize multiply scattered photons in turbid media with the ultimate goal of imaging the optical properties in living subjects. A principal challenge of the technique is weak modulated signal strength. We discuss ways to push the limits of signal enhancement with intense acoustic bursts while conforming to optical and ultrasonic safety standards. A CCD-based speckle-contrast detection scheme is used to detect acoustically modulated light by measuring changes in speckle statistics between ultrasound-on and ultrasound-off states. The CCD image capture is synchronized with the ultrasound burst pulse sequence. Transient acoustic radiation force, a consequence of bursts, is seen to produce slight signal enhancement over pure ultrasonic-modulation mechanisms for bursts and CCD exposure times of the order of milliseconds. However, acoustic radiation-force-induced shear waves are launched away from the acoustic sample volume, which degrade UOT spatial resolution. By time gating the CCD camera to capture modulated light before radiation force has an opportunity to accumulate significant tissue displacement, we reduce the effects of shear-wave image degradation, while enabling very high signal-to-noise ratios. Additionally, we maintain high-resolution images representative of optical and not mechanical contrast. Signal-to-noise levels are sufficiently high so as to enable acquisition of 2D images of phantoms with one acoustic burst per pixel.

  3. Modifying the acoustic impedance of polyurea-based composites

    NASA Astrophysics Data System (ADS)

    Nantasetphong, Wiroj; Amirkhizi, Alireza V.; Jia, Zhanzhan; Nemat-Nasser, Sia

    2013-04-01

    Acoustic impedance is a material property that depends on mass density and acoustic wave speed. An impedance mismatch between two media leads to the partial reflection of an acoustic wave sent from one medium to another. Active sonar is one example of a useful application of this phenomenon, where reflected and scattered acoustic waves enable the detection of objects. If the impedance of an object is matched to that of the surrounding medium, however, the object may be hidden from observation (at least directly) by sonar. In this study, polyurea composites are developed to facilitate such impedance matching. Polyurea is used due to its excellent blast-mitigating properties, easy casting, corrosion protection, abrasion resistance, and various uses in current military technology. Since pure polyurea has impedance higher than that of water (the current medium of interest), low mass density phenolic microballoon particles are added to create composite materials with reduced effective impedances. The volume fraction of particles is varied to study the effect of filler quantity on the acoustic impedance of the resulting composite. The composites are experimentally characterized via ultrasonic measurements. Computational models based on the method of dilute-randomly-distributed inclusions are developed and compared with the experimental results. These experiments and models will facilitate the design of new elastomeric composites with desirable acoustic impedances.

  4. Scanning Tomographic Acoustic Microscopy

    NASA Astrophysics Data System (ADS)

    Wade, G.; Meyyappan, A.

    1988-07-01

    The technology for "seeing" with sound has an important and interesting history. Some of nature's creatures have been using sound waves for many millenia to image otherwise unobservable objects. The human species, lacking this natural ability, have overcome this deficiency by developing several different ultrasonic imaging techniques. acoustic microscopy is one such technique, which produces high resolution images of detailed structure of small objects in a non-destructive fashion. Two types of acoustic microscopes have evolved for industrial exploitation. They are the scanning laser acoustic microscope (SLAM) and the scanning acoustic microscope (SAM). In this paper, we review the principles of SLAM and describe how we use elements of SLAM to realize the scanning tomographic acoustic microscope (STAM). We describe the data acquisition process and the image reconstruction procedure. We also describe techniques to obtain projection data from different angles of wave incidence enabling us to reconstruct different planes of a complex specimen tomo-graphically. Our experimental results show that STAM is capable of producing high-quality high-resolution subsurface images.

  5. Acoustic emission monitoring system

    DOEpatents

    Romrell, Delwin M.

    1977-07-05

    Methods and apparatus for identifying the source location of acoustic emissions generated within an acoustically conductive medium. A plurality of acoustic receivers are communicably coupled to the surface of the medium at a corresponding number of spaced locations. The differences in the reception time of the respective sensors in response to a given acoustic event are measured among various sensor combinations prescribed by the monitoring mode employed. Acoustic reception response encountered subsequent to the reception by a predetermined number of the prescribed sensor combinations are inhibited from being communicated to the processing circuitry, while the time measurements obtained from the prescribed sensor combinations are translated into a position measurement representative of the location on the surface most proximate the source of the emission. The apparatus is programmable to function in six separate and five distinct operating modes employing either two, three or four sensory locations. In its preferred arrangement the apparatus of this invention will re-initiate a monitoring interval if the predetermined number of sensors do not respond to a particular emission within a given time period.

  6. Acoustic properties of low growing plants.

    PubMed

    Horoshenkov, Kirill V; Khan, Amir; Benkreira, Hadj

    2013-05-01

    The plane wave normal incidence acoustic absorption coefficient of five types of low growing plants is measured in the presence and absence of soil. These plants are generally used in green living walls and flower beds. Two types of soil are considered in this work: a light-density, man-made soil and a heavy-density natural clay base soil. The absorption coefficient data are obtained in the frequency range of 50-1600 Hz using a standard impedance tube of diameter 100 mm. The equivalent fluid model for sound propagation in rigid frame porous media proposed by Miki [J. Acoust. Soc. Jpn. (E) 11, 25-28 (1990)] is used to predict the experimentally observed behavior of the absorption coefficient spectra of soils, plants, and their combinations. Optimization analysis is employed to deduce the effective flow resistivity and tortuosity of plants which are assumed to behave acoustically as an equivalent fluid in a rigid frame porous medium. It is shown that the leaf area density and dominant angle of leaf orientation are two key morphological characteristics which can be used to predict accurately the effective flow resistivity and tortuosity of plants. PMID:23654364

  7. ACOUSTICS IN ARCHITECTURAL DESIGN, AN ANNOTATED BIBLIOGRAPHY ON ARCHITECTURAL ACOUSTICS.

    ERIC Educational Resources Information Center

    DOELLE, LESLIE L.

    THE PURPOSE OF THIS ANNOTATED BIBLIOGRAPHY ON ARCHITECTURAL ACOUSTICS WAS--(1) TO COMPILE A CLASSIFIED BIBLIOGRAPHY, INCLUDING MOST OF THOSE PUBLICATIONS ON ARCHITECTURAL ACOUSTICS, PUBLISHED IN ENGLISH, FRENCH, AND GERMAN WHICH CAN SUPPLY A USEFUL AND UP-TO-DATE SOURCE OF INFORMATION FOR THOSE ENCOUNTERING ANY ARCHITECTURAL-ACOUSTIC DESIGN…

  8. Streaming Media

    ERIC Educational Resources Information Center

    Pulley, John

    2009-01-01

    At a time when the evolutionary pace of new media resembles the real-time mutation of certain microorganisms, the age-old question of how best to connect with constituents can seem impossibly complex--even for an elite institution plugged into the motherboard of Silicon Valley. Identifying the most effective vehicle for reaching a particular…

  9. Media Matters

    ERIC Educational Resources Information Center

    Cooper, Kenneth J.; Pyrillis, Rita; Rosario, Ruben; Stuart, Reginald; Zinngrabe, Elaine

    2007-01-01

    This article presents five vignettes, written by veteran journalists, that focus on the current and future state of journalism. Despite almost daily reports of media consolidation and newspaper layoffs, the journalists sound a cautionary but optimistic tone about the industry. They weigh in on everything from the threats to diversity to the future…

  10. Latticed pentamode acoustic cloak

    PubMed Central

    Chen, Yi; Liu, Xiaoning; Hu, Gengkai

    2015-01-01

    We report in this work a practical design of pentamode acoustic cloak with microstructure. The proposed cloak is assembled by pentamode lattice made of a single-phase solid material. The function of rerouting acoustic wave round an obstacle has been demonstrated numerically. It is also revealed that shear related resonance due to weak shear resistance in practical pentamode lattices punctures broadband feature predicted based on ideal pentamode cloak. As a consequence, the latticed pentamode cloak can only conceal the obstacle in segmented frequency ranges. We have also shown that the shear resonance can be largely reduced by introducing material damping, and an improved broadband performance can be achieved. These works pave the way for experimental demonstration of pentamode acoustic cloak. PMID:26503821

  11. Acoustic energy shaping

    NASA Technical Reports Server (NTRS)

    Wang, T. G.; Elleman, D. D. (Inventor)

    1977-01-01

    A suspended mass is shaped by melting all or a selected portion of the mass and applying acoustic energy in varying amounts to different portions of the mass. In one technique for forming an optical waveguide slug, a mass of oval section is suspended and only a portion along the middle of the cross-section is heated to a largely fluid consistency. Acoustic energy is applied to opposite edges of the oval mass to press the unheated opposite edge portions together so as to form bulges at the middle of the mass. In another technique for forming a ribbon of silicon for constructing solar cells, a cylindrical thread of silicon is drawn from a molten mass of silicon, and acoustic energy is applied to opposite sides of the molten thread to flatten it into a ribbon.

  12. Passive broadband acoustic thermometry

    NASA Astrophysics Data System (ADS)

    Anosov, A. A.; Belyaev, R. V.; Klin'shov, V. V.; Mansfel'd, A. D.; Subochev, P. V.

    2016-04-01

    The 1D internal (core) temperature profiles for the model object (plasticine) and the human hand are reconstructed using the passive acoustothermometric broadband probing data. Thermal acoustic radiation is detected by a broadband (0.8-3.5 MHz) acoustic radiometer. The temperature distribution is reconstructed using a priori information corresponding to the experimental conditions. The temperature distribution for the heated model object is assumed to be monotonic. For the hand, we assume that the temperature distribution satisfies the heat-conduction equation taking into account the blood flow. The average error of reconstruction determined for plasticine from the results of independent temperature measurements is 0.6 K for a measuring time of 25 s. The reconstructed value of the core temperature of the hand (36°C) generally corresponds to physiological data. The obtained results make it possible to use passive broadband acoustic probing for measuring the core temperatures in medical procedures associated with heating of human organism tissues.

  13. Seamount acoustic scattering

    NASA Astrophysics Data System (ADS)

    Boehlert, George W.

    The cover of the March 1 issue of Eos showed a time series of acoustic scattering above Southeast Hancock Seamount (29°48‧N, 178°05‧E) on July 17-18, 1984. In a comment on that cover Martin Hovland (Eos, August 2, p. 760) argued that gas or “other far reaching causes” may be involved in the observed acoustic signals. He favors a hypothesis that acoustic scattering observed above a seeping pockmark in the North Sea is a combination of bubbles, stable microbubbles, and pelagic organisms and infers that this may be a more general phenomenon and indeed plays a role in the attraction of organisms to seamounts

  14. A New Wave of Acoustics.

    ERIC Educational Resources Information Center

    Beyer, Robert

    1981-01-01

    Surveys 50 years of acoustical studies by discussing selected topics including the ear, nonlinear representations, underwater sound, acoustical diagnostics, absorption, electrolytes, phonons, magnetic interaction, and superfluidity and the five sounds. (JN)

  15. Structural Acoustics and Vibrations

    NASA Astrophysics Data System (ADS)

    Chaigne, Antoine

    This chapter is devoted to vibrations of structures and to their coupling with the acoustic field. Depending on the context, the radiated sound can be judged as desirable, as is mostly the case for musical instruments, or undesirable, like noise generated by machinery. In architectural acoustics, one main goal is to limit the transmission of sound through walls. In the automobile industry, the engineers have to control the noise generated inside and outside the passenger compartment. This can be achieved by means of passive or active damping. In general, there is a strong need for quieter products and better sound quality generated by the structures in our daily environment.

  16. Electromechanical acoustic liner

    NASA Technical Reports Server (NTRS)

    Sheplak, Mark (Inventor); Cattafesta, III, Louis N. (Inventor); Nishida, Toshikazu (Inventor); Horowitz, Stephen Brian (Inventor)

    2007-01-01

    A multi-resonator-based system responsive to acoustic waves includes at least two resonators, each including a bottom plate, side walls secured to the bottom plate, and a top plate disposed on top of the side walls. The top plate includes an orifice so that a portion of an incident acoustical wave compresses gas in the resonators. The bottom plate or the side walls include at least one compliant portion. A reciprocal electromechanical transducer coupled to the compliant portion of each of the resonators forms a first and second transducer/compliant composite. An electrical network is disposed between the reciprocal electromechanical transducer of the first and second resonator.

  17. Densitometry By Acoustic Levitation

    NASA Technical Reports Server (NTRS)

    Trinh, Eugene H.

    1989-01-01

    "Static" and "dynamic" methods developed for measuring mass density of acoustically levitated solid particle or liquid drop. "Static" method, unknown density of sample found by comparison with another sample of known density. "Dynamic" method practiced with or without gravitational field. Advantages over conventional density-measuring techniques: sample does not have to make contact with container or other solid surface, size and shape of samples do not affect measurement significantly, sound field does not have to be know in detail, and sample can be smaller than microliter. Detailed knowledge of acoustic field not necessary.

  18. Acoustic tooth cleaner

    NASA Technical Reports Server (NTRS)

    Heyman, J. S. (Inventor)

    1982-01-01

    An acoustic oral hygiene unit is described that uses acoustic energy to oscillate mild abrasive particles in a water suspension which is then directed in a low pressure stream onto the teeth. The oscillating abrasives scrub the teeth clean removing food particles, plaque, calculous, and other foreign material from tooth surfaces, interproximal areas, and tooth-gingiva interface more effectively than any previous technique. The relatively low power output and the basic design makes the invention safe and convenient for everyday use in the home without special training. This invention replaces all former means of home dental prophylaxis, and requires no augmentation to fulfill all requirements for daily oral hygienic care.

  19. Acoustic emission intrusion detector

    DOEpatents

    Carver, Donald W.; Whittaker, Jerry W.

    1980-01-01

    An intrusion detector is provided for detecting a forcible entry into a secured structure while minimizing false alarms. The detector uses a piezoelectric crystal transducer to sense acoustic emissions. The transducer output is amplified by a selectable gain amplifier to control the sensitivity. The rectified output of the amplifier is applied to a Schmitt trigger circuit having a preselected threshold level to provide amplitude discrimination. Timing circuitry is provided which is activated by successive pulses from the Schmitt trigger which lie within a selected time frame for frequency discrimination. Detected signals having proper amplitude and frequency trigger an alarm within the first complete cycle time of a detected acoustical disturbance signal.

  20. Strong acoustic wave action

    NASA Astrophysics Data System (ADS)

    Gokhberg, M. B.

    1983-07-01

    Experiments devoted to acoustic action on the atmosphere-magnetosphere-ionosphere system using ground based strong explosions are reviewed. The propagation of acoustic waves was observed by ground observations over 2000 km in horizontal direction and to an altitude of 200 km. Magnetic variations up to 100 nT were detected by ARIEL-3 satellite near the epicenter of the explosion connected with the formation of strong field aligned currents in the magnetosphere. The enhancement of VLF emission at 800 km altitude is observed.

  1. Acoustic bubble removal method

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Elleman, D. D.; Wang, T. G. (Inventor)

    1983-01-01

    A method is described for removing bubbles from a liquid bath such as a bath of molten glass to be used for optical elements. Larger bubbles are first removed by applying acoustic energy resonant to a bath dimension to drive the larger bubbles toward a pressure well where the bubbles can coalesce and then be more easily removed. Thereafter, submillimeter bubbles are removed by applying acoustic energy of frequencies resonant to the small bubbles to oscillate them and thereby stir liquid immediately about the bubbles to facilitate their breakup and absorption into the liquid.

  2. Acoustic and electromagnetic waves

    NASA Astrophysics Data System (ADS)

    Jones, Douglas Samuel

    Theoretical models of EM and acoustic wave propagation are presented in an introductory text intended for intermediate-level science and engineering students. Chapters are devoted to the mathematical representation of acoustic and EM fields, the special theory of relativity, radiation, resonators, waveguide theory, refraction, surface waves, scattering by smooth objects, diffraction by edges, and transient waves. The mathematical tools required for the analysis (Bessel, Legendre, Mathieu, parabolic-cylinder, and spheroidal functions; tensor calculus; and the asymptotic evaluation of integrals) are covered in appendices.

  3. Acoustic loading in straight pipes

    NASA Technical Reports Server (NTRS)

    El-Raheb, M.

    1980-01-01

    Based on linear one-dimensional acoustics, a geometrically perfect elastic waveguide would respond to an oscillatory internal pressure only in the presence of path deflectors (elbows and branches). In practice, a significant elasto-acoustic interaction results even in straight conduits as a result of manufacturing tolerances. A theoretical model of the linear acoustic loading in straight pipes is developed that considers the acoustic wave distortion due to perimeter, axial, and wall thickness nonuniformities.

  4. Spacecraft Internal Acoustic Environment Modeling

    NASA Technical Reports Server (NTRS)

    Allen, Christopher; Chu, S. Reynold

    2008-01-01

    The objective of the project is to develop an acoustic modeling capability, based on commercial off-the-shelf software, to be used as a tool for oversight of the future manned Constellation vehicles to ensure compliance with acoustic requirements and thus provide a safe and habitable acoustic environment for the crews, and to validate developed models via building physical mockups and conducting acoustic measurements.

  5. Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic Testing

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; O'Connell, Michael R.; Tsoi, Wan B.

    2009-01-01

    Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in

  6. Closing remarks on Faraday Discussion 107: Interactions of acoustic waves with thin films and interfaces

    SciTech Connect

    Martin, S.J.

    1997-11-01

    The papers in this Faraday Discussion represent the state-of-the-art in using acoustic devices to measure the properties of thin films and interfaces. Sauerbrey first showed that the mass sensitivity of a quartz crystal could be used to measure the thickness of vacuum-deposited metals. Since then, significant progress has been made in understanding other interaction mechanisms between acoustic devices and contacting media. Bruckenstein and Shay and Kanazawa and Gordon showed that quartz resonators could be operated in a fluid to measure surface mass accumulation and fluid properties. The increased understanding of interactions between acoustic devices and contacting media has allowed new information to be obtained about thin films and interfaces. These closing remarks will summarize the current state of using acoustic techniques to probe thin films and interfaces, describe the progress reported in this Faraday Discussion, and outline some remaining problems. Progress includes new measurement techniques, novel devices, new applications, and improved modeling and data analysis.

  7. Variable-Position Acoustic Levitation

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Stoneburner, J. D.; Jacobi, N.; Wang, T. G.

    1983-01-01

    Method of acoustic levitation supports objects at positions other than acoustic nodes. Acoustic force is varied so it balances gravitational (or other) force, thereby maintaining object at any position within equilibrium range. Levitation method applicable to containerless processing. Such objects as table-tennis balls, hollow plastic spheres, and balsa-wood spheres levitated in laboratory by new method.

  8. Post Treatment of Acoustic Neuroma

    MedlinePlus

    Home What is an AN What is an Acoustic Neuroma? Identifying an AN Symptoms Acoustic Neuroma Keywords Educational Video Pre-Treatment Treatment Options Summary Treatment Options Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions ...

  9. Acoustical Environment of School Buildings.

    ERIC Educational Resources Information Center

    Fitzroy, Dariel; Reid, John L.

    A field study was made of the acoustical environment of schools designed for increased flexibility to meet the spatial requirements of new teaching methods. The object of the study was to define all the criteria for the acoustical design of this type of classroom including the determination of--(1) minimum acoustical separation required for…

  10. ACOUSTICAL ENVIRONMENT OF SCHOOL BUILDINGS.

    ERIC Educational Resources Information Center

    FITZROY, DARIEL; REID, JOHN L.

    A FIELD STUDY WAS MADE OF THE ACOUSTICAL ENVIRONMENT OF SCHOOLS DESIGNED FOR INCREASED FLEXIBILITY TO MEET THE SPATIAL REQUIREMENTS OF NEW TEACHING METHODS. THE OBJECT OF THE STUDY WAS TO DEFINE ALL THE CRITERIA FOR THE ACOUSTICAL DESIGN OF THIS TYPE OF CLASSROOM INCLUDING THE DETERMINATION OF--(1) MINIMUM ACOUSTICAL SEPARATION REQUIRED FOR…

  11. Fundamentals of Acoustics. Psychoacoustics and Hearing. Acoustical Measurements

    NASA Technical Reports Server (NTRS)

    Begault, Durand R.; Ahumada, Al (Technical Monitor)

    1997-01-01

    These are 3 chapters that will appear in a book titled "Building Acoustical Design", edited by Charles Salter. They are designed to introduce the reader to fundamental concepts of acoustics, particularly as they relate to the built environment. "Fundamentals of Acoustics" reviews basic concepts of sound waveform frequency, pressure, and phase. "Psychoacoustics and Hearing" discusses the human interpretation sound pressure as loudness, particularly as a function of frequency. "Acoustic Measurements" gives a simple overview of the time and frequency weightings for sound pressure measurements that are used in acoustical work.

  12. Acoustic subwavelength imaging of subsurface objects with acoustic resonant metalens

    SciTech Connect

    Cheng, Ying; Liu, XiaoJun; Zhou, Chen; Wei, Qi; Wu, DaJian

    2013-11-25

    Early research into acoustic metamaterials has shown the possibility of achieving subwavelength near-field acoustic imaging. However, a major restriction of acoustic metamaterials is that the imaging objects must be placed in close vicinity of the devices. Here, we present an approach for acoustic imaging of subsurface objects far below the diffraction limit. An acoustic metalens made of holey-structured metamaterials is used to magnify evanescent waves, which can rebuild an image at the central plane. Without changing the physical structure of the metalens, our proposed approach can image objects located at certain distances from the input surface, which provides subsurface signatures of the objects with subwavelength spatial resolution.

  13. Otitis media with effusion

    MedlinePlus

    OME; Secretory otitis media; Serous otitis media; Silent otitis media; Silent ear infection; Glue ear ... drains from the tube and is swallowed. Otitis media with effusion (OME) and ear infections are connected ...

  14. On Media Education

    ERIC Educational Resources Information Center

    Fedorov, Alexander

    2008-01-01

    This monograph analyzes the theory and practice of media education and media literacy. The book also includes the list of Russian media education literature and addresses of websites of the associations for media education.

  15. Approaches to Media Management.

    ERIC Educational Resources Information Center

    Macciocca, Julie

    1996-01-01

    Describes how media/technology specialists organize and monitor instructional resources in schools. Topics include technology coordinators, decentralization of resources, media specialists in each school, and media retrieval systems to schedule the use of media and technology in classrooms. (LRW)

  16. ADSORPTIVE MEDIA TECHNOLOGIES: MEDIA SELECTION

    EPA Science Inventory

    The presentation provides information on six items to be considered when selecting an adsorptive media for removing arsenic from drinking water; performance, EBCT, pre-treatment, regeneration, residuals, and cost. Each item is discussed in general and data and photographs from th...

  17. Cloaking an acoustic sensor with single-negative materials

    SciTech Connect

    Cai, Chen; Zhu, Xue-Feng; Xu, Tao; Zou, Xin-Ye; Liang, Bin; Cheng, Jian-Chun

    2015-07-15

    In this review, a brief introduction is given to the development of acoustic superlens cloaks that allow the cloaked object to receive signals while its presence is not sensed by the surrounding, which can be regarded as “cloaking an acoustic sensor”. Remarkably, the designed cloak consists of single-negative materials with parameters independent of the background medium or the sensor system, which is proven to be a magnifying superlens. This has facilitated significantly the design and fabrication of acoustic cloaks that generally require double-negative materials with customized parameters. Such innovative design has then been simplified further as a multi-layered structure comprising of two alternately arranged complementary media with homogeneous isotropic single-negative materials. Based on this, a scattering analyses method is developed for the numerical simulation of such multi-layered cloak structures, which may serve as an efficient approach for the investigation on such devices.

  18. Propagation characteristics of acoustic waves in snow

    NASA Astrophysics Data System (ADS)

    Capelli, Achille; Kapil, Jagdish Chandra; Reiweger, Ingrid; Schweizer, Jürg; Or, Dani

    2015-04-01

    Acoustic emission analysis is a promising technique for monitoring snow slope stability with potential for application in early warning systems for avalanches. Current research efforts focus on identification and localization of acoustic emission features preceding snow failure and avalanches. However, our knowledge of sound propagation characteristics in snow is still limited. A review of previous studies showed that significant gaps exist and that the results of the various studies are partly contradictory. Furthermore, sound velocity and attenuation have been determined for the frequency range below 10 kHz, while recent snow failure experiments suggest that the peak frequency is in the ultrasound range between 30 kHz to 500 kHz. We therefore studied the propagation of pencil lead fracture (PLF) signals through snow in the ultrasound frequency range. This was achieved by performing laboratory experiments with columns of artificially produced snow of varying density and temperature. The attenuation constant was obtained by varying the size of the columns to eliminate possible influences of the snow-sensor coupling. The attenuation constant was measured for the entire PLF burst signal and for single frequency components. The propagation velocity was calculated from the arrival time of the acoustic signal. We then modelled the sound propagation for our experimental setup using Biot's model for wave propagation in porous media. The Model results were in good agreement with our experimental results. For the studied samples, the acoustic signals propagated as fast and slow longitudinal waves, but the main part of the energy was carried by the slow waves. The Young's modulus of our snow samples was determined from the sound velocity. This is highly relevant, as the elastic properties of snow are not well known.

  19. COMBUSTION ACOUSTICS DIAGNOSTICS

    EPA Science Inventory

    This is an Exploratory Research Project that was awarded by APPCD for research on developing an acoustic flame condition monitor. It will involve a bench scale experiment of 4-6 weeks duration to record adjacent audible energy of a Bunsen burner. The experiment will require a d...

  20. Acoustics in Schools.

    ERIC Educational Resources Information Center

    Singer, Miriam J.

    This paper explores the issues associated with poor acoustics within schools. Additionally, it suggests remedies for existing buildings and those under renovation, as well as concerns for new construction. The paper discusses the effects of unwanted noise on students in terms of physiological, motivational, and cognitive influences. Issues are…

  1. Microfiber interferometric acoustic transducers.

    PubMed

    Wang, Xiuxin; Jin, Long; Li, Jie; Ran, Yang; Guan, Bai-Ou

    2014-04-01

    Acoustic and ultrasonic transducers are key components in biomedical information technology, which has been applied in medical diagnosis, photoacoustic endoscopy and photoacoustic imaging. In this paper, an acoustic transducer based on Fabry-Perot interferometer (FPI) fabricated in a microscaled optical fiber is demonstrated. The transducer is fabricated by forming two wavelength-matched Bragg gratings into the microfiber by means of side illumination with a 193nm excimer laser. When placing the transducer in water, the applied acoustic signal periodically changes the refractive index (RI) of the surrounding liquid and modulates the transmission of the FPI based on the evanescent-field interaction between the liquid and the transmitting light. As a result, the acoustic signal can be constructed with a tunable laser whose output wavelength is located at the slope of the inteferometric fringes. The transducer presents a sensitivity of 10 times higher than the counterparts fabricated in conventional singlemode fibers and has great potential to achieve higher resolution for photoacoustic imaging due to its reduced diameter. PMID:24718189

  2. Intelligent Engine Systems: Acoustics

    NASA Technical Reports Server (NTRS)

    Wojno, John; Martens, Steve; Simpson, Benjamin

    2008-01-01

    An extensive study of new fan exhaust nozzle technologies was performed. Three new uniform chevron nozzles were designed, based on extensive CFD analysis. Two new azimuthally varying variants were defined. All five were tested, along with two existing nozzles, on a representative model-scale, medium BPR exhaust nozzle. Substantial acoustic benefits were obtained from the uniform chevron nozzle designs, the best benefit being provided by an existing design. However, one of the azimuthally varying nozzle designs exhibited even better performance than any of the uniform chevron nozzles. In addition to the fan chevron nozzles, a new technology was demonstrated, using devices that enhance mixing when applied to an exhaust nozzle. The acoustic benefits from these devices applied to medium BPR nozzles were similar, and in some cases superior to, those obtained from conventional uniform chevron nozzles. However, none of the low noise technologies provided equivalent acoustic benefits on a model-scale high BPR exhaust nozzle, similar to current large commercial applications. New technologies must be identified to improve the acoustics of state-of-the-art high BPR jet engines.

  3. Teaching acoustics online

    NASA Astrophysics Data System (ADS)

    Morrison, Andrew; Rossing, Thomas D.

    2003-10-01

    We teach an introductory course in musical acoustics using a Blackboard. Students in this course can access audio and video materials as well as printed materials on our course website. All homework is submitted online, as are tests and examinations. The students also have the opportunity to use synchronous and asynchronous chat rooms to discuss the course with each other or with the instructors.

  4. Micro acoustic spectrum analyzer

    DOEpatents

    Schubert, W. Kent; Butler, Michael A.; Adkins, Douglas R.; Anderson, Larry F.

    2004-11-23

    A micro acoustic spectrum analyzer for determining the frequency components of a fluctuating sound signal comprises a microphone to pick up the fluctuating sound signal and produce an alternating current electrical signal; at least one microfabricated resonator, each resonator having a different resonant frequency, that vibrate in response to the alternating current electrical signal; and at least one detector to detect the vibration of the microfabricated resonators. The micro acoustic spectrum analyzer can further comprise a mixer to mix a reference signal with the alternating current electrical signal from the microphone to shift the frequency spectrum to a frequency range that is a better matched to the resonant frequencies of the microfabricated resonators. The micro acoustic spectrum analyzer can be designed specifically for portability, size, cost, accuracy, speed, power requirements, and use in a harsh environment. The micro acoustic spectrum analyzer is particularly suited for applications where size, accessibility, and power requirements are limited, such as the monitoring of industrial equipment and processes, detection of security intrusions, or evaluation of military threats.

  5. Angular spectrum approach for the computation of group and phase velocity surfaces of acoustic waves in anisotropic materials

    PubMed

    Pluta; Schubert; Jahny; Grill

    2000-03-01

    The decomposition of an acoustic wave into its angular spectrum representation creates an effective base for the calculation of wave propagation effects in anisotropic media. In this method, the distribution of acoustic fields is calculated in arbitrary planes from the superposition of the planar components with proper phase shifts. These phase shifts depend on the ratio of the distance between the planes to the normal component of the phase slowness vector. In anisotropic media, the phase shifts depend additionally on the changes of the slowness with respect to the direction of the propagation vector and the polarization. Those relations are obtained from the Christoffel equation. The method employing the fast Fourier transformation algorithm is especially suited for volume imaging in anisotropic media, based on holographic detection in transmission of acoustic waves generated by a point source. This technique is compared with measurements on crystals performed by phase-sensitive scanning acoustic microscopy. PMID:10829665

  6. Otitis Media

    PubMed Central

    Bain, John

    1992-01-01

    Otitis media remains one of the least understood conditions seen by a family physician. More attention to follow up instead of widespread use of antibiotics and decongestant mixtures could improve family practice care of children with middle ear disorders. Greater selection in resorting to surgical management would be helpful. Unnecessary interference is unlikely to be of long-term benefit to either children or their families. ImagesFigures 1-3Figures 4-5 PMID:21221314

  7. Otitis media.

    PubMed

    Schilder, Anne G M; Chonmaitree, Tasnee; Cripps, Allan W; Rosenfeld, Richard M; Casselbrant, Margaretha L; Haggard, Mark P; Venekamp, Roderick P

    2016-01-01

    Otitis media (OM) or middle ear inflammation is a spectrum of diseases, including acute otitis media (AOM), otitis media with effusion (OME; 'glue ear') and chronic suppurative otitis media (CSOM). OM is among the most common diseases in young children worldwide. Although OM may resolve spontaneously without complications, it can be associated with hearing loss and life-long sequelae. In developing countries, CSOM is a leading cause of hearing loss. OM can be of bacterial or viral origin; during 'colds', viruses can ascend through the Eustachian tube to the middle ear and pave the way for bacterial otopathogens that reside in the nasopharynx. Diagnosis depends on typical signs and symptoms, such as acute ear pain and bulging of the tympanic membrane (eardrum) for AOM and hearing loss for OME; diagnostic modalities include (pneumatic) otoscopy, tympanometry and audiometry. Symptomatic management of ear pain and fever is the mainstay of AOM treatment, reserving antibiotics for children with severe, persistent or recurrent infections. Management of OME largely consists of watchful waiting, with ventilation (tympanostomy) tubes primarily for children with chronic effusions and hearing loss, developmental delays or learning difficulties. The role of hearing aids to alleviate symptoms of hearing loss in the management of OME needs further study. Insertion of ventilation tubes and adenoidectomy are common operations for recurrent AOM to prevent recurrences, but their effectiveness is still debated. Despite reports of a decline in the incidence of OM over the past decade, attributed to the implementation of clinical guidelines that promote accurate diagnosis and judicious use of antibiotics and to pneumococcal conjugate vaccination, OM continues to be a leading cause for medical consultation, antibiotic prescription and surgery in high-income countries. PMID:27604644

  8. Media Education Initiatives by Media Organizations: The Uses of Media Literacy in Hong Kong Media

    ERIC Educational Resources Information Center

    Chu, Donna; Lee, Alice Y. L.

    2014-01-01

    As more media organizations have engaged in media education, this paper investigates the goals and practices of these activities. This article coins media education initiatives by media organizations with the term "media-organization media literac"y (MOML). Four MOML projects in Hong Kong were selected for examination. Built on critical…

  9. Acoustics- Version 1.0

    SciTech Connect

    2012-09-13

    This package contains modules that model acoustic sensors and acoustic sources (hearable) in Umbra. It is typically used to represent hearing in characters within Umbra. Typically, the acoustic sensors detect acoustic sources at a given point; however, it also contains the capability to detect bullet cracks by detecting the sound along the bullet path that is closest to the sensor. A memory module, acoustic memory, represents remembered sounds within a given character. Over time, the sounds are removed, as a character forgets what it has heard.

  10. Acoustics- Version 1.0

    Energy Science and Technology Software Center (ESTSC)

    2012-09-13

    This package contains modules that model acoustic sensors and acoustic sources (hearable) in Umbra. It is typically used to represent hearing in characters within Umbra. Typically, the acoustic sensors detect acoustic sources at a given point; however, it also contains the capability to detect bullet cracks by detecting the sound along the bullet path that is closest to the sensor. A memory module, acoustic memory, represents remembered sounds within a given character. Over time, themore » sounds are removed, as a character forgets what it has heard.« less

  11. Measurement of Bubble Size Distribution Based on Acoustic Propagation in Bubbly Medium

    NASA Astrophysics Data System (ADS)

    Wu, Xiongjun; Hsiao, Chao-Tsung; Choi, Jin-Keun; Chahine, Georges

    2013-03-01

    Acoustic properties are strongly affected by bubble size distribution in a bubbly medium. Measurement of the acoustic transmission becomes increasingly difficulty as the void fraction of the bubbly medium increases due to strong attenuation, while acoustic reflection can be measured more easily with increasing void fraction. The ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright, an instrument for bubble size measurement that is under development tries to take full advantage of the properties of acoustic propagation in bubbly media to extract bubble size distribution. Properties of both acoustic transmission and reflection in the bubbly medium from a range of short single-frequency bursts of acoustic waves at different frequencies are measured in an effort to deduce the bubble size distribution. With the combination of both acoustic transmission and reflection, assisted with validations from photography, the ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright has the potential to measure bubble size distributions in a wider void fraction range. This work was sponsored by Department of Energy SBIR program

  12. A Bayesian approach to modal decomposition in ocean acoustics.

    PubMed

    Michalopoulou, Zoi-Heleni

    2009-11-01

    A Bayesian approach is developed for modal decomposition from time-frequency representations of broadband acoustic signals propagating in underwater media. The goal is to obtain accurate estimates and posterior probability distributions of modal frequencies arriving at a specific time and their corresponding amplitudes, which can be employed for geoacoustic inversion. The proposed approach, optimized via Gibbs sampling, provides uncertainty information on modal characteristics via the posterior distributions, typically unavailable from traditional methods. PMID:19894790

  13. Acoustic Suppression Systems and Related Methods

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R. (Inventor); Kern, Dennis L. (Inventor)

    2013-01-01

    An acoustic suppression system for absorbing and/or scattering acoustic energy comprising a plurality of acoustic targets in a containment is described, the acoustic targets configured to have resonance frequencies allowing the targets to be excited by incoming acoustic waves, the resonance frequencies being adjustable to suppress acoustic energy in a set frequency range. Methods for fabricating and implementing the acoustic suppression system are also provided.

  14. Underwater asymmetric acoustic transmission structure using the medium with gradient change of impedance

    NASA Astrophysics Data System (ADS)

    Bo, Hu; Jie, Shi; Sheng-Guo, Shi; Yu, Sun; Zhong-Rui, Zhu

    2016-02-01

    We propose an underwater asymmetric acoustic transmission structure comprised of two media each with a gradient change of acoustic impedance. By gradually increasing the acoustic impedances of the media, the propagating direction of the acoustic wave can be continuously bent, resulting in allowing the acoustic wave to pass through along the positive direction and blocking acoustic waves from the negative one. The main advantages of this structure are that the asymmetric transmission effect of this structure can be realized and enhanced more easily in water. We investigate both numerically and experimentally the asymmetric transmission effect. The experimental results show that a highly efficient asymmetric acoustic transmission can be yielded within a remarkable broadband frequency range, which agrees well with the numerical prediction. It is of potential practical significance for various underwater applications such as reducing vibration and noise. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204049 and 11204050), the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (Grant No. IRT1228), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant Nos. 20122304120023 and 20122304120011).

  15. Recent Developments and the Impact of the Newer Media.

    ERIC Educational Resources Information Center

    Dwyer, Francis M.

    Technical features of Penn State's Instructional Media Center are described. Unlike many other instructional units, special attention has been paid to the physiological requirements for learning in its design and construction, i.e., acoustics, lighting, visibility, and air conditioning. The building contains many unique features which may be…

  16. Education in acoustics in Argentina

    NASA Astrophysics Data System (ADS)

    Miyara, Federico

    2002-11-01

    Over the last decades, education in acoustics (EA) in Argentina has experienced ups and downs due to economic and political issues interfering with long term projects. Unlike other countries, like Chile, where EA has reached maturity in spite of the acoustical industry having shown little development, Argentina has several well-established manufacturers of acoustic materials and equipment but no specific career with a major in acoustics. At the university level, acoustics is taught as a complementary--often elective--course for careers such as architecture, communication engineering, or music. In spite of this there are several research centers with programs covering environmental and community noise, effects of noise on man, acoustic signal processing, musical acoustics and acoustic emission, and several national and international meetings are held each year in which results are communicated and discussed. Several books on a variety of topics such as sound system, architectural acoustics, and noise control have been published as well. Another chapter in EA is technical and vocational education, ranging between secondary and postsecondary levels, with technical training on sound system operation or design. Over the last years there have been several attempts to implement master degrees in acoustics or audio engineering, with little or no success.

  17. Acoustic energy harvesting based on a planar acoustic metamaterial

    NASA Astrophysics Data System (ADS)

    Qi, Shuibao; Oudich, Mourad; Li, Yong; Assouar, Badreddine

    2016-06-01

    We theoretically report on an innovative and practical acoustic energy harvester based on a defected acoustic metamaterial (AMM) with piezoelectric material. The idea is to create suitable resonant defects in an AMM to confine the strain energy originating from an acoustic incidence. This scavenged energy is converted into electrical energy by attaching a structured piezoelectric material into the defect area of the AMM. We show an acoustic energy harvester based on a meta-structure capable of producing electrical power from an acoustic pressure. Numerical simulations are provided to analyze and elucidate the principles and the performances of the proposed system. A maximum output voltage of 1.3 V and a power density of 0.54 μW/cm3 are obtained at a frequency of 2257.5 Hz. The proposed concept should have broad applications on energy harvesting as well as on low-frequency sound isolation, since this system acts as both acoustic insulator and energy harvester.

  18. Books on acoustics

    NASA Astrophysics Data System (ADS)

    Shaw, Neil A.

    2001-05-01

    The legacy of a man is not limited to just his projects. His writings in many cases are a more lasting, and a definitely more accessible, monument. For 60 years, Leo L. Beranek has produced books on acoustics, acoustic measurements, sound control, music and architecture, noise and vibration control, concert halls, and opera houses in addition to teaching and consulting. His books are standard references and still cited in other books and in technical and professional articles. Many of his books were among, if not, the first comprehensive modern treatment of the subject and many are still foremost. A review of Dr. Beranek's many books as well as some anecdotes about the circumstances and consequences of same will be presented.

  19. Alaskan river environmental acoustics

    NASA Astrophysics Data System (ADS)

    Dahl, Peter H.; Pfisterer, Carl; Geiger, Harold J.

    2005-04-01

    Sonars are used by the Alaska Department of Fish and Game (ADF&G) to obtain daily and hourly estimates of at least four species of migratory salmon during their seasonal migration which lasts from June to beginning of September. Suspended sediments associated with a river's sediment load is an important issue for ADF&G's sonar operations. Acoustically, the suspended sediments are a source of both volume reverberation and excess attenuation beyond that expected in fresh water. Each can impact daily protocols for fish enumeration via sonar. In this talk, results from an environmental acoustic study conducted in the Kenai River (June 1999) using 420 kHz and 200 kHz side looking sonars, and in the Yukon River (July 2001) using a 120 kHz side looking sonar, are discussed. Estimates of the volume scattering coefficient and attenuation are related to total suspended sediments. The relative impact of bubble scattering and sediment scattering is also discussed.

  20. Acoustics Discipline Overview

    NASA Technical Reports Server (NTRS)

    Envia, Edmane; Thomas, Russell

    2007-01-01

    As part of the Fundamental Aeronautics Program Annual Review, a summary of the progress made in 2007 in acoustics research under the Subsonic Fixed Wing project is given. The presentation describes highlights from in-house and external activities including partnerships and NRA-funded research with industry and academia. Brief progress reports from all acoustics Phase 1 NRAs are also included as are outlines of the planned activities for 2008 and all Phase 2 NRAs. N+1 and N+2 technology paths outlined for Subsonic Fixed Wing noise targets. NRA Round 1 progressing with focus on prediction method advancement. NRA Round 2 initiating work focused on N+2 technology, prediction methods, and validation. Excellent partnerships in progress supporting N+1 technology targets and providing key data sets.

  1. Radiosurgery of acoustic neurinomas

    SciTech Connect

    Flickinger, J.C.; Lunsford, L.D.; Coffey, R.J.; Linskey, M.E.; Bissonette, D.J.; Maitz, A.H.; Kondziolka, D. )

    1991-01-15

    Eighty-five patients with acoustic neurinomas underwent stereotactic radiosurgery with the gamma unit at the University of Pittsburgh (Pittsburgh, PA) during its first 30 months of operation. Neuroimaging studies performed in 40 patients with more than 1 year follow-up showed that tumors were smaller in 22 (55%), unchanged in 17 (43%), and larger in one (2%). The 2-year actuarial rates for preservation of useful hearing and any hearing were 46% and 62%, respectively. Previously undetected neuropathies of the trigeminal (n = 12) and facial nerves (n = 14) occurred 1 week to 1 year after radiosurgery (median, 7 and 6 months, respectively), and improved at median intervals of 13 and 8 months, respectively, after onset. Hearing loss was significantly associated with increasing average tumor diameter (P = 0.04). No deterioration of any cranial nerve function has yet developed in seven patients with average tumor diameters less than 10 mm. Radiosurgery is an important treatment alternative for selected acoustic neurinoma patients.

  2. Acoustic methodology review

    NASA Technical Reports Server (NTRS)

    Schlegel, R. G.

    1982-01-01

    It is important for industry and NASA to assess the status of acoustic design technology for predicting and controlling helicopter external noise in order for a meaningful research program to be formulated which will address this problem. The prediction methodologies available to the designer and the acoustic engineer are three-fold. First is what has been described as a first principle analysis. This analysis approach attempts to remove any empiricism from the analysis process and deals with a theoretical mechanism approach to predicting the noise. The second approach attempts to combine first principle methodology (when available) with empirical data to formulate source predictors which can be combined to predict vehicle levels. The third is an empirical analysis, which attempts to generalize measured trends into a vehicle noise prediction method. This paper will briefly address each.

  3. Acoustic tractor beam.

    PubMed

    Démoré, Christine E M; Dahl, Patrick M; Yang, Zhengyi; Glynne-Jones, Peter; Melzer, Andreas; Cochran, Sandy; MacDonald, Michael P; Spalding, Gabriel C

    2014-05-01

    Negative radiation forces act opposite to the direction of propagation, or net momentum, of a beam but have previously been challenging to definitively demonstrate. We report an experimental acoustic tractor beam generated by an ultrasonic array operating on macroscopic targets (>1 cm) to demonstrate the negative radiation forces and to map out regimes over which they dominate, which we compare to simulations. The result and the geometrically simple configuration show that the effect is due to nonconservative forces, produced by redirection of a momentum flux from the angled sides of a target and not by conservative forces from a potential energy gradient. Use of a simple acoustic setup provides an easily understood illustration of the negative radiation pressure concept for tractor beams and demonstrates continuous attraction towards the source, against a net momentum flux in the system. PMID:24836252

  4. Acoustic Tractor Beam

    NASA Astrophysics Data System (ADS)

    Démoré, Christine E. M.; Dahl, Patrick M.; Yang, Zhengyi; Glynne-Jones, Peter; Melzer, Andreas; Cochran, Sandy; MacDonald, Michael P.; Spalding, Gabriel C.

    2014-05-01

    Negative radiation forces act opposite to the direction of propagation, or net momentum, of a beam but have previously been challenging to definitively demonstrate. We report an experimental acoustic tractor beam generated by an ultrasonic array operating on macroscopic targets (>1 cm) to demonstrate the negative radiation forces and to map out regimes over which they dominate, which we compare to simulations. The result and the geometrically simple configuration show that the effect is due to nonconservative forces, produced by redirection of a momentum flux from the angled sides of a target and not by conservative forces from a potential energy gradient. Use of a simple acoustic setup provides an easily understood illustration of the negative radiation pressure concept for tractor beams and demonstrates continuous attraction towards the source, against a net momentum flux in the system.

  5. A Martian acoustic anemometer.

    PubMed

    Banfield, Don; Schindel, David W; Tarr, Steve; Dissly, Richard W

    2016-08-01

    An acoustic anemometer for use on Mars has been developed. To understand the processes that control the interaction between surface and atmosphere on Mars, not only the mean winds, but also the turbulent boundary layer, the fluxes of momentum, heat and molecular constituents between surface and atmosphere must be measured. Terrestrially this is done with acoustic anemometers, but the low density atmosphere on Mars makes it challenging to adapt such an instrument for use on Mars. This has been achieved using capacitive transducers and pulse compression, and was successfully demonstrated on a stratospheric balloon (simulating the Martian environment) and in a dedicated Mars Wind Tunnel facility. This instrument achieves a measurement accuracy of ∼5 cm/s with an update rate of >20 Hz under Martian conditions. PMID:27586767

  6. Structural Acoustics and Vibrations

    NASA Astrophysics Data System (ADS)

    Chaigne, Antoine

    This structural chapter is devoted to vibrations of structures and to their coupling with the acoustic field. Depending on the context, the radiated sound can be judged as desirable, as is mostly the case for musical instruments, or undesirable, like noise generated by machinery. In architectural acoustics, one main goal is to limit the transmission of sound through walls. In the automobile industry, the engineers have to control the noise generated inside and outside the passenger compartment. This can be achieved by means of passive or active damping. In general, there is a strong need for quieter products and better sound quality generated by the structures in our daily environment.

  7. Analogy between the one-dimensional acoustic waveguide and the electrical transmission line in the cases of nonlinearity and relaxation

    NASA Astrophysics Data System (ADS)

    Yang, Desen; Zhang, Haoyang; Shi, Shengguo; Li, Di; Shi, Jie; Hu, Bo

    2015-10-01

    The propagation of plane acoustic waves can be investigated by taking advantage of the electro-acoustical analogy between the one-dimensional acoustic waveguide and the electrical transmission line, because they share the same type of equation. This paper follow the previous studies and expand the analogy into the cases of quadratic nonlinearity and dispersion produced by relaxation process. From the basic equations relating acoustic pressure, density fluctuation and velocity, which are valid for the nonlinear and relaxing media, the equivalent travelling-wave circuits of one-dimensional acoustic waveguide with the consideration of nonlinearity and relaxation processes are obtained. Furthermore, we also discuss the analogy relationship of parameters which exist in the acoustical and electrical systems.

  8. Theory on acoustic sources

    NASA Technical Reports Server (NTRS)

    Wright, S. E.

    1978-01-01

    A theory is described for the radiation emission emission from acoustic multipole sources. The sources can be stationary or moving at speeds including supersonic and experience stationary or moving disturbances. The effect of finite source distributions and disturbances is investigated as well as the manner in which they interact. Distinction is made between source distributions that responsed as a function of time and those that respond as a function of space.

  9. Acoustic velocity meter systems

    USGS Publications Warehouse

    Laenen, Antonius

    1985-01-01

    Acoustic velocity meter (AVM) systems operate on the principles that the point-to-point upstream traveltime of an acoustic pulse is longer than the downstream traveltime and that this difference in traveltime can be accurately measured by electronic devices. An AVM system is capable of recording water velocity (and discharge) under a wide range of conditions, but some constraints apply: 1. Accuracy is reduced and performance is degraded if the acoustic path is not a continuous straight line. The path can be bent by reflection if it is too close to a stream boundary or by refraction if it passes through density gradients resulting from variations in either water temperature or salinity. For paths of less than 100 m, a temperature gradient of 0.1' per meter causes signal bending less than 0.6 meter at midchannel, and satisfactory velocity results can be obtained. Reflection from stream boundaries can cause signal cancellation if boundaries are too close to signal path. 2. Signal strength is attenuated by particles or bubbles that absorb, spread, or scatter sound. The concentration of particles or bubbles that can be tolerated is a function of the path length and frequency of the acoustic signal. 3. Changes in streamline orientation can affect system accuracy if the variability is random. 4. Errors relating to signal resolution are much larger for a single threshold detection scheme than for multiple threshold schemes. This report provides methods for computing the effect of various conditions on the accuracy of a record obtained from an AVM. The equipment must be adapted to the site. Field reconnaissance and preinstallation analysis to detect possible problems are critical for proper installation and operation of an AVM system.

  10. Structures and Acoustics Division

    NASA Technical Reports Server (NTRS)

    Acquaviva, Cynthia S.

    1999-01-01

    The Structures and Acoustics Division of NASA Glenn Research Center is an international leader in rotating structures, mechanical components, fatigue and fracture, and structural aeroacoustics. Included are disciplines related to life prediction and reliability, nondestructive evaluation, and mechanical drive systems. Reported are a synopsis of the work and accomplishments reported by the Division during the 1996 calendar year. A bibliography containing 42 citations is provided.