Showing papers on "Acoustic interferometer published in 2010"

Basics of Biomedical Ultrasound for Engineers

Abstract: Preface. Acknowledgments. Introduction. Prelude and Basic Definitions. The Advantages of Using Ultrasound in Medicine. A General Statement on Safety. Some Common Applications of Ultrasound. What Is It that We Need to Know? References. 1 Waves A General Description. 1.1 General Definitions of Waves A QualitativeDescription. 1.2 General Properties of Waves A QualitativeDescription. 1.3 Mechanical One-Dimensional Waves. 1.4 The Wave Function. 1.5 The Wave Equation. 1.6 Harmonic Waves. 1.7 Group Waves. 1.8 Wave Velocity. 1.9 Standing Waves (a Mathematical Description). 1.10 Spherical Waves. 1.11 Cylindrical Waves. 1.12 The Wave Equation in a Nonhomogeneous Medium. References. 2 Waves In A One-Dimensional Medium. 2.1 The Propagation Speed of Transverse Waves in a String. 2.2 Vibration Frequencies for a Bounded String. 2.3 Wave Reflection (Echo) in a One-Dimensional Medium. 2.4 Special Cases. 2.5 Wave Energy in Strings. 2.6 Propagation of Longitudinal Waves in an Isotropic Rod orString. 2.7 A Clinical Application of Longitudinal Waves in aString. References. 3 Ultraspmoc Waves in Fluids. 3.1 Waves in Fluids. 3.2 Compressibility. 3.3. Longitudinal Waves in Fluids. 3.4 The Wave Energy. 3.5 Intensity. 3.6 Radiation Pressure. 3.7 A Perfect Reflector. References. 4 Propogation of Acoustic Waves in Solid Materials. 4.1 Introduction to the Mechanics of Solids. 4.2 The Elastic Strain. 4.3 Stress. 4.4 Hooke s Law and Elastic Coefficients. 4.5 The Wave Equation for an Elastic Solid Material. 4.6 Propagation of a Harmonic Planar Wave in a SolidMaterial. References. 5 Attenuation and Dispersion. 5.1 The Attenuation Phenomenon. 5.2 Explaining Attenuation with a Simple Model. 5.3 Attenuation Dependency on Frequency. 5.4 The Complex Wave Number. 5.5 Speed of Sound Dispersion. 5.6 The Nonlinear Parameter B/A. References. 6 Reflection and Transmission. 6.1 The Acoustic Impedance. 6.2 Snell s Law. 6.3 Reflection and Transmission from Boundaries Separating TwoFluids (or Solids with No Shear Waves). 6.4 Reflection from a Free Surface in Solids (ModeConversion). 6.5 Reflection and Transmission from a Liquid SolidBoundary. References. 7 ACOUSTIC LENSES AND MIRRORS. 7.1 Optics. 7.2 Optics and Acoustics. 7.3 An Ellipsoidal Lens. 7.4 Spherical Lenses. 7.5 Zone Lenses. 7.6 Acoustic Mirrors (Focusing Reflectors). References. 8 Transducers and Acoustic Fields. 8.1 Piezoelectric Transducers. 8.2 The Acoustic Field. 8.3 The Field of a Point Source. 8.4 The Field of a Disc Source. 8.5 The Field of Various Transducers. 8.6 Phased-Array Transducers. 8.7 Annular Phased Arrays. References. 9 Ultrasonic Imaging Using the Pulse-Echo Technique. 9.1 Basic Definitions in Imaging. 9.2 The A-Line . 9.3 Scatter Model for Soft Tissues. 9.4 Time Gain Compensation. 9.5 Basic Pulse-Echo Imaging (B-Scan). 9.6 Advanced Methods for Pulse-Echo Imaging. References. 10 Special Imaging Techniques. 10.1 Acoustic Impedance Imaging Impediography. 10.2 Elastography. 10.3 Tissue Speckle Tracking. 10.4 Through-Transmission Imaging. 10.5 Vibro-acoustic Imaging. 10.6 Time Reversal. 10.7 Ultrasonic Computed Tomography. 10.8 Contrast Materials. 10.9 Coded Excitations. References. 11 Doppler Imaging Techniques. 11.1 The Doppler Effect. 11.2 Velocity Estimation. 11.3 Frequency Shift Estimation. 11.4 Duplex Imaging (Combined B-Scan and Color FlowMapping). References. 12 Safety and Therapuetic Applications. 12.1 Effects Induced by Ultrasound and Safety. 12.2 Ultrasonic Physiotherapy. 12.3 Lithotripsy. 12.4 Hyperthermia HIFU and Ablation. 12.5 Drug Delivery. 12.6 Gene Therapy. 12.7 Cosmetic Applications. References. Appenidx A: Typical Acoustic Properties of Tissues. Appendix B: Exemplary Problems. Appendix C: Answers to Exemplary Problems. Index.

Acoustic surface evanescent wave and its dominant contribution to extraordinary acoustic transmission and collimation of sound.

Abstract: We demonstrate both theoretically and experimentally the physical mechanism that underlies extraordinary acoustic transmission and collimation of sound through a one-dimensional decorated plate. A microscopic theory considers the total field as the sum of the scattered waves by every periodically aligned groove on the plate, which divides the total field into far-field radiative cylindrical waves and acoustic surface evanescent waves (ASEWs). Different from the well-known acoustic surface waves like Rayleigh waves and Lamb waves, ASEW is closely analogous to a surface plasmon polariton in the optical case. By mapping the total field, the experiments well confirm the theoretical calculations with ASEWs excited. The establishment of the concept of ASEW provides a new route for the integration of subwavelength acoustic devices with a structured solid surface.

Sputtered SiO 2 as low acoustic impedance material for Bragg mirror fabrication in BAW resonators

Abstract: In this paper we describe the procedure to sputter low acoustic impedance SiO2 films to be used as a low acoustic impedance layer in Bragg mirrors for BAW resonators. The composition and structure of the material are assessed through infrared absorption spectroscopy. The acoustic properties of the films (mass density and sound velocity) are assessed through X-ray reflectometry and picosecond acoustic spectroscopy. A second measurement of the sound velocity is achieved through the analysis of the longitudinal ?/2 resonance that appears in these silicon oxide films when used as uppermost layer of an acoustic reflector placed under an AlN-based resonator.

Acoustic absorber, acoustic transducer, and method for producing an acoustic absorber or an acoustic transducer

Abstract: The invention relates to an acoustic absorber comprising an absorption layer ( 1 a, 1 b ) composed of an open-pored porous material According to the invention, the open-pored porous material is flexurally stiff in such a way that the absorption layer ( 1 a, 1 b ) is stimulated to flexurally oscillate when sound waves impinge on the absorption layer and the absorber can absorb sound waves of a first frequency range because of the inflow of air into the open-pored porous material of the absorption layer and can absorb sound waves of a second frequency range that comprises lower frequencies than the first frequency range because of the stimulation of flexural oscillations of the absorption layer The invention further relates to an acoustic transducer and to a method for producing an acoustic absorber or an acoustic transducer

Piezoelectric resonator including an acoustic reflector portion

Abstract: A piezoelectric resonator that achieves stable quality and improved resonance characteristics includes an acoustic reflector portion disposed between a substrate and a vibration portion, which includes a piezoelectric thin film sandwiched between a pair of electrodes, and a plurality of low acoustic impedance layers made of a material having relatively low acoustic impedance and a plurality of high acoustic impedance layers formed made of a material having relatively high acoustic impedance, the acoustic impedance layers being disposed alternately, and adjustment layers, which are disposed between the high acoustic impedance layers and the low acoustic impedance layers on the substrate sides of the high acoustic impedance layers and which have an acoustic impedance value intermediate between that of the high acoustic impedance layers and that of the low acoustic impedance layers. The low acoustic impedance layers and the high acoustic impedance layers have compressive stresses and the adjustment layers have a tensile stress.

Solid-state acoustic metamaterial and method of using same to focus sound

Abstract: A phonemic crystal is made of a first solid medium having a first density and a substantially periodic array of structures disposed in the first medium, the structures being made of a second solid medium having a second density different from the first density. The first medium has a speed of propagation of longitudinal sound waves and a speed of propagation of transverse sound waves, the speed of propagation of longitudinal sound waves being approximately that of a fluid, and the speed of the propagation of transverse sound waves being smaller than the speed of propagation of longitudinal sound waves.

Acoustic waves from a supersonic jet impinging on an inclined flat plate

Abstract: Flow and flow-induced acoustic fields of a supersonic jet impinging on an inclined flat plate is computationally studied. Effects of nozzle-plate distance and jet temperature are discussed as these are important parameters for the estimation of the acoustic wave strength from the engineering viewpoint such as a rocket plume. Three-dimensional compressible Navier-Stokes equations are solved with the modified weighted compact nonlinear scheme for the numerical simulations. Simulation results are analyzed from the viewpoints of acoustic emission and propagation mechanism, and acoustic field characteristics such as directivity, their spectra, and acoustic wave source positions are investigated. Time-averaged pressure contour on the plate shows two pressure peaks that are commonly observed in the jet-plate interaction; one by the jet impingement and the other by the plate shock wave. The acoustic fields indicate that there are at least three kinds of acoustic waves in all the cases considered in the study: (i) Mach waves generated from the shear layer of the main jet, (ii) acoustic waves generated from the impingement region, and (iii) Mach waves generated from the shear layer of the supersonic flow downstream of the jet impingement. Indication of the second one (ii) is important because the commonly-used empirical method for the estimation of the acoustic waves from a rocket plume does not consider such acoustic waves. Directivity and sound pressure level of the acoustic waves (ii) and the Mach waves (iii) change strongly with the temperature increase. Directivity and sound pressure level of the acoustic waves (ii) and the Mach waves (iii) change slightly with the nozzle-plate distance increase. The results show that whether the impinging point is inside or outside of potential core does not strongly affect the characteristics of the induced acoustic waves (ii).

Substrate analysis using surface acoustic wave metrology

Abstract: A system for imposing and analyzing surface acoustic waves in a substrate to determine characteristics of the substrate is disclosed. Optical elements and arrangements for imposing and analyzing surface acoustic waves in a substrate are also disclosed. NSOM's, gratings, and nanolight elements may be used to impose surface acoustic waves in a substrate and may also be used to measure transient changes in the substrate due to the passage of surface acoustic waves therethrough.

Apparatus for determining the properties of a medium in the form of a fluid or a soft material

Abstract: An apparatus determines the properties of a medium in the form of a fluid or soft material. An acoustic waveguide has two opposing guide elements delimiting an interior space to be filled with a medium. The guide elements, upon filling the interior space with a medium, form an interface with the medium with an inner surface. A transmitter generates acoustic surface waves in the waveguide, which are received by a receiver. The waveguide can be coupled with an evaluation unit for determining physical properties of the medium based on a signal generated by the receiver. A housing accommodates the guide elements, transmitter and receiver. On the respective inner surface, at least a part of the acoustic surface waves can be converted into volumetric sound waves of the medium and at least a part of the volumetric sound waves can be converted into acoustic surface waves of the waveguide.

Device and method for manipulating particles utilizing surface acoustic waves

Abstract: The present invention provides a device and a method for particle manipulation utilizing interface acoustic waves. The device comprises a cavity (3) for a fluid formed at an interface between a piezoelectric substrate (1) and channel-forming substrate (2). An acoustic generator (4), such as one or more inter digital transducers, is arranged to excite surface acoustic waves which are converted to interface acoustic waves when entering the interface such that acoustic energy is efficiently transferred into the cavity (3) to create standing acoustic waves (6), whereby acoustic primary radiation forces associated with the standing acoustic waves (6) enable to focus or direct the particles (7) suspended in the fluid.

Interferometric imaging of surface acoustic waves on a glass sphere

Abstract: We use an ultrafast optical pump and probe technique to investigate the propagation of subgigahertz surface acoustic waves on a 1 mm diameter glass sphere with an aluminum coating. A fiber-based pump setup generates the surface waves and a common-path interferometer images them in the time domain over the sphere surface as they pass through the pole opposite the source of excitation. Fourier analysis allows the acoustic spectrum of the acoustic source to be extracted and waves traveling in opposite directions to be isolated.

Simultaneous Nearby Measurements of Acoustic Propagation and High-Resolution Sound-Speed Structure Containing Internal Waves

Abstract: During the 2006 Shallow Water (SW06) experiment, simultaneous measurements were made of the sound-speed field as a function of range and depth associated with nonlinear internal waves and acoustic propagation at frequencies of 2-10 kHz over a 1-km path. The internal waves were measured by a towed conductivity-temperature-depth (CTD) chain to get high resolution. These measurements were coordinated so that the nonlinear waves could be interpolated onto the acoustic path, allowing predictions of their effects on the acoustics. Using the measured sound-speed field, the acoustic arrivals under the influence of the internal waves are modeled and compared to data. The largest impact of measured moderate amplitude internal waves on acoustics is that they alter the arrival time of the rays which turn at the thermocline.

Accurate measurement of interferometer group delay using field-compensated scanning white light interferometer

Abstract: Interferometers are key elements in radial velocity (RV) experiments in astronomy observations, and accurate calibration of the group delay of an interferometer is required for high precision measurements. A novel field-compensated white light scanning Michelson interferometer is introduced as an interferometer calibration tool. The optical path difference (OPD) scanning was achieved by translating a compensation prism, such that even if the light source were in low spatial coherence, the interference stays spatially phase coherent over a large interferometer scanning range. In the wavelength region of 500-560 nm, a multimode fiber-coupled LED was used as the light source, and high optical efficiency was essential in elevating the signal-to-noise ratio of the interferogram signal. The achromatic OPD scanning required a one-time calibration, and two methods using dual-laser wavelength references and an iodine absorption spectrum reference were employed and cross-verified. In an experiment measuring the group delay of a fixed Michelson interferometer, Fourier analysis was employed to process the interferogram data. The group delay was determined at an accuracy of 1×10(-5), and the phase angle precision was typically 2.5×10(-6) over the wide wavelength region.

Stabilized detection scheme of surface acoustic waves by Michelson interferometer

Abstract: A new detection scheme of surface acoustic waves by Michelson interferometer has been proposed. A substantial advantage of this scheme lies in its being stabilized against vibration and independent sensitivity of the width of an optical beam. These effects were achieved by creating an interference field on the surface of a photodetector. The measurement scheme proposed was analyzed by means of a numerical modeling method. Experiments confirming the fact of the sensitivity of the proposed detection scheme being independent of vibration and width of optical beam have also been made.

Air-Coupled Seismic Waves at Long Range from Apollo Launchings

Abstract: Microphones and seismographs were co-located in arrays on Skidaway Island, Georgia, for the launchings of Apollo 13 and 14, 374 km to the south. Simultaneous acoustic and seismic waves were recorded for both events at times appropriate to the arrival of the acoustic waves from the source. The acoustic signal is relatively broadband compared to the nearly monochromatic seismic signal; the seismic signal is much more continuous than the more pulse-like acoustic signal; ground loading from the pressure variations of the acoustic waves is shown to be too small to account for the seismic waves; and the measured phase velocities of both acoustic and seismic waves across the local instrument arrays differ by less than 6 per cent and possibly 3 per cent if experimental error is included. It is concluded that the seismic waves are generated by resonant coupling to the acoustic waves along some 10 km of path on Skidaway Island.

Method of and apparatus for measuring strength of ultrasonic waves

Abstract: A method of and an apparatus for measuring the strength of ultrasonic waves are provided. They are capable of measuring the strength of ultrasonic waves easily and at low cost without using a sound pressure meter. The ultrasonic wave strength measuring apparatus has a particle source soaked in a cleaning liquid, an oscillator to generate the ultrasonic waves whose strength is going to be measured to vibrate the particle source so that particles are eluted from the particle source into the cleaning liquid, a counter to count the number of particles in the cleaning liquid, and an operation unit to find the strength of the applied ultrasonic waves based on the counted number of particles.

Defoaming method and device

Abstract: Provided are a deforming method and device that use laser-induced breakdown. The provided method and device make it possible to shorten the focal distance, thereby improving laser beam convergence, and increase the utilization efficiency of sound waves that contribute to defoaming. Pulsed laser light is focused and irradiated into a space inside an acoustic waveguide (4), thereby generating pulsed sound waves from the illumination point (7). The pulsed sound waves propagate down the acoustic waveguide as plane waves, then propagate beyond an open end (16) as spherical waves, and break up a foam outside the open end of the acoustic wave guide.

Hypersonic phononic crystal for surface acoustic waves

Abstract: A phononic crystal exhibiting a band gap in the near-gigahertz frequency range for surface acoustic waves was fabricated in a lithium niobate substrate Reflection and transmission properties of the sample were characterized both electrically and optically, by means of embedded broadband interdigital transducers and optical heterodyne interferometry, respectively Measurements performed for (XZ) propagating surface waves show the existence of a band gap between 660 and 900 MHz Optical measurements confirm that the phononic crystal behaves as a perfect mirror for waves propagating at frequencies within the band gap Outside the band gap, transmission can be observed for frequencies below, but also above the forbidden frequency range, hence showing that losses experienced by high frequency surface acoustic waves, ie for modes located beyond the sound line, can be partially overcome

Acoustic manipulator element

Abstract: According to an exemplary embodiment of the present invention, an acoustic manipulator element is provided. The acoustic manipulator element is arrangable relatively to an acoustic source in a manner that the acoustic manipulator element splits frequency selectively sound waves originating from the acoustic source in a reflected and a through component, wherein at least a portion of the acoustic waves of the through component is attenuated by at most 15 dB for acoustic frequencies having a wavelength between 200 Hz and 16000 Hz compared to the sound waves of the acoustic source.

Properties Investigation of Laser-induced Plasma Sound Waves in Liquids

Abstract: By the piezoelectric transducer hydrophone,laser-induced plasma sound waves in liquids were measured through experiments.Wavelet transform was applied to analyze the spectra characteristics of these signals acquired at different laser energy,different metal solid boundary and different laser wavelength.The results show that laser-induced plasma sound waves frequency range is 0~150 kHz,and changes of the laser energy,the metalboundary underwater and the laser wavelength have little effect on distribution of frequency of waves.Most energy of plasma sound waves is concentrated at the a6 level,and the proportion of the whole energy decreases with the increase of ionization energy of metal.The main frequency of sound waves is within 0~10 kHz,and the frequency peak is 5 kHz.

Reflection of acoustic waves in the real solar atmosphere

Abstract: We use space-time variations of velocity restored from observations to isolate acoustic waves propagating into upper layers of the atmosphere. At reflection, acoustic ten-minute waves penetrate into the evanescent layers of the photosphere up to the temperature-minimum layers, and five-minute waves reach the layers of the lower chromosphere.

Mode‐2 internal waves impact on acoustic signal properties.

Abstract: The properties of mode‐2 internal waves repeatedly observed on the New Jersey Shelf (USA) with high‐frequency acoustic flow visualization systems will be overviewed. The impact of the mode‐2 internal waves on the range/depth distribution of acoustic signal properties will be discussed.

薄膜および微細構造におけるGHz-THz 音響波伝播のイメージング

Abstract: Ultrashort light pulses absorbed in a medium generate both bulk and surface acoustic waves: we focus here on imaging the surface waves and on monitoring the bulk acoustic waves that propagate in the depth direction. This is done in the time domain by delayed probe light pulses. For the bulk acoustic waves, the generated frequency ranges up to 1 THz. Some studies concerning the ultrafast electron-phonon relaxation in metal films, high frequency generation in semiconductor quantum wells, and high frequency shear acoustic wave generation and detection are reviewed here. For the surface acoustic waves the generated frequency ranges up to 1 GHz, and time-resolved two-dimensional images of the propagation are obtained with micron lateral spatial resolution. This imaging method is applied to anisotropic crystals and phononic crystals to elucidate their acoustic properties.

The effect of a surface impedance load on the behavior of quasi-Rayleigh waves near a cylindrical cavity

Abstract: The effect of a surface impedance load on the properties of axisymmetric quasi-Rayleigh waves propagating along the boundaries of a cylindrical cavity is investigated. By solving the problem by means of the impedance method, a dispersion equation for these waves is obtained. It is shown that the equation can be represented as the condition that the determinant of the sum of impedance matrices of the load and the medium is zero. Analysis of this equation allows one to investigate the effect of the surface load on the behavior of quasi-Rayleigh waves and on their critical frequencies. The conditions that should be met by the impedance load for quasi-Rayleigh waves to be absent near the cavity or for one or two such waves to exist are determined. The choice of the load is specified for the propagating quasi-Rayleigh wave to possess preset dispersion properties. The conclusions drawn on the basis of this study are illustrated by several examples of load models that can be implemented in practice.

Propagation of low‐frequency sound through densely sampled internal waves.

Abstract: It is well known that nonlinear internal gravity waves can have a significant effect on acoustic propagation. In particular, horizontal refraction and ducting of sound can occur when the acoustic propagation path is aligned with fronts of internal waves. Additionally, more complicated effects are associated with internal waves that are curved and/or truncated. In this talk, observations of internal waves measured on the New Jersey shelf area of the north Atlantic and their effects on the acoustic field are presented. During the experiment, a low‐frequency source broadcasting continuous tone was towed repeatedly out and back along radials with respect to a VLA. The ship’s track was oriented parallel to the shelf break so that the acoustic propagation path was roughly aligned with internal waves propagating up the shelf. Internal waves were measured at the location of the receivers by temperature sensors on the VLA, at the location of the source by a towed CTD chain, as well as by a cluster of 16 environmen...

Numerical Simulation of Acoustic Waves in a Two-Dimensional Phononic Crystal: Negative Refraction

Abstract: The lens effect of acoustic waves in a two-dimensional (2D) phononic crystal is studied by numerical simulation based on the finite-difference time-domain (FDTD) method. We calculate the phonon band structure of 2D phononic crystals, consisting of metal cylinders placed periodically in water. Lens effect is observed by the negative refraction of acoustic waves, which results in refocusing of the waves at the point outside the crystal. To increase the focal intensity, we introduce a 2D phononic crystal shield with a different composition of material, which returns the incident waves back to the lens via the perfect reflection. Also, the dependence on filling fraction of metal in the crystal is studied.

Research of All-fiber Single-mode Velocity Interferometer

Abstract: Based on the principle of all-fiber single-mode velocity interferometer,a set of experiment equipment was assembled successfully,which was made up of single-mode fiber and couplerIn the experiment,the all-fiber single-mode velocity interferometer realized the measurement of high velocity with a deviation of 14% from a laser vibrometerIn the Hopkinson bar striking experiment,when the reference velocity is 2086m/s,the measurement result is 2057m/sThe feasibility of velocity interferometer is proved