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The sound wave in a cylindrical steel bar, generated by a light tap on one of its ends, is recorded by a microphone located near the other end. A sound analysis software is used to obtain the resonance spectrum of the bar. Longitudinal and flexural vibration frequencies are obtained from the peaks of the spectrum. The speed of sound, Young's modulus, and Poisson's ratio of steel are obtained. [c] 2010 American Association of Physics Teachers. [DOI: 10.1119/1.3493403]

Acoustic lenses are employed in a variety of applications, from biomedical imaging and surgery to defense systems and damage detection in materials. Focused acoustic signals, for example, enable ultrasonic transducers to image the interior of the human body. Currently however the performance of acoustic devices is limited by their linear operational envelope, which implies relatively inaccurate focusing and low focal power. Here we show a dramatic focusing effect and the generation of compact acoustic pulses (sound bullets) in solid and fluid media, with energies orders of magnitude greater than previously achievable. This focusing is made possible by a tunable, nonlinear acoustic lens, which consists of ordered arrays of granular chains. The amplitude, size, and location of the sound bullets can be controlled by varying the static precompression of the chains. Theory and numerical simulations demonstrate the focusing effect, and photoelasticity experiments corroborate it. Our nonlinear lens permits a qualitatively new way of generating high-energy acoustic pulses, which may improve imaging capabilities through increased accuracy and signalto-noise ratios and may lead to more effective nonintrusive scalpels, for example, for cancer treatment. acoustic focusing | nonlinear dynamics | solitary waves | sonic imaging | granular crystals doi/ 10.1073/pnas.1001514107

A new structure is proposed that is composed of reflector plated mounted in front and in back of the transducer at an angle of 45[degree], so that acoustic waves from front and back of the transducer are combined to form a single main beam. The analysis has shown that far field directivity has become sharper and acoustic pressure output is doubled.

Approximate forms for the Green's function are used, which are based on rigorous representations, can represent the Green's function to any required degree of accuracy and can be applied to any type of substrate and acoustic wave. The practical application of the methods is shown by examples of longitudinally coupled resonator filter (LCRF) designs implemented using leaky wave cuts of lithium tantalate.

Zinc-oxide-based thin-film bulk acoustic wave (BAW) resonators are examined with respect to variation of dimensions of a boundary frame spurious mode suppression structure. The simple semi-2-D plate model has predicted the device behavior, the 2-D finite element method results have coincided with them with some additional effects and breaking the resonator behavior down to eigenmodes have provided insights into the physics of the device operation.

Optical holographic interferometry was used to study standing sound waves in air inside a resonance tube driven by a small loudspeaker at one end. The front face of the resonance tube was constructed with plexiglass, allowing optical interrogation of the tube interior. The object beam of the holographic setup was directed through the plexiglass and reflected off the back wall of the resonator. When driven at resonance, the fluctuations in the air density at the antinodes altered the refractive index of the air in the tube, causing interference patterns in the resulting holographic images. Real-time holography was used to determine resonance frequencies and to measure the wavelengths of the standing waves. Time-average holography was used to observe the effect of increasing the sound pressure level on the resulting fringe pattern. A simple theory was developed to successfully predict the fringe pattern. [DOI: 10.1119/1.3147683]

Full-wave analysis of piezoelectric boundary acoustic waves (PBAWs) propagating along a metallic grating sandwiched between 2 semi-infinite layers is described. The studies have shown that both the shear-horizontal (SH) type and Rayleigh-type PBAWs are supported in the structure and thus spurious responses due to the Rayleigh-type PBAW is completely suppressed for device implementation.

The langatate elastic and piezoelectric constants and their associated temperature coefficients are determined by using 2 independent methods, the pulse echo overlap (PEO) and a combined resonance technique (CRT) to measure bulk acoustic wave (BAW) phase velocities. The temperature behavior of the BAW modes is extracted by using the CRT technique and the extracted temperature coefficients for the elastic and piezoelectric constants between room temperature and 120[degree]C are discussed.

Weakly nonlinear behavior of electric power transmission through an elastic wall by piezoelectric transducers and acoustic waves near resonance is analyzed by using the cubic theory of nonlinear electroelasticity. The studies have shown that near nonlinear resonance the electrical input-output relation has lost its linearity, has become multi-valued and has jumped due to large mechanical deformations.

High-Q resonators with a symmetric composite layer Si[O.sub.2]-AlN[Si[O.sub.2] between the electrodes are developed. The temperature drift has disclosed the impact of the Si[O.sub.2] layers, which is more pronounced on the first harmonic, reducing the TCF to 4 ppm/K for the 3rd harmonic of the 310 nm oxide devices.

The article discusses the results that are obtained when an iterative high-resolution wavenumber inversion algorithm is applied to the broadband acoustic waveguides. The approach is shown to be extremely effective in enhancing the efficiency of the algorithm in the presence of experimental noise.

The characteristics of surface acoustic wave (SAW) filters composed of interdigital Schottky and ohmic contacts were examined for evaluating the properties of SAWs in reverse-biased AlGaN/GaN heterostructures on (0001) sapphire substrates. Findings reveal a change in the response of the onsets of SAW signals to the spatial variation of the threshold voltage.

A method for determining the main reflection, transmission and scattering parameters for short metal reflectors is presented. Results suggest that the proposed method is simple and fast for the characterization of single-electrode reflectors.

The synthesis and bulk acoustic wave (BAW) properties on the dual mode frequency shift of solidly mounted resonators are discussed. A nonlinear declining trend with a linear increase of the mass loading is observed in case of dual-resonance frequencies.

Elastic constants of the amorphous TeO2+x films deposited by RF dioxide sputtering under varying oxygen percentage in reactive gas mixture are studied. It is seen that the anomalous elastic properties of the [TeO.sub.2+x] films grown in 100% O2 are useful for potential application in the design of temperature stable surface acoustic wave devices.

A classical ultraviolet photolithography was used to fabricate a GHz surface acoustic wave (SAW) device based on a ZnO/Si structure. The characterization of different high-frequency modes with an advanced finite-element/boundary-element based model allowed accurate design of SAW devices.

A formulation based on Mindlin's piezoelectric plate theory and the plane wave expansion method is used to study the frequency band gap and dispersion relations of the lower-order Lamb waves in two-dimensional piezoelectric phononic plates. The formulation is can be applied to study the phononic plates composed of solid-solid and air-solid constituents with square and triangular lattices respectively.

We have designed, simulated, fabricated, and tested an ultra-wideband (UWB) multifunctional communication and radar system utilizing a single shared transmitting antenna aperture. Two surface acoustic wave bandpass chirp filters were used to modulate the radar and communications pulses, generating linear frequency modulation waveforms with opposite slope factors. The system operates at a center frequency of 750 MHz with 500 MHz of instantaneous bandwidth. The measured range resolution is 63 cm (25 in) using targets with a radar cross section of 2.7 [m.sup.2]. The probability of detection was measured to be 99%, and the probability of false alarm was 7% with the communication and radar systems operating simultaneously. The bit error rate for simultaneous communication at 1 Mb/s, and radar at 150 kHz pulse repetition frequency and 1.5-ns pulsewidth is 2e-3. Our UWB multifunctional system demonstrates the ability to simultaneously interrogate the environment and communicate through a shared transmitting antenna aperture, while realizing a simple system architecture with low output power and not employing time-division multiplexing. Index Terms--Chirp, communications, radar, RF.

The authors have developed a neural network to predict cut-off dimensionless frequencies of the antisymmetric circumferential waves propagating around an elastic circular cylindrical shell of different radius ratio. The cut-off dimensionless frequencies and the evolution of the group and phase velocities relative to the frequencies can be evaluated with precision.

A fully integrated two-port surface acoustic wave (SAW) resonator, fabricated using a standard 0.6-[micro]m complementary metal-oxide semiconductor (CMOS) process is described in this paper. Only three micromachining processes, namely, reactive ion etching, zinc-oxide deposition, and wet etching, implemented subsequent to the standard process, are required to realize these resonators. Three design examples of these resonators are given to demonstrate the characteristics of these resonators at different operating frequencies. Experimental measurements of the [S.sub.21] transmission characteristics were conducted on the fabricated resonators and they were found to have parallel resonant frequencies of 1.02 GHz, 941 MHz, and 605 MHz and quality (Q) factors of 44, 86, and 285, respectively. Based on these measurements and the fabrication layers of the device, an equivalent-circuit model tailored specifically for standard CMOS two-port resonators was developed. Finite-element modeling of the SAW resonators was performed to verify the measured series resonant frequency. Comparison between the developed model and measurement characteristics was also presented. Improvement in Q factor was observed when reflector height was increased. Index Terms--Complementary metal-oxide semiconductor (CMOS), equivalent circuit, micromachining, piezoelectric resonator, surface acoustic wave (SAW) resonator.

Study is presented in which a formed laser source, using a four-element lenticular array is used in the ablative regime to generate select, narrowband, acoustic waves. A simplified concept is presented to explain the effect of a line array source on the frequency content of acoustic waves.

The propagation of waves along a one-dimensional 'diatomic' chain made up to welded spheres is analyzed in terms of frequency spectrum and the influence of the parity of the number of the spheres in the chain is underlined. Depending on the parity of the number of spheres in the finite chain and on the ratio between the masses of the spheres, it points out that localized modes might appear in the band gap.

Different means of stopping the spurious impact produced by lateral modes in thickness-excited film bulk acoustic wave resonators (FBAR) are investigated by a study of the shape of electrodes. The problem is solved by the development and explanation of a new elliptical electrode shape to subdue spurious modes.

The nonlinear interaction of sound waves in air is applied to sound reproduction for audio applications where a directional audible sound is generated by amplitude-modulating the ultrasound carrier with an audio signal then transmitting it from a parametric loudspeaker. The result indicates that five-dimensional integral expressions for the second-order sound fields are simplified to one-dimensional integrals.

Force frequency coefficients of a Y-cut langanite (LGN) resonator and a Y-cut langatate (LGT) resonator as a function of the azimuthal angle is measured. The maximum magnitudes of the coefficients of the LGN and the LGT are five and seven times smaller than that of stress compensated cut (SC-cut) quartz.

Force frequency coefficients of a Y-cut langanite (LGN) resonator and a Y-cut langatate (LGT) resonator as a function of the azimuthal angle is measured. The maximum magnitudes of the coefficients of the LGN and the LGT are five and seven times smaller than that of stress compensated cut (SC-cut) quartz.

We describe the detection of bursts of surface acoustic waves by a double-pulsed TV holography technique. We describe mathematically the long- and short-wave bursts in the output correlograms and validate theoretical results with experimental images. The use of short-wave bursts permits us to scan the surface and makes it easier to distinguish, for purposes of nondestructive testing, the disturbances produced by flaws. OCIS codes: 120.6160, 120.4290, 240.6690.

The aim of this work was to measure and compare the binding constants of antibody immunoglobulin G (IgG) to bacterial cell wall proteins, streptococcal protein G and Staphylococcus aureus protein A, using an acoustic wave sensor. Devices, which used shear-horizontal acoustic waves propagating in a waveguide configuration at 108 and 155 MHz, were employed in the detection of apparent IgG binding constants at the solid-liquid interface in the range of 6.7-667 nM IgG. Real-time data during IgG-protein G and IgG-protein A binding yielded apparent association constants of 3.29 x [10.sup.4] and 8.02 x [10.sup.3] [M.sup.-1] [s.sup.-1] leading to equilibrium constants of 1.13 x [10.sup.8] and 2.90 x [10.sup.7] [M.sup.-1], respectively. The measured apparent rate constants are consistent with literature reports of higher affinity of protein G for IgG. Furthermore, protein binding through the Fc region of IgG is suggested to occur below 333 nM, while different mechanisms are suggested to occur above 333 nM. For the first time, nonequilibrium studies of IgG-protein G and A binding at a solid-liquid interface has yielded valuable quantitative kinetic information about binding mechanisms. The promise of this detection method is shown by providing quick determination of binding constants with low sample volumes.

A great deal of progress has been made in the modeling of aerodynamically generated sound of rotors over the past decade. Although the modeling effort has focused on helicopter main rotors, the theory is generally valid for a wide range of rotor configurations. The Ffowcs Williams-Hawkings (FW-H) equation has been the foundation for much of the development. The monopole and dipole source terms of the FW-H equation account for the thickness and loading noise, respectively. Blade-vortex-interaction noise and broadband noise are important types of loading noise, hence much research has been directed toward the accurate modeling of these noise mechanisms. Both subsonic and supersonic quadrupole noise formulations have been developed for the prediction of high-speed impulsive noise. In an effort to eliminate the need to compute the quadrupole contribution, the FW-H equation has also been utilized on permeable surfaces surrounding all physical noise sources. Comparisons of the Kirchhoff formulation for moving surfaces with the FW-H equation have shown that the Kirchhoff formulation for moving surfaces can give erroneous results for aeroacoustic problems. Finally, significant progress has been made incorporating the rotor noise models into full vehicle noise prediction tools.

The MARTEL test rig of Centre National d'Etudes Spatiales, located in Poitiers, France, is designed to study the noise of highly supersonic hot jets under conditions approaching those of a launch vehicle at liftoff. The nonanechoic character of the site (concrete ground, large plate representing the launch pad) requires a specific measurement device in order to calculate the sound power radiated by the jets. The integration process defined by ONERA is discussed and is tested using a freejet noise model derived from the work of NASA, which has been extended to the jet-plate interaction by assuming that the sound power radiated by the jet remains unchanged in this case. First results concerning jets of various velocities seem to confirm the preceding hypothesis and the reliability of the method used.

The Galerkin/least squares (GLS) modification improves the performance of finite-element computations of time-harmonic acoustics at high wave numbers. The design of the GLS resolution-dependent method parameter for two-dimensional computation in previous work was based on dispersion analysis of one-dimensional and square bilinear elements. We analyze the dispersion of linear triangular finite elements, and define method parameters that eliminate dispersion on a hexagonal patch. Numerical tests compare the performance of the proposed method with established techniques on structured and unstructured triangular meshes. Based on this work, we propose a method parameter that may be used for computation with both linear triangular and bilinear quadrilateral elements. CE Database keywords: Dispersion; Finite elements; Acoustic waves; Triangles.

A zero flow, fully three-dimensional, variable impedance, rectangular duct aeroacoustics code that spans the frequency spectrum of interest in duct liner research is developed. The governing equations and boundary conditions in the duct are solved numerically using the finite element methodology. The methodology makes use of a state-of-the-art, sparse equation solver to obtain the capability to study high-frequency sound waves that may require millions of grid points for resolution. Noise suppression levels predicted from the code are in excellent agreement with those obtained from mode theory. The single-processor performance of the solver, relative to that of the more commonly used band solver, increases with frequency. At a frequency of 17 kHz, the band solver is 4.25 times slower and consumes 2.5 times more memory than the fully sparse equation solver. The duct aeroacoustics code is combined with an optimization algorithm and used successfully to educe the impedance spectrum of a ceramic liner. The primary problem with using the methodology to perform optimization studies at frequencies above 14 kHz is excessive central processor unit time. The results support the recommendation that research be directed toward exploitation of the multiprocessor capability of the solver to further reduce central processor unit time.

The flow surrounding an abruptly deflected wedge in a uniform stream with upstream Mach number near one is investigated. Asymptotic techniques are employed to formulate the appropriate unsteady transonic small disturbance model of the problem on which numerical calculation is performed. The development of the shock patterns and the approach to steady date is presented in subsonic, sonic and supersonic cases.

Stroboscopic holographic interferometry has been developed at an advanced undergraduate level allowing real-time imaging of standing sound waves in gas filled, closed tube resonators. A heterodyne Mach-Zehnder interferometer was first built by students to show the feasibility of interferometric detection of sound waves in a small cell. In the subsequent holographic study, the laser irradiance is modulated by an acousto-optic cell at frequencies near that of the standing wave, and a video camera records the fringe motion due to sound pressure changes. Fractional fringe shifts are observed for an air filled cell, and multiple fringe shifts are imaged for the case of freon. Sound reflections from the cell ends are easily observed, with nonsinusoidal waveforms dominating at high intensities due to superposition of resonator harmonics.

A new algorithm handles the near-field problem by utilizing a uniform linear array. An ideal covariance matrix associated with far-field signals having the same bearings as near-field signals is constructed based on a far-field approximation covariance matrix from the characteristics of the wavefront shape of near-field signals and the signal covariance matrix of incoherent far-field sources. The properties and the simulation effects, exhibiting the efficiency of this suggested approach, are studied.