Volume 112, Issue 6, December 2002
- acoustical news—usa
- acoustical news—international
- book reviews
- reviews of acoustical patents
- general linear acoustics 
- nonlinear acoustics 
- aeroacoustics, atmospheric sound 
- underwater sound 
- ultrasonics, quantum acoustics, and physical effects of sound 
- transduction 
- structural acoustics and vibration 
- noise: its effects and control 
- acoustical measurements and instrumentation 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- music and musical instruments 
- bioacoustics 
Index of content:
- REVIEWS OF ACOUSTICAL PATENTS
112(2002); http://dx.doi.org/10.1121/1.1522421View Description Hide Description
The purpose of these acoustical patent reviews is to provide enough information for a Journal reader to decide whether to seek more information from the patent itself. Any opinions expressed here are those of the reviewers as individuals and are not legal opinions. Printed copies of United States Patents may be ordered at $3.00 each from the Commissioner of Patents and Trademarks, Washington, DC 20231. Patents are available via the Internet at http://www.uspto.gov.
- GENERAL LINEAR ACOUSTICS 
112(2002); http://dx.doi.org/10.1121/1.1513365View Description Hide Description
It is commonly known that wave reflections are caused by abrupt spatial variations in the physical parameter called wave impedance. When a material contains a spatially periodic distribution of wave impedances some very interesting and complex wave propagation phenomena will occur. Two examples of such periodic structures immediately come to mind: the first is a sandwiched structure of two types of plates, say for example, identical layers of thin steel plates interspersed with identical thick aluminum plates; and the second is a large number of identical long thin pipes that are connected from end to end with identical short heavy threaded couplings. The pipe assembly is our primary concern here because it represents the drill string, used worldwide to drill for natural energy resources. We want to understand how waves propagate through drill strings because we want to use them as a means of communication. But while the second structure is our primary concern, it is the study of the first structure, composed of layers, that is the truly historical problem and the source of much of our understanding of this rich set of wave physics. Traditionally, wave propagation in periodic media has been studied as an eigenvalue problem. The eigenvalues themselves yield information about phase velocities, group velocities, passbands, and stopbands. Most often the analysis has stopped there and the eigenvectors have been ignored. Here we turn our attention to the eigenvectors, using them to evaluate the impedance of the periodic structure with particular emphasis on the periodic drill string. As you might expect the impedance of the drill string is a complex number, which is evaluated from a very complicated expression. However, we have discovered that the impedance at two physical locations along the length of each piece of drill pipe in the drill string always reduces to a real number. This is immensely important because it allows us to match the impedance of the drill string to our communication devices. We show how this leads to the effective design of repeaters, noise cancelers, wave terminators, and quarter-wave transformers for a drill-string communication system.
A vertical eigenfunction expansion for the propagation of sound in a downward-refracting atmosphere over a complex impedance plane112(2002); http://dx.doi.org/10.1121/1.1514930View Description Hide Description
The propagation of sound in a stratified downward-refracting atmosphere over a complex impedance plane is studied. The problem is solved by separating the wave equation into vertical and horizontal parts. The vertical part has non-self-adjoint boundary conditions, so that the well-known expansion in orthonormal eigenfunctions cannot be used. Instead, a less widely known eigenfunction expansion for non-self-adjoint ordinary differential operators is employed. As in the self-adjoint case, this expansion separates the acoustic field into a ducted part, expressed as a sum over modes which decrease exponentially with height, and an upwardly propagating part, expressed as an integral over modes which are asymptotically (with height) plane waves. The eigenvalues associated with the modes in this eigenfunction expansion are, in general, complex valued. A technique is introduced which expresses the non-self-adjoint problem as a perturbation of a self-adjoint one, allowing one to efficiently find the complex eigenvalues without having to resort to searches in the complex plane. Finally, an application is made to a model for the nighttime boundary layer.
112(2002); http://dx.doi.org/10.1121/1.1512700View Description Hide Description
This study is devoted to deducing exact elastic constants of an anisotropic solid material without using any advance information on the elastic constants by incorporating a displacement-distribution measurement into resonant ultrasound spectroscopy (RUS). The usual RUS method measures free-vibration resonance frequencies of a solid and compares them with calculations to find the most suitable set of elastic constants by an inverse calculation. This comparison requires mode identification for the measured resonance frequencies, which has been difficult and never been free from ambiguity. This study then adopts a laser-Doppler interferometer to measure the displacement-distribution patterns on a surface of the vibrating specimen mounted on pinducers; comparison of the measured displacement distributions with those computed permits us to correctly identify the measured resonance frequencies, leading to unmistakable determination of elastic constants. Because the displacement patterns are hardly affected by the elastic constants, an exact answer is surely obtained even when unreasonable elastic constants are used as initial guesses at the beginning of the inverse calculation. The usefulness of the present technique is demonstrated with an aluminumalloy and a langasite crystal.
112(2002); http://dx.doi.org/10.1121/1.1511756View Description Hide Description
Complex degree of coherence functions are computed using synthetic and measured ultrasound data to demonstrate noteworthy aspects of coherenceanalysis in the context of aberration correction. Coherence functions calculated from synthetic data illustrate the importance of proper normalization of the constituent cross-correlation integrals when weak elements and receiver directivity are significant factors. The synthetic data also show that a spike can occur at the zero-lag position of the coherence function when the signal-to-noise ratio is reduced by element directivity near the edges of a large aperture. The latter observation is confirmed by experimental data acquired through tissue-mimicking distributed aberration phantoms using a low f-number two-dimensional array system. The coherence of data acquired at neighboring elements is not changed by time-shift compensation of transmit and receive focusing, but time-shift compensation does improve the coherence of echoes measured over larger separations. The resulting increase in coherence widths evaluated at levels between 0.2 and 0.5 is correlated with narrower −10 dB and −20 dB effective widths in focuses visualized using single-transmit images. Iterative focus compensation methods may benefit from aberration estimation algorithms that take advantage of these longer-range correlations in random-scattering waveforms.
112(2002); http://dx.doi.org/10.1121/1.1500756View Description Hide Description
The interaction of the low-order antisymmetric and symmetric Lamb waves with vertical cracks in aluminum plates is studied. Two types of slots are considered: (a) internal crack symmetrical with respect to the middle plane of the plate and (b) opening crack. The modal decomposition method is used to predict the reflection and transmission coefficients and also the through-thickness displacement fields on both sides of slots of various heights. The model assumes strip plates and cracks, thus considering two-dimensional plane strain conditions. However, mode conversion into and vice versa) that occurs for single opening cracks is considered. The energy balance is always calculated from the reflection and transmission coefficients, in order to check the validity of the results. These coefficients together with the through-thickness displacement fields are also compared to those predicted using a finite element code widely used in the past for modeling Lamb mode diffraction problems. Experiments are also made for measuring the reflection and transmission coefficients for incident or lamb modes on opening cracks, and compared to the numerical predictions.
112(2002); http://dx.doi.org/10.1121/1.1510139View Description Hide Description
The discrepancy between reverberation times of an enclosed sound fieldmeasured by the steady-state method and by the transient decay method is well-known. So far, no clear explanation has been obtained. In this paper, the steady-state bandlimited energy in an enclosure and bandlimited power flow into modally reactive boundaries are derived to describe the energy balance relationship and thus the reverberation time in a frequency band. This reverberation time is then compared to that obtained from the transient decay of the sound field based on the modal analysis. The comparison provides an understanding of the discrepancy mentioned above as well as the physical interpretations of the reverberation times estimated by both methods.
The low-frequency reflection and scattering of the Lamb mode from a circular through-thickness hole in a plate: Finite Element, analytical and experimental studies112(2002); http://dx.doi.org/10.1121/1.1512292View Description Hide Description
A study of the interaction of the Lamb wave with a circular through-thickness hole in a plate is presented. The study is limited to the nondispersive frequency range of this wave, in which the distributions of stress and displacement are simple. This allows a Finite Element analysis to be undertaken using a two-dimensional membrane discretization. Predictions of the direct reflection of the mode and the lateral scattering of the mode are made for a range of diameters of the hole. At the same time, an analytical solution based on modal superposition is developed, and this is also used to predict the reflection and scattering coefficients. Both sets of predictions are validated by experimental measurements. It is found that the trends of the reflection coefficients for different hole diameters, frequencies and distances from the hole satisfy a simple normalization. On a detailed scale, the functions exhibit undulations which are shown to result from the interference of the direct reflection with secondary reflections which arrive slightly later.
112(2002); http://dx.doi.org/10.1121/1.1512699View Description Hide Description
Sound transmission across a nonuniform section in an infinite duct is studied numerically using the finite element method. An impedance matched absorptive portion is added to each end of the computational domain so as to avoid the undesirable higher mode reflection that will otherwise take place there. Results suggest that the sound fields downstream of the nonuniform section inlet are complicated and cannot be easily described by the conventional solution of the wave equation. The distribution of acoustic energy among the various propagating modes well downstream from the outlet of the nonuniform section is also discussed. Results show that the first symmetrical higher mode is important for all cases. The plane wave becomes important at high frequency with high rate of change of the cross-sectional area when the section is a convergent one.
The low frequency reflection characteristics of the fundamental antisymmetric Lamb wave from a rectangular notch in a plate112(2002); http://dx.doi.org/10.1121/1.1512702View Description Hide Description
An analysis of the reflection of the fundamental Lamb mode from surface-breaking rectangular notches in isotropic plates is presented. The results are obtained from finite element time domain simulations together with experimental measurements. Good agreement is found between the simulations and the measurements. Results are shown for a range of notch widths and depths, including the special case of a crack, defined as a zero-width notch. The reflection coefficient, when plotted as a function of the notch width, exhibits a cosinusoidal periodic shape, and this is explained by interference between the separate reflections from the start and the end of the notch. The reflection coefficient, when plotted as a function of notch depth, shows that in general the reflection increases with both frequency and notch depth, but the shapes of the functions are complex and there are some surprising features. An analysis of the reflection from cracks using the S-parameter scattering approach and some simplified descriptions of the crack-opening behavior yields physical explanations of the nature of these reflection functions. It is found that opening of the crack can be described adequately by a quasistatic assumption only when the crack is small, and in other cases a ray theory approach is more representative. The reflection function is shown to be a result of contributions from both the axial stress and the shear stress in the wave, and the relative importance of these varies with the crack depth and the frequency.
Analysis of piezoelectric strip waveguides based on the effective index and pseudospectral element methods112(2002); http://dx.doi.org/10.1121/1.1512293View Description Hide Description
Integrated acousto-optical circuits in are attractive devices for applications especially in advanced WDM systems. In order to increase the scale of integration and to reduce the RF driving power of these devices, one promising approach is to use acoustical waveguides with smaller lateral dimensions. In this paper the combination of a pseudospectral elements method (PSEM) and an effective index method (EIM) for the analysis of film-loaded surface acoustic waveguides (SAWG’s) is presented. Numerical results demonstrate the exponential rate of convergence of the PSEM and agree with the computations performed via the transverse resonance technique. Due to the exponential rate of convergence of the PSEM and to a mapping transformation in the substrate, the piezoelectric problem in the depth direction of the structures is evaluated by a low number of Legendre polynomials. The method is applied to the analysis of several layered SAWG’s of practical interest for AO devices, such as in which the metal is either Au, Al, In, or Ti.
Tube-wave propagation in a fluid-filled borehole generated by a single point force applied to the surrounding formation112(2002); http://dx.doi.org/10.1121/1.1508781View Description Hide Description
Propagation of tube waves in an infinite fluid-filled borehole, generated by a single-force point source placed in the elastic surrounding formation, is analyzed in the long-wave approximation. Integral representations of the precise solution are obtained both for fast and slow formations. An asymptotic analysis of tube-wave propagation in the fluid-filled borehole is performed on the basis of these two integral representations. The complete asymptotic wave field in the borehole fluid for a fast formation consists of and phases and the lowest eigenmode of the Stoneley wave (tube wave). For a slow formation the conical Stoneley wave(Machwave) is generated. It appears only behind the critical angle defined by the ratio of the wavevelocity in the formation to the low-frequency Stoneley wavevelocity and decays weakly with an offset. Asymptotic wave forms are in good agreement with wave forms obtained by straightforward calculations.
112(2002); http://dx.doi.org/10.1121/1.1517254View Description Hide Description
A simplified boundary element method(BEM) for dealing with high-frequency sound is proposed. The boundary integralequation is modified into a quadratic form to enable the prediction of sound levels in the one-third octave band analysis. Monopole and dipole source terms in the conventional BEM are transformed into the auto- and cross-spectra of two vibrating sources, in which the cross-spectra are eventually neglected by assuming that the correlation coefficients involved are negligible. The present method is compared with the Rayleigh integral for calculating the sound pressure radiated from a baffled panel, in terms of the application limit. The characteristic length of the boundary element and the applicable frequency range can be determined by the lower limit value of the correlation coefficient. As a test example, the field pressure radiated from a partially vibrating sphere is predicted and the resultant trend is in good agreement with the analytic solution as far as the related correlation coefficient satisfies the assumption. The overdetermination process for overcoming nonuniqueness in exterior radiation problems is unnecessary in the present method because phase information can be ignored. The results of the calculation show that the proposed method is acceptable for solving the exterior radiation problem at a high-frequency range in a timely manner.
- NONLINEAR ACOUSTICS 
Supercritical parametric phase conjugation of ultrasound. Numerical simulation of nonlinear and nonstationary mode112(2002); http://dx.doi.org/10.1121/1.1506687View Description Hide Description
This paper investigates the saturation mechanism of the nonstationary supercritical mode of parametric wavephase conjugation in a magnetostrictive medium. The numerical simulation considers the two most probable nonlinear mechanisms of interaction between elastic deformation and electromagnetic excitation. For the qualitative study of the dynamics of the system, a one-dimensional numerical simulation is sufficient if applied to an infinite medium with a finite active zone. The temporal form of the conjugate wave is obtained for both hypotheses. Comparison with experiments shows that only one mechanism corresponds to the experimental behavior.
Strain wave evolution equation for nonlinear propagation in materials with mesoscopic mechanical elements112(2002); http://dx.doi.org/10.1121/1.1517252View Description Hide Description
Nonlinear wave propagation in materials, where distribution function of mesoscopic mechanical elements has very different scales of variation along and normally to diagonal of Preisach–Mayergoyz space, is analyzed. An evolution equation for strain wave, which takes into account localization of element distribution near the diagonal and its slow variation along the diagonal, is proposed. The evolution equation provides opportunity to model propagation of elastic waves with strain amplitudes comparable to and even higher than characteristic scale of element localization near Preisach–Mayergoyz space diagonal. Analytical solutions of evolution equation predict nonmonotonous dependence of waveabsorption on its amplitude in a particular regime. The regime of self-induced absorption for small-amplitude nonlinear waves is followed by the regime of self-induced transparency for high-amplitude waves. The developed theory might be useful in seismology, in high-pressure nonlinear acoustics, and in nonlinear acoustic diagnostics of damaged and fatigued materials.