Volume 113, Issue 6, June 2003
- acoustical news—usa
- acoustical news—international
- reviews of acoustical patents
- letters to the editor
- 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 
- architectural acoustics 
- acoustical measurements and instrumentation 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech processing and communication systems 
- bioacoustics 
Index of content:
- REVIEWS OF ACOUSTICAL PATENTS
113(2003); http://dx.doi.org/10.1121/1.1574044View 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.
- LETTERS TO THE EDITOR
113(2003); http://dx.doi.org/10.1121/1.1570436View Description Hide Description
The possibility of recovering the Green’s function from the field-field correlations of coda waves in an open multiple scattering medium is investigated. The argument is based on fundamental symmetries of reciprocity, time-reversal invariance, and the Helmholtz–Kirchhoff theorem. A criterion is defined, indicating how sources should be placed inside an open medium in order to recover the Green’s function between two passive receivers. The case of noise sources is also discussed. Numerical experiments of ultrasonicwave propagation in a multiple scattering medium are presented to support the argument.
113(2003); http://dx.doi.org/10.1121/1.1572136View Description Hide Description
An unresolved issue in the author’s Ph.D. thesis concerned the relation between turbulent flow speed and the maximum response of a string excited by the turbulence. The maximum response occurred at a flow speed significantly less than that predicted. This discrepancy was not resolved at the time, but can be resolved if one notes that the flow excitation is dispersive, with longer scale disturbances that flow faster than smaller scale disturbances. It is suggested that string response to turbulence may be a useful way to determine small-scale properties of a turbulent flow.
Comment on “Multiple scattering in a reflecting cavity: Application to fish counting in a tank” [J. Acoust. Soc. Am. 109, 2587–2597 (2001)] (L)113(2003); http://dx.doi.org/10.1121/1.1569938View Description Hide Description
113(2003); http://dx.doi.org/10.1121/1.1572145View Description Hide Description
Results are presented from Arctic field trials carried out to estimate the bearing to acoustic sources in the water column using seismic particle motion measured at a tri-axial geophone mounted on the sea ice surface. Source bearings are estimated by applying polarization filters to suppress seismic waves with transverse particle motion and computing the incident power rotated into radial look angles from 0° to 360°; the inherent 180° ambiguity is resolved by requiring out-going (prograde) particle motion in the vertical-radial plane. An earlier study considered impulsive sources at ranges of 200–1000 m at a site characterized by mixed annual ice. The present work considers two studies of similar scale carried out at sites with uniformly smooth annual ice and rough, ridged annual ice, and a third study on multi-year ice involving sources at 2–50-km range. The results indicate good bearing estimation to long range with little dependence on ice type.
113(2003); http://dx.doi.org/10.1121/1.1570435View Description Hide Description
Informational masking (IM) has a long history and is currently receiving considerable attention. Nevertheless, there is no clear and generally accepted picture of how IM should be defined, and once defined, explained. In this letter, consideration is given to the problems of defining IM and specifying research that is needed to better understand and model IM.
113(2003); http://dx.doi.org/10.1121/1.1572137View Description Hide Description
Acoustic data from two sperm whale neonates (Physeter macrocephalus) in rehabilitation are presented and implications for sound production and function are discussed. The clicks of neonate sperm whale are very different from usual clicks of adult specimens in that neonate clicks are of low directionality [SL anomaly (0°–90°) <8 dB], long duration (2–12 ms), and low frequency (centroid frequency between 300 and 1700 Hz) with estimated SLs between 140 and 162 dB//1 μPa (rms). Such neonate clicks are unsuited for biosonar, but can potentially convey homing information between calves and submerged conspecifics in open ocean waters at ranges of some 2 km. Moreover, it is demonstrated that sperm whale clicks are produced at the anterior placed monkey lips, thereby substantiating a key point in the modified Norris and Harvey theory and supporting the unifying theory of sound production in odontocetes.
- GENERAL LINEAR ACOUSTICS 
113(2003); http://dx.doi.org/10.1121/1.1570444View Description Hide Description
The scattering of elastic waves in a medium with damage from microcracking is discussed. The influence of damage from penny-shaped microcracks within a homogeneous medium is considered. The microcracks are assumed to be randomly oriented and uniformly distributed. Explicit expressions are derived for the attenuation of longitudinal and shear elastic waves in terms of the damage parameter and the effective elastic moduli of the medium. A generalized tensor-based approach is used such that the results are coordinate free. The derivation is based upon diagrammatic methods. The problem is formulated in terms of the Dyson equation, which is solved for the mean field response within the limits of the first-order smoothing approximation. The longitudinal and shear attenuations are discussed in terms of their frequency dependence and damage dependence. In particular, the attenuations are shown to scale linearly with the damage parameter.
113(2003); http://dx.doi.org/10.1121/1.1572141View Description Hide Description
An exact, analytical solution is developed for the problem of acoustic-wave scattering from a cluster of ideal, gaseous, spherical bubbles in an unbounded, homogeneous, host fluid. This solution takes into account all modes of oscillation of the bubbles as well as all interactions between them; it is applicable to a wide range of bubble sizes and excitation frequencies. In the low frequency regime, the theory of this paper is shown to reduce to the “monopole” approximation, the effect of higher-order modes being non-negligible only for very small bubble-to-bubble separations. A numerical study of interactive backscattering from small clusters, comprising up to three ideal bubbles, is presented. Interactions between the bubbles are shown to produce downward shifts in the resonance frequency of the cluster, when the scattering configuration is symmetric. Furthermore, asymmetries of the scattering configuration are shown to generate sharp resonances at frequencies above the resonance of the symmetric mode. The results of this paper agree with previous theoretical and experimental work.
113(2003); http://dx.doi.org/10.1121/1.1572139View Description Hide Description
Elastic wave scattering off a layer containing a single set of vertical periodic fractures is examined using a numerical technique based on the work of Hennion et al. [J. Acoust. Soc. Am. 87, 1861–1870 (1990)]. This technique combines the finite element method and plane wave method to simulate three-dimensional scattering off a two-dimensional fractured layer structure. Each fracture is modeled explicitly, so that the model can simulate both discrete arrivals of scatteredwaves from individual fractures and multiply scatteredwaves between the fractures. Using this technique, we examine changes in scatteringcharacteristics of plane elastic waves as a function of wave frequency, angle of incidence, and fracture properties such as fracture stiffness, height, and regular and irregular spacing.
Including dispersion and attenuation directly in the time domain for wave propagation in isotropic media113(2003); http://dx.doi.org/10.1121/1.1572143View Description Hide Description
When sound propagates in a lossy fluid, causality dictates that in most cases the presence of attenuation is accompanied by dispersion. The ability to incorporate attenuation and its causal companion, dispersion, directly in the time domain has received little attention. Szabo [J. Acoust. Soc. Am. 96, 491–500 (1994)] showed that attenuation and dispersion in a linear medium can be accounted for in the linear wave equation by the inclusion of a causal convolutional propagation operator that includes both phenomena. Szabo’s work was restricted to media with a power-law attenuation. Waters et al. [J. Acoust. Soc. Am. 108, 2114–2119 (2000)] showed that Szabo’s approach could be used in a broader class of media. Direct application of Szabo’s formalism is still lacking. To evaluate the concept of the causal convolutional propagation operator as introduced by Szabo, the operator is applied to pulse propagation in an isotropic lossy medium directly in the time domain. The generalized linear wave equation containing the operator is solved via a finite-difference-time-domain scheme. Two functional forms for the attenuation often encountered in acoustics are examined. It is shown that the presence of the operator correctly incorporates both, attenuation and dispersion.
Prediction and measurement of nonpropagating Lamb modes at the free end of a plate when the fundamental antisymmetric mode is incident113(2003); http://dx.doi.org/10.1121/1.1568758View Description Hide Description
Reflection of Lamb waves when the fundamental mode is incident at the free end of a plate is studied, in order to identify the extent to which the generation of nonpropagating modes influences the field local to the end of the plate. Semi-analytical predictions, finite element simulations, and experimental measurements are presented for frequencies below the cutoff. First it is shown, for frequencies below the cutoff, that reflection of the mode is accompanied by a delay in phase, and that there is significant additional motion due to nonpropagating modes within about five plate thicknesses of the end. The extend of this additional motion in the vicinity of the end of the plate is demonstrated by subtracting the contribution of the propagating modes from the displacement field. The wave field at frequencies above the cutoff is more complex because the as well as the propagating modes are present at the end of the plate. Nevertheless, it has still been possible, using semi-analytical predictions and finite element simulations, to demonstrate the additional motion due to the nonpropagating modes.
Some extensions of the Gaussian beam expansion: Radiation fields of the rectangular and the elliptical transducer113(2003); http://dx.doi.org/10.1121/1.1572144View Description Hide Description
A straightforward extension of Gaussian beam expansion is presented for calculation of the Fresnel field integral [J. J. Wen and M. A. Breazeale, J. Acoust. Soc. Am. 83, 1752–1756 (1988)]. The source distribution function is expanded into the superposition of a series of two-dimensional Gaussian functions. The corresponding radiation field is expressed as the superposition of these two-dimensional Gaussian beams and is then reduced to the computation of these simple functions. This treatment overcomes the limit that the shape of source is of circular axial-symmetry. The numerical examples are presented for the field of the (uniform) elliptical and the rectangular piston transducers and agree well with the results given by complicated computation.
- NONLINEAR ACOUSTICS 
Local interaction simulation approach to modelling nonclassical, nonlinear elastic behavior in solids113(2003); http://dx.doi.org/10.1121/1.1570440View Description Hide Description
Recent studies show that a broad category of materials share “nonclassical” nonlinear elastic behavior much different from “classical” (Landau-type) nonlinearity. Manifestations of “nonclassical” nonlinearity include stress–strain hysteresis and discrete memory in quasistatic experiments, and specific dependencies of the harmonic amplitudes with respect to the drive amplitude in dynamic wave experiments, which are remarkably different from those predicted by the classical theory. These materials have in common soft “bond” elements, where the elastic nonlinearity originates, contained in hard matter (e.g., a rock sample). The bond system normally comprises a small fraction of the total material volume, and can be localized (e.g., a crack in a solid) or distributed, as in a rock. In this paper a model is presented in which the soft elements are treated as hysteretic or reversible elastic units connected in a one-dimensional lattice to elastic elements (grains), which make up the hard matrix. Calculations are performed in the framework of the local interaction simulation approach (LISA). Experimental observations are well predicted by the model, which is now ready both for basic investigations about the physical origins of nonlinear elasticity and for applications to material damage diagnostics.
113(2003); http://dx.doi.org/10.1121/1.1566974View Description Hide Description
In crystals the speed of the surface acoustic wave mode may approach that of the lowest-speed quasitransverse bulk mode in some directions of propagation. Under these circumstances, it is possible for energy to be transferred from the surface mode to the bulk mode by nonlinear coupling. In the present paper we investigate the possibilities for mode coupling in the (001), (110), and (111) planes of cubic crystals. A condition is given for determining the range of propagation directions with significant coupling, and numerical results are provided for eight different crystals with a range of anisotropy ratios. It is shown that even for significant excitation amplitudes the coupling is negligible for most propagation directions in the aforementioned surface cuts.
113(2003); http://dx.doi.org/10.1121/1.1570437View Description Hide Description
A theoretical investigation of the nonlinear interaction between an acoustic plane wave and an interface formed by two rough, nonconforming surfaces in partial contact is presented. The macroscopic elastic properties of such a nonlinear interface are derived from micromechanical models accounting for the elastic interaction that is characteristic of spherical bodies in contact. These results are used to formulate set of boundary conditions for the acoustic field, which are to be enforced at the imperfect interface. The scattering problem is solved for plane wave incidence by using a simple perturbation approach and the harmonic balance method. Sample results are presented for arbitrary wave polarization and angle of incidence. The relative magnitude of the nonlinear signals and their potential use toward the nondestructive evaluation of imperfect interfaces are assessed. In particular, attention is drawn to the enhanced nonlinear response of an interface insonified by a shear vertical wave in the neighborhood of the longitudinal critical angle. The motivation for this investigation is provided by the need to develop nondestructive methods to detect and localize small, partially closed cracks in metals with coarse microstructures.
Optimization of acoustic scattering from dual-frequency driven microbubbles at the difference frequency113(2003); http://dx.doi.org/10.1121/1.1570442View Description Hide Description
The second harmonic radiation of acoustically driven bubbles is a useful discriminant for their presence in clinical ultrasound applications. It is useful because the scatter from a bubble at a frequency different from the driving can have a contrast-to-tissue ratio better than at the drive frequency. In this work a technique is developed to optimize the scattering from a microbubble at a frequency different from the driving. This is accomplished by adjusting the relative phase and amplitudes of the components of a dual-frequency incident ultrasound wave form. The investigation is focused primarily on the example of dual-mode driving at frequencies of 1 MHz and 3 MHz, with the scattering optimized at 2 MHz. Bubble radii of primary interest are 0.5 to 2 μm and driving amplitudes to 0.5 atm. Bubbles in this size range are sensitive to modulation of driving. It is shown that an optimal forcing scheme can increase the target response eightfold or more. This suggests new applications in imaging and in bubble detection.
- AEROACOUSTICS, ATMOSPHERIC SOUND 
113(2003); http://dx.doi.org/10.1121/1.1562647View Description Hide Description
The linearized equations of viscousfluid flow are used to analyze the diffraction of a time-harmonic acoustic plane wave by a circular aperture in a rigid plane screen. Arbitrary aperture size and arbitrary angle of incidence are considered. Sets of dual integral equations are derived for the diffracted velocity and pressure fields, and are solved by analytic reduction to sets of linear algebraic equations. In the case of normal incidence, numerical results are presented for the fluid velocity in the aperture and the power absorption due to viscous dissipation. The theoretical results for power absorption are compared to previously obtained results from high amplitude acoustic experiments in air. The conditions under which the dissipation predicted by linear theory becomes significant are quantified in terms of the fluid viscosity and sound speed, the acoustic frequency, and the aperture radius.