Volume 107, Issue 4, April 2000
- acoustical news—usa
- acoustical news—international
- book reviews
- reviews of acoustical patents
- general linear acoustics 
- nonlinear acoustics 
- underwater sound 
- ultrasonics, quantum acoustics, and physical effects of sound 
- transduction 
- structural acoustics and vibration 
- architectural acoustics 
- acoustical measurements and instrumentation 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- music and musical instruments 
- bioacoustics 
- letters to the editor
Index of content:
- BOOK REVIEWS
Acoustics of Layered Media I: Plane and Quasi-plane Waves (Springer Series on Wave Phenomena Volume 5) Second, Updated Printing (softcover); Acoustics of Layered Media II: Point Sources and Bounded Beams (Springer Series on Wave Phenomena Volume 10) Second, Updated and Enlarged Edition107(2000); http://dx.doi.org/10.1121/1.428553View Description Hide Description
- REVIEWS OF ACOUSTICAL PATENTS
107(2000); http://dx.doi.org/10.1121/1.428515View 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 
107(2000); http://dx.doi.org/10.1121/1.428462View Description Hide Description
A time-dependent three-dimensional acoustic scattering problem is considered. An incoming wave packet is scattered by a bounded, simply connected obstacle with locally Lipschitz boundary. The obstacle is assumed to have a constant boundary acoustic impedance. The limit cases of acoustically soft and acoustically hard obstacles are considered. The scattered acoustic field is the solution of an exterior problem for the wave equation. A new numerical method to compute the scattered acoustic field is proposed. This numerical method obtains the time-dependent scattered field as a superposition of time-harmonic acoustic waves and computes the time-harmonic acoustic waves by a new “operator expansion method.” That is, the time-harmonic acoustic waves are solutions of an exterior boundary value problem for the Helmholtz equation. The method used to compute the time-harmonic waves improves on the method proposed by Misici, Pacelli, and Zirilli [J. Acoust. Soc. Am. 103, 106–113 (1998)] and is based on a “perturbative series” of the type of the one proposed in the operator expansion method by Milder [J. Acoust. Soc. Am. 89, 529–541 (1991)]. Computationally, the method is highly parallelizable with respect to time and space variables. Some numerical experiments on test problems obtained with a parallel implementation of the numerical method proposed are shown and discussed from the numerical and the physical point of view. The website: http://www.econ.unian.it/recchioni/w1 shows four animations relative to the numerical experiments.
107(2000); http://dx.doi.org/10.1121/1.428463View Description Hide Description
Explicit formulas are derived for waves modeled by the scalar two-dimensional Helmholtz equation for the field that is diffracted when surface creeping rays encounter an infinitely sharp edge. Both Neumann and Dirichlet boundary conditions are analyzed, and the diffracted field is found to be an order to magnitude smaller in the latter case.
107(2000); http://dx.doi.org/10.1121/1.428464View Description Hide Description
Acoustic radiation from a source located inside layered cavities is studied using the transfer matrix method. It is shown that the radiation can be either enhanced or inhibited, depending on the characteristics and the material composition of the cavities. The analysis predicts well-defined spectral peaks and nodes in some cavities. It is found that significant enhancement and inhibition are possible by varying acoustic parameters. The results also show that the strength of the radiating source can be significantly modified due to the presence of layered structures. The link to the similar phenomena in the optical cavities is discussed.
107(2000); http://dx.doi.org/10.1121/1.428465View Description Hide Description
This article presents a method to deduce the in-plane elastic properties of multilayered composite plates. Drawing on a synthetic-aperture technique developed for the elucidation of materials properties in air-coupled ultrasonics, this new method exploits the high elastic anisotropy of composite materials to permit an accurate measurement of directional in-plane stiffness. It is found that comparisons of experimental measurements with plate stiffnesses calculated on the basis of lamination theory agree to within several percent for uniaxial and biaxial laminates and to within 10 percent for quasi-isotropic laminates. It is further shown that the method is largely insensitive to transducer deployment angle within a range related to the transducer beamwidth.
Acoustic wave motion along a narrow cylindrical duct in the presence of an axial mean flow and temperature gradient107(2000); http://dx.doi.org/10.1121/1.428466View Description Hide Description
A numerical solution is presented to the problem of nonisentropic acoustic wave motion in a circular capillary tube in the presence of both axial mean flow and a background axial temperature gradient. The effects of the radial components of the acoustic velocity are included in the analysis. The main application area is in the study of the acoustic effects of catalytic converters. The solution makes use of a series expansion and is valid for small relative changes in the background temperature, which are typical of this application area. Various solutions to the problem have been obtained previously, using different simplifications to the complete problem which is considered here. It is shown that each of the simplifications results in errors for the predicted attenuation of at least 20 dB/m, using conditions typical for catalytic converters. In particular, the isentropic assumption is shown to be invalid.
107(2000); http://dx.doi.org/10.1121/1.428467View Description Hide Description
Acoustic scattering from a hybrid junction in a rectangular waveguide is studied. The Fourier transform and mode matching is used to represent the scattered wave and the simultaneous equations for the modal coefficients are formulated. A residue calculus is utilized to obtain a solution to the simultaneous equations in fast-converging series. Numerical computations are performed to show the behavior of transmission in terms of junction geometry and operating frequency. The utility of acoustic hybrid junction is discussed in terms of its decoupling characteristics.
107(2000); http://dx.doi.org/10.1121/1.428468View Description Hide Description
In this paper, a simple flow model is used in order to assess the influence of mean flow and dissipation on the acoustic performance of the classical two-duct Herschel–Quincke tube. First, a transfer matrix is obtained for the system, which depends on the values of the Mach number in the two branches. These Mach numbers are then estimated separately by means of an incompressible flow calculation. Finally, both calculations are used to study the way in which mean flow affects the position and value of the characteristic attenuation and resonances of the system. The results indicate the nontrivial character of the influence observed.
107(2000); http://dx.doi.org/10.1121/1.428469View Description Hide Description
Complex source pulsed beams (CSPB) are exact wave-packet solutions of the time-dependent wave equation that are modeled mathematically in terms of radiation from a pulsed point source located at a complex space–time coordinate. In the present paper, the physical source realization of the CSPB is explored. This is done in the framework of the acoustic field, as a concrete physical example, but a similar analysis can be applied for electromagnetic CSPB. The physical realization of the CSPB is addressed by deriving exact expressions for the acoustic source distribution in the real coordinate space that generates the CSPB, and by exploring the power and energy flux near these sources. The exact source distribution is of finite support. Special emphasis is placed on deriving simplified source functions and parametrization for the special case where the CSPB are well collimated.
Calculation of surface wave motions due to a subsurface point force: An application of elastodynamic reciprocity107(2000); http://dx.doi.org/10.1121/1.428470View Description Hide Description
The elastodynamic reciprocity theorem for two time-harmonic elastodynamic states of the same body is used to determine the surface wave motions generated by a subsurface point load of arbitrary direction in an isotropic, homogeneous, elastic half-space. The actual surface wave motions due to the point load expressed in a suitably general form represent one of the states, while the other one is an appropriately selected auxiliary solution consisting of incoming and outgoing surface waves. A direct application of the reciprocity theorem yields the desired information on the generated surface wave motion.
Wave-number-based assessment of the doubly asymptotic approximation. I. Frequency domain wet surface impedance107(2000); http://dx.doi.org/10.1121/1.428471View Description Hide Description
The doubly asymptotic approximation (DAA) is a canonical relationship for the interaction between surface normal velocity and pressure. Its validity for a slender hemicapped cylinder is examined by formulating a frequency domain version of DAA using the global basis functions employed in the wave-number-based formulation of the surface variational principle [K. Wu and J. H. Ginsberg, ASME J. Vib. Acoust. 120, 392–400 (1998)]. The wet surface impedance matrix, which relates the spectral representation of normal velocity to a corresponding representation of pressure, is obtained according to a second-order version of DAA and according to the surface variational principle. Comparison and interpretation of the results reveals that DAA fails to account for highlights associated with transition from supersonic to subsonic surface waves as the surface wavelength decreases with frequency held constant.
Wave-number-based assessment of the doubly asymptotic approximation. II. Frequency and time domain response107(2000); http://dx.doi.org/10.1121/1.428472View Description Hide Description
In part I, the surface variational principle (SVP) and the doubly asymptotic approximation (DAA) were used to generate alternative descriptions of the frequency domain wet surface impedance. These are used here to obtain alternative descriptions of the displacement field in slender hemicapped cylindrical shells. This field is represented as a decomposition into a two-dimensional wave-number space. The responses that are obtained are frequency domain transfer functions for a point force at the midplane, evaluated for a discrete set of frequencies. Solutions obtained from first- and second-order versions of DAA are compared to the SVP result. Then temporal responses are obtained by using an inverse fast Fourier transform to evaluate the convolution of the transfer functions with a prototypical temporal excitation. The results reveal that DAA and SVP differ most in the vicinity of fluid-loaded resonances. The largest disagreement is encountered for the axisymmetric portion of the response. It is shown that DAA often greatly underpredicts peak displacements and accelerations, but a few cases lead to overprediction.
- NONLINEAR ACOUSTICS 
107(2000); http://dx.doi.org/10.1121/1.428473View Description Hide Description
The results of experimental and theoretical investigations of nonlinear acoustic phenomena (nonlinear losses, shift of resonance frequency, generation of the third harmonic, and nonlinear sound-by-sound damping) in polycrystallinezinc nonannealed and annealedresonating rods are presented. The measurements were carried out in the strain range at a frequency of about 3 kHz; the frequency of the weak ultrasonic pulse was about 270 kHz. The experimentally observed phenomena are described in frames of phenomenological equations of state containing elastic hysteresis and dissipative nonlinearity. The nonlinear acoustic parameters of these equations are determined by comparison between theoretical dependencies and experimental results. The influence of structural changes in zinc due to annealing on the nonlinear acoustic phenomena is shown.
A method for estimating time-dependent acoustic cross-sections of bubbles and bubble clouds prior to the steady state107(2000); http://dx.doi.org/10.1121/1.428474View Description Hide Description
Models for the acoustic cross-sections of gas bubbles undergoing steady-state pulsation in liquid have existed for some time. This article presents a theoretical scheme for estimating the cross-sections of single bubbles, and bubble clouds, from the start of insonation onward. In this period the presence of transients can significantly alter the cross-section from the steady-state value. The model combines numerical solutions of the Herring–Keller model with appropriate damping values to calculate the extinction cross-section of a bubble as a function of time in response to a continuous harmonic sound field (it is also shown how the model can be adapted to estimate the time-dependent scatter cross-section). The model is then extended to determine the extinction cross-section area of multiple bubbles of varying population distributions assuming no bubble–bubble interactions. The results have shown that the time taken to reach steady state is dependent on the closeness of the bubble to resonance, and on the driving pressure amplitude. In the response of the population as a whole, the time to reach steady state tends to decrease with increasing values of the driving pressure amplitude; and with the increasing values of the ratio of the numbers of bubbles having radii much larger than resonance to the number of resonant bubbles. The implications of these findings for the use of acoustic pulses are explored.
- UNDERWATER SOUND 
Backscattering enhancements associated with subsonic Rayleigh waves on polymer spheres in water: Observation and modeling for acrylic spheres107(2000); http://dx.doi.org/10.1121/1.428475View Description Hide Description
Unlike most common solids, “plastic” polymer solids typically have shear and Rayleigh wave phase velocities less than the speed of sound in water. Subsonic Rayleigh waves on smooth objects in water are not classified as leakey waves and it is necessary to reexamine backscattering mechanisms. Also the intrinsic material dissipation of the Rayleigh wave can be significant. Backscattering by acrylic or polymethlmethacrylate (PMMA) spheres in water is analyzed and measured in the region and it is found that prominent low-lying resonance peaks of the form function exist. The peaks can be modeled with quantitative ray theory as the result of coupling of subsonic Rayleigh waves with sound through acoustic tunneling. The most prominent maximum of occurs at and is associated with the quadrupole (or partial wave. In addition to explaining the scattering, the target strength is found to be sufficiently large that such spheres may be useful for passive low frequency targets.
107(2000); http://dx.doi.org/10.1121/1.428476View Description Hide Description
A mapping approach for handling sloping interfaces in parabolic equationsolutions is developed and tested. At each range, the medium is rigidly translated vertically so that a sloping interface becomes horizontal. To simplify the approach, the slope is assumed to be small and the extra terms that arise in the wave equation under the mapping are neglected. The effects of these terms can be approximately accounted for by applying a leading-order correction to the phase. The mapping introduces variations in topography, which are relatively easy to handle for the case of a pressure-release boundary condition. The accuracy of the approach is demonstrated for problems involving fluid sediments. The approach should also be accurate for problems involving elastic sediments and should be useful for solving three-dimensional problems involving variable topography.