Volume 115, Issue 6, June 2004
- 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 
- noise: its effects and control 
- architectural acoustics 
- acoustical measurements and instrumentation 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- speech processing and communication systems 
- bioacoustics 
Index of content:
- BOOK REVIEWS
115(2004); http://dx.doi.org/10.1121/1.1698712View Description Hide Description
- REVIEWS OF ACOUSTICAL PATENTS
115(2004); http://dx.doi.org/10.1121/1.1748009View 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 
A uniqueness theorem for the time-domain elastic-wave scattering in inhomogeneous, anisotropic solids with relaxation115(2004); http://dx.doi.org/10.1121/1.1710876View Description Hide Description
A uniqueness theorem for the (analytic or computational) time-domain modeling of the elastic wave motion in a scattering configuration that consists of inhomogeneous, anisotropic solids with arbitrary relaxation properties, occupying a bounded subdomain in an unbounded homogeneous, isotropic, perfectly elastic embedding, is presented. No direct time-domain uniqueness proof seems to exist for this kind of configuration. As an intermediate step, the one-to-one correspondence between the causal time-domain wavefield components and the constitutive material response functions on the one hand, and their time Laplace-transform counterparts for (a sequence of) real, positive values of the transform parameter on the other hand, seems a necessary tool. It is shown that such an approach leads to simple, explicit, sufficiency conditions on the inertial loss and compliance relaxation tensors describing the solid’s constitutive behavior for uniqueness to hold. In it, the property of causality plays an essential role. In Christensen [Theory of Viscoelasticity—An Introduction (Academic, New York, 1971)] a similar approach is applied to the problem of uniqueness of the elastodynamic initial-/boundary-value problem associated with a viscoelastic object of bounded extent, the surface of which is subject to an admissible set of explicit boundary values. In the scattering configuration of unbounded extent, no explicit boundary values occur and the far-field compressional and shear wave radiation characteristics at “infinity” in the embedding play a key role in the proof.
Comparison of a finite element model with a multiple-scales solution for sound propagation in varying ducts with swirling flows115(2004); http://dx.doi.org/10.1121/1.1707084View Description Hide Description
A multiple-scales (MS) solution is proposed to study sound propagation in slowly varying ducts with mean swirling flows. Instead of the standard linearized Euler equations, the MS method is applied to the so-called Galbrun’s equation. This equation is based on an Eulerian–Lagrangian description and corresponds to a wave equation written only in terms of the Lagrangian perturbation of the displacement. This yields simpler differential equations to solve for the MS model as well as simpler boundary conditions. In this paper, Galbrun’s equation is also solved by a mixed pressure-displacement finite element method(FEM). The proposed FEM model has already been tested in authors’ previous papers. This model is quite general and is extended here to arbitrary mean flows, including compressibility and swirling flow effects. Some MS and FEM solutions are then compared in order to validate both models.
Elimination of internal resonance problem associated with acoustic scattering by three-dimensional rigid body115(2004); http://dx.doi.org/10.1121/1.1703537View Description Hide Description
In this work, a simple and stable numerical method is presented, utilizing the method of moments (MoM), to eliminate the internal resonance problem associated with acoustic scattering by three-dimensional rigid body subjected to a plane wave incidence. The numerical method is based on the potential theory and combines the single layer formulation (SLF) and the double layer formulation (DLF). The scattering body is approximated by planar triangular patches. For the MoM solution of SLF and DLF, the basis functions have been defined with respect to the edges to approximate the unknown source distribution. These basis functions along with an efficient testing proceduregenerate accurate results at all frequencies, including the characteristic frequencies. Finally, the new solution method is validated with several representative examples.
115(2004); http://dx.doi.org/10.1121/1.1736650View Description Hide Description
A complete solution is obtained for the diffraction of a time-harmonic acoustic plane wave by a circular disk in a viscous fluid. Arbitrary disk radius size and arbitrary angle of incidence are considered. The linearized equations of viscous flow and the no-slip condition on the rigid disk are used to derive sets of dual integral equations for the fluid velocity and pressure. The dual integral equations are solved by analytic reduction to sets of linear algebraic equations. An asymptotic approximation for the far-field scatteredpressure is given, and this approximation is compared to results of previous inviscid acoustic analyses. It is shown that our results for the force on the disk and the far-field scatteredpressure are consistent with the prediction of the theory of aerodynamic sound. Numerical results are presented for the fluid velocity field in the case of tangential incidence. The velocity field near the disk is shown to contain vortices that are swept along the disk with the passage of the incident plane wave.
115(2004); http://dx.doi.org/10.1121/1.1710500View Description Hide Description
This paper presents a theory to describe wave propagation in a porous medium composed of two solids saturated by a single-phase fluid for spatially variable porosity. This problem has been previously solved for constant porosity when one of the solids is ice or clay, but that model is not useful for most realistic situations. The equations for variable porosity are derived from the virtual work principle, where the generalized coordinates are identified as the displacements of the two solid phases and a new variable associated with the relative fluid flow, whose divergence is the change in fluid content. The generalized forces are the fluid pressure and combinations of the stress tensor of each solid phase and the fluid pressure. The Lagrangianequations of motion are derived for the isotropic case and a theorem on the existence and uniqueness of their solution is given. The plane wave analysis reveals the existence of three compressional and two shear waves. The theory is applied to wave propagation in shaley sandstones showing that phase velocities of the faster P and S waves agree very well with experimental data for varying porosity and clay content. A simulation through a plane interface separating two frozen sandstones of different ice contents is presented.
115(2004); http://dx.doi.org/10.1121/1.1739483View Description Hide Description
A plane-wave method for computing the three-dimensional scattering of propagating elastic waves by a planar fracture with heterogeneous fracture compliance distribution is presented. This method is based upon the spatialFourier transform of the seismic displacement-discontinuity (SDD) boundary conditions (also called linear slip interface conditions), and therefore, called the wave-number-domain SDD method (wd-SDD method). The resulting boundary conditions explicitly show the coupling between plane waves with an incident wave number component (specular component) and scattered waves which do not follow Snell’s law (nonspecular components) if the fracture is viewed as a planar boundary. For a spatially periodic fracture compliance distribution, these boundary conditions can be cast into a linear system of equations that can be solved for the amplitudes of individual wave modes and wave numbers. We demonstrate the developed technique for a simulated fracture with a stochastic (correlated) surface compliance distribution. Low- and high-frequency solutions of the method are also compared to the predictions by low-order Born series in the weak and strong scattering limit.
115(2004); http://dx.doi.org/10.1121/1.1687735View Description Hide Description
The scattering amplitude for the scattering of anti-plane shear waves by screw dislocations, and of in-plane shear and acoustic waves by edge dislocations are computed within the framework of elasticity theory. The former case reproduces well-known results obtained on the basis of an electromagnetic analogy. The latter case involves four scattering amplitudes in order to fully take into account mode conversion, and an adequately generalized optical theorem for vector waves is provided. In contrast to what happens for scattering by obstacles, the scattering amplitude increases with wavelength, and, in general, mode conversion in the forward direction does not vanish.
115(2004); http://dx.doi.org/10.1121/1.1739480View Description Hide Description
The propagation speed of shear waves is related to frequency and the complex stiffness (shear elasticity and viscosity) of the medium. A method is presented to solve for shear elasticity and viscosity of a homogeneous medium by measuring shear wave speed dispersion. Harmonic radiation force, introduced by modulating the energy density of incident ultrasound, is used to generate cylindrical shear waves of various frequencies in a homogeneous medium. The speed of shear waves is measured from phase shift detected over the distance propagated. Measurements of shear wave speed at multiple frequencies are fit with the theoretical model to solve for the complex stiffness of the medium. Experiments in gelatin phantoms show promising results validated by an independent method. Practical considerations and challenges in possible medical applications are discussed.
A two-field hybrid formulation for multilayers involving poroelastic, acoustic, and elastic materials115(2004); http://dx.doi.org/10.1121/1.1698758View Description Hide Description
Recently, an implementation of the mixed pressure displacement formulation for poroelastic materials using the theory of hierarchical elements has been proposed. It has been shown that poroelastic hierarchical elements allow for an important reduction of the number of degrees of freedom required for the modeling of a porous material in three dimensions, compared to linear finite elements. In this paper, the coupling of a porous material modeled with hierarchical elements and an elastic domain modeled with finite elements or a fluid modeled with hierarchical elements is presented. Non-coincident meshes are assumed. Continuity of the fields is ensured by using a two-field hybrid formulation. The paper is organized as follows. The theory is first presented. The computation of fluid-structure coupling integrals over non-coincident meshes is then tackled. Numerical results are produced to show the accuracy and the performance of the proposed model for the modeling of an elastic-porous or a porous-fluid coupled system. Comparisons between numerical simulations and experiments are also presented in the case of a porous coated plate.
- NONLINEAR ACOUSTICS 
115(2004); http://dx.doi.org/10.1121/1.1738837View Description Hide Description
Nonlinear Rayleigh waves propagating in a substrate coated with a thin elastic film are studied numerically. The evolution model consists of the nonlinear spectral equations of Zabolotskaya [J. Acoust. Soc. Am. 91, 2569–2575 (1992)] augmented ad hoc to include film dispersion. The dispersion relation is obtained from linear theory but is otherwise exact. Both loading and stiffening films are considered. Computations are performed for nonlinear evolution of an initially sinusoidal Rayleigh wave under three distinct dispersion regimes corresponding to different film thicknesses. The validity of the evolution model is also examined.
- UNDERWATER SOUND 
115(2004); http://dx.doi.org/10.1121/1.1703539View Description Hide Description
The automatic spatial and temporal focusing properties of a time-reversing array (TRA) make it an attractive technology for active and passive sonar systems that may be deployed in unknown multipath environments. However, in these and other potential underwater applications of TRAs, either the source, the array, or both are likely to be moving. In this paper we present broadband-signal TRA performance predictions that include the influence of the Doppler effect on the time-reversal process for broadband signals transmitted from an arbitrarily moving source to a stationary vertical TRA through a shallow ocean environment. Here, the impact of source motion on TRA performance is predicted from analysis and numerical simulations using a formulation of the Doppler shifted field based on Fourier superposition of stationary but spatially distributed time-harmonic sources. Quantitative results for the size and location of the TRA’s retrofocus are presented as well as the correlation of the TRA retrofocus signal with the time-reversed original signal for various source motions in range-independent and range-dependent shallow water sound channels. Overall, source motion is predicted to have little effect on TRA operations with source speeds less than 20 m/s for signals having a center frequency of 500 Hz at source–array ranges of a few kilometers.
115(2004); http://dx.doi.org/10.1121/1.1707085View Description Hide Description
Measurements of bottom scattering strengths were made with a multi-frequency echo sounder mounted on a tower on a sandy bottom off West Destin, FL. Data were measured at five frequencies in the range 265–1850 kHz, at subcritical grazing angles ranging from to and at azimuths up to around the tower. Scattering strength increased at about up to peaked between 700 and 1100 kHz, and decreased at higher frequencies.
The derivative of a waveguide acoustic field with respect to a three-dimensional sound speed perturbation115(2004); http://dx.doi.org/10.1121/1.1736651View Description Hide Description
Semianalytic expressions are derived for the first-order derivative of a pressure field in a laterally homogeneous waveguide, with respect to an arbitrary three-dimensional refractive index perturbation in either the water column or ocean bottom. These expressions for the “environmental derivative,” derived using an adjoint method, require a three-dimensional spatial correlation between two Green’s functions, weighted by an environmental parameter basis function, with the Green’s functions expressed in terms of normal modes. When a particular set of orthogonal spatial basis functions is chosen, the three-dimensional spatial integral can be converted into a set of one-dimensional integrations over depth and azimuth. The use of the orthogonal basis permits environmental derivatives to be computed for an arbitrary sound-speed perturbation. To illustrate the formulas, a simple sensitivity study is presented that explores under what circumstances three-dimensional plane-wave and cylindrical perturbations produce non-negligible horizontal refraction effects, for a fixed source/receiver geometry. Other potential applications of these formulas include benchmarking three-dimensional propagation codes, and computing Cramer–Rao bounds for three-dimensional environmental parameter estimates, including internal wave components.
115(2004); http://dx.doi.org/10.1121/1.1643368View Description Hide Description
Humpback whale songs were recorded on six widely spaced receivers of the Pacific Missile Range Facility (PMRF) hydrophone network near Hawaii during March of 2001. These recordings were used to test a new approach to localizing the whales that exploits the time-difference of arrival (time lag) of their calls as measured between receiver pairs in the PMRF network. The usual technique for estimating source position uses the intersection of hyperbolic curves of constant time lag, but a drawback of this approach is its assumption of a constant wave speed and straight-line propagation to associate acoustic travel time with range. In contrast to hyperbolic fixing, the algorithm described here uses an acoustic propagationmodel to account for waveguide and multipath effects when estimating travel time from hypothesized source positions. A comparison between predicted and measured time lags forms an ambiguity surface, or visual representation of the most probable whale position in a horizontal plane around the array. This is an important benefit because it allows for automated peak extraction to provide a location estimate. Examples of whale localizations using real and simulated data in algorithms of increasing complexity are provided.
115(2004); http://dx.doi.org/10.1121/1.1710502View Description Hide Description
Active acoustic time reversal is a technique for focusing sounds recorded in complex unknown environments back to their remote point(s) of origin. It can be accomplished with a transducer array—a time-reversing array (TRA)—that sends and receives sound. Nearly all prior work on TRA performance has involved stationary arrays. This letter describes how random array deformation influences TRA retrofocusing in shallow ocean environments. For harmonic signals, randomly drifting array elements degrade TRA performance by ∼20% when the average horizontal wavenumber times the root-mean-square horizontal element displacement approaches 0.5. TRA focusing should be less sensitive to vertical element drift.
115(2004); http://dx.doi.org/10.1121/1.1710504View Description Hide Description
A large-aperture, seabed mounted, fiber-optic hydrophone array has been constructed and characterized. The system is designed for use as a large area surveillance array for deployment in shallow water regions. The underwater portion comprises two arrays of 48 hydrophones separated by a 3 km fiber-optic link, which are connected to a shore station by 40 km of single-mode optical fiber. The hydrophone is based on a fiber-optic Michelson interferometer and the acoustic transduction mechanism is a fiber-wrapped mandrel design. No electrical power is required in the underwater portion. The performance of the system is described, characterized during laboratory measurements and during a recent sea trial. Specifically, measurements of the acoustic resolution, array shape, beam patterns, array gain, and target tracking capability of this array. The system demonstrates self-noise levels up to 20 dB (typically 10 dB) lower than the ambient acoustic noise experienced in the sea trial and array gains close to the theoretical maximum. The systemtelemetry and electronics have been designed to be expandable to accommodate several hundred hydrophones.