bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibro-acoustic effects of a soft compliant layer on submerged finite cylindrical shells
Authors: Herdic Peter C. , Houston Brian H. , Photiadis Douglas M. , Williams Earl G.
Published: July 2002

The structural acoustics associated with a compliant material applied to the outer surface of a framed fluid-loaded cylinder is examined. Spatially dense laser Doppler vibrometer (LDV) and near field acoustic holography (NAH) measurements are employed to capture the detailed response under radial point force excitation. In the mid- and high-frequency regimes, the soft, low impedance layer is associated with significant reduction in the normal velocity at all wavenumbers. Essentially, there is very little motion of the outer compliant layer due to the impedance mismatch with the fluid. Further, these data indicate that Bloch wave components are modified somewhat due to reduced fluid-loading effects. However, at low frequencies the normal velocities at the fluid interface are greatly accentuated due to simple resonances associated with the impedance of the acoustic medium, the soft spring-like compliant layer, and the structure. Although these resonances are typically characterized as subsonic, enhanced levels are observed in the farfield. Also, it is found experimentally that the input drive impedance changes with the addition of the compliant layer, thus, modifying the energy delivered to the system by the shaker. The data will be reported along with simple impedance models that illustrate the physics of the behavior.
Generator of fluid reactances and resistances for blades vibrating at high frequencies
Authors: Martinez R. , Martini K.
Published: July 2002

Blades and two-sided bladelike objects vibrating at high frequencies experience a spatial distribution of radiation loading with the following two features: (1) away from the edges: a primarily resistive recoil pressure, oscillating about a 2ρc mean (that mean being the familiar ‘‘1-D’’ solution); and (2) near and at the edges: a complicated mixture of resistive and reactive fields that account for diffraction effects. This paper discusses a novel analytical/numerical tool for predicting (1) and (2) inexpensively and in a unified manner. The theory achieves that by considering an unconventional product of Fresnel functions, each representing an edge. It succeeds in generating a distribution of finite-fluid impedances even for sonic patterns of vibration, i.e., even for prescribed wave numbers at ‘‘coincidence,’’ for which an additive correction scheme using the same Fresnel integrals would fail. The new computational tool is unexpectedly accurate all the way down to the acoustically compact range, failing to recover by only 27% the well-known entrained mass of a rigidly vibrating strip at low frequencies. The presentation will close with a brief discussion of how the presence of a mean flow affects the above conclusions. [Work supported by NSWC/CD’s 6.2 program.]
The data are what the data are: Top-down processing in spoken word recognition is necessary
Authors: Samuel Arthur G.
Published: July 2002

For the last two decades there has been an ongoing debate about the architecture of the word recognition process: Is this process accomplished in a strictly autonomous, bottom-up fashion, or does information at higher levels affect the perception of lower-level representations? I will review results from a number of experimental settings that support the necessity of positing top-down, lexical-to-phonemic effects. I will argue that models that are presented as strictly autonomous must therefore either be at odds with the data, or must not in fact be fully autonomous. The literature indicates that perception of spoken words is (naturally) based primarily on the perceptual input, but that lexical knowledge also plays a significant role: Top-down processing is a necessary component of an accurate model.
Broadband super-resolution in a reverberant environment using ‘‘pairwise’’ correlations
Authors: Olivieri Marc P.
Published: July 2002

In recent years, the underwater acoustic community has been focusing its attention on the problem of shallow water as a harsh acoustic environment, since traditional narrow-band systems have failed to achieve their expected deep-water performance. At present, new broadband techniques are sought to solve this problem. In previous work, the Ambient Noise Sonar [M. P. Olivieri and S. A. L. Glegg, J. Acoust. Soc. Am. 99, 2454 (1996)] was developed to locate broadband sources in shallow water. In the case of multipaths or correlated sources, this broadband ‘‘pairwise’’ cross-correlation technique introduces ambiguities. To resolve them, a set of adaptive and eigenvector beamformers is proposed for broadband coherent processing. Because the method is based on pairwise correlations, it trades off degrees of freedom in space (case of an equi-space line array) for degrees of freedom in frequency (bandwidth). Adaptive beamformers for the cross-frequency covariance matrix are derived using ‘‘frequency smoothing’’ analogous to ‘‘spatial smoothing,’’ and super-resolution is achieved in the case of multiple correlated sources and low signal-to-noise ratios. Results from simulations and measured data will be presented, and the sensitivity of the adaptive beamformers with respect to the bandwidth will be discussed.
Great halls: Great renovations. Renovation of Europe’s two most famous concert halls—the Grosser Musikvereinssaal in Vienna and the Concertgebouw in Amsterdam
Authors: Clements Pamela
Published: July 2002

It is not widely known that Europe’s two leading concert halls were renovated in the past, renovation that perhaps significantly affected the acoustical quality of the spaces. In 1911 the Grosser Musikvereinssaal underwent major renovation to improve fire safety. The hall was almost gutted, the ceiling and stage rebuilt, the light fixtures on the balcony rails were removed, and the caryatids and entablature supporing the balcony were relocated from the front of the parterre to the side walls. At the Concertgebouw the seating was changed (again for fire safety), and in 1899 the stage was rebuilt to reduce the height of the very steep orchestral risers. This was done to improve the sound quality and playing conditions for the orchestra. In the case of the Musikverein, this author has found little contemporary comment on what may have been remarkably changed acoustical conditions. In the case of the Concertgebouw, the renovation was hailed as a great improvement—yet this stage is still much steeper than would be recommended by most acousticians today. This paper is based on plans, photographs, and other historical evidence about the acoustic conditions in the two halls before and after the renovations.
Flow-controlled acoustic propagation channels on continental shelves
Authors: Orr Marshall H. , Mignerey Peter C.
Published: July 2002

Continental shelves have steep changes in bathymetric gradients. These gradients are caused by a wide variety of geological processes and are often associated with the shelf/slope break, canyons, and banks created during pauses in transgressive/regressive sea-level cycles. Tidal flow over these bathymetric features causes temporal variability in the local sound-speed field. The temporal variability is repeatable over successive semidiurnal tidal cycles. The flow ranges from subcritical to supercritical. The variability in the flow over gradients in the bathymetry can result in the formation of a stratified sound channel, perturbation of the channel by linear and noninternal waves, flow stagnation with separation, and hydraulic jumps that can have associated mixing events. Each of these flow types will cause unique sound-speed fields that can impact the properties of an acoustic signal propagating through the region. Calculations that show the relative importance of some flow types on the temporal variability of the acoustic signals that have propagated through a flow-controlled channel are presented. [Work supported by the Office of Naval Research.]
Azimuthally dependent transmission loss and horizontal coherence in the presence of shelf internal waves
Authors: Oba Roger M. , Finette Steven
Published: July 2002

A three-dimensional acoustic model, FOR3D, is used to propagate an acoustic field from a continuous wave point source to a horizontal array of receivers. The space–time variability of the continental shelf environment is modeled by shallow water of constant depth containing two types of internal waves: a spatially diffuse, randomly isotropic field, and a deterministically propagated, transversely invariant solitary wave packet. The internal wave packets cause azimuthal and range dependence in the properties of the acoustic signal as a function of (a) the bearing from the source, as referenced to the wave packet’s propagation vector, and (b) the location of the packet in the propagation path. The simulations also demonstrate a degree of out-of-plane scattering. Ensemble averaging is used to simulate horizontal coherence in environments containing combinations of the internal waves, and to illustrate the comparative importance of the diffuse and wave packet contributions. The cases studied here at selected frequencies between 100 and 400 Hz suggest that the performance of horizontal array receivers may require full three-dimensional modeling of propagation and media. [Work supported by the Office of Naval Research.]
Results from a simulation study of mode coupling due to acoustic wave-soliton interactions
Authors: Chin-Bing Stanley A. , King David B. , Warn-Varnas Alex , Zingarelli Robert A. , Murphy Joseph E.
Published: July 2002

There is a strong interest in understanding the interactions between ocean acoustic waves and shallow water solitons. Central to these interactions are the acoustic mode conversions caused by the solitons. Such mode conversions potentially occur each time the acoustic wave and soliton interact; however, at certain combinations of acoustic-oceanographic wavelengths, the interactions can produce large losses in acoustic signal. Mode coupling results will be discussed from simulation studies that examined the signal loss due to interactions with solitons in the Strait of Messina. Coupled mode formulations were avoided so that interpretations of results were not dependent upon any particular mode coupling scheme. Rather, the full-wave, two-way, finite-element model, FFRAME, was used to produce numerically accurate predictions of the complex pressure field as it passed through the soliton. This complex field was then decomposed into its component wave numbers via an FFT to determine the mode structure. This simulation included the entire acoustic field (forward propagation, backscatter, multiple scatter, etc.). The results were realistic and difficult to interpret. Results will be shown at various points along the way as the acoustic wave passed thorugh the soliton. [Work supported by ONR/NRL and by a High Performance Computing DoD grant.]
Low-frequency acoustic resonances in the bubble plume formed by a plunging water jet
Authors: Berger Thomas K. , Hahn Thomas R. , Buckingham Michael J.
Published: July 2002

As a jet of water penetrates a free water surface, air is entrained in the form of bubbles which produce sound by various mechanisms, including both individual and collective oscillations. The low-frequency acoustic emissions of the bubble clouds entrained and dispersed by vertical continuous and transient fresh water jets impinging from varying heights into a fresh water receiving pool in a large laboratory tank were studied both theoretically and experimentally for jet velocities ranging to about 10 m/s, and jet diameters of millimeter order. The acoustic signals were measured with hydrophones in different positions, amplified, and digitally sampled. The measured power spectra revealed well-defined, nonuniformly spaced resonance peaks at frequencies below about 1 kHz. A theory based on a conical bubble plume, with a nonuniform sound speed profile, acting as a resonant cavity predicts the frequencies of the resonance peaks and shows remarkable agreement with the experimentally measured values. Further, time-frequency analysis gives bubble size distributions and shows the driving source for the resonant cavity to be large secondary bubbles formed through coalescence, which become acoustically active through deformation or break-up as they are re-entrained by the downstream flow in a failed attempt to rise to the surface.
Acoustic monitoring of generation and evolution of shallow-water solitary internal waves
Authors: Turgut Altan , Wolf Stephen , Orr Marshall , Badiey Mohsen
Published: July 2002

The feasibility of acoustic monitoring of generation and evolution of shallow-water solitary internal waves is investigated by using the acoustic and environmental data collected during the 1995 Shallow Water Acoustics in a Random Medium (SWARM) experiment. Spatial and temporal variability of acoustic signals (60 to 450 Hz) were measured by using two well-populated vertical receiving arrays at 30- and 40-km ranges from two moored sources and at 20-km cross-range from two ship-deployed sources. Environmental data were collected by using CTDs, thermistor strings, a high-frequency acoustic backscattering imaging system, and a chirp sonar system. Correlation between cross-range propagation and oceanographic measurements during the generation and evolution of a solitary internal wave packet indicates the possibility of acoustic monitoring of this oceanographic process. Results of a parametric study using broadband numerical simulations are also presented to develop the best monitoring strategies for future experiments. [Work supported by ONR.]
A hybrid FEA/SEA technique for the analysis of complex systems: Application to plate and beam structures
Authors: Langley Robin S. , Smith Jeremy R. D. , Bremner Paul G.
Published: July 2002

The authors have previously developed a method for the low- to high-frequency vibration analysis of complex systems which is based on wave number partitioning. The long wavelength deformation of the system is modeled by using the finite element method (FEA), while the short wavelength deformation is modeled by using statistical energy analysis (SEA). The coarse mesh FEA model which is used to capture the long wavelength deformation of the system is enhanced by the addition of ‘‘fuzzy’’ mass and damping terms; this compensates for the ‘‘missing’’ short wavelength dynamics. The response yielded by the FEA model is then used in conjunction with SEA to give the short wavelength response. The method is noniterative, and it has previously been shown to produce good results for structures constructed from rod and beam elements. In this paper the method is extended to two-dimensional structural components such as plates. The method is applied to an example beam/plate assembly, and a comparison is made with the results yielded by SEA alone, and by a very detailed FEA model. The present approach is found to give significant improvements over SEA, while being very efficient compared to the detailed FEA model.
Current tomography in very shallow water
Authors: Badiey M.
Published: July 2002

Shallow and estuarine environments share a common acoustical property in that multi-path arrival structure of a pulse propagating through these regions generally occurs. For very shallow water depths, the direct-path becomes scattered path in a short range between the source and the receiver. The received acoustic signal becomes a superposition of many arrivals following all the possible acoustic paths between source and receiver. Most of these paths interact with sea surface and sea bottom several times. The impact of tidal currents and the changes in temperature and salinity profiles are most easily observed by focusing on the direct-path component of the received signal. Because the direct-path is not easily obtained in these regions of interest, the question of how and to what extent one can use the latter arrivals for current inversion is legitimately addressable. In this paper, we show the results in the application of current tomography in water depths of approximately 15 m. Also, the possibility of obtaining oceanographic parameters such as surface roughness by using broadband reciprocal transmission of a local source and receiver as well as a far source–receiver configuration is discussed.
Modeling and control issues concerning smart materials
Authors: Smith Ralph C.
Published: July 2002

Modeling and control issues concerning certain smart material actuators utilized in nonlinear regimes will be presented. Piezoceramic, electrostrictive, and magnetostrictive materials all exhibit various degrees of hysteresis and nonlinear dynamics at high-drive levels. The accurate and efficient quantification of these effects and their incorporation in control design are necessary to attain the full capabilities of the materials. The models described here are based on the quantification of domain effects inherent to ferroelectric and ferromagnetic materials. These models require a small number of parameters and are robust with respect to a variety of operating conditions. Hence, they are amenable to control design. Linear control methods prove ineffective at high-drive levels and certain nonlinear control laws and inverse compensation techniques for smart material applications will be discussed.
Computationally efficient modeling of structural inhomogeneities by analytical/numerical matching
Authors: Bliss Donald B. , Loftman Rickard C. , Park Christopher D. , Franzoni Linda P.
Published: July 2002

Solving structural acoustic problems in the mid-frequency range is a challenging task. Computation is expensive due to both the large well-coupled nature of the domain and resolution constraints such as small flexural wavelength. In addition, discrete structural elements such as ribs and stiffeners cause localized high-resolution content that requires much greater resolution than would be otherwise warranted. A method called analytical/numerical matching (ANM) alleviates this additional computational burden. The ANM method captures the particular influence of the inhomogeneity on the structure in an analytically expressed local solution. The governing equation is then used to show that the extraction of this local solution by superposition amounts to replacing the original discrete influence of the inhomogeneity by a smoothed forcing derived from the local solution. The result is a smoother problem that can be computed more efficiently and without the loss of any information. The method has been demonstrated for several configurations of increasing complexity in the process of its development as a useful tool for efficiently solving realistic problems of engineering interest. These problems have shown the usefulness, accuracy, and efficiency of the method. Examples will be presented, including recent work on implementation within a finite element analysis.
The mid-frequency range finite element (MFR-FE) method: MATLAB implementation and results
Authors: Sparrow Victor W.
Published: July 2002

The mid-frequency range finite element (MFR-FE) method was developed by Christian Soize in the early 1980s, and it is well described in Soize’s book with Roger Ohayon [Structural Acoustics and Vibration, (Academic, New York, 1998), Chap. 7]. The method combines finite element equations and the frequency translation property of the Fourier transform to solve acoustics and vibration problems in the mid-frequency range, at frequencies higher than possible with conventional finite element codes. In an effort to understand the method fully, an implementation of MFR-FE was developed in MATLAB [Mathworks Inc., Natick, MA], a natural environment for prototyping algorithms involving matrices and signal processing. The FE formulation was built upon one already prepared by Kwon and Bang [The Finite Element Method Using MATLAB, (CRC, Boco Raton, FL, 1997)], and initial results were recently described [Paper AIAA–99-1855, 5th AIAA/CEAS Aeroacoustics Conference]. The present talk will provide an overview of MFR-FEs and give example results, extending those previously shown. One advantage of the method is that it can be used with other improvements in FE technology, such as hp adaptive formulations. [Work sponsored by NASA Langley Research Center Structural Acoustics Branch.]
Acoustic Bessel bullets: Where did they come from and where are they going
Authors: Stepanishen Peter
Published: July 2002

Acoustic Bessel bullets (BB’s) are a new class of band-limited transient localized waves. A brief review of the development of acoustic BB’s using space–time methods is first presented where the roots are traced back to the well-known plane-wave solution of the 1-D wave equation. Although ideal three-dimensional acoustic BB’s which maintain their spatially dependent shape and time history as they propagate in free space can be generated from an infinite planar aperture, edge diffraction effects play an important role in determining the space–time characteristics of the acoustic BB’s generated by a finite planar aperture. A generalized modal impulse response approach is proposed to investigate the characteristics of acoustic BB’s and other localized wave fields generated from finite planar apertures with radially symmetric space–time source distributions. Numerical results are presented to illustrate the general space–time characteristics of the modal decomposition of the source distributions, the generalized impulse responses, and the associated acoustic BB fields. These results will illustrate the trade-offs between the radial extent of the acoustic BB’s and the near-to-far-field transition. Several interesting characteristics of the far field will also be discussed.
Limited diffraction beams and their applications on signal processing
Authors: Lu Jian-yu
Published: July 2002

Limited diffraction beams such as Bessel beams and X waves have been studied recently. These beams have many potential applications in medical imaging, tissue identification, blood flow velocity vector estimation, nondestructive evaluation of industrial materials, optical communications, and other physics related areas such as electromagnetics and optics. In this talk, fundamentals of limited diffraction beams will be presented. Results of applications of X wave theory on high-frame rate medical imaging will be shown. Applications of these beams in other areas, especially, in signal processing will be discussed. [This work was supported in part by grant HL 60301 from the National Institutes of Health.]
Broadband processing using localized waves in a shallow ocean environment
Authors: Chambers David H. , Candy James V. , Lewis D. Kent
Published: July 2002

In this paper the MPS localized wave pulse is used as the basis for designing a broadband signal processor to discriminate between two point sources. The nonseparable nature of the MPS pulse requires a ‘‘best fit’’ approach to processor design. This approach illustrates the kinds of problems one would encounter when using localized waves in a processor. The processor design is described, then applied to simulated acoustic signals generated in a shallow ocean environment. The results show that the MPS-based processor can discriminate between the two sources at least as well as a more conventional broadband beamformer. No attempt is made to estimate the positions of the sources. [This work was performed under the auspices of the Department of Energy by the Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.]
Acoustical helicoidal wave transducers with applications for the alignment of ultrasonic and underwater systems
Authors: Hefner Brian T. , Marston Philip L.
Published: July 2002

A simple four-panel transducer capable of producing a beam with a screw-dislocation along its axis was constructed and evaluated. A screw-dislocation in a wave front is characterized by a phase dependence about the dislocation axis that varies as exp(−imφ), where m is an integer and φ is the angle about the axis. At the axis the phase is indeterminate and as a result there is a corresponding null in the pressure magnitude. To generate a wave front with these characteristics, a four-panel 3-1 composite piezoelectric transducer was driven with the appropriate phasing of the panels to create dislocation along the beam axis. As a result the beam does not possess cylindrical symmetry, however, the dislocation is found to exist in both the far and near fields of the transducer. This null then clearly indicates the axis of the beam at all distances and has the potential to be used as an aid in the alignment of objects in sonar experiments or other similar applications. A related transducer was summarized previously [J. Acoust. Soc. Am. 103, 2971 (1998)] and is also discussed here for the purposes of comparison. [Work supported by the Office of Naval Research.]
Source localization in a stochastic ocean using data from the Santa Barbara Channel experiment
Authors: Daly Peter , Baggeroer Arthur
Published: July 2002

Source localization performance using matched field processing is degraded when: (1) incorrect environmental information is used in replica generation; and (2) the propagation model fails to correctly predict energy transfer from one spatially derived eigenvalue to another. Krolik [J. Acoust. Soc. Am. 92] addressed (1) by developing a robust adaptive matched field processor assuming a stochastic propagation medium and a perturbed sound speed profile. Czenszak [J. Acoust. Soc. Am. 101] extended Krolik’s work to include multiple narrow-band frequencies. We approach both (1) and (2) by direct decomposition of the simulated pressure field based on environmental perturbations. This yields information on energy distribution from a single point source on spatially derived eigenvalues in a simulated environment. We will explore the application of both processors and extensions of them to range-dependent shallow water acoustic data taken from the 1998 Santa Barbara Channel experiment. Source localization performance of the stochastic ocean beamformer is contrasted with both Bartlett and White Noise Constrained processors at ranges to 15 km, with emphasis on performance metrics in the face of uncertain environmental knowledge.
Matched-field processing of two multi-dimensional arrays
Authors: Perkins John S. , Nicholas Michael , Lingevitch Joseph F. , Orris Gregory J. , Heard Garry J.
Published: July 2002

Source location and tracking results using matched-field processing are presented for two multi-dimensional arrays. One array was L-shaped with the horizontal leg lying on the bottom. The vertical leg consisted of 32 elements with 2.5-m spacing and the horizontal leg consisted of 32 elements with 5.0-m spacing. The array was deployed in 100-m-deep water near the shelf break southeast of Halifax, Nova Scotia. The second array consisted of five vertical legs (each with 30 elements at 5.7-m spacing) arranged in a pentagon, 136-m on each side. This array was located in 200-m-deep water in the Santa Barbara Channel. For the L-shaped array, the individual legs produced results that were markedly different but extremely complimentary. As a result, their incoherent average often out-performed the fully coherent processing of the entire (64-element) array: the peak locating the source was narrower and the sidelobes were suppressed. This was not the case for the pentagonal array. The ambiguity surfaces from the individual legs were similar so that incoherent averaging broadened the source peak and did not suppress the sidelobes. Processing the entire array coherently produced excellent results. [Work supported by the Office of Naval Research.]
Wave number sampling at short range
Authors: Collins Michael D.
Published: July 2002

The self-starter is an efficient approach for solving geoacoustic inverse problems involving a vertical array of receivers located on the order of ten wavelengths from a source [R. J. Cederberg and M. D. Collins, J. Acoust. Soc. Am. 22, 102–109 (1997)]. With this approach, accurate solutions can be obtained by sampling the wave number spectrum at approximately ten points. There have been unsubstantiated claims that the spectral solution provides similar efficiency when implemented with an approach that involves perturbing the integration contour off the real line [F. B. Jensen et al., Computational Ocean Acoustics (American Institute of Physics, New York, 1994), pp. 231–240]. It is demonstrated that this quadrature scheme breaks down at short ranges and that the self-starter solution is about an order of magnitude faster. These conclusions are based on comparisons of the rational approximations associated with the self-starter and the quadrature scheme, comparisons of acoustic fields for particular problems, and a simple analysis of the spectral integral. These conclusions are not surprising since the rational approximation associated with the self-starter is based on the analytic evaluation of the spectral integral while the other rational approximation is based on numerical integration. [Work supported by ONR.]
Vortical and acoustical mode coupling inside a two-dimensional cavity with transpiring walls
Authors: Majdalani Joseph
Published: July 2002

In a long, low aspect ratio, two-dimensional cavity, where gaseous motion is permitted along transpiring walls, a time-dependent field is established when low amplitude, sinusoidal pressure oscillations with nonzero mean are introduced. An accurate solution is extracted here for the time-dependent field by way of small parameter perturbations. Contingent upon small pressure-wave amplitudes, Navier–Stokes equations are linearized to the order of the mean flow Mach number to furnish interaction equations governing the unsteady field. The latter is decomposed into acoustic and solenoidal fields coupled through Dirichlet-type boundary conditions. Solving for the solenoidal field from the momentum equation employs separation of variables and multiple scale expansions based on a careful choice of an inner scale. In fact, the unique inner scale used in the two-variable derivative expansion method is original in the sense that it stems from an unconventional, nonlinear variable transformation. A uniformly valid solution is formulated subsequently for the temporal field. This explicit solution discloses the character of the acoustic boundary layer evolving from damped traveling waves. The rate of decay is found to depend on a viscosity parameter, revealing that deeper penetration of rotational waves is possible at low viscosity. Characterization of the boundary layer region is covered in addition to a standard error analysis. In closing, results are verified through comparisons to accurate numerical predictions.
Acquisition of a tactile-alone vocabulary by normally hearing users of the Tickle Talker™
Authors: Galvin Karyn L. , Blamey Peter J. , Oerlemans Michael , Cowan Robert S. C. , Clark Graeme M.
Published: July 2002

Tactile-alone word recognition training was provided to six normally hearing users of the Tickle Talker™, an electrotactile speech perception device. A mean group tactile-alone vocabulary of 31 words was learned in 12 h of training. These results were comparable to, or superior to, those reported for other tactile devices and Tadoma. With increased training the group became faster at learning tactually new words, which were introduced in small training sets. However, as their tactile-alone vocabulary grew, subjects required more training time to reach the pass criterion when evaluated on their recognition of their whole vocabulary list. A maximum possible vocabulary size was not established. The application of tactile-alone training with hearing-impaired users of the device is discussed.
Realistic, acoustic telephone evaluation using a HATS (Head and Torso Simulator) based telephone test head
Authors: Matthisson Andre , Jonsson Soren
Published: July 2002

A substantial variety of test heads/simulators for testing the electroacoustic characteristics of telephone terminals exist today. They all intend to replicate essential features of typical human test crews, however, with varying fidelity. Traditionally, standardized measurements are performed using a table top test head (LRGP test head). In this paper we shall present a more anatomically representative ‘‘test head’’ using a head and torso simulator combined with a telephone handset holding device. Using this setup, more realistic measurements can be obtained, still complying with the geometries of the traditional table top test heads.
Elucidation of the relationship between complex acoustic power and radiation efficiency for vibrating bodies
Authors: Chen Pei-Tai
Published: July 2002

This investigation examines the physical meaning of surface complex acoustic power and its relationship to acoustic radiation efficiency. It is shown that the radiated power is the power radiating out of a far-field surface where the plane wave relationship between pressure and particle velocity holds. Meanwhile, the reactive power pertains to the difference between kinetic energy and potential energy. A stationary condition of the ratio between the radiated power to the reactive power yields an eigenvalue problem, subsequently decomposing the surface acoustics into a modal representation. Doing so further allows the examination of the relationship between acoustic radiation efficiency and power factor of the complex power. According to the results, the radiation efficiency of the first radiation mode is nearly equal to the square of the first modal power factor. The modes beyond the first of the modal radiation efficiencies are relatively larger than the corresponding squared modal power factors. Numerical examples of elastic structures subjected to external forces illustrate the relationship between radiation efficiencies and power factors of complex powers.
Wave-number sampling at short range
Authors: Collins Michael D.
Published: July 2002

Spectral solutions can be obtained efficiently at long ranges by using a quadrature scheme that involves perturbing the integration contour off the real line [F. B. Jensen et al., Computational Ocean Acoustics (American Institute of Physics, New York, 1994), pp. 231–240]. The efficiency of this implementation of the spectral solution is investigated for short-range problems. Examples are presented to illustrate that the self-starter [J. Acoust. Soc. Am. 92, 2069–2074 (1992)] is about ten times faster at ranges on the order of ten wavelengths. The accuracy of the spectral solution and the self-starter are directly related to the accuracy of rational approximations. The rational function associated with the spectral solution is based on the numerical evaluation of the spectral integral. The rational function associated with the self-starter is based on the analytic evaluation of the spectral integral. The relationship between these approaches is analogous to the relationship between the finite-difference and split-step Padé [J. Acoust. Soc. Am. 93, 1736–1742 (1993)] solutions of the parabolic equation.
Comments on “Ultrasonic interferences in polymer plates” [J. Acoust. Soc. Am. 104, 1232–1241 (1998)]
Authors: Ainslie Michael A.
Published: July 2002

General formulas for reflection and transmission coefficients are quoted for a plane wave incident on a solid plate. The result used in the subject article is derived as a special case of the general solution.
Introduction to the NSANE experiment
Authors: Green Dale
Published: July 2002

The NearShore Acoustic Network Experiment (NSANE) surf zone characterization experiment recently conducted on behalf of ONR at the Scripps pier in San Diego was a major logistical enterprise, as well as a challenging scientific and engineering exercise. The goal of the experiment was to ascertain the feasibility of acoustic communications and navigation in this adverse environment. Test equipment was provided by a consortium of organizations, all of which required coordinated installation over a full week, occasionally under rather adverse conditions. As a prelude to several other presentations on technical and scientific results, a video recording of much of the installation and demobilization will be shown highlighting the NSANE nature of the experiment.
Bubble distributions and high-frequency propagation in the surf zone
Authors: Farmer David M. , Vagle Svein
Published: July 2002

The masking and scattering effects of dense bubble populations are a distinguishing feature of high-frequency acoustic propagation in the surf zone. The high-quality factor of bubbles at resonance ensures that at higher frequencies bubble size distribution is a crucial factor determining propagation characteristics. In May 1999 a collaborative study near Scripps Pier led to the simultaneous acquisition of bubble size distributions within the surf, together with acoustic back and forward scatter at frequencies of 12 and 100 kHz. Vertical sonars were also used to monitor the development of bubble clouds beneath breaking waves, while horizontal imaging and Doppler sonars tracked the evolution of the larger scale bubble field. Bubble field and surface wave measurements provide the environmental background that must be incorporated in realistic propagation models. Bubble evolution models must in turn account for the currents and wave-induced turbulence, along with the loss of larger bubbles through buoyancy and effects of gas dissolution on smaller bubbles. We present a preliminary assessment of the observations and indicate the direction of required modeling efforts. [Work supported by ONR.]
A new k-space method for simulation of ultrasonic propagation in tissue
Authors: Mast T. Douglas , Liu D.-L. Donald , Souriau Laurent P. , Nachman Adrian I. , Waag Robert C.
Published: July 2002

A new k-space method for large-scale computations of ultrasonic propagation is presented. In the new method, spatial derivatives from the second-order acoustic wave equation for inhomogeneous media are evaluated by Fourier transformation. Solutions are advanced in time using a k−t space Green’s function. Computational results indicate that the new method shares advantages of both past k-space and pseudospectral methods. For scatterers with properties similar to soft tissue, the k-space method provides much higher accuracy and lower computational cost than a 2–4 finite-difference time domain method. The k-space method also allows high accuracy to be obtained for time steps much larger than those required by a leapfrog pseudospectral method. The low dispersion inherent to the k-space method is illustrated by large-scale quasi-one-dimensional computations, in which pulse waveforms incur negligible shape change for propagation distances as large as 1000 wavelengths. Example applications of the k-space method are demonstrated, including simulation of propagation through a large-scale tissue cross-sectional model and incorporation of a k-space solver into a nonlinear inverse scattering method employing eigenfunctions of the far-field scattering operator.
Should every physics student study acoustics?
Authors: Rossing Thomas D.
Published: July 2002

Should every physics student learn about sound? Many of my colleagues say ‘‘no;’’ I say ‘‘yes.’’ My arguments for restoring acoustics to the physics curriculum will be presented.
Nonlinear longitudinal waves in inhomogeneously predeformed elastic media
Authors: Ravasoo Arvi
Published: July 2002

The quasi one-dimensional problem of nonlinear longitudinal wave propagation in the elastic medium undergoing inhomogeneous plane prestrain is investigated theoretically. The analytical solution to describe the propagation of the wave with an arbitrary smooth initial profile is derived. The influence of the magnitude of the prestrain intensity on the distortion of the wave profile is studied. The sine-wave propagation in the medium subjected to the distributed static load is considered in more detail. The dependence of the sine-wave characteristics on the physical and geometrical properties of the medium and on the parameters of the predeformed state is clarified. The possibility to enhance the efficiency of ultrasonic nondestructive testing making use of the nonlinear effects of wave propagation is discussed. The algorithm to evaluation of the parameters of plane strain on the basis of wave profile evolution data is proposed.
Multifrequency plane, nonlinear, and dissipative waves at arbitrary distances
Authors: Hedberg Claes M.
Published: July 2002

A solution for multifrequency plane waves propagating through a dissipative and nonlinear medium is presented. It originates from the well-known Bessel function series ratio for a pure sinusiodal wave, introduced by Cole and Mendousse. The solution is exact. The only limitation, inherited from the single-frequency solution, is the slow convergence of the series when the nonlinearity is very large compared to the dissipation. Otherwise any frequencies, amplitudes and phases can be introduced in the original wave and the solution is valid for any propagated distance.
Extracting spectral envelopes: Formant frequency matching between sounds on different and modulated fundamental frequencies
Authors: Dissard Pascal , Darwin C. J.
Published: July 2002

The four experiments reported here measure listeners’ accuracy and consistency in adjusting a formant frequency of one- or two-formant complex sounds to match the timbre of a target sound. By presenting the target and the adjustable sound on different fundamental frequencies, listeners are prevented from performing the task by comparing the absolute or relative levels of resolved spectral components. Experiment 1 uses two-formant vowellike sounds. When the two sounds have the same F0, the variability of matches (within-subject standard deviation) for either the first or the second formant is around 1%–3%, which is comparable to existing data on formant frequency discrimination thresholds. With a difference in F0, variability increases to around 8% for first-formant matches, but to only about 4% for second-formant matches. Experiment 2 uses sounds with a single formant at 1100 or 1200 Hz with both sounds on either low or high fundamental frequencies. The increase in variability produced by a difference in F0 is greater for high F0’s (where the harmonics close to the formant peak are resolved) than it is for low F0’s (where they are unresolved). Listeners also showed systematic errors in their mean matches to sounds with different high F0’s. The direction of the systematic errors was towards the most intense harmonic. Experiments 3 and 4 showed that introduction of a vibratolike frequency modulation (FM) on F0 reduces the variability of matches, but does not reduce the systematic error. The experiments demonstrate, for the specific frequencies and FM used, that there is a perceptual cost to interpolating a spectral envelope across resolved harmonics.
New explicit solutions in acoustics of closed spaces on the basis of divergent series
Authors: Sumbatyan M. A. , Pompei A. , Rigano M. A.
Published: July 2002

A new approach to the acoustics of closed spaces is developed that involves solutions for polygonal shapes in explicit form. It is shown that exact solutions can be constructed for polygonal geometries where all the interior angles are equal to π/n (n is an integer). It is stated that the set of such polygons consists of the rectangle (known result) and three types of triangles. Some new explicit formulas are obtained for the eigenfrequencies of the triangles. It is demonstrated that the proposed technique also permits an exact representation of the impulse response function for the geometries described.
On analytic design of loudspeaker arrays with uniform radiation characteristics
Authors: Aarts Ronald M. , Janssen A. J. E. M.
Published: July 2002

Some notes on analytical derived loudspeaker arrays with uniform radiation characteristics are presented. The array coefficients are derived via analytical means and compared with so-called maximal flat sequences known from telecommunications and information theory. It appears that the newly derived array, i.e., the quadratic phase array, has a higher efficiency than the Bessel array and a flatter response than the Barker array. The method discussed admits generalization to the design of arrays with desired nonuniform radiating characteristics.
Music, Cognition, and Computerized Sound: An Introduction to Psychoacoustics
Authors: Tobias Jerry V.
Published: July 2002

The MIT Press, Cambridge, 1999.

xi+372 pp.+CD-ROM (formatted for Macintosh, for Windows 95, 98, and NT, and for Unix). Price: $60.000 hardcover.
Comments on “Ultrasonic flow metering based on transit time differentials which are insensitive to flow profile” [J. Acoust. Soc. Am. 74, 955–959 (1983)]
Authors: Willatzen M.
Published: July 2002

In a 1983 paper by H. Lechner, published in this journal, it was claimed that sound propagation in a flowing media confined by a cylindrical waveguide is characterized by mode phase speeds which, for small flows, do not depend linearly on flow. In particular, Lechner concludes that the phase speed of the fundamental mode changes with minus two times the average upstream flow as compared to the phase speed at zero flow. Downstream, the phase speed of the same mode is left unchanged with flow. In this comment, it is shown that changes in mode phase speeds with respect to flow will change sign when the flow direction is reversed disproving Lechner’s claim. Numerical calculations based on Sodha et al.’s paper published in Acustica [41, 232–237 (1979)], being the basis of Lechner’s work as well as this work, support the present analytical results for all modes.
Wave-number-based assessment of the doubly asymptotic approximation. I. Frequency domain wet surface impedance
Authors: Ginsberg Jerry H.
Published: July 2002

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.
Three-dimensional density spectra of sandy sediments
Authors: Tang Dajun , Orsi Thomas H.
Published: July 2002

Power spectra of density variability for sandy sediments offshore Panama City, Florida, are estimated and modeled using digital x-ray computed tomography images of sediment structure. Spectral analysis reveals that while shell pieces and mud mixtures are the main contributors to density variability at large scales, intrinsic density variability associated with sand grain contacts dominates at small scales. The power spectrum of sandy sediments is modeled by an analytic form that consists of two power-law components, one associated with the shell and mud contributions and the other with the intrinsic density variability of sand. The dominant term has a much higher power-law exponent than previously reported. Implications for the scattering of high-frequency sound in sandy sediments are discussed.