bluuebunny/crossref_metadata_2025 huggingface dataset:
Guided modes in a layered elastic half-space with doubly corrugated surfaces
Authors: El-Bahrawy Ahmed
Published: October 2005

Time-harmonic Rayleigh, Love, and Rayleigh–Lamb-like waves in a layer on a half-space with both the free surface and the interface doubly periodically corrugated are considered. The dispersion relation for the full problem is derived using the null-field approach. The stopband and passband structure of the physical modes are investigated numerically for doubly sinusoidally corrugated geometries with equal periods and equal corrugation heights. First the Rayleigh-like surface waves that exist when there is no layer are investigated. The passbands, stopbands, and damped parts are presented as a function of frequency and angle of propagation for two different corrugations heights. Some dispersion curves of wave number versus frequency are also given. With the layer present similar dispersion curves are given for some of the lowest Love and Rayleigh–Lamb-like waves. In general, the modes have a considerable angular dependence. Their resonance structure with respect to the position as well as the number of resonances and the stopband widths are affected. The passband, stopband, and the damped part for a mode as well as the possibility of an appearance of new physical solutions are also dependent on the corrugation height. More surprising is that some inhomogeneous modes become involved in the interaction pattern for the layered half-space, thus changing the characteristic behavior of the homogeneous modes and generating new passbands, stopbands, and damped parts.
Point force excitation of surface waves along the doubly corrugated traction-free boundary of an elastic half-space
Authors: El-Bahrawy Ahmed
Published: October 2005

The excitation of generalized Rayleigh waves due to the effect of a buried time-harmonic source located below the infinite, doubly periodically corrugated free boundary of a homogenous, isotropic, and linear elastic half-space is considered. The full elastodynamic equations are solved using the null-field approach (also called the T matrix method), and the contribution of the surface waves to the total displacement field in the vicinity of the boundary is obtained for the sinusoidally corrugated geometry with equal periods of corrugation. For different corrugation heights and frequencies and both a vertically and a horizontally directed point force excitation, numerical results are presented for the angular dependence of the surface field far away from the source where the generalized Rayleigh mode contribution dominates. When dealing with the horizontally directed point force the direction of the excitation in the horizontal plane is an important factor and it is explored numerically as well. In general, the far-field amplitude increases both with increasing frequency and corrugation height. It is smaller for a horizontal point force than a vertical one with the same location. As expected, the angular dependence of the amplitude is closely connected to the corresponding resonance and damped structure of the surface modes. Also, the appearance of stopbands or damped parts in the surface mode is followed by a disappearance of the far-field amplitude. The numerical computations are affected by some numerical instabilities that seem difficult to circumvent. Instabilities seem to arise when a residue of an inverse matrix is computed numerically and appear for all frequencies and corrugation heights for surface waves propagating at 0°, 45°, and 90° to the corrugations. Others appear only for certain frequencies and corrugation heights at other directions of surface wave propagation and seem to be a consequence of a cross-over resonance between the surface modes.
A study of seismic acoustic wave propagation through a laterally varying multilayered medium using the boundary-integral-equation–discrete-wave-number method
Authors: Haartsen Matthijs W. , Bouchon M. , Toksöz M. N.
Published: October 2005

In this paper the boundary-integral-equation method is employed along an acoustic/elastic interface of a seabed. The line source Green’s functions are based on a discrete-wave-number representation of an infinite acoustic ocean and a discrete-wave-number representation of the horizontally stratified elastic bottom. The bottom Green’s function, which adds in the elastic wave-field contributions of the horizontally stratified layers, is computed by the method of reflectivity and transmissivity matrices. In this paper the developed algorithm has been used to study scattering from irregular acoustic/elastic interfaces at ultrasonic frequencies. One model has been compared with real data collected in an ultrasonic modeling tank. The final section of this paper addresses the scattering of two acoustic/elastic rough interface models overlying a stack of solid layers with increasing velocity profile. The first seabed model has a syncline-shaped interface and the second is a syncline with a superposed sinusoidal component.
Resetting the pitch-analysis system. 2. Role of sudden onsets and offsets in the perception of individual components in a cluster of overlapping tones
Authors: Bregman Albert S. , Ahad Pierre A. , Kim Jean
Published: October 2005

Experiments on young adults studied the effects of suddenness of onset or offset on the discrimination of the order of pitches of individual tones in a 1-s, 4-tone cluster of overlapping pure tones. In experiment 1, the tones, all within a critical band, went on asynchronously. Each rose and decayed linearly in amplitude. Faster onsets, within the range 10 to 640 ms as measured on the first tone, increased the accuracy of the discrimination of the order of onsets, but 10-ms onsets were slightly worse than 40-ms onsets in early sessions. Experiment 2 found similar effects for the abruptness of offsets of tones in clusters whose components came on synchronously but went off asynchronously. Onset order was very much easier to detect than offset order. The auditory system may use neural onset and offset responses to reset itself and carry out new analyses at frequency-by-amplitude points of sudden amplitude change, thereby contributing to auditory scene analysis.
Stimulus classification procedure for assessing the extent to which binaural processing is spectrally analytic or synthetic
Authors: Dye Raymond H. , Yost William A. , Stellmack Mark A. , Sheft Stanley
Published: October 2005

A two-dimensional stimulus classification paradigm was used to assess the extent to which listeners’ processing of interaural delays at low frequencies is spectrally analytic or synthetic. Listeners were presented with a 753-Hz target with an interaural delay that varied from trial to trial, taking on one of ten values, five leading to the left ear and five leading to the right. A 553-Hz distractor component was simultaneously presented, with its interaural delay also presented at one of ten different values. During a block of 100 trials, each of the possible combinations of target and distractor delay was presented once, and only once, in a random order. Listeners were instructed to make left–right judgments based on the target delay. Each condition was repeated ten times, and the slopes of the best linear boundaries between left and right responses were used to derive the relative weights given to the target and distractor in judgments of laterality. Six of the nine listeners gave increasing weight to the target as the duration of the signals was increased from 25 or 50 to 400 ms. Three listeners showed little change with duration; one consistently gave equal weight to the target and distractor, two consistently gave greater weight to the target than to the distractor. The utility of classification paradigms in the study of multidimensional acoustic signals is discussed.
Evaluating residual background noise in human auditory brain-stem responses
Authors: Don Manuel , Elberling Claus
Published: October 2005

The nature of the residual background noise in ABR averages was empirically examined in normal hearing objects. The residual noise in the average was estimated with use of the technique described by Elberling and Don [Scand. Audiol. 13, 187–197 (1984)]. Low-level click stimuli were presented in 2-dB steps spanning the range from 30 to 48 dB p-p.e. SPL. For each stimulus level, 10 000 sweeps were acquired and stored for analysis. Shortcomings of the use of artifact rejection and standard averaging are demonstrated. It is further demonstrated how application of the Bayesian estimation technique of Elberling and Wahlgreen [Scand. Audiol. 14, 89–96 (1985)] to form weighted averages can help minimize these shortcomings. Finally, the effects of smaller sweep block sizes on the Bayesian technique’s ability to control the destructive effects of nonstationary noise are analyzed. Minimizing the destructive effects increases the value of statistical techniques used to detect objectively or to control the quality of ABR recordings. In all, these techniques in combination improve not only the accuracy of test interpretation but also the efficiency of clinical test time, which is becoming important for the control of medical costs.
Discrimination of speech-like contrasts in the auditory thalamus and cortex
Authors: Kraus Nina , McGee Therese , Carrell Thomas , King Cynthia , Littman Thomas , Nicol Trent
Published: October 2005

The neurophysiologic discrimination of acoustic contrasts was investigated as reflected by the mismatch negativity (MMN) response. Evoked responses were recorded from guinea pig thalamus (medial geniculate nucleus) and epidural surface in response to synthesized speech contrasts /ga/–/da/ and /ba/–/wa/. From the caudomedial portion of the medial geniculate nucleus, /ba/–/wa/ elicited a strong mismatch response, whereas /ga/–/da/ did not. Neither stimulus contrast elicited an MMN from the ventral, or primary, portion of medial geniculate. Both stimulus contrasts elicited an MMN from the midline surface. Neither contrast elicited an MMN from the surface over the temporal lobe. Results indicate a hierarchy of processing of the spectrotemporal changes which characterize formant transitions. Also, results indicate that the nonprimary portions of the auditory pathway contribute substantially to the MMN.
A hybrid solution for the response Green’s function of a fluid-loaded cylindrical shell
Authors: Cuschieri J. M. , Feit D.
Published: October 2005

A classical problem in structural acoustics is the response of a fluid-loaded cylindrical shell, with ring discontinuities or ring forces, to excitation by incident acoustic waves. The solution for these types of problems is generally formulated using integral transforms. The solution in the spatial domain is obtained by inverse transforming the wave-number solution. In past work, the inverse transform has been obtained by using either a contour integral approach or by introducing structural damping, thus removing the singularities from the integrand of the inverse transform. An alternative to these classical approaches, which does not require the introduction of structural damping, and therefore retains only the influence of the fluid loading on the response of the cylindrical shell, is a hybrid method which has previously been used for a fluid-loaded plate with a line discontinuity. Using this approach, the solution is not contaminated by the artificially introduced structural damping. Furthermore, the hybrid approach is more efficient computationally, especially when the evaluation of the response Green’s function is required. In this paper, the hybrid approach is applied to the solution of the displacement response Green’s function for a fluid-loaded cylindrical shell with a ring discontinuity, excited by an obliquely incident acoustic wave. The shell wall thickness to radius ratio is 0.01 and therefore thin shell equations of motion are used in the solution. The results presented are for the first circumferential mode (n=0). However, the approach can be used to generate results for other values of the circumferential mode number. At high frequencies, the results asymptotically approach those for a fluid-loaded plate. Also, for an axial load the results are in close agreement with results obtained on a shell with structural damping by other investigators.
On structure-borne sound: Experiments showing the initial transient acoustic wave field generated by an impacted plate
Authors: Wåhlin A. O. , Gren P. O. , Molin N-E.
Published: October 2005

The initial propagating transient acoustic field in air generated by an impacted plate is visualized. The transient traveling flexural waves in the plate created by the impact are shown, simultaneously. The experiments are performed using double pulsed holographic interferometry. It is shown that flexural waves in a plate act as a series of traveling acoustic sources. Since the flexural waves in the plate are dispersive the trace matched acoustical waves further away from the impact source propagate at a smaller angle relative to the plate than those closer to the impact. An observer situated close to the plate and away from the impact point will first receive high-frequency components of the sound. A quantitative evaluation of the acoustic field also shows that if there is a transient increase in pressure on one side of the plate there will be a similar decrease on the other side.
A dynamical problem on a N-electrode piezoquartz bar subjected to a temperature field
Authors: Munshi T. K. , Kundu K. K. , Mahalanabis R. K.
Published: October 2005

An attempt has been made to investigate analytically the mechanical response in a N-electrode piezoquartz bar such that two consecutive electrodes are separated by an unelectroded region under electrical and thermal excitations employing the equations of Maxwell, the equation of steady heat flow, and the relevant piezoelectric constitutive equations. The method of operational calculus and Green’s function have been used. The numerical results illustrate disturbances of the order of 10−7 m for a time scale ranging from t=0.1 to 1 s and the response becomes a linear function of time.
Reflection and refraction of the evanescent plane wave on plane interfaces
Authors: Deschamps Marc
Published: October 2005

Both the reflection and the refraction of a harmonic evanescent plane wave on an isotropic immersed layer are dealt with. Theoretical results are compared with experimental data. A bulk inhomogeneous (or evanescent) plane wave is generated in water by transmission through a prism made in an absorbing material. By using this method, the generated plane wave exhibits planes of constant amplitude orthogonal to the planes of constant phase. The incident wave propagates in the phase direction and is attenuated in its orthogonal direction. This wave is then reflected and transmitted by an isotropic and nonabsorbing layer. The most important result is the observation of reflection and transmission coefficients greater than unity. This effect agrees with the evanescent plane wave theory.
Effects of one-dimensional random rough surfaces on ultrasonic backscatter: Utility of phase-screen and Fresnel approximations
Authors: Bilgen Mehmet , Rose James H.
Published: October 2005

The effects of one-dimensional randomly rough surface corrugations on the time-dependent backscatter predicted by a simple model of the interaction of ultrasound with the microstructure of a sample are studied. Changes in the wave field that are due to surface topography, were calculated and compared by three different schemes: (1) the boundary integral element (BIE) method, (2) the phase-screen approximation (PSA), and (3) the PSA combined with the Fresnel approximation (which, as we report, yields an analytic series solution). Although the second and third schemes are easy to implement and accurate in some important cases, they are uncontrolled approximations that do not systematically estimate the resulting errors. The BIE method provides increasingly precise answers for a given model (at the cost of increasingly large numerical calculations) and was used to estimate the range of validity for the approximate methods. It is shown that the time evolution of the backscattered signal is approximately the same for the PSA as for the BIE calculations, aside from an overall time-independent constant. It is also shown that the approximate constant of proportionality depends strongly on the frequency, the correlation length, and the rms height; it is much less affected by the radius or the focal length of the probe. The constant of proportionality is presented both graphically and as a semiempirical formula and can be used to estimate and correct the error of the simpler PSA calculation.
The spatial correlation of rough seabed scattering of surface-generated ambient noise
Authors: Liu Jin-Yuan , Krolik Jeffrey L.
Published: October 2005

This article considers the effect of rough seabed scattering on the spatial correlation of low-frequency ambient noise. Extending the study presented by Liu et al. [J. Acoust. Soc. Am. 93, 753–769 (1993)], it is shown here that seabed roughness may alter the horizontal spatial correlation of the noise field primarily through the excitation of an interface wave along the bottom. The horizontal coherence and directionality of the noise field are shown to be a function of the correlation length and angular dependence of the roughness. Since the interface wave component decays rapidly away from the bottom, the vertical noise field correlation is minimumly affected by the seabed roughness. An examination of the noise field under two different statistical descriptions of seabed roughness, the Goff–Jordan and Gaussian models, shows that detailed differences in the roughness spectral shape produce only minor changes in the noise spatial correlation at infrasonic frequencies.
Bayesian estimation of Goff–Jordan seafloor microroughness statistics via simulated annealing
Authors: Premus V. , Alexandrou D.
Published: October 2005

A geophysically motivated stochastic model of seafloor morphology, characterized by an anisotropic, fractal-based description of the surface covariance function, has been introduced by Goff and Jordan [J. Geophys. Res. 93 (B11), 13,589–13,608 (1988)]. This paper describes a method for estimating Goff–Jordan rough surface parameters through acoustic remote sensing. The method employs a physical scattering model and optimum parameter estimation theory to connect the statistics of realistic small-scale bottom relief with the statistics of the backscattered acoustic field. It operates directly on the backscattered acoustic time series and is capable of inferring the stochastic properties of the seafloor on the order of the acoustic wavelength. Observations of backscatter angular dependence are simulated using full-field acoustic modeling derived from the 3-D Kirchhoff approximation to the Helmholtz integral equation. The optimum processor maximizes the joint a posteriori probability density of the five-dimensional surface roughness parameter set. Due to the complexity of the energy surface, the method of simulated annealing is used to search for the globally optimum solution vector.
Surface and volume scattering measurements using broadband explosive charges in the Critical Sea Test 7 experiment
Authors: Ogden Peter M. , Erskine Fred T.
Published: October 2005

Extensive measurements of low-frequency (70–1000 Hz) sea surface backscattering strengths have been made as part of the Critical Sea Test (CST) 7 experiment. These measurements were made for a variety of wind speeds from 3.0 to 17.5 m/s and for mean grazing angles from about 5 to 30 deg. The results from the CST-7 tests support the conclusions based on surface scattering strengths measured in previous CST SUS tests regarding the mechanisms controlling surface scattering and the frequencies and environmental conditions at which the mechanisms are important. As in previous tests, three scattering regimes were noted: a regime where results are generally consistent with scattering from a rough surface, a second regime where the frequency and grazing-angle dependences are much greater than expected from air–sea interface scatter but are consistent with scattering from subsurface bubble clouds, and a third regime that forms a transition zone between the other two regimes. The new measurements extend the range of environmental conditions over which these regimes are seen to substantially higher wind speeds than were obtained in the CST tests prior to CST-7. Volume scattering was observed to play a significant role in the measured results, with scattering from salmon the principal source of volume reverberation. Correlations of the measured scattering strengths were calculated for various environmental parameters and showed that the predictive ability of several wind speed-related parameters was improved by using a 2- to 4-h backaverage rather than the values taken during the runs.
The effect of internal waves on matched-field processing
Authors: Jackson Darrell R. , Ewart Terry E.
Published: October 2005

The performance of matched-field processing is degraded because of randomness of the propagation medium. Simulations and theory specialized to the Bartlett processor are used to study this type of environmental mismatch. The purpose is to quantify the effects of deep-water internal waves on matched-field processing. This is done at three different levels of approximation. First, the case of an ocean waveguide with a quadratic average sound-speed profile and vertically stationary sound-speed fluctuation statistics with Gaussian correlation is examined. Next, approximations are introduced so that a relatively simple analytic model can be abstracted from the theory. Finally, vertically nonstationary fluctuations obtained from a realistic, dynamic internal wave model are considered. In this case, a realistic average deep-water sound-speed profile, consistent with the internal wave field, is used. The results are found to agree with the predictions of the analytic model when the effects of multipaths are unimportant.
Ultrasonic absorption and velocity measurements for poly (vinyl alcohol) and water solutions
Authors: So Jin H. , Esquivel-Sirvent R. , Yun S. S. , Stumpf F. B.
Published: October 2005

The ultrasonic absorption and velocity at 21 MHz and also the shear viscosity were measured for poly (vinyl alcohol) and water solutions. The concentrations of poly (vinyl alcohol) by weight that were used were 1%, 3%, 5%, 9%. Measurements were made at 25°, 30°, 35°, 40°, and 45 °C. It was found that α/f2 decreased with increasing temperature and increased with increasing concentration. The wave velocity increased with both temperature and concentration. The shear viscosity was observed to decrease with temperature and increase with concentration.
Asymptotic forms of modal acoustic impedances for slender cylindrical radiators
Authors: Kritikos H. N.
Published: October 2005

An asymptotic form of the modal specific acoustic impedance is derived for the limiting case of an infinite slender axially symmetric radiating cylinder. This form allows the construction of a closed-form solution for the Green’s function that determines the axial surface pressure resulting from a ring velocity excitation on a infinite rigid cylinder. It also provides the means of constructing an approximate closed-form solution for the axial pressure distribution due to a finite axially symmetric velocity band with a cosine distribution on an infinite slender cylinder with rigid baffles. The approximate forms allow the pressure distribution to be be modeled as the sum of a pressure field derived from an infinite cylinder plus the radiation field of two ring sources arising from end effects.
The Heard Island papers: A contribution to global acoustics
Authors: Munk Walter , Baggeroer Arthur
Published: October 2005

Acoustic transmissions from a low-frequency source near Heard Island in the southern Indian Ocean were monitored at 16 sites worldwide. The results are presented in the following papers. A summary is presented of what has been learned about the dimensions of this new subject: global acoustics.
The development of the perception of cues to the [m]–[n] distinction in CV syllables
Authors: Ohde Ralph N.
Published: October 2005

The contribution of the nasal murmur and vocalic formant transition to the perception of the [m]–[n] distinction by adult listeners was investigated for speakers of different ages. Children, aged 3, 5, and 7, and an adult female and male produced consonant-vowel (CV) syllables consisting of either [m] or [n] and followed by [i æ u ɑ]. Three productions of each syllable were computer edited into the following segments: (1) full murmur; (2) 50-ms murmur preceding release; (3) 25-ms murmur preceding release; (4) 25-ms murmur preceding release+25-ms transition following release; (5) 25-ms transition following release; (6) 50-ms transition following release; and (7) full transition + vowel. The results indicate that both the murmur and transition provide cues to place of articulation, but that the latter property is more prominent in perception than the former across speaker age. The salience of the murmur and vocalic transition cues was greater for adults than children indicating a developmental progression of the encoding of gestures associated with these properties. Although the simultaneous presence of murmur and vocalic transition cues surrounding the point of spectral discontinuity improved perception of place of articulation across speakers, there was evidence of a developmental progression of this property also. For speakers of all ages, as segment duration decreased, consistent decrements in identification of place of articulation occurred only for transition stimuli. The murmur + transition was the most salient cue supporting the importance of spectral discontinuities and/or relational properties in production and perception particularly in the acquisition of sound features.
Single-sided determination of elastic constants of thick composites using acoustoultrasonic technique
Authors: Minachi A. , Hsu D. K. , Thompson R. B.
Published: October 2005

The determination of elastic constants is vital for any in-depth study of material performances. One of the more frequently used methods for elastic constant determination involves ultrasonic velocity measurements. Although this method is convenient in isotropic materials, it involves more complicated procedures for anisotropic materials. In this study, a measurement method is introduced that does not require cutting samples for velocity measurements in different directions. This method utilizes the acoustoultrasonic technique and deduces the elastic constants of transversely isotropic materials from the time-of-flight of obliquely reflected echoes which are received by another transducer placed on the same surface. Analytical and numerical analyses are described which reveal the sensitivity of the results to different kinds of measurement errors. It is reported that systematic errors are most detrimental to the extraction of elastic constants, and appropriate steps are demonstrated which reduce this kind of error. This method is experimentally tested on three unidirectional graphite/epoxy composite plates. Three of the elastic constants were found using pulse-echo velocity measurements normal to the top surface of the sample plate. The other two elastic constants were computed using acoustoultrasonic technique. The results show good agreement with nominal values of elastic constants obtained by cutting one of the tested samples.
Temperature variation due to ultrasonic absorption in a protein solution
Authors: Shin D. O. , Kim E. J. , Yoon S. W.
Published: October 2005

The temperature variation due to ultrasonic absorption in a protein solution has been experimentally investigated. Egg white and 10.6% ovalbumin solution were used as the samples of protein solutions. For ultrasonic absorption the continuous sound waves of 3.5, 5.0, 7.5, and 10.0 MHz from focused transducers were incident upon the samples of finite volume, respectively. The temperature variation was measured at the focal region of an ultrasonic beam in the sample. The measurements showed that the temperature variation in the egg white was much larger than that in the 10.6% ovalbumin solution. This discrepancy might be due to the differences in protein composition.
Tongue structural model: Integrating MRI data and anatomical structure into a finite element model of the tongue
Authors: Wu Chao-Min , Wilhelms-Tricarico Reiner
Published: October 2005

The goal of this research is to obtain a three-dimensional (3-D) tongue structural model as a reference placement for dynamic simulations of the tongue during speech articulation. The tongue structural model adapted to each individual’s anatomy will be developed by integrating tongue shape information from MRI scans and anatomical drawings to form an anatomical model. The data structure of this model will be a finite element mesh. Interactive programs written in matlab are developed to (i) manually extract tissue boundary information from MRI data of the tongue and other oral structure, (ii) combine this information with the anatomical drawings of cross sections of the human tongue to form an anatomical model, and (iii) fit a basic finite element model (topological model) to the anatomical model to form the tongue structural model for a sample vowel gesture of each subject. Both processes (ii) and (iii) will be achieved by a method of 3-D nonuniform geometrical mapping using a generalized thin-plate spline mapping. Two tongue structural models (one for a Caucasian native American male and another for an Asian native Japanese male) will be built, using MRI data obtained during a sustained vowel production. [Work supported in part by a NSF grant to Dr. O. Fujimura.]
Low levels of noise and resolution of their nuisance
Authors: Van Houten John J.
Published: October 2005

Noise ordinances provide objective standards which are used in the resolution of complaints, disputes, and land use compatibility concerns. However, application of the prevailing ordinance standard may indicate that compliance exists without adequately addressing the nuisance which motivated the complaint. The frustration of relentless noise and its related nuisance can be the motivation for litigation. Legal action may be the only remedy for its ultimate abatement. This paper will consider low levels of noise, less than the prevailing public agency standard, and will explore justification for the resolution of the nuisance which they may cause. Sources of such noise include a neighbor’s pool pump/motor or air conditioner, industrial equipment, transformers, combustion burners, pumping units, water flow in pipes, etc. Noise ordinance standards which prevail in California will be reviewed, and nuisance criteria will be identified. In addition, case histories will be discussed which will provide examples of the resolution of the nuisance caused by low level noise.
Acoustic scattering from a rigid sphere coated with multiple layers of absorbing materials: Eigenfunction expansion method
Authors: Sridhara B. S. , Rao Sadasiva M.
Published: October 2005

Far-field scattered properties for a rigid sphere coated with several layers of absorbing materials have been obtained using the eigenfunction expansion method. The sphere coated with m number of acoustic layers and placed in air, in a lossless situation, was considered. Compatibility conditions of sound pressures and sound velocities were applied at layer interfaces. The resulting (2m+1) complex linear algebraic equations involving material properties, and the spherical Bessel, Newman, and Hankel functions, were written in the matrix form. Computer codes were developed and the equations were solved for the coefficients which, along with other variables and parameters, were used to compute the scattered field properties. The formulation was verified by computing the far-field scattered parameter and comparing it with the available standard results. Far-field scattered properties were computed for a rigid sphere coated with a total of 12 different layers. In each case, the magnitude of the far-field scatter parameter was computed and plotted as a function of the angle in the range from 0° to 180°. It was observed that the scatter parameter was sensitive to the change in the angle and the variation was relatively large in the range from 100° to 160° in the case of certain layers.
Evidence of gestural overlap across speaking rate: Acoustic data
Authors: Tjaden Kris , Weismer Gary
Published: October 2005

The form of phonetic gestures has been assumed to remain stable across variations in speaking rate. Segmentalization or amount of gestural overlap has been shown to covary with speaking rate. However, the precise relationship between speaking rate and acoustic measures of segmentalization has not been delineated. In the present investigation, speakers produced multiple repetitions of the words ‘‘build,’’ ‘‘dill,’’ and ‘‘gill’’ in carrier phrases at graded, self-selected speaking rates ranging from slow to fast. F2 onset frequency of the vocalic nucleus served as an index of segmentalization and was used to predict the time delay to the onset of the major F2 transition associated with /I1/. Previous work suggests F2 onset frequency is sensitive to degree of gestural overlap in vocalic nuclei preceded by alveolar consonants. Preliminary results suggest (1) longer vocalic nuclei tend to be associated with F2 onset frequencies closer to the preceding consonantal articulatory locus, and (2) the linear relationship between F2 onset and time to target deteriorates above certain speaking durations, suggesting that the basic form of the gesture is altered at slower rates. [Work supported by DC 00319.]
State switched acoustic source
Authors: Larson Gregg D. , Rogers Peter H.
Published: October 2005

To produce high amplitude low-frequency signals, an underwater transducer must generate a relatively large volume displacement. Since water exerts a large reaction force back on the transducer, ‘‘conventional wisdom’’ dictates that such a transducer would have to be a high Q resonant device and thus not be broadband as seemingly required for many applications. However, a transducer does not have to be broadband in the conventional sense to work in communication and SONAR systems. A transducer capable of switching between two discrete frequencies is adequate for communication and one capable of switching among several frequencies could produce chirp signals for active sonars. Ordinarily, a broadband transducer is needed to switch frequencies rapidly. It is theoretically possible, however, to instantaneously switch frequencies with a high Q resonant system provided that the system’s resonant and drive frequencies are altered simultaneously. Such a ‘‘state-switched’’ transducer [Munk, Webb, Birdsall, unpublished (1980), (1981)] would retain the advantages (high power, high efficiency, and large displacements) of a high Q resonant transducer without the accompanying disadvantage of slow response time. A state-switched acoustic source with an active spring of PZT has been built to demonstrate the state switching concept. [Research supported by ONR 334.]
Coupling finite element and impedance element to model the radiation of piezoelectric transducers in boreholes
Authors: Ekeom Didace , Dubus Bertrand
Published: October 2005

In the context of petroleum acoustics, it is of great interest to modelize the radiation of the piezoelectric transducer in a borehole surrounded by an homogeneous isotropic elastic formation of infinite extent without restrictive assumptions on the geometry, radiation pattern, or types of waves. The finite element method is well suited to solve such problems if the troncature of the infinite formation is correctly treated. This troncature generates ingoing waves which normally do not exist in infinite domain. In this paper, classical finite elements (atila code) are used to model in steady state the transducer, the fluid-filled borehole, and part of the formation inside a spherical boundary. On this exterior boundary, impedance elements are used to take into account the infinite character of the formation. These elements are obtained by discretizing the mechanical impedance of outgoing spherical P and S waves. The method is validated by studying two configurations having analytical solutions: the pulsating sphere and the oscillating point. Results include displacement fields and radiation patterns for P or/and S waves. Finally, the radiation of a cylindrical piezoelectric transducer in an oil-filled borehole [S. Kostek etal., J. Acoust. Soc. Am. 95, 109 (1994)] is analyzed. P and S components of the displacement field, electrical admittance of the transducer, directivity patterns, and distribution of radiated energy are displayed.
Equal-likelihood probability modeling in active and passive sonar
Authors: Pitre Richard
Published: October 2005

The equal-likelihood rationale [R. Pitre and N. R. Davis, J. Acoust. Soc. Am. (to be published)] for the selection of probability models has been extended and strengthened. The method is shown to be optimally robust, testable, and correctable. Nonlinear parameter estimation and filtering equations are developed based on this formalism and its application to modeling active sonar in a random waveguide is formulated. [Work sponsored by ONR.]
Historical temperaments analysis system
Authors: Esbri Alejandro S.
Published: October 2005

This paper describes in a succinct form an historical temperaments analysis system designed for musicians with advanced knowledge of intervalic theory. By introducing the concept of positivetrajectoryreduction in the fifth circle diagram of the temperament to be analyzed, it is possible to do a very fast calculation of the size of any interval inside that temperament, within an error of ±1 cent. The corresponding exact frequency ratio becomes obvious in many cases and it is easy to summarize all the intervalic information in one analysis sheet. In addition to the fifth circle diagram, this sheet includes frequency ratios for the chromatic, diatonic, and hexatonic scales (especially their size in cents), intervals with respect to the tonic, and the deviation in cents of each note from equal temperament. With this system, piano tuning students can make comparisons of different temperaments, classify them, and understand their practicability for different types of keyboard music. Besides, the practical tuning instructions for each temperament can be comprehended much better. Also, with this analysis system, composers and keyboardists are able to program any temperament in an electronic synthesizer with user-tuning option, and the system is even helpful for creating new temperaments.
Selected topics in computational ray methods
Authors: Hackman Roger H. , Sammelmann Gary S.
Published: October 2005

Several selected topics intimately involved with the application of ray theory to acoustic scattering are discussed. The first topic is the application of quantitative ray theory to the low-frequency acoustic scattering from large aspect ratio solids. In this approach, the scattering amplitude is developed as a time-ordered perturbation series. The series for the elastic response is explicitly summed to obtain a closed form expression that is analogous to results obtained for spherical and infinite cylindrical geometries through application of the Sommerfeld–Watson transformation. Emphasis is placed on novel features that have no counterpart on these simpler geometries (e.g., ‘‘bipolar’’ coupling phenomena) and their implications for resonance excitation. A second topic deals with a near-field/far-field target strength model for more complicated geometrical shapes that is under development at CSS. But theoretical and experimental results are presented. A third topic is the high-frequency ‘‘quasi-resonance’’ phenomenon of thin shelled structures. The structure of the ‘‘quasiresonance’’ mode is obtained for both complex wave number (real frequency) and complex frequency (real wave number) extensions of the reflection coefficient for a fluid loaded flat plate. The results are used to synthesize the scattering amplitude for spherical shells using forms previously derived for the Sommerfeld–Watson transform.
Effect of mass loading on the dynamic behavior of a three-dimensional truss
Authors: Bondaryk Joseph E. , Dyer Ira
Published: October 2005

Recent trends in submarine design suggest the use of trusslike structures, connected to the hull by a limited number of attachment points, to support rotating machinery and decks with passive loads. The ratio of the supported mass to the truss mass is high, typically 5–10. This loading must affect the dynamic response of the truss. It is believed that resiliently mounted mass will have a ‘‘fuzzy’’ effect on the truss and result in damping of structural waves. The MIT Structural Acoustics Group is making experimental measurements on a 1:15 scale model of a nonpractical, 3D, submarine truss, constructed of 0.5-in. aluminum tubing, up to frequencies of 5 kHz. The dynamic response of two identical trusses, one unloaded and one mass-loaded at a ratio of 5:1, to octave-band noise are measured and compared. The results show the effects of passive and resiliently mounted mass loading on a truss structure. [Research supported by ONR.]
Acoustic modeling of plasma-induced vapor bubbles
Authors: Hess Gary R. , Rodriguez Arturo E. , Winsor Niels K. , Young Chris M. , Crum Lawrence A. , Stellingwerf Robert F.
Published: October 2005

Plasma-induced bubbles respond to time-dependent injection of energy which modifies the acoustic output relative to ‘‘classical’’ gas bubbles. Additionally, they consist primarily of hot vapor which complicates the thermodynamics, elevates the importance of some traditionally untreated variables, and requires additional physical process treatments beyond the basic hydrodynamics. A code that is based upon fundamental physical principles was developed to study the importance of many of these variables. The code is capable of treating the actual driving circuit, resultant plasma behavior, transition from cylindrical to spherical geometry early in the discharge, radiation production, plasma chemistry, thermal transport, and hydrodynamics in a modified Flynn formulation. Primary output consists of bubble wall acceleration, radius, etc., energy balance, and far field pressure. The code has been validated with experimental data and will be compared with ongoing hydrocode model development as well. Experimental and theoretical results are presented for large vapor bubbles. [Work supported by the U.S. Navy.]
Considerations of errors in computer-based measurements
Authors: Wallis Alan D.
Published: October 2005

The use of computers has come to dominate acoustical measurements as was predicted at ICA 1983 in Paris. However, what was not predicted was that a generation of acousticians would arrive with no previous experience of older analogue systems. To some of these new generation workers, ‘‘the computer is always right’’ and little or no thought is given to the limitations and accuracy restrictions of a totally digital system. Automatic checks routinely done before and after measurements on previous generations of instruments are sometimes ignored, while instrument tolerances are assumed to be zero and calibrations are assumed to be perfect even though logic suggests otherwise. Consideration is given to making basic checks on computer based instruments, so that reasonable reliance can be placed on the results, often using old and traditional methods brought up to data and translated from the analogue to the digital world. Sample case histories of particular ‘‘real world’’ errors are given, with some idea of the practical limitations of new technology instrumentation and where they sometimes fall short of older units. These are compared with some requirements of ANSI and international standards.
Theoretical prediction of luminescence from acoustically driven cracks
Authors: Löfstedt Ritva , Putterman Seth
Published: October 2005

Under the effect of an intense long wavelength sound field the length of a crack in a solid medium should oscillate. When the crack length is increased the imposed acoustic energy is focused down to regions of atomic dimension so as to break the fundamental bonds which determine the crystal structure. It is suggested that this energy comes out as light whose intensity is periodic with the sound wave. This analysis is based upon the elliptical model of a crack modified to include surface tension. [Work supported by the U.S. DOE Office of Basic Energy Science, Division of Engineering and Geophysics; R.L. is an AT&T Fellow.]
On asymmetrical motions of cavitation bubbles
Authors: Shi Tao , Apfel Robert E.
Published: October 2005

The phenomenon of sonoluminesence has been of considerable recent interest due to a better understanding of two types of mechanisms: asymmetrical collapse of transient bubbles and single gas bubble oscillation. Asymmetrical collapse of transient bubbles result in lower sonoluminescence temperature; asymmetrical shape modes may also disturb the periodic stability of single gas bubble oscillation. The boundary integral method has been used to study the asymmetrical motions of bubbles of initial diameters of 1–100 μm. The role of initial bubble shape perturbation, dissolved gas saturation, surface tension, and maximum bubble size are observed up to a point where assumptions concerning the maximum bubble wall velocity and the internal bubble dynamics are expected to break down. It is observed that the initial shape perturbation grows when the bubble collapses and decays when it expands. Therefore, it appears that there are circumstances when cyclic single bubble oscillations can occur even with significant shape distortion. [Work supported by Jet Propulsion Lab through Contract No. 958722.]
Active sound extraction for noise control
Authors: Madanshetty Sameer I. , Chu Boa-Teh
Published: October 2005

A method of controlling the noise level in duct flows is described. The method is based on the principle of energy extraction by active source(s), rather than by wave cancellation as in ‘‘antisound.’’ As such the method of energy extraction is robust; it does not need the delicate signal processing, perfect phase, and amplitude matching, crucial to sound cancellation. Two useful modes of control are discussed, one for quieting low frequencies and the other effective for higher frequencies. The possibility of perfect ‘‘noise trapping’’ in a finite region is also considered, even though it is difficult to implement such complete control in practice. A preliminary experiment that substantiates the concept is described. Extension of this method of noise control to three-dimensional cases is also briefly discussed.
Scholte interface wave on a cylindrical shell
Authors: Maze G. , Léon F. , Lecroq F. , Décultot D. , Überall H.
Published: October 2005

The fluid-borne interface wave on an evacuated cylindrical shell immersed in water is known as Scholte–Stoneley wave, or also as A wave [Talmant etal., J. Acoust. Soc. Am. 86, 278 (1989)]. The resonances of this wave, caused by phase matching upon its multiple circumnavigations of the scattering object, can be observed in the backscattering spectra of incident sound waves within a frequency window that depends on the shell thickness, for thicknesses less than 40% of the cylinder radius. The interaction between the flexural wave A0 in the shell, and the Scholte wave is studied in detail as a function of shell thickness. Dispersion curves for the A and the A0 waves are presented, indicating a region of repulsion between these two curves corresponding to a change of the physical nature of the two waves.