bluuebunny/crossref_metadata_2025 huggingface dataset:
Electroelastic modeling of the motions of ceramic bars under large driving voltages
Authors: Dökmeci M. C. , Altay G. Aşkar
Published: October 2005

In relation to electroceramic media subject to large driving voltages, this paper presents the one-dimensional nonlinear equations of a cylindrical ceramic bar. The field variables of the ceramic bar are all expanded in the power series expansions of its cross-sectional coordinates. By means of a unified variational principle, which is formulated through Hamilton’s principle and Legendre’s transformation [e.g., M. C. Dökmeci, IEEE Trans. UFFC 35, 775–787 (1988)] together with the series expansions of field variables, the one-dimensional electroelastic equations are systematically derived in both differential and variational forms. They are capable of predicting the extensional, flexural, and torsional as well as coupled motions of a ceramic bar at low and high frequencies. By a proper truncation of the series expansions, the electroelastic equations incorporate as many higher-order effects as deemed desirable in any case. Special cases are investigated [cf. M. C. Dökmeci, Int. J. Solids Struct. 10, 401–409 (1974) and Proceedingsofthe 40thAnnualSymposiumonFrequencyControl (IEEE, New York, 1986), pp. 168–178]. The uniqueness is examined in solutions of the linearized electroelastic equations. [Work supported in part by The Scientific and Technical Research Council of Turkey.]
Investigation of the vibroacoustical characteristics of cylindrical shells
Authors: Dudnik Rostislav A. , Kolpakov Andrei B.
Published: October 2005

Experimental and theoretical investigations of the influence of inhomogeneity upon the oscillations and radiation of thin cylindrical shells are executed. The inhomogeneity is presented by either one additional mass (m0) fastened (at Φ=180°) on the shell surface, or two identical inertia masses (m1=m2=m0/2) which are fastened at Φ=±Φ1. The impact of such division of a unit inhomogeneity on oscillating velocity distribution as well as on the pressure radiated levels and directionality diagrams of the relevant shell models is analyzed for different quantities of summary mass (m0). The execution analysis is limited by the investigation of azimuth lower-frequency modes. It was shown that the considered distribution of inhomogeneity makes it possible to control the radiation level of the shell in certain frequency ranges. The investigation of a structure of near and far acoustical fields radiated by these shells at various distances from the radiating surfaces was conducted also. It was shown that as this distance increases, the number of the mode providing the largest contribution to the complete field decreases. Corresponding experimental results are presented.
Recovery of task-dynamic parameters with a mismatched articulatory model
Authors: McGowan Richard S. , Lee Mindy
Published: October 2005

A method for recovering task-dynamic parameters from speech acoustics has been proposed [see McGowan, Speech Commun. 14, 19–48 (1994)]. In the series of tests to be described here, there were mismatches imposed between the task dynamics that produced the speech data and the task dynamics used in the analysis-by-synthesis procedure for recovery. One of the mismatches was in the articulator weights used in specifying how much of each articulator to use in attaining construction goals. Another mismatch was in the allowed relation between activation interval and the natural frequency of the constriction dynamics (natural frequency constraint). Bilabial and velar places of articulation (constriction) were tested, and the first three formant trajectories were used as data. When there was articulator weight mismatching, it was found that articulators would compensate so that the recovered constriction trajectories were similar to those of the data producing trajectories. It appeared to be more difficult to overcome mismatches in the natural frequency constraint. Also, the nonuniqueness of the recovered task dynamics is exhibited when there is not sufficient acoustic data. [This work was supported by NINDCD Grant 01247 to Haskins Laboratories.]
Influences of stop consonant voicing on tongue, lip, and jaw movement kinematics
Authors: Löfqvist Anders , Gracco Vincent L.
Published: October 2005

Lip closing movements for bilabial stops have been reported to be faster and of shorter duration for voiceless than for voiced stops. The experimental evidence is conflicting, however, and recordings have mostly been limited to lip and jaw movements in a single dimension. The present study examines articulatory kinematics in /aCV/ sequences, where the consonant is one of the set /p,b,t,d,k,g/ and the second vowel one of /i,a,u/. A magnetometer system was used to track vertical and horizontal movements of receivers placed on the lips and the jaw, and on four points on the tongue. Tangential velocity was used to define movement onsets and offsets. Movement amplitude was calculated as the path of the receiver from movement onset to offset. Preliminary results from two subjects suggest the possibility that the effects of consonant voicing on movement kinematics vary for different articulators. Tongue body movements towards consonantal closure had consistently higher velocity, larger amplitude and longer duration for voiced than for voiceless velar stops. Tongue tip and lip and jaw closing movements showed less robust differences between voiced and voiceless alveolar and labial stops. [Work supported by NIH.]
Evaluating a topographical mapping from speech acoustics to tongue positions
Authors: Hogden John , Heard Michelle
Published: October 2005

The continuitymapping algorithm—a procedure for learning to recover the relative positions of the articulators from speech signals—is evaluated using human speech data. The advantage of continuity mapping is that it is an unsupervised algorithm; that is, it can potentially be trained to make a mapping from speech acoustics to speech articulation without articulator measurements. The procedure starts by vector quantizing short windows of a speech signal so that each window is represented (encoded) by a single number. Next, multidimensional scaling is used to map quantization codes that were temporally close in the encoded speech to nearby points in a continuitymap. Since speech sounds produced sufficiently close together in time must have been produced by similar articulator configurations, and speech sounds produced close together in time are close to each other in the continuity map, sounds produced by similar articulator positions should be mapped to similar positions in the continuity map. The data set used for evaluating the continuity mapping algorithm is comprised of simultaneously collected articulator and acoustic measurements made using an electromagnetic midsagittal articulometer on a human subject. Comparisons between measured articulator positions and those recovered using continuity mapping will be presented.
Acoustic resonances in square cross-sectional rods (preliminary results)
Authors: Beige Jerome , De Billy Michel
Published: October 2005

As it was observed, it is shown that for particular frequencies, a square cross section normally insonified gives rise to resonance phenomenon. This is illustrated by using two different acoustic approaches: a dynamic visualization of the pressure scattered by a square bar and a measurement of the reradiated acoustic pressure in a plane normally oriented to the axis of a square rod. Different structures of the angular patterns are observed according to the nature of the excited guided mode. The experiments were performed on specimens of different materials such that the value of the product of the frequency times the width of the rod is less than 28 MHz mm. A theoretical approach based on the Fraser’s work [W. B. Fraser, Int. J. Solids Structures 5, 379–397 (1969)] will be proposed.
Relation between the damping coefficient and the excitation coefficient of leaking Lamb waves
Authors: El Kettani M. Ech Cherif , Luppé F. , Conoir J. M. , Ripoche J.
Published: October 2005

The relation between the leaking ability and the excitation coefficient of a propagating Lamb wave on an immersed plate is studied. The more the Lamb wave radiates during its propagation, the more strongly it is expected to be excited from the incidence of an ultrasonic beam at the appropriate angle. The excitation coefficient of a given Lamb wave at a given frequency–thickness product is obtained from a residue calculation. It is numerically achieved from the exact formulation of the reflection coefficient, and analytically performed with the help of the resonance scattering theory approximations. Both methods exhibit clearly the proportionality of the excitation coefficient with the normalized damping coefficient. The direct measurement of the excitation coefficient is not possible because of the interference phenomenon of the Lamb wave radiation with the specularly reflected beam. Consequently, the measurements are performed far away from the interference area. The linearity of the pressure amplitude (in dB) with the propagation distance allows the direct determination of the damping coefficient, as well as the extension of the experimental data to the interference area. The excitation coefficient is herefrom deduced. The results confirm the theoretical ones. [Work supported by D. R. E. T., France.]
Geometrical theory of diffraction applied to Scholte wave diffraction
Authors: Duflo H. , Tinel A. , Duclos J.
Published: October 2005

The geometrical theory of diffraction (GTD) has been established by Keller in order to describe the interaction of a bulk wave with a dihedral edge. It was experimentally verified that Keller’s laws were also valid to describe the interaction of a Scholte wave with the edge of an elastic dihedral. When the Scholte wave met the dihedral at oblique incidence, the diffracted energy was actually on Keller’s cone the axis and generatrix of it were respectively the dihedral edge and the direction of the incident Scholte wave. It was assumed that incident energy spread among a bulk wave in the direction of the incident Scholte wave as well as reflected and transmitted surface waves (Scholte and Rayleigh waves). The direction of emission of these waves was calculated as a function of dihedral and incidence angles. This calculus showed that Rayleigh waves did not exist if the incidence angle was higher than the Rayleigh angle. Experimental results were obtained for duraluminum dihedrals of various angles ranging from 30 to 90 deg and for incidence directions between 0 and 45 deg. Diffracted energy was only noted on Keller’s cone. [Work supported by D.R.E.T.]
Lamb waves of two elastic plates coupled by a thin water film
Authors: Rousseau M. , Coulouvrat F. , Lenoir O. , Khelil H. , Izbicki J. L.
Published: October 2005

This experimental and theoretical study investigates the guided waves that propagate along a multilayered structure, composed of two identical, infinite, aluminum plates coupled by a thin water film. The related dispersion equation is written under a closed form. Solutions are calculated numerically to draw the dispersion curves. The low- and high-frequency limits are calculated analytically. Special attention is devoted to the determination of the cut-off frequencies. An asymptotic analysis shows that, in most cases, a doubling of the classical Lamb waves happens. The small deviation of the cut-off frequencies from the classical ones has been evaluated. An additional, single mode is also outlined; its cut-off frequency is smaller than the Lamb waves ones and depends heavily on the water film thickness. The experiments have been performed on 3- and 5-mm aluminum plates insonated at normal incidence by short pulses. The reflected signal is then FFT-processed; depending on whether the specular echo is removed or not, a resonance or a backscattered spectrum is obtained. The doubling of the Lamb waves, and the existence of an additional low-frequency mode, have been thus confirmed. For a structure composed of three aluminum plates, the experiment now outlines families of three models, each family being closely related to one classical lamb wave.
Acoustics of fluid conveying elastic structures
Authors: Grinfeld Michael A. , Norris Andrew N.
Published: October 2005

Acoustic waves are considered that are propagating in a layered structure consisting of elastic layers with ideal fluid moving between them. This is a simple model of a fluid-filled porous medium. First discussed is the dependence of the dispersion curves on the relative velocity of the fluid and on the material and geometrical parameters of the constituents. Dispersion relations for a periodic layering are derived explicitly. Different asymptotic limits can be obtained, which reduce to known solutions for interfacial acoustical wave motion in the presence of flow. The main focus of this talk is the possibility of instabilities triggered by the moving fluid in the layered system. The role of such acoustical instabilities in nonlinear dynamics of poroelastic fluid-filled media is discussed. This effect can be viewed as a generalized flutter phenomenon, made possible by the permeability of the pore space. [Work supported by ONR.]
Guided sound propagation in three-dimensional inhomogeneous moving nonstationary fluid
Authors: Godin Oleg A.
Published: October 2005

Sound propagation in a multicomponent fluid, parameters of which including flow velocity as well as shape of boundaries are smooth and slowly varying functions of time and two horizontal coordinates, is considered. No limitations are imposed on the Mach number and the fluid parameters dependence on the vertical coordinate other than the assumption that sound/flow synchronism points are absent. All the processes in the fluid are assumed to be adiabatic. The method of two-scale expansions is used to construct asymptotic development of solutions of the set of hydrodynamic equations linearized with respect to the wave’s amplitude. The well-known ‘‘vertical modes-horizontal rays’’ approach is generalized to cover acoustic waves in nonstationary moving media. An adiabatic invariant is found that governs the amplitude variation of a normal mode along the corresponding space-time horizontal ray. Physical meaning of the adiabatic invariant is analyzed. Results are compared to those of recent studies of guided propagation in moving time-independent [O. A. Godin, DAN SSSR 320, 204–208 (1991)] and unstationary motionless fluid [A. V. Aref’ev and V. S. Buldyrev, Akust. Zh. 40, 205–211 (1994)]. The importance of a consistent account of medium’s motion and its time dependence is demonstrated. [Work supported by RBRF and NRC.]
Effects of stress, vowel duration, and vowel height on the timing of pitch peaks in Czech
Authors: Bartels Christine
Published: October 2005

Czech is described as having word stress fixed on the first syllable, independent of vowel quantity. The pitch peak of a word generally falls on that first, stressed syllable. However, in some environments, the pitch peak shifts to a later syllable, leading to the perception that this later syllable is more prominent. This study investigated the phonetic factors conditioning such divergent placement of stress and pitch peak in Czech. Native speakers produced contextually embedded trisyllabic nonsense words with high-pitch accents. Vowel height and quantity in the first and second syllable were independently varied to assess their effect on syllable pitch and the timing of the pitch peak. Whether a syllable was stressed constituted the third independent variable in the analysis. To determine whether stress remained on the first syllable, the timing of stress-related properties, i.e., amplitude and syllable lengthening, was examined. Results showed that a high vowel in either syllable tended to raise the pitch, but the second vowel could only attract the pitch peak if the first vowel was short and low. A long first vowel prevented accent shift to the second syllable. Stress-related properties remained largely confined to the first syllable, although the amplitude maximum occasionally shifted to the second syllable, if long.
Acoustic and kinematic evidence for difference in language timing structure
Authors: Dunn Margaret H.
Published: October 2005

Proposed differences in the timing organization of Italian and Finnish are examined from the perspectives of simultaneous acoustic duration and bilabial movement (selspot tracked) collected from four native speakers of each language. All utterances were disyllabic, shaped CVC(C)V for Italian and CV(V)C(C)V(V) for Finnish. Italian, generally believed to be syllable-timed, shows regular acoustic intervals between vowels implemented by shortening of the initial vowel in closed syllables. Movement data shows that shortening is achieved by early initiation of clusters and geminate consonants, truncating the initial vowel. Finnish, generally described as mora-timed, shows increments of acoustic duration of disyllabic utterances with the addition of moras, either to vowels or to medial consonants. An apparent constraint on syllable duration leads to acoustic shortening of both initial vowels and intervocalic consonants in the longest utterances. Movement data show that increases in quantity affect both medial consonant and preceding vowel portions of utterances. It is proposed that syllable-timing works directly from vowel to vowel, while mora-timing allows increase in duration of disyllabic utterances, adjusting both vowel and consonant durations to fill out or limit the possible intervals between vowels. [Work supported by NIH Grant DC 00121 to Haskins Laboratories.]
Further results from modeling deep-ocean reverberation from the Mid-Atlantic ridge
Authors: Chin-Bing Stanley A. , Murphy Joseph E.
Published: October 2005

Results comparing computer model simulations and reverberation data [Chin-Bing and Murphy, 3328(A) (1994)] have been reported previously. The reverberation data were taken from the Mid-Atlantic ridge region during the 1993 Acoustics Experiment as part of the ONR Acoustic Reverberation Special Research Program (ARSRP). A representation of the rough, range-dependent ocean sediment and sub-bottom bathymetry of the region was obtained from geomorphological models (the Webb–Jordan sediment distribution model and the Goff–Jordan fractal seafloor/basement model). A modified version of the Collins fepe2way model was used for the long-range reverberation predictions. Our model simulations compared favorably with 210- to 290-Hz bandwidth reverberation data gathered from ‘‘site A, seg 076.’’ In this continuing study of site A, seg 076, the fframe and safe models are being used to study the influence of heavily sedimented regions on reverberation. New modeling results will be presented and compared with the measured reverberation. [Work supported by Office of Naval Research, Acoustic Reverberation SRP, and a High Performance Computing DoD Shared Resource Center grant.]
High-frequency acoustic penetration into seafloor sediments at subcritical grazing angles due to roughness at the water–sediment interface
Authors: Thorsos Eric I.
Published: October 2005

Acoustic penetration into sediments at low grazing angles is of interest for buried mine detection. For sandy sediments the critical angle can be in the 25°–30° range, which suggests that penetration at lower grazing angles might be quite limited. It will be shown, however, that when the sediment roughness is modeled to be consistent with the occurrence of sand waves, then significant penetration into the sediment can occur at subcritical grazing angles due to scattering at the rough interface. An integral equation method is used to obtain acoustic fields near the surface to illustrate the degree of penetration. A 1-D surface model is used, and the sediment is modeled as a fluid. For a given surface profile, the acoustic penetration is found to increase as the frequency increases. When the frequency is reduced to bring the roughness into the perturbation theory region, acoustic penetration is much reduced. [Work supported by ONR.]
Acoustics of a bell with a tube on its head
Authors: Chen Tong
Published: October 2005

Temple bells in Korea are quite special as compared with bells in other countries. The bell has a tube on its head and a pit or cavity (‘‘rumbling structure’’) under it. The acoustical behavior of the bell and its pit has been modeled as a cylindrical cavity with an air gap. The air gap changes the mode frequencies and damping factors of the cavity; the damping factor increases sharply with increase in length of the air gap, especially for some modes. In real cases, the air gap between the bell and the rumbling structure is limited to 0.3–0.4 m. The tube on the bell is effective for radiation of sound only when its length is nearly an integer times the half-wavelength of a cavity mode. It is reasonable to adjust the tube length for the most prominent partial in the bell sound, which determines the strike note. The acoustic mode frequencies can be tuned by adjusting the depth of the pit and the length of the tube to improve the timbre of the bell sound.
A linear filter approximation to the hammer/string interaction for use in a commuted synthesis piano model
Authors: Van Duyne Scott A. , Smith Julius O.
Published: October 2005

In commuted synthesis of string instruments, the soundboard/body resonator is commuted to the excitation point and replaced by its own impulse response [Smith and Van Duyne, elsewhere in this session]. Hence, the highly nonlinear hammer/string interaction must be replaced by a commutable linear filter. Using the wave digital hammer computational model of the piano hammer [ 3300(A) (1994)], it was observed that the force pulse of a hammer striking an infinite string was qualitatively similar to the impulse response of a second-order filter with two real poles. Hence, good second- and higher-order filter designs based on physical data were possible. However, multiple humps may appear in the hammer force pulse on a terminated string due to returning string waves. It was observed that the magnitude spectra of the single hump spectrum and the multiple hump spectrum were similar in bandwidth, differing only in a slight ringing in the lower spectrum due to the lowpassed combing effect of the returning string waves. Therefore, an equalization filter was designed to summarize this combing effect by fitting a bank of parallel second-order sections to the complex ratio spectrum. Excellent linear piano hammer simulations were produced.
Equivalence of finite difference approximation and digital waveguide modeling for lossless, nondispersive media in one to three dimensions
Authors: Smith Julius O. , Van Duyne Scott A.
Published: October 2005

The finite difference approximation method is commonly used to convert a differential equation into a recursive computation for computer simulation of an acoustic medium. Less well known is the digital waveguide modeling approach to the same problem, which is based on simulating the propagation of sampled traveling waves in the medium, and which implements losses and dispersion using digital filters applied to the traveling waves [Comput. Music. J., 74–91 (Winter 1992)]. It turns out the two methods are equivalent in rectilinear coordinates in one, two, and three dimensions, in the lossless, nondispersive case, provided the spatial sampling interval is chosen to be a specific constant (c in the one-dimensional case) times the temporal sampling interval. Since the digital waveguide simulation technique requires far less computational effort, it can be used to both accelerate and increase the accuracy of numerical simulations of acoustic media.
Qualitative and quantitative nonlinear dynamics of clarinet tones and multiphonics
Authors: Wilson Teresa D. , Keefe Douglas H.
Published: October 2005

Nonlinear dynamics offers a nontraditional but useful viewpoint from which to study tone production in the clarinet, and its applications have not been fully explored. A qualitative and quantitative analysis using nonlinear dynamics was done on pressure time series for single (monophonic) and multiphonic tones performed by a professional clarinetist. The pressure was measured by a piezoresistive pressure transducer inserted flush with the inner mouthpiece wall 4.5 cm from the tip. Phase portraits and Poincare sections were produced, and pressure spectra, correlation dimensions D, and Lyapunov exponents were calculated. The multiphonic spectra were biperiodic and phase-locked. For single tones D=1.0–1.1, and for multiphonics D=2.2–2.5. The largest exponent for both single tones and multiphonics was small and positive; for example, the information loss was 1 bit per 44 periods for the written note E3 and 1 bit per 68 periods for E5. The slightly positive Lyapunov exponent and the values D≳1 for single tones, and D≳2 for multiphonics, may be interpreted as the information loss due to slight fluctuations of a performer who maintains a steady tone. This result represents a significant difference between human performance and physical modeling of musical tone production.
Ab initio calculations for helium, acoustics, and metrology
Authors: Moldover Michael R.
Published: October 2005

Lossy, gas-filled resonators are now being developed at NIST to measure the viscous and thermal diffusivities of gases. If these resonators become as well understood as the low-loss spherical resonators already developed at NIST, the uncertainty in the measured viscosity of a dilute gas will become less than 0.1%, possibly limited by the difficulty of measuring the dimensions of a double-Helmholtz resonator (i.e., a Greenspan viscometer). The accuracy of the data from the acoustic viscometer will be tested by comparing experimental results for helium with the recent abinitio result from quantum mechanical calculations: η=(19.800±0.010) μPa s at 298.15 K. Similarly, the results for the Prandtl obtained from cylindrical acoustic resonators with inserts will be tested by comparison with the abinitio result: Pr=(Cpη/λM)=0.66419. Helium-based gas thermometry (both traditional and acoustic) will benefit from the theoretical results for the second virial coefficient of helium. Perhaps pressure measurements in the 1- to 10-MPa region could be improved by combining the abinitio results with highly accurate measurements of the dielectric constant of helium.
Recent progress and problems on study of forced standing solitons generated in Faraday wave experiment
Authors: Wei Rongjue
Published: October 2005

From the simple Faraday wave experiment with rectangular tanks of variable length and width, or with insection of partitions, the standing or nonpropagating solitons will manifest a number of interesting nonlinear phenomena. These include parameters governing generation, stability, collision dynamics, reflection symmetry, chaotic behaviors, etc., of one or more solitons. Some of the not well-solved problems of the physics and mathematical formulations will be presented. [A brief summary of the work by the Nonlinear Acoustics Group I of Nanjing, supported by Chinese Nonlinear Sc. Foundation.]
Capillary bridge stability in an acoustic standing wave: Linearized analysis of passive stabilization with radiation pressure
Authors: Marston Philip L.
Published: October 2005

A liquid bridge between two solid surfaces, known as a capillary bridge, has applications in low gravity such as the solidification of floating zones. Long bridges are naturally unstable to a symmetric mode where a region adjacent to one end bulges while the opposite end thins. For a cylindrical bridge of radius R and length L, the slenderness S=L/2R has a natural (Rayleigh) limit of π beyond which the bridge breaks. It is proposed here to stabilize dense bridges at a velocity antinode of a standing acoustic wave perpendicular to the bridge axis. Let 〈pr〉 denote the angular average of the radiation pressure over the surface of a cylindrical bridge. It is necessary to select the acoustic frequency such that 〈pr〉 increases with R so that a bulge is automatically squeezed by the increased radiation pressure. Linearized analysis of the stability indicates S may be extended beyond π: Smax depends on q=(R2/γ)d〈pr〉/dR, where γ is the surface tension and Smax diverges as q approaches unity. The analysis supports the possibility of passive acoustic stabilization of capillary breakup in low gravity. The one-dimensional inviscid slice approximation is used in the analysis of axisymmetric deformations. [Work supported by NASA.]
Nonlinear vibro-acoustic method for diagnostics of cracks in construction materials
Authors: Korotkov Aleksey S. , Sutin Alexander M.
Published: October 2005

New methods for the diagnostics of defects in objects made of construction materials, primarily of metals, are proposed. The basic concept of the proposed methods is simple: Materials containing defects have a much larger nonlinear response than materials with no defects. For materials with integrity, the nonlinear responses are up to several orders less as compared with the case of defected materials with defects. It is noteworthy to stress that these nonlinear effects are noticeable even at small strains far from a material damage threshold, thus making it rather attractive for nondestructive testing. The first experiments were performed employing samples shaped as rods made of steel used for fabricating parts of nuclear reactors. The samples were exposed to static stretching in order to introduce defects. Acoustic field modulation was measured by low-frequency vibrations and its increase (more than 30 dB) in stretched samples was observed. The nonlinear interaction of the impact-produced vibrations with the acoustic field in steel samples with a crack was investigated. It was shown that the modulation of sound by such vibration can be used for cracks detection. The method was also used to test a welded joint in a large pipe line for a nuclear power station.
Multichannel auditory perspectives, a historical view of Harvey Fletcher’s forgotten contributions and their ramifications
Authors: Ampel Frederick J. , Uzzle Ted
Published: October 2005

The history of sound transmission, recording and reproduction, and the number of channels those technologies may employ, is complex and convoluted. It has proceeded down numerous paths, and found many dead ends. Beginning with the work of Bell, Edison, and Clement Ader, the technical achievements and insights needed to produce successful and aurally accurate reproduction required much invention and enormous amounts of insight. How many channels? Sonic accuracy or artistic effect? Loudspeakers or headphones? Live or recorded? When Fletcher began his investigations in 1931, no one knew the answers. Regrettably, his significant contributions have been either lost to time or ignored. Without Fletcher much of what is known today about perception and sound would not have been possible. This paper will examine his contributions, remind one of the answers he found, show where they led, and bring them once again to the forefront.
Harvey Fletcher and musical acoustics
Authors: Strong William J. , Bassett Irvin G. , Hartmann William M.
Published: October 2005

Although the bulk of his work was concerned with various aspects of speech and hearing in communication, Harvey Fletcher had a longtime interest in musical acoustics. This interest is evidenced in his papers on perceptual aspects of musical tones, which stressed the complex interdependences of the percepts of loudness, pitch, and timbre on the physical parameters of intensity, frequency, and spectrum. However, his active involvement in musical acoustics research came to fruition only after he was released from other research, administrative, and teaching responsibilities. In conjunction with others, he explored perceptual aspects of piano, organ, violin, and percussion tones. His approach was that of analysis of natural tones, followed by synthesis of these tones based on the analysis results. Real and synthetic tones were presented to listeners who were asked to judge the tones as being real or synthetic. When listeners were unable to distinguish between the two, the synthetic tones were considered to contain all of the essential ingredients of the real tones. Fletcher’s papers in which this work was described will be reviewed and samples of his real and synthetic tones will be presented.
Estimating acoustic radiation from a Bernoulli–Euler beam using shaped polyvinylidene fluoride film
Authors: Scott Brian L. , Sommerfeldt Scott D.
Published: October 2005

A number of methods exist for determining far-field sound radiation from structures. Among such prediction techniques are purely analytical models and use of discrete sensors placed directly on the structure or in the surrounding fluid media. Analytical methods suffer from a lack of ability to model the structure completely and adapt to unforeseen system changes. Discrete sensors on the beam may require a large number of transducers to obtain an accurate estimate of the radiation and may also suffer from aliasing problems. Far-field sensors are often not suitable due to environmental constraints. An alternative method is the use of shaped distributed sensors on the structure, which act as low-pass filters in the wave-number domain. The use of this type of sensor helps to isolate the radiating portion of the wave-number spectrum and is also beneficial in reducing the number of sensors required to avoid aliasing. This work presents numerical results of using shaped polyvinylidene fluoride (PVDF) film to predict the far-field radiated sound. These results are compared to the theoretical results and to the results obtained when discrete sensors mounted to the structure are used.
Strategies for using strain sensing in active control of acoustic radiation
Authors: Masson Patrice , Berry Alain , Nicolas Jean
Published: October 2005

Sensing approaches used in active structural acoustic control (ASAC) are mainly concerned with monitoring acceleration, velocity or displacement of the structure, typically by means of accelerometers or PVDF, thereby eliminating the need for far-field acoustic sensor(s). The radiation of the structure is estimated from this information, either directly or from a model of the radiating structure. The direct approach has the advantage of not being dependent on the accuracy of any model. A new sensing strategy is herein presented, in both direct- and model-based approaches, where the estimation of acoustic radiation involves monitoring the strain field of the structure. Such information is directly given by fiber optics sensors, for example, so that significant gain is expected at this level. Two approaches are presented using strain information. The first formulation is obtained by integrating by parts the Rayleigh’s formula. Dependence on boundary conditions then appears and has to be dealt with. The second formulation utilizes a finite-difference scheme in order to estimate, from the strain information, the displacement field in Rayleigh’s formula. Simulations are performed using a given displacement field and the two formulations are compared in order to evaluate their effectiveness for use in active control schemes.
The Tait equation and its connection with B/A: An historical note
Authors: Beyer Robert T.
Published: October 2005

In the 1880s, the Scottish physicist P. G. Tait set up an empirical equation to fit pressure-volume data for fresh and salt water, gathered on a research expedition of the H. M. S. Challenger [‘‘Physics and Chemistry’’ of the VoyageofH. M. S. Challenger, Vol. II, part IV (1888)]. This equation, together with two or three variants of it, was the starting point of a number of researches over the next 70 years. In the 1950s, it was put to use in still another form, and became the ancestor of the quadratic relationship of pressure and density used in nonlinear acoustics. The history of this development and the connection between the Tait equation and the ratio B/A is set forth.
Nonlinear bubble oscillations and Bjerknes forces
Authors: Cordry Sean M. , Crum Lawrence A. , Roy Ronald A.
Published: October 2005

The acoustic levitation of bubbles in standing waves has been considered by many authors. Calculations of the equilibrium levitation position have followed the example of Eller [A. Eller, 170–171 (1968)] by considering linear radial pulsations whose amplitude is given by a linearized Rayleigh–Plesset equation. This procedure begins to fail as the bubble starts behaving in a nonlinear fashion. For bubbles experiencing nonlinear behavior, the radiation pressure (primary Bjerknes force) must be numerically calculated from the product of the instantaneous bubble volume and the pressure gradient of the sound field. Bubbles smaller than resonance size are normally attracted to the pressure antinode, but when nonlinear effects are considered, the bubbles can be repulsed by the pressure antinode for driving pressures above a certain threshold amplitude. Results of our calculations will be presented along with the implications for single bubble sonoluminescence. [Work supported by the office of Naval Research.]
Acoustic streaming at high Reynolds numbers in focused sound beams
Authors: Hamilton M. F. , Il’inskii Yu. A. , Zabolotskaya E. A.
Published: October 2005

In experiments reported recently on acoustic streaming in focused sound beams [Starritt etal., Ultrasound Med. Biol. 15, 363 (1989), and Matsuda etal., AdvancesinNonlinearAcoustics: 13thISNA, edited by H. Hobæk (World Scientific, Singapore, 1993), pp. 595–600], the Reynolds numbers for the streaming are of order 100. To model such experiments, nonlinearity in the momentum equation for the streaming velocity should be taken into account. Previous comparisons of theory with measurements of acoustic streaming in focused beams are based on linear equations for the streaming velocity, which are normally valid only for Stokes flows characterized by Reynolds numbers less than unity [Lighthill, J. Sound Vib. 61, 391 (1978)]. The numerical results presented here were obtained with nonlinear inertia terms for the streaming velocity retained in equations that describe the paraxial region of the beam. The primary wave is assumed to be a focused Gaussian beam, with parameters corresponding to the experiments cited above. Inclusion of nonlinearity yields predictions of streaming patterns that are more localized in the focal region, and in closer agreement with experiment, than predictions based on linearized equations for the flow. [Work supported by Schlumberger, NSF, and the Office of Naval Research.]
Theory and experiment of pulse propagation in shallow water
Authors: Zhang Renhe , Zhu Ye
Published: October 2005

An experiment was conducted in shallow water with strong thermocline, located between the depths from 11 to 15 m. Explosive sources were detonated at 7 and 25 m, with receivers also at 7 and 25 m. Band-limited signals with 1/3 oct bandwidth for different center frequencies and ranges were analyzed. The waveform structures are strongly dependent on source and receiver depths, center frequency, and range. A ray-mode theory including beam displacement was used to calculate the waveform structures and to invert for the bottom-loss versus grazing angle. The calculated waveform structures are consistent with the measured ones well.
Marine animal sound classification
Authors: Fristrup Kurt M. , Watkins William A.
Published: October 2005

Software was developed to measure characteristics of marine animal sounds (AcouStat). These measurements included aggregate bandwidth, duration, amplitude modulation, frequency modulation, center frequency, and interactions among some of these variables. These measurements proved effective for describing and classifying sounds in several contexts: identifying species, quantifying the repertoire of a single species, and identifying individuals. Our experience during development suggests that removal of noise energy and use of robust statistical measures are necessary to ensure repeatable results with open water recordings of marine mammal species.
Quantitative analysis of dolphin sounds
Authors: Tyack Peter L.
Published: October 2005

Most analyses of acoustic communication in animals lump sounds into qualitative categories. These are usually based upon aural impressions for human listeners or visual inspection of spectrograms. Quantitative analysis of acoustic features from beluga whale sounds raise serious questions about how discrete and robust the traditional categories of beluga calls are. Other categories, such as the contour of a dolphin whistle, use features that need not relate directly to absolute measure of time and frequency. Studies of vocal development and vocal imitation often benefit from a quantitative measure of similarity between sounds and putative models. Several different methods are compared to analyze whistle contours, including multivariate analysis of time-frequency features, dynamic time warping, and a signal compression approach. Ultimately, all such techniques need to be validated by studies of how each species perceives its own signals.
Vocal learning in Budgerigars (Melopsittacus undulatus) using food reward
Authors: Manabe Kazuchika , Dooling Robert J.
Published: October 2005

Budgerigars (parakeets) are small, highly social, Australian parrots capable of vocal learning throughout adulthood. These birds readily produce short (200 ms), whistled, frequency-modulated contact calls when separated from one another. In this experiment, birds were trained twice daily in 10 min sessions to produce or modify contact-call-like vocalizations using food reward. Calls were analyzed in real time using serial FFTs and each production was compared to a digitally stored ‘‘template.’’ Call productions which exceeded a predetermined criterion of similarity were rewarded, while those below criterion were not. Results show that budgerigars can learn to modify the intensity and spectro-temporal pattern of their species-typical calls within several days. Aside from human language, bird vocalizations have provided the only other clear example of learning in the acquisition and maintenance of a vocal repertoire. While song learning in birds has led to a number of important insights into the neurobiology of learning, such learning typically occurs over a time frame of months to years. The present results demonstrating call learning over a period of several days more closely parallel the time course of other more common forms of vertebrate learning. [Work supported by NIH Grants DC00198 and MH00982.]
Application of Green’s function modeling to ultrasonic probing of a planar interface
Authors: Hsu Nelson N.
Published: October 2005

The use of plane-wave ultrasound to probe interface properties based on angular spectrum analyses is common in the nondestructive testing of materials. Space-time domain Green’s function modeling is an alternative approach to frequency domain modeling. it is better suited for the implementation of short duration pulses, small aperture transducers, and time-resolved pulse-echo methods. However, a computation based on the Green’s function, though conceptually simple, is more involved than a computation based on the model of a plane wave of fixed frequency. Recently, an explicit Green’s function for layered media has been derived. Efficient computer programs have also been developed for cases which can be easily tested experimentally and have immediate applications. As examples, comparison results between theory and experiment are reported here for three test configurations: (1) a solid plate on a half-space with different interface conditions, with a point step-function source and a point detector located on top of the plate; (2) a liquid/solid interface, with both the point source and point detector in the liquid; and (3) a line focus transducer probing a liquid/solid interface. Practical applications to laser ultrasound, simulated acoustic emission, and the acoustic microscope are illustrated.
Laser ultrasonic monitoring of steel microstructure at elevated temperatures
Authors: Spicer James B.
Published: October 2005

Laser ultrasonics as a remote, noncontacting ultrasonic testing method has been used extensively for materials characterization. However, the unique character of the laser source has not been exploited fully. This work on steel at elevated temperatures has made use of relationships which exist for the thermoelastic laser source in monitoring microstructural changes in steel. Ultrasonic monitoring of microstructural evolution in solids is performed by making measurements of ultrasonic velocity and attenuation. At elevated temperatures, both the ultrasonic velocity and the attenuation are affected independently of the material microstructure. Thermal expansion of the sample complicates the determination of velocity from ultrasonic data since an independent measurement of sample length is needed. Contacting transducers allow only intermittent determination of velocity and attenuation since continuous contact might adversely affect either the transducer or the material. In this study, the laser-ultrasonic source characteristics are used to address these issues related to the testing of materials at elevated temperatures. Results obtained for the testing of austenitic and martensitic stainless steels to temperatures in excess of 1273 K indicate that characteristic microstructural changes may be detected by analysis of the laser ultrasonic data. This analysis permits real-time, continuous monitoring of microstructural evolution.
Determination of the elastic properties of composite plates using gas-coupled ultrasonics
Authors: Anderson Michael J. , Fortunko Christopher M. , Odom Edwin M.
Published: October 2005

A nonintrusive technique has been developed for measurement of the elastic moduli of reinforced polymer composite plates. Two ultrasonic transducers placed in a transmission configuration use air as the coupling medium to excite A0 Lamb waves in the plate sample. The phase speed of the plate waves at a given frequency is inferred from the angle of incidence for maximum transmission. Use of a low-impedance couplant gives several advantages beyond the nonintrusive nature of the technique. First, the influence of the gas medium is entirely decoupled from the determination of stiffness moduli. Second, a low-impedance couplant gives a high-quality factor, which enhances the potential precision of the technique. Gas coupled measurements of stiffness moduli on unidirectionally reinforced graphite/epoxy and glass/epoxy plates of thickness in the range ≊1–6 mm are presented. Plate waves were excited over the frequency range 100–200 kHz. Stiffness moduli E11, E22, G12, and Poisson’s ratio ν23 (fibers in the ‘‘l’’ direction) were obtained from the phase-speed/frequency data using least squares. Properties determined with the gas coupled technique are compared with static measurements, and with model predictions based upon the properties of the constituents and fiber-volume ratio.
Lamb wave measurements for rapid monitoring of sheet metal
Authors: Alers George A.
Published: October 2005

Lamb waves represent a very natural choice of interrogating energy for problems involving ultrasonic inspection of sheet and plate shaped materials. They have not enjoyed wide use in nondestructive evaluation because their excitation and detection by piezoelectric transducers require special mechanical supports and corrections for the acoustic loading of the sheet by the coupling medium must be made. By using properly designed electromagnetic acoustic transducers (EMATs), the transducer supports can be simplified, corrections for leaky waves can be eliminated, and very specific modes can be used to optimize a particular inspection process. Several examples of using special Lamb wave modes to inspect pipes and tubes in industrial environments will be presented, and their use for materials characterization in ferromagnetic metals will be emphasized.