bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-stage pulse tube refrigerator phase controlled by three rotary valves
Authors: Kodama T. , Tanaka M.
Published: October 2005

A two-stage pulse tube refrigerator equipped with three rotary valves has been constructed. One rotary valve controls the flow of the main gas flowing through the regenerators, and other two valves are used to modify the phase angle of the first and second stage through the room temperature side of the pulse tubes. The phase angles at the room temperature side of the first and second pulse tube relative to the main pressure oscillation can be changed independently. Besides the phase-angle dependence, the performance of the refrigerator was also investigated by changing the duration time connecting to the high- and low-pressure side of the main gas flow valve. When lead shots are used for the regenerative material at the second stage, the lowest temperature of 10.8 K was obtained. The experiments to optimize the working conditions are still on going and will be reported at the meeting.
A miniature pulse tube cooler for 80-K cooling
Authors: Kanao Ken-ichi , Watanabe Norihisa , Kanazawa Yoshiaki
Published: October 2005

A miniature pulse tube cooler for 80-K cooling has ben developed. In this paper the test results are reported [Kanao etal ., Cryogenics ICEC Suppl. 34, 167–170 (1994)]. The cooler is a simple orifice pulse tube type. It is based on a miniature split Stirling cooler. To reduce vibration, the compressor has a dual opposed piston driven by voice coil motors. In the case of 60-W/50-Hz ac input, generated pressure variation is 0.48 MPa peak-to-peak around 2.0 MPa. A regenerator and a pulse tube make up the ‘‘U‘‘-shaped cold finger. In the regenerator 1000 sheets of 400 mesh stainless screen are stacked. The diameter of the screen is 9.3 mm. Dimensions of the pulse tube are 4.4 mm in diameter and 55 mm in length. A reservoir is connected to the hot end of the pulse tube through a long capillary tube without any valves. Its volume is 100 cm3. The performances achieved are as follows: The lowest temperature is 69 K, and the cooling power is 400 mW at 80 K with 60 W input and 1 W at 80 K with 160 W input.
Numerical study of unsteady, thermally stratified flow in an idealized thermoacoustic stack
Authors: Worlikar Aniruddha S. , Knio Omar M. , Klein Rupert
Published: October 2005

A computational model for the simulation of unsteady, thermally stratified flow within an idealized thermoacoustic stack is developed. The model is based on a vorticity-based formulation of the low-Mach-number conservation equations. The numerical scheme combines fast Poisson solvers with domain decomposition/boundary Green’s-function techniques. The model is applied to analyze the response of the stack to imposed, finite-amplitude acoustic oscillations. Computed results are used to visualize the essential features of the vorticity field and temperature distribution, quantify the heat transfer between the gas and plates, and analyze thermal and mechanical energy losses. [The work of A.S.W. and O.M.K. is supported by the Office of Naval Research. R.K. is partially supported by Deutsche Forschungsgemeinschaft (DFG).]
Thermoacoustic onset as a critical transition
Authors: Smith Eric
Published: October 2005

It is noted that the processes of phase transition in equilibrium statistical mechanics and onset in thermoacoustic engines have the same mathematical features, and arise in the same way from the trace over a statistical density matrix. Onset differs physically in being a process of spontaneous breaking of time-translation symmetry, while equilibrium critical systems are by definition time independent. Heat engines thus represent a class of systems through which the concept of phase transition may be extended to include a limited range of classical dynamics.
The performance of an optimized thermoacoustic air conditioner
Authors: Minner Brian L. , Braun James E. , Mongeau Luc
Published: October 2005

Up to 25 thermoacoustic cooler design parameters were optimized to provide high COP predictions in selected air conditioning applications. Capacities ranging between 300 and 1500 W were considered. Two different configurations were investigated: (1) a single stack with a Helmholtz resonator termination, and (2) two drivers and two stacks. The optimization scheme utilized the Simplex algorithm, and the analysis was performed by DELTAE coupled with an original heat exchanger modeling tool which incorporated conventional straight fin analysis and semiempirical flow correlations. Various requirements were imposed for the external cooling and heat rejection temperatures, ranging between 270 and 287 K on the cold side and between 310 and 320 K on the hot side. Finned tube heat exchangers with water as the secondary fluid were considered. The predicted values of COP were greater than 3.8 (0.36, relative to the Carnot value) for an application analogous to a small window air conditioner. The performance and characteristics of the two different configurations were compared, and the loss distribution in each case was calculated. Furthermore, the impact of various constraints was examined. The performance predictions are encouraging and suggest that thermoacoustic air conditioning may be a viable proposition.
The impact of heat exchanger type on the design and performance of optimized thermoacoustic refrigerators
Authors: Minner Brian L. , Braun James E. , Mongeau Luc
Published: October 2005

A basic thermoacoustic cooler design was optimized with three different types of heat exchangers to obtain high COP predictions in a 200-W refrigeration application. The heat exchanger designs employed: (1) a parallel array of copper-alloy plates (conduction); (2) a single-pass, single row of finned tubes, with water/ethylene glycol mixtures as the secondary fluids (finned tube); and (3) a parallel array of infinitely conductive plates (ideal). The optimization scheme utilized the Simplex algorithm, and the analysis was performed by DELTAE coupled with an original heat exchanger modeling tool which incorporated conventional straight fin analysis and semiempirical flow correlations. The external cooling and heat rejection temperatures were fixed at 260 and 310 K, for which the Carnot COP is 5.2. The best COP’s resulting from the optimization of around 25 design parameters for each case were approximately 2.0 (conduction), 2.5 (finned tube), and 3.0 (ideal). In the finned tube device, the COP was limited by the cold exchanger secondary fluid properties. The use of a phase change secondary fluid, in conjunction with a heat pipe, for example, may further improve the performance of finned tube heat exchangers. The ideal case performance represents a probable upper limit for the configuration considered.
Torsionally resonant toroidal thermoacoustic refrigerator
Authors: Osborne Joseph W. , Garrett Steven
Published: October 2005

Current thermoacoustic refrigerator designs, based on linear actuation style moving-coil electrodynamic transducers (loudspeakers), are limited by their power-handling capacity. Loudspeakers introduce additional design constraints by the fact that they are required to simultaneously serve three separate functions: they must provide the electromotive force, the mechanically resonant elastic suspension, and a flexure seal (usually bellows). A fixed barrier within the toroidal resonator permits the excitation of a λ/2 standing wave when the entire toroid is driven into rigid-body torsional oscillation. The barrier eliminates the need for a flexure seal. The suspension (spokes) and the drive mechanism are external to the resonator. This increases the number of options available for the drive and resonant suspension and allows these functions to be optimized independently. The first TRT-TAR device, which did not include stacks and heat exchangers, generated predictable standing-wave gas resonances which were tuned to the first or second torsional resonances by adjustment of the gas mixture concentration. A complete, fully instrumented TRT-TAR, which includes a single stack and heat exchanger pair, has been fabricated and tested at low amplitudes [Work supported by the Office of Naval Research.]
High-power, high-efficiency drives for annular thermoacoustic refrigerators
Authors: Zhang David Chao , Maynard J. D.
Published: October 2005

In a typical thermoacoustic refrigerator, a reciprocating piston driver must be sealed to the acoustic resonator, requiring sliding seals or bellows which may be prone to failure. S. L. Garrett has proposed using an annular acoustic resonator with a rigid, sealed partition, with the acoustic excitation provided by oscillating the entire annular resonator about its axis. A problem arises in driving such a resonator, because now instead of driving only a piston, the entire resonator structure must be driven, and this requires high forces. High forces would result in high bearing wear for cam drives, and reciprocating electromagnetic drives at high-energy densities are limited by joule heating during stationary parts of the cycle. However, a very-high-energy density drive with low dissipation is possible using state-of-the-art permanent magnets and an electric motor; in an electric motor the rotor is in constant motion so that an induced back electromotive force limits joule heating and permits nearly 100% efficiency. In this paper a device employing these ideas for providing a very efficient reciprocating drive for an acoustic resonator will be presented. [Work sponsored by the Office of Naval Research.]
Vibrocentrifugal fluid pump
Authors: Chen Reh-lin , Garrett Steven
Published: October 2005

Centrifugal force has been used to create a large variety of pumps with pressure differentials which vary from inches of water (blowers) to more than 10 000 atmospheres (compressors). The centrifugal pumping pressure depends upon centripetal acceleration which is directly proportional to the square of the tangential velocity and inversely proportional to the rotational radius. Since the velocity dependence is quadratic, vibratory excitation will also lead to steady fluid flows. Experimental measurements of a vibrocentrifugal pump which is driven by a ‘‘clamped-free’’ bar undergoing resonant flexural vibration will be reported. Fluid flow is restricted to a flexible tube attached or internal to the oscillating bar. This process is extremely attractive for the self-pumping of heat transport liquids through the heat exchangers in a torsionally resonant toroidal thermoacoustic refrigerator. In that application, a single motor can be used to provide both the resonant excitation of the acoustic standing wave within the thermoacoustic refrigerator and eliminate the requirement for two separate motors to pump the hot and cold heat transport fluids. [Work supported by the Office of Naval Research.]
Detection and discrimination of spectral peaks by listeners with moderate to severe hearing losses
Authors: Nelson Peggy B. , Revoile Sally G.
Published: October 2005

Summers and Leek (1994) demonstrated that listeners with moderate hearing loss have a reduced ability to identify spectral peaks in broadband stimuli coincident with increased auditory filter bandwidths, but that abilities were presumed sufficient for vowel identification. The current study investigated spectral ripple detection and ripple frequency discrimination with listeners having moderate and severe losses. Stimuli were flat spectrum pure-tone complexes log-spaced over 2-oct bands (1000–4000 Hz and 500–2000 Hz). In one experiment the different signal’s spectrum was multiplied by sinusoidal log-spaced ripples. Ripple frequency was held constant while ripple amplitude adapted. In the second experiment, all signals contained constant-amplitude ripples with ripple frequency adapting. Preliminary results for moderate loss listeners indicate ripple detection thresholds for both 2-oct band stimuli are similar to those previously reported. Comparatively, listeners with flat severe losses have markedly poorer ability to detect spectral peaks, and performed significantly poorer for detecting ripples in the higher-frequency stimuli than in the lower-frequency stimuli. Results suggest that vowel distinctions based on formant discrimination may be difficult for these listeners. Also, deficient consonant identification may be associated with reduced ripple detection ability; the severely hard-of-hearing listener with the largest ripple threshold also had the poorest word identification. [Work supported by NIDCD Grant No. K0800124.]
Is impaired auditory temporal processing a cause of speech-language disorders? Negative evidence from psychoacoustic investigations
Authors: Watson Charles S. , Watson Betty U.
Published: October 2005

Psychoacoustic studies cast some doubt on the hypothesis that deficits in auditory temporal processing cause speech and language disorders. First, the temporal acuity of the auditory system so greatly exceeds that required by tasks considered to support this hypothesis [e.g., Tallal and Piercy, Nature241 , 468–469 (1973)] that disordered subjects would be quite unable to understand speech if their basic temporal processing were as imprecise as it is proposed to be. Second, in a study of 127 normal-hearing listeners, nonsense-syllable recognition was not correlated with temporal discrimination measured with various nonspeech stimuli, and the same result was later obtained for sentences, words and CV’s, although all speech measures load on a common factor. Third, structural-equation models were fitted to data collected from 24 college students with specific reading disabilities, and 70 who were ‘‘normal.’’ Data to be predicted included passage comprehension, word-attack skills, and word identification. A model using measures of speech perception and of intelligence yielded 0.7≳r2≳0.9, but these predictions were not improved by nonspeech measures of auditory temporal processing. A viable hypothesis is that sensory processing speed may be only indirectly related to some speech-language disabilities, but more directly related to intelligence. [Work supported by NIH/NIDCD.]
A handicapped listener’s articulation tests underwater
Authors: Fukuda Akiteru , Okada Heiji
Published: October 2005

There have been a number of papers in underwater sound propagation for a diver’s mutual communication. A healthy man’s monosyllable hearing test underwater has been reported previously. Now, a report of results on disabled (hard of hearing) listeners test is given. Sound propagation tests used a standard Japanese 25 m(L)×13 m(W)×1.5 m(D) waterpool. An underwater speaker Altec type UW-30 is used and is driven by a 10-W amplifier. A listener’s monosyllable test signal is used with a standard voice number (101) by an NHK announcer. The distances between the radiation speaker and the disabled listener are agreed upon at 5, 10, and 20 m, and depths are changed from 1.3 to ∼1.5 m. Radiator and listener’s depths are held at the same level through every test. Depth simulation used with the air chamber at 10 kg/cm2 normal air at Saitama Medical Univ., where pressures are controlled equivalent to 0-, 10-, 20-, and 30-m water depths. In the results of the articulation test, about the same scores are observed between the handicapped person and the healthy listener. Especially at the distance of 10-m, a handicapped person’s average score is greater than 4% compared with the healthy person’s score. Such a result requires further examinations.
Categorical perception of emotional speech
Authors: de Gelder Bea , Vroomen Jean
Published: October 2005

Emotions are communicated through the prosody of speech. Are such expressions perceived categorically or rather in a multidimensional space without clear foci? The former alternative is in line with longstanding views about the existence of some basic emotions. Recent reports present evidence that facial expressions are perceived categorically [de Gelder etal ., Cognit. Emotion (in press)]. To explore this issue for auditory speech, a continuum between happiness and fear was created by varying pitch excursion, pitch height, and duration of an utterance via PSOLA. Categoricity of perception for auditory expressions was examined in (a) an auditory-only presentation and (b) an auditory–visual condition of simultaneous presentation of the auditory stimuli and facial expressions corresponding to the either of the two expressions. In the auditory-only conditions a clear CP phenomenon is observed. In the bimodal conditions the visual information modulates the perception of the speech emotion. The latter phenomenon is not observed in a patient suffering from prosopagnosia. The findings raise the issue of a common biological basis for facial and vocal expression perception.
Phoneme detection in resyllabified words
Authors: Vroomen Jean , de Gelder Bea
Published: October 2005

There is evidence that the human listener takes, in continuous speech, the onset of a syllable as the onset of a spoken word [J. Vroomen and B. de Gelder, J. Exp. Psychol.: Human Percept. Performance (in press)]. However, this syllabic strategy would fail in resyllabified words like ‘‘my bike is,’’ pronounced as /mai bai kis/. In the present study, a phoneme monitoring task is used to investigate whether resyllabified phonemes are more difficult to detect than their nonresyllabified counterpart. The results show that (i) nonresyllabified phonemes can be detected faster than resyllabified phonemes, and (ii) that this effect is bigger for words that are not unique at their offset. This suggests that, in particular, late-unique resyllabified words should be more difficult to perceive, and it lends further credence to the idea that a syllable onset is taken as the onset of a word.
Estimation of nonsense syllable intelligibility
Authors: Rankovic Christine M.
Published: October 2005

An intelligibility estimation test comprising nonsense syllables that were recorded separately, and then concatenated, is under development for hearing aid assessment. Consonant-vowel-consonant syllables (CVCs) are presented along with a visual display on a computer monitor that identifies each syllable with an animated pointer as it is presented to the listener. After presentation of a list of 50–60 CVCs, the listener is asked to estimate the consonant percent-correct score. A major advantage of the test is rapid administration. Percent-correct estimates were collected from 16 normal-hearing subjects presented with CVCs masked by a speech-shaped noise and with high- and low-pass filtered CVCs. In all test conditions, actual percent-correct scores were obtained for comparison. In noise and under filtering, estimates are slightly higher than actual scores. However, estimates increase with speech-to-noise ratio (dB) at a rate of about 4% per dB, similar to the actual percent-correct scores. The crossover frequency derived from the filtering experiment was approximately 1700 Hz, nearly identical to that reported by French and Steinberg [J. Acoust. Soc. Am. 19, 90–119 (1947)]. Hence, articulation theory principles may be applicable. This test may serve as a speedy assessment tool for evaluating and selecting hearing aids. [Work supported by NIH.]
Application of frequency modulation technology to children
Authors: Franklin Barbara
Published: October 2005

Classrooms provide a poor acoustical environment for children who have a hearing loss. Frequency modulation (FM) systems can reduce the signal-to-noise problems of hearing aids by providing a constant sound pressure of the speaker’s voice. A new type of FM receiver combines the hearing aid and the FM system in a single behind-the-ear unit (BTE/FM). This new BTE/FM system eliminates the body-worn case as well as all loops and cords. A new product, which will shortly be introduced into the market, is an FM system, where all the components are contained in the ‘‘boot’’ which is then attached to the bottom of the hearing case. In this way, the hearing aid itself converts into an FM system. This paper will discuss this new technology and its contribution to children with a combined hearing and vision loss. [Work supported by OSERS.]
Study on detection of the electronic siren from an ambulance
Authors: Baba H. , Ebata M.
Published: October 2005

The electronic siren used on an ambulance is very loud in the street, but it is hard for the driver in an automobile to recognize it in many cases. It is conceivable that the reason is due to masking of the sounds inside and outside the automobile. In this paper, the detectable level of the electronic siren used on an ambulance was described and the reason why the thershold level of the siren is actually increased is discussed. As a result, conclusions were extracted as follows. (1) The threshold of the siren increases at the rate of 1.0–1.7 dB, when the level of music listened to in an automobile is increased by 2 dB in LAeq. This is considered to be caused by masking. (2) In an automobile running at medium speed, the detectable level of the siren increases by about 0.5 dB compared to the case of standstill. This is concerned with attention to driving.
Spatial surface convolution approximation of three-dimensional leaky wave contributions to high-frequency scattering
Authors: Marston Philip L.
Published: October 2005

A previous formulation of two-dimensional high-frequency scattering by smooth elastic objects is based on a one-dimensional convolution of a one-sided spatial response function with the local pressure of the incident wave evaluated at the surface of the object [P. L. Marston, J. Acoust. Soc. Am. 91, 34–41 (1995)]. That result is shown to follow from a more general three-dimensional formulation as an embedded special case. The new formulation expresses the local outgoing leaky wave amplitude as a surface convolution of the pressure of the incident wave with a two-dimensional response function. The formulation makes use of the local surface mechanics and wave properties but does not directly use thin-shell assumptions. Previous results are recovered for the leaky wave coupling coefficient and limiting phase for broadside illumination of a circular cylinder, the dimensions of elliptical coupling patches, and (from stationary phase) the coupling conditions for tilted cylinders. The formulation is useful for obtaining quick and simple backscattering strength estimates for objects with truncations where there are dominant leaky wave scattering contributions. It also describes the size of coupling regions on general smooth surfaces. [Work supported by the Office of Naval Research.]
Generalization of analytical numerical matching for structural acoustic scattering with discontinuities using a composite Green’s function approach
Authors: Loftman Rickard C. , Bliss Donald B.
Published: October 2005

Analytical numerical matching (ANM), when applied to structural acoustics, efficiently models structural discontinuities by superposing high-resolution local analytical solutions at discontinuities upon a low-resolution global numerical solution. This composite solution is very accurate and computationally efficient. Previously, ANM composite solutions have been developed for several specific problem geometries. A method for treating general constraint configurations using ANM is presented using the Green’s function concept, which models general structural constraints as an integration of point force solutions of the unconstrained structure. The general local solution is found by integration of the ANM local solution derived in the case of a point force. The point force local solution is analytic, known explicitly, and independent of overall geometry. The complementary global solution is far smoother than the original problem and, therefore, can be more efficiently calculated. In short, a general discretely constrained problem is replaced by a smoothed constrained problem, plus a local analytic correction. The method is demonstrated by application to scattering from an infinitely long cylindrical shell with periodic bulkheads. Accuracy and convergence of the structural response and scattered pressure are compared using a classical modal solution, a previous ANM modal solution, and the present general method. [Work supported by ONR.]
Active classification of submerged shells insonified by dolphin ‘‘clicks.’’
Authors: Gaunaurd G. C. , Brill D. , Huang H. , Moore P. W. B. , Strifors H. C.
Published: October 2005

Many echoes returned by various submerged shells when they are insonified by dolphin echolocation clicks have been examined. The details of the experimental tests the database collected have been described elsewhere. The signal processing analysis of the returned signatures attempted to understand how the animal performed his amazing target classification feats. The echoes were examined in the time, the frequency, and the joint time–frequency domains, and it has precisely been shown how specific features observable in these domains are directly related to the physical characteristics of the shells. The processing capitalizes on certain basic resonance features contained in the echoes, and from them it determines the size, shape, wall thickness, and the material composition of the shell and its filler substance. In the same way that these features give us the identifying characteristics of the targets with hardly any calculation required, it is believed that they also give them to the dolphin. This may explain the secret of their unique success. Emphasized here are features in the combined time–frequency domain, extracted by a variety of Wigner-type distributions belonging to the bilinear (or Cohen) class. The automation of the processing does not seem to be beyond present capabilities.
Scattering of sound by two concentric free-flooded cylindrical shells
Authors: Kim K. Steven
Published: October 2005

Scattered acoustic pressure fields are obtained when two concentric free-flooded cylindrical shells of finite lengths are subjected to plane waves incident obliquely to the axis of the cylindrical shells. Integral equations are formulated for the elastic thin shells with simply supported boundary conditions at both ends. Near- and far-field acoustic pressures of the scattered sound are calculated. Effects of acoustic coupling between two shells on scattering of sound are studied.
Response of thin semi-infinite cylindrical elastic shell to axisymmetric impulsive radial excitation
Authors: Mapes Theodore J.
Published: October 2005

The transient response of a semi-infinite, thin cylindrical elastic shell to an impulsive, axisymmetric radial excitation applied at the origin is investigated in the time and frequency domains using Fourier and Laplace transform methods. Solutions for the radial and axial displacements as functions of time and axial position show the dispersive nature of the wave propagation. High-frequency components propagating at the plate wave speed are followed by slower components occurring near the shell ring frequency. The temporal variation of the spectral components of the transient displacement is examined using a joint time–frequency distribution function. Analytical results are confirmed by experimental measurements on a brass tube.
Acoustic signature simulation of a composite armor vehicle using boundary element methods
Authors: Wu Z. , Raveendra S. T. , Shalis E.
Published: October 2005

Acoustic signatures of ground combat vehicles are very important to their survivability. In the low-frequency range of 10–200 Hz, the structure-borne acoustic radiation is mainly due to the track force/moment inputs. Full-vehicle models were developed to numerically simulate the radiated acoustic signature as well as the interior noise levels of a new composite combat vehicle at its design stage. Boundary-element method was used to compute the radiated sound pressure in the semianechoic condition after mapping normal vibration velocities (calculated from a finite-element model) onto the vehicle’s surfaces [Z. Wu and E. Shalis, ‘‘Acoustic signature prediction of combat vehicle using finite and boundary element methods,’’ SPIE’s 1996 Symposium on Smart Structures and Materials, 26–29 Feb. 1996, San Diego, CA]. The numerical computation is quite intensive since a large number of frequency points is required. A matrix interpolation procedure was used where the actual number of frequency loops are reduced substantially. It is done by initially computing the solution matrices at prescribed key frequencies and then computing the matrices at the intermediate frequencies using a quadratic interpolation. [This work was partially funded by a U.S. Army SBIR contract granted to Automated Analysis Corp.]
Adaptation of a frequency domain structural acoustics finite element code to test the doubly asymptotic approximation
Authors: Ginsberg Jerry H. , Allik Henno
Published: October 2005

The doubly asymptotic approximation is widely employed to model the transient (time domain) response of structures that are partially or fully immersed in water. It replaces the field equations for the fluid with an ad hoc surface interaction law that was identified from analytical solutions for spheres and infinitely long cylinders. Previously, the validity of the method for slender hemi-capped cylindrical shells was investigated by comparing DAA in the frequency domain to the surface variational principle, and then using FFT theory to obtain alternative transient responses. That study was limited by its use of Ritz series for displacement. The present work describes how SARA-2D, which is a frequency domain structural acoustics computer code, may be employed to assess the validity of DAA. SARA-2D uses finite elements for the structure, while finite and infinite elements model the fluid. Because of the narrow bandwidth of its matrices, it is more efficient than boundary elements for a frequency sweep. However, internalization of the wet surface nodes within the finite element mesh, the nonlocal nature of DAA, and the need to construct an added mass matrix for DAA lead to interesting issues in deriving an equivalent DAA model. [Work supported by ONR, Code 1222.]
Application of finite element analysis and analytical numerical matching to scattering from fluid-loaded structures with discontinuities
Authors: Park Christopher D. , Loftman Rickard C. , Franzoni Linda P. , Bliss Donald B.
Published: October 2005

Analytical numerical matching (ANM) is an analysis method that separates problems into high-resolution local and low-resolution global solutions. A method is presented to treat discontinuities, such as structural attachments, within the ANM local solution by high-resolution solid modeling using finite element analysis. The global problem, which is subjected only to smooth distributed forces, can then be solved by lower order methods, such as shell theory. Both the local and global solutions are more easily solved than the original problem, and the resulting composite solution is very computationally efficient. The approach is a novel way to embed local highly refined solutions within a broader problem. The method is illustrated by several sample problems including a vibrating beam with constraints, and acoustic scattering from a fluid loaded shell.
The splitting of dispersion curves for the fluid loaded plate
Authors: Dickey J. , Maidanik G. , Uberall H.
Published: October 2005

The splitting of the free-wave dispersion curve for a fluid-loaded plate into sub- and supersonic branches and the apparent ‘‘repulsion‘‘ of these two branches are commonly observed. A simple model of the fluid-loaded plate indicates that this splitting must occur. A framework is offered from which to investigate the sensitivity of the details of the dispersion curve in this spectral range. The influence of the simplifying assumptions on the behavior of the dispersions in this spectral range and the development of more complete models are discussed and cited.
Inferring the effects of curvature of tubulars from pulse propagation tests
Authors: Rama Rao V. N. , Morgan Dale F. , Vandiver J. Kim
Published: October 2005

Drilling tubulars typically function under large static and dynamic axial loads. The axial load causes curvature in the tubing and when loads are excessive, sections of tubing are forced in contact with the borehole wall. This causes excessive wear and fatigue and leads to failure of the tubing. The feasibility of inferring the incidence of curvature in the tubing and the increase in the attenuation level due to wall contact was investigated with pulse propagation tests on sections of drill tubing. Propagation speed and attenuation as a function of frequency were estimated from impulse response data using a nonlinear least-squares inversion technique. The changes in dispersion of phase speed and attenuation levels were used to identify changes in wall contact condition. Further, attenuation levels were also used to identify the presence of tubing curvature through the resultant coupling between axial and bending waves.
Crack detection in simple and complex beamlike structures
Authors: Arzoumanian Sevag H. , Swanson David C.
Published: October 2005

A technique, inspired by Skudrzyk’s mean value theory, for determining the severity of single cracks in uniform beams having arbitrary intermediate and boundary conditions is presented. It is based on a weighted average of eigenfrequency shifts of higher-order modes—modes 2 and higher—and does not require knowledge of the details of the structure. Starting from an analysis of a uniform beam with a midspan crack, a closed-form expression—valid for all ranges of crack compliance— for the eigenfrequency shifts of higher-order modes was obtained. It was shown that the mode averaged eigenfrequency shifts for arbitrarily located cracks on uniform beams are given by this same analytical expression and are, hence, independent of crack location. Finally, Skudrzyk’s mean value theory was invoked to extend this approach to truly complex beam assemblies. It was shown that the mode averaged response of complex beams is reasonably close to that of their equivalent simple structures thereby making the use of deterministic models in determining the magnitude of cracks unnecessary. [Work supported by ONR.]
Broadband method and apparatus for precise measurement of complex shear modulus of viscoelastic materials
Authors: Sheiba L.
Published: October 2005

This method is based on the inverse solution to the vibration problem of a finite elastic cylinder with reinforced torsional surfaces by rigid septa or plates. In all cases the polymer layer to be tested is bonded to rigid plates; therefore, the radial displacement is zero at the boundary between the polymer layer and the septum. The admittance matrix Y of the element is constructed within the framework of the hypothesis for planar cross sections. The dimensionless shear wave number kt(ω)h, which is the unknown variable, is obtained by measuring the transfer matrix of a known structure and as a result of solving the transcendental equation in a designated frequency range. Data are attained over a broadband of frequencies and temperatures without dependence on the time–temperature superposition principle.
Distinguishing multiple prosodic boundaries in articulatory kinematics and dynamics
Authors: Byrd Dani , Saltzman Elliot
Published: October 2005

Recent work has demonstrated that temporal lengthening of articulatory gestures adjacent to an intonational phrase boundary likely results from a lower underlying gestural stiffness. Magnetometer data from one subject (two more to be added) was examined to determine whether multiple levels of prosodic boundaries are distinguished in the spatiotemporal patterning of articulation. Eighty tokens were recorded of a /CVCV♯CVCV/ sequence with five differing boundary conditions: (a) none, (b) a simple word boundary, (c) a boundary between elements in a list, (d) a vocative name boundary, and (e) an utterance boundary. The magnitude and duration of each consonantal closing and opening gesture, and the temporal latency between consonants were determined. Three statistically differentiated levels of interconsonant latency were found in the /CV♯CV/ portion of the utterance—e,d≳c≳a,b—that results from differences in post-boundary closing durations. Lengthening of preboundary opening movements also occurs for the three largest boundaries—e,d,c≳a,b. All gestural duration increases are accompanied by longer mean times to peak velocity indicating lower gestural stiffnesses. Additionally, the boundary−adjacent opening gestures are spatially larger before the three largest boundaries—e,d,c≳a,b. Both spatial and temporal boundary effects on articulation will be described in a dynamical model. [Work supported by NIH.]
Is Tone Sandhi Group part of the prosodic hierarchy in Taiwanese?
Authors: Hsu Chai-Shune , Jun Sun-Ah
Published: October 2005

Recently, it has been shown that segments are phonetically strengthened at the beginning of prosodic units [Jun (1993) (for Korean); Fougeron and Keating (1995) (for English); Fougeron (1996) (for French)]. This study investigates whether the syntactically defined Tone Sandhi Group (TSG) in Taiwanese is part of the prosodic hierarchy based on the pattern of phonetic strengthening. VOT and closure duration of word initial /ph/ are compared in five prosodic conditions, varying in the position within the intonational phrase (IP) and TSG. Preliminary results show that VOT and closure duration of /ph/ are longer IP-initially than IP-medially. Furthermore, VOT, but not closure duration, is consistently longer TSG-initially. Interestingly, both VOT and closure are shorter TSG-finally: Final weakening marks the TSG boundary, just as initial strengthening marks the IP boundary, suggesting that TSG is a prosodic unit. However, incorporating TSG into the prosodic hierarchy is problematic for the strict layer hypothesis, which states that a lower-level prosodic unit is exhaustively contained within a higher level prosodic unit. An alternative is to assume that phonetics may mark both nonprosodic (TSG) and prosodic (IP) boundaries. [Work supported by NSF.]
Downstep, regressive upstep, H raising, or what?—Sorting out the phonetic mechanisms of a set of ‘‘phonological’’ phenomena
Authors: Xu Yi , Kim Jiyeon
Published: October 2005

For a long time, downstep and H raising have been considered to be two of the phonological processes that are partially responsible for generating the surfaceF 0 contours in languages. Downstep refers to the lowering of the second H relative to the first one in a tone sequence of HLH. H raising refers to the raising of the H in an HL sequence. Recently, Laniran and Clements suggest that, in Yorùbá, both phenomena may be viewed as the consequences of regressive upstep, a process by which an L raises an H that occurs earlier [Y. O. Laniran and G. N. Clements, Proc. 13th ICPhSc, Stockholm, Vol. 2, pp. 734–737 (1995)]. Meanwhile, a series of studies on contextual tonal variations in Mandarin and Thai reveals phenomena also reminiscent of downstep and H raising. Due to the nature of the tones in those languages, however, explanations in terms of phonetic mechanisms seemed to emerge. The present paper reports a study that examines both local and long distance contextual tonal variations in Mandarin. It is argued, based on data found in this study, that there are actually two phonetic mechanisms underneath all these phenomena: carryover assimilation and anticipatory dissimilation.
Perceptual parsing of coarticulated F0 information in speech
Authors: Pardo Jennifer S. , Fowler Carol A.
Published: October 2005

Coarticulatory acoustic variation is presumed to be caused by temporally overlapping linguistically significant gestures of the vocal tract. The complex acoustic consequences of such gestures can specify them without recourse to context-sensitive representations of phonetic segments. When the consequences of separate gestures converge on a common acoustic dimension, as during coarticulation, perceptual parsing of overlapping spoken gestures, rather than associations of acoustic features, is required to resolve the distinct gestural events. Direct tests of this theory were conducted in which mutual influences of (1) fundamental frequency during a vowel on prior consonant perception and (2) consonant identity on following vowel stress and pitch perception were found. The results of these converging tests lead to the conclusion that speech perception involves a process in which coarticulated segments are parsed from the acoustic stream of speech along gestural lines.
Contributions of auditory feedback frequency components on F0 fluctuations
Authors: Kawahara Hideki , Aikawa Kiyoaki
Published: October 2005

Auditory feedback effects on voice F0 control were investigated in terms of the frequency range of feedback harmonic components. The analysis was based on data obtained by a new experimental auditory feedback method called TAF (transformed auditory feedback). This method replaces a natural side tone path with an artificial path which modifies the parameters of the feedback speech sounds in real time, and measures effects in the speech sounds produced [Kawahara and Williams, Vocal Fold Physiology Symposium (1995)]. A series of TAF experiments using sustained vowel phonations with band limitations using high-pass and low-pass filters was conducted. Estimated impulse responses from pitch perception to voice F0 control illustrated that the response is compensatory and can be decomposed into two second-order responses with an initial delay. The results indicated that high-pass filtering does not show significant effects on response parameters while low-pass filtering shows a negative correlation between the cutoff frequency and the response delay. The average response delays for high-pass filtering and low-pass filtering were equivalent for a 800-Hz cutoff frequency. Implications on voice pitch perception will be discussed.
Acoustic–phonetic realizations of focus in discourse and their perceptual correlates in Korean and Japanese
Authors: Choi Young-Sook , Sato Shigeru , Min Guang-Jun
Published: October 2005

In order to look for acoustic–phonetic reflections of focus in discourse, speech of Korean and Japanese was analyzed, followed by a perception experiment ensuring that, to locate the focus, a sufficient range of F0 change must exist in the focused phrase. The following findings are drawn from phonetic observations and the perception experiment. (1) In both Korean and Japanese the focus is realized by the difference in F0 in the syllables in the focused phrase rather than by its local maximum. Without a lexically preassigned pitch accent, the focus in Korean emphasizes the difference in the rise in pitch in the first two syllables of the phrase in focus. Japanese, on the contrary, makes use of the inherent accentual pattern of the phrase, resulting in comparatively higher F0 of the accented syllable. (2) The differences in intensity between focused and unfocused phrases are not significant, whereas the overall significance of the differences in pitch change is maintained both in Korean and Japanese; there is a tendency in Korean toward larger variational ranges than in Japanese. (3) Duration is longer for the focused phrase than for the unfocused; Korean shows more prominent lengthening of the focused phrase than Japanese. (4) According to the perception experiment, duration and intensity are not utilized to locate the focus in discourse; in spite of longer duration and stronger intensity, focus is not perceived without a sufficient change of F0.
Pitch discrimination during breathy phonation
Authors: Silverman Daniel
Published: October 2005

Just-noticeable differences (jnd’s) for frequency of complex waves with stable F0 are 0.3–0.5 Hz [Flanagan and Salow (1958)]. However, there are both articulatory and acoustic reasons to believe that jnd’s are greater during breathy phonation than during modal phonation. This study investigated pitch discrimination during breathy phonation by manipulating acoustic parameters. Both breathy vowels and modal vowels from Mazatec were digitized. Intensity was equalized, and F0 was manipulated by 0.2-Hz increments employing the OCEAN Speech Processing Program, while all other acoustic parameters were held constant. Subjects listened to pairs of these stimuli and judged whether they were the same or different. It is predicted that jnd’s would be greater during breathy phonation than during modal phonation. Results will be discussed with reference to laryngeal timing patterns in vowels in Mazatec and elsewhere. In Mazatec, tone and breathy phonation are sequenced with respect to each other on a single vowel. In languages that possess phonation contrasts without tonal contrasts [e.g., Gujarati: Fischer-Jorgensen (1971)], no sequencing is observed: breathiness pervades the vowel. It is likely that pitch discrimination plays a contributing role in such timing distinctions between Mazatec-type languages and Gujarati-type languages: Pitch is likely to be less discriminable during breathy phonation.
The intonational structure of Chickasaw
Authors: Gordon Matthew K.
Published: October 2005

Relatively little instrumental work has been done on the intonational structure of American Indian languages. This study investigates the intonation of Chickasaw, an American Indian language belonging to the Muskogean family, following Pierrehumbert’s [The Phonology and Phonetics of EnglishIntonation (MIT, Cambridge, MA, 1980)] intonation framework. Preliminary results suggest certain interesting intonational features in Chickasaw. Declarative intonational phrases with neutral subject–object–verb word order are marked with a high boundary tone, whereas interrogative intonational phrases are signaled with a low boundary tone. In both types of phrases, a high nuclear pitch accent docks onto the right-most heavy syllable in the verb, where heavy is equivalent to CVV, CVC, or CV in a metrically prominent position. Data also show that an intonational phrase in Chickasaw consists of one or more accentual phrases. Accentual phrases consisting of a single word begin with a low tone, and receive a high tone both on the second syllable and the final syllable of the phrase: LHH pattern. The initial low tone of the accentual phrase is typically not realized in words with fewer than three syllables. Accentual phrases consisting of more than one word and the effect of focus on intonation will also be considered.
Rhythm and intonational phrase structure influences on the placement of pitch accents within words in American English utterances
Authors: Dilley Laura C. , Shattuck-Hufnagel Stefanie
Published: October 2005

Many cases of apparent ‘stress shift’ in American English, e.g., ‘‘MAssachusetts MIRacle,’’ show early pitch accent within the word, influenced both by pitch accent clash with the following word, and by prosodic constituent structure: The first pitch accent in a new intermediate intonational phrase occurs as early in the word as possible (Beckman and Edwards, 1994; Shattuck-Hufnagel etal ., 1994). The lexical stress pattern of the word also plays a role: Words with alternating stress (e.g., Massachusetts, absolutely) behave quite regularly, but words with adjacent full-vowel syllables (e.g., maintain, unlikely) are more variable (Shattuck-Hufnagel, 1995). One possible account of this irregularity is that adjacent-stress words challenge the prevalent patterns of rhythmic alternation in American English. In this study, the effects of both word-level and phrase-level rhythmic context on the pitch accent behavior of words with these two stress patterns are explored, in a large corpus of FM radio news speech [M. Beckman and J. Edwards, in Phonological Structure and Phonetic Form: Papers in LaboratoryPhonology III (1994); Shattuck-Hufnagel et al., J. Phon. 22, 357–388 (1994); Shattuck-Hufnagel, in Proceedings of the International Congress of thePhonetic Sciences (1995)]. [Work supported by NIH Grant R01-DC-02125 and NSF Grant IRI 9314967.]