bluuebunny/crossref_metadata_2025 huggingface dataset:
The measurement of absorption coefficient and acoustic impedance using spherical waves and a transfer function method
Authors: Nobile Matthew A.
Published: October 2005

The normal-incidence absorption coefficient (or complex impedance) of an acoustical material is usually measured in a standing wave tube using plane wave excitation. In order to obtain valid high-frequency data, a tube with a small cross section is required. But, quite often, the absorptive properties of the small sample of material that is tested are not representative of those of the larger sample from which it has been taken. An engineering method has been described [M. A. Nobile, Proc. NOISE-CON '87, Penn State University, 8–10 June 1987, pp. 611–616] that shows that large samples of materials (or outdoor ground surfaces) can be evaluated using spherical waves in a hemi-anechoic environment. As with the standing-wave tube method (per ASTM E-1050), this new method utilizes random noise excitation and computes the transfer function between two closely spaced microphones. The accuracy is limited primarily by diffraction from the edges of the finite sample, which is not taken into account. This paper will address the theoretical aspects of the problem and present some recent experimental results.
Nonlinear compressibility corrections to induced hydrodynamic mass: Consequences for small amplitude supersonic modes
Authors: Putterman S. , Roberts P. H. , Fiszdon W.
Published: October 2005

The induced mass of an object accelerating through an isotropic fluid has contributions due to the fluid's compressibility that are anisotropic and nonlinear in the velocity. This effect can lead to pronounced amplitude dependence in the resonant frequency of supersonic modes. One such example to be presented involves the plasma wave that propagates in 2-D arrays of ions in He4 with a velocity that is ten times the He4 sound velocity. [Work of S. P. supported by DOE and work of P.H.R. supported by ONR.]
Nonlinearity parameters for superfluid helium
Authors: Cramer M. S. , Sen R.
Published: October 2005

The nonlinear propagation of second-sound in He II near one of the zeros of the quadratic steepening parameter associated with the B/A ratio is considered. It is shown that the correct description at these pressures and temperatures requires an additional nonlinearity parameter. New expressions for the nonlinear sound and shock speed are given and compared to experiment.
Refraction of finite amplitude acoustic waves at a plane fluid-fluid interface
Authors: Cotaras Frederick D. , Blackstock David T.
Published: October 2005

One of the oldest and most venerable laws of acoustics is Snell's law. But does this law hold for finite amplitude sound? By following the path of a wavelet (point on a waveform), the following form of Snell's law for a finite amplitude wave is derived: sin θt/sin θi = (c2 + β2ut)/(c1 + β1ui), where θ, c, β, and u are angle, small-signal sound speed, nonlinearity coefficient, and particle velocity, respectively. Subscripts i, t, 1, and 2 denote incident wave, transmitted wave, fluid 1, and fluid 2, respectively. Since θ1, is predicted to vary from wavelet to wavelet, the transmitted wave field cannot be truly planar. However, by following the path of individual wavelets, the waveform of the transmitted signal is computed at any point in the field. [Work supported by ONR.]
Training new fricative contrasts
Authors: Jamieson Donald G. , Morosan David , Rvachew Susan
Published: October 2005

A perceptual fading technique [cf. Jamieson and Morosan, Percept. Psychophys. 40, 205–215 (1986)] was used to train two types of listeners to perceive new fricative contrasts. One group consisted of young adult francophones who had difficulty producing and perceiving the voiced/ voiceless “th” distinction in English. With this group, training using the fading technique improved identification accuracy both for the specific, synthetic targets used in training, and for multiple, natural tokens of these sounds, spoken by different individuals, both men and women. However, this learning was quite specific, as performance was poor when listeners were tested with the target sounds in new word positions, or when /d/ tokens were used in the distractor set. The second group of listeners were young children who consistently mispronounced at least one English fricative sound, and had been diagnosed as having a functional articulation disorder. A sizeable proportion of these children, all of whom had been selected on the basis of production difficulties, displayed atypical perceptual skills; for these children, training produced a measureable improvement in identification accuracy, and in some instances, perceptual training (without explicit production training) also improved the productions of the target sounds. [Work supported by NSERC AHFMR and HWC:NHRDP.]
Computation of the Biot coefficients
Authors: Yavari B. , Bedford A.
Published: October 2005

To apply the Biot theory to the study of the interaction of acoustic waves with ocean sediments, the coefficients in the equations must be evaluated. The coefficients depend on the frequency and the fabric, or microstructure, of the sediments. A method for evaluating the drag and virtual mass coefficients has recently been developed [A. Bedford et al., J. Acoust. Soc. Am. 76, 1804–1809 (1984)]. The method requires solving for the motion of the fluid in the pores when the solid constituent is subjected to a spatially uniform, oscillatory motion. The finite element method has been used to determine the fluid motion. The drag and virtual mass coefficients have been determined for a variety of two-dimensional pore geometries. It was found that the drag coefficient is insensitive to the pore geometry, while the virtual mass coefficient is very sensitive to the pore geometry. It was determined that the coefficients are independent of the frequency up to a characteristic value of dimensionless frequency and exhibit a bilinear dependence on frequency. [Work supported by ONR.]
The effects of seabed interaction on air-to-water sound transmission
Authors: Chapman David M. F.
Published: October 2005

The presence of a reflecting seabed alters the transmission of sound from an air-borne source to a water-borne receiver. Resonances in a plane-wave transmission coefficient correspond to excitation of the acoustic normal modes in the water layer. Although the air-borne source excites the same normal modes as a water-borne source, the amplitude and phase of the excitation coefficients are different. There are some notable effects: the weak dependence of transmission loss upon source height, the preferred excitation of high-order modes, and the 25 log R dependence of transmission loss upon range in the mode-stripping regime. The predictions of a simple normal-mode transmission loss model are presented, including realistic absorption in the air and at the seabed. [Work supported by the U.K. Ministry of Defence, through the Royal Aircraft Establishment at Farnborough.
Bottom interacting pulse propagation in the ocean
Authors: Collins Michael D.
Published: October 2005

The parabolic equation method was first applied to underwater sound propagation by F. D. Tappert. It has since been refined and benchmarked into a valuable tool for frequency domain calculations. Development of an equivalent nonlinear method in the time domain was initiated by B. E. McDonald and W. A. Kuperman. A linear version of this method has been developed to handle bottom interaction. The new model allows density and loss to be functions of depth. Loss is accounted for in the proper manner for typical ocean sediments. Loss per meter increases linearly with frequency. A new initial field has been derived using the method of matched asymptotics. Numerical methods suited to linear acoustics have been implemented. The method has been benchmarked by convolving an impulse response obtained by it into a cw response and comparing with normal mode results. [Work supported by ONR.]
Modeling depth-dependent absorption in marine sediments
Authors: Ogushwitz Paul R.
Published: October 2005

Biot model estimates of absorption are particularly sensitive to porosity and to the frame moduli. In previous work [P. R. Ogushwitz, J. Acoust. Soc. Am. 77, 429–464 (1985)], the frame moduli from a self-consistent theory of composites (SCT) was estimated, and an empirical factor (the “contact factor”) that scales the SCT estimates in order to match measured wave speeds was determined. It is shown that the contact factor is related to grain packing and cementation. Here, it is first shown that Biot model estimates of sound speed versus depth do agree with measurements in Gulf Coast brine sands [G. H. F. Gardner et al., Geophysics 39, 770–780 (1974)], where the SCT estimates have been scaled by the appropriate contact factor. Second, it is shown that the corresponding Biot estimates of absorption versus depth are within the range of measured absorption values, that they exhibit a maximum at 1750-m depth, and that the behavior of this maximum is consistent with other published measurements and theories. Third, Biot estimates of shear wave absorption are presented. Finally, a physical model for the contact factor is presented.
High temporal resolution observations of high-frequency acoustic bottom echoes
Authors: Clarke Thomas L. , Proni John R. , Huff Lloyd
Published: October 2005

Acoustic bottom echoes at frequencies from 10 to 380 kHz were recorded for a variety of bottom types in southern Chesapeake Bay. Short pulse lengths and direct digital recording allowed temporal resolution of 100μs to be achieved. Supporting measurements of sediment characteristics and bottom roughness allowed comparison of the measurements with theory. The field observations were in good agreement with the theory after corrections for the interaction of transducer beam patterns with bottom roughness were made.
Characterization of seafloor type and roughness from 12-kHz acoustic backscattering measurements
Authors: de Moustier C. , Alexandrou D.
Published: October 2005

Seafloor acoustic backscatter measurements were carried out with 12-kHz sea beam multibeam echo-sounders over a variety of terrains including pelagic sediments on the top of two seamounts in the tropical North Pacific; hemipelagic sediments, lava flows, and debris flows on the East rift zone of the Kilauea volcano; and a manganese nodule field in the tropical Northeastern Pacific. These data are subjected to statistical tests for homogeneity and stationarity, and sidelobe interference cancellation is performed through adaptive filtering. These measurements are then used to compare the 12-kHz acoustic signature of these terrains based on statistics of the amplitude and the phase of the echoes received at discrete angles of incidence in the interval ±20°. Implications for bottom type identification as well as surface roughness determination are discussed. [Research funded by ONR.]
Acoustic investigation of Paleo-drainage networks in central Chesapeake Bay
Authors: Halka Jeffrey , Gardner D. L.
Published: October 2005

Located west of the deep axial channel in the central Chesapeake Bay is a featureless, gently sloping platform bounded by the 8- and 16-m depth contours. Sediments on this platform consist almost entirely of muds accumulated during the Holocene rise in sea level. This area has been extensively surveyed using 5- and 27-kHz seismic reflection profiling equipment. While generally revealing only minor reflectors in the muds which overlie the pre-Holocene erosion surface, certain areas consisted of acoustically impenetrable sediments. X rays of cores collected from these areas showed numerous gas-filled voids in the sediment. Stream channel margins are evident on the pre-Holocene erosion surface, and the gaseous zones are confined between these margins, although the bottom of the channels cannot be observed due to the acoustic impenetrability. The gas zones are traceable and form an interconnected network, one of which connects to a present day upland stream.
A comparison of measured backscatter strengths with the first- and second-order terms of a Neumann series solution to the Helmholtz scattering integral
Authors: Keiffer Richard , Werby M. F. , Stanic Steve
Published: October 2005

In previous ASA meetings, a rough interface scattering model under development at NORDA has been reported. This model makes use of Brekhovskikh's tangent plane approximation for the total field near the scattering surface in the Helmholtz integral equation. Direct numerical integration is then performed yielding the first-order term of a Neumann series solution for the scattered field. Furthermore, as has been shown, this model also calculates a second-order term via Neumann's successive approximation technique. Physically, this second-order approximation begins to account for secondary scatterings as well as ameliorating the initial tangent plane approximation. In this meeting, the first- and second-order modeled results with backscatter strengths recently measured off of Panama City, FL, by NORDA's Ocean Acoustics Division will be compared.
Correcting the Kirchhoff rough boundary. Interaction model for scattering
Authors: McCoy John J.
Published: October 2005

The Kirchhoff rough boundary interaction model is an incomplete large k approximation, which does not incorporate either shadowing or multiple interaction effects. Numerical implementation suggests that, of these two shortcomings, the neglect of shadowing is the more important. Accordingly, attempts have been made at correcting the Kirchhoff model by introducing a shadow function. For statistical formulations, this introduction is frequently accomplished after the incorporation of a statistical average. This is inconsistent with the underlying physics. Here, shadow functions are shown to have a rigorous basis as statistical measures of the rough boundary geometry, independent of any scattering experiment. That is, one can define a suite of statistical measures of the rough boundary geometry, which can subsequently be interpreted as shadow functions in the context of a scattering experiment. The particular statistical measure that is appropriate for a specific experiment is determined by the statistic of the acoustic signal to be estimated.
Resonance interaction of sound waves with a stratified seabed
Authors: Conde Greta , Jackins P. D. , Gaunaurd G.
Published: October 2005

A novel approach to analyze the reflection and transmission of sound waves from a penetrable and layered fleet interface between two media is described. This approach generalizes the first-order prediction of the resonance scattering theory (RST), which was developed earlier for stacks of arbitrarily many elastic plates separating dissimilar fluid media [Jackins and Gaunaurd, J. Acoust. Soc. Am. 80, 1762–1776 (1986)]. The generalization consists of two portions. The first one makes the lower fluid medium become an elastic half-space, which makes the model useful to predict reflections from a stratified ocean bottom. This portion was briefly analyzed earlier [J. Acoust. Soc. Am. Suppl. 1 80, S116 (1986)]. The second portion, now married to the first, consists in a second-order approximation for the parameters involved in the description of the bottom reflection/transmission coefficients, which retains second-order terms containing second derivatives of the pertinent parameters. This is an application to flat, layered media of an (second-order) acoustical counterpart of an R-matrix formulation for many-body scattering. It is shown how the present generalization contains the earlier first-order (RST) prediction as a particular case, and how it improves its accuracy with a relatively minor additional calculational effort.
A scattering function for bistatic reverberation calculations
Authors: Ellis Dale D. , Haller D. R.
Published: October 2005

The ocean bottom scattering function S(θ,φ;θ′,φ′) depends, in general, on the grazing angles θ, θ′ and azimuthal angles φ,φ′ of the incident and scattered energy. However, most measurements are for backscatter only: B(θ) ≡ S(θφ;θ,φ + π). The few available general measurements indicate strong forward scattering near the specular angle (θ′ = θ, φ′ = φ), and weaker, azimuthally isotropic, diffuse scattering away from the specular. The proposed function combines Lambert's law with Brekhovskikh and Lysanov's surface scattering function, giving S(θ,φ;θ′,φ′) = μ sin θ sin θ′ + ν(1 + ΔΩ)2 × exp[ − (1/2σ2)ΔΩ] where ΔΩ = [cos2 θ + cos2 θ′ − 2 cos θ cos θ′ cos(φ − φ′)]/(sin θ + sin θ′)2. By fitting μ, ν, σ to the backscattering measurements, a general scattering function is obtained. This is an improvement over two common methods of extrapolating backscattering to general scattering. In particular, one common method uses the separable approximation B(θ)B(θ)′, which peaks at θ′ = π/2, rather than at the specular angle. Another common method uses the half-angle approximation B[12(θ + θ′)] which peaks at the correct in-plane grazing angle (if θ′ is replaced by π − θ′ for forward scattering), but fails out of plane.
A 3-MHz acoustic concentration meter that measures suspended sand
Authors: Hanes Daniel M.
Published: October 2005

A 3-MHz acoustic concentration meter (ACM), which measures the intensity of backscattered acoustic energy, has been deployed in the laboratory and in the field in order to estimate the concentration of suspended sand. Techniques for measuring the profile of the concentration of suspended sand close to the seabed with a vertical resolution of about 1 cm are discussed. The scattering characteristics of suspended sand in a laboratory tank were used to provide a method of calibration for the ACM. The dependence of the scattering coefficients upon sediment size was also investigated. The ACM was deployed in the surf zone at Starthope Lane, Prince Edward Island, Canada, in October 1984. In the surf zone, the limitations of such profilometers are (a) air bubbles injected into the water by breaking waves, and (b) the possible variations in sand size with height above the seabed. [Work supported by Naval Facilities Engineering Command.]
Double scattering from two parallel rough surfaces using the facet-ensemble approach
Authors: Schreiner Henry F.
Published: October 2005

Many features of the ocean surface and ocean bottom are generally long crested in shape and can be approximated by thin strips or facets placed edge to edge. Frequency and time-domain (impulse) solutions for diffraction and reflection off this kind of surface have been successfully modeled [W. A. Kinney and J. G. Zornig, J. Acoust. Soc. Am. 77, 1403–1408 (1985)]. The introduction of a second surface of interaction creates a significantly more complex problem. Medwin and Childs presented a Huygens wavelet interpretation for double diffraction off a pair of rigid wedges or troughs [H. Medwin et al., J. Acoust. Soc. Am. 72, 1005–1013 (1982)]. This interpretation is used to construct a model that computes the complex acoustic pressure after scattering off two parallel facet-constructed surfaces. The effects on the correlation between two separated receivers are presented as functions of surface roughness and bottom topography in the frequency band of 500–1000 Hz. Also, comparisons are given at different sea states of single-receiver responses from backscatter off prominent bottom features for a 3-kHz 100-ms signal. All results quantify the effects of the roughness features on signal degradation. [Work supported by Office of Naval Technology.]
Effects of boundary and fluid variations on the enhancement of diffusive transport
Authors: Thompson Charles
Published: October 2005

The role that both boundary vibration and unsteady fluid motion have in enhancing diffusive transport will be discussed. In particular, how acoustically induced vortical disturbances interact with a two-dimensional temperature field will be examined. Such vortical disturbances have been shown to be three-dimensional [C. Thompson, “Stability of a Stokes boundary layer,” J. Acoust. Soc. Am. 81, 861 (1987)]. Hence, parametric interaction between the flow and temperature field to the major mechanism for diffusion enhancement is expected. Numerical results demonstrating the degree of augmentation will be presented. [Work supported by Analog Devices Professorship and NSF.]
Noncollinear interaction of a tone with noise
Authors: Lind Stephen J. , Hamilton Mark F.
Published: October 2005

The noncollinear interaction of a tone with noise is investigated experimentally in an air-filled rectangular duct. A low-frequency band of noise in the (0,0) mode interacts with a high-frequency pure tone in the (1,0) mode. A quasilinear theory developed by Hamilton and TenCate [J. Acoust. Soc. Am. 81, 1703–1712 (1987)] for the noncollinear interaction of two pure tones is generalized to predict the sum and difference frequency sidebands of noise created around the high-frequency tone. When two pure tones interact, the resulting sum and difference frequency sound oscillates in space with a periodicity that depends on the frequencies and interaction angle of the primary waves. The band of low-frequency noise is thus upshifted to sidebands whose spectral shapes are scalloped in appearance. The scalloping becomes more pronounced with range from the source, and increasing the interaction angle reduces the overall levels of the sidebands. Theory and experiment are shown to be in good general agreement. [Work supported by NSF and by ONR.]
Propagation and interaction of two collinear finite amplitude sound beams
Authors: Tjøtta Jacqueline Naze , Tjøtta Sigve , Vefring Erlend H.
Published: October 2005

The propagation and interaction of collinear, high-intensity sound beams are investigated within the scheme of the parabolic equation (Khokhlov-Zabolotskaya-Kuznetsov equation). The equation is solved numerically for two monochromatic sources by using a generalization of the method of Hamilton, Naze Tjøtta, and Tjøtta [J. Acoust. Soc. Am. 78, 202–216 (1985)]. Propagation curves and beam patterns for the various components of the acoustic field (harmonics and combination frequencies) are presented. Special attention is given to the difference frequency component. The analysis extends to ranges beyond the shock formation distance. Various source levels, absorption lengths, and downshift ratios are considered. The results are compared with that obtained for sources operating at moderate intensity (quasilinear theory).
Blast noise propagation prediction
Authors: Shaffer Carolyn R. , Franke Steve , Raspet Richard
Published: October 2005

The U.S. Army Construction Engineering Research Laboratory has performed simultaneous meteorological and acoustic measurements of sound propagation from small explosives. Categorized experimental data have been placed into groups based on similarity of variation in sound speed with height. Using these data groups as input to the pulse fast field program [J. Acoust. Soc. Am. 79, 628–634 (1986)], predictions of sound levels are produced. The comparison of these predictions and measured levels will be discussed.
Active control of sound radiation from plates using force inputs
Authors: Fuller Chris R.
Published: October 2005

Recently much interest has arisen over the use of active control methods to reduce sound fields. The usual method is to use an array of secondary acoustic sources positioned in the radiated field. This technique has proved somewhat successful, but one difficulty is the excitation of unwanted radiation (control spillover) that necessitates the use of many control sources. A new technique is studied in which the active control is applied directly to the radiating surface by a force input. The advantage of this approach is that, by reducing plate response, the radiated sound levels will be controlled globally. The system considered consists of a baffled clamped circular elastic plate excited on one side by an incident acoustic plane wave. Reduction of the radiated acoustic field on the other side of the plate is achieved by a point force applied directly to the plate surface. The complex amplitude of the control force is determined mathematically such that the radiated acoustic intensity integrated over various required sectors is minimized. Results obtained demonstrate excellent global reduction in the radiated field levels for the single control force and the mechanisms inherent in the method are discussed. [Work supported by NASA Langley.]
Vibration isolation for spacecraft using the piezoelectric polymer PVF2
Authors: Sirlin Samuel W.
Published: October 2005

Throughout the remainder of the current decade and through the 1990s, the pointing requirements of spaceborne scientific payloads will grow increasingly more stringent, yet, for reasons of cost effectiveness, the trend will be away from single-payload-dedicated free-flying spacecraft and toward large, multipayload space vehicles. The basebody structural frequencies of space station/space platforms will be significantly lower than those for previous missions, making the traditional separation between pointing controller bandwidth and structural modes impossible to maintain. Man motion and machine vibration disturbances will likely limit the space station attitude control to relatively coarse levels. In the face of such a demanding dynamic environment, future space stations will host attached payloads, some of whose pointing requirements approach those of the free-flying space telescope. These issues drive the need for the development of advanced pointing mount technology that can provide a high degree of precision while simultaneously isolating a payload from a disturbance rich host vehicle. A finite element model of an active softmount based on the piezoelectric polymer poly (vinylidene fluoride) has been developed. The model includes the geometric nonlinearities that are associated with the large deflection capability of the softmount. This model is put together with a simple space station model and then both linear frequency domain and time domain simulations are carried out. The wideband disturbance rejection capabilities of the design are demonstrated, both in the frequency domain and in nominal operations.
Active vibration control by using the wave control concept
Authors: Lu Jiawei , Crocker Malcolm J.
Published: October 2005

A novel active vibration control approach using the concept of wave control is discussed. The idea is to try to change the characteristics of a system and to destroy the condition of resonance response by adding a control force at the boundary of a vibrating system. The approach is different from the modal-space control technique, which is often used in the vibration control of space structures, especially when these structures are built from materials with low damping and are very flexible due to their large size. For the demonstration of this new wave control concept, an active vibration control model for a finite length string is discussed. An exciting force is applied somewhere on the string, and a control force applied at one end of the string is found to absorb the vibrational wave propagating to the end so that no wave reflection appears at the end and the condition of resonance response is destroyed. A beam model has also been developed. The theoretical results are encouraging and better than those obtained by means of the modal-space control approach. The beam model of active vibration control is being investigated experimentally. [Work supported by SDIO/DNA, Contract No. DNA-001-85-C-0183.]
Active control of sound fields in elastic cylinders
Authors: Fuller C. R. , Silcox R. J. , Lester H. C.
Published: October 2005

Much interest has recently arisen over the use of active noise and vibration control in various applications where weight considerations are important. The results of research directed towards applying active methods for reducing noise in the cabins of propeller aircraft will be reviewed. Two differing techniques of implementing the active control will be discussed. The first consists of placing active acoustic sources in the interior space in order to achieve cancellation. The second method relies on active control of the transmitted acoustical energy by vibrational force inputs applied directly to the cylinder wall. Both theoretical and experimental results using simplified models of aircraft fuselages will be presented and the mechanisms inherent in the control action will be outlined.
Interaction impedance of a system of pistons coated with an elastic skin using a plane-wave decomposition
Authors: Boissinot Philippe
Published: October 2005

Expressions of self and mutual impedance of pistons in an infinite, rigid, plane baffle are well known. The array is coated with an elastic rubber skin. Plane-wave decomposition of the compression and shear potentials is performed in the skin as well as the fluid. Expressions are given for the nearfield pressure and for the displacement field in the skin. This pressure is then integrated over the pistons to obtain expressions of self and mutual radiation impedance, which is referred to as average surface velocity. Results are presented for linear (2-D case) and circular (3-D case) radiators in terms of kd (dimensionless product of the wavenumber and the distance between pistons). The other parameters are thickness and elastic characteristics of the skin and the dimension of the piston. As a post processing, the three-dimensional directivity diagram for the whole array can be easily obtained through the plane-wave decomposition in the fluid.
Word-based versus syllable-based models of speech production planning: Evidence from elicited phonological errors
Authors: Shattuck-Hufnagel Stefanie
Published: October 2005

Earlier error-elicitation experiments have shown that single-segment errors are more likely to be elicited when the target segments share position in the word onset, and less likely when the target segments cross word position (e.g., /p/ and /f/ are more likely to interact in “parade fad” and less likely in “repeat fad,” even though both target segments are in prestress position in the latter case). A separate series of experiments using CVC stimuli showed a difference in error patterns when the stimulus words are spoken in lists versus embedded in short phrases; stimuli like “leap note nap lute” elicit about the same proportion of errors in initial and final position, while the phrasal version (“From the leap of the note to the nap of the lute”) elicits far fewer errors in final position. If this difference between word lists and phrases extends to other aspects of error patterns, it might affect the word-position/stress-position results for mixed one- and two-syllable stimuli. However, results show that, when these stimuli are embedded in phrases, the error patterns remain remarkably similar. Moreover, when speakers are asked to generate sentences using the words of the stimulus, instead of reading or reciting the phrases provided by the experimenter, results again support the claim that word-onset consonants are more likely to interact in an error than are prestress consonants. These findings suggest that word structure plays a role in the production processing representation that is in force when single-segment errors occur.
Task-dynamic modeling of interarticulator coordination
Authors: Saltzman Elliot L. , Rubin Philip E. , Goldstein Louis , Browman Catherine P.
Published: October 2005

Speech production involves the formation and release of constrictions at different points in the vocal tract. Progress is reported on a task-dynamic computational model of autonomous coordination among the components of articulatory synergies (e.g., lips and jaw) that participate in motions along functionally defined tract variables (e.g., lip aperture and protrusion). For each speech gesture, a time-invariant dynamical system (damped, second-order) is specified at the tract-variable level, and is transformed into a gesturally and posturally specific dynamical system for the synergy components. Articulatory movement patterns emerge as implicit consequences of the gesture-specific tract-variable control structures and the ongoing postural state of the articulators. Explicit trajectory planning is not required. Significantly, the modeled coordinative processes are exactly the same during simulations of unperturbed, mechanically perturbed, and coproduced speech gestures. All simulations are implemented using the Haskins Laboratories software articulatory synthesizer, and are restricted to the vocal tract's sagittal plane, and the simplified articulatory geometry represented in the synthesizer. [Work supported by NIH Grant NS-13617 and NSF Grant BNS-85-20709.]
A twisting one-mass glottal model
Authors: Rice Lloyd
Published: October 2005

A new model of vocal cord vibration will be presented that represents the cord body by a single mass exhibiting oscillatory behavior on a horizontal axis together with a rotational component. The model is adequate to describe the diverging and converging configurations of the glottal opening as observed at different phases of the glottal cycle. Characteristics of the model are explored under various glottal vibratory modes and are compared with those of existing models such as the popular two-mass configuration.
Estimating vocal tract shapes from x-ray microbeam data
Authors: Ladefoged Peter , Lindau-Webb Mona
Published: October 2005

X-ray microbeam techniques provide data on a few points on the tongue. The possibility of an algorithm that will turn these data into a full specification of the whole tongue shape is tested. A weakness of the system is that it is difficult to place pellets on the posterior half of the tongue. The first goal is thus to investigate what is the minimum number of pellets necessary to predict the shape of the anterior part of the tongue. Data were recorded from seven points, four of which were on the front of the tongue, approximately 15 mm apart. The subject produced short utterances illustrating English vowels. This procedure was then repeated with the four tongue pellets moved approximately 5 mm forward. Image scans of sustained English vowels in which the subject had a chain on the tongue midline consisting of 17 pellets 5 mm apart were also recorded. The results allowed determination of the extent to which tongue shapes can be determined from x-ray microbeam pellets. [Work supported by NIH.]
Interaction of speaking rate and postvocalic consonantal voicing on vowel duration in American English
Authors: Gopal H. S. , Syrdal Ann K.
Published: October 2005

Vowel duration is influenced both by speaking rate and by voicing of the postvocalic consonant. Our study systematically investigates how these two factors interact. Syllable and segment durations were measured for /pVC/ target syllables containing one of eight vowels and voiced or voiceless stops or fricatives. Target syllables were produced in sentence contexts at three speaking rates by four female and three male native American English speakers. Our findings replicate and extend Klatt's incompressibility model of vowel duration [D. H. Klatt, J. Acoust. Soc. Am. 54, 1102–1104 (1973)]. The two factors influencing vowel duration do not combine independently in a multiplicative or additive fashion. Instead, they interact such that vowels manifest a resistance to further shortening.
Token-to-token variation of tongue-body vowel targets: The effect of coarticulation
Authors: Perkell J. S. , Cohen M. H.
Published: October 2005

Variation of vowel targets for a midsagittal point on the tongue body of a single speaker of American English was examined. The subject pronounced multiple repetitions of nonsense utterances of the form /bV(C)Vbʌ/, in which the vowels were /i/, /u/, /a/ and the consonant, when present, was /b/ or /h/. Stress was placed on the second syllable. Movements of a single point on the middle of the tongue-body dorsum were transduced with a new alternating magnetic field movement transducer system. For each vowel, a scatter plot was generated of “target” positions (x,y coordinates) at the moment of minimum tangential velocity. In general, these scatter plots are elongated. When the vowels in the first and second syllables are the same, the scatter in target position is relatively tighter and less elongated than when the vowels are different. When the vowels in the two syllables are different, the long axis passing through the scatter for one vowel is oriented in the direction of the target for the other vowel, providing a “statistically based” demonstration of context dependence of articulatory targets. [Work supported by NIH Grant No. NS04332.]
Fundamental frequency and intensity control in speech
Authors: Strik Helmet , Boves Louis
Published: October 2005

A gradual downdrift of fundamental frequency (F0) and intensity (IL) during speech utterances has been observed in almost all languages. Because both F0 and IL are related to subglottal pressure (Psg) and because Psg is supposed to decrease as the air supply in the lungs decreases, it has been hypothesized that this downdrift, usually called declination, is a passive process. In utterances where declination is absent, like in some types of questions, active countermeasures would then be necessary. In this research, Psg, airflow, electroglottogram, speech signal, and EMG activity of the cricothyroid, sternohyoid, and vocalis muscles have been recorded, while linguistically naive subjects sustained vowels on a fixed F0 and IL and produced a number of sentences with different intonation patterns. Results indicate that there is no direct relation between air supply in the lungs and Psg, and that Psg, F0, and IL can be kept on a desired level without active involvement of the muscle systems that control intonation in speech. [Research supported by the Foundation of Linguistics, funded by Z. W. O.]
The timing of prenuclear high accents in English
Authors: Silverman Kim E. A. , Pierrehumbert Janet B.
Published: October 2005

In English, the alignment of intonation peaks with their syllables exhibits a great deal of contextually governed variation. Understanding this variation is of theoretical interest, and modeling it correctly is important for good quality intonation synthesis. An experimental study of the alignment of prenuclear accent peaks with their associated syllables will be described. Two speakers produced repetitions of names of the form “Ma Lemm,” “Mom LeMann,” “Mamalie Lemonick,” and “Mama Lemonick,” with all combinations of the four first names and three surnames. Segmental durations and the F0 peak location in the first name were measured. Results show that although both speaking rate and prosodic context affect syllable duration, they exert different influences on peak alignment. Specifically, when a syllable is lengthened by a word boundary (e.g., Ma Le Man versus Mama Lemm) or stress clash (e.g., Ma Lemm), the peak falls disproportionately earlier in the vowel. This seems to be related to the syllable-internal durational patterns. It is concluded that rules for generating phonetic details from phonological structure must access information about the upcoming prosodic context.
Application of a variational principle for fluid-structure interaction to the analysis of the response of an elastic disk in a finite baffle
Authors: Ginsberg Jerry H. , Chen Pei-Tai
Published: October 2005

A variational principle derived from the Kirchhoff-Helmholtz integral theorem was previously employed to predict the surface pressure and vibrational response of an unbaffled elastic disk to harmonic excitation [J. H. Ginsberg and A. D. Pierce, J. Acoust. Soc. Am. Suppl. 1 79, S35 (1986)]. Here, the analysis is extended to describe a finite rigid baffle by using assumed mode functions for the pressure distribution along the vibrating and rigid surfaces. Versions using various analytical functions, as well as finite element modes, are developed and examined for convergence, numerical accuracy, and efficiency. Dependence of the surface pressure on the baffle radius is examined; results in the limit of an infinite baffle are shown to agree well with a prior analysis by Alper and Magrab [J. Acoust. Soc. Am. 48, 681–690 (1970)]. [Work supported by the Office of Naval Research, Code 1132-F.]
Ultrasonic wave propagation in multilayered fibrous composites
Authors: Nayfeh Adnan H. , Chimenti Dale E.
Published: October 2005

A unified analytical treatment supported by extensive experimental data of the interaction of ultrasonic waves with single and multilayered fibrous composite plates is presented. The plates are supposed to be immersed in water and subjected to incident waves at arbitrary angles from the normals. For the single laminate plate, solutions are presented for arbitrary azimuthal angles. However, for the general multilayered plate case, treatment is restricted to the case where the wave is incident along planes of symmetry of each individual lamina. Reflection and transmission coefficients are derived, from which characteristic behavior is identified. Comparisons between theory and experiments in the form of reflected energy distribution and identification of dispersion based upon a total transmission criterion are given.
Measurements of ultrasonic parameters in fluid-filled porous metals with different grain size
Authors: Adler Laszlo , Xue Qiang , Jungman Alain , Quentin Gerard
Published: October 2005

Ultrasonic wave propagation in sintered metallic samples (immersed in fluid) was investigated. Samples made out of bronze and out of stainless steel materials with particle sizes ranging from 30–600 μ were used in this study. In order to correlate particle size with ultrasonic parameters, all samples were chosen with approximately the same volume porosity of 30%. Fast and slow compressional waves, surface wave velocities, as well as attenuation, were measured. The frequency dependence behavior of these ultrasonic parameters was studied from 1–20 MHz and correlated to particle size. [This work was supported by NATO Grant 0131/87 and by the National Science Foundation Grant INT-8614592.]
Quantitative particle characterization by ultrasound
Authors: Roy Ronald A. , Apfel Robert E.
Published: October 2005

An acoustic scattering technique was developed for determining the compressibility and density of microparticles (diameter less than 15 μm), which were modeled as fluid spheres. Tone bursts of 2-μs duration and 30-MHz center frequency were scattered from individual microparticles as they traversed the confocal region of two transducers. The scattered bursts were detected at 90° and 180° (backscattering), digitized, and stored in computer memory. By using either the Rayleigh or Born approximations, it was possible to determine the compressibility and density of the particles given a priori knowledge of the particle size and host properties. It was subsequently possible to compute the mean compressibility and density averaged over a population of particles, or to display histograms of scattered amplitude statistics. An experiment was run to assess the feasibility of using polystyrene microspheres to calibrate the instrument. A second study was performed on the buffy coat harvested from whole human blood. Finally, Chinese hamster ovary cells were studied in order to see if the instrument could detect hyperthermia induced membrane blistering. [Work supported by NIH and ONP.]
Dependence on pulse parameters for free radical production by cavitation from short pulsed ultrasound
Authors: Fowlkes J. B. , Crum L. A.
Published: October 2005

Recent data will be presented that indicate the presence of free radicals generated with peak acoustic pressure amplitudes and pulse shapes characteristic of some medical diagnostic devices. The free radicals were detected via a chemiluminescence reaction in an aqueous solution containing luminol using a single photon counting technique. The acoustic pressure threshold for light emission was examined as a function of pulse width, duty cycle, and pulse repetition frequency (PRF); possible explanations for these dependences based upon a simple concept of cavitation inception will bc presented. [Work supported by the National Institutes of Health.]
Interaction of Lamb waves with surface-breaking cracks in centrifugally east stainless steel (CCSS) plates
Authors: Ngoc Tran D. K. , Ng Kin W.
Published: October 2005

Application of conventional ultrasonic nondestructive evaluation techniques to CCSS components in nuclear power plants has been limited principally due to the anisotropy of CCSS materials. Phenomena such as beam skewing and distortion are directly attributable to this anisotropy and cause severe difficulties in defect detection and sizing. The present investigation is intended to use Lamb waves as the probing mechanism to detect and characterize a surface-breaking crack residing on an interior surface not accessible by the ultrasonic probe. Experimental investigation is directed at several techniques for exciting and detecting Lamb waves in this application. The excitability of various Lamb-wave modes in the fd (frequency times thickness) range of interest and the effects of anisotropy and surface curvature on mode propagation characteristics are also studied. Signals due to mode conversion and crack diffraction are used to develop an interpretation procedure for crack detection and sizing. [Work supported by EPRI under contract RP2405-23.]
Possibility of improved laser-Doppler detection of sound by tracking moving phase fronts
Authors: Pierce Allan D.
Published: October 2005

Laser-Doppler anemometry applied to acoustics presents special problems because of the small velocities of fluid flow associated with sound and because of the relatively rapid oscillations. The analysis of Hanish, attributed to General Electric Company (1967) and demonstrated by K. J. Taylor in 1976 and 1981, shows such problems can be overcome in major part for single frequency sound using the spectral density of the photomultiplier tube output. Comparable success is unlikely for broadband sound; an “uncertainty principle” requires averaging over time intervals comparable to the reciprocal of the Doppler shift in frequency; no black box electronics can beat this principle. Difficulties appear insurmountable if characteristic acoustic frequencies are much higher than the Doppler shift. A possible way of overcoming this is to take advantage of the constancy of the sound speed and of the omnidirectionality of incoming sound. Optical systems can be designed which move the effective optical scattering volume along nearly rectilinear paths at the sound speed such that the laser tracks a moving phase front. The fluid velocity sensed by the laser thus appears to be constant rather than oscillating, so one has the opportunity to examine meaningful averages over sufficiently long time periods. [Work supported by ONR.]
Lipreading with single-channel vibrotactile presentation of voice fundamental frequency
Authors: Bernstein Lynne E. , Eberhardt Silvio P. , Demorest Marilyn E.
Published: October 2005

A study evaluated several transformations of voice fundamental frequency (F0) for use by a single-channel vibrotactile device to supplement lipreading. The experimental procedure involved lipreading stimuli from a corpus of over 1500 sentences stored on a video laserdisk [L. E. Bernstein and S. P. Eberhardt, 1986, Johns Hopkins Lipreading Corpus]. There were five experimental conditions. Three transformations of voice F0 were tested: two transformed F0 to a pulse rate code, the third employed two sine waves that were amplitude modulated as a function of F0. Condition 4 provided both F0 and a second stimulator indicating high-frequency speech energy. Condition 5 was visual alone. Subjects were 15 normal-hearing adults in a multiple single-subject design with alternating baseline and test sessions. Analyses of covariance for words correct, words per stimulus sentence, and syllables per sentence showed that all subjects improved in lipreading. Subjects who received a single vibrator for voice F0 lipread more successfully than subjects who did not receive the vibrotactile supplement or who received the dual tactile stimulation.