bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of local spectra in smoothly varying nonhomogeneous environments—Local canonization and marching algorithms
Authors: Steinberg Ben Zion
Published: October 2005

By applying the windowed Fourier transform directly to the Helmholtz wave equation a new formulation that governs the evolution of the local spectra of wave fields in a general nonhomogeneous environment is derived. By further invoking the so-called locally homogeneous approximation, a simplified evolution equation, termed as the locally homogeneous wave equation is developed, together with an upper bound on the error associated with the approximation. It is shown how simple analytical solutions of the new wave equation in a general smoothly varying nonhomogeneous environment can be obtained using well-known analytical techniques, and how the marching methodology connects these new solutions to the original problem described by the Helmholtz equation.
Measurements of bottom-limited ocean impulse responses and comparisons with the time-domain parabolic equation
Authors: Field R. L. , Leclere J. H.
Published: October 2005

Ocean impulse response functions computed with the time-domain parabolic equation model are shown to be consistent with response functions measured in a bottom-limited ocean located off the east coast of the United States. The geoacoustics used in the model are developed from Deep Sea Drilling Project sites near the experimental area. Measured impulse responses are obtained by correlating the measured source signature of a 25- to 150-Hz linear, frequency-modulated signal with the signals received on a 15-element vertical line array. Correlation coefficients computed as a function of depth are used as a measure of comparison between measured and modeled responses. The capability of the time-domain parabolic equation to model wide-angle (68°–75°) multipaths and sub-bottom layers with high impedance contrasts is shown. Correlation loss between response functions measured from different transmissions at the same range is shown to be attributable to the degree to which spatial invariance of the ocean can be assumed.
Correlation of deep ocean noise (0.4–30 Hz) with wind, and the Holu Spectrum—A worldwide constant
Authors: McCreery Charles S. , Duennebier Frederick K. , Sutton George H.
Published: October 2005

One year of ambient ocean noise data, 0.4 to 30 Hz, from the Wake Island hydrophone array in the northwestern Pacific are compared to surface wind speeds, 0–14 m/s (0–28 kn). Between 0.4 and 6 Hz, noise levels increase with wind speed at rates of up to 2 dB per m/s until a saturation is reached having a slope of about −23 dB/octave and a level of 75 dB relative to 1 μPa/√Hz at 4 Hz. This noise saturation, called the ‘‘Holu Spectrum,’’ likely corresponds to saturation of short-wavelength ocean wind waves. It is probably a worldwide constant. Between 4 and 30 Hz, noise also increases with wind speed at rates of up to 2 dB per m/s, but no saturation level is observed and the slope increases to about 4 dB/octave. This may be acoustic noise from whitecaps. On a hydrophone less than 3 km from Wake, noise between 0.5 and 10 Hz increases with wind speed at a rate up to 2 dB per m/s, but absolute noise levels are significantly higher than levels on the other hydrophones more distant from Wake, and no saturation is apparent. Surf breaking against the shore of the island is the probable source of this noise.
Effect of personal and situational variables on noise annoyance in residential areas
Authors: Fields James M.
Published: October 2005

This study uses methods that control for noise level and data quality to objectively evaluate the evidence on 22 personal and situational explanations for annoyance with environmental noise in residential areas. The balance of the evidence from 464 findings drawn from 136 surveys suggests that annoyance is not affected to an important extent by ambient noise levels, the amount of time residents are at home, the type of interviewing method, or any of the nine demographic variables (age, sex, social status, income, education, home ownership, type of dwelling, length of residence, or receipt of benefits from the noise source). Annoyance is related to the amount of isolation from sound at home and to five attitudes (fear of danger from the noise source, noise prevention beliefs, general noise sensitivity, beliefs about the importance of the noise source, and annoyance with non-noise impacts of the noise source). The evidence is too evenly divided to indicate whether changes in noise environments cause residents to be annoyed more, less, or about the same as would be expected in long-established noise environments. The evidence shows that even at low noise levels (below DNL 55 dB), a small percentage are highly annoyed and that the extent of annoyance is related to noise exposure.
Comparison of data and parabolic equation solutions for long-range pulse propagation
Authors: Heaney Kevin D. , Kuperman W. A. , McDonald B. Edward , Collins Michael D.
Published: October 2005

A propagation model that combines the horizontal refraction of the adiabatic mode solution and the accurate field computation of the parabolic equation (PE) method is applicable to long-range problems. In a previous application of this model, qualitative agreement was achieved for narrow-band data from the Heard Island Feasibility Test (HIFT). The broad-band extension of this model has been applied to two long-range propagation paths. Data have been analyzed from a single-slice tomography experiment that involved a 1000-km propagation path in deep water and a source centered at 250 Hz. These data were previously modeled with a WKB solution [Duda etal., J. Acoust. Soc. Am. 92, 939–955 (1992)], which breaks down for the lower modes in the sound channel. These results are in agreement with these data even for the arrivals associated with the lower modes. The Heard Island to Christmas Island propagation path of the HIFT has also been analyzed. Several features along this path cause significant mode coupling, including a sloping bottom near the source, the Antarctic Circumpolar Convergence, and a sea mount. Although there is variability in this data due to fluctuations, the observed dispersion and arrival structure is consistent with these results.
Modeling of the acoustic propagation through the Gulf Stream
Authors: Desharnais F.
Published: October 2005

Propagation loss modeling has been done in support of the experimental cruise ‘‘Maple Gelato’’ conducted in an area of the Gulf Stream, east of Cape May, New Jersey (by the SACLANTCEN, Italy, and the Defence Research Establishment Atlantic, Canada). The experiment was conducted in summer conditions (September 1992), and seamounts were also present in the area. Although the data will not be presented at this time, the modeling of the propagation through the front, done with the SACLANT parabolic equation model, will be presented for frequencies ranging from 10 to 300 Hz, and for sensors distributed along a 300-m vertical array. Preliminary results show that the effect of the front is to redistribute the energy in space, and to shift convergence zones. The acoustic levels within the two first convergence zones however are not affected substantially, although this depends on source and receiver depths. Seamounts, depending on their locations relative to the source, can counteract the effects of the fronts. The modeling results will be compared with results obtained in other frontal areas, to emphasize the particularities of the Gulf Stream.
Comparison of time-domain parabolic equation and measured ocean impulse responses in a range-dependent environment
Authors: Leclere James H. , Field Robert L.
Published: October 2005

Ocean impulse response functions computed with the time-domain parabolic equation model are shown to be consistent with measured response functions in a shallow-water range-dependent environment off the east coast of the United States. Impulse response functions are measured by correlating the source signature of a 20- to 150-Hz linear, modulated signal with signals received on a 15 element vertical line array. Environmental inputs to the model are derived from Ocean Drilling Project (ODP) sites near the experiment location. Correlation coefficients as a function of depth are used to compare measured and modeled responses at three separate ranges. [Work supported by The Office of Naval Research under the Naval Research Laboratory/Stennis Space Center Acoustic Transients Project.]
Acoustic and elastic wave scattering from elliptic-cylindrical shells
Authors: Radlinski Ronald P. , Simon Murray M.
Published: October 2005

An acoustic scattering formulation has been derived from a modification of the extended boundary integral method (null-field approach) developed for elastic wave scattering from infinite cylindrical shells of arbitrary shape. Thin shell theory is assumed to describe the motion of the scatterer. Acoustic and elastic p-p wave scattering calculations are presented for elliptic-cylindrical shells of different materials and eccentricities. At low frequencies, the scattering by an elliptical shell in a fluid is dominated by the bending resonances. At higher frequencies, the acoustic scattering is strongly dependent on the angle of incidence, material characteristics, and the predominately extensional structural resonances. In an elastic material, resonant modal responses of the shell were found to increase mode conversion of dilatational waves into shear waves. By comparison with elasticity theory for shells and by extrapolations from thin and thick plate theories, the limitations of the thin shell theory are shown to be material dependent. The present method is used to re-examine examples of backscatter from elliptic-cylindrical shells reported in other studies.
Torsional mode coupling and filtering in a composite waveguide with multiperiodic interface corrugations
Authors: Asfar Omar R. , Hawwa Muhammad A.
Published: October 2005

This study is concerned with the interaction of six torsional modes in a composite axisymmetric waveguide whose interfaces are sinusoidally corrugated in the axial direction. The modes are interacting when two resonant conditions on the codirectional modes and a Bragg condition occur simultaneously. In light of the weakness of the interface corrugations, the perturbation method of multiple scales is used to derive the mode coupling equations. A novel numerical scheme for two-point boundary-value problems is used to solve the coupled amplitude equations. The power reflection coefficient of a filter section is then calculated for the cases of uniform, tapered, and chirped corrugations. An optimal filter is realized by combining both taper and chirp thus producing a nearly ideal characteristics.
Categorical perception of silent-center syllables
Authors: McLeod Heather , Jongman Allard
Published: October 2005

Work by Strange and colleagues [e.g., Strange etal., J. Acoust. Soc. Am. 74, 695–705 (1983)] has shown that CVC syllables without the steady-state vowel (‘‘silent-center syllables’’) are as accurately recognized as CVC syllables containing the steady-state vowel, suggesting that dynamic rather than static properties are more important in vowel perception. The present study expands this line of research by studying the identification of silent-center syllables as members of a vowel continuum. Two synthetic continua were presented to listeners for identification: A [bib–b(eh)b] continuum and a silent-center [bib–b(eh)b] continuum. The silent-center version was created by excising the steady-state portion of the original continuum, leaving the formant transitions intact. A comparison of the two identification functions revealed a significant shift, suggesting that full and silent-center syllables are not perceptually equivalent in this type of identification task. The results will be discussed in terms of theories of vowel perception.
Compensation abilities to lip perturbations of rounded vowel [u]
Authors: Savariaux Christophe , Perrier Pascal , Orliaguet Jean-Pierre
Published: October 2005

An experiment is described involving lip perturbation, using a large (20 mm) Plexiglas tube, during the production of the rounded french vowel [u]. Ten naive speakers pronounced isolated repetitions of [u] in three conditions: (1) without perturbation, (2) with the lip-tube after a learning period of 20 repetitions, and (3) with the lip-tube after 20 repetitions with information on the way to deal with the perturbation. X-ray recordings were made at the end of each phase, and formants were extracted from the acoustical record. Compensation abilities were evaluated by considering the first three formants, in reference to the difference limens [Mermelstein, J. Acoust. Soc. Am. 63, 572–580 (1978)]. At the end of the second phase, one speaker was able to compensate for the perturbation. For all other speakers, we observed a strong increase in F2. For the third phase, the speakers were divided into three groups who were given different information in order to help them compensate for the perturbation (first group: articulatory information, second group: acoustic information, third group: both types of information). Speakers in the first group all produced a fairly good [u]. Speakers in the second group showed some enhancement, but the F1–F2 targets were not reached. In the third group, no reliable compensation was observed. Some interpretations are proposed concerning compensation strategies and speech space control.
Matched-field estimation of scattering from Arctic ice—Analysis of the CEAREX 89 field experiments
Authors: Kapoor Tarun K. , Schmidt Henrik
Published: October 2005

Scattering experiments were conducted in 1989 in the Norwegian–Iceland Sea using explosive charges detonated at varying depths. The scattered field was received at a crossed horizontal hydrophone array positioned at a depth of 60.0 m. In this paper, the scattering of low-frequency acoustic waves from the Arctic Ice sheet will be evaluated via matched-field processing of short-range returns. Using near-field beamforming (focusing), which assumes a point scatterer, it was possible to isolate the scattering hot spots under the ice sheet. Essential inputs to this processing include the source location and shot times which were determined using an adaptive least-squares estimator in a matched-field approach. [Work supported by ONR.]
The influence of boundary layer on elastic wave scattering by spherical inclusions
Authors: Lévesque Daniel , Piché Luc
Published: October 2005

The influence of a boundary layer on the scattering of elastic waves by spherical inclusions is investigated. Based on the exact transition matrix (T) developed for layered obstacles [A. Boström, J. Acoust. Soc. Am. 67, 399–413 (1980)], a numerical study is performed for all values of h/a, where h is the layer thickness and a is the effective radius of the layered obstacle. For h/a ≪ 0.1, the layer behaves like an interface, allowing one to investigate a wide range of boundary conditions. Except for high mass density interfaces, the scattered field amplitude is sensitive mainly to the normal and transverse stiffnesses and classical solutions for the so-called rigid and slip boundary conditions are recovered. For h/a<0.1, the layer acts as an interface region and property changes of the host near the obstacle can be modeled. Ultrasonic measurements with charge-filled polymers present evidence for such a layer. Finally, for h/a≊0.1, the layer behaves as a coating or a shell depending on the mass density. In this case, full interactions are included in the formalism.
Increased backscattering from an inhomogeneous liquid–solid interface at the Rayleigh angle
Authors: Nagy Peter B. , Adler Laszlo
Published: October 2005

It is shown that the experimentally observed peak in the incoherent backscattering from a liquid–solid interface at the Rayleigh angle is caused by the sharp maxima of the longitudinal and shear transmission coefficients. Of course, both refracted waves are evanescent in this region, i.e., they do not carry energy away from the interface but rather keep the vibration within approximately one wavelength of the surface. Nevertheless, the resulting vibration in the solid is much stronger than at other angles of incidence. The incoherent scattering can be caused by either geometrical irregularity or material inhomogeneity (e.g., surface roughness or polycrystalline grain structure). This paper presents analytical and experimental results showing that, regardless of the physical nature of the scattering inhomogeneity, there is a distinct maximum in the backscattered intensity around the Rayleigh angle. The width of the peak is determined by the density ratio between the solid and the liquid while the maximum backscattering at the peak is essentially independent of the average material properties and is determined solely by the scattering inhomogeneity.
Wave scattering from a thin random fluid layer
Authors: Zhang Yuan , Weaver Richard L.
Published: October 2005

The problem of a plane harmonic wave obliquely incident from a homogeneous ideal fluid space upon a random fluid layer is considered. The thin layer is taken to have properties that vary randomly only in the in-plane directions. A first Born approximation is used and the average intensity of the incoherent part of the scattered wave is found to be proportional to the two-dimensional spatial Fourier transform of the auto- and cross-covariance functions of the layer, within the confines of the validity of the first Born approximation. Therefore, the inverse scattering problems may be straightforward, provided the necessary experimental data of the incoherent wave can be found. A sufficient condition is also given to estimate the range in which the second-order term in the Born series can be ignored. [Work supported by the National Science Foundation Solid Mechanics Program, Grant No. MSM-91-14360.]
Scattering from partially contacting interfaces
Authors: Harris J. G. , Yogeswaren E.
Published: October 2005

Fatigue cracks and diffusion bonds are two common objects of nondestructive inspection. Both are characterized by extensive regions of rough, partially contacting interfaces, where the characteristic size of a void or asperity is much smaller than the compressional wavelength in the material, at frequencies on the order of 100 MHz. Work describing efforts to characterize scattering from such an interface, including the effects of multiple scattering, is described. The multiply scattered wave fields are calculated by solving scalar or vector integral equations. Two formulations will be discussed. One uses a specific interface model consisting of multiple, small cracks having arbitrary lengths and spacings, while the other uses a more general formulation called a polarization theory [G. Wickham, J. Nondestr. Eval. (to appear in 1993)]. The scattered wave fields are then used in a measurement model, whose purpose is to emulate the effects that the emitting and receiving transducers have upon the incident and received signals. Both scattering by an incident plane wave and by a focused beam are discussed. [Work supported by NSF.]
On the scattering of elastic waves in inhomogeneous material
Authors: Aymé-Bellegarda Eveline J. , Habashy Tarek M.
Published: October 2005

This work is concerned with the imaging and quantitative characterization of objects embedded in inhomogeneous material, using acoustic or elastic waves as the interrogating sources. Such problems are recurrent in many areas such as, for instance, geophysics, oceanography, and medical imaging. The interest here hinges on the determination of high contrast channels embedded in multilayered elastic structures. A general framework is presented, based on vector integral equations. In addition to being suitable for both the forward and inverse problem, this framework is appropriate for any geometry and transmitter–receiver characteristics. Tractability issues are discussed, leading to the consideration of the Born approximation for inhomogeneous elastic background. To go beyond the inherent limitations of this approximation, an iterative inversion scheme is introduced. The method is illustrated in the case of a 2-D problem. First, the forward model is validated against an independent means based on a finite-difference approach. Then, constrained least-square reconstruction is performed, aiming at recovering the density distribution of a 2-D fluid-filled object buried in high contrast layers.
Variational methods and boundary conditions for Bloch waves in composite materials
Authors: Jiao B. L. , Siems R.
Published: October 2005

A modified variational procedure is presented for an efficient determination of dispersion curves and especially of normal modes of phonons in periodic, inhomogeneous materials with abrupt changes of material constants: The Bloch wave eigenvalue problem is solved by a Ritz method using expansion functions with discontinuous first derivatives for the displacements, which satisfy the boundary conditions for displacements and stresses. Explicit expressions are given for a threefold periodic arrangement of inclusions in a matrix. Questions of convergency and completeness of the expansion are discussed. A numerical comparison with results obtained with customary Fourier trial functions for structures inhomogeneous in one and two dimensions and with exact results for one dimensional inhomogeneities shows the great accuracy of the method.
Ferroelectric domain layer wave in ABA type 180° domain sandwich structure
Authors: Li Xingjiao , Wu Zhiming , Chen Jeffery , Cai Dingguo , Li Shaopin , Chen Zhuohui
Published: October 2005

The ferroelectric domain layer wave (FDLW) in the ABA type 180° domain sandwich has been discussed. The polarized direction of A material is opposite to that of B material. The results show that there exist two types of ferroelectric domain layer waves in the structure. One is the FDLW of symmetric vibration [X. Li, J. Appl. Phys. 56, 88 (1984)], another is the FDLW of asymmetric vibration. The asymmetric vibration FDLW is a new FDLW, it has a cutoff frequency. From the dispersion relation of the two modes, it is shown that the frequency of the asymmetry mode is higher than the frequency of the symmetry mode. The amplitudes of displacement fields and potential fields of the asymmetry mode are smaller than that of the symmetry mode in the B layer. The system that is composed of the different A, B materials have been analyzed and the general dispersion relation is given; it has a very simple formation, and the relations between the parameter of A, B material and dispersion relation have been discussed.
Electroacoustic waves in a piezoelectric-layered structure under periodic metal gratings
Authors: Zhu Youxin , Wu Zhiming , Cai Dingguo , Li Xingjiao
Published: October 2005

The propagation of electroacoustic waves in a piezoelectric-layered structure under periodic metal gratings is investigated. A general theory that fits both the elastic and electric periodic boundary conditions has been developed and is applicable to a grating with an arbitrary electrical connection between adjacent metal strips. Numerical works are given. It is found that the considered electroacoustic waves, which penetrate deep into the substrate in the absence of the metal grating, become trapped at the interface between the substrate and the surface layer when the grating is presented. It is noted that the penetrate depth is heavily dependent on the grating thickness. The electroacoustic wave penetration depth can be adjusted by a proper design of the grating structure to minimize the acoustic power density in the layered structure. The relevant attributes of the wave such as particle displacement electrical potential, and dispersion are also computed and analyzed. Some practical application in acoustoelectronics are suggested. [Work supported by NNSF.]
The subband in ferroelectric 180° multilayered domain structure
Authors: Wu Zhiming , Cai Dingguo , Zhu Youxin , Chen Jeffery , Li Xingjiao
Published: October 2005

In a ferroelectric 180° multilayered domain structure, the ferroelectric domain layer wave (FDLW) propagating along the domain interface would cause a periodic electric potential field [X. J. Li etal., J. Phys. C 2, 9577–9588 (1991)]. The periodic potential field would split the energy band of electrons into subbands called the ‘‘minigap.’’ The feature of the minigap is that it depends on the existence of FDLW because the wave vector and amplitude of FDLW would affect the minigap structure. This is different from the normal superlattice in which the minigap is determined. In addition, the periodic potential fields have the symmetry vibration modes and asymmetry vibration modes corresponding to the same dispersion relation of FDLW, while the displacements of the two opposite domains are asymmetry and symmetry, respectively. The calculating results of the subband in ferroelectric 180° domain superlattice have shown that the subband variation with the vector k of FDLW is similar to the subband variation with periodic width of superlattice.
Modeling format frequency discrimination
Authors: Sommers Mitchell S. , Kewley-Port Diane
Published: October 2005

Changes in the formant frequencies of steady-state vowels can produce level changes in harmonic components throughout the bandwidth of the stimulus. To successfully model thresholds of formant frequency discrimination, however, it is necessary to determine whether level changes in components spectrally remote from the altered formant affect discrimination performance. Therefore, the present experiments investigate which harmonics affect performance in order to evaluate excitation-pattern models of formant frequency discrimination. Synthetic tokens of the vowels /u/ and /e/ were generated by digitally summing the first 24 harmonics of a 200-Hz fundamental. Minimal uncertainty thresholds were obtained for F1 increments in /e/ and F2 decrements in /u/ when: (1) all harmonics were allowed to vary; (2) harmonic level variations were restricted to a subset of components spectrally close to the altered formant; and (3) harmonics remote from the shifted formant were excluded from the stimulus. Results indicated that thresholds for conditions (1) and (2) did not differ until level variations were restricted to between two and three components. Thresholds for condition (3) were not significantly different than those obtained for vowels with a full complement of harmonics. Excitation-pattern models of the results will be discussed. [Research supported by NIH.]
On the distinctive pitch of vowels: Perceptual prototypes for sinewave analogs?
Authors: Rubin Philip E. , Remez Robert E. , Pardo Jennifer S. , Fellowes Jennifer M. , Blumenthal Eva Y. , Warren Danielle A. , Schanzer Bella
Published: October 2005

A recent study by Kuhl etal. (1991) found striking perceptual correspondences between vowels and steady tones. Whether subjects experienced spoken vowels, visually presented images of articulating faces producing vowels, or imaginary vowels, they matched the vowel /ɑ / with a low-pitch tone, and /i/ with a high-pitch tone. However, tonal analogs of vowels were matched in the opposite manner, with low pitch associated with the vowel /i/ and high with the vowel /ɑ /. These sine-wave vowels were therefore excluded from hypothesized recognition mechanisms employing distinctive vowel pitches as perceptual prototypes. This finding is counterevidence to claims that tonal analogs of utterances are perceived through ordinary means. The present study employed sinewave realizations of several words differing solely in the nuclear vowel, /ɑ / or /i/, in an attempt to replicate and extend this finding. Subjects were asked to match the predominant pitch or vowel quality of these medial sine-wave vowels to the pitch of a single tone. The results will be discussed with respect to claims about the ordinariness of the perception of sinewave replicas and hypothetically prototypic distinctive vowel pitches. [Research supported by NIDCD and NICHD.]
Free and forced vibrations in a floating ice sheet: Modeling and comparison with data
Authors: Yang T. C. , Yates T.
Published: October 2005

Time domain waveforms excited by an impulse, point force are modeled using fluid-loaded thin plate theory and compared with measured data collected on ice-implanted geophones. In the frequency domain, the solution, expressed as an integral over wave number, can be expressed in terms of poles (free waves) and branch cuts (forced waves). The time domain solution is obtained by taking a Fourier transform of the frequency response of the plate, weighted by the (measured) source spectrum. The modeled time domain waveform compared favorably with the received time series data. A simple direct time domain solution for the forced wave in a thin plate in air also approximates the data well. It is shown that the forced wave solution produces the ‘‘abnormal’’ dispersion relation observed in recent geophone data. The free-wave solutions, which have been extensively studied before, also agree with the geophone data.
The curious case of English /w/ and /y/
Authors: Lisker Leigh
Published: October 2005

English /w/ and /y/ are often identified phonetically with /u/ and /i/: /w/ and /u/ involve dorso-velar constriction and lip rounding, /y/ and /i/ raising of the tongue toward the palate without rounding. Although the glides are thus more or less equated with the vowels, most linguists keep /w, y/ apart from /u, i/. The justification is that /w, y/ are nonsyllabic ‘‘glides,’’ whereas /u, i/ are not. As a phonetic basis for keeping /w, y/ and /u, i/ apart, this is not very compelling. Aside from the fact that the articulatory postures for /w, y/ may not always be identical with those for /u, i/, the phonological argument advanced here is that /w/ differs from /u/ in being distinctively rounded, but not distinctively dorso-velar, while /y/ is distinctively palatal, but not distinctively unrounded. In fact, the same articulatory configuration, that of a rounded palatal [inverted aitch], is differently interpreted in the contexts /i–i/ and /u–u/, so that [i(inverted aitch)i] is /iwi/, while [u(inverted aitch)u] is /uyu/. Thus the same vocal tract configuration, reflected in an identical F pattern, is differently interpreted in the two vocalic contexts. It would seem that the listener knows that it was achieved by two quite different articulatory maneuvers. [Work supported by NIH Grant HD-01994 to Haskins Labs.]
An examination of the perceptual magnet effect
Authors: Lively Scott E.
Published: October 2005

Recently, Kuhl [Pecept. Psychophys. 50, 93–107 (1991)] has argued that speech perception is guided by phonetic prototypes that are assumed to be stored in long-term memory. This claim is based on the finding of a ‘‘perceptual magnet effect.’’ According to Kuhl, speech prototypes act like ‘‘magnets’’ because they attract similar stimuli to themselves. Furthermore, prototypes attract other stimuli more strongly than nonprototypes. Thus vowels that surround a prototypical stimulus are more difficult to discriminate than vowels that surround a nonprototype. Data are presented from vowel ‘‘goodness’’ rating experiments that suggest that listeners’ prototypes for the vowel /i/ may be more extreme and variable than Kuhl’s data indicate. Data are also presented from a categorization experiment that indicates that all of Kuhl’s vowels may not be from the same phonetic category. These findings call into question the basis of the perceptual magnet effect. An alternative interpretation of both sets of findings is given. [Work supported by NIH.]
Imaging the tongue: Ultrasound
Authors: Stone Maureen
Published: October 2005

This videotaped presentation will explain the fundamentals of using ultrasound imaging to study the vocal tract and vocal folds during speech and swallowing. The demonstration will focus on three areas. First, the placement and use of the ultrasound transducer for different types of measurements, including the use of a transducer/head holder to allow reliable, repeatable measurements. Second, a sampling of data will show the tongue in motion in several planes, and the fluidity and complexity of its movement. Vocal fold movement will also be presented. Finally, the tape will demonstrate the use of the instrument on several normal and patient subjects, including profoundly deaf speakers and swallowing-disordered patients.
The rise and fall of the soft palate: The Velotrace
Authors: Bell-Berti Fredericka , Krakow Rena A. , Ross Dorothy , Horiguchi Satoshi
Published: October 2005

The Velotrace is a mechanical device that makes possible the collection of analog data on velar position [S. Horiguchi and F. Bell-Berti, Clin. Pal. J. 24, 104–111 (1987)]. The device consists of two levers connected through a push rod, carried on a support rod. The Velotrace is positioned with the support rod resting on the floor of the nasal cavity, with one lever resting on the nasal surface of the velum. When this internal lever is deflected upward, the second (or external) lever is deflected toward the speaker; i.e., changes in the position of the lever resting on the velum are directly reflected in the changes in position of the external lever. The position of an LED fixed to the end of the external lever is monitored with an optoelectric camera, and recorded with an FM tape recorder. [Supported by NIDCD Grant No. DC-00121 to the Haskins Labs.]
The whole body plethysmograph in speech research
Authors: Ohala John J.
Published: October 2005

The whole body plethysmograph is used to monitor a subject’s pulmonic activity and consists of an air-tight box just big enough to contain the subject. The subject breathes and speaks through a tube or facemask which vents to the atmosphere. Changes in thoracic or abdominal volume during breathing cause proportional changes in the volume of the air inside the box. Either an air pressure or an air flow transducer may be mounted in a second vent in the wall of the box in order to measure the aerodynamic variations associated with respiration including those in the expiratory phase on which virtually all voice production is superimposed. The device, which can be constructed fairly simply, is as accurate as the transducer used. If the breathing vent is momentarily closed off, leaving the subject to breathe the air inside the box—which now constitutes a closed system as regards exchange of air between speaker and box—a rough measure of subglottal air pressure may be obtained in a noninvasive way. Its use in phonetic research will be demonstrated by means of a 10-min video.
Physiologically based models of phonation
Authors: Titze Ingo R.
Published: October 2005

The process of gathering data from excised larynges, tissue samples, mechanical models, and human subjects is shown. These data are integrated by computer to simulate the physics of air and tissue motion in the larynx and the vocal tract. Voice simulation offers many pedagogical and clinical opportunities in addition to the obvious research applications.
Dynamic electropalatography
Authors: Hardcastle William J.
Published: October 2005

This videotape will present a demonstration of electropalatography (EPG). EPG uses a thin acrylic pseudopalate embedded with contact-sensitive electrodes to measure tongue–palate contact during speech movements. Its applications are far reaching. Two major applications are its use in examining coarticulatory effects in speech and as a biofeedback tool for speech disorders.
The correlation between ocean wave energy dissipation and ambient noise
Authors: Felizardo Francis C. , Melville W. Kendall
Published: October 2005

An experiment that measured the NSL between 2 to 25 kHz, the wind speed U, and the directional wave spectrum was conducted off the coast of Oregon to examine the correlation between the ambient noise spectrum level (NSL) and surface wave parameters. These measurements show that although the correlation between the ambient NSL and the rms wave height is poor, the NSL and wave height spectrum energy levels at frequencies somewhat higher than the spectral peak give correlation coefficients that are comparable to that between the well-known correlation between U and NSL. Estimates of wave energy dissipation due to breaking waves using models proposed by Komen etal. [J. Phys. Ocean. 14, 1271–1285 (1984)] and Phillips [J. Fluid Mech. 156, 505–531 (1985)] likewise give comparable correlation coefficients. These results are consistent with the laboratory experiments [M. R. Loewen and W. K. Melville, J. Fluid Mech. 224, 601–623 (1991)] which show that the energy dissipated by wave breaking scales with the acoustic energy radiated. The implications of these results for acoustic remote sensing of breaking waves and associated processes of air–sea interaction are discussed.
Influence of bathymetry on the spatial characteristics of ambient noise
Authors: Newcomb J.
Published: October 2005

The ambient noise field is a complex and highly variable phenomena with many components, including contributions due to shipping. Spatial characteristics (e.g., the horizontal directionality) of the ambient noise field have been measured with towed line arrays in many of the major water masses of the world. This paper will address the effects of bathymetry on the propagation and measurement of ambient noise. It is shown that, in many cases, the horizontal directionality of the ambient noise can be fully understood only when the bathymetry along the propagation paths has been considered. Examples of measured data will be presented illustrating the effects of bathymetric stripping and bathymetric shielding on the spatial character of the ambient noise. Other examples of measured data will be shown demonstrating that bathymetric influences are not limited to a narrow frequency range. In addition, modeled data will be used to illustrate the effects of the surrounding bathymetry on noise and signal propagation. [Work supported by the Office of Naval Research (ONR) and the ASW Environmental Acoustic Support (AEAS) Project.]
Determination of structural impedance from scattering data
Authors: Gaumond Charles F. , Sarkissian Angie , Williams Earl G. , Yoder Timothy J.
Published: October 2005

Knowledge of the structural impedance is significantly important in the computation of acoustic scattering and radiation because it contains all the information about the structure that is necessary for the evaluation of the scattered or radiated field in any fluid medium. The inverse problem of determining the structural impedence from scattering measurements is treated. Based on the determination of surface field quantities from acoustical holography measurements, an algorithm is developed for the reconstruction of the structural impedence from knowledge of the scattered field for a set of incident plane-wave directions. The resolution of this reconstruction is treated. Higher resolution may be obtained with near-field measurements.
Optoelectronic measurement of orofacial motions during speech production
Authors: Vatikiotis-Bateson Eric , Munhall Kevin , Ostry David
Published: October 2005

Optoelectronic position sensing devices have been important in the study of speech articulation. While limited to the kinematics of externally visible structures such as the lips and the jaw, such systems can be used easily with a wide range of subjects. This video shows how an innovative marker-tracking system, OPTOTRAK (Northern Digital, Inc.), is currently being used in three areas of experimentation: (1) rigid body analysis in which 3-D motion of the jaw is decomposed into its three orientation and three translation components; (2) modeling of the relation between muscle activity (EMG) and 3-D motion of the lips and jaw using artificial neural networks; and (3) mapping facial motions for possible use in orofacial modeling and audiovisual recognition. The first experiment shows how technical developments, resulting in accurate measurement of 3-D motion, now make it possible to calculate all orientation angles and positions necessary to fully describe structures such as the jaw. The second area demonstrates a more traditional paradigm in which several types of data must be acquired simultaneously. The third area illustrates the growing interest in mapping speech events to facial motion as well as to changes in vocal tract shape.
Effect of stimulus intensity on the pitch of a complex tone’s spectral edge
Authors: Houtsma Adrianus J. M. , Kohlrausch Armin , Kef Peter A. , Horst Johannes W.
Published: October 2005

Six subjects made pitch matches between a fixed-intensity sinusoidal comparison tone and a complex test tone with harmonics 1 through 20 in zero-phase and fundamentals between 46 and 54 Hz at sensation levels between 10 and 70 dB. Tone and intertone gap durations were 500 ms. All subjects performed six matches at all five fundamental frequency values and at seven intensities. As control, subjects also matched pitches between pure tones around 1000 Hz. Mean matches to complex tones were found to depend on intensity, at a subject-averaged rate of 0.12% dB, always going from a pitch below the edge frequency at low sensation level to a pitch above the edge frequency at high sensation level. This is consistent with evidence from cochlear nerve data by Evans [Philos. Trans. R. Soc. London Ser. B 336, 381 (1992)]. Standard deviations of complex-tone matches were typically only a factor two larger than those of pitch matches between pure tones, even at the lowest sensation levels. This is not well understood in terms of cochlear nerve data which suggest that edge pitch should fade away at sensation levels below 30–40 dB [Horst etal., J. Acoust. Soc. Am. 78, 1898–1901 (1985)].
A computer model of the physiological basis of the extraction of pitch from tone complexes
Authors: Meddis Ray , Hewitt Michael J.
Published: October 2005

A low pitch sensation can be heard when a mid-frequency (e.g., 500–4000 Hz) carrier is amplitude modulated at a rate between 100 and 400 Hz. The output of multipolar neurons in the ventral cochlear nucleus are known to reflect strongly modulation of the acoustic stimulus and even to amplify it. Other cells in the inferior colliculus respond by increasing their rate of firing when a rate of amplitude modulation, critical to that cell, is applied to a stimulating tone. The system to be described consists of a model of the auditory periphery that simulates auditory-nerve fiber input, arrays of multipolar point-neuron models that receive this input, and arrays of inferior colliculus unit models that receive input from the multipolar cells. Individual model units behave similarly to physiological units. Arrays of IC model units also show many properties associated with psychophysical studies of pitch including the ability to extract ambiguous pitch from inharmonic tone complexes.
Modulation-following responses and peripheral neural adaptation
Authors: Smith Robert L. , Passaglia Chris , Nguyen My
Published: October 2005

In response to tones that are amplitude modulated by sinusoids, a voltage at the modulation frequency can be recorded from the round window of anesthetized gerbils. This ‘‘modulation following response’’ (MFR) displays a number of properties that suggest that it is predominantly composed of summated auditory-nerve responses and may provide a convenient monitor of peripheral neural adaptation. The MFR is a maximum at tone onset and then decays or adapts towards a sustained value that is maintained throughout the duration of the stimulus. At sufficiently low-stimulus intensity levels, the MFR can be reduced by simultaneous or forward masking in a frequency-selective manner similar to the compound action potential (CAP) at tone onset. The MFR is generally eliminated, along with the CAP, by the application of Tetrodotoxin at the round window. The MFR also exhibited a bandpass ‘‘modulation transfer function’’ and a complex dependence on intensity level that differ from single-unit response characteristics, and appear to reflect the spatiotemporal summation producing compound responses at the round window. [Work supported by NSF.]
The effects of notched noise on detection of amplitude modulation of narrow-band noise
Authors: Strickland Elizabeth A. , Viemeister Neal F.
Published: October 2005

The temporal modulation transfer function for narrow-band noises does not appear to change substantially as a function of carrier frequency, although auditory filter width increases with frequency. One possibility is that listeners always listen at high frequencies, where auditory filter width is relatively broad, regardless of the carrier frequency. To examine this possibility, detection thresholds for sinusoidal amplitude modulation were measured for a low- and a high-modulation frequency as a function of frequency location of a narrow-band noise carrier, in the presence of low-pass, high-pass, or notched noise. Results indicated that high-pass and notched noise produced a nearly identical increase in thresholds, while low-pass noise had little effect. The effect of the noise was similar for all carrier frequencies, suggesting that listeners were not listening at high frequencies in all conditions. The similarity of the effects of high-pass and notched noise indicate that listeners may use spread of excitation, when available, to aid in detecting modulation of narrow-band signals. [Work supported by NIDCD Grant No. DC00683.]
Fresnel width of the coupling regions of generalized leaky Lamb waves and Fermat’s principle
Authors: Marston Philip L.
Published: October 2005

Ray methods describe guided-wave scattering contributions based on local coupling processes. To estimate the effective width of coupling regions for launching and radiation of sound by leaky guided waves of phase velocity cl, Fresnel volume concepts of Y. A. Kravtsov and others [see, e.g., P. L. Marston, PhysicalAcoustics (Academic, New York, 1992), Vol. 21, pp. 1–234] were generalized. First, the usual coupling condition on the angle of incidence θl for a sphere or cylinder, sin θl=c/cl, is derived by Fermat’s principle. Then the angular shift Δθl is derived for a π radian phase deviation from the Fermat ray. For a far-field source or observer, ‖Δθl‖≊√2π/(ka cos θl) is a measure of the ray width. Fermat’s principle is also examined for a prompt backward wave mechanism [D. H. Hughes, Ph.D. thesis, Washington State Univ. (1992)] for the high-frequency scattering enhancement by shells. [Work supported by ONR.]
Ray approach for analyzing wave scattering by a submerged vessel with internal structures
Authors: Lu I-Tai , Yao Yuqi
Published: October 2005

This paper discusses a ray approach to analyze wave scattering by fluid-loaded targets (submarinelike structures). The approach consists of the following four elements: (1) modal analysis in separable structures (e.g., flat plate, cylindrical shell, spherical shell, etc.); (2) coupling of plate and shell modes at joints; (3) ray asymptotics and spectral approaches for separable structures; and (4) combination of the results in (2) and (3) for nonseparable structures. The model consisting of a cylindrical pipe with hemispherical endcaps, a bulk head and an internal rib, have been considered. Some computed results are compared with experimental data derived by a tank test at the NUSC facility using Mark 0 model. [Work supported by ONR.]
Influence of endcaps on mid-frequency scattering from finite cylindrical shells at axial incidence
Authors: Conti Matthew , Guo Y. P. , Dyer Ira
Published: October 2005

Experimental studies of mid-frequency scattering from cylindrical shell models at axial incidence have demonstrated the excitation of axisymmetric compressional and flexural waves within the endcap. The endcap discussed here consists of spherical and conical sections connected to the cylindrical portion of the shell model via slope discontinuities. Phase-matched coupling to compressional waves occurs on the spherical portion of the endcap. Scattering to both wave types occurs at the slope discontinuities. Conical shell dispersion equations developed by Guo are shown to match experimental observations. The Wigner transform is used to demonstrate these phenomena. Amplitude and group delay effects are discussed. The bistatic measurements were conducted over a frequency range of 2.5<ka<10.5, corresponding to 3/4 to 3 times ring frequency of the shells. [The authors acknowledge assistance of NRL for acquisition of data. Work supported by ONR.]