bluuebunny/crossref_metadata_2025 huggingface dataset:
Field measurements of the spatial coherence of surface and bottom interacting acoustic signals
Authors: Dahl Peter H. , McConnell Steven O.
Published: October 2005

The complex spatial coherence is a measure of the degree of similarity between signals received at different elements of an array. Field measurements of spatial coherence were obtained at a shallow water site in Puget Sound, Washington. Pulsed signals with center frequency ranging from 15–50 kHz were propagated 500 m through water 35 m in depth, and received at stationary vertical and horizontal line arrays. The received signals have a characteristic time dependence that relates to the impulse response of the channel, i.e., the sequential arrival of direct and bottom bounce paths (D + BB), single surface bounce (SB1), double suface bounce (SB2), etc. The complex coherence is computed using time windows that isolate the different paths by groups, e.g., the D + BB paths are isolated from surface interacting paths, and an estimate of coherence is derived by ensemble averaging over 50 pings. Also discussed is the dependence of spatial coherence on (1) normalized receiver separation (d/λ), (2) the deterministic ray paths as set by the basic channel geometry, (3) ray travel time fluctuations governed by changing environmental factors such as the sea state, and (4) array configuration. [Work supported by the Office of Naval Technology with technical management by NOARL, Code 240.]
Molecular dynamics of viscous flows
Authors: Banavar Jayanth R. , Ma Wen-Jong , Koplik Joel , Willemsen Jorge
Published: October 2005

Molecular dynamics techniques are used to study the microscopic aspects of several slow viscous flows past a solid wall, where both fluid and wall have a molecular structure. Systems of several thousand molecules are found to exhibit reasonable continuum behavior, albeit with significant thermal fluctuations. In Couette and Poiseuille flow of liquids it is found that the no-slip boundary condition arises naturally as a consequence of molecular roughness, and that the velocity and stress fields agree with the solutions of the Stokes equations. At lower densities slip appears, which can be incorporated into a flow-independent slip-length boundary condition. An immiscible two-fluid system is stimulated by a species-dependent intermolecular interaction. The local velocity field near a moving contact line shows a breakdown of the no-slip condition and, up to substantial statistical fluctuations, is consistent with earlier predictions of Dussan. [Work supported by NSF.]
Direct and inverse problems for pulse reflection from random media
Authors: Papanicolaou George C.
Published: October 2005

The reflection of pulsed acoustic waves from a layered random half-space is studied. A theorem that determines the local power spectral density of the reflected signal on the surface is given. From the structure of this power spectral density, slowly varying properties of the medium can be inferred. Extensive numerical computations that delineate the scope of the theory are presented.
Ultrasonic tissue characterization parameter presentations in three dimensions
Authors: Feleppa Ernest J. , Lizzi Frederic L. , Dumke Anne E. , Rosado Angel
Published: October 2005

Ultrasonic tissue characterization based on spectrum analysis of radio-frequency (rf) echo signals is proving to be clinically useful in ophthalmology and abdominal studies. Parameters computed using spectrum analysis can be theoretically related to scattering properties of tissue such as scatterer size and impedance and therefore to histology. Such parameters can also be correlated empirically with clinical features, histopathology, treatment history, etc. They appear to be useful for clinical evaluation of disease, particularly detecting, diagnosing, staging, and monitoring cancer. Although parameters can be presented graphically or numerically, two-dimensional parameter images significantly facilitate the interpretation provided by tissue characterization. The portrayal of parameters in three dimensions further enhances the visualization of parameter distributions, and provides an even more powerful tool for tissue evaluation. In addition, three-dimensional (3-D) presentations of the surfaces of tissue structures permit assessment of spatial relationships and quantitative estimation of volume. These methods have been applied fruitfully in a number of medical applications, including evaluation of intraocular tumors, cancers of the liver, clots and thrombi, skin lesions, and prostate tissue. [This research has been supported by NIH Grants EY01212, EY01480, CA38400, and RR05853.]
Measurement of consonant confusions by human listeners in whispered speech
Authors: Martin Doug
Published: October 2005

The acoustic differences between whispered and normally phonated speech are large; yet whispered speech is still very discriminable. Since replacing a periodic voicing source with an aperiodic excitation does not significantly affect perception, there exists the possibility of a central processing stage to augment the normal peripheral processing. In the present experiments, the 16 CV syllables used by Miller and Nicely (1955) are whispered by three male and three female talkers. The data are used to collect confusion matrices from listeners who discriminate among 64 sample syllables from each talker. Data are also collected with stimuli involving normal and loud speech, in an attempt to determine what, if any, acoustic cues might discriminate between the consonants across stimulus conditions. The consonant confusions are obtained using a multitalker babble as a masker. Babble is used instead of white noise because it should equally mask all speech stimuli, whereas white noise may mask some stimuli, such as fricatives, more than others. Probabilities of consonant confusions across the voicing dimension for whispered speech will be presented.
A long-range outdoor sound propagation model based on an analytical determination of the acoustical ray paths
Authors: L'Espérance A. , Herzog P. , Daigle G.
Published: October 2005

For short-range sound propagation problems, the acoustic energy reaches a remote receiver via a straight direct ray and a ground-reflected ray and the total pressure at the receiver can be precisely computed considering the geometrical spreading, the atmospheric absorption, and the ground effect [Piercy et al., J. Acoust. Soc. Am. 61. 1403 (1977)]. For long-range sound propagation problems, additional effects have to be considered: mainly, the refraction due to temperature and wind gradients that curve the rays and the turbulence that destroys the coherence between the rays. To evaluate the effect of refraction, a constant linear sound-speed gradient is assumed. This assumption allows an analytical determination of the curved rays and it also permits the determination of additional reflected rays that may appear in the presence of positive gradients, or of the position of the shadow zone in the presence of negative gradients. The total sound pressure at the receiver is computed by summing up the contribution from all the rays existing between the source and the receiver and, if the receiver is in the shadow zone, the diffraction solution of Berry is used [A. Berry and G. A. Daigle, J. Acoust. Soc. Am. 83, 2042–2058 (1988)]. The comparisons between theoretical and experimental results show the accuracy of the proposed model.
An automated method for matching a vocal fold contact area model to an EGG waveform
Authors: Titze Ingo R. , Liang Haixiang
Published: October 2005

Electroglottography (EGG) signals arc routinely used for observation of vocal fold adduction and regularity in vocal fold vibration. Analysis over many cycles can be very tedious if waveform parameters arc extracted manually or semiautomatically. A parameter optimization strategy is used here to provide a list fit to a model, thereby allowing larger volumes of data to be processed. Processing speed and reliability of extraction depend on the type of model being used and the cleverness in choosing the appropriate seed values. [Work supported by NIH.]
Ultra-high rate digital sampling: Jitter, shimmer, and spectral perturbation of speech
Authors: Yonovitz A. , Ostuni John
Published: October 2005

The glottal function was obtained through the use of a reflectionless tube. This tube acted as a pseudoinfinite termination of the vocal tract. Male and female speakers phonated a neutral vowel while target matching to a 125- and 210-Hz tone, respectively. The glottal waveform was digitized at 1 000 samples per second with a resolution of 12 bits. Each cycle was partitioned at an interpolated zero-crossing. This procedure provided an accurate determination of the period of each glottal pulse. The spectral content of each individual cycle was determined by discrete Fourier analysis. The amplitude and phase of the first 20 harmonics were determined for each cycle. These harmonics were utilized to determine separate perturbation values, as well as an overall amplitude measure. The data showed a systematic change in the spectral character of the sustained vowel source signal. Spectral perturbation analysis may be a more inclusive measure of waveshape changes than jitter or shimmer.
Noise at the glottis during speech production
Authors: Stevens Kenneth N.
Published: October 2005

Turbulence in the airflow near the glottis can result in the generation of noise, usually called aspiration noise. This noise can occur with or without vocal fold vibration, and can exist in conjunction with other sources of noise at constrictions above the glottis. Based on theoretical considerations, together with experimental data from speech acoustics and from models, a method has been developed for estimating the level, spectrum, and location of the aspiration noise source from knowledge of the glottal opening and the airflow. Some uncertainties remain in predicting the level of the source because of individual differences in airway configuration. Calculations of the radiated sound pressure for breathy voicing, for aspirated consonants, and for sounds with supraglottal constriction lead to absolute levels and spectra that are consistent with measured data for utterances from several speakers. These theoretical analyses can be used to aid in the development of improved methods for the systhesis of speech and for the interpretation of acoustic data from speech. [Work supported in part by a grant from the National Institutes of Health.]
Coarticulation effects in American English velar and alveolar stop consonants: An electropalatographical and acoustical analysis
Authors: Suzuki Noriko
Published: October 2005

Coarticulation effects of post-consonantal vowels on the place of tongue contact for American English velar and alveolar stop consonants were examined through simultaneous measurements with a new type of electropalatography (EPG) and with spectral analysis. The EPG system, developed by the author, has 49 electrodes, and is used to observe lingual contact with the soft palate, hard palate, and upper incisal teeth. It can record the palatograms at a 7.8-ms frame interval. The resulting palatograms can be compared with acoustic spectra made from simultaneous speech recordings. One American male subject produced VCV utternances in which the consonants were /k/, /g/, /t/, and /d/, and the vowels were /a/, /o/, /u/, /e/, and /i/. The results confirm that the tongue contact position for American English velar stop consonants is more strongly influenced by the vowels following it than for alveolar stop consonants. The value of F2 around the release burst was consistent with the strong coarticulation effects observed with the EPG.
Estimation of elasticity and viscosity parameters of muscles for speech production models
Authors: Wilhelms Reiner
Published: October 2005

In connection with a project on a dynamic three-dimensional tongue model, a constitutive description of tongue muscles is needed. This does not only include elastic coefficients, but also viscoelastic parameters of the inactive as well as for the activated muscles. A number of documented and published experiments were done on related areas, usually using different muscles, like muscular tissue of vocal folds, heart muscles, etc. Many of these used small elastic deformation as the underlying theory that only allows for linear stress-strain relations and small strains. A more general method for describing the elastic and myoelastic behavior is by a strain energy function for large deformation. The appropriate elastic parameters then are parameters in the strain energy function. This study describes a method to estimate the parameters from observation of the motion of several points on the surface of a free oscillating specimen.
The domain of laryngeal feature effects in Chonnam Korean
Authors: Jun Sun-Ah
Published: October 2005

This paper investigates the domain of two aspects of laryngeal features in the Chonnam dialect of Korean. In Korean, voiceless lenis stops, /p,t,k/, sometimes become voiced between voiced segments. Traditionally, this voicing has been discussed as occurring “within words.” However, word-initial lenis stops are sometimes voiced at fast tempo, suggesting that the domain is some prosodic unit such as the “accentual phrase” [S. A. Jun, J. Acoust. Soc. Am. Suppl. 1 85, S98 (1989)]. To test this, utterances of various constructions produced by three Chonnam speakers at three different tempi (slow, normal, fast) were recorded. An electroglottograph (EGG) was recorded simultaneously with the audio wave. In general, the audio waveform and EGG agreed: Either both showed voicing, or neither did. Only a few cases showed a discrepancy and, for almost all of these cases, the EGG data showed what was expected from the accentual phrasing. Since the number of accentual phrases within an utterance varied with the speech rate (the faster, the fewer), voicing also varied. Preliminary results of VOT measurements in aspirated stops show a similar effect of the accentual phrase boundary: VOT was longer at the beginning of an accentual phrase than medially. Thus the domain of all laryngeal feature effects seems to be the accentual phrase rather than the word.
Timing of upper lip protrusion gestures for the vowel /u/
Authors: Perkell J. S. , Matthies M. L.
Published: October 2005

Timing of upper lip protrusion gestures and accompanying acoustic events was examined for multiple repetitions of word pairs such as “lee coot” and “leaked coot” for three speakers of American English. The duration of the intervocalic consonant string was manipulated by using various combinations of/s,t,k,h,♯/. Pairwise comparisons were made of times of acoustic /i/ offset to acoustic /u/ onset (consonant string duration), protrusion onset to acoustic /u/ onset (onset interval), maximum acceleration to acoustic /u/ onset (acceleration interval), and acoustic /u/ onset to protrusion offset (offset interval). In spite of considerable token-to-token and cross-speaker variation, several general observations were made. There were some consonant-specific effects, primarily for /s/. The non-s subset evidenced two modes of behavior. (1) The lip protrusion gesture for /u/ had a relatively invariant duration, but its timing varied with respect to the oral consonant gesture complex: The longer the consonant string, the earlier the lip protrusion gesture, or (2) the protrusion gesture duration correlated positively with consonant duration. The mode 1, which predominated, the slope of the timing relationship between oral and labial gestures differed across subjects. [Work supported by NIDCD.]
Comparison of lip rounding in German and English vowels
Authors: Crabtree Monica , Kurz Claudia
Published: October 2005

Lip displacements in German and English vowels were compared in order to test two claims; first, that German rounded vowels are more rounded than their English counterparts [Disner, UCLA Working Papers in Phonetics No. 58 (1983)] and, second, that [y] is less rounded than [u] in German [S. Wood, J. Acoust. Soc. Am. 80, 391–401 (1986)]. Disner's claim is related to the idea that the number of contrasting vowels in a language affects the dispersion within the vowel space [Keating and Huffman, Phonefica 41, 191–207 (1984)]. The number of vowels may also constrain contextual variation due to consonantal environment in different ways in the two languages. This was also tested. Three native speakers of each language were videotaped saying four tokens of each vowel in their respective languages, in bilabial-alveolar context and in velar-alveolar context. Various measurements of upper and lower lip position were analyzed using ANOVA. Preliminary results indicate that German [u, U, o, ɔ] are indeed more rounded than English [u, U, o, o]. However, the results with respect to [y] do not support Wood's claim.
Effects of visual word stimuli on speech perception
Authors: Kondo Tadahisa , Kakehi Kazuhiko
Published: October 2005

The effects of visual word stimuli on speech perception in Japanese are investigated. An experiment is constructed to discriminate effects mediated by phonological and semantical codes of written words. Subjects are simultaneously presented with a visual word stimulus and an auditory word stimulus embedded in a short sentence. The recognition rates for a syllable in a spoken word, where the syllable is either replaced with white noise or has white noise added to it, are measured in various conditions in which various types of visual word stimuli are presented. Four types of visual word stimuli are used: (1) matching words, (2) nonword strings with the same pronunciation, (3) associative meaning words, and (4) nonrelative words in regard to auditory word stimuli. Additionally, non-character stimuli are used as a control condition. The mean syllable recognition rates for five conditions are in order of (1), (2), (3), control, and (4), from higher ones. The rates for (1) and (2) are significantly different from the rate for the control condition. Consequently, both phonological and semantical codes of visual words are important factors affecting speech perception.
Effects of speech intelligibility upon performance
Authors: Garinther Georges R. , Peters Leslie J. , Whitaker Leslie A.
Published: October 2005

The assessment of the ability of a talker to communicate with other persons, under given conditions, is normally accomplished by means of speech intelligibility testing. The resultant scores, however, do not provide any quantification of how well the communicating individuals performed the task at hand. An experiment was conducted in which professional military crews operated a tank simulator at five levels of speech intelligibility ranging from very good to extremely poor. Measures such as time to drive to an engagement location, number of targets hit, time to perform the entire mission, etc., were obtained. The results of this study will serve as a first step for establishing more realistic acoustical limits for military systems, guide the design of improved communication systems, and assist operations analysts in better defining war gaming parameters.
Effects of masker fluctuations, number of maskers, and reverberation on binaural speech perception in normal and impaired hearing
Authors: Bronkhorst Adelbert W. , Plomp Reinier
Published: October 2005

Binaural speech-reception thresholds (SRT) in noise for both normal-hearing and hearing-impaired listeners were determined (1) using earphone presentation of stimuli simulating a free-field environment with between one and six noise sources, and (2) in a reverberant environment with the listener in either the direct or indirect field of the speech and/or noise source. The masking noise was either steady state, or modulated like running speech. It was found that normal-hearing listeners benefit considerably from both masker fluctuations and interaural level differences due to headshadow: Both cues caused an advantage of up to 7 dB in terms of SRT. Much smaller gains were attained by most hearing impaired listeners. The gains also diminished when reverberation was present, or when the number of maskers was increased. Results further showed that in almost all conditions where interaural time or phase differences were present, the release from masking experienced by both normal-hearing and hearing-impaired listeners was in the order of 2–3 dB.
Computation of the reciprocal network parameters of a piezoelectric transducer using the ATILA finite-element code
Authors: Brown M. W. , McLean K. A. , Kuntsal E. , Baker S. R. , Wilson O. B.
Published: October 2005

The ATILA finite-element code [Decarpigny et al., J. Acoust. Soc. Am. 78, 1499 (1985)] has been used to compute the reciprocal network parameters for several piezoelectric transducers. These are, for example, the blocked electrical impedance, the open-circuit acoustical impedance, and the transduction coefficient. Also computed were the acoustical radiation impedance and the diffraction constant. The procedure used, and the results of some comparisons with experimental data, will be described. [Work supported by NRL-USRD and the Naval Postgraduate School.]
Fiberacoustic sensor embedded in a composite
Authors: Yin Ai-guo , Varadan Vijay K. , Varadan Vasundara V.
Published: October 2005

This paper presents a discussion of multimode optical fibers used for acoustic wave (2–10 MHz) propagation. The optical fiber acts as a connecting rod between two piezoelectric transducers (PZT) that are attached at each end (dumbbell arrangement). This device is then completed by encapsulation of a solid epoxy or a strengthened composite. One piezoceramic is excited and generates an elastic wave to propagate along the optical fiber and into the other piezoceramic. An alteration of the steady-state signal thus is indicative of an impact and/or random pressure disturbances upon the composite. Additionally, environmental temperature changes are also detectable. Experimental measurement and related theories are demonstrated.
Optimum unequally spaced linear array
Authors: Lan Jun , Varadan Vijay K. , Varadan Vasundara V.
Published: October 2005

An entirely new method for designing an unequally spaced linear array—successive approximation method—has recently been developed. This analytical technique permits the sidelobe level of the directivity function to be minimum by adjusting all of the sidelobes to equal heights. Computations display the sidelobe levels of optimum unequally spaced arrays to be much lower than those obtained using other methods. Optimum unequally spaced linear arrays offer several advantages over conventional amplitude shaded linear arrays. These include simple technology, narrow beamwidth, and high sensitivity for identical sidelobe levels. Practical optimum unequally linear arrays have been fabricated and experimental results are consistent with computed expectations.
Heliport noise contours with and without a penalty for induced building rattle
Authors: Luz George , Letty Richard
Published: October 2005

The debate over whether a penalty should be added to the A-weighted noise level of helicopters to account for the added annoyance of building rattles induced by blade slap is long-standing. Recent evidence suggests that the decision to add a penalty should depend on the type of construction in the area subjected to the noise. An implication for community planners is that noise contour maps should be presented in two forms: with and without a penalty, thus allowing the planners to decide whether building codes to reduce rattle should be enforced for new development. Examples from two Army airfields are provided to demonstrate the advantages and disadvantages of this process. On-site noise monitoring data are also presented to confirm the accuracy of the unpenalized noise contours.
A proposed highway noise criterion based on the difference between intrusive and background sound levels
Authors: Solomon Sheryl R. , Tocci Gregory C. , Cavanaugh William J.
Published: October 2005

The Federal Highway Administration's “Highway Noise Abatement Criterion” uses the peak hour equivalent sound level for setting limits in highway noise impact studies. In studies conducted by Cavanaugh Tocci Associates, Inc., it has been observed that the FHWA criterion is generally adequate during the day when the traffic mix is such that traffic sound levels are relatively uniform with time, i.e., when the difference between the intrusive sound levels (defined here as the 1 percentile level, L01) and the background sound levels (defined here as the 90th percentile level, L90) are less than 10 dBA. At night, although the FHWA traffic noise criterion remains satisfied, the difference between the L01 sound levels produced by truck passbys and the L90 sound levels significantly exceed 10 dBA. Once this 10-dBA margin between the L01 and the L90 sound levels is exceeded, community response to traffic noise is affected. This large difference between the intrusive and background sound levels seems to explain the “but I can still hear the trucks” syndrome. This experience suggests that highway noise acceptability criteria and environmental impact assessments should also include a limit on the difference between intrusive and background sound levels. Preliminary criterion limits based on studies to date are described.
An exact solution of the (Helmholtz) Weyl composition equation in underwater acoustics
Authors: Fishman Louis
Published: October 2005

Phase space and path integral methods have been applied to both mathematical and computational direct and inverse wave propagation modeling at the level of the scalar one-way Helmholtz equation. These methods are particularly appropriate for extended, strongly inhomogenenous, multidimensional channeling environments. Operator symbols play a pivotal role in the analytical constructions and numerical algorithms. The construction of the operator symbol requires the exact (or approximate) solution of the (Helmholtz) Weyl composition equation in the Weyl pseudodifferential operator calculus. The exact symbol for the profile K2(q) = K02 + A tanhρq + B sech2 ρq is constructed and briefly analyzed. This family of profiles is particularly appropriate for ocean seismo-acoustic modeling, as it includes (1) both symmetric and asymmetric wells with trapped modes and (2) sharp gradient features. Two limiting cases are the delta and discontinuity profiles. The results are used to illustrate several points pertinent to wide-angle propagation modeling and the refractive index profile reconstruction problem. [Work supported by NSF, AFOSR, and ONR.]
A three-dimensional time-domain paraxial approximation for underwater acoustic wave propagation
Authors: Orchard B. J. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

One-way narrow- and wide-angle three-dimensional time-domain paraxial approximations to the wave equation are developed to model acoustic propagation. The approximate equations are designed to be appropriate for ocean applications including pulse propagation with dissipative volume attenuation and variable density. First, pseudodifferential equations for acoustic pressure are obtained from a thermodynamic model, which incorporates attenuation due to the presence of multiple acoustically absorbing chemical species. Comparisons are made to corresponding results obtained from the phenomenological model of Stokes. Padé approximants and the method of multiple scales are then used to generate partial differential equations with paraxial characteristics. Appropriate boundary, initial, and interface conditions are described for the model equations. Analytical expressions for pulse-type solutions to a special case of the narrow-angle equation are obtained which demonstrate some of model's properties and restrictions. Stability of the narrow-angle approximation is demonstrated by means of an energy integral. [Work supported by ONR.]
An investigation of sound ray dynamics in a range-dependent model of the ocean volume using an area preserving mapping
Authors: Brown Michael G. , Tappert Frederick D. , Goni Gustavo J.
Published: October 2005

An area preserving mapping that describes sound ray propagation in a simple range-dependent ocean sound channel is derived and studied. The unbounded ocean model has a bilinear sound-speed profile in which the vertical sound-speed gradient above the sound channel axis varies sinusoidally in range. It is assumed that the scale of the range-dependent perturbation is small compared to a typical upper loop length of a ray. The explicit mapping that results gives successive iterates of range and upgoing ray angle at the sound channel axis, (rn, θn) → (rn+1,,θn+ 1). The degree of stochasticity of the mapping is governed by a single dimensionless parameter ε—the strength of the range-dependent perturbation. Iterates of the mapping indicate that only a small fraction of all ray trajectories are chaotic, i.e., exhibit extreme sensitivity to initial conditions, for perturbations comparable in strength to those produced by internal waves in the ocean. The chaotic nature of these rays is confirmed by the calculation of positive Lyapunov exponents.
Stable and accurate interface conditions for wide-angle parabolic wave equations
Authors: Sundström Arne
Published: October 2005

The proper formulation of mathematical and numerical conditions at a fluid/elastic interface is studied for the standard and higher-order parabolic wave equations. For wide-range integrations in shallow oceans, the amplitude and phase error of the bottom reflection coefficient and the error growth of the scheme must be as small as possible. Schemes with minimal local error and error growth are given, both for the usual parabolic wave equation, the higher-order variants based on Padé approximations, and the shallow-water variants suggested by Collins [J. Acoust. Soc. Am. 86, 1097–1102 (1989)].
Marching and spatial-spectral filtering of localized phase-space representations of wave fields in layered media
Authors: Steinberg B. Z. , McCoy J. J.
Published: October 2005

Spatial and spectral (directional) information of the wave data are of equal importance in the analysis and synthesis of wave phenomena. Their simultaneous collaboration in a phase-space format may be achieved by incorporating windowing techniques into (conventional) spectral integrals. The result is a local-spectral representation of the field that is concentrated inherently around physically meaningful regions in phase space. This representation is most naturally suited to perform simultaneous spatial and spectral processing of wave data and therefore may serve as a powerful tool in a variety of applications such as remote sensing, imaging, field reconstruction, and more. In this work a method to propagate the local spectra of wave fields through plane stratified media is developed and discussed. An adaptive marching algorithm that permits control of the localization process will be presented. The ability of the new scheme to perform simultaneous spatial and spectral data filtering of wave phenomena, and its resolving power in phase space, will be discussed and demonstrated by means of numerical examples.
Linear density-reciprocal sound velocity relationships for two continental shelf surface sediment classes
Authors: Ioup Juliette W. , Rayborn Grayson H. , Ioup George E.
Published: October 2005

The density to reciprocal sound velocity dependence of two predominant classes of continental shelf surface sediments as measured by Hamilton [J. Acoust. Soc. Am. 68, 1313–1340 (1980)] can be described as a subclass of Nobes's cases [J. Acoust. Soc. Am. 86, 290–294 (1989) ] by the Wood equation [Wood, A Textbook of Sound (Macmillan, New York, 1941)] or by straight line fits to the Wood equation or the data [J. Acoust. Soc. Am. Suppl. 1 80, S113 (1986)]. The data classes can be characterized as sand-silt and clay-sand-silt. Although the Wood equation is nonlinear in density versus reciprocal sound velocity, for the porosity domain of these sediments it is nearly linear, as are the measured data. Also a linear relation may be derived from the Wood equation by doing a Taylor series expansion about the midpoint velocity-density value for each sediment type. These results can be used to choose model study parameters, to calculate sediment densities from shipboard measured sound speeds, or to estimate average grain densities and velocities from measured bulk sediment densities and sound speeds. [Work supported by the Naval Oceanic and Atmospheric Research Laboratory through the U.S. Navy-ASEE Summer Faculty Research Program and through Grant No. N00014-89-J-6002.]
Friction-induced sounds—Wineglass acoustics revisited
Authors: Daly Mark A. , Akay Adnan
Published: October 2005

In an effort to understand the mechanisms of friction-induced sounds, radiation from a wineglass excited by a violin bow has been investigated. Experiments on the vibration response of a glass shows the existence of an important dependence between the friction force and the vibration response of the glass. It is shown that under certain conditions there is a lock-in mechanism between the friction force and the glass response that leads to radiation at a particular natural frequency of the glass and its harmonics. An analytical model predicting the vibration response of a wineglass is presented. [Work supported by NSF and Institute for Manufacturing Research at Wayne State University.]
Resonant response of curved beams
Authors: Charpie James P. , Burroughs Courtney B.
Published: October 2005

A mix of formulations and solution techniques is used to determine and compare the vibration response of curved beams. This investigation is extremely analytical. Bernoulli-Euler formulations for beams of constant and variable radii of curvature are solved by both the Galerkin and Rayleigh-Ritz methods and a Timoshenko formulation is solved by the Rayleigh-Ritz method. Results include the mode shapes as well as the natural frequencies. Both the formulations and the results are shown to reduce to their proper analogs for straight beams. All formulations allow extension of the beam's centerline. The viability of the “inextensibility assumption” is investigated. Order-of-magnitude scaling of the differential equations is used to identify dominant curvature terms. Changes in resonance frequencies and mode shapes with beam curvature are explored. Sudden jumps in mode shapes with small changes in curvature are shown and discussed.
Sound wave propagation through multiphase materials
Authors: Schwarz W. H. , Marguiles T. S.
Published: October 2005

Theories for infinitesimal, planar sound wave propagation in a dilute suspension of rigid particles in a viscous fluid has been investigated by generally three approaches: (1) wave scattering, (2) hydrodynamic, and (3) ad hoc approaches specific to particular systems. Here, a hydrodynamic development that uses spatially averaged continuum balance and constitutive equations for multiphase materials is presented. Two alternative approaches derive equivalent results (i.e., a bicubic polynomial equation) for the complex propagation constant χ = − (a + ik), where a is the spatial attenuation coefficient and k is the wavenumber. One approach uses linear momentum equations for each individual phase, while the other uses an overall linear momentum equation and a relative momentum equation, obtained by taking the sum and difference of the individual momentum equations for the continuous and particulate phases. The advantage of this latter aproach is that it expresses the results in the form of a generalized Fick's law, and expresses the diffusion of particles, as well as the supply terms such as barophoresis, thermophoresis, and pycnophoresis, explicitly. Furthermore, an Einstein relation can be obtained by simply defining a diffusion coefficient, and interpreting this coefficient in the linear momentum supply term that is proportional to the relative velocity as a Stokes viscous drag force.
Measurement of tortuosity of porous materials and implications for acoustical modeling
Authors: Champoux Yvan , Stinson Michael R.
Published: October 2005

Tortuosity is one of several physical parameters required by various theoretical models to characterize the acoustical behavior of a porous material. In this paper, an experimental system that permits rapid and convenient measurement of the tortuosity of materials is described. A five-terminal conductivity technique is applied to samples of porous material saturated with an electrolyte. Measurements of voltages between three judiciously installed inner electrodes (silver wire), coupled with independent measurement of sample porosity, are sufficient to determine the tortuosity. The current electrodes are different than the voltage terminals, so voltage drops associated with the electrochemical processes at these electrodes are not important. Consequently, the measurements of tortuosity are not affected by the amount of current used or the conductivity of the electrolyte. Experimental results, using several calibration samples with known tortuosity, confirm that tortuosity can be measured using this approach with a 2%–3% accuracy. Acoustical measurements (characteristic impedance and propagation constant) on a model porous material having pores of varying cross-sectional area are used to illustrate the importance of using the measured tortuosity in application of theoretical models.
Measurements of elastic constants of ceramic composites using ultrasonic plate mode antiresonances
Authors: Wang W. , Rokhlin S. I.
Published: October 2005

With oblique incidence of an ultrasonic wave upon a thin anisotropic plate immersed in fluid, in general the quasilongitudinal, flexural, and quasi-SH vibrations are excited. At some angles of incidence, coherent interactions of these waves lead to antiresonance-type minima of the normal displacement on the back surface of the plate and therefore to minima of the transmission coefficient. At off-axis orientations of the thin anisotropic plate relative to the incidence plane, several minima may be found. One of them may be used for shear modulus measurement. The measurements have been performed on (1) a porous aluminum oxide membrane, which is transversely isotropic in the plane of the membrane, and (2) a unidirectional SiC/Al composite membrane, where the fibers lie in the plane of the plate. The elastic constants were extracted from the experimental data by a nonlinear least-squares optimization technique. It is demonstrated that the method gives very good results for determination of in-plane longitudinal and shear moduli.
A new objective speech quality measure for speech coding systems
Authors: Barnwell Thomas P.
Published: October 2005

This paper presents a new objective measure for speech quality testing to be used with speech coding systems. This measure is presented in the context of an ongoing 15-year study of objective measures for speech quality. As part of this research, well over 3000 measures have been evaluated in a study that has done well over a million separate correlation analyses. Included in the study were parametric forms of virtually all commonly used objective measures as well as a large number of new, complex composite measures. The new objective speech quality measure to be presented is a composite measure based on the line spectrum pair (LSP) decomposition of the linear predictive coding (LPC) polynomial. The measure is intended specifically to be used for the design of LPC quantizers for use in a wide variety of speech coding systems. This new measure is the first measure developed in this research that has both very high performance in terms of its ability to predict listener subjective responses as well as the properties necessary to be used explicitly in the design of LPC quantizers.
Physiological models of masking and speech processing
Authors: Delgutte Bertrand
Published: October 2005

Auditory models might be applied to speech coding either as objective evaluation measures, or as coder stages in coder/decoder systems. Both applications are based on the premise that these models accurately represent all the information that is relevant to auditory perception. In this talk, two fundamental problems that need to be worked out in order to make auditory models practically useful in speech coding are identified: the choice of a distance measure for comparing model outputs, and the design of the decoder. These ideas are illustrated using a model of peripheral auditory processing that is based on physiological recordings from auditory-nerve fibers, and predicts psychophysical performance in masking and discrimination for a variety of stimulus conditions. In this model, intensity difference limens in restricted regions of the frequency spectrum depend on overall spectral shape and sound level, so that the coding accuracy in different frequency bands would have to vary with time. Model outputs will be compared for natural and coded speech, and the role of nonlinear phenomena in the inner ear (such as two-tone suppression ) will be discussed. [Work supported by NIH Grant NS13126.]
On the estimation of the acoustic surface impedance of layered porous materials
Authors: Lauriks W. , Allard J. F. , Cops A.
Published: October 2005

The acoustic impedance of layered porous materials can be calculated using the Biot theory and a matrix formalism to characterize each layer. A comparison with experimental data will be made for layered systems of various types, including layered systems covered with a membrane. The experimental data have been obtained with a two-microphone technique, which calculates the acoustic impedance from pressure measurements at two different microphone locations above the sample.
Mechanisms causing narrow-band sounds associated with aneurysms and arterial lesions
Authors: Mast T. Douglas
Published: October 2005

Many investigators have reported sounds of nearly pure tone, with frequencies of the order of 500 Hz and Q's of the order of 20, associated with flow in human carotid and cerebral arteries. These sounds are apparently caused by vascular lesions, but there is not yet a satisfactory explanation. Olinger and Wasserman [Surg. Neurol. 8, 298–312 (1977)] advanced the hypothesis that aneurysms act as Helmholtz resonators. Simple order of magnitude calculations support this hypothesis, but the resonator's acoustic compliance must be associated with wall elasticity, rather than fluid compressibility. Aaslid and Nornes [J. Neurosurg. 60, 32́36 (1984)], using angiography and Doppler flow velocimetry, found no tangible link between narrow peaks in the spectrum of fluctuations in the flow velocity and the presence of aneurysms. They postulated instead that the peaks are due to periodic vortex shedding; the vortex-shedding hypothesis is supported by a strong dependence of frequency of spectrum peaks on blood flow velocity. The present paper addresses the question of whether such narrow-band sound can result solely from mechanisms of a fluid mechanical nature that do not involve the elasticity of the arteries. An alternate mechanism is also discussed involving weakened elastic spots or patches on the arterial walls that have intrinsic resonance frequencies. [Work supported by the William E. Leonhard endowment to Pennslyvania State University. The author acknowledges the advice of A. D. Pierce.]
Temperature distribution at tissue-bone interface generated by a focused Gaussian ultrasonic beam
Authors: Wu Junru , Du Gonghuan
Published: October 2005

When a focused Gaussian ultrasonic beam in soft tissue normally impinges on the boundary of a contiguous bone, reflection and transmission occur. Taking account of the reflection, the steady-state temperature elevation along the beam axis generated by the ultrasonic beam has been calculated. The effects of reflection, focusing, and perfusion will be discussed in detail. [Work supported by the American Cancer Society (IN-156) and by NSF and Vermont Epscor.]
A diffraction beam used for ultrasonic local heating expressed as the superposition of Gaussian beams
Authors: Byrne Richard , Wu Junru
Published: October 2005

Spatially uniform temperature elevation at a target inside a body is desirable for ultrasonic hypothermia and other medical applications. It has been shown for the two-dimensional case [Hynynen et al., Ultrasound Med. Biol. 7, 397 (1981)] that a “volcano”-shaped acoustic intensity profile is ideal for achieving such a temperature distribution. To generate this intensity distribution, the velocity at the surface of the transducer is found to be described by a Bessel-type function by an inverse Hankel transformation. The diffraction beam generated by the transducer can also be expressed as the superposition of Gaussian beams [M. A. Breazeale and J. J. Wen, J. Acoust. Soc. Am. 83, 1752–1756 (1988)], which are better suited for calculation of temperature elevation. The results of acoustic intensity distribution of the superpositon of Gaussian beams will be compared with those of the Bessel-type function. [Work supported by the American Cancer Society (IN-156) and by NSF and Vermont Epscor.]
The detection of microbubble radius versus time and some comparisons with theoretical results
Authors: Xu Qihong , Apfel Robert E.
Published: October 2005

Based on the fact that the scattering strength of both a gas bubble and a void is proportional to the ka, where k is the acoustical wavenumber and a is the radius of the scatterer, a driving transducer with 755-kHz frequency was used to produce cavitation in water, and a transducer with a 30-MHz center frequency worked as an active detector (pulse-echo). The active detector sends a series of the tone bursts and receives the signal backscattrered by transient cavitation produced by the 755-kHz transducer. Bubble radius versus time from which the duration of the bubble's growing can be extracted can be estimated by demodulating the backscattered signal. Using the model of the gas-filled cavity, the collapse time τ for the model will be [E. A. Neppiras, Phys. Rep. 61(3), 159—251 (1980)] τ = 0.915Rmax (ρ/Pm) (1 + Q/Pm), where Pm and ρ are the pressure and density in the liquid and Q is the pressure in the bubble at the maximum bubble size. The maximum bubble radius Rmax was estimated using the measured value of τ and was compared with earlier numerical results [H. G. Flynn and C. C. Church, J. Acoust. Soc. Am. 84, 985–998 (1988)] for the same peak acoustic pressure as in the experiment. [Work supported by NIH through Grant No. 5-RO1-CA39374.]
Frequency response of headphones measured in free field and diffuse field by loudness comparison
Authors: Ueda Kazuo , Hirahara Tatsuya
Published: October 2005

Coupler measurement of headphone frequency response may be incorrect at high and low frequencies [T. Hirahara and K. Ueda, J. Acoust. Soc. Am. Suppl. 1 87, S142 (1990)]. Since sound pressure near the eardrum is difficult to measure physically, a psychophysical method was employed to assess real ear frequency response of headphones. Loudness comparisons were performed by four subjects, under two experimental conditions: free field (anechoic room) and diffuse field (reverberation room). These conditions were run to check the influence of field characteristics on the reliability of the measurements. Each subject adjusted the headphone level of critical band noise bursts until they were equally loud as those from a reference loudspeaker (7 dB SPL). Measurement scatter was smaller in the diffuse field than in the free field. One hypothesis to explain this result is that head movement causes less change in level in a diffuse field than in a free field. Support for this comes from measurement of the SPL distribution in the two rooms, which revealed that the sound-pressure variation was smaller in the diffuse field than in the free field. To examine the reliability of loudness judgments at high frequencies, another method—hearing thresholds by Békésy tracking—was employed. Each subject's threshold was measured with both loudspeakers and headphones. After compensation was made for loudspeaker transfer functions, headphone frequency response was deduced from the results. This method led to high-frequency responses similar to those from loudness comparison. Below 6 kHz, however, there were only slight differences, because equating loudness for loudspeaker sound and for headphone sound does not strictly correspond to equal sound pressure at the eardrum.