bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic frequency spectrum shifts in failing artificial hearts
Authors: Choudhri Asim , Salehizadeh Bijan , Levin Howard , Oz Mehmet
Published: July 2002

Left ventricular assist devices (LVAD) are implantable mechanical blood pumps providing circulatory assistance for patients in heart failure, and are currently being investigated as a long-term alternative to cardiac transplantation. While effective in short term use as a bridge to transplantation, the durability of the device for extended use has yet to be demonstrated. To prospectively follow the mechanical status of the devices, biweekly transabdominal acoustic readings from a standard microphone and accelerometer are obtained. Time-domain analysis of the recordings allows the timing of ejection (device systole) and passive filling (device diastole) to be measured. Ejection duration was measured at 240 ms in 11 new devices and exceeded 300 ms in two aging devices which subsequently failed within 3 weeks of measurement. Frequency-domain analysis showed the presence of a 230-Hz signal in both failing devices, possibly indicative of bearing wear within the motor. In addition, a 50-Hz signal present in all properly functioning devices was missing in one of the devices which failed. Acoustical analysis will play a vital role in the continuing care of LVAD patients and will allow a more rapid and noninvasive method of assessing device status.
W. D. Ward as musical acoustician, journal editor, and reviewer
Authors: Martin Daniel W.
Published: July 2002

W. Dixon Ward’s musical talent as an expert pianist and a singer, combined with experience and training in both psychology and physics, provided the background for his significant doctoral research on pitch at Harvard University; for subsequent research in musical acoustics at the Baldwin Piano and Organ Company; and for continuing research in musical sound throughout his career. Twice Dix served the Journal as an associate editor for psychological acoustics. He peer-reviewed many Journal articles in psycho-acoustics, musical acoustics, and noise. He reviewed numerous books, and served on acoustical standards committees including acoustical terminology.
Pitch accent, phrase tones, and vowel devoicing in Tokyo Japanese
Authors: Kitahara Mafuyu
Published: July 2002

In Tokyo Japanese, short high vowels devoice between voiceless consonants, which conflicts with the realization of pitch accent. The fundamental frequency around the devoiced region in a corpus of 12 speakers was measured to investigate if and how speakers compensate for the loss of information normally conveyed by the pitch accent. Previous studies revealed that elevation and abrupt pitch fall immediately after the devoiced region is characteristic of utterances containing a devoiced accented syllable. However, preliminary analyses of these data show the occurrence of the characteristic pitch pattern after a devoiced region is dependent on the pitch height before the devoiced region. If two syllables are consecutively devoiced and the first one bears an accent, the pitch elevation only occurs when the antepenultimate syllable has a low phrase tone. This suggests a nonlocal pitch adjustment exists dependent on the occurrence of devoicing and the location of phrase tones. This also implies that vowel devoicing is not just a low-level consonantal effect, but has a long distance impact on the execution of phrasal pitch contours.
Lexical stress and metrical stress in auditory word recognition
Authors: Soltano Emily G. , Slowiaczek Louisa M.
Published: July 2002

Three experiments examined the influence of word stress in spoken word recognition. Experiments 1 and 2 investigated the role of lexical stress on response times in lexical decision and shadowing tasks. Primes and targets shared lexical stress patterns (e.g., BIBlical—JUVenile) or did not (e.g., deFENDed–JUVenile). The results did not support an influence of lexical stress in word recognition. Experiment 3 used a shadowing task, in which metrical stress was manipulated. Metrical stress defines weak syllables as containing schwa and strong syllables as containing all other vowel sounds. Primes and targets shared metrical stress patterns (e.g., resist–cigar) or did not (e.g., hostile–cigar). Targets with strong first syllables were shadowed faster than targets with weak first syllables. Moreover, the type of first syllable (weak or strong) interacted with whether the prime and target had the same metrical stress pattern; responses were faster when the target had a strong first syllable and the prime-target metrical stress patterns matched compared to all other conditions. These data provide converging evidence for the view that metrical stress and not lexical stress influences word recognition. [Work supported by Grant No. NS29286 from NIH.]
Dispersion estimates for bubbly seawater
Authors: Goodman Ralph R. , Caruthers Jerald W. , Elmore Paul A.
Published: July 2002

In April 1995, the Naval Research Laboratory performed high-frequency direct-path experiments in shallow water, near Panama City. During that period there were two days of strong weather which gave rise to slower sound speed, larger fluctuations over a few seconds, and dispersion. It led to the conclusion that only the presence of bubbles could cause these changes. The experimental results will be published soon. In an effort to understand these changes, analytical and numerical analyses were undertaken. Straightforward dispersion theory, based on the change of impressibility gives an integral expression that is a function of frequency and bubble distribution. It was found that there is a simple, exact integration for the case where the distribution of bubbles of radius a is given by the inverse of fourth power, a−4. Numerical studies have been performed that can be used to compare dispersion for other powers, from a−3 to a−5. The analyses give insight into the role that void fraction, bubble sizes, and their distribution play in dispersion. The analyses exhibit, as well, the sensitivity to accuracy that would be required if dispersion is to be used to determine the distribution of bubble size in the sea. [Work supported by NRL.]
Congruence of articulatory and acoustic variability
Authors: Faber Alice , Brown Julie M.
Published: July 2002

Johnson et al. [J. Acoust. Soc. Am. 94, 701–714 (1993)] suggest, on the basis of observed inter-speaker variability in discriminant analyses of articulatory measures, that speakers utilize acoustically defined targets in speech production. The present paper compares inter-speaker variability in simultaneously recorded acoustic and articulatory data (s–t words) from five New England speakers. The articulatory data were x and y coordinates of coils on the tongue, lips, and jaw, transduced by the Haskins Laboratories EMMA system and recorded at three locations in the target vowel; acoustic data were F1, F2, and F3 measures at the same temporal locations. Discriminant analyses of the articulatory and acoustic data sets reveal congruent patterns of inter-speaker variability in the two domains. The inter-speaker differences do not reflect superficial dialect or idiolect differences (e.g., extent to which /■/ and /■/ contrast, or tendency to glottalize syllable-final /t/). Rather, they reflect differences in the way subjects vary jaw position, especially height, suggesting an anatomical basis for the observed differences. Thus, within the limits of their oral morphology, these speakers are using comparable articulatory targets for speech sounds.
Singular value decomposition for normal-mode computations
Authors: Kessel Ronald T. , Dawson Trevor W.
Published: July 2002

Mode models of sound propagation in layered media begin with a search for modes in the complex wave-number plane, followed by computation of the vertical mode functions and mode superposition. Sound propagation modelers would like to search for modes ever more efficiently and thoroughly. The search amounts to the mathematical problem of finding the roots (zeros) of a complex-valued function—a problem that defies definitive solution. Rather than reducing the numerical test for modes (roots) to a single characteristic equation, singular value decomposition (SVD) can be used to test when the global matrix describing the propagation of plane waves through the layered media is singular, which is an equivalent condition for a mode. The advantages of this approach are that it is numerical stable, it automatically gives the vertical mode functions (although un-normalized), it can detect duct and interface modes at any depth, and it can identify and resolve close-mode pairs (double roots) and their antisymmetric mode functions occurring in weakly coupled sound channels.
Acoustic mode decoupling via environmentally adaptive coordinates
Authors: Mignerey Peter C.
Published: July 2002

A normal mode expansion is used to relate the coupling of energy between modes to horizontal derivatives of the eigenfunctions. A curvilinear coordinate system is constructed using a WKB approximation for a reference eigenfunction such that horizontal derivatives causing coupling vanish. The curvilinear coordinate system is defined such that constant surfaces of the vertical wave number integral coincide with surfaces of constant curvilinear depth. Thus any particular zero of an eigenfunction lies on a constant depth surface in the curvilinear system. The horizontal derivatives of all other modes depend on a ratio of vertical wave numbers with the reference mode. Nearly constant horizontal behavior of this wave number ratio supports the decoupling of all modes in the curvilinear system. Such coordinate systems naturally adapt to the environment even with realistic sound-speed profiles that include discontinuities as well as sloping bottom bathymetry. They provide an adiabatic normal-mode basis for constructing acoustic models in the fully three-dimensional environments of continental shelf regions. Environmentally adaptive coordinate systems also provide a rational basis for interpolating three-dimensional environmental data.
Auditory perception and plasticity in the avian auditory system
Authors: Dooling Robert J. , Ryals Brenda M.
Published: July 2002

Auditory perception plays a crucial role in a variety of avian behaviors including individual and species recognition, mate selection, territorial defense, song learning, and predator detection. Because the premium on hearing well is high, birds provide a window on the evolution and adaptation of auditory systems to different environments. The auditory perceptual capabilities of the avian auditory system are reviewed with special emphasis on the discrimination, recognition, and learning of complex sounds including species-specific vocalizations. These processes in birds are no where more plastic than when they subserve vocal development and learning. Because birds regenerate hair cells in the inner ear following damage, they also provide a unique opportunity to examine the return of auditory perception and the precision of vocal production and vocal learning following replacement of the auditory epithelium in an adult organism. Results of these studies are relevant to the perception and learning of speech sounds in humans and to the application of auditory prosthetic devices in humans. [Work supported by NIH Grant Nos. DC-00198 and MH-00982 to RJD and DC-01372 to RJD and BMR.]
Vowel perception and neural plasticity in cochlear implant users: The effect of more-basal-than-normal stimulation
Authors: Svirsky Mario A.
Published: July 2002

Because formant frequencies are a crucial cue in identifying English vowels, some pulsatile multichannel cochlear implants attempt to deliver formant frequency information by stimulating different electrodes depending on instantaneous formant values. For users of these cochlear implants, it may be possible to predict performance in vowel confusion studies based on the subject’s ability to discriminate different electrodes. One possible confounding factor is that cochlear implants stimulate cochlear locations that are more basal than normal (i.e., associated with higher frequencies). To what extent is this more basal-than-normal stimulation a problem? Is it important to stimulate the ‘‘physiologically correct’’ places in the cochlea, or (to state a diametrically opposed hypothesis) is the place code infinitely plastic? A mathematical model of vowel perception with cochlear implants is proposed that explicitly tests both hypotheses. The model attempts to predict a postlingually deaf subject’s vowel confusions based on his electrode discrimination and on his ‘‘perceptual bias’’ (meaning, in this case, the extent to which he has adapted to more-basal-than-normal stimulation). The conclusion is that more-basal-than-normal stimulation of the cochlea degrades speech perception shortly after implantation, but becomes less critical as subjects adapt to the new location.
The radiated noise from realistic airfoils encountering vortical gusts
Authors: Lockard David P. , Morris Philip J.
Published: July 2002

The long-term objective of the current research is to use computational aeroacoustics (CAA) methodology and parallel computers to increase the understanding of broadband blade noise. In a previous paper by the authors [D. P. Lockard and P. J. Morris, AIAA-97-0286 (1997)] the effect of thickness on the sound radiated by airfoils encountering incompressible, vortical gusts was investigated. This work extends those calculations by examining the effect of camber on the radiated noise. A two-dimensional, Navier-Stokes code, implemented using the message passing library and FORTRAN 90 on the IBM SP2, is used to perform the calculations. The code uses Runge-Kutta time integration and seven-point, central-difference, dispersion-relation-preserving spatial operators. A multigrid method is used to obtain converged steady-state solutions before the gust is introduced in a source region inside the domain. [Work supported by NASA Langley Research Center.]
Application of a parallel three-dimensional nonlinear method to the acoustics of flow-over cavities
Authors: Liu Jingmei , Long Lyle N.
Published: July 2002

A three-dimensional computational aeroacoustics (CAA) method combined with advanced parallel computing techniques is applied to the simulation of the acoustic response of flow-over cavities (Helmholtz resonator). Direct numerical simulation is conducted by solving a newly developed nonlinear disturbance equation [Morris et al., Comp. Phys. (in press)] which consists of linear and nonlinear fluctuation terms, spatially varying coefficients that depend on the mean-flow properties, and a mean-flow source term that is independent of the fluctuations. The mean-flow component is obtained from a numerical solution of the Reynolds-averaged Navier–Stokes equations with a turbulence model by taking advantage of traditional, robust CFD algorithms with good convergence characteristics. The capturing of time-accurate characteristics of the unsteady flow field and the the nondispersive and nondissipative characteristics of the acoustic field, is conducted by using CAA methodology for the perturbations about the mean flow. In order to reduce the computational time, the calculations are performed in parallel, using a domain decompostion strategy. This attempt at understanding and overcoming some obstacles that arise in direct simulation of CAA, opens new prospects for predicting the acoustics of aircraft engine liners.
Health effects in the upper extremeties of persons operating low-vibration power tools
Authors: Brammer Anthony J. , Sutinen P. , Koskimies K. , Pyykkö I. , Starck J.
Published: July 2002

A group of manual workers (N=18) who operate low-vibration power tools (|ahw|max<2 m s−2) has been examined for objective evidence of work-related changes in hand and arm function. The subjects were drawn from and selected to be representative of a cohort of chain saw operators (N=124) whose health has been followed prospectively, 30% of whom reported experiencing numbness in the upper extremities. A method for detecting a statistically sufficient change in tactile acuity from measurements of mechanoreceptor-specific vibrotactile perception thresholds conducted over a 5-yr interval has been developed, together with any shift in acuity from the value occurring in healthy persons. A progressive deterioration in acuity was found in 12/36 hands, which is predicted to result in abnormal acuity in 39% of the group after a further 5 yr of work. The subjects predicted to be most severely affected currently exhibit reduced hand grip, and reduced hand and arm strength.
Hot topics in acoustical oceanography
Authors: Buckingham Michael J.
Published: July 2002

Acoustical oceanography involves the use of inverse acoustic techniques to investigate physical and biological phenomena in the sea. Processes at the sea surface, including bubble formation from wave breaking, precipitation rates, and gas transfer across the air–sea interface, are all being interrogated using active and passive acoustic techniques. Novel methods for monitoring fish stocks, based on the acoustic properties of the swim bladder, are also receiving attention. The acoustic calls of marine mammals are being investigated as natural sound sources to characterize the ocean environment. New geo-acoustic models to marine sediments have been developed and incorporated into ambient noise inversion techniques for determining seabed properties. Time-reversal experiments have been conducted over ranges of several kilometers, successfully stabilizing acoustic arrivals and allowing fluctuations in the ocean to be characterized. Brief accounts of these topics will be presented.
Similarity scaling for consonants and consonant clusters in initial position
Authors: Newman Rochelle S. , Sawusch James R. , Luce Paul A.
Published: July 2002

Knowing the perceived similarity between different consonants and consonant clusters in different syllable positions is important for models of word recognition that involve activation of neighborhoods of similar-sounding words. Similarity data may also help in understanding whether clusters are single entities, or are decompositional. Furthermore, the extent to which similarity is dependent on the particular talker is relevant for issues of talker normalization. In this study, participants rated the similarity of pairs of consonant–vowel and consonant cluster–vowel syllables in two different voices (one male, one female) over the course of five sessions. The similarity spaces will be discussed in relation to the issues described above. In general, there was no evidence for the decompositionality of consonant clusters. There was a high correlation (r=0.81) in the similarity spaces between the two voices. However, the results from a subset of the items presented in a third voice showed much lower correlations than did the results from the original two voices. This highlights the need to control factors such as the corpus of items, voices, and context when examining similarity scaling data. [Work supported by NIDCD Grant Nos. R01 DC00219 and R01 DC0265801-A1 to SUNY at Buffalo.]
Individual differences of transient evoked otoacoustic emissions: Effects of gender and ear canal volume
Authors: Romano Lisa Jayne , Jupiter Tina
Published: July 2002

Transient evoked otoacoustic emissions (TEOAE) are an objective means for measuring cochlear hearing loss in newborn infants. TEOAEs are low-intensity sounds produced by the normal cochlea that are elicited by acoustic stimuli and then recorded in the outer ear canal. Protocols are being developed for clinical use, and pass/fail criteria are usually based on the size of the emission. The common practice is to wait until an emission of 6 dB is achieved before recording a positive result. Within subject, stimulus-related characteristics may influence the results. Quantifying the sources of variability can effect the analysis of the results. This study will investigate the effects of gender and ear canal volume on TEOAE size. Five male and five female young adult volunteers will serve as subjects. None of the volunteers will have a history of otologic disease or use of medication. All subjects will have normal hearing and normal middle ear function. Pure-tone audiometry and single frequency immittance testing (226 Hz probe tone) will be made. TEOAE will be measured using ILO88 hardware controlled by an IBM PC.
Crack detection in simple and complex beamlike structures
Authors: Arzoumanian Sevag H. , Swanson David C.
Published: July 2002

An approximate technique, inspired by Skudrzyk’s mean value theory, for determining the severity of single cracks in uniform beams having arbitrary intermediate and boundary conditions is presented. It is based on a weighted sum over eigenfrequency shifts of higher-order modes—modes 2 and higher—and does not require knowledge of the details of the structure. Starting from an analysis of a uniform beam with a midspan crack, a closed form expression, valid for all ranges of crack compliance, for the eigenfrequency shifts of higher-order modes is obtained. This result is used to derive an expression, consisting of a weighted sum of eigenfrequency shifts over a fixed frequency band, that is independent of structural details that are further than half a wavelength away from crack. This sum is valid for arbitrarily located cracks on uniform beams and, if evaluated over an appropriate band, is shown to be independent of boundary conditions and beam length. Finally, Skudrzyk’s mean value theory is invoked to extend this approach to truly complex beam assemblies. Analytical predictions agree well with computational results. [Work supported by ONR.]
Nonanalytic nonlinear oscillations: Christiaan Huygens, quadratic Schrödinger equations, and solitary waves
Authors: Denardo Bruce
Published: July 2002

An example of an oscillatory system with a time-reversible nonanalytic nonlinearity is shown to be a pendulum with a flexible cord sandwiched between two identical circular disks, in contrast to the analytic case of a pendulum interrupted by a single circular disk. The amplitude-dependent frequencies of both cases are perturbatively calculated, and are compared to numerical simulations. The nonanalyticity causes the unusual effect of the frequency to vary linearly with amplitude for small amplitudes, which has also been observed in compressional standing waves in sandstone. The general condition for a nonanalytic nonlinearity to yield this behavior is presented. The amplitude-dependent frequency for the double-interrupted pendulum allows an explanation for Huygens’ observation that circular interrupters were as effective as cycloidal interrupters in achieving isochronous motion. A lattice of linearly coupled double-interrupted pendulums is described near the lower and upper cutoff modes by quadratic nonlinear Schrödinger (NLS) equations, in contrast to cubic NLS equations which arise for analytic pendulum lattices as well as typical acoustic and surface wave guides. Solitary breather and kink solutions to the quadratic NLS equations are presented, and the quadratic NLS breather is predicted to occur in a bar of sandstone. [Work supported by ONR.]
Tower bell music through the centuries
Authors: Halsted Margo
Published: July 2002

From a single bell thousands of years ago to a modern carillon of up to seven octaves, bell sounds and bell music have fascinated, informed, regulated, and entertained the people within their sphere. The talk will concentrate on the Western traditions of marking the hours, signaling, banishing evil spirits, enriching market place activity, and filling the air with the distinctive and sometimes complicated sounds of a carillon concert. Slides and recordings will illustrate the instruments and the music.
Horizontal coherence in shallow water
Authors: Rozenfeld Ilya , Cable Peter , Carey William , Siegmann William L.
Published: July 2002

For applications such as beamforming and matched field processing, the spatial behavior of the shallow water acoustic field is relevant. Oceanic and geoacoustic variabilities introduce random fluctuations into the field, which can be characterized by the spatial coherence. The spatial coherence of the acoustic field can be described by its correlation function. In this presentation results from an investigation of the sensitivity of the horizontal correlation function to variations in parameters of shallow water propagation will be discussed. In order to demonstrate key sensitivities, stratified environmental models with one or more sediment layers will be used. Variabilities are assumed to arise from small random fluctuations within the layers and at the layer interfaces. Formulas based on a modal perturbation approach are used. The dependence of the correlation function on such parameters as range and frequency is of particular interest, and in addition effects of mode coupling are estimated. Numerical simulations illustrating the results will be presented. [Work supported by NSF.]
Ultrasound-mediated transdermal delivery of tagging compounds into migratory fish
Authors: Clark Joseph A. , Young Jane A. , Bart Amrit N. , Zohar Yonathan
Published: July 2002

There is a need for noninvasive, low-cost, efficient methods of tagging large numbers of aquatic animals. For example, improved tagging methods are needed to follow the migratory patterns of some endangered salmonoid species. This talk reports on an investigation of the feasibility of using cavitation levels of ultrasound to mediate the delivery of tagging compounds into fish. Two tagging compounds are investigated: calcein (Fluorexon) and oxytetracycline-hydrochloride (Terramycin). Both of these compounds are presently used as tagging agents. However, injection methods of delivery are not efficient for cases where large numbers of wild fish are involved, and if they are placed directly into the aquatic environment of fish the compounds diffuse too slowly through the skin to adequately tag the fish before creating other health problems for them. A system for generating controlled doses of cavitation level ultrasound to schools of fish will be described and measurements of the enhancement in delivery of the tagging compounds to the fish will be reported.
Perception of English /n l/ with amplified consonants or transitions by native speakers of Chinese
Authors: Schmidt Anna Marie , Kaminski Amy C.
Published: July 2002

Previous work has shown that speakers of some southern Chinese dialects have difficulty perceptually differentiating English /n l/. In this study, an attempt was made to increase the perceptual salience of some possible acoustic cues. Seven native Chinese speakers labeled the first consonant of three combined sets of ten English /n l/ minimal pairs produced by a male and a female native English speaker. One set consisted of unaltered words from the earlier study. The consonant portion of the second set had been normalized for peak amplitude. The peak amplitude of the consonant was then equal to the peak amplitude of the vowel. In the third set, a portion of the CV transition had been normalized. Native English speakers labeled the words with high accuracy. Results and implications will be discussed.
An acoustic and perceptual study of Swiss German stops
Authors: Ham William H.
Published: July 2002

Oral stops in Swiss German show a three-way contrast, traditionally characterized as lenis /b, d, g/, fortis /p, t, k/ and long fortis /p:, t:, k:/. Fortis occur after long vowels, long fortis after short vowels, and lenis after both. Spectrographic analysis was performed on all stops in medial and final position for three Bernese speakers. Absence of voicing and lack of significant differences in voice onset times were noted, suggesting closure duration alone accounts for the three-way contrast: lenis are on average 57% shorter than fortis, and fortis 70% shorter than long fortis. Using the minimal set [ra:de] (‘spin’), [ra:te] (‘guess’) and [rat:e] (‘rat’), the salience of preceding vowel length relative to closure duration was examined in two perceptual experiments: The lenis stop was lengthened in 20-ms increments to long fortis length, and the long fortis stop was shortened to lenis length. The lengthened continuum shows a clear shift from lenis to fortis percept, but no shift to fortis long. The shortened continuum shows chance performance. Robust crossover effects in the lengthened continuum suggest vowel and consonant length are relevant to stop identification, while the shortened continuum suggests vowel length is primary.
Binaural enhancement of simultaneous vowels
Authors: Paschall D. Dwayne
Published: July 2002

Previous investigations have shown that for monaural presentations, identification accuracy of simultaneous vowels improves when a precursor with the same F0 and spectrum envelope is present which draws attention to a particular voice. In normal listening situations, however, one likely makes use of both ears rather than one ear only. The present investigation examined the ability of a dichotic precursor to enhance simultaneous vowel sounds presented to the left ear. A precursor was presented to the listeners whose intensity level in the left ear was the same as that used in previous investigations. However, the intensity of the precursor in the right ear was varied to produce different perceptual locations of the precursor: left ear only, 45° left of midline, midline, 45° right of midline, and right ear only. Thus the same monaural stimulus that has been shown to produce enhancement in previous investigations was present in each precursor location. However, the perceptual location of the precursor was different in every condition. Results from this investigation suggest that the perceived location of the precursor can have a significant effect on whether the precursor does or does not produce enhancement. If the perceived location of the precursor occurs in a different place from the simultaneous vowel stimulus, the precursor is not effective in enhancing the identification performance of the added vowel.
Ship-radiated noise-field characterization
Authors: Wales Stephen C.
Published: July 2002

Sonobuoy measurements of merchant ships were processed for mean levels and fluctuation dynamics of the broadband and line components from a large database of ships. Direct path results are reported. The mean levels are compared with various ship source level models. The levels are shown to agree with Ross-type models with some minor differences noted. The importance of source characterization, particularily source depth, in interpreting these results is emphasized. Fluctuations of the broadband component are shown to vary by as much as 6 dB with periods of 10–20 s for a limited number of ships. The results are shown to be consistent with the hypothesis that they are due to ship motion in the water. Examples are provided of ship line temporal variation in frequency and amplitude. Preliminary work on categorizing the data according to the spectra characteristics and time behavior is discussed.
Biomimetic sonar differentiates coin head from tail
Authors: Kuc Roman B.
Published: July 2002

An active sonar using Polaroid electrostatic transducers positioned at the end of a robot arm can recognize an object from its echoes. The sonar adaptively changes its location and configuration in response to the echoes. The sonar mimics biological echo-location systems, such as those employed by bats and dolphins, in that there is a center transmitter flanked by two adjustable receivers, the sonar has rotational and translational mobility, and the echo processing contains elements that have been observed in the mammalian auditory system. The sonar translates in a horizontal plane and rotates in pitch and yaw to position an object at a standard location within the beam patterns. The transmitter points at the object to maximize the incident acoustic intensity and the receivers rotate to maximize the echo amplitude and bandwidth and to minimize the echo-producing region. This procedure results in a unique echo vector associated with each object at a given object pose. Recognition is accomplished by extracting 32 values from the binaural echo patterns and searching a database that is constructed during a learning phase. The system can differentiate reliably the head and tail sides of a coin. [Work supported by NSF Grant IRI–9504079.]
Coarticulation of disyllables by deaf and hearing speakers
Authors: Okalidou Areti , Harris Katherine S.
Published: July 2002

The coarticulatory patterns of three deaf and three hearing adult speakers were assessed as a function of segment type and phonetic context, by means of acoustic analysis of the F2. The F2 differences between /■♯CVC/ disyllables minimally contrasting in vocalic ([i], [u], [a]) and in constant ([b], [d]) context, respectively, were examined at five measurement locations, namely, at ■ onset, ■ midpoint, ■ offset, and transition onset and vowel midpoint of the stressed vowel. Intervocalic coarticulation was greater for either deaf or hearing speakers, depending on the phonetic composition of disyllables (bVb or dVd). Moreover, the deaf speakers showed less marked consonant influences on the ■ and stressed vowel portions of disyllables compared to the hearing controls. The above findings partly dispute the conclusions drawn from previous studies. Furthermore, they suggest that the speech of deaf speakers is guided by patterns of articulatory organization similar in certain respects to those of young children learning to speak.
Improving the process of automatically extracting diphones with context-dependent boundaries for synthesized speech
Authors: Yarrington Debra M. , Hoskins Steven R. , Bunnell H. Timothy
Published: July 2002

A method has been developed for automatically extracting diphone speech segments with context-dependent boundaries. When compared with speech synthesized from manually extracted diphone speech segments, it was found that speech synthesized from the automatically extracted segments was, overall, slightly less intelligible but slightly more natural sounding [Yarrington et al., ‘‘Robust automatic extraction of diphones with variable boundaries,’’ in EUROSPEECH ’95, 4th European Conference on Speech Communication and Technology, Vol. 3, pp. 1845–1848, Madrid, Spain (1995)]. The lower intelligibility appeared to be due to a small number of very poor diphone segments. While it is feasible to correct this problem by manually replacing misleading diphones, several changes have been made to the extraction procedure to eliminate or at least reduce the frequency of occurrence of incorrect diphones. In particular, a different spectral measure is being used for estimates of spectral similarity, and F0 plus a spectral robustness measure have been added as features which are used in selecting diphones for extraction. Perceptual data comparing words generated from a diphone inventory constructed using the new algorithm with words generated from the original manually constructed inventory will be presented. [Work supported by NIDRR Grant No. H133E30010, the Nemours Research Programs, and the Microsoft Corporation.]
Modeling nonlinear pulses in sediments with attenuation and dispersion
Authors: Kulkarni Rahul S. , Siegmann William L. , Collins Michael D. , McDonald B. Edward
Published: July 2002

A hybrid treatment for wide-angle paraxial propagation that includes effects of both sediment dispersion and weak nonlinearity has been developed. A Fourier transform approach is used to combine effects of refraction, diffraction, and sediment dispersion in the frequency domain, and nonlinear effects in the time domain. A nonlinear wide-angle time-domain equation developed recently is first split into linear and nonlinear component equations. The linear equation is decomposed into its discrete frequency-domain counterparts. Sediment attenuation and dispersion are incorporated using a complex wave number along with a frequency-dependent formula for phase velocity to satisfy causality. The numerical implementation consists of first decomposing a broadband source into its frequency components and propagating them over a range step using a wide-angle PE. Fourier synthesis is used to reconstruct the signal, which is then corrected to account for nonlinear effects in the time domain. Numerical examples illustrating the effects of dispersion and nonlinearity on shallow-water wide-angle propagation will be presented and compared with available results. [Work supported by ONR.]
Far-field acoustic holography onto cylindrical surfaces using pressure measured on semicircles
Authors: Norris Andrew N.
Published: July 2002

A simple formula was recently proposed by Williams [J. Acoust. Soc. Am. 99, 2022–2032 (1996)] for imaging pressure and velocity on a vibrating circular cylindrical shell using the far-field pressure measured along a meridional semicircle. The method is examined and some new results are obtained. The procedure is generalized to handle cylindrical surfaces of noncircular but convex cross section. It is demonstrated that Williams’ formula predicts a supersonic surface intensity which gives the same meridional energy flux as the exact radiated far-field pressure. A modification of Williams’ formula is suggested which uses pressure data from several neighboring semicircles, although complete spherical coverage is not required. The modified imaging formula is based upon the first two terms in an asymptotic expansion in the dimensionless wave number. The leading-order term yields the original formula, and the second term results in a boundary layer type of correction in the circumferential direction. Numerical examples are presented which compare the exact supersonic acoustic intensity on a cylinder with that from the original and the modified formula. These indicate that the circumferential on-surface resolution is significantly enhanced by combining data from neighboring semicircles, even when the total far-field spherical coverage is small.
Scattering of elastic waves from thin shapes in three dimensions using the composite boundary integral equation formulation
Authors: Liu Yijun , Rizzo Frank J.
Published: July 2002

In this paper, the composite boundary integral equation (BIE) formulation is applied to scattering of elastic waves from thin shapes with small but finite thickness (open cracks or thin voids, thin inclusions, thin-layer interfaces, etc.), which are modeled with two surfaces. This composite BIE formulation, which is an extension of the Burton and Miller’s formulation for acoustic waves, uses a linear combination of the conventional BIE and the hypersingular BIE. For thin shapes, the conventional BIE, as well as the hypersingular BIE, will degenerate (or nearly degenerate) if they are applied individually on the two surfaces. The composite BIE formulation, however, will not degenerate for such problems, as demonstrated in this paper. Nearly singular and hypersingular integrals, which arise in problems involving thin shapes modeled with two surfaces, are transformed into sums of weakly singular integrals and nonsingular line integrals. Thus, no finer mesh is needed to compute these nearly singular integrals. Numerical examples of elastic waves scattered from penny-shaped cracks with varying openings are presented to demonstrate the effectiveness of the composite BIE formulation.
Wave propagation in stressed composites
Authors: Degtyar A. D. , Huang W. , Rokhlin S. I.
Published: July 2002

The performance of high-temperature composites can be significantly affected by the presence of residual stresses. These stresses arise due to the mismatch of thermal expansion coefficients between matrix and fibers during cooling from fabrication temperature to room temperature. This effect is especially pronounced in metal matrix and intermetallic composites. It can lead to plastic deformation, matrix cracking and fiber/matrix interface debonding. Elastic wave propagation in homogeneously stressed media has been frequently addressed in the literature. However, the effect of nonhomogeneous stress distribution has not been investigated. This is especially important since the average residual stresses are zero in equilibrium and thus their distribution is inherently nonhomogeneous. In this paper, the feasibility of using ultrasonic techniques for residual stress assessment in composites is addressed. A theoretical method is presented for determining the velocities of ultrasonic waves propagating through a composite material with a nonhomogeneous distribution of residual stresses. It is based on the generalized self-consistent multiple scattering model. Calculated results for longitudinal and shear ultrasonic wave velocities propagating perpendicular to the fiber direction in SCS-6/Ti composite with and without residual stresses are presented. They show that velocity changes due to the presence of stresses are on the order of 1%.
Representation of the displacement in terms of scalar functions for use in transversely isotropic materials
Authors: Rahman A. , Ahmad F.
Published: July 2002

Comments are presented on two recent papers [J. Acoust. Soc. Am. 96, 2546 (1994), J. Acoust. Soc. Am. 100, 57 (1996)]. Their results can be obtained with much economy of work by employing an alternative representation for the decomposition of the displacement. This decomposition is useful whenever transversely isotropic materials are being studied.
Measurements and computations of shooting noise. Part 2: Bullet noise
Authors: van den Berg Frank H. A. , Salomons Erik M.
Published: July 2002

Due to the supersonic speed of the bullet, a shock wave is generated (sonic boom). A method has been developed to compute the generation and propagation of bullet noise on the basis of the geometry of the bullet and its speed. This model also holds for bullet paths of finite length with decreasing bullet speed. The accuracy of this model is investigated by comparison with experimental data for propagation of bullet noise of several weapons, over ranges up to 7 km. The caliber of the weapons ranges from 5.56 to 120 mm. The measurements indicate that nonlinear effects are only important for the first few hundred meters from the bullet path. This is explained by a coherence loss, caused by propagation through the atmosphere. When corrected for this loss, the measurements and calculations of bullet noise compare reasonably well. [This work was coordinated and financed by the Dutch Ministry of Defence, Defence Co-ordinator Physical Planning and Environmental Affairs (MODNL-CROMD).]
A self-learning predictive model of articulator movements during speech production
Authors: Blackburn C. Simon , Young Steve
Published: July 2002

A model is presented which predicts the movements of flesh points on the tongue, lips, and jaw during speech production, from time-aligned phonetic strings. Starting from a database of x-ray articulator trajectories, means and variances of articulator positions and curvatures at the midpoints of phonemes are extracted from the data set. During prediction, the amount of articulatory effort required in a particular phonetic context is estimated from the relative local curvature of the articulator trajectory concerned. Correlations between position and curvature are used to directly predict variations from mean articulator positions due to coarticulatory effects. Use of the explicit coarticulation model yields a significant increase in articulatory modeling accuracy with respect to x-ray traces, as compared with the use of mean articulator positions alone.
Rheological Properties of Narrow Distribution Polystyrene Solutions
Authors: Ashare Edward
Published: July 2002

Experimental non-Newtonian viscosity, primary normal stress difference, dynamic viscosity, and dynamic storage modulus data were obtained for 16 viscoelastic fluids. The fluids investigated were solutions of almost monodisperse polystyrene in Aroclor (a mixture of chlorinated diphenyls). Several nonlinear rheological equations of state were fit to the experimental data, and the Bird-Carreau model was found to fit the data within 15% for every solution investigated. Bird-Carreau model parameters were determined by use of a nonlinear least-squares computer analysis, and these parameters were related to polymer molecular weight and concentration. Experimental values of the steady-state compliance were obtained from primary normal stress difference and shear stress data. These values agreed with the Rouse theory prediction.
The Limit of Linear Viscoelastic Response in Polymer Melts as Measured in the Maxwell Orthogonal Rheometer
Authors: Gross Lawrence H. , Maxwell Bryce
Published: July 2002

The Maxwell orthogonal rheometer was used to measure the limit of linear viscoelastic response (LLVER) as a function of frequency for three linear polyethylenes at 170°C, for six atactic polystyrenes at 170°C, and for Phenoxy A at 212°C. For the elastic component of the stress, linear viscoelastic response was found to exist in all cases up to finite strains of approximately 50%. The viscous component of the stress exhibited linear viscoelastic response up to approximately 100% strain and sometimes as high as 120%, the maximum strain tested. Two constitutive equations (Bird and Carreau's theory with Gordon and Schowalter's generalization and Tanner's network rupture theory) are noted for the dependence they predict of the strain LLVER as a function of frequency. Bird's theory, with Gordon and Schowalter's generalization, predicts that the elastic strain limit times the frequency will be a constant as the frequency is varied; Tanner's theory predicts that the elastic strain limit will be a constant with varying frequency. Data are shown to support Tanner's theory. Although the theories predict similar relations for the viscous strain limit, since no viscous limit is found up to 120% strain, this portion of the theories could not be checked. Plots of the reduced in-phase modulus, G′(γ)/GL′, and the reduced in-phase viscosity, η′(γ)/ηL′, versus strain, γ, (GL′ and ηL′ are the modulus and viscosity below the limit) yield very similar curves for all the polymers. This is in agreement with the limited data from MacDonald, Marsh, and Ashare. The reduced in-phase modulus is constant as the strain is increased up to the elastic LLVER. A gradual decrease then occurs for all of the polymers; at 120% strain, the reduced modulus has decreased between 20 and 30%.
Numerical simulation of viscoelastic flow around a cylinder using an integral constitutive equation
Authors: Barakos G. , Mitsoulis E.
Published: July 2002

Numerical simulations have been undertaken for the flow of a 5 wt. % polyisobutylene (PIB) solution in tetradecane (C14) around a cylinder placed between parallel plates. The PIB solution has been the subject of an extensive rheological characterization and the flow geometry corresponds to the one used in a previous study for laser Doppler anemometry and flow-induced birefringence measurements. The constitutive equation used is an integral-type K-BKZ model with a relaxation spectrum, which fits well experimental data for the shear and elongational viscosities and the normal stresses as measured in shear flow. Stable numerical solutions have been obtained and used to compare the K-BKZ model predictions with the experimental data reported recently by Baaijens. The velocity and shear stress values predicted by the simulation are in excellent agreement with the experimental ones. Very good agreement is also obtained for the predictions of the first normal stress difference both before and after the cylinder, in sharp contrast with previous experimental results, which had shown a much slower relaxation of the stresses. The drag force exerted by the fluid on the cylinder has been calculated and reported to be a decreasing function of the Deborah number De.