bluuebunny/crossref_metadata_2025 huggingface dataset:
Vacillating and Mixed Emotions: A Conceptual‐Discursive Perspective on Contemporary Emotion and Cognitive Appraisal Theories Through Examples of Pride
Authors: Sullivan Gavin B. , Strongman Kenneth T.
Published: May 2003

Gavin B. Sullivan and Kenneth T. Strongman, Vacillating and Mixed Emotions: A Conceptual‐Discursive Perspective on Contemporary Emotion and Cognitive Appraisal Theories Through Examples of Pride, pp. 203–226.

Vacillating and mixed emotional experiences are often difficult to explore and understand because they confront the limits of our language's ability to capture private experiences in extreme or abnormal circumstances. In this paper, we build upon remarks by Wittgenstein (1953) to present a conceptual‐discursive perspective based on naturalistic examples of individuals vacillating between pride and other emotions. This perspective is used to show how relevant emotion theories contain conceptual errors of the sort identified by Wittgenstein. The “assembled reminders” of shifts between pride and other emotions are presented in contrast to analyses that focus on people's identification of causes of emotions, an approach which leads to theoretical speculation about underlying appraisal set changes or discussion of the empirical justification of cognitive ontology. We bypass a direct confrontation on these issues by examining how people's talk about the content of vacillating and mixed emotional experiences (i.e., aspect shifts) augments a shared “emotionology” with creative expressions and poetic comparisons. This last point is illustrated by the emotional instability experienced by individuals with Borderline Personality Disorder (BPD). Support for the conceptual‐discursive perspective is provided by the success of a particular therapeutic approach, the Conversational Model, in ameliorating the developmental disruption of BPD by encouraging participation in empathic conversations. We conclude that a conceptual‐discursive perspective undermines the cognitive appraisal “picture” of vacillating emotions and adds to our understanding.
A hybrid algorithm for the two‐dimensional layout problem: the cases of regular and irregular shapes
Authors: Hifi M. , M'Hallah R.
Published: June 2003

The two‐dimensional layout (TDL) optimization problem consists of finding the minimal length layout of a set of both regular and irregular two‐dimensional shapes on a stock sheet of finite width but infinite length. The layout should not contain any overlap. In this paper, we solve the TDL problem by proposing two approximate algorithms. The first one is a new heuristic based on a constructive approach specifically designed for irregular shapes, but that works well with regular ones. The second is a hybrid method in which the constructive approach displays the layouts corresponding to the chromosomes yielded by the genetic algorithm. The resulting algorithm yields satisfactory results in relatively short computational times as shown by the extensive computational testing on problems from the literature.
DEA network computing in multi‐stage parallel processes
Authors: Sueyoshi Toshiyuki , Honma Takashi
Published: June 2003

DEA (Data Envelopment Analysis) is a managerial method that has been widely used for performance analysis in various public and private sectors. To deal with large‐scale DEA problems, this research proposes the architecture of DEA network computing (LAN: Local Area Network) that is designed to coordinate a simultaneous use of multiple personal computers. An important feature of the proposed DEA computer architecture is that it is computationally structured in multi‐stage parallel processes to enhance its algorithmic efficiency. The performance of the proposed network computing approach is tested and examined in a large simulation study.
Constructing nurse schedules at large hospitals
Authors: Dias Tiago M. , Ferber Daniel F. , De Souza Cid C. , Moura Arnaldo V.
Published: June 2003

Several heuristics, based on evolutive algorithms and local search, are used to solve the nurse scheduling problem at a large hospital. Due to several intricate and specific restrictions imposed on the schedules, the problem is a difficult one to solve by hand. Moreover, some of the restrictions have a subjective value attached to them, and this constrains the use of exact methods that search for global optima. In order to facilitate the use of the solver modules by the hospital staff, a user interface was also implemented.
Towards an integrated environmental assessment for wetland and catchment management
Authors: Turner R Kerry , Georgiou Stavros , Brouwer Roy , Bateman Ian J , Langford I J
Published: June 2003

This paper develops a decision support system for evaluation of wetland ecosystem management strategy and examines its, so far partial, application in a case study of an important complex coastal wetland known as the Norfolk and Suffolk Broads, in the east of England, UK. Most managed ecosystems are complex and often poorly understood hierarchically organized systems. Capturing the range of relevant impacts on natural and human systems under different management options will be a formidable challenge. Biodiversity has a hierarchical structure which ranges from the ecosystem and landscape level, through the community level and down to the population and genetic level. There is a need to develop methodologies for the practicable detection of ecosystem change, as well as the evaluation of different ecological functions. What is also required is a set of indicators (environmental, social and economic) which facilitate the detection of change in ecosystems suffering stress and shock and highlight possible drivers of the change process. A hierarchical classification of ecological indicators of sustainability would need to take into account existing interactions between different organization levels, from species to ecosystems. Effects of environmental stress are expressed in different ways at different levels of biological organization and effects at one level can be expected to impact other levels, often in unpredictable ways. The management strategy, evaluation methodologies and indicators adopted should also assess on sustainability grounds whether any given management option is supporting, or reducing, the diversity of functions which are providing stakeholders with the welfare benefits they require.
Merged remotely sensed data for geomorphological investigations in deserts: examples from central Saudi Arabia
Authors: Al‐juaidi Farhan , Millington Andrew C , Mclaren Sue J
Published: June 2003

Image merging has gained acceptance in geological remote sensing, however it has rarely been applied in geomorphology. We report on the usefulness of principal components substitution (PCS) to merge IRS panchromatic data with multispectral Thematic Mapper (TM) imagery, to map commonly encountered desert geomorphological features, and in relative age dating of alluvial surfaces. The merged data were applied to the identification and mapping of geomorphological features along two geolo‐gically different mountain fronts in central Saudi Arabia. Two types of geomorphological maps have been created. A morphogenetic map that distinguishes between aeolian landforms, fluvial landforms, desert pavements, and gypsum crusts. Second, a morphochronological map, which shows the relative age of four geomorphic surfaces developed on an alluvial fan. The construction of the two maps is supported by field observations and laboratory measurements. Using the optimum index factor (OIF), a TM band 1, 5 and 7 image (of 20 merged composites) was found to be the optimum colour composite image for the geomorphological features in this arid environment. We discuss our findings in the context of the spatial and spectral properties required for applied geomorphological remote sensing.
Monitoring hydrological controls on dust emissions: preliminary observations from Etosha Pan, Namibia
Authors: Bryant Robert G
Published: June 2003

Atmospheric dust loadings have a significant influence on global climate by affecting air temperatures through the absorption and scattering of solar radiation. Many dryland basins are significant sources of aeolian dust, but our knowledge of how dust emissions from these systems are affected by ephemeral wetting events is either limited or poor. This research uses synergistic data sets (Total Ozone Mapping Spectrometer (TOMS) and Advanced Very High Resolution Radiometer (AVHRR)) in order to identify possible hydrological controls on aeolian dust emissions from the Etosha Basin, Namibia. Data suggest that individual inundation events (detected by AVHRR) within this basin have a marked effect on immediate and subsequent dust emissions (detected by TOMS). This study also outlines the contribution of dust emissions from both the pan surface and from the ephemeral oshanas region to the north of the Etosha Basin to the persistent dust plume, and highlights the complexity of the interactions between hydrology, land use and dust emissions within ephemeral basins.
War with Iraq: A Cost–Benefit Analysis
Authors: Cordesman Anthony H. , Wilson Joseph C. , Takeyh Ray , Kemp Geoffrey
Published: May 2003

The following is an edited transcript of the thirtieth in a series of Capitol Hill conferences convened by the Middle East Policy Council. The meeting was held on October 9, 2002, in the Dirksen Senate Office Building with Chas. W. Freeman, Jr., moderating.
Influence of viscosity on the diffraction of sound by a circular aperture in a plane screen
Authors: Davis Anthony M. J. , Nagem Raymond J.
Published: May 2003

The linearized equations of viscous fluid flow are used to analyze the diffraction of a time-harmonic acoustic plane wave by a circular aperture in a rigid plane screen. Arbitrary aperture size and arbitrary angle of incidence are considered. Sets of dual integral equations are derived for the diffracted velocity and pressure fields, and are solved by analytic reduction to sets of linear algebraic equations. In the case of normal incidence, numerical results are presented for the fluid velocity in the aperture and the power absorption due to viscous dissipation. The theoretical results for power absorption are compared to previously obtained results from high amplitude acoustic experiments in air. The conditions under which the dissipation predicted by linear theory becomes significant are quantified in terms of the fluid viscosity and sound speed, the acoustic frequency, and the aperture radius.
Nonlinear coupling of surface and quasitransverse bulk modes in cubic crystals
Authors: Kumon R. E. , Hamilton M. F.
Published: May 2003

In crystals the speed of the surface acoustic wave mode may approach that of the lowest-speed quasitransverse bulk mode in some directions of propagation. Under these circumstances, it is possible for energy to be transferred from the surface mode to the bulk mode by nonlinear coupling. In the present paper we investigate the possibilities for mode coupling in the (001), (110), and (111) planes of cubic crystals. A condition is given for determining the range of propagation directions with significant coupling, and numerical results are provided for eight different crystals with a range of anisotropy ratios. It is shown that even for significant excitation amplitudes the coupling is negligible for most propagation directions in the aforementioned surface cuts.
Amplitude and phase of distortion product otoacoustic emissions in the guinea pig in an (f1,f2) area study
Authors: Schneider Sandra , Prijs Vera F. , Schoonhoven Ruurd
Published: May 2003

Lower sideband distortion product otoacoustic emissions (DPOAEs), measured in the ear canal upon stimulation with two continuous pure tones, are the result of interfering contributions from two different mechanisms, the nonlinear distortion component and the linear reflection component. The two contributors have been shown to have a different amplitude and, in particular, a different phase behavior as a function of the stimulus frequencies. The dominance of either component was investigated in an extensive (f1,f2) area study of DPOAE amplitude and phase in the guinea pig, which allows for both qualitative and quantitative analysis of isophase contours. Making a minimum of additional assumptions, simple relations between the direction of constant phase in the (f1,f2) plane and the group delays in f1-sweep, f2-sweep, and fixed f2/f1 paradigms can be derived, both for distortion (wave-fixed) and reflection (place-fixed) components. The experimental data indicate the presence of both components in the lower sideband DPOAEs, with the reflection component as the dominant contributor for low f2/f1 ratios and the distortion component for intermediate ratios. At high ratios the behavior cannot be explained by dominance of either component.
The measurement of A0 and S0 Lamb wave attenuation to determine the normal and shear stiffnesses of a compressively loaded interface
Authors: Drinkwater Bruce W. , Castaings Michel , Hosten Bernard
Published: May 2003

Guided waves in an elastic plate surrounded by air propagate with very low attenuation. This paper describes the effect on this propagation of compressively loading an elastomer with high internal damping against one surface of the elastic plate. The propagation of both A0 and S0 Lamb modes is considered. The principal effect is shown to be increased attenuation of the guided waves. This attenuation is caused by leakage of energy from the plate into the elastomer, where it is dissipated due to high viscoelastic damping. It is shown that the increase in attenuation is strongly dependent on the compressive load applied across the solid–solid interface. This interface is represented as a spring layer in a continuum model of the system. Both normal and shear stiffnesses of the interface are quantified from the attenuation of A0 and S0 Lamb waves measured at each step of the compressive loading. The normal stiffness is also measured independently by normal incidence, bulk longitudinal wave ultrasound. The resulting predictions of wave propagation behavior, such as attenuation, obtained by the model are in excellent agreement with those measured experimentally.
Precise measurements of bulk-wave ultrasonic velocity dispersion and attenuation in solid materials in the VHF range
Authors: Kushibiki Jun-ichi , Okabe Ryoichi , Arakawa Mototaka
Published: May 2003

A general method was established for precisely measuring velocity dispersion and attenuation in solid specimens with acoustic losses in the very high frequency (VHF) range, using the complex-mode measurement method and the diffraction correction method. Experimental procedures were presented for implementing such a method and demonstrated this measurement method in the frequency range of 50–230 MHz, using borosilicate glass (C-7740) as a dispersive specimen and synthetic silica glass (C-7980) as a nondispersive standard specimen. C-7980 exhibited no velocity dispersion; velocity was constant at 5929.14±0.03 m/s. C-7740 exhibited velocity dispersion, from 5542.27 m/s at 50 MHz to 5544.47 m/s at 230 MHz with an increase of about 2 m/s in the measured frequency range. When frequency dependence of attenuation was expressed as α=α0fβ, the results were as follows: α0=1.07×10−16 s2/m and β=2 for C-7980 and α0=5.16×10−9 s1.25/m and β=1.25 for C-7740.
On low frequency sound transmission loss of double sidebranches: A comparison between theory and experiment
Authors: Tang S. K. , Li F. Y. C.
Published: May 2003

The sound power transmission losses of various sidebranches installed along a rectangular duct below the first cut-off frequency of the duct are studied experimentally. Special efforts are made to examine how accurately the plane-wave theory predicts the sound-power transmission loss. Four types of sidebranch impedance are established and their effects to the sound power transmission loss discussed. It is found that under the nonresonant conditions the plane-wave theory can give reasonable prediction when the branch separation is large or the original sound transmission loss of the corresponding single side-branch is weak. The theory always overestimates the sound transmission loss at resonant conditions but gives underestimation if the transmission loss is due to the noise breakout in the sidebranches, especially for short branch separation.
Prediction and measurement of nonpropagating Lamb modes at the free end of a plate when the fundamental antisymmetric mode A0 is incident
Authors: Diligent O. , Lowe M. J. S. , Le Clézio E. , Castaings M. , Hosten B.
Published: May 2003

Reflection of Lamb waves when the fundamental mode A0 is incident at the free end of a plate is studied, in order to identify the extent to which the generation of nonpropagating modes influences the field local to the end of the plate. Semi-analytical predictions, finite element simulations, and experimental measurements are presented for frequencies below the A2 cutoff. First it is shown, for frequencies below the A1 cutoff, that reflection of the A0 mode is accompanied by a delay in phase, and that there is significant additional motion due to nonpropagating modes within about five plate thicknesses of the end. The extend of this additional motion in the vicinity of the end of the plate is demonstrated by subtracting the contribution of the propagating modes from the displacement field. The wave field at frequencies above the A1 cutoff is more complex because the A1 as well as the A0 propagating modes are present at the end of the plate. Nevertheless, it has still been possible, using semi-analytical predictions and finite element simulations, to demonstrate the additional motion due to the nonpropagating modes.
Functional differences between vowel onsets and offsets in temporal perception of speech: Local-change detection and speaking-rate discrimination
Authors: Kato Hiroaki , Tsuzaki Minoru , Sagisaka Yoshinori
Published: May 2003

To provide a perceptual framework for the objective evaluation of durational rules in speech synthesis, two experiments were conducted to investigate the differences between vowel (V) onsets and V-offsets in their functions of marking the perceived temporal structure of speech. The first experiment measured the detectability of temporal modifications given in four-mora (CVCVCVCV) Japanese words. In the V-onset condition, the inter-onset intervals of vowels were uniformly changed (either expanded or reduced) while their inter-offset intervals were preserved. In the V-offset condition, this was reversed. These manipulations did not change the duration of the entire word. Each of the modified words was paired with its unmodified counterpart, and the pair was given to listeners, who were asked to rate the difference between the paired words. The results show that there were no significant differences in the listeners’ abilities to detect the temporal modification between the V-onset and V-offset conditions. In the second experiment, the listeners were asked to estimate the differences they perceived in speaking rates for the same stimulus set as that of the first experiment. Interestingly, the results show a clear difference in the listeners’ performance between the V-onset and V-offset conditions. Specifically, changing the V-onset intervals changed the perceived speaking rates, which showed a linear relation (r=−0.9) despite the fact that the duration of the entire word remained unchanged. In contrast, modifying the V-offset intervals produced no clear relation with the perceived speaking rates. The second experiment also showed that the listeners performed well in speaking rate discrimination (3.5%–5% in the change ratio). These results are discussed in relation to the differences in the listeners’ temporal processing range (local or global) between the two experiments.
Measurement and prediction of ultralow frequency ocean ambient noise off the eastern U.S. coast
Authors: Wilson D. Keith , Frisk George V. , Lindstrom Timothy E. , Sellers Cynthia J.
Published: May 2003

Ultralow frequency (0.02–2 Hz) acoustic ambient noise was monitored from January to April 1991 at six ocean bottom stations off the eastern U.S. coast. The depths of the stations ranged from about 100 m to 2500 m. The measured spectra are in good agreement with predictions made using Cato’s theory [J. Acoust. Soc. Am. 89, 1076–1095 (1991)] for noise generation by surface-wave orbital motion after extending the calculations to incorporate horizontally stratified environments. Contributions from both the linear, single-frequency (virtual monopole) and the nonlinear, double-frequency (dipole) mechanisms are clearly recognizable in the data. The predictions make use of directional wave data obtained from surface buoys deployed during the SWADE experiment and an ocean bottom model derived from compressional wave speed data measured during the EDGE deep seismic reflection survey. The results demonstrate conclusively that nonlinear surface-wave interactions are the dominant mechanism for generating deep-ocean ULF noise in the band 0.2–0.7 Hz.
Acoustic correlates of caller identity and affect intensity in the vowel-like grunt vocalizations of baboons
Authors: Rendall Drew
Published: May 2003

Comparative, production-based research on animal vocalizations can allow assessments of continuity in vocal communication processes across species, including humans, and may aid in the development of general frameworks relating specific constitutional attributes of callers to acoustic-structural details of their vocal output. Analyses were undertaken on vowel-like baboon grunts to examine variation attributable to caller identity and the intensity of the affective state underlying call production. Six hundred six grunts from eight adult females were analyzed. Grunts derived from 128 bouts of calling in two behavioral contexts: concerted group movements and social interactions involving mothers and their young infants. Each context was subdivided into a high- and low-arousal condition. Thirteen acoustic features variously predicted to reflect variation in either caller identity or arousal intensity were measured for each grunt bout, including tempo-, source- and filter-related features. Grunt bouts were highly individually distinctive, differing in a variety of acoustic dimensions but with some indication that filter-related features contributed disproportionately to individual distinctiveness. In contrast, variation according to arousal condition was associated primarily with tempo- and source-related features, many matching those identified as vehicles of affect expression in other nonhuman primate species and in human speech and other nonverbal vocal signals.
Patterns in the vocalizations of male harbor seals
Authors: Van Parijs Sofie M. , Corkeron Peter J. , Harvey James , Hayes Sean A. , Mellinger David K. , Rouget Philippe A. , Thompson Paul M. , Wahlberg Magnus , Kovacs Kit M.
Published: May 2003

Comparative analyses of the roar vocalization of male harbor seals from ten sites throughout their distribution showed that vocal variation occurs at the oceanic, regional, population, and subpopulation level. Genetic barriers based on the physical distance between harbor seal populations present a likely explanation for some of the observed vocal variation. However, site-specific vocal variations were present between genetically mixed subpopulations in California. A tree-based classification analysis grouped Scottish populations together with eastern Pacific sites, rather than amongst Atlantic sites as would be expected if variation was based purely on genetics. Lastly, within the classification tree no individual vocal parameter was consistently responsible for consecutive splits between geographic sites. Combined, these factors suggest that site-specific variation influences the development of vocal structure in harbor seals and these factors may provide evidence for the occurrence of vocal dialects.
Statistics of ultrasonic scatterer size estimation with a reference phantom
Authors: Gerig Anthony , Zagzebski James , Varghese Tomy
Published: May 2003

A theoretical expression for the variance of scatterer size estimates is derived for a modified least squares size estimator used in conjunction with a reference phantom method for backscatter coefficient measurement. A Gaussian spatial autocorrelation function is assumed. Simulations and phantom experiments were performed to verify the results for backscatter and size variances. The dependence of size estimate errors upon free experimental parameters is explored. Implications of the findings for the optimization of scatterer size estimation are discussed. The utility of scatterer size parametric imaging is examined through the signal to noise ratio comparison with standard ultrasonic B-mode imaging.
A nonlinear filter-bank model of the guinea-pig cochlear nerve: Rate responses
Authors: Sumner Christian J. , O’Mard Lowel P. , Lopez-Poveda Enrique A. , Meddis Ray
Published: May 2003

The aim of this study is to produce a functional model of the auditory nerve (AN) response of the guinea-pig that reproduces a wide range of important responses to auditory stimulation. The model is intended for use as an input to larger scale models of auditory processing in the brain-stem. A dual-resonance nonlinear filter architecture is used to reproduce the mechanical tuning of the cochlea. Transduction to the activity on the AN is accomplished with a recently proposed model of the inner-hair-cell. Together, these models have been shown to be able to reproduce the response of high-, medium-, and low-spontaneous rate fibers from the guinea-pig AN at high best frequencies (BFs). In this study we generate parameters that allow us to fit the AN model to data from a wide range of BFs. By varying the characteristics of the mechanical filtering as a function of the BF it was possible to reproduce the BF dependence of frequency-threshold tuning curves, AN rate-intensity functions at and away from BF, compression of the basilar membrane at BF as inferred from AN responses, and AN iso-intensity functions. The model is a convenient computational tool for the simulation of the range of nonlinear tuning and rate-responses found across the length of the guinea-pig cochlear nerve.
Shape identification of underwater objects using backscattered frequency signals
Authors: Liu G. R. , Li Wei , Zhang X. M. , Varadan V. K.
Published: May 2003

The inverse problems in the area of the acoustic scattering often concern the determination of the size, shape, and orientation of an object using the scattered field data. This paper presents a method to retrieve the shape information of an underwater object using illuminated lengths, which can be obtained from the ramp response signatures of the object. An ellipsoidal object submerged in water is considered. Both the low and high backscattered frequency data have been employed to calculate the illuminated lengths. The calculated results show that the illuminated lengths will be more accurate, if only the high-frequency-range data are employed. For ellipsoidal objects, any three illuminated lengths that are not of a same plane can in theory fully determine the shape of the ellipsoid. As the calculated illuminated lengths contain numerical errors, the calculated results of the three semiaxes of the ellipsoid will deteriorate and become unreliable, especially when the three incident directions of the illuminated lengths become close. The reason is that the condition number of the coefficient matrix becomes big in such situations, which leads to an increase of the relative error upper limit in the calculated results. To avoid such errors in close incident wave cases, it is found that the use of more than three incident waves works very well in the shape identification of an underwater object.
Enhancing interaural-delay-based extents of laterality at high frequencies by using “transposed stimuli”
Authors: Bernstein Leslie R. , Trahiotis Constantine
Published: May 2003

An acoustic pointing task was used to determine whether interaural temporal disparities (ITDs) conveyed by high-frequency “transposed” stimuli would produce larger extents of laterality than ITDs conveyed by bands of high-frequency Gaussian noise. The envelopes of transposed stimuli are designed to provide high-frequency channels with information similar to that conveyed by the waveforms of low-frequency stimuli. Lateralization was measured for low-frequency Gaussian noises, the same noises transposed to 4 kHz, and high-frequency Gaussian bands of noise centered at 4 kHz. Extents of laterality obtained with the transposed stimuli were greater than those obtained with bands of Gaussian noise centered at 4 kHz and, in some cases, were equivalent to those obtained with low-frequency stimuli. In a second experiment, the general effects on lateral position produced by imposed combinations of bandwidth, ITD, and interaural phase disparities (IPDs) on low-frequency stimuli remained when those stimuli were transposed to 4 kHz. Overall, the data were fairly well accounted for by a model that computes the cross-correlation subsequent to known stages of peripheral auditory processing augmented by low-pass filtering of the envelopes within the high-frequency channels of each ear.
Experimental and numerical investigations of axisymmetric wave propagation in cylindrical pipe filled with fluid
Authors: Pan Haitao , Koyano Kiyoshi , Usui Yoshiko
Published: May 2003

Acoustic wave propagation in fluid-filled cylindrical pipe with arbitrary thickness is investigated numerically and experimentally. The vibrational properties of the coupled fluid-pipe system are evaluated by a layerwise approach, which is similar to the finite-strip method. In this approach, the thick cylindrical wall is divided into a number of thin cylindrical layers in the thickness direction. The displacements in the thickness direction for each layer are approximated by linear-shape functions. The governing equation is obtained by using an energy minimization principle. The dispersion curves, distribution of vibrational energy between pipe wall and contained fluid, and displacement fields are examined. The dependence of the dispersion curves on wall thickness is discussed. Two PZT ring transducers adhered to the outer surface of pipe are used as source and receiver, respectively. The propagating waves generated by burst signals are measured. To localize transient signal both in time and frequency domains, the discrete wavelet transform is applied to decomposing the receiving signal into several components. Each component is limited to a narrower bandwidth. Therefore the frequency-dependent group velocity is estimated. The experimental and numerical results are compared.
Further efforts to predict pure-tone thresholds from distortion product otoacoustic emission input/output functions
Authors: Gorga Michael P. , Neely Stephen T. , Dorn Patricia A. , Hoover Brenda M.
Published: May 2003

Recently, Boege and Janssen [J. Acoust. Soc. Am. 111, 1810–1818 (2002)] fit linear equations to distortion product otoacoustic emission (DPOAE) input/output (I/O) functions after the DPOAE level (in dB SPL) was converted into pressure (in μPa). Significant correlations were observed between these DPOAE thresholds and audiometric thresholds. The present study extends their work by (1) evaluating the effect of frequency, (2) determining the behavioral thresholds in those conditions that did not meet inclusion criteria, and (3) including a wider range of stimulus levels. DPOAE I/O functions were measured in as many as 278 ears of subjects with normal and impaired hearing. Nine f2 frequencies (500 to 8000 Hz in 12-octave steps) were used, L2 ranged from 10 to 85 dB SPL (5-dB steps), and L1 was set according to the equation L1=0.4L2+39 dB [Kummer et al., J. Acoust. Soc. Am. 103, 3431–3444 (1998)] for L2 levels up to 65 dB SPL, beyond which L1=L2. For the same conditions as those used by Boege and Janssen, we observed a frequency effect such that correlations were higher for mid-frequency threshold comparisons. In addition, a larger proportion of conditions not meeting inclusion criteria at mid and high frequencies had hearing losses exceeding 30 dB HL, compared to lower frequencies. These results suggest that DPOAE I/O functions can be used to predict audiometric thresholds with greater accuracy at mid and high frequencies, but only when certain inclusion criteria are met. When the SNR inclusion criterion is not met, the expected amount of hearing loss increases. Increasing the range of input levels from 20–65 dB SPL to 10–85 dB SPL increased the number of functions meeting inclusion criteria and increased the overall correlation between DPOAE and behavioral thresholds.
Short-time fractional Fourier methods for the time-frequency representation of chirp signals
Authors: Capus Chris , Brown Keith
Published: May 2003

The fractional Fourier transform (FrFT) provides a valuable tool for the analysis of linear chirp signals. This paper develops two short-time FrFT variants which are suited to the analysis of multicomponent and nonlinear chirp signals. Outputs have similar properties to the short-time Fourier transform (STFT) but show improved time-frequency resolution. The FrFT is a parameterized transform with parameter, α, related to chirp rate. The two short-time implementations differ in how the value of α is chosen. In the first, a global optimization procedure selects one value of α with reference to the entire signal. In the second, α values are selected independently for each windowed section. Comparative variance measures based on the Gaussian function are given and are shown to be consistent with the uncertainty principle in fractional domains. For appropriately chosen FrFT orders, the derived fractional domain uncertainty relationship is minimized for Gaussian windowed linear chirp signals. The two short-time FrFT algorithms have complementary strengths demonstrated by time-frequency representations for a multicomponent bat chirp, a highly nonlinear quadratic chirp, and an output pulse from a finite-difference sonar model with dispersive change. These representations illustrate the improvements obtained in using FrFT based algorithms compared to the STFT.
Note on informational masking (L)
Authors: Durlach Nathaniel I. , Mason Christine R. , Kidd Gerald , Arbogast Tanya L. , Colburn H. Steven , Shinn-Cunningham Barbara G.
Published: May 2003

Informational masking (IM) has a long history and is currently receiving considerable attention. Nevertheless, there is no clear and generally accepted picture of how IM should be defined, and once defined, explained. In this letter, consideration is given to the problems of defining IM and specifying research that is needed to better understand and model IM.
Recovering the Green’s function from field-field correlations in an open scattering medium (L)
Authors: Derode Arnaud , Larose Eric , Tanter Mickael , de Rosny Julien , Tourin Arnaud , Campillo Michel , Fink Mathias
Published: May 2003

The possibility of recovering the Green’s function from the field-field correlations of coda waves in an open multiple scattering medium is investigated. The argument is based on fundamental symmetries of reciprocity, time-reversal invariance, and the Helmholtz–Kirchhoff theorem. A criterion is defined, indicating how sources should be placed inside an open medium in order to recover the Green’s function between two passive receivers. The case of noise sources is also discussed. Numerical experiments of ultrasonic wave propagation in a multiple scattering medium are presented to support the argument.
Nonlinear interaction of plane ultrasonic waves with an interface between rough surfaces in contact
Authors: Pecorari Claudio
Published: May 2003

A theoretical investigation of the nonlinear interaction between an acoustic plane wave and an interface formed by two rough, nonconforming surfaces in partial contact is presented. The macroscopic elastic properties of such a nonlinear interface are derived from micromechanical models accounting for the elastic interaction that is characteristic of spherical bodies in contact. These results are used to formulate set of boundary conditions for the acoustic field, which are to be enforced at the imperfect interface. The scattering problem is solved for plane wave incidence by using a simple perturbation approach and the harmonic balance method. Sample results are presented for arbitrary wave polarization and angle of incidence. The relative magnitude of the nonlinear signals and their potential use toward the nondestructive evaluation of imperfect interfaces are assessed. In particular, attention is drawn to the enhanced nonlinear response of an interface insonified by a shear vertical wave in the neighborhood of the longitudinal critical angle. The motivation for this investigation is provided by the need to develop nondestructive methods to detect and localize small, partially closed cracks in metals with coarse microstructures.
Temporary threshold shifts and recovery following noise exposure in the Atlantic bottlenosed dolphin (Tursiops truncatus)
Authors: Nachtigall Paul E. , Pawloski Jeffrey L. , Au Whitlow W. L.
Published: May 2003

Behaviorally determined hearing thresholds for a 7.5-kHz tone for an Atlantic bottlenosed dolphin (Tursiops truncatus) were obtained following exposure to fatiguing low-frequency octave band noise. The fatiguing stimulus ranged from 4 to 11 kHz and was gradually increased in intensity to 179 dB re 1 μPa and in duration to 55 min. Exposures occurred no more frequently than once per week. Measured temporary threshold shifts averaged 11 dB. Threshold determination took at least 20 min. Recovery was examined 360, 180, 90, and 45 min following exposure and was essentially complete within 45 min.
On the importance of early reflections for speech in rooms
Authors: Bradley J. S. , Sato H. , Picard M.
Published: May 2003

This paper presents the results of new studies based on speech intelligibility tests in simulated sound fields and analyses of impulse response measurements in rooms used for speech communication. The speech intelligibility test results confirm the importance of early reflections for achieving good conditions for speech in rooms. The addition of early reflections increased the effective signal-to-noise ratio and related speech intelligibility scores for both impaired and nonimpaired listeners. The new results also show that for common conditions where the direct sound is reduced, it is only possible to understand speech because of the presence of early reflections. Analyses of measured impulse responses in rooms intended for speech show that early reflections can increase the effective signal-to-noise ratio by up to 9 dB. A room acoustics computer model is used to demonstrate that the relative importance of early reflections can be influenced by the room acoustics design.
Local interaction simulation approach to modelling nonclassical, nonlinear elastic behavior in solids
Authors: Scalerandi Marco , Agostini Valentina , Delsanto Pier Paolo , Van Den Abeele Koen , Johnson Paul A.
Published: May 2003

Recent studies show that a broad category of materials share “nonclassical” nonlinear elastic behavior much different from “classical” (Landau-type) nonlinearity. Manifestations of “nonclassical” nonlinearity include stress–strain hysteresis and discrete memory in quasistatic experiments, and specific dependencies of the harmonic amplitudes with respect to the drive amplitude in dynamic wave experiments, which are remarkably different from those predicted by the classical theory. These materials have in common soft “bond” elements, where the elastic nonlinearity originates, contained in hard matter (e.g., a rock sample). The bond system normally comprises a small fraction of the total material volume, and can be localized (e.g., a crack in a solid) or distributed, as in a rock. In this paper a model is presented in which the soft elements are treated as hysteretic or reversible elastic units connected in a one-dimensional lattice to elastic elements (grains), which make up the hard matrix. Calculations are performed in the framework of the local interaction simulation approach (LISA). Experimental observations are well predicted by the model, which is now ready both for basic investigations about the physical origins of nonlinear elasticity and for applications to material damage diagnostics.
Optimization of acoustic scattering from dual-frequency driven microbubbles at the difference frequency
Authors: Wyczalkowski Matthew , Szeri Andrew J.
Published: May 2003

The second harmonic radiation of acoustically driven bubbles is a useful discriminant for their presence in clinical ultrasound applications. It is useful because the scatter from a bubble at a frequency different from the driving can have a contrast-to-tissue ratio better than at the drive frequency. In this work a technique is developed to optimize the scattering from a microbubble at a frequency different from the driving. This is accomplished by adjusting the relative phase and amplitudes of the components of a dual-frequency incident ultrasound wave form. The investigation is focused primarily on the example of dual-mode driving at frequencies of 1 MHz and 3 MHz, with the scattering optimized at 2 MHz. Bubble radii of primary interest are 0.5 to 2 μm and driving amplitudes to 0.5 atm. Bubbles in this size range are sensitive to modulation of driving. It is shown that an optimal forcing scheme can increase the target response eightfold or more. This suggests new applications in imaging and in bubble detection.
Children’s detection of pure-tone signals: Informational masking with contralateral maskers
Authors: Wightman Frederic L. , Callahan Michael R. , Lutfi Robert A. , Kistler Doris J. , Oh Eunmi
Published: May 2003

When normal-hearing adults and children are required to detect a 1000-Hz tone in a random-frequency multitone masker, masking is often observed in excess of that predicted by traditional auditory filter models. The excess masking is called informational masking. Though individual differences in the effect are large, the amount of informational masking is typically much greater in young children than in adults [Oh et al., J. Acoust. Soc. Am. 109, 2888–2895 (2001)]. One factor that reduces informational masking in adults is spatial separation of the target tone and masker. The present study was undertaken to determine whether or not a similar effect of spatial separation is observed in children. An extreme case of spatial separation was used in which the target tone was presented to one ear and the random multitone masker to the other ear. This condition resulted in nearly complete elimination of masking in adults. In young children, however, presenting the masker to the nontarget ear typically produced only a slight decrease in overall masking and no change in informational masking. The results for children are interpreted in terms of a model that gives equal weight to the auditory filter outputs from each ear.
Scattering of elastic waves in damaged media
Authors: Yang Liyong , Turner Joseph A.
Published: May 2003

The scattering of elastic waves in a medium with damage from microcracking is discussed. The influence of damage from penny-shaped microcracks within a homogeneous medium is considered. The microcracks are assumed to be randomly oriented and uniformly distributed. Explicit expressions are derived for the attenuation of longitudinal and shear elastic waves in terms of the damage parameter and the effective elastic moduli of the medium. A generalized tensor-based approach is used such that the results are coordinate free. The derivation is based upon diagrammatic methods. The problem is formulated in terms of the Dyson equation, which is solved for the mean field response within the limits of the first-order smoothing approximation. The longitudinal and shear attenuations are discussed in terms of their frequency dependence and damage dependence. In particular, the attenuations are shown to scale linearly with the damage parameter.
Examination of time-reversal acoustics in shallow water and applications to noncoherent underwater communications
Authors: Smith Kevin B. , Abrantes Antonio A. M. , Larraza Andres
Published: May 2003

The shallow water acoustic communication channel is characterized by strong signal degradation caused by multipath propagation and high spatial and temporal variability of the channel conditions. At the receiver, multipath propagation causes intersymbol interference and is considered the most important of the channel distortions. This paper examines the application of time-reversal acoustic (TRA) arrays, i.e., phase-conjugated arrays (PCAs), that generate a spatio-temporal focus of acoustic energy at the receiver location, eliminating distortions introduced by channel propagation. This technique is self-adaptive and automatically compensates for environmental effects and array imperfections without the need to explicitly characterize the environment. An attempt is made to characterize the influences of a PCA design on its focusing properties with particular attention given to applications in noncoherent underwater acoustic communication systems. Due to the PCA spatial diversity focusing properties, PC arrays may have an important role in an acoustic local area network. Each array is able to simultaneously transmit different messages that will focus only at the destination receiver node.
Experimental studies of applications of time-reversal acoustics to noncoherent underwater communications
Authors: Heinemann M. , Larraza A. , Smith K. B.
Published: May 2003

The most difficult problem in shallow underwater acoustic communications is considered to be the time-varying multipath propagation because it impacts negatively on data rates. At high data rates the intersymbol interference requires adaptive algorithms on the receiver side that lead to computationally intensive and complex signal processing. A novel technique called time-reversal acoustics (TRA) can environmentally adapt the acoustic propagation effects of a complex medium in order to focus energy at a particular target range and depth. Using TRA, the multipath structure is reduced because all the propagation paths add coherently at the intended target location. This property of time-reversal acoustics suggests a potential application in the field of noncoherent acoustic communications. This work presents results of a tank scale experiment using an algorithm for rapid transmission of binary data in a complex underwater environment with the TRA approach. A simple 15-symbol code provides an example of the simplicity and feasibility of the approach. Covert coding due to the inherent scrambling induced by the environment at points other than the intended receiver is also investigated. The experiments described suggest a high potential in data rate for the time-reversal approach in underwater acoustic communications while keeping the computational complexity low.
Resolution enhancement and separation of reverberation from target echo with the time reversal operator decomposition
Authors: Folégot Thomas , Prada Claire , Fink Mathias
Published: May 2003

Time reversal operator (TRO) decompositions are performed in a model of an ocean wave guide containing a target and having different kinds of bottom. The objective is to study the effects of bottom reverberation and absorption by means of ultrasonic experiments. It is shown experimentally that the echo from a target can be separated from the bottom reverberation. Reverberation eigenvectors are back propagated in the wave guide leading to focus on the bottom. An amplitude correction is applied to both reverberation and signal eigenvectors to compensate for bottom absorption and thus to improve target resolution.
Response of strings to turbulence—Redux (L)
Authors: Lyon Richard H.
Published: May 2003

An unresolved issue in the author’s Ph.D. thesis concerned the relation between turbulent flow speed and the maximum response of a string excited by the turbulence. The maximum response occurred at a flow speed significantly less than that predicted. This discrepancy was not resolved at the time, but can be resolved if one notes that the flow excitation is dispersive, with longer scale disturbances that flow faster than smaller scale disturbances. It is suggested that string response to turbulence may be a useful way to determine small-scale properties of a turbulent flow.