bluuebunny/crossref_metadata_2025 huggingface dataset:
The Huygens Surface Science Package sound speed measurements and the methane content of Titan's atmosphere
Authors: Hagermann A. , Towner Martin C. , Rosenberg Philip D. , Garry James R. , Svedhem Hakan , Leese Mark R. , Hathi Brijen , Lorenz Ralph D. , Zarnecki John C.
Published: May 2008

The Huygens probe descended through Titan's atmosphere in January 2005. On board was the Surface Science Package (SSP), a set of nine sensors, which included a speed-of-sound sensor. We present a detailed description of the SSP speed of sound measurements and report constraints on the methane content in Titan's lower atmosphere based on these measurements. After extensive instrument calibration and subsequent Bayesian analysis of the data, the most likely result derived from our measurements in Titan's lower atmosphere is a methane fraction of approximately 2% at 10 km, increasing to 3.5% at lower altitudes. These estimates are based on a binary composition. Our data show that any large scale variation of methane within the lower 11 km of Titan's atmosphere is unlikely. Within experimental and theoretical uncertainties, our estimates are lower than, but compatible with earlier estimates obtained from the mass spectrometry experiment.
Waterfalls in space, and other problems of 'underwater' acoustics on a small planet
Authors: Leighton Timothy G. , White Paul R. , Finfer Daniel C.
Published: May 2008

Whilst extraterrestrial liquids do occur in the Solar System, today's acoustical oceanographers have fewer sites to which they can apply their experience of Earth's oceans than perhaps they would have had in the early Solar System, with its magma oceans. Possible sites are Saturn's moons Titan and Enceladus, and Jupiter's moon Europa. The ability to transfer our understanding of Earth's acoustical oceanography to other moons and planets is particularly valuable, given that current understanding is sufficient to undertake complex inversions to estimate Earth's ocean environmental parameters from relatively sparse, or even naturally-occurring, acoustical signals. However such transference should be done with care, as terms familiar in Earth's acoustical oceanography may not be correct on other worlds. For example, in a deep ocean on a small world (such as Europa), the hydrostatic pressure will not equal the product of the density, the depth, and the surface value of the acceleration due to gravity, since the latter can vary with depth, and because vertical lines are not parallel on a small planet. This paper explores two cases of transferring our terrestrial experience off world, to the ice seas of Europa, and to the methane lakes and waterfalls of Titan.
Flow field and acoustic characteristics of an acoustically forced burner impinging jet
Authors: Zhang Yang , Hajim Saad , Bassi Jason , Farhat S
Published: May 2008

The flow field and acoustic characteristics of a turbulent impinging jet from an impinging burner have been investigated experimentally. The effect of acoustically excited upstream flow with a range of driving frequencies from 0 to 3000Hz and use of perforated plate near the nozzle have been studied to achieve modifications to the near-field and far-field of the jet. The acoustic response of the burner to upstream acoustically excited flow under different geometry configurations was investigated in detail. The burner components were found to have a significant effect on the burner acoustic response, with overall damping and enhancement achieved over the full driving frequency range. The velocity flow field of the impinging jet, including spectra and rms data, were mapped from the burner nozzle to the plate with CTA measurements with three acoustic excitation frequencies and no excitation; 0Hz, 52.5Hz, 75Hz and 530Hz (within acoustic mode bands of burner).The results show that excitation frequencies of 52.5Hz and 75Hz were found to propagate all the way to the plate, whilst 530Hz dissipates near the nozzle exit. (Re = 16,200 , H/D = 3, nozzle velocity profile).
Mode switching of combustion instabilities associated with flame transfer function non-linearities
Authors: Durox Daniel , Noiray Nicolas , Schuller Thierry , Candel Sebastien
Published: May 2008

Studies of combustion instabilities indicate that the frequency of oscillation changes during the growth of oscillations before a limit cycle is reached. It is also found that a system can switch from one mode to another when the amplitude exceeds a certain threshold. It is shown that these features can be linked to the flame response non-linearity. The analysis is carried out by examining combustion instabilities appearing on a multipoint injection burner, placed a the end of a cylindrical manifold. This element acts like a resonator and its length can be modified easily. Experiments indicate that mode switching takes place between two resonant modes of the cavity and this is shown to be caused by the non-linearity of the flame response. The phenomenon can be analyzed by considering the non-linear evolution of the flame transfer function. It is possible to combine this information with a stability analysis of the burner, and define conditions which give rise to mode switching. It is found that this behavior is related to a change in phase difference between heat release rate fluctuations and velocity perturbations at the burner outlet. This phase shift takes place as the amplitude of oscillation increases.
Computation of Indirect Combustion Noise by a CAA Method
Authors: Richter Christoph , Thiele Frank H.
Published: May 2008

Indirect combustion noise, which is generated by the acceleration of hot gases from a turbulent swirling flame, has become an important issue to understand turbo-machinery core noise. This indirect combustion noise it is dominated by a strong interaction of hydrodynamic and acoustic perturbations due to the transonic base flow in the turbine stages and combustion chamber exit nozzle. Current numerical simulation methods for the phenomenon based on compressible Large Eddy Simulation (LES) are very expansive. Thus LES applications are still limited to one design or few variations with immense computational costs. The most simple model fully covering indirect combustion noise, are the linearized non-isentropic Euler equations over an arbitrary mean flow. Therefore the gap between theory and LES is closed by a method adopted from Computational Aeroacoustics (CAA). It combines a high cost efficiency in terms of required points per wavelength with a high adaptability to realistic mean flow conditions. The CAA method is first validated with a simplified experiment and then applied to predict the acoustic properties of two model combustion chambers, one of them with transonic termination nozzle. By means of the acoustic intensity the sources of the noise are located.
Study of oscillating regimes in air-staged diffusion flames
Authors: Ballester Javier , Hernández Ricardo , Sanz Ana
Published: May 2008

The occurrence of fluctuating behaviours in air-staged diffusion flames was studied experimentally in a gas-fired furnace. Burner settings (swirl levels, air distribution) were systematically varied, leading to a broad range of flame characteristics and pollutant emissions. Pressure fluctuations reached significant amplitudes and displayed characteristic frequencies for certain operating conditions. However, heat release fluctuations (as estimated from OH* chemiluminescence) were correlated with pressure only in a part of those cases. Therefore, thermo-acoustic coupling is thought to exist only under certain conditions, whereas other oscillating regimes are not ascribed to acoustic feedback but to changes in the location of the flame stabilization region. This conclusion was supported by the values of the Rayleigh index calculated for the different regimes. An enhanced tendency to the onset of thermo-acoustic instabilities was observed for highly staged flames.
Elastic constants identification of anisotropic composite rectangular parallelepipeds
Authors: Delaunay Thomas , Laux Didier , Ferrandis Jean-Yves
Published: May 2008

For many years, composite materials have been investigated due to their potential in many applications such as nuclear fuel. Nowadays, the improvement of structure conception and simulation requires many reliable properties, especially the entire elastic tensor. For these reasons, the implementation of simulation and characterization methods adapted to the geometry of samples and the high anisotropy degree of such materials are then crucial issues to developers and end users. The work presented here reports first macroscopic properties of two composites Duralumin/Air and Duralumin/Tungsten Carbide) calculated using periodical homogenization method from elastic constants of each phase measured by high frequency acoustic microscopy. Then a resonant ultrasonic spectroscopy method is used to identify the entire elastic tensor. First, computation predicting the resonant frequencies and the mode shapes of free vibrations of cubes are presented. Excitation is then ensured by ultrasonic transducers and detection is performed by means of a laser vibrometer. A fit process of the theoretical frequencies on the measured data is then described. This method allows us to conclude about the accuracy of the homogenization method.
Ultrasonic and photoacopustic investigations of water mixtures with dioxanes 1-3 & 1-4
Authors: Linde Bogumil B. , Kiszel Anna K. , Sikorska Anna
Published: May 2008

Ultrasonic velocities, densities and thermal effusivity dependence on concentration were measured in the mixtures of water with dioxanes 1-3 and 1-4 in the temperature range from 291.15 to 303.15 K. Adiabatic compressibilities were calculated from Laplace's equation based on the experimental results obtained. Variations of these values with concentration and temperature were studied. Structural interactions and the formation of a compact pseudo-stable structure at very low concentrations of these liquids were observed. The plots of the adiabatic compressibility versus the mole fraction of these molecules display two characteristic points at low concentrations: the intersection of the isotherms and their minimum. Such relations between adiabatic compressibility, concentration and temperature are usually attributed to the formation of pseudo-stable molecular structures. To formulate a model of local structures present in the investigated molecular systems it is indispensable to get an insight into hydration of molecules and the formation of hydrogen bonds. Therefore, the attention was focused particularly on these problems.
Bonding quality evaluation of layered materials by guided wave dispersion
Authors: Kim Young H. , Bae Minseok , Choi Sunhee , Kim Jisu , Hong Seokchan
Published: May 2008

Multi-layered materials have been widely used for high performance materials with advanced properties required for the critical parts of structures. The characteristics of bonding quality in multi-layered materials have been hot issue for a long time. The bonding quality was evaluated by using dispersion of guided wave. Broadband guided waves were generated at oblique incidence angle, and waves reflected at the edge of the specimen were detected by using a pulse-echo setup. The dispersion curves were obtained from edge-reflected leaky guided wave for various plates: Single layered plates of aluminum, copper and stainless steel, and double layered plates of aluminum-stainless steel cladding, epoxy-bonded aluminum-stainless and epoxy-bonded aluminum-copper. The aluminum-stainless steel cladding specimen showed similar dispersion for both sides, whereas epoxy-bonded specimens showed different dispersions which are similar to that of upper layer only. These results imply that the cladding specimen used in the present work is well bonded, whereas epoxy-bonded specimens are acoustically isolated. The dispersion curve of guided wave has high potential to evaluate bonding quality of layered materials.
An experimental method of corrugated surface reconstruction investigated in combination with finite-element simulation
Authors: Herbison Sarah W. , Lamkanfi Ebrahim , Declercq Nico F.
Published: May 2008

Current theory applied to ultrasonic diffraction from periodically corrugated surfaces is valid only in the far-field; it cannot be applied to determine the diffracted field within the surface corrugations themselves. Therefore, information regarding the corrugation is difficult to extract from experiments that are necessarily conducted in the far-field. The present work aims to simulate a potential experimental method for investigating the corrugations themselves. Using near-field results obtained from a finite-element code, the far-field diffraction is constructed as a series of time-harmonic plane waves. By back-propagating this diffracted field, information about the corrugations is obtained. Comparing the results of the back-propagated field to the field generated by the finite-element code shows the limitations of determining details of periodically corrugated surfaces from far-field experiments.
Diffuse ultrasonic backscatter at oblique incidence for heterogeneous solids
Authors: Turner Joseph A. , Ghoshal Goutam
Published: May 2008

Diffuse ultrasonic backscatter techniques are useful for probing heterogeneous materials. They can be used to extract microstructural parameters and to detect flaws which cannot be detected by conventional ultrasonic techniques. Such experiments, usually done using a modified pulse-echo technique, utilize the spatial variance of the signals as a primary measure of microstructure. Quantitative ultrasonic scattering models include components of both transducer beams as well as microstructural scattering information. Of particular interest for interpretation of many experiments is the propagation through a liquid-solid interface at normal and oblique incidence. Here, the Wigner distribution of the beam pattern of an ultrasonic transducer through a liquid-solid interface is used in conjunction with the stochastic wave equation to model this scattering problem within a single scattering formulism. The Wigner distribution represents a distribution in space and time of the spectral energy density as a function of wave vector and frequency. A Gaussian beam is used to model the transducer beam pattern. The scattered response in the time domain is then compared with experimental results for materials of common interest. These results are anticipated to impact ultrasonic nondestructive evaluation and characterization of heterogeneous media.
Psychoacoustic evaluation of compression drives
Authors: Cruanes Catala Joan , Frances Monllor Jorge , Ramis Soriano Jaime , Alba Fernandez Jesús
Published: May 2008

The following work tries to be an approximation to the sound quality valuation of radiant systems, in concrete, the case of compression drives. This approach is realized from different perspectives: on one hand, an evaluation of the quality of these systems from the point of view of the psychoacoustic classic parameters described by Zwicker will be done. On the other hand, a perceptual model described by Moore and based on the human auditory system will be applied. Both models will be applied in signals registered on different commercial models of compression drives. The work also includes the accomplishment of a psychoacoustic experiment in which a hearing will realize a valuation of perceived quality. Finally, one will try to establish a correlation with the information obtained in the three mentioned approaches.
A study of evaluating the button sounds
Authors: Ishimitsu Shunsuke , Sakamoto Koji , Arai Takayuki , Yoshimi Toshikazu , Fujimoto Yuichi , Kawasaki Kenichi
Published: May 2008

In recent years, much attention has been directed at the sound design which designs various sound treated as noise, such as automobile acceleration sound and cleaner sound, because the point of view sound is a part of products, has permeated. This research considered the sound design and its evaluation about 11 kinds of the button sounds. First, the impression was extracted by the SD method and relevance with time frequency analysis was investigated. Moreover, we also confirmed that an impression changed, when the sound of a bad impression is processed into the sound of a good impression using adaptive control.
Non-visual identification of walking grounds
Authors: Giordano Bruno L. , McAdams Stephen , Visell Yon , Cooperstock Jeremy , Yao Hsin-Yun , Hayward Vincent
Published: May 2008

We investigated the role of haptic, proprioceptive and auditory information in the non-visual identification of walking grounds. We selected four solid materials (e.g., marble) and four aggregate materials (e.g., fine gravel). Five observers identified the materials in each of four experimental conditions: multisensory, haptic, proprioceptive, and auditory. In the auditory condition, they were presented with walking sounds they produced. In the other conditions, observers walked blindfolded on the materials. In the haptic and proprioceptive conditions auditory information was masked. In the proprioceptive condition haptic information was masked. No masking took place in the multisensory condition. In all conditions, solids and aggregates were seldom confused, and aggregates were better identified than solids. Chance identification performance was observed only for solids in the presence of simultaneous haptic and auditory masking, suggesting a secondary role of proprioceptive information. In the proprioceptive condition, identification of aggregates was better than chance, suggesting a significant role of proprioception. Identification of aggregates was at its best in the haptic condition, and not in the multisensory condition, suggesting either an inconsistency of information between auditory and non-auditory channels, or conflicting cognitive strategies for the exploitation of these sources of information in multisensory contexts.
The effect of tone envelope on sensory integration: support for the 'unity assumption'
Authors: Schutz Michael , Kubovy Michael
Published: May 2008

Research on the integration of auditory and visual sensory information consistently confirms the optimal integration hypothesis, according to which information is weighted according to its relative quality. Thus, since the auditory system has greater temporal resolution, this hypothesis predicts that visual information will not affect auditory judgments of duration. In conflict with this hypothesis, Schutz & Lipscomb (2007) report that percussionists use visual information to alter audience perception of note duration. To show that this discrepancy arises from the acoustic characteristics of percussive sounds, we paired visual information derived from a striking motion with pure tones exhibiting two types of envelopes: percussive (sharp onset followed by exponential decay) and flat (sharp onset to a fixed level, followed by sharp offset) envelopes. Visual information affected auditory duration judgments only for the tones with percussive envelopes (e.g. the sounds produced by a striking motion). As ratings of percussive tones were no more variable than ratings of flat tones, the difference cannot be explained by "ambiguity" of percussive-tone duration. In contrast to the notion of optimal integration, we conclude that envelope is an important acoustic cue for cross-modal integration and offers important information regarding event identification.
Size from sound: Size estimates of balls dropped from various height
Authors: Grassi Massimo
Published: May 2008

Three experiments investigated the perception of the size of a ball (i.e., a non sounding object) from the sound it produces when dropped upon a plate (i.e., a sounding object) from various heights. Experiment one: listeners estimated metrically the size of seven balls (Ø 1, 1.5, 2, 2.5, 3, 4, 5 cm) when dropped upon a baked clay plate from 6 cm of height. Experiment two: a new group of listeners estimate the size of the balls, however, balls could be dropped from either 6 cm or 12 cm of height. In the last experiment, balls could be dropped from either 3, 6 or 12 cm of height. In all experiments listeners received no foregoing information about the sound source event, such as the material of the balls, the material of the plate, etc. Overall, listeners' estimations matched veridically the actual size of the balls. However, in the second and third experiment, listeners' estimations were dependent on the height: balls were judged slightly larger when dropped from the highest heights.
The texture of natural sounds
Authors: Andringa Tjeerd C.
Published: May 2008

The texture, a spectro-temporal pattern, of many sound sources is a robust and characteristic perceptual property that listeners use for sound source recognition. The robustness of the texture ensures that we can recognize sound sources like a helicopter, flowing water, or a surf breaking on pebbles in a wide variety of acoustic environments. This robustness suggests that textures can be used for automatic source identification or environment classification. We introduce a method to determine the presence of sound textures associated with, for example, flat noise, pulsed noises (helicopter), sweep based textures (running water), and tonal noises (babble). The cumulative probability density of time-frequency fluctuations are matched with prototypical cumulative probability density functions (cpdf) with a running variant of the Kolmogorov-Smirnov test. Textures with a similar distribution as the target distribution, contribute approximately equally to all values of the cpdf. The flatness of this distribution is used as a distance measure. When the pdf's of the target textures do not overlap strongly, the method can determine the texture of time-frequency-regions as small as 100 ms by 6 semi-tones. This method can therefore also be used to determine the texture of the background.
Auditory Perception of Silent Object Properties
Authors: Rosenblum Lawrence D.
Published: May 2008

While much of what we consciously hear is based on sound sources, we also hear properties of objects that are themselves silent, but act to reflect and obstruct sound. A research program has been initiated to examine the degree to which listeners can judge properties of silent, sound-structuring objects. Results of this research have revealed impressive sensitivity to many of these properties. Thus far, this work has shown that (sighted) listeners have some ability to: a) determine the location, dimensions, and general shape of sound-obstructing panels; and b) identify various rooms based on how rooms structure emitted sounds; and c) determine their location in a room based on how the room structures sound at different positions. These results indicate that listeners are sensitive to ambient, as well as emitted acoustic properties, and call for a modified conception of human audition that takes into account these sensitivities.
Source Perception of Everyday and Self Produced Sounds: Factors in the Evolution of Human Auditory Cognitive Capability
Authors: Ballas James
Published: May 2008

The everyday world was making meaningful sound well before language developed. Self-produced sound exhibits a tight binding between source event and interpretation. These assertions naturally prompt thoughts about the role of these types of sound in the evolution of human auditory capability, especially language. The recent resurgence in theorizing about the origin of language has included other human capabilities as potential generative factors (e.g., gestures), but there has been little discussion about the possible role of capability to process everyday and self-produced sound. This is surprizing given that recent neurocognitive research has supported common processing for speech and meaningful sound. Key attributes of language processing are the ability to interpret not just signs but symbols, and the ability to employ generative grammar processing to produce and interpret symbol strings. Association of sound events with causes and sequences, auditory representation of meaning, persistence of meaning under event and sequence variation, and persistence of event interpretations beyond what is currently present (temporal and spatial abstraction) are all fundamental requirements for these language attributes, and it is asserted that these capabilities might have developed to accurately perceive everyday and self-produced sound.
The salience of interaural temporal disparities (ITDs) conveyed by high-frequency signals is determined by the temporal features of their ongoing envelopes
Authors: Trahiotis Constantine , Bernstein Leslie R.
Published: May 2008

Many studies of binaural hearing reveal that envelopes of complex, high-frequency stimuli convey useful interaural time differences (ITDs). Envelope-based ITDs have, typically, been found to be less "potent" than those conveyed by low-frequency waveforms. When considering such findings, Blauert, in his classic textbook, noted that monaural, peripheral processing would result in 1) low-frequency inputs to the binaural processor that are essentially half-wave rectified versions of the input waveforms and 2) high-frequency inputs that are essentially full-wave rectified versions of only the envelopes of the input waveforms. Taking this into account, Blauert, echoing Colburn and Esquissaud (1976), surmised that low-frequency signals would ultimately convey "more distinct time cues" having greater "transient features" than would high-frequency signals and, therefore, be expected to provide more precise ITD information. By using high-frequency "transposed" stimuli having envelopes constructed to provide "more distinct time cues" we have shown in a variety of experimental contexts that the potency of envelope-based ITDs, can rival that measured with low-frequency stimuli. Our most recent experiments use "raised sine stimuli" in order to vary directly the temporal features of the envelope waveform including its "sharpness," "off-time," and interaural cross-correlation function. The new data will be discussed in terms of Blauert's insight.
Fast multipole accelerated boundary element method (FMBEM) for solution of 3D scattering problems
Authors: Gumerov Nail A. , Duraiswami Ramani
Published: May 2008

Wideband FMBEM codes are challenging to implement since there are problems at both very low and high frequencies. Substantially different schemes for function representation and translation are efficient for low and high frequency ranges. We present a method which is suitable for solution both high and low frequency problems since it implements a switch between different representations and uses fast translation methods appropriate to each representation. For a high frequency problem the switch between representations may occur at some intermediate levels of hierarchical space subdivision of the FMM. We also present an FMM-based preconditioner used in the flexible GMRES iterative solver for scattering problems and discuss example problems computed in range 0.001<kD<200, where k is the wave number and D is the size of the computational domain. The theoretical and experimental computational complexity of our algorithm is approximately O((kD)3) at large kD with relatively small asymptotic constant and the algorithm allows to solve problems with up to million nodes used for surface discretization in the range tested on a conventional personal computer.
A 3 dimensional finite element modeling of "smart foam" and its experimental validation
Authors: Leroy Pierre M. , Atalla Noureddine , Berry Alain , Herzog Philippe
Published: May 2008

The "smart foam" concept and design originate from the combination of passive dissipation of acoustic foams in the medium and high frequency range and the active absorption ability of piezoelectric actuators (generally PVDF) in the low frequency range. This results in a passive/active absorption control device that can efficiently operate over a broad range of frequencies. In this paper, a 3D finite element model of smart foam and its experimental validation are presented. The finite element model uses quadratic poroelastic elements with a (u,p) formulation, as well as elastic, fluid and piezoelectric elements. The weak integral formulation of the different involved domains and their coupling conditions are presented. In particular, an isotropic and a simplified orthotropic model of poroelastic media are presented and compared. The fabrication of a prototype smart foam based on melamine foam with a curved, bonded PVDF film is discussed. Passive absorption and acoustic radiation of this prototype are measured in an impedance tube. The measured data are in good agreement with the numerical results, thereby validating the finite element model. This modeling tool constitutes a powerful platform to simulate and optimize various configurations of smart foams.
Prediction of the sound field in anechoic rooms : comparison of two different approaches
Authors: Bécot François-Xavier , Schneider Stefan , Jaouen Luc
Published: May 2008

Despite the numerical advances, predicting the sound field in anechoic rooms is still challenging because it requires a fine modeling of the wall surface, acoustic properties and geometry, and the computation of the room sound field. It is proposed here to compare two innovative approaches to predict the performance of anechoic wedges, in particular to quantify the influence of porous frame motion, and to propose a numerically efficient model for the prediction of the sound field in anechoic room sounds at low frequencies. The first approach relies on the theory for modeling the sound propagation in double porosity media first presented by Olny & Boutin [J. Acoust. Soc. Am. 114 (1), 2003]. It has been shown that this approach could accurately predict the cut-off frequency of anechoic wedges. The interest is that this approach is numerically costless and that complex geometry could be considered. The second approach is based on the combination of FEM and BEM. It allows to predict the sound field in anechoic rooms. Compared to the previous approach, the latter one has the advantage of being able to identify structural effects inside the wedges and to propose an accurate prediction of the sound field in the room.
Segmental effects on the prosody of voice quality
Authors: Pfitzinger Hartmut
Published: May 2008

Voice quality variability is due to supra-segmental influences but also to segmental factors like phoneme class, vowel quality, nasalization, airstream mechanism etc. These factors determine a rather unexplored micro-prosodic phenomenon: the phone-intrinsic voice quality which causes voice quality coarticulation and voice quality transitions in fluent speech. I subsume all these phenomena under the high-frequency components of prosody. Since high-frequency and low-frequency components (supra-segmentals) of voice quality prosody are superposed and thus encoded the main goal of this paper is to separate them and make both accessible to speech research. In 2003 a holistic voice quality parameter extractor was introduced by Mokhtari, Pfitzinger, and Ishi: It applies a principal components analysis to a database of glottal-flow waveforms for the purpose of later reconstructing and interpolating all underlying glottal-flow waveforms from just a few principal components. Recently, by applying this basic principle to a large corpus of manually segmented glottal-flow waveforms of 44 speakers I dramatically improved its applicability to any speech signals. The application of this version to a large speech database and subsequent high-pass and low-pass filtering of the resulting voice quality parameters yielded phone-intrinsic voice quality parameter sets as well as slowly varying meaningful voice quality parameter contours.
Identification of talkers speaking emotional speech
Authors: Kim Kyung Wha , Wong Patrick C.
Published: May 2008

Identification of talkers speaking emotional speech is common in many communicative situations and forensic "voice line ups". However, emotional speech is auditorily and acoustically different from neutral speech, which may cause difficulty in talker identification. In this study, we examined how listeners identify different talkers speaking emotional or neutral voices, and how short-term training may benefit talker identification. Recordings were obtained from 10 male speakers speaking in angry and neutral voices. Within one session, listeners were first trained to identify the talkers, and their ability to generalize to untrained sentences spoken by the same talkers was tested. We found that while there was no significant difference in identifying neutral and angry voices, the ability to generalize to untrained sentences was more impaired with angry voices. The theoretical and forensic implications of these results are discussed. [Work supported by NIH and NSF]
An fMRI-based structural equation model for natural language processing shows age-dependent changes in brain connectivity
Authors: Holland Scott K. , Karunanayaka Prasanna , Plante Elena J. , Schmithorst Vincent J.
Published: May 2008

Structural Equation Modeling (SEM) or path analysis is a multivariate analytic tool that is used to test hypothesis about causal influences among measured or latent variables. When applied to functional neuroimaging (fMRI) data, SEM combines interregional covariance and neuroanatomy to investigate brain connectivity and the dynamic flow of information across neural networks. We have investigate Linear SEM or LSEM as a first step in estimating connection strengths from fMRI data in children during acoustic stimulation with stories in English. An average LSEM was constructed based on the concatenated fMRI data from N=313 children, age 5 to 18, listening to stories. Time courses from the fMRI data is used as input to the LSEM as computed in AMOS (v.5.1, SmallWaters, Corp. Chicago, IL) to yield an average model for the entire group. The LSEM path coefficients were examined between brain regions involved in auditory speech perception and language processing. Connectivities estimated by LSEM are significantly age dependent in some brain areas, while the connectivity coefficient between other brain regions is not a function of age.
Modeling formant pattern in fricative-vowel sequences
Authors: Toda Martine , Maeda Shinji
Published: May 2008

MRI data indicate that there are two subject-dependent articulatory patterns in French post-alveolar sibilant fricative /'integral of'/. Each type of articulations can correspond to the Polish fricatives /'curled c'/ and /'underdotted s'/ on the basis of their articulatory similarity: palatalized for the former, and the presence of a sublingual cavity as well as lip protrusion for the latter. The F2 transitions, in part, reflect the acoustic contrast between these Polish fricatives, which exhibit a higher locus in the palatalized /'curled c'/ than in /'underdotted s'/. However, no systematic transitional characteristic could be found in French. We hypothesize that the subject-specific formant-cavity affiliation in the adjacent vowel /a/ and/or the difference of scale in vocal tract lengths manifest as the acoustic variation in French, whereas those VT morphological differences are articulatorily compensated in Polish to maintain the distinctiveness of these two post-alveolar fricatives. In order to assess this hypothesis, the F-patterns along /a 'integral of' a/ sequences are simulated for various vocal tract configurations. In calculations, the two different types of the fricative articulations are combined with the vocal-tract area functions appropriate for /a/ but different in shape and in size to taken into account for female and male speakers. The results will be discussed.
Diffraction effects on speech phonemes during phonation
Authors: V Vijayakumar , C Eswaran
Published: May 2008

In this paper we will show how the ventricular fold modifies speech phonemes and also causes the shimmering of speech. Diffraction of sound waves at the ventricular fold which can be considered as a circular aperture, can modify the vocalized glottal sound spectrum reaching the pharyngx. Thus during phonation, speech phoneme spectra are essentially enveloped by Bessel functions. Since Bessel beams are known to be nondiffracting, this step ensures that the phonemes do not undergo further diffraction effects which can destroy the unique harmonic structure of the phonemes. Note that the wavelengths of sound waves and the dimensions of the human vocal tract appendages are of the same order of magnitude which mean that diffraction should be commonplace in the vocal tract if not for the initial packaging of the speech phoneme at the ventricular fold.
Acoustic-to-articulatory inversion of fricatives
Authors: Feïz Farid , Potard Blaise , Laprie Yves
Published: May 2008

The objective is to recover the vocal tract shape dynamics from the speech signal of vowels and fricatives. The method relies on the analysis-by-synthesis paradigm and is an extension of the method proposed by Ouni and Laprie which exploits a hypercubic articulatory table to represent the synthesis facet, i.e. Maeda's articulatory model. The first major modification is the use of parallelepiped instead of cubes. The new construction strategy only subdivides the articulatory space in the articulatory direction which gives rise to the strongest non-linearities. This enables a substantial reduction of the table size. The second major modification is the inversion of fricative sounds. In addition to the articulatory parameters the relative location of the noise source downstream the constriction is taken into account. This gives rise to three different articulatory codebooks, each corresponding to the relative position of the source with respect to the main constriction. This new inversion method has been evaluated on VCV sequences. It turns out that the correct vocal tract dynamics is recovered even if the constriction area is slightly underestimated. Input data are the first three formant frequencies but MFCC coefficients are now investigated since they render the high frequency region of fricative spectra better.
Quantifying rhythm in running speech
Authors: Ross Tristie , Ferjan Naja , Arvaniti Amalia
Published: May 2008

In the past decade several metrics that reflect the variability of vocalic and consonantal intervals in speech have been used to quantify the impressionistic division of languages into stress- and syllable-timed. Although all such metrics successfully separate prototypical languages, such as stress-timed English and syllable-timed Spanish, their results for other languages are less clear. The problem is related to the limited datasets used, which consist of either a small number of sentences per language elicited from several speakers, or longer stretches of speech elicited from one speaker per language. Here we elicited short sentences, story reading and spontaneous speech from several speakers of stress-timed English, syllable-timed Spanish, Korean, a hitherto unclassified language, and Greek, which has shown to resist classification. Our results show that different metrics yield different classifications for some languages, like Greek, while scores for the same language differ depending on speaking style. Taken all together these results cast doubt on the robustness and usefulness of the popular metrics and suggest that alternative ways of conceiving of speech rhythm that do not rely exclusively on timing but take relative prominence into account may ultimately be more successful in explaining speech rhythm.
Computing the fundamental frequency variation spectrum in conversational spoken dialogue systems
Authors: Laskowski Kornel , Wölfel Matthias , Heldner Mattias , Edlund Jens
Published: May 2008

Continuous modeling of intonation in natural speech has long been hampered by a focus on modeling pitch, of which several normative aspects are particularly problematic. The latter include, among others, the fact that pitch is undefined in unvoiced segments, that its absolute magnitude is speaker-specific, and that its robust estimation and modeling, at a particular point in time, rely on a patchwork of long-time stability heuristics. In the present work, we continue our analysis of the fundamental frequency variation (FFV) spectrum, a recently proposed instantaneous, continuous, vector-valued representation of pitch variation, which is obtained by comparing the harmonic structure of the frequency magnitude spectra of the left and right half of an analysis frame. We analyze the sensitivity of a task-specific error rate in a conversational spoken dialogue system to the specific definition of the left and right halves of a frame, resulting in operational recommendations regarding the framing policy and window shape.
Time-Reversal Acoustics in Biomedical Engineering
Authors: Fink Mathias , Montaldo Gabriel , Tanter Mickael
Published: May 2008

Time-reversal is a very powerful method for focusing through complex and heterogeneous media and shows very promising results in biomedical applications. In this presentation, we review some of the main applications investigated during the past decade. An iterative implementation of the time-reversal process allows tracking gallstones in real time during lithotripsy treatments. In this application domain, a smart exploitation of the reverberations in solid waveguides permits the focusing of high amplitude ultrasonic shock waves with a small number of transducers. Because time reversal is able to correct the strong distortions induced by the skull bone on ultrasonic propagation, this adaptive focusing technique allows brain ultrasonic therapy through the skull bone. Finally, time-reversal focusing guided by speckle noise can be implemented to correct distortion in medical ultrasonic imaging and recent results will be presented.
Nonlinear imaging of isoechogenic phantoms using selective phase conjugation of acoustic harmonics
Authors: Preobrazhensky Vladimir L. , Pernod Philippe , Krutyansky Leonid M.
Published: May 2008

Selective phase conjugation of acoustic harmonics generated by an intense focused probing wave is applied for imaging of isoechogenic phantoms non detectable by the linear echography. The principle of imaging is based on the difference between the nonlinear properties of a phantom and its surrounding medium. As shown by theoretical modelling the analysis of the phase conjugate second harmonic 2ω of the probing wave provides an image contrast comparable with the relative difference between the nonlinear parameters of the phantom and its background. Second harmonic generation by the phase conjugate wave 2ω during its back propagation to the source of the probing wave provides an image contrast at the frequency 4ω even stronger than the difference of nonlinear parameters. These theoretical conclusions are confirmed by the experimental measurements carried out using 10MHz supercritical parametric phase conjugator. The objects were prepared with methanol water solutions of concentrations 20% and 60%. The solutions filling either a cavity in the agar gel or an acoustically transparent container immersed in water represented isoechogenic phantoms with weaker and stronger nonlinearities relatively to water. The contrast values of 2ω-images were measured as -14% and +10% respectively while for 4ω-images the contrast achieved -45% and +37%.
Doppler ultrasonography using wave phase conjugation
Authors: Pyl'Nov Yuri , Smagin Nikolay , Pernod Philippe , Preobrazhensky Vladimir L.
Published: May 2008

Ultrasound wave phase conjugation (WPC) is an efficient tool for velocimetry of flows due to its sensibility to the break of time reversal invariance of acoustic fields in moving media. The presence of flow leads to the non compensated Doppler phase shift of the backward phase conjugate wave relatively to the primary probing wave. This phase shift provides detection, diagnostics and velocimetry of flows and does not require the presence of any scatterers in a flow. Furthermore the phase shift of phase conjugate wave can be used in liquid flowmeters. As it was shown in previous works the sensitivity of liquid flowmeters using phase conjugate ultrasonic waves essentially increases by using nonlinear effects appearing during propagation of phase conjugate waves in a moving liquid. In the present paper we report the theoretical and experimental results on imaging of flow velocity distributions in tubes and phantoms of blood vessel. The scanning auto-confocal system based on parametric ultrasonic wave phase conjugator at 10MHz operation frequency is used in the experiments.The preliminary results of experimental measurements of velocity of vascular blood flow in soft tissues in vitro are discussed.
Time Reversed Elastic Waves within Soft Solids
Authors: Catheline Stefan , Negreira Carlos , Benech Nicolas , Brum Javier
Published: May 2008

When a scalar far-field wave is time reversed from the surface of a cavity, it starts to converge toward its initial point source location, then collapses and finally diverges. Without near field evanescent waves, the symmetric focus spot is limited by the Rayleigh criterion. We present an experimental observation of a time-reversal vectorial wave in the volume of a soft solid. The elastic field is measured using the transient elastography technique. It is observed that the time reversed far field wave collapses and gives birth to near field effects. Numerical computation based on elastodynamic Green's functions in a time-reversal cavity confirms and completes the experimental conclusions: the time symmetry with respect to collapse time is broken and the Rayleigh criterion is direction dependant; the spatial collapse is larger in the direction of the point body force than in the perpendicular direction. The authors anticipate that the method can be used for shear wave beam forming in soft tissues as well as to tissue elasticity assessment.
Investigation of a novel nonlinear detector of weak acoustic signals in noise
Authors: Deeks Julian L. , White Paul R.
Published: May 2008

Recent work has identified and explored a method of detecting weak signals in Gaussian noise, based on the response of a nonlinear system to small input perturbations. The technique is applicable to the detection of weak underwater acoustic signals in unwanted ambient sea noise. Much of the research to date has been carried out using a forced Duffing oscillator as the nonlinear system, with parameters selected so as to place the system at the point of transition from a chaotic state to a stable periodic state. The additive input perturbation, most commonly comprising a simulated single frequency embedded in Gaussian noise with a very low input SNR, has been found to initiate the transition as indicated by the appearance of a stable trajectory in phase space. The attendant increase in amplitude at the output of the detector, at or near to the signal frequency, constitutes a detection of that weak signal. This paper presents a quantitative investigation of the technique as applied to underwater acoustic signals (real and simulated), using receiver operating characteristics (ROC) as a measure of its performance. Both the Duffing system, and a more novel version of the technique using a forced Lorenz system, are investigated.