bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and ultrasonic properties of vanadium tellurite glasses containing cupper oxide
Authors: Abd El-Aal Nadia , Afifi Hisham
Published: May 2008

The elastic properties of vanadium tellurite (65TeO2-(35-x) V2O5- xCuO) glasses with different compositions of cupper (x= 7.5 to 17.5 mol% in steps of 2.5 mol %) have been studied at room temperature (300K). The ultrasonic velocity measurements have been made using a transducer having resonating frequency of 4 MHz (both longitudinal and shear). The density, molar volume, and ultrasonic velocities show an interesting observations, which are used to explore the structural changes in the network. Elastic moduli, Poisson ratio, crosslink density, microhardnes, and Debye temperature of the glasses have been determined using the experimental data. The composition dependence of the elastic properties explores useful information about the physical properties of the vanadium tellurite glasses doped with cupper. Quantitative analysis has been carried out in order to obtain more informations about the structure of the glass under the study, based on bond compression model, and ring deformation model, i.e., the cation-anion bond of each oxide. The observed results through ultrasonic non-destructive evaluation investigate the structural changes and mechanical properties of the glass.
Study of acoustical phonon modes in superlattices with SiGe QDs
Authors: Yaremko Anatoliy , Yukhymchuk Volodymyr , Dzhagan Volodymyr , Valakh Mykhailo
Published: May 2008

Multilayers with SiGe nanoislands (QD's) grown in a broad temperature range are studied using Raman spectroscopy, HRXRD and compared with similar multilayers without islands. As the growth temperature increases, Si content in the islands increases, partially relieving strain. These structural transformations manifest themselves in both the intensity and frequency of the low-frequency Raman peaks. Due to composition- and strain-induced changes in the island band structure, excitation conditions come out of resonance, reducing Raman peak intensity. We have shown that at the interpretation of the Raman scattering by folded acoustic phonons for structures with nanoislands the real morphology of the island layer should be considered. The observed series of the low-frequency Raman peaks, for the multilayered structures with the number of QD layers below ten, is due to the acoustic phonon modes within the islands. The enhancement of the scattering intensity due to resonance of the excitation light with the electronic transitions within the islands plays a significant role. Theoretical analysis was fulfilled in the framework of microscopic approach with using Green function method and taking into account the real structure of QD's and their interaction with surrounding matrix.
Energy pumping in acoustics
Authors: Bellet Romain , Cochelin Bruno , Mattei Pierre-Olivier , Herzog Philippe
Published: May 2008

Energy pumping corresponds to a particular vibratory regime of a non-linear system coupled to a linear primary structure. Its non-linear behaviour allows to reduce vibrations of the primary structure, and is thus a new passive vibration control technique. This phenomenon has mainly been studied in mechanical engineering, so we transposed its principle to noise control in an acoustic medium. The presentation will focus on results about acoustic energy pumping that we observed both experimentally and numerically, in the time and frequency domains. These results highlight two main points: physically, energy pumping corresponds to an irreversible transfer of energy from the primary system to the non-linear absorber, and practically, its effects are a noise level limitation in the acoustic medium in permanent regime and a much faster sound extinction in transient regime.
Shock wave propagation in heterogeneous medium, from ultrasound to sonic boom
Authors: Ganjehi Lili , Coulouvrat François , Thomas Jean-Louis , Marchiano Régis
Published: May 2008

Strong variability of sonic boom due to the atmospheric turbulence is known since the first test flight recordings in the 1960's. To simulate this, a laboratory scale experiment is conducted with ultrasonic shock waves in water at 1 MHz. The experiment is designed for an optimal 1:100,000 scaling with sonic boom. It includes single or multiple heterogeneities of varying sizes but comparable to the acoustical wavelength. Its deterministic aspect allows detailed comparisons with the results of a numerical model based on a nonlinear wide angle parabolic approximation. The experiments show the following features of the shock wave propagation : wavefront folding, local amplification (acoustical lens effect), increase of the rise time, strong variability of the time waveforms. All these features are in qualitative agreement with sonic boom observations. They are observed for a single heterogeneity provided this one is sufficiently large, but are amplified in case of multiple heterogeneities. Comparisons with results of numerical simulations show good agreement in various configurations. Improvements provided by the wide angle approach with respect to the standard parabolic approximation will also be discussed. Preliminary simulations for N wave propagation in a randomly heterogeneous medium will finally be presented.
The analysis of diffraction effects of acoustic waves on the crack's top
Authors: Zhitlukhina Yulia V. , Perov Dmitry V. , Rinkevich Anatoly B.
Published: May 2008

Diffraction effects and features of acoustic wave propagation in elastic media with microcrack were investigated in detail for pulse probing signals. The crack's plane was oriented across the direction of longitudinal ultrasonic wave incidence so that the detection of such a crack with so "inconvenient" spatial location is difficult enough by using traditional acoustic techniques. By using laser interferometer, the set of instantaneous pictures of acoustic field on the specimen's surface, corresponding to different time moments was obtained what allowed investigating and visualizing of acoustic field propagation and diffraction's effects on the crack's top in dynamics. Using various methods of numerical modeling of diffraction processes of acoustic wave on the crack's edge and top for pulse signals the origin of V-like structures on the snapshots of acoustic fields was explained and analyzed.
Ultrasonic and acoustic method for viscoelastic complex media characterization
Authors: Nassar Georges , Lefebvre Fabrice , Skaf Alain , Nongaillard Bertrand
Published: May 2008

In this paper, the potentialities of a low frequency ultrasonic/acoustic technique devoted to the study and characterization of the viscoelastic complex media is investigated. This work shows the limit of the use of ultrasound in a viscoelastic media with a complex matrix. In this context the cheese was indicated as a model of propagation medium, such a product having a very complex matrix in term of texture, openings, crystallization, moisture,... . Theoretical basis of sound attenuation in cheese is recalled, especially the effects of the matrix viscoelasticity and the scattering of ultrasonic energy by holes and cracks. Depending on the degree of openness, ultrasonic velocity or attenuation is chosen to represent the evolution of the cheese. For very high degree of openness, ultrasounds are no longer usable and a tap-test acoustic technique is employed and allows a quality indicator to be constructed. Experimental validations were done with optical images of cut cheeses and rheological measurements. The results indicate that a high degree of sensitivity can be reached with ultrasonic / acoustic non destructive technique.
An ultrasonic anemometer for Mars
Authors: Wilson Colin , Hutchins David , Davis Lee A. , Towner Martin C.
Published: May 2008

Ultrasonic anemometers are often used for studies of 3-D atmospheric turbulence on Earth, due to their robust calibration and fast operation (>10 Hz). The same qualities make ultrasonic anemometry attractive for use on Mars, where similar atmospheric turbulence is found. The low density of Martian atmosphere - a hundredth that of the Earth's - is problematic, because of the large acoustic impedance mismatch between the atmosphere and piezoelectric transducers. One solution to this problem is to use piezoelectric transducers with a hornlike resonator bonded to their front surface. Another solution is to use a capacitive membrane transducer instead. We report on performance of various ultrasonic transducers in carbon dioxide Martian pressures, and present an instrument design capable of meeting the stringent mass, power, and environmental requirements of the European ExoMars lander.
Single bubble oscillations in viscoelastic media
Authors: Strybulevych Anatoliy , Leroy Valentin , Scanlon Martin G. , Page John H.
Published: May 2008

We report a new ultrasonic technique for determining the viscoelasticity of soft materials based on the oscillations of single bubbles injected into the material of interest. It is known that bubbles in a liquid act as strong acoustic scatterers that exhibit a low frequency resonance known as the Minnaert resonance. In the case of viscoelastic media, the complex frequency-dependent shear modulus causes the Minnaert frequency to be shifted to a higher value and leads to additional ultrasonic absorption. Therefore, both storage and loss shear moduli can be determined from the resonance frequency and the damping rate of the acoustic oscillations of a single bubble that has been injected into the sample. Experiments were performed on optically transparent commercial hair gel, agar gel, and PDMS rubber, allowing independent measurements of the bubble sizes to be made by an optical imaging technique. The acoustical properties of the samples were measured by sweeping the frequency of a continuous sinusoidal signal from 4 to 50 kHz. Because the Minnaert frequency is inversely proportional to the radius of the bubble, experiments on bubbles of different sizes enabled the frequency dependence of the complex shear moduli of the materials to be determined.
Acoustic transmission through one plane of bubbles
Authors: Leroy Valentin , Strybulevych Anatoliy , Scanlon Martin G. , Page John H.
Published: May 2008

We measured the transmission of ultrasonic waves through one layer of bubbles, for frequencies ranging from 30 to 250 kHz. The layer was a true 2D structure obtained by injecting very monodisperse bubbles (with radius r=100 μm) into a yield-stress polymer gel. Even for layer with a low concentration of bubbles (areal fraction, nπr2, of 10-20%, where n is the number of bubbles per unit area), the transmission was found to be significantly reduced by the presence of bubbles (-20 to -50 dB) and showed a sharp minimum at a particular frequency. Interestingly, this frequency did not correspond to the individual Minnaert resonance of the bubbles, but depended on the concentration, which we interpret as an indication of strong coupling between the bubbles. We propose a simple model, based on a self-consistent relation, which takes into account the coupling between the bubbles and gives good agreement with the measured transmission.
Nonlinear ultrasonic waves in water-air mixtures
Authors: Vanhille Christian , Campos-Pozuelo Cleofé
Published: May 2008

In this paper we present some features of nonlinear ultrasonic waves in water-air mixtures. This analysis is based on the coupling of the linear wave equation to the bubble equation in a volume formulation. The system is solved via the development of a numerical model (SMOW-BL code). The main restrictions of the model are: the nonlinear behaviour comes exclusively from the bubble vibration, all the bubbles have the same size, air inside the bubbles is adiabatic. Continuous waves at low ultrasonic frequency and wide band pulses propagation in an open domain are analysed. Results obtained by considering several bubbly layers in water are given. The existence of soliton in a water-air mixture is demonstrated. Some results corresponding to standing waves are also presented. A model which allows us to consider the self-generation of air bubbles in water, i.e., cavitation, is proposed.
Photothermal and photoacoustic imaging by ultrafast optical sampling
Authors: Dilhaire Stefan , Rampnoux Jean-Michel , Pernot Gilles , Calbris Gaetan , Grauby Stephane , Rossignol Clément , Ermeneux Sebastien , Mottay Eric
Published: May 2008

We describe a new ultrafast imaging technique based on the use of two new generation Ytterbium lasers emitting at 1030 nm at 50 MHz repletion rate. Ultrafast acquisition is achieved by slightly shifting the repetition rate of the "pump" and the "probe" beams. In that conditions a single shot response is acquired in 1ms that allows sweeping the surface of the device or the material and obtain movies of the reflectivity field of the surface. This technique allows filming the reflectance changes of a material at very high speed typically 1 Tera frame per second during 20ns. We will show applications of this technique in acoustic imaging of surface waves and non destructive evaluation of microelectronic materials.
Experimental evaluation of the wavenumber in stacked screen regenerators
Authors: Ueda Yuki
Published: May 2008

The experimental method to evaluate the wavenumber of the acoustic wave propagating in pores media is proposed. The method was applied to four types of stacks composed of square channels and seven types of regenerators consisting of stacked mesh screens. The experimental results of the stacks agreed well with the theoretical results. The experimentally obtained wavenumber in the stacked screen regenerators were found to be similar to that in circular channels. However, it was found that they depend on the types of regenerators. Based on the dependence on the regenerator types of the evaluated wavenumber, the effective radius in the stacked screen regenerators was addressed.
A thermoacoustic device for sound reproduction
Authors: Kontomichos Fotios , Koutsioubas Alexandros , Mourjopoulos John , Spiliopoulos Nikolaos , Vradis Alexandros
Published: May 2008

Many current research efforts focus on alternative electroacoustic transduction devices having no moving parts, in order to achieve sufficient audio performance from compact solid state devices. Thermoacoustic loudspeakers are transducers based on the conversion of A/C current signals to thermal energy, causing a local fluctuation of air pressure which generates acoustic waves. A thermoacoustic actuator does not involve any movement of solid components in order to generate an acoustic wave and it is based on a mechanism of a "virtual" piston produced by vibrating air molecules via alternating heat transfer to the medium. This work examines such novel and alternative audio transduction technologies based on a novel hybrid thermoacoustic transducer prototype which was developed at the University of Patras through the cooperation between Audio and Acoustic Technology Group and Solid State Physics Laboratory. This hybrid solid state device without moving parts is based on the thermoacoustic method of sound reproduction and preliminary measurements of its performance are presented. The theoretical principles of these systems are also simulated, resulting into comparisons with the measured performance of the prototype.
Numerical modelling of acoustic streaming in resonators
Authors: Boufermel Abdennour , Joly Nicolas , Lotton Pierrick
Published: May 2008

The acoustic wave propagation in thermoviscous fluid can generate slow phenomena, such as streaming and thermoacoustic effects, by nonlinear processes localised mainly in the viscous and thermal boundary layers. The model presented consists in computing numerically by the finite element method, (i) first, the harmonic solution for linear acoustics in thermoviscous fluid including the boundary layers, and (ii) second, the unsteady solution for the acoustic streaming and heat transfer. The model formulation is based on the mass and momentum conservation equations for the streaming, and the energy conservation equation for heat transfer. The streaming is presented as a standard form of an incompressible flow for velocity vector for mass transport, where the nonlinear effects of acoustics are considered as excitation forces for the streaming and sources for heat transfer. As the performance of thermoacoustic devices is limited by the convective heat transfer of the streaming, this study is suited for the optimisation of these systems. Another application is the development of microfluidic devices.
Experimental validations of a new thermoacoustic simulation software CRISTA
Authors: Bétrancourt Adrien , Le Pollès Thierry , Defresne Gérard , Baltean-Carlès Diana , Duthil Patxi , Thermeau Jean-Pierre , François Maurice-Xavier
Published: May 2008

A new simulation software CRISTA has been developed at LIMSI-CNRS. It is based on the Rott's equations approximation. It computes all thermal and acoustic parameters of a given thermoacoustic device whose geometry is previously designed with another program TADESIGN. To realize the simulation, the user needs only to define a drive ratio at some point of the system and the heat exchanger temperatures. Note that for a prime mover the hot heat exchanger temperature is a simulation result. Every converged solution guarantees the physical principles. Moreover, CRISTA allows computing the quality factor of the resonator. The experimental validations have been successfully performed on different devices coupled to the same prime mover: a simple RLC load, an acoustic amplifier, a pulse tube refrigerator and a lumped boost pulse tube refrigerator.
Viscous and thermal effects in acoustic radiation problems
Authors: Inayat Hussian Husnain , Guyader Jean-Louis
Published: May 2008

The thermal and viscous effects are generally neglected in acoustic radiation problems. In the present work we observe if these effects have any significance on acoustic radiation characteristics. Several researches have been materialised in this respect, notably, Bruneau, Beltman et al. These models study factors like inertial and viscous terms for example and then keep some while neglect others based on their significance. Our approach is quite general and we take all the factors into consideration. Our model not only deals with the thermal and viscous effects but compressibility and all other terms are taken into consideration. A system of differential equations issuing from conservation principles is linearized. Next harmonic dependence is assumed and a linear system is obtained. This linear system generates different waves among which only those are kept, which follow the sommerfeld condition. These waves produce an equal number of linear systems, and consequently; pressure, temperature, and the normal and tangential acoustic veocities are determined, using the boundary conditions of no slip, isothermal wall and matching normal acoustic velocity. Our aim is to apply these findings to a viscothermal fluid within a double wall to see if acoustic transmission is improved.
The role of temporal fine structure in speech source segregation
Authors: Bernstein Joshua G. , Grant Kenneth W.
Published: May 2008

Normal-hearing (NH) listeners show better speech recognition when a stationary noise masker is replaced by an opposite-gender competing talker at the same signal-to-noise ratio (SNR). Hearing-impaired (HI) listeners often do not show this interfering-talker benefit (ITB). This may be due to a reduced ability to use temporal fine structure (TFS). Consistent with this idea, NH listeners also show little ITB when TFS is removed. We hypothesized that TFS underlies the ITB by providing source-segregation cues. To test this hypothesis, non-auditory segregation cues were introduced in the form of a video of the talker's face. Speech intelligibility was estimated in NH listeners as a function of SNR for sentences spoken by a female talker and masked by speech-spectrum shaped stationary noise or a single male talker. Target and masker were summed before processing by a 15-channel noise vocoder to remove TFS, and presented with or without accompanying video. Without video, listeners received little ITB, consistent with previous results. Auditory-visual conditions yielded as much as 9 dB of ITB, supporting the hypothesis that a diminished ability to perceptually segregate sources contributes to the lack of ITB in the absence of TFS. Similar results were obtained for unprocessed speech in HI listeners.
Intelligibility of temporal fine structure speech signals with restricted FM excursion
Authors: Gilbert Gaëtan , Leger Agnes , Lorenzi Christian
Published: May 2008

The Hilbert transform is the most common demodulation technique to derive temporal fine structure (TFS) signals. However, for speech stimuli, the Hilbert transform generally leads to results that have no clear physical meaning, generating undesired artefacts; for instance, instantaneous frequency may vary well beyond the analysis filters bandwidth. This study examined the intelligibility in quiet of TFS-coded Vowel-Consonants-Vowel signals generated with a demodulation technique minimizing these artefacts. Speech items were passed through a 16 FIR filters (750th order) filterbank. A Greenwood mapping was used to set filters bandwidth between 80-8020 Hz (approximately 2 ERBs wide). A frequency-modulation function was extracted at the output of each filter, hard limited within the analysis bandwidth and lowpass filtered. Spectral cues were removed by equating the rms across bands. Identification scores ranged between chance level (6.25%) with no improvement across sessions for the least experienced listeners and 50% correct for the most experienced listeners. Further experiments will investigate these between-listeners differences.
Effect of speech rate on speech-on-speech masking
Authors: Chen Jing , Wu Xihong H. , Zou Xuefei F. , Zhang Zhiping P. , Xu Lijuan J. , Wang Mengyuan Y. , Li Liang , Chi Huisheng S.
Published: May 2008

Target speech can be better recognized under speech-on-speech masking conditions if certain differences between target and masker (e.g. in loudness, pitch, location) can be used as cues for streaming. This study examined whether the speech rate can be used by listeners as a cue for unmasking target speech. The rate difference between target and masking speech was manipulated by changing the rate of masking speech using the Synchronized Overlap-Add Fixed Synthesis (SOLAFS) algorithm, and consequently, the ratio of target speech to masking speech (the speech rate ratio, SRR) was quantified. Both target and masker speech were Chinese nonsense sentences and they were co-presented with the signal-to-masker ratio of -7 dB. The results show that speech recognition was significantly increased with the SRR increase from 1 to 1.5 or the SRR decreased from 1 to 0.5. Moreover, the unmasking effect of precedence-induced perceived spatial separation on target-speech recognition was increased monotonically with the increase of the SRR from 0.5 to 1.5. These results suggest that the speech rate is one of the factors influencing both energetic masking and informational masking of Chinese speech. [Supported by the NSFC 60435010; 60535030; 60605016; 30670704]
A computational model of binaural speech intelligibility level difference
Authors: Palomäki Kalle J. , Brown Guy J.
Published: May 2008

This study addresses two questions relating to the binaural intelligibility level difference (BILD). First, we ask whether the BILD is underlain by an equalization-cancellation (EC) mechanism, in which a disparity between the interaural time difference of the target and masker is exploited within each frequency channel, rather than across channels. Second, we consider the effects of three sources of internal noise on the EC mechanism: jitter in neural delays, noise in the equalization process and nonlinearities in the auditory pathway. These issues are investigated using a computational model consisting of peripheral auditory model, binaural processor, auditory scene processor and automatic speech recognition system. The binaural model is based on EC processing, with performance limited by internal noise. The auditory scene processor groups speech harmonics by common F0 and identifies 'glimpses' in which the signal-to-noise ratio is favorable for speech. The performance of human listeners and the computational model are compared on the same speech intelligibility test (Edmonds & Culling, 2005, JASA 117(5), 3069-3078). The BILD of human listeners can be replicated by adjusting parameters that determine the internal noise in the EC model; however, the speech reception threshold of the model is lower than that of human listeners.
Estimating the effective frequency of cochlear implant electrodes using contralateral residual acoustic hearing
Authors: Green Tim , Faulkner Andrew , Rosen Stuart
Published: May 2008

For some cochlear implant (CI) users a contralateral hearing aid provides significantly improved speech perception. Important factors in the bimodal transmission of speech spectral information are likely to include the extent to which the frequency selectivity of residual hearing allows additional place-coded channels, and mismatches between frequency-to-place maps across modalities. When acoustic place coding extends above around 500 Hz an overlap of frequency coverage between acoustic and electric hearing may result in interaural conflicts. However, addressing this issue requires accurate knowledge of CI frequency-to-place maps. Effective characteristic frequencies of CI electrodes have previously been estimated using comparisons of the pitch produced by electrical stimulation with that produced by contralateral acoustic sinusoids In the present work, the acoustic stimuli used for pitch comparisons are either sinusoids or 1/3 octave bands of noise. The latter minimize temporal pitch cues and may reduce differences in perceived quality between electrical and acoustical auditory sensations. Electrical stimuli are high-rate (900 pps or greater) single-electrode pulse trains. Comparisons are performed at different levels spaced over the dynamic range and both paired-comparison and adjustment tasks are used. Results will be discussed in relation to speech processing approaches for optimally combining an implant and contralateral hearing aid.
MEG measures of the auditory steady-state response: Sinusoidal and non-sinusoidal stimuli
Authors: Prendergast Garreth , Johnson Sam R. , Green Gary G.
Published: May 2008

Human sensitivity to amplitude modulation has long been of interest to researchers, both in behavioural and neurological measures. Processing of amplitude modulation is implicated in the process of speech perception and sinusoidal amplitude modulation is used extensively to probe the mechanisms involved in encoding this information. The temporal envelope of speech is more accurately described as bursts of modulation rather than continuous modulation and the current work exposes participants to a continuum of modulation waveforms; from sinusoidal to pulsatile. Waveforms were amplitude modulated at 4 Hz and imposed upon a 500 Hz pure-tone carrier. The waveforms were generated using raised-cosine pulses with different half-durations. Half-durations of 8, 16, 24, 32, 64 and 125 ms were used (125 ms producing sinusoidal amplitude modulation at 4 Hz). Stimuli were 240 seconds in duration and responses were collected on a 248 channel whole-head MEG scanner. The frequency domain steady-state response was analysed from each condition in 14 participants, and results confirmed that the response to sinusoidal amplitude modulation was significantly lower than to modulations more representative of those found in speech signals. This suggests that non-sinusoidal stimuli may be more effective when investigating these auditory mechanisms.
Laboratory synthesis of industrial noise environments with predetermined statistical properties
Authors: Qiu Wei , Davis Bob , Hamernik Roger P.
Published: May 2008

High-level nonGaussion noise is commonly found in a variety of industrial environments. Recent experiments have shown that for a given energy level, the statistical properties of a noise can have a strong effect on the extent of hearing loss produced in exposed individuals. In order to study, in an animal model, the effects on hearing of such noise environments, the statistical properties of the noise as embodied in the kurtosis metric must be under experimental control. For a fixed value of kurtosis and energy level the following four variables will have a strong effect on hearing loss: (1) peak histogram; (2) interval histogram; (3) duration of noise transients; and (4) level of any background Gaussian noise. Simulations have shown that the relations among kurtosis and these variables are nonlinear. However, under certain restricted conditions, these relations may be linear. Accordingly, two strategies for designing controlled industrial noise exposures are presented: (1) the interval-priority model and (2) the duration-priority model. Computer simulations and measurements of actual acoustic environments showed that these two models could be effectively used to simulate a wide variety of realistic industrial noises.
Relationship between a visual stimulus with a feeling of depth and its equivalent sound pressure level (ESPL)
Authors: Hasegawa Hiroshi , Ono Hirotaka , Ito Takumi , Yuyama Ichiro , Kasuga Masao , Ayama Miyoshi
Published: May 2008

This study investigated the equivalent perception between a visual stimulus and its associated sound. Experiments of an auditory-visual stimulus presentation using an audio-video clip of a man beating a drum on a road were performed. The visual stimulus had a feeling of depth with a perspective view of the road. The visual stimulus was projected onto a screen that had the viewing angles of 43.8 deg.(W) * 25.4 deg.(H). Four kinds of distance between the subject and the visual stimulus from 5 to 40 m, seven kinds of the delay time between auditory and visual stimulus from -8 F to 8 F (1 F = 1/30 s), where "+" indicates that the visual event preceded the sound, and nine levels of the sound stimulus from -12 dB to 12 dB of the standard sound pressure level (SPL) were combined and presented. We evaluated the sound pressure level matching with each presentation pattern (equivalent sound pressure level; ESPL). As a result, we obtained that the ESPL tended to decrease when the delay time increased (the sound was delayed). This result shows a possibility that the visual stimulus was a little shifted to the direction of the sound.
Synchrony-asynchrony discrimination of audio-visual signals in auditory streaming
Authors: Kobayashi Maori , Sakamoto Shuichi , Suzuki Yôiti
Published: May 2008

Temporal synchrony is a critical condition for integrating information presented in different sensory modalities. In this study, the effect of tonal organization on synchrony-asynchrony discrimination was examined. The auditory sequences were four repetitions of a triplet pattern comprising a low-frequency tone (L) and a high-frequency tone (H). The frequency difference (ΔF) between L and H was either approximately 1/12, 1/6, 1/3, 1/2, or 1 octave, centered at 1 kHz. Each tone was of 33.2 ms duration including rising and falling raised-cosine ramps of 5 ms. The stimulus onset asynchrony (SOA) of adjacent tones was randomized between 33.2 and 332 ms. The tone sequences were presented diotically via headphones at 65 dB SPL. The visual stimulus was a luminance-modulated Gaussian blob presented on a CRT monitor. The visual stimulus duration was 8.3 ms. Synchrony-asynchrony discrimination thresholds of visual-auditory stimulus onsets were measured using the 2IFC paradigm with a 2-up 1-down method under six ΔF conditions. The results demonstrated that synchrony-asynchrony discrimination improved for audio-visual pulse trains at ΔF between L and H greater than 1/3 octave, suggesting that audio-visual synchrony perception is influenced by the build-up of auditory streaming.
Characterizing lexical interferences in informational masking during speech-in-speech comprehension
Authors: Hoen Michel , Grataloup Claire , Pellegrino François , Collet Lionel , Meunier Fanny
Published: May 2008

Results from our former research on the characterization of informational masking effects occurring during speech-in-speech comprehension showed that phonological and lexical information create specific informational masking effects, depending on the number of speakers involved (Hoen et al., 2007). The goal of the present study was to better characterize purely lexical factors potentially participating into informational masking phenomena. We evaluated speech-in-speech comprehension performances of 40 normal hearing participants listening to isolated lexical items presented together with different speech babble sounds. Lexicality of target items was controlled by using words of variable lexical frequency, high- vs. low-frequency items, as well as pseudowords. The interaction between lexicality of target items and lexicality of words in background noise was controlled by creating babble sounds made of high- or low-frequency words. Results show that, as in silence, lexicality of target items plays a determinant role, high-frequency words being always more intelligible (70%) than low-frequency words (50%), or pseudowords (37%). Conversely, the frequency of lexical items present in the babble had an effect only on the comprehension of pseudowords, the latter being more intelligible in a background of low-frequency items. Together, these results give new precisions on the detailed informational masking effects occurring during speech-in-speech comprehension.
The effect of masker type and word-position on word recall and sentence understanding
Authors: Ezzatian Payam , Li Liang , Pichora-Fuller Kathy , Schneider Bruce
Published: May 2008

Speech understanding is influenced by not only the presence, but also the specific nature of maskers. Noise maskers primarily result in energetic masking, whereas speech maskers create additional interference due to linguistic and acoustic similarities to the target. The present study examined the influence of different types of maskers and target word position on the immediate recall of words in sentences by normal-hearing younger adults. In Experiment 1, nonsense sentences with 3 keywords (e.g., A "house" should "dash" to the "bowl".) were presented against a background of speech-spectrum noise or two-talker nonsense speech. With the speech masker, accuracy increased with word position. With the speech-spectrum noise masker, performance was highest for the first word and did not vary linearly with word position. In Experiment 2, when the speech-masker was noise-vocoded to preserve envelope information while disrupting fine structure cues and minimizing semantic content, performance was similar to that found with the speech-spectrum masker. The results suggest that the ability to track a target sentence in conditions of informational masking improves as the target utterance unfolds over time.
Hearing-screening tests based on filtered sounds and on speech-in-noise intelligibility tests
Authors: Kostek Bozena , Czyzewski Andrzej , Kosikowski Lukasz , Kochanek Krzysztof , Skarzynski Henryk
Published: May 2008

A hearing-screening system dedicated to small-children in pre-schools and primary schools is described in the paper. It uses as a hardware a palmtop computer supplemented with a small sound calibrating device. The described application provides tests that employ automatic questionnaire analysis, audiometric test procedures, and assessment of speech intelligibility in noise. In the speech-in-noise intelligibility tests, pictures are used for young children, and the screening tests are supervised by adults. Apart from the standardized audiometric tests, the screening tests employ environmental sounds filtered in audiometric frequency bands and calibrated as to their levels. When all the testing is completed, the system automatically analyzes the results for each child examined. The decision is made automatically by the expert system taking into account the number of incorrect answers. Children whose hearing impairment is confirmed are referred to treatment in rehabilitation centers. The project presented is a part of the large-scale "I can hear..." screening tests program carried out in Poland for the last few years. This may help to increase awareness and inspire action against noise at a very early age. The methods employed for filtering and calibration environmental sounds and results achieved are presented in the paper.
Learning to read; attaching your ear to your tongue
Authors: Galanter Eugene
Published: May 2008

Really early learning predicts later success in school, life, and society (1), (2). Speech fluency, measured by accuracy, rate, and prosody (3), predicts reading comprehension (4) and reading proficiency (5). Speech fluency may be improved by one-on-one teacher interactions. When properly administered they give teachers useful information, but are time-consuming and subject to teacher's expectations. The results are commonly norm-referenced; a "wait to fail" model where teachers find deficits later in "high-stakes tests" (6). These failures led us to develop "voice mirroring (VM)." (7) V-M lets children self-correct their speech by hearing it mirrored after amplification. The child hears discrepancies between their own speech and their teacher's to self-correct. Children supported by V-M demonstrate better reading skills as estimated by their teachers; (single-blind). Well-spoken children read well
Subjective evaluation of accelerating car interior noise using brain magnetic field
Authors: Takami Kenji , Ishimitsu Shunsuke , Nakagawa Seiji , Asami Toshihiko
Published: May 2008

Recently, the production concept of car engine sound has been changing to the sound design from the cure against noise. Although most work has concentrated on comfortable engine sound, the psychoacoustic effects of time-varying rate of frequency in accelerating engine sound have not been sufficiently studied. Thus we investigated the effects of time-frequency-changing rate in car interior noise on auditory impression using psychological and neurophysiological methods. Harmonic complex tones which simulated accelerating car noise were used as stimuli. Frequencies of the stimuli were time-varying by 15, 25, 35, 50, and 70 Hz/s, like accelerating-engine sounds. First, subjective evaluations were examined using a SD method. Second, neuronal activities of the auditory cortex evoked by these stimuli were measured by magnetoencephalography(MEG). The results indicated that time-varying rate of frequency has significant effects on subjective impression and neuronal activities of the auditory cortex.
Development of pure-tone auditory threshold in school children
Authors: Müller Reinhard
Published: May 2008

The overwhelming majority of publications concerning hearing in children is related to diseases, but normal development of hearing attracts little attention. Normal hearing, as defined by ISO 7029, refers to persons at the age of 18. While aging effects of hearing may be estimated by the use of formulas, children are not included. A field-study at a primary school in Germany showed a notably lower hearing sensitivity for children than for young adults. First graders did not hear well, but auditory performance improved with rising age. For validating this result, the first graders of the field study were again tested 3 years later. The second tests showed the expected improvement of their hearing threshold. So the hearing sense starts not with the full capability but underlies a certain development. Maybe training effects are the key to understanding this topic, as in other human skills.
Human recognition by active and passive acoustic signatures
Authors: Ekimov Alexander , Sabatier James M.
Published: May 2008

Recognition of different sensed objects is a problem that often appears in practice. One of the solutions is based on analysis of the signatures of the specific objects. This method was applied for the acoustic detection of walking humans. Human footsteps excite envelopes of broadband acoustic signals in the air due to periodic friction forces between the foot and the ground/floor. The repetition frequency of these envelopes is equal to the footstep rate and usually lies below 3 Hz. High frequencies in these envelopes allow detection and localization of a walker using a narrowband ultrasonic receiver with a high directivity pattern. Consequently, periodic low frequency human motion results in passive ultrasonic detection using this method. This motion has also unique Doppler signatures and is measured using ultrasonic sonar. Common analyses of passive and Doppler signatures allow the extraction of the specific cadence in human motion and recognition of a human while rejecting other moving or stationary objects. [Work supported by Department of the Army, Army Research Office contract W911NF-04-1-0190].
Active vibration control for the identification-based model of a circular plate
Authors: Leniowska Lucyna , Kos Pawel
Published: May 2008

An active vibration control system is proposed for suppressing the small amplitude vibration of circular plate. An experimental set-up consists of a hard-walled cylinder with a thin metallic plate at one end. Primary excitation is provided by a low frequency loudspeaker installed centrally at the bottom of the cylinder. The vibrations of the plate are measured by the application of strain sensors and accelerometers. Intelligent materials such as 2-layer piezo disk elements are used as the actuators. For the considered system the OE (Output Error) method of discrete-time model identification for real-time active vibration control have been applied. The mathematical model obtained by this method identification is then employed for the linear pole placement controller design. Numerical simulations describing the attenuation effects are presented and discussed.
Modified amplitude and strouhal number scaling for correction of turbulent wall pressure fluctuations
Authors: Galib Thomas
Published: May 2008

Pressure fluctuations were measured in an external turbulent boundary layer over a buoyantly propelled axisymmetric body of revolution. Data were measured for three cases, resulting in axial length Reynolds numbers of 6.88x10 , 4.27x10 , and 3.21x10 at the measurement locations. The fresh water measurements were made in a fully developed turbulent boundary layer, following natural transition, with a near zero (very mildly adverse) pressure gradient. The salt water measurements were made in a favorable pressure gradient following a flow trip to force transition. The momentum thickness Reynolds number was greater than 4400 for all measurements, and the data were scaled with outer variables. The turbulence data were corrected using Corcos correction factors and then further scaled in both amplitude and frequency by the square root of (transducer radius/displacement thickness), in an attempt to resolve spatial resolution effects. This resulted in excellent agreement among the spectra to a modified Strouhal number of 1, which was the range of validity for the data. A second data set (constant freestream velocity and increasing displacement thickness with downstream measurement location), scaled somewhat better with the ratio of transducer radius to displacement thickness.
Fast solutions in FSI-Problems using CMS-Methods
Authors: Guggenberger Johannes
Published: May 2008

Parameter studies in FSI-problems may often become quite time consuming. In most cases the fluid parameters are well defined and only the influence of the parameters of the solid is subject to investigate. Therefore it would be desirable to investigate the fluid and solid part separately and finally combine them using CMS-Methods. This approach would also provide a good physical insight into the individual and combined behaviour of the components fluid and solid. Generally for each interface DOF one constraint mode must be added to the modal base. Since in most problems in FSI the fluid-structure interface involves many DOF the general CMS approach becomes inefficient. To reduce the number of constraint modes it is proposed to use the mode shapes of each component as a load function on the other domain. The static solution provides the modal based constraint modes. Their number corresponds to the number of total component modes which is in most cases much less then in the classic approach. The application is shown in optimization, updating, and monte-carlo-simulation problems.
Training English vowels for French speakers with varying English experience
Authors: Iverson Paul , Preece-Pinet Melanie
Published: May 2008

It is clear that high-variability phonetic training can improve speech perception for adult second-language learners, but it is uncertain what levels of processing are responsible for this change and whether this interacts with the previous experience of the learners. The present study investigated these issues by giving auditory training to French speakers with varying degrees of English experience. Listeners completed 8 sessions of high-variability identification training with clusters of minimal-pair words (e.g., sleet, slit, slight, slate) and a different speaker in each session. The pre/post tests evaluated changes in vowel perception using open-set identification in quiet and noise, a 3-interval category discrimination task, and a task in which individuals mapped their best exemplars for English vowels in a space that included formant movement and duration. The preliminary results suggest that French speakers improved substantially in their identification performance (about 20 percentage points), without having large changes in their ability to discriminate these categories. The results support a view that training improves the process of applying phonetic category knowledge, without changing the underlying categories themselves.
Glottal-opening and airflow pattern during production of voiceless fricatives: a new non-invasive instrumentation
Authors: Honda Kiyoshi , Maeda Shinji
Published: May 2008

In the production of voiceless fricatives, the airflow passing through the vocal tract is controlled by reciprocal open-close patterns of the glottal and oral constriction. In order to observe such coordinated patterns, the authors have developed a combined method using a non-invasive (external-lighting and sensing) photoglottographic (ePGG) technique and a pressure-difference airflow mask. The former technique has the advantage of no restriction of phonetic environments (improvement from the standard PGG) and can be further combined with instrumentation of intraoral air pressure and/or of articulatory movements. Our PGG-airflow data are examined to address a question: It has been known that the glottis opens always wider for word-initial fricatives than for word-medial ones despite no obvious difference in acoustic and physiological requirements. It will be discussed whether the degrees of glottal opening during a fricative co-vary with other aerodynamic and articulatory controls in CVCV utterances with V = nonclose vowels.