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ASA and NAG scholars 2003
ASA scholars
 
  1. Alexei Drozhzhin
    Photo of Alexei Drozhzhin
    Place of Work: Lavrentyev Institute of Hydrodynamics SB RAS.
    Date of Birth: 11.07.1973
    Research Title: Multispark electric discharge in liquid.
    Main Results:
    The research of mechanism of multispark discharge in water was performed. The multispark electrode is a set consisting of any amount of discharge gaps connected parallel to each other. The electrodes in the discharge gaps are situated according to a rod-to-plane type. On each rod there appears a vapor-gas bubble wherein an electric discharge is formed. The discharge plasma does not connect the opposite metal electrodes. The investigating the delay time of bubble breakdown tb was performed. The delay time is the main parameter of a synchronizing the electrodynamic processes taking place on the multispark electrode surface. The results of investigating the dependence of delay time on water conductivity, voltage pulse amplitude, and polarity and area of the rod end of the surface were obtained. According to the experimental results, the formulas allowing us to calculate delay time were obtained. It is found that the delay time of the bubble breakdown on the anode is 5-6 times more than delay time at negative rod polarity.

    The research of the delay time of bubble breakdown forming in the hole of a thin dielectric plate (diaphragm discharge) was carried out. The analysis comparing the obtained results to those for a metal anode and cathode was performed. It is found out that tb of the diaphragm discharge coincides with the delay time of the bubble breakdown on the metal anode within the error of carried out measurements. The results mentioned above were used to explain the mechanism of a thermal water breakdown. On the base of the obtained results a multispark generator of cylindrical pressure waves was constructed. The dependence of the wave pressure amplitude on the distance to the focus of generator was measured. It was indicated that while projecting multispark devices, it was necessary to consider that the forming a group of vapor-gas bubbles reduced the rarefaction wave amplitude in the vicinity of the multispark electrode surface. The photographs of the process of forming a cavitation cluster along the generator focus were taken with the high-speed digital camera. Generator was often used in scientific research, e.g, in the sonoluminescence and cavitation problem investigations.

    Main publications:
    1. V.S. Teslenko, G.N. Sankin, A.P. Drozhzhin, and R.N. Medvedev. Role of cooperativity in sonoluminescence problem investigations.- in: 5-th World Congress on Ultrasonics WCU 2003, September 7-10, 2003, Paris, France, p.116.
    2. G.N. Sankin, A.P. Drozhzhin, K.A. Lomanovich, V.S. Teslenko. A multisite electric-discharge diaphragm generator of shock waves in a liquid.- Instruments and Experimental Techniques, Vol.47, No.4, 2004, p.525-528.
  2. Olga Frolova (Chelibanova)
    Photo of Olga Frolova
    Place of Work: The Department of High Nerve Activity and Psychophysiology, St-Petersburg State University.
    Date of Birth: 24.08.1979
    Research Title: Mother's speech influence on the child's phonologic development during first year of his life.
    Main Results:
    Mother's speech is one of the main parts of child's speech environment. The way for "mutual imitation" was supposed to be the approaching of characteristics of mother's and child's acoustic signals. Eight mother-child pairs take part in our investigation. The registration, analyze of acoustic signals were carried out. It was shown the main frequency of the mother's speech increases and remains on this level from 3 to 6 month of child's life. It was shown that mothers begin to articulate clearly to the 6 month opposite 3 month, now only for vowels: [a] and [e] for worlds with exaggerated melodic contour. The acoustic characteristics of child's signals change and become closer to the parameters of adult's speech from 3 to the 6 month (mother's speech in particular). It is seemed to be more strict in the situation of "speech interaction" (opposite child's signals when mothers was absent). The maximal approaching of the parameters of child's vowel-likes and mother's vowels takes place in the 6 month in the imitational situation. The investigation of acoustic characteristics of vowels and consonants (vowel-likes, consonants- likes) in signals, produced by mothers and children during all first year of the life is planned in future. The goal of such work is the determination of mother's speech's role on the every stage of child's development.
    Main publications:
    1. Grashin P.S., Karabutov A.A., Oraevsky A.A., Pelivanov I.M., Podymova N.B., Savateeva E.V., Solomatin V.S., Spatial distribution of light intensity in high-scattering medium: Monte-Carlo simulations, theoretical analysis and results of opto-acoustical measurements.- Quant. Electronics, 32(10), 868 (2002).
  3. Pavel Grashin
    Photo of Pavel Grashin
    Place of Work: Moscow State University.
    Date of Birth: 21.01.1980
    Research Title: Direct measurement of optical properties of heterogeneous high-scattering media with laser pulsed opto-acoustical method.
    Main Results:
    This work was devoted to solve an important scientific problem of study of the laser radiation propagation in optically turbid media. The pattern of laser fluence rate distribution in turbid tissues and the amount of absorbed energy is very important aspect of any clinical laser treatment of biological objects. For example, it is especially important for procedures such as photodynamic therapy of tumors, laser therapy of pigmented and vascular skin lesions and in over medical applications. Time-resolved laser optoacoustic method was being developed for the measurement of the spatial distribution of laser fluence rate in turbid media and to determine the its optical properties - effective light attenuation and absorption coefficients. This method is based on detection of laser-induced acoustic transients in an investigated medium with high temporal resolution. The effective light attenuation coefficient can be measured by exponential fitting of the front of optoacoustic transient. To determine the light absorption coefficient it is necessary to investigate features of the spatial distribution of laser fluence rate beneath the surface of an irradiated medium. Such investigation was carried out experimentally, with Monte-Carlo simulation and theoretically by solving the light transport equation. It was developed the method of the measurement of optical properties of turbid media in the geometry of the indirect registration of optoacoustic transients at one-sided access to a medium under the investigation. It allows one to make the device being able to measure the light absorption and scattering coefficients of biological tissues in vivo.
    Main publications:
    1. Lyakso E.E., Petrikova N.A., Chelibanova O.V. The features of Russian adults' perception of sounds produced by Russian children of 2 year of life.- Journal of Physiology. 2003, v.4, p.456.
    2. Lyakso E., Gromova A., Frolova O. An acoustic study of words production of Russian children during the third year of life.- "Specom" International workshop "Speech and computer", 2003, Proceedings. M. P.319-326.
    3. Lyakso E.E., Gromova A.D., Frolova O.V., Romanova O.A. Acoustic aspect of child speech development at third year of child's life.- Journal of Physiology, 2004, v.90, N1, p.83-90.
  4. Ilya Makarov
    Photo of Ilya Makarov
    Place of Work: Institute for Information Transmission Problems, RAS.
    Date of Birth: 26.04.1979
    Research Title: 3-dimensional articulatory modeling and area function to transfer function mapping algorithm.
    Main Results:
    A detailed mathematical model of articulation and acoustics which maps any vocal tract shape and any set of articulatory parameters onto the space of speech signal parameters is necessary for the implementation of high-quality articulatory synthesizer. The same model is needed for successful solutions of the speech inverse problems, i.e. determination of the vocal tract shape, articulatory parameters, or area function of the vocal tract from the measured acoustical parameters of speech.

    Present acoustical-articulatory models relied on some assumptions which were impossible to verify experimentally. New measurement techniques (X-ray microbeam system, MRI system, electromagnetic articulograph) make it possible to verify such assumptions and, hence, to specify the acoustical-articulatory models substantially.

    A new algorithm of the vocal tract shape-to-area function conversion was developed as a result of the study conducted under the ASA Grant for 2004. This algorithm is based on the MRI measurements of the axial vocal tract shapes (these measurements were kindly placed in our disposal by the specialists from the Institut de la Communication Parlee, France). It was found that the pharynx can actively change its width during the process of speech production because of the activity of the pharyngeal constrictors. The pharyngeal width change can influence the area function in the pharyngeal section. The pharyngeal width model is proposed as a linear combination of 2 statistically independent principal components which cover about 93% of variance. The pharyngeal width is controlled by varying the factors by these components. The accuracy of the evaluated algorithm was also investigated. The error of the area function approximation by the algorithm is found to be within the error of the MRI measurements in all vocal tract sections. The evaluated algorithm was compared with the best known algorithm of the vocal tract shape-to-area conversion - ab-model. The proposed algorithm gives better accuracy and considerably lesser variance of the area function values almost in all vocal tract sections when compared with the ab-model. The acoustical model of the vocal tract transfer function was also investigated. It was found that the calculation of the resonance frequencies from the MRI-measured cross-sectional areas of vocal tract under the assumption that its walls are absolutely rigid, provides values that noticeably differ from the measured formant frequencies. The compliance of the walls affects the first resonance and almost does not affect the higher-order resonances. The presence of branchings in the tract at the level of the esophageal entrance affects the second and third resonances stronger than the first resonance. The parameters of the wall impedance (loss, mass and elasticity) and the length and cross-sectional area of the branchings are determined by minimizing the rms error between the measured and calculated resonance frequencies. The error in the frequency calculation with allowance for the wall compliance and branching in the vocal tract proves to be within the accuracy of the formant estimation.

    The evaluated algorithms were used in solving the inverse problem for vowels and fricatives and in the articulatory resynthesis of speech signal from the results of the inverse problem solution. The quality of the resynthesized signals was comparable with the quality of the original speech signals.


    Main publications:
    1. A.S.Leonov, I.S.Makarov, V.N.Sorokin, A.I.Tsyplikhine. Articulatory resynthesis of vowels.- Information processes, 2003, Vol.3, No.2, p.73-82.
    2. I.S.Makarov, V.N.Sorokin. Resonances of the branched vocal tract with compliant walls.- Physical Acoustics, 2004, Vol.50, No.3, p.389-396.
    3. A.S.Leonov, I.S.Makarov, V.N.Sorokin, A.I. Tsyplikhine. Articulatory resynthesis of fricatives.- Information processes, 2004, Vol.4, No.2, p.141-159.
    4. P.Baden, I.S.Makarov, V.N.Sorokin. Algorithm of vocal tract cross-sectional area function calculation.- Accepted for publication in: Physical Acoustics, 2004, Vol.50, No.6, p.739-745.
  5. Andrey Radostin
    Photo of Andrey Radostin
    Place of Work: Institute of Applied Physics, RAS.
    Date of Birth: 13.02.1977
    Research Title: Experimental and theoretical investigations of nonlinear acoustic effects in micro-inhomogeneous media.
    Main Results:
    1. The theoretical analysis of nonlinear effects arising at propagation and interaction of elastic waves in media with two main types of hysteretic state equations has been carried out, the main distinctive properties of each media are detected [1,2];
    2. the model of fractured medium hysteretic nonlinearity is proposed, in the frames of this model the processes of propagation and interaction of acoustic waves are analyzed [3];
    3. the nonlinear wave processes in medium with cracks filled with viscous liquid are analyzed [4];
    4. the nonlinear differential equation, describing propagation of elastic waves in microinhomogeneous medium, containing viscoelastic defects with quadratic elastic nonlinearity, is derived, the numeric research of its stationary solution is carried out [5];
    5. an experimental study of the effects of amplitude-dependent internal friction (nonlinear loss, resonance frequency shift, and sound-by-sound damping) in an acoustic bar resonator made of sandstone is carried out, the analytical description of the observed effects is performed within the framework of the microinhomogeneous medium model,. the parameters of the hysteretic and dissipative components of sandstone nonlinearity are obtained from a comparison of the experimental data with analytical dependences describing the nonlinear effects [6].
    Main publications:
    1. Nazarov V.., Radostin .V., Ostrovsky L.A., Soustova I.. Wave processes in media with hysteretic nonlinearity. Part I.- Acoust. Phys., Vol.49, No.3, 2003, p.344.
    2. Nazarov V.., Radostin .V., Ostrovsky L.A., Soustova I.. Wave processes in media with hysteretic nonlinearity. Part II.- Acoust. Phys., Vol.49, No.4, 2003, p.444.
    3. Nazarov V.., Radostin .V. An adhesion mechanism of the hysteresis nonlinearity in fractured media.- Izv. Phys. of the Solid Earth, Vol.39, No.2, 2003, p.170.
    4. Nazarov V.., Radostin .V. Nonlinear wave processes in media with cracks filled with viscous liquid//Acoust. Phys., Vol.49, No.5, 2003, p.565.
    5. V.E.Nazarov and A.V.Radostin. Acoustic Waves in Microinhomogeneous Media with Quadratic Elastic Nonlinearity and Relaxation.- Physics-Doklady, Vol.48, No.11, 2003, p.633.
    6. V.E.Nazarov and A.V.Radostin. Experimental Study of the Effects of Amplitude-Dependent Internal Friction in a Sandstone Bar Resonator.- Acoust. Phys., Vol.50, No.4, 2004, p.446.
  6. Andrey Vedernikov
    Photo of Andrey Vedernikov
    Place of Work: Moscow State University, Physics Faculty, Department of Acoustics.
    Date of Birth: 05.06.1977
    Research Title: Measurement for shear modulus of soft biological tissues using ultrasound.
    Main Results:
    During research where conducted series of experiments. Experiments were aimed to measure shear elastic modulus distribution inside polymer phantoms at various conditions using ultrasound. Elastic characteristics of soft tissues are known to have close correlation with the presence or absence of pathology in tissue. This phenomenon could be assumed as the basis for the process of tissue diagnostics. Shear elastic modulus was computed from the results of shear wave velocity measurements within volume under inspection.

    Shear waves were generated using focused therapy array of transducers due to radiation force of ultrasound. Propagation rate for those waves depends on shear modulus of tissue. Conventional ultrasound imaging scanner operating in M-mode was used to detect and measure the acoustic shear waves. Scanner radiated acoustics pulses and detected the signal reflected by the particles of the medium. For the purpose of increasing the medium reflectivity in process of phantom preparation some amount of reflecting particles was added. RF-signals stored on the PC were then processed using cross correlation technique for the displacement estimation. Having the data on the displacements inside the phantom, shear wave velocity was calculated. Shear elastic modulus value, computed from measured shear wave velocity shows good correspondence with value computed from static elasticity measurements.

    Also there were made experiments on measurement of shear modulus distribution inside inhomogeneous phantoms. During phantom preparation were made hard and soft layers, which could be clearly separated when shear wave speed was measured inside those layers. Another kind of inhomogeneity was thermally induced by a grid wires when electric current was passed through it and by heating phantom with ultrasound beam. The higher the temperature the lower the shear modulus of a polymer, it's melting point is about 120 C. While heating the sample by electric wires shear wave passed through the heated region with lower shear modulus and time of pass was growing with temperature of heating. Changes in time of shear wave travelling through inhomogeneity were measured in time at different temperatures of heating. Those changes are in good correspondence with theoretically calculated travel time for the shear wave through the shear modulus thermal inhomogeneity induced by electric current. Thermal inhomogeneity was also induced by heating phantom with ultrasound beam, which was then used for shear wave generation. Increasing of a shear wave peak amplitude and growth of shear pulse duration was observed.

    Main publications:
    1. V.G.Andreev, A. V.Vedernikov. "Shear waves excitation in an ultrasonically heated tissue". 3rd International Symposium on Therapeutic Ultrasound, Lyon, France, 22-25 June, 2003, Conference Proceedings. p.163-168.
    2. A.V.Vedernikov, V.G.Andreev Generation of the shear waves by focused ultrasonic beam: account of thermal effects. XIII Session of the Russian Acoustical Society, Moscow, August 2003, Conference Proceedings, vol.3, p.184 - 187.
NAG scholars
  1. Andrey Morozov
    Photo of Andrey Morozov
    Place of Work: Moscow State University, Physics Faculty.
    Date of Birth: 19.04.1979
    Research Title: Piezoelectric transducer surface vibration characterization using acoustic holography and laser vibrometry.
    Main Results:
    The surface of a piezoelectric transducer vibrates nonuniformly, due to transducer structure (e.g. phased arrays) or due to excitation of Lamb waves at their surface. The knowledge of surface vibration character can be used for precise prediction of radiated acoustic fields and for creation of transducers with predefined properties. However, up to now there are no reliable direct methods of surface vibration measurement in liquids.

    In our works the new acoustic holography method for study of piezoelectric transducer surface vibrations was developed. The method includes a measurement of wave amplitude and phase in many points of a plane grid in front of the source, numerical time reversal of a wavefront, and back propagation of the field to the source using the Rayleigh integral.

    The method of acoustic holography was experimentally used for study of many acoustic sources of different forms, sizes and frequencies, including piezocomposite transducers and medical ultrasonic scanners. It was shown that the method allows reconstruction of the source vibrations with high precision and spatial resolution. The technique was successfully used to reveal the character of surface damages of broken or overheated transducers. The reconstructed velocity distribution over transducer surface was also used to predict the radiated acoustic pressure in space. It was showh that our method gives much more precise results than the prediction based on assumption of uniform vibrations, which is frequently used.

    In addition to the holographic approach, vibrations of piezoelectric transducers were studied directly using laser vibrometer. A special experimental and theoretical study was performed, and it was shown that this well-developed method gives wrong results when measurements are performed in liquid, because of strong acousto-optic interaction in a condensed media. It was shown that although the acoustic holographic approach has limited spatial resolution (of order of a wavelength), it allows fairly exact prediction of the radiated field structure.

    The experimental technique of measurements with laser vibrometer was expanded to record all the time-dependent waveform in every point of a transducer. The time-domain transducer surface vibrations and the processes of Lamb waves generation and propagation were investigated in impulse and continuous regimes.

    Main publications:
    1. O.A.Sapozhnikov, Yu.A.Pishchalnikov, A.V.Morozov. Reconstruction of the normal velocity distribution on the surface of an ultrasonic transducer from the acoustic pressure measured on a reference surface.- Acoustical Physics, 2003, Vol.49, No.3, pp.354-360.
    2. A.V.Morozov, Yu.A.Pishalnikov, O.A.Sapozhnikov. Method of measurement of vibrational velocity on ultrasound source surface: numeric analysis of accuracy.- Physics of Vibrations, 2002, Vol.10, No.2, pp.93-99.
  2. Natalya Petrikova
    Photo of Natalya Petrikova
    Place of Work: Saint-Petersburg State University.
    Date of Birth: 13.04.1979
    Research Title: Fine motor and "speech" development of the first year Russian native children.
    Main Results:
    Psychological investigators have asserted the presence of quality relationship between a child fine motor and speech development on early ontogenesis stages. However quantity date are not in plenty.

    A video analysis of 5 healthy home children was executed by the computer program Observer, (this program was kindly placed in our disposal by the specialists from the Pavlov State Medical University of Saint Petersburg, the pharmacology laboratory)).

    There were recognized: a time of beginning and end of manipulations, a time of beginning and a type of vocalizations (in vowel-like categories by Russian alphabet) to study an influence of manipulations on spontaneous vocalizations of the first year children.

    An average sum time of manipulation and average quantity vocalizations were measured in every age. It is shown, than an envelope, which shown a dynamic of average sum time of manipulation during the first year each child has inversely form as a envelope which shown a dynamic a average quantity vocalizations. Thus, the child in definite time has the longer manipulation time, the less quantity vocalizations. Besides, a comparison of vocalization number, accompanying of manipulation, and an amount implementation of this acquirement on each child in each month permit to suggest the presence of contrary influence of manipulation on vocalization compresence.

    It is shown, average vocalization amount, which accompanying of manipulations considerably less than vocalization quantity that accompanying the other movement during the first year of children. It is discerned, that the most frequent vowel-likes in the first year of child life are [a] and [e]-like, only these sounds were realized during manipulation in each period. However, the sound repertoire accompanying of the other movements was too much various in each time. It is shown up, vowel-likes, accompanying of a manipulation, are characterized by its higher fundamental frequency and otherwise interrelationship between F1 and F2 than adult vowels, and they occupy more extensive field on two-formant plane.

    Probabilities of vocalization forthcoming were worked regarding the time of beginning, end and during manipulation out. It was recognized, the probability of vocalization during manipulation was anear peer or less than the probability of vocalization forthcoming before the beginning or the end of vocalizations.

    In sum the above permit to infer that during the first year manipulation affects spontaneous vocal production to depress it. But because of we have not had aplenty of accompanying vocalization it seems essential to increase a child amount.

    Main publications:
    1. Lyakso .., Chelibanova .V., Petrikova N.., Galunov V.I The early language development of Russian children.- International journal of psychophysiology, 2002, V.45, p.113.
    2. Galunov V.I., Lyakso .E., Chelibanova .V., Petrikova N.. The acoustical aspect of vocal speech communication during the early childhood.- Speech and computer, SPb, Russia, 2002, p.75-82.
    3. Lyakso .., Petrikova N.., Chelibanova .V. Characteristics of an apperception of the second year children sounds by Russian native auditors.- Setchenov's Russian physiological journal, 2003, v.89, N4, pp.456-472.