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  • 1. Akiyama, Masahiko
    et al.
    Kamakura, Tomoo
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Parametric sound fields by phase-cancellation excitation of primary waves.2008Conference paper (Refereed)
    Abstract [en]

    By radiating bifrequency primary waves from two ultrasonic emitters with changing the phases of the primary waves, we can obtain the sound fields that are different from the usual in‐phase excitation. Especially, for the excitation of out‐phase by 180 degrees the difference frequency wave has the directivity of almost uniformity near the acoustic axis. Additionally, the sound pressure levels of the harmonic components of the difference frequency and the primary waves as well are suppressed by 10 dB and more

  • 2. Andersson, Sara
    et al.
    Haller, Kristian
    Hellbratt, Sven-Erik
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Damage monitoring of ship FRP during exposure to explosion impacts2011Conference paper (Refereed)
    Abstract [en]

    Fiber Reinforced Plastics (FRP) has been used by Kockums' shipyard in the manufacturing of ships over 35 years, during which time is has been proven to be durable and practical. The light weight makes it a more and more attractive material as energy and material expenditure decreases are required. A special application is the Composite Superstructure Concept [1] where composite materials are added on top of a steel hull, which decreases the weight and running costs considerably, and makes it possible to even add extra levels while keeping the same center of gravity. If efficient condition monitoring systems can keep track of emerging damages of the structure, the weight may be even more reduced and the interval between maintenance inspections may be prolonged. As important steps in this process, a ship mock-up section was subjected to increased levels of explosive underwater impacts, and the damage progression in the hull was monitored by a nonlinear acoustic technique.

  • 3. Demin, I.Yu.
    et al.
    Pronchatov-Rubtsov, N.V.
    Rudenko, Oleg
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Gurbatov, S.N.
    Krainov, A.
    The numerical simulation of propagation of intensive acoustic noise2013Conference paper (Refereed)
    Abstract [en]

    The propagation of intensive acoustic noise is of fundamental interest in nonlinear acoustics. Some of the simplest models describing such phenomena are generalized Burgers’ equations for finite amplitude sound waves. An important problem in this field is to find the wave’s behavior far from the emitting source for stochastic initial waveforms. The method of numerical solution of generalized Burgers equation proposed is step-by-step calculation supported on using Fast Fourier Transform of the considered signal. The general idea is to keep only Fourier image of concerned signal and update it recursively (in space). For simulating the wave evolution we used 4096 (212) point realizations and took averaging over 1000 realizations. Also the object of the present study is a numerical analysis of the spectral and bispectral functions of the intense random signals propagating in nondispersive nonlinear media. The possibility of recovering the input spectrum from the measured spectrum and bispectrum at the output of the nonlinear medium is discusses. The analytical estimations are supported by numerical simulation. For two different types of primary spectrum evolution of jet noise were numerically simulates at a short distance and assayed bispectrum and a spectrum analysis of the signals.

  • 4. Dvoesherstov, M.Yu.
    et al.
    Cherednik, V.I.
    Bosov, S.I.
    Orlov, I.Ya.
    Rudenko, Oleg
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Numerical and experimental analysis of the parameters of an electroacoustic thin-film microwave resonator2013In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 59, no 5, p. 513-520Article in journal (Refereed)
    Abstract [en]

    The results of numerical and experimental analysis of the parameters of a singlefrequency micro wave thinfilm electroacoustic resonator based on an (0001)AlN piezofilm with an acoustic reflector operat ing at a frequency of 10 GHz are presented. The effect of the reflector design on the resonator characteristics is considered. Using the modified Butterworth–Van Dyke model, it was shown that the ohmic resistance of electrodes and entrance paths substantially decreases the Qfactor at the resonance frequency of series and the acoustic losses in the resonator deteriorate the Qfactor at the parallel resonance frequency

  • 5. Enflo, Bengt
    et al.
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    On the evolution of a spherical short pulse in nonlinear acoustics2012Conference paper (Refereed)
    Abstract [en]

    Planar wave propagation in nonlinear acoustics is modeled by the Burgers equation, which is exactly soluble. Spherical wave propagation is modeled by a generalized Burgers equation, in which the dissipative parameter of the plane wave Burgers equation is replaced by an exponentially growing function of the variable symbolizing the travelled length of the wave. A procedure previously used in 1998 by B.O. Enflo [1] on cylindrical short pulses is now used on spherical short pulses, which are originally N-waves. The procedure consists of the four steps: 1) A shock solution of the generalized Burgers equation is found by asymptotic matching. The shock fades in the region where the nonlinear term in the equation can be neglected. 2) The linear equation in step 1) is rescaled. It is identically solved by an integral representation containing an unknown function. 3) The integral representation found in step 2) is evaluated by the steepest descent method in the fading shock region introduced in step 1). The unknown function introduced in step 2) is determined by comparing the result of this evaluation with the fading shock solution found in step 1). 4) The integral representation with the unknown function determined is evaluated approximately asymptotically for large values of the original length (or time) variables in the original generalized Burgers equation (old-age regime). The result of this procedure is an old-age solution, controlled by numerical calculations. Curves of analytical and numerical solutions are given

  • 6.
    Fei, Shenyang
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Development of a general acoustic model for an arbitrary surveillance camera design2018Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis studies how the mechanical design of a surveillance camera affects the acoustic performance, mainly in terms of the frequency response within the human hearing range. During the project, the mechanical characteristics that affect frequency response were investigated by measuring the camera’s audio behavior in an anechoic chamber. A theoretical and adaptable acoustic model was built in COMSOL to simulate the frequency response of the sound path. Measurement and simulation results were compared to identify critical aspects of the mechanical design and adjust accordingly for better acoustic performance.

  • 7.
    Gurbatov, S. N.
    et al.
    NI Lobachevsky State Univ Nizhny Novgorod, Nizhnii Novgorod, Russia..
    Rudenko, Oleg
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering. NI Lobachevsky State Univ Nizhny Novgorod, Nizhnii Novgorod, Russia.;Moscow MV Lomonosov State Univ, Moscow, Russia.;AM Prokhorov Inst Gen Phys, Moscow, Russia.;Russian Acad Sci, OYu Shmidt Inst Terr Phys, Moscow, Russia.;Blekinge Inst Technol, Karlskrona, Sweden..
    On the Inverse Problems of Nonlinear Acoustics and Acoustic Turbulence2015In: Radiophysics and Quantum Electronics, ISSN 0033-8443, E-ISSN 1573-9120, Vol. 58, no 7, p. 463-476Article in journal (Refereed)
    Abstract [en]

    We consider the problem of retrieval of the radiated acoustic signal parameters from the measured wave field in some cross section of the nonlinear medium. The possibilities of solving regular and statistical inverse problems are discussed on the basis of the solution of the Burgers equation for zero and infinitesimal viscosities.

  • 8. Gusev, V.A.
    et al.
    Rudenko, Oleg
    The Field of Radiative Forces and the Acoustic Streaming in a Liquid Layer on a Solid Half-Space2010In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 56, no 6, p. 861-870Article in journal (Refereed)
    Abstract [en]

    The acoustic field and the field of radiative forces that are formed in a liquid layer on a solid substrate are calculated for the case of wave propagation along the interface. The calculations take into account the effects produced by surface tension, viscous stresses at the boundary, and attenuation in the liquid volume on the field characteristics. The dispersion equations and the velocities of wave propagation are determined. The radiative forces acting on a liquid volume element in a standing wave are calculated. The structure of streaming is studied. The effect of streaming on small size particles is considered, and the possibilities of ordered structure formation from them are discussed.

  • 9. Haller, Kristian
    Acoustical Measurements of Material Nonlinearity and Nonequilibrium Recovery2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A damaged material or a material with non perfect atomic geometry, dislocations or cracks, exhibits two types of characteristic responses to acoustic excitations. First is the fast nonlinear dynamics response that is present as long as the material is excited. As soon as the excitation stops the response disappear. Second is the Slow Dynamics, which detects alterations of the material properties. The properties are affected by, for example, a mechanical pulse, changes in temperature, pressure or humidity. When the cause of alteration stops the material is recovering towards its equilibrium state. This recovering can exist over a long period of time, much longer than the vibration from a mechanical pulse. The techniques used here, both the fast and Slow Dynamics, have been used for NonDestructive Testing to detect damage in objects. All of them are suitable for this purpose, but for different material and geometry different techniques can be advantageous. They offer the possibility to use relatively low frequencies which is advantageous because attenuation and diffraction effects are smaller for low frequencies. Therefore large and multi-layered complete objects can be investigated. Sometimes the position of the damage is required, but it is in general difficult to limit the geometrical extent of low-frequency acoustic waves. A technique is presented that constrains the wave field to a localized trapped mode so that damage can be located. The existence of trapped modes is shown using an open resonator concept and the localization is shown to be successful. The problem with intermittent and changing amplitudes, even when very small, is that the material is really never at equilibrium, or even at steady state. The measurement signal influences the outcome. The material is affected by its strain history and its constantly changing state, the fast and Slow Dynamics are hard to separate. A measurement technique keeping the internal strain constant has been used to minimize the influence of Slow Dynamics allowing observations of only nonlinearity. The influence of temperature is also studied with this technique.

  • 10. Haller, Kristian
    et al.
    Hedberg, Claes
    Constant Strain Frequency Sweep Measurements on Granite Rock2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 100, no 6Article in journal (Refereed)
    Abstract [en]

    Like many materials, granite exhibits both nonlinear acoustic distortion and slow nonequilibrium dynamics. Measurements to date have shown a response from both phenomena simultaneously, thus crosscontaminating the results. In this Letter, constant strain frequency sweep measurements eliminate the slow dynamics and, for the first time, permit evaluation of nonlinearity by itself characterized by lower resonance frequencies and a steeper slope. Measurements such as these are necessary for the fundamental understanding of material dynamics, and for the creation and validation of descriptive models.

  • 11. Haller, Kristian
    et al.
    Hedberg, Claes
    Rudenko, Oleg
    Slow variations of mechanical and electrical properties of dielectrics and nonlinear phenomena at ultrasonic irradiation2010In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 56, no 5, p. 660-664Article in journal (Refereed)
    Abstract [en]

    The interconnection between variations of elasticity and dielectric permittivity of mesoscopic solid systems under exposure to ultrasound is experimentally observed. A phenomenological theory generalizing Debye’s approach for polar fluids is developed to explain the measured data. The substitution of acoustic measurements by dielectric ones not only simplifies the procedure, but offers new possibilities to remotely evaluate the mechanical properties of materials and natural media.

  • 12.
    Hedberg, Claes
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Andersson, Sara
    Haller, Kristian
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Deflection dynamics of rock beam caused by ultrasound2013In: Mechanics of time-dependant materials, ISSN 1385-2000, E-ISSN 1573-2738, Vol. 17, no 4, p. 597-604Article in journal (Refereed)
    Abstract [en]

    A new method for monitoring the time dependent dynamics of materials is proposed and implemented. By completely separating the conditioning (here ultrasound), the probing (here gravity), and the material state indicator (here deflection), the details of this dynamic process becomes apparent. The method allows both continuous monitoring of the material state without cross-interaction by the measuring process on the results, as well as complete freedom of conditioning and probing. It was successfully tested for sensitivity and repeatability when applied on a horizontally suspended beam of gabbro rock, which was observed to sag when subjected to ultrasound. These introductory tests have given new insights. The beam rises back, against the force of gravity, after the ultrasound is turned off. The deflection motions are fast both at the onset and at the termination of ultrasound, with the subsequent continuations being much slower. This new method is able to provide the higher accuracy needed for the advancement of the theoretical framework for material property time dependent dynamics.

  • 13.
    Hedberg, Claes
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Andersson, Sara
    Haller, Kristian
    Hallbratt, Sven-Erik
    Non-contact nonlinear ultrasound scan of a CFRP plate with manufactured damages2013Conference paper (Refereed)
    Abstract [en]

    A Carbon Fibre Reinforced Plastic plate was manufactured to have internal damages of different types. A nonlinear ultrasound technique was used to scan the plate. Non-contact transmitters of own design were used as transducer, and a contact sensor was used to measure the wave in the composite. Scanning was made perpendicularly with the sensor being on the same side as the transducer. The technique can be adapted in accuracy and speed.

  • 14.
    Hedberg, Claes
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Haller, Kristian
    Method for Monitoring Slow Dynamics Recovery2012In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 58, no 3, p. 713-717Article in journal (Refereed)
    Abstract [en]

    Slow Dynamics is a specific material property, which for example is connected to the degree of damage. It is therefore of importance to be able to attain proper measurements of it. Usually it has been monitored by acoustic resonance methods which have very high sensitivity as such. However, because the acoustic wave is acting both as conditioner and as probe, the measurement is affecting the result which leads to a mixing of the fast nonlinear response to the excitation and the slow dynamics material recovery. In this article a method is introduced which, for the first time, removes the fast dynamics from the process and allows the behavior of the slow dynamics to be monitored by itself. The new method has the ability to measure at the shortest possible recovery times, and at very small conditioning strains. For the lowest strains the sound speed increases with strain, while at higher strains a linear decreasing dependence is observed. This is the first method and test that has been able to monitor the true material state recovery process.

  • 15. Hedberg, Claes
    et al.
    Haller, Kristian
    Non-contact nonlinear acoustic damage localization in plates. Part 2: Localized resonance through dynamically trapped modes2008In: Acta Acustica united with Acustica , ISSN 1610-1928 , Vol. 94, no 1, p. 48-53Article in journal (Refereed)
    Abstract [en]

    This work is the second part of three that presents new tools to be used for damage localization in plates by nonlinear acoustical methods. It introduces an important in-plane localization technique, which is based on the existence of resonant spatially localized wave fields. The wave from the transducer is acting as a dynamic influence on the plate surface, making the waves reflect in a non-ideal way. The non-ideal reflections make the modes underneath the transducer have different resonant frequencies than the modes beside the insonified area. They appear both for contact and non-contact sources. In the nonlinear damage localization application, the trapped mode wave field interacts with another signal at lower frequency. This results in sidebands around the high frequency whose amplitudes are related to the amount of damage underneath the transducer.

  • 16. Hedberg, Claes
    et al.
    Haller, Kristian
    Kamakura, Tomoo
    A Self-Silenced Sound Beam2010In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 56, no 5, p. 637-639Article in journal (Refereed)
    Abstract [en]

    Parametric loudspeakers are transmitting two high power ultrasound frequencies. During propagation through the air, nonlinear interaction creates a narrow sound beam at the difference frequency, similar to a light beam from a torch. In this work is added the physical phenomenon of propagation cancellation, leaving a limited region within which the sound can be heard—a 1 meter long cylinder with diameter 8 cm. It is equivalent to a torch which would only illuminate objects within 1 meter. The concept is demonstrated both in simulation and in experiment.

  • 17.
    Hedberg, Claes
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Johnson, Erland
    Andersson, Sara
    Haller, Kristian
    Kjell, Gunnar
    Hellbratt, Sven-Erik
    Ultrasonic monitoring of a fiber reinforced plastic: steel composite beam during fatigue2012Conference paper (Refereed)
    Abstract [en]

    The use of composite superstructures on current or newly built steel hulls is a recently emerged technology. The economic estimations predict that the extra costs for putting composite superstructures, with the present safety margins, on steel ships will be paid back in only 2-3 years. This also makes the ships having smaller ecological footprints with less fuel consumption and CO2 emissions. In this stage of development it is needed to ensure the durability of the joints between the steel and glass fiber reinforced plastic. The first step is that the joints must first be proven to withstand fatigue. In this test a 4-meter beam, which represents the joint, were investigated for fatigue progression by a four-point-bending fatigue test. In order to show that ultrasonic material monitoring techniques can be used to monitor the damage progression, the beam was measured during the tests until failure. The test was successful both in showing that the joint could withstand high levels of mechanical exposure, and in that the ultrasonic techniques accompanied the damage progression which means that they may be used on vessels during operation

  • 18. Hedberg, Claes
    et al.
    Rudenko, Oleg
    Dissipative and hysteresis loops as images of irreversible processes in nonlinear acoustic fields2011In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 110, no 5Article in journal (Refereed)
    Abstract [en]

    Irreversible processes taking place during nonlinear acoustic wave propagation are considered using a representation by loops in a thermodynamic parameter space. For viscous and heat conducting media, the loops are constructed for quasi-harmonic and sawtooth waves and the descriptive equations are formulated. The linear and nonlinear absorptions are compared. For relaxing media, the processes are frequency-dependent. The loops broadens, narrows, and bends. The linear and nonlinear relaxation losses of wave energy are shown. Residual stresses and irreversible strains appear for hysteretic media, and here, a generalization of Rayleigh loops is pictured which takes into account the nonlinearly frequency-dependent hereditary properties. These describe the dynamic behavior, for which new equations are derived.

  • 19.
    Håkansson, Lars
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    The Fourier Transform in Sound and Vibration2015In: International Journal of Acoustics and Vibration, ISSN 1027-5851, ISSN 1027-5851, Vol. 20, no 4, p. 190-190Article in journal (Refereed)
  • 20.
    Ikonen, Linus
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Nilsson, Daniel
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Quality assessment of mineral wool insulation plates: Using ultrasonic non-destructive testing2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the manufacturing process of mineral wool insulation plates, defects arise, such as unmelted base minerals and uncured binder which gets embedded within the plates. To be able to sort out these defective plates from a manufacturing line, a reliable quality assessment is needed. The aim is to find an ultrasonic non-destructive testing method that can identify the embedded defects. This was achieved through experiments on defective insulation plates using three different ultrasonic non-destructive testing methods that were of interest. These methods were higher harmonics, pulse-echo and through transmission. Of these three, the through transmission method showed the most promising results in finding the defects that were sought after. The through transmission method utilizes two aligned transducers, one acting as a transmitter and one as a receiver. When the defective area passes through the sound beam between the transducers the intensity of the beam drops, indicating that a defect is present. The weakened intensity is due to the signal attenuation, mainly caused by the higher density of the defects compared to the base material in the surrounding insulation plate. The method is well suited for being implemented in a production line since it’s a fast method and, therefore, suited for moving objects. More measurements are needed to establish a reliable reference value to consistently distinguish the defects from the surrounding plate. The method was only evaluated in a small scale experimental environment so further experiments on a larger scale are needed to mimic and evaluate the reliability in the real case scenario of the production lines.

  • 21. Kao-Walter, Sharon
    et al.
    Levin, M.L.
    Petronyuk, J.S.
    Walter, Mats
    Acoustic imaging internal microstructure of a packaging material2008Conference paper (Refereed)
    Abstract [en]

    Microstructure of a paper-based packaging material was studied by acoustic microscopy method. The laminate structure of the packaging material contains paperboard, polymer and aluminium, which are widely used for aseptic liquid food package. The method has also been used to detect delaminations inside the material. The results show the possibility to study the micro structural features of paperboard, polymer and aluminium foil layered materials by applying the high-resolution ultrasonic acoustic microscopy. The potential for visualization defects in the body of this kind of materials is discussed in order to further develop the Non-Destructive Testing (NDT) method in food packaging industries.

  • 22.
    khan, Imran
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Muthusamy, Dineshkumar
    Ahmad, Waqas
    Gustavsson, Ingvar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Zackrisson, Johan
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Nilsson, Kristian
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Remotely Controlled Laboratory Setup for Active Noise Control and Acoustic Experiments2012Conference paper (Refereed)
    Abstract [en]

    This paper presents a remotely controlled educational experiments setup for Active Noise Control (ANC) and acoustic experiments. The experiments setup is based on the Virtual Instruments Systems in Reality (VISIR) open source platform, National Instruments LabVIEW software and a Digital Signal Processor TMS320C6713 from Texas Instruments. The software development and equipment are controlled remotely form a client PC using a standard web browser. The proposed laboratory setup focuses on ANC experiments applied to noise in a ventilation duct. The laboratory setup will enable students to test and investigate properties and behaviour of adaptive algorithms in reality as compared to more confined simulations usually carried out in Matlab etc. The general steps in ANC, such as the feasibility of active control, designing, testing and debugging ANC algorithms, configuration and implementation of an active control system, are all covered. In addition students will be able to study the effect of analog to digital converters (ADC), anti-aliasing filters, digital to analog converters (DAC) and reconstruction filters using digital signal processing in reality, etc. The laboratory setup is suitable for a wide range of courses such as sound related experiments in upper secondary school physics, digital signal processing, adaptive signal processing, and acoustics at university level.

  • 23.
    khan, Imran
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Muthusamy, Dineshkumar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Ahmad, Waqas
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Gustavsson, Ingvar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Zackrisson, Johan
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Nilsson, Kristian
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Johansson, Sven
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Remotely Controlled Active Noise Control Laboratories2012Conference paper (Refereed)
    Abstract [en]

    Remotely controlled laboratories in educational institutions are gaining popularity at an exponential rate due to the multidimensional benefits they provide. The Virtual Instrument Systems in Reality (VISIR) project by Blekinge Institute of Technology (BTH) Sweden has successfully implemented remotely controlled laboratories, with remotely controlled real instruments and experimental setups. Currently these laboratories provide students the opportunity to conduct experiments in the field of electronics, antenna theory and mechanical vibration measurements. In this paper a prototype system of a remotely controlled laboratory for active noise control (ANC) is introduced. The proposed lab will focus on addressing the problem of a ventilation duct noise. The laboratory is informative and to a great extent introduces a student to the general steps in ANC when it is suggested as a plausible solution for a noise problem. The student can perform an investigation concerning feasibility of active control, design, configuration and implementation of an active control system. The laboratory is based on a modern and relevant DSP platform with the corresponding software development environment controlled remotely. In addition, it may be utilized remotely both for lab assignments in acoustics courses and digital signal processing courses.

  • 24. Lebedev-Stepanov, P. V.
    et al.
    Rudenko, Oleg
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Acoustic microfluidics: Capillary waves and vortex flows in the cylindrical volume of a fluid drop2015In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 61, no 2, p. 173-177Article in journal (Refereed)
    Abstract [en]

    We calculate the field of radiation forces in a cylindrical fluid layer on a solid substrate formed as a result of the action on a fluid of a capillary wave propagating from the axis along a free surface. We study the structure of acoustic flows excited by the radiation forces. We discuss the action of flows on small-sized particles and the possibilities of these particles to form ordered structures. © 2015, Pleiades Publishing, Ltd.

  • 25. Lebedev-Stepanov, P.V.
    et al.
    Rudenko, Oleg
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Acoustic Flows in a Fluid Layer on a Vibrating Substrate2013In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 59, no 6, p. 640-643Article in journal (Refereed)
    Abstract [en]

    The field of radiation forces in a fluid layer on a solid substrate is calculated. This field is formed during propagation of surface capillary wave along a free surface. The wave is excited by substrate vibrations as a result of instability development. The structure of acoustic flows is studied. Their effect on small size particles and the possibilities of generating ordered structures from these particles are discussed.

  • 26.
    Murki, Sai Rohith
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Puttagunta, Yaswanth
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    CFD Simulation of an Activated Carbon Filter2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In various industries, specialized filters with activated carbon are used for adsorbing mercury from air-flows. MRT has eight such Activated CarbonFilters (ACFs) in one of their devices. The main purpose of research is tostudy the flow in the ACF filter and suggest a mathematical model for the complete system through which an improved design can be found.Simulation of a single ACF illustrates how the current system’s air flow does not cover the whole filter leaving part of the carbon bed unused forthe adsorption. This is validated by experimental data. A theoretical studybased on a mathematical model is made and the improved air flow pattern of a re-designed ACF is presented. An additional improvement is that byswitching inlet and outlet the usable time of the filters is prolonged.

  • 27.
    Nomura, Hideyuki
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Kamakura, Tomoo
    Estimation of parametric sound field controlled by source amplitudes and phases using numerical simulation2012Conference paper (Refereed)
    Abstract [en]

    The parametric array is formed by two finite-amplitude ultrasound beams with neighboring frequencies. The nonlinear interaction of the beams generates a highly directive audible sound at the difference frequency. Up to now, we have analyzed theoretically parametric sound fields in a free space. This study proposes a numerical simulation method of nonlinear ultrasound propagation to estimate the parametric sound field in the time domain. Using the finite-difference time-domain method based on the Yee algorithm with operator splitting, axisymmetric nonlinear propagation was simulated on the basis of equations for a compressible viscous fluid. As model application, a lengthlimited parametric sound beam, which is formed by four finite-amplitude ultrasound beams with different frequencies and controlled by phases and amplitudes of sound sources and has a truncated array length [C.M. Hedberg et al., Acoust. Phys. 56, 637–639 (2010)], was numerically simulated. The simulation showed a spatially restricted and very narrow difference frequency sound beam similar to their experiment. In addition, to investigate the dependence of amplitude and phase on the lengthlimited beam profiles, parametric sound fields were numerically estimated by varying the amplitude and phase slightly from the condition of the length-limited beam. Numerical results indicated that the changes of the amplitude and phase affected the beam length and width, in particular, amplitude changes drastically deformed the beam shape from that of the length-limited beam. This result suggests that precisely controlled sound sources are necessary to obtain the best length-limited sound beam.

  • 28. Nomura, Hideyuki
    et al.
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Kamakura, Tomoo
    Numerical simulation of length-limited parametric sound beam2011Conference paper (Refereed)
    Abstract [en]

    This study proposes a numerical simulation method that predicts nonlinear propagation of ultrasound beams in order to estimate the sound field of parametric array in the time domain. Basically, the method resorts to solving numerically and compactly the governing equations in a compressible viscous fluid using the Yee algorithm finite-difference time domain method. The simulation indicates a narrow audible sound beam which is a feature of the parametric array. Additionally, a length-limited parametric sound beam, which is proposed by Hedberg et al. [C. M. Hedberg et al., Acoust. Phys. 56, 637-639 (2010)], is numerically simulated as a model application. A pair of parametric sound sources generates the length-limited sound beam by control of the amplitudes and initial phases of the sources. The simulation shows a narrow truncated array length-limited sound beam.

  • 29. Nomura, Hideyuki
    et al.
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Kamakura, Tomoo
    Numerical simulation of parametric sound generation and its application to length-limited sound beam2012In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 73, no 12, p. 1231-1238Article in journal (Refereed)
    Abstract [en]

    In this study we propose a simulation model for predicting the nonlinear sound propagation of ultrasound beams over a distance of a few hundred wavelengths, and we estimate the beam profile of a parametric array. Using the finite-difference time-domain method based on the Yee algorithm with operator splitting, axisymmetric nonlinear propagation was simulated on the basis of equations for a compressible viscous fluid. The simulation of harmonic generation agreed with the solutions of the Khokhlov-Zabolotskaya-Kuznetsov equation around the sound axis except near the sound source. As an application of the model, we estimated the profiles of length-limited parametric sound beams, which are generated by a pair of parametric sound sources with controlled amplitudes and phases. The simulation indicated a sound beam with a narrow truncated array length and a width of about one-quarter to half that of regular a parametric beam. This result confirms that the control of sound source conditions changes the shape of a parametric beam and can be used to form a torch like low-frequency sound beam.

  • 30. Nomura, Hideyuki
    et al.
    Kamakura, Tomoo
    Clement, Gregory
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Visualization of parametric sound generation process based on wave number filtering using numerical simulation2012Conference paper (Refereed)
    Abstract [en]

    A parametric sound is generated from a nonlinear interaction of two or more intense ultrasounds at different but neighboring frequencies. The purpose of this study is to visualize the generation process of the parametric sound in a time domain using a numerical simulation. In particular, we focus on the generation of length-limited parametric sound beam, which is generated from a pair of parametric sound sources and indicates a truncated array length with a special radial beam pattern like a Mexican hat. To visualize nonlinear components, a simulated nonlinear sound wave is transformed into spatial spectra in a wave number space, and a nonlinear component such as the difference frequency sound is extracted using wave number filtering. The visualization of length-limited sound generation indicates discontinuities of wave fronts near a sound source. From the result, it is suggested that the discontinuity of wave front causes the special radial pattern of the beam with narrow width.

  • 31.
    Poskus, Karolis
    Blekinge Institute of Technology.
    Acoustic Analysis of Wave-Guide and MEMS Microphone in Camera Including Thermoviscous Losses2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today Micro Electrical Mechanical Systems (MEMS) microphones are available in a range of electronic consumer products such as smart phones, tablets, smartwatches and surveillance cameras. The MEMS microphones are usually attached to a circuit board with a hole that lets sound propagate through, as well as additional wave-guides which alter the MEMS microphones original frequency response. The MEMS microphone and additional wave-guides are in the same size order as the thermal and viscous boundary layers. These are called non-ideal losses and are usually not considered when dealing with large scale acoustical systems. The only way to predict the impact of these losses is the use of Finite Element software.

    The objective of the work is to model the thermoviscous losses when the waves propagate through narrow regions. The system of study is the Axis Network Camera P1367 and the study focuses on the acoustic path into the microphone. The first aim is to model the acoustic path along with the MEMS microphone to produce a frequency response that matches the measured frequency response of the different configurations for the sound-guide. A second aim is to find the configuration which produces the most desirable frequency response.

    Several measurements with different configurations were made, such as varying the length and radius of the sound-guide hole. All measurements were performed in an an-echoic chamber. Thereafter, a FEM model was created of the simplified acoustic path and the different configurations that were performed in the measurement were compared with the simulated results.

    The simulated frequency responses differ in terms of where the resonance frequency occurs, but the configurations of the sound-guide match the overall behavior when comparing the simulated and measured results. The most optimal configuration of the acoustical path is obtained.

    The simulated model requires more work in terms of obtaining a better matching frequency response, most importantly the MEMS cavity. The real geometry of the MEMS sensor cavity did not produce the same frequency response as the one in the data sheet for the specific microphone used for this study, thus a fictive cavity was introduced to produce the desired frequency response. The model did succeed in capturing the overall behavior as well as when the configuration was altered.

  • 32.
    Rudenko, Oleg
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    A nonlinear screen as an element for sound absorption and frequency conversion systems2016In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 62, no 1, p. 46-50Article in journal (Refereed)
    Abstract [en]

    The paper discusses a model for a screen with dissipative and nonlinear elastic properties that can be used in acoustic sound absorption and frequency conversion systems. Calculation and estimation schemes are explained that are necessary for understanding the functional capabilities of the device. Examples of the nonlinear elements in the screen and promising applications are described.

  • 33. Rudenko, Oleg
    The 40th Anniversary of the Khokhlov-Zabolotskaya Equation2010In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 56, no 4, p. 452-462Article in journal (Refereed)
    Abstract [en]

    The 40th anniversary of the Khokhlo-Zabolotskaya equation was marked by a special session of the 158th Meeting of the Acoustical Society of America (October 2009, San Antonio, Texas, United States). A response on the part of Acoustical Physics to this date is also quite appropriate, all the more so because Russian scientists were the main players involved in formulating and using this equation during the period of time between the middle 1960s and middle 1980s. In this article, the author—a participant and witness of those events—presents his view of the dramatic history of the formulation of this equation and related models in the context of earlier and independent work in aerodynamics and nonlinear wave theory. The main problems and physical phenomena described by these mathematical models are briefly considered.

  • 34.
    Rudenko, Oleg
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Оn strongly nonlinear waves and waves with strongly displayed weak nonlinearity2013In: Nonlinear Waves – 2012 / [ed] Gurbatov, S.N., Nizhny Novgorod: Institute of Applied Physics , 2013Chapter in book (Refereed)
  • 35. Rudenko, Oleg
    et al.
    Gurbatov, Sergey
    Hedberg, Claes
    Nonlinear Acoustics Through Problems and Examples2010Book (Other academic)
    Abstract [en]

    The fundamentals of nonlinear acoustics are presented in form of problems followed by solutions, explanations and answers. As distinct from existing textbooks, this book of problems not only helps the reader to become familiar with nonlinear wave processes and the methods of their description, but contributes to mastering calculation procedures and obtaining numerical estimates of the most significant parameters. Thereby, skills are acquired which are indispensable for carrying out original scientific research. This book can be useful to undergraduate and postgraduate students and researchers working in the field of nonlinear wave physics and acoustics.

  • 36.
    Rudenko, Oleg
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Gurbatov, S.N.
    Inverse problem of nonlinear acoustics: Synthesizing intense signals to intensify the thermal and radiation action of ultrasound2016In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 62, no 4, p. 418-428Article in journal (Refereed)
    Abstract [en]

    Inverse problems of nonlinear acoustics have important applied significance. On the one hand, they are necessary for nonlinear diagnostics of media, materials, manufactured articles, building units, and biological and geological structures. On the other hand, they are needed for creating devices that ensure optimal action of acoustic radiation on a target. However, despite the many promising applications, this direction remains underdeveloped, especially for strongly distorted high-intensity waves containing shock fronts. An example of such an inverse problem is synthesis of the spatiotemporal structure of a field in a radiating system that ensures the highest possible energy density in the focal region. This problem is also related to the urgent problems of localizing wave energy and the theory of strongly nonlinear waves. Below we analyze some quite general and simple inverse nonlinear problems. © 2016, Pleiades Publishing, Ltd.

  • 37.
    Rudenko, Oleg
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Gurbatov, S.N.
    Demin, I. Yu
    Nonlinear noise waves in soft biological tissues2013In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 59, no 5, p. 584-589Article in journal (Refereed)
    Abstract [en]

    The study of intense waves in soft biological tissues is necessary both for diagnostics and therapeutic aims. Tissue represents an inherited medium with frequency-dependent dissipative properties, in which waves are described by nonlinear integro-differential equations. The equations for such waves are well known. Their group analysis has been performed, and a number of exact solutions have been found. However, statistical problems for nonlinear waves in tissues have hardly been studied. As well, for medical applications, both intense noise waves and waves with fluctuating parameters can be used. In addition, statistical solutions are simpler in structure than regular solutions; they are useful for understanding the physics of processes. Below a general approach is described for solving nonlinear statistical problems applied to the considered mathematical models of biological tissues. We have calculated the dependences of the intensities of the narrowband noise harmonics on distance. For wideband noise, we have calculated the dependence of the spectral integral intensity on distance. In all cases, wave attenuation is determined both by the specific dissipative properties of the tissue and the nonlinearity of the medium.

  • 38.
    Rudenko, Oleg
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Gurbatov, S.N.
    Demin, I.Yu.
    Absorption of intense regular and noise waves in relaxing media2014In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 60, no 5, p. 499-505Article in journal (Refereed)
    Abstract [en]

    An integro-differential equation is written down that contains terms responsible for nonlinear absorption, visco-heat-conducting dissipation, and relaxation processes in a medium. A general integral expression is obtained for calculating energy losses of the wave with arbitrary characteristics-intensity, profile (frequency spectrum), and kernel describing the internal dynamics of the medium. It is shown that for weak waves, the general integral leads to well-known results of a linear approximation. Profiles of stationary solutions are constructed both for an exponential relaxation kernel and for other types of kernels. Energy losses at the front of week shock waves are calculated. General integral formulas are obtained for energy losses of intense noise, which are determined by the form of the kernel, the structure of the noise correlation function, and the mean square of the derivative of realization of a random process

  • 39.
    Rudenko, Oleg
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Hedberg, Claes
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Diffraction of high-intensity field in focal region as dynamics of nonlinear system with low-frequency dispersion2015In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 61, no 1, p. 28-36Article in journal (Refereed)
    Abstract [en]

    The stationary profile in the focal region of a focused nonlinear acoustic wave is described. Three models following from the Khokhlov-Zabolotskaya (KZ) equation with three independent variables are used: (i) the simplified one-dimensional Ostrovsky-Vakhnenko equation, (ii) the system of equations for paraxial series expansion of the acoustic field in powers of transverse coordinates, and (iii) the KZ equation reduced to two independent variables. The structure of the last equation is analogous to the Westervelt equation. Linearization through the Legendre transformation and reduction to the well-studied Euler-Tricomi equation is shown. At high intensities the stationary profiles are periodic sequences of arc sections having singularities of derivative in their matching points. The occurrence of arc profiles was pointed out by Makov. These appear in different nonlinear systems with low-frequency dispersion. Profiles containing discontinuities (shock fronts) change their form while passing through the focal region and are non-stationary waves. The numerical estimations of maximum pressure and intensity in the focus agree with computer calculations and experimental measurements. © 2015, Pleiades Publishing, Ltd.

  • 40.
    Rudenko, Oleg
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Strong and weak nonlinear dynamics: Models, classification, examples2013In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 59, no 6, p. 664-650Article in journal (Refereed)
    Abstract [en]

    The difference between strong and weak nonlinear systems is discussed. A classification of strong nonlinearities is given. It is based on the divergence or inanity of series expansions of the equation of state commonly used in the study of weak nonlinear phenomena. Such power or functional series cannot be used in three cases: (i) if the equation of state contains a singularity; (ii) if the series diverges for strong disturbances; (iii) if the linear term is absent, and higher nonlinearity dominates. Strong nonlinearities are known in acoustics, optics, mechanics and in quantum field theory. Mathematical models, solutions and observed phenomena are presented. For example, an equation of Heisenberg type and its generalization for strongly nonlinear wave system are given. In particular, exact solutions of new “quadratically cubic” Burgers and Riemann–Hopf equations are discovered.

  • 41.
    Rudenko, Oleg
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Strongly nonlinear waves? A new trend of nonlinear acoustics2013Conference paper (Refereed)
    Abstract [en]

    Strongly nonlinear waves (SNWs) and extreme states of matter are key physical concepts. A SNW is a wave whose amplitude is on the order of the material's internal strength limit. When a shock front appears at a distance of 10∧2-10∧3 wavelengths in water, nonlinearity is weak but strongly expressed. The acoustic pressure is 10∧5-10∧6 Pa, much less than the internal pressure 2.2*10∧9 Pa. However, impurities decrease the breaking strength, and waves creates bubbles at smaller pressures. An explosive wave is also a SNW, breaking solids. For weakly nonlinear waves (WNWs) the equation of state can be expanded in power or functional series. However, these cannot be used in 3 cases. First, if the equation contains singularities, like for "clapping" and Hertz nonlinearities of heterogeneous solids. Secondly, if the series is divergent. Thirdly, when the linear term is absent and the higher nonlinearities dominate. Such SNWs appear in mechanics and in quantum field theory.

  • 42.
    Rudenko, Oleg
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    The phenomenon of self-trapping of a strongly nonlinear wave.2014In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 135, no 4Article in journal (Refereed)
    Abstract [en]

    Self means here an effect of a wave on itself. Several self-action phenomena are known in nonlinear wave physics. Among them are self-focusing of beams self-compression of light pulses self-channeling self-reflection (or self-splitting) waves with shock fronts self-induced transparency and self-modulation. These phenomena are known for weakly nonlinear waves of different physical origin. Our presentation at ASA meeting in Montreal [POMA 19 045080 (2013)] was devoted to strongly nonlinear waves having no transition to the linear limit at infinitesimally small amplitudes. Such waves can demonstrate particle-like properties. Self-trapping consists of the arrest of wave propagation and in the formation of a localized state. In particular the model generalizing the Heisenberg' ordinary differential equation to spatially distributed systems predicts periodic oscillations but no traveling waves. Different models for strongly nonlinear waves will be considered and some unusual phenomena will be discussed. Preliminary results were published in Ac. Phys. 59 584 (2013) and Physics-Uspekhi (Adv. Phys. Sci.) 183 683 (2013). [This work was supported by the Megagrant No.11.G34.31.066 (Russia) and the KK Foundation (Sweden).

  • 43.
    Rudenko, Oleg
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Hedberg, Claes
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    The quadratically cubic Burgers equation: an exactly solvable nonlinear model for shocks, pulses and periodic waves2016In: Nonlinear dynamics, ISSN 0924-090X, E-ISSN 1573-269X, Vol. 85, no 2, p. 767-776Article in journal (Refereed)
    Abstract [en]

    A modified equation of Burgers type with a quadratically cubic (QC) nonlinear term was recently pointed out as a new exactly solvable model of mathematical physics. However, its derivation, analytical solution, computer modeling, as well as its physical applications and analysis of corresponding nonlinear wave phenomena have not been published up to now. The physical meaning and generality of this QC nonlinearity are illustrated here by several examples and experimental results. The QC equation can be linearized and it describes the experimentally observed phenomena. Some of its exact solutions are given. It is shown that in a QC medium not only shocks of compression can be stable, but shocks of rarefaction as well. The formation of stationary waves with finite width of shock front resulting from the competition between nonlinearity and dissipation is traced. Single-pulse propagation is studied by computer modeling. The nonlinear evolutions of N- and S-waves in a dissipative QC medium are described, and the transformation of a harmonic wave to a sawtooth-shaped wave with periodically recurring trapezoidal teeth is analyzed. © 2016 The Author(s)

  • 44. Rudenko, Oleg
    et al.
    Korobov, A
    Izosimova, M
    Nonlinearity of Solids with Micro- and Nanodefects and Characteristic Features of Its Macroscopic Manifestations2010In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 56, no 2, p. 151-157Article in journal (Refereed)
    Abstract [en]

    The meaning of the experimentally measured nonlinear parameters of a medium is discussed. The difference in meaning between the local nonlinearity, which is measured in the vicinity of a single defect and depends on the size of the region of averaging, and the effective volume nonlinearity of the medium containing numerous defects is emphasized. The local nonlinearity arising at the tip of a crack is calculated; this nonlinearity decreases with an increase in the region of second harmonic generation. The volume nonlinearity is calculated for a solid containing spherical cavities. The volume nonlinearity is also calculated for a medium containing infinitely thin cracks in the form of circular disks, which assume the shape of ellipsoids in the course of the crack opening. The nonlinear acoustic parameter is calculated with the use of the exact classical results of the theory of cracks.

  • 45. Rudenko, Oleg
    et al.
    Schvartburg, A
    Nonlinear and Linear Wave Phenomena in Narrow Pipes2010In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 56, no 4, p. 429-434Article in journal (Refereed)
    Abstract [en]

    Phenomena arising in the course of wave propagation in narrow pipes are considered. For nonlinear waves described by the generalized Webster equation, a simplified nonlinear equation is obtained that allows for low frequency geometric dispersion causing an asymmetric distortion of the periodic wave profile, which qualitatively resembles the distortion of a nonlinear wave in a diffracted beam. Tunneling of a wave through a pipe constriction is investigated. Possible applications of the phenomenon are discussed, and its relation to the problems of quantum mechanics because of the similarity of the basic equations of the Klein– Gordon and Schrödinger types is pointed out. The importance of studying the tunneling of nonlinear waves and broadband signals is indicated.

  • 46.
    Rudenko, Oleg
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Sobisevich, A. L.
    Sobisevich, L.E.
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Shamaev, N. V.
    Nonlinear model of a granulated medium containing viscous fluid layers and gas cavities2012In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 58, no 1, p. 99-106Article in journal (Refereed)
    Abstract [en]

    We analyze nonlinear oscillations and waves in a simple model of a granular medium containing inclusions in the form of fluid layers and gas cavities. We show that in such a medium, the velocity of one of the wave modes is low; therefore, the nonlinearity is high and the effects of interaction are more strongly expressed than usual.

  • 47. Rudenko, Oleg
    et al.
    Stepanov, P. V. Lebedev
    Gusev, V. A.
    Korobov, A. I.
    Korshak, B. A.
    Odina, N. I.
    Izosimova, M.
    Molchanovb, S. P.
    Alfimov, M. V.
    Control of the Self-Assembly Processes in a Droplet of a Colloidal Solution by an Acoustic Field2010In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 56, no 6, p. 935-941Article in journal (Refereed)
    Abstract [en]

    The formation of structured films consisting of ensembles of micro- or nanoparticles and possessing preset functional characteristics is studied both experimentally and theoretically. The films are obtained by drying out droplets of colloidal solutions on a solid substrate under the acoustic effect produced by a standing SAW field.

  • 48.
    Rudenko, Oleg
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    YN, Makov
    SN, Gurbatov
    Blood flow dynamics under venipuncture and viscosity estimation from pressure and flow variations2013In: Acoustical Physics, ISSN 1063-7710, E-ISSN 1562-6865, Vol. 59, no 1, p. 109-114Article in journal (Refereed)
    Abstract [en]

    We have calculated the nonstationary flow of a viscous liquid in a narrow tube under the action of pressure variations with time. Such a flow accompanies venipuncture the procedure of taking a sample from a vein with a hypodermic needle. We show how the changes in the flow characterstics during venipuncture make it possible to actively estimate viscosity. This method is "nonperturbative" for blood in the sense that the measurement process weakly affects the measured quantity. It may find application in medicine.

  • 49. Sarvazyan, Armen
    et al.
    Rudenko, Oleg
    Nyborg, Wesley
    Biomedical applications of radiation force of ultrasound: Historical roots and physical basis2010In: Ultrasound in Medicine and Biology, ISSN 0301- 5629, Vol. 36, no 9, p. 1379-1394Article, review/survey (Refereed)
    Abstract [en]

    Radiation force is a universal phenomenon in any wave motion, electromagnetic or acoustic. Although acoustic and electromagnetic waves are both characterized by time variation of basic quantities, they are also both capable of exerting a steady force called radiation force. In 1902, Lord Rayleigh published his classic work on the radiation force of sound, introducing the concept of acoustic radiation pressure, and some years later, further fundamental contributions to the radiation force phenomenon were made by L. Brillouin and P. Langevin. Many of the studies discussing radiation force published before 1990 were related to techniques for measuring acoustic power of therapeutic devices; also, radiation force was one of the factors considered in the search for noncavitational, nonthermal mechanisms of ultrasonic bioeffects. A major surge in various biomedical applications of acoustic radiation force started in the 1990s and continues today. Numerous new applications emerged including manipulation of cells in suspension, increasing the sensitivity of biosensors and immunochemical tests, assessing viscoelastic properties of fluids and biological tissues, elasticity imaging, monitoring ablation of lesions during ablation therapy, targeted drug and gene delivery, molecular imaging and acoustical tweezers. We briefly present in this review the major milestones in the history of radiation force and its biomedical applications. In discussing the physical basis of radiation force and its applications, we present basic equations describing the relationship of radiation stress with parameters of acoustical fields and with the induced motion in the biological media. Momentum and force associated with a plane-traveling wave, equations for nonlinear and nonsteady-state acoustic streams, radiation stress tensor for solids and biological tissues and radiation force acting on particles and microbubbles are considered.

  • 50. Schenkman, Bo
    et al.
    Nilsson, Mats E.
    Human echolocation: Blind and sighted persons' ability to detect sounds recorded in the presence of a reflecting object2010In: Perception, ISSN 0301-0066 , Vol. 39, no 4, p. 483-501Article in journal (Refereed)
    Abstract [en]

    Research suggests that blind people are superior to sighted in echolocation, but systematic psychoacoustic studies on environmental conditions such as distance to objects, signal duration, and reverberation are lacking. Therefore, two experiments were conducted. Noise bursts of 5, 50, or 500 ms were reproduced by a loudspeaker on an artificial manikin in an ordinary room and in an anechoic chamber. The manikin recorded the sounds binaurally in the presence and absence of a reflecting 1.5-mm thick aluminium disk, 0.5 in in diameter, placed in front, at distances of 0.5 to 5 m. These recordings were later presented to ten visually handicapped and ten sighted people, 30 62 years old, using a 2AFC paradigm with feedback. The task was to detect which of two sounds that contained the reflecting object. The blind performed better than the sighted participants. All performed well with the object at < 2 in distance. Detection increased with longer signal durations. Performance was slightly better in the ordinary room than in the anechoic chamber. A supplementary experiment on the two best blind persons showed that their superior performance at distances > 2 m was not by chance. Detection thresholds showed that blind participants could detect the object at longer distances in the conference room than in the anechoic chamber, when using the longer-duration sounds and also as compared to the sighted people. Audiometric tests suggest that equal hearing in both ears is important for echolocation. Possible echolocation mechanisms are discussed.

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