bluuebunny/crossref_metadata_2025 huggingface dataset:
The interaction of microbubbles with high intensity pulsed ultrasound
Authors: Fong Siew Wan , Klaseboer Evert , Khoo Boo Cheong
Published: May 2008

High intensity pulsed ultrasound when interacting with microbubble contrast agents is potentially useful for biomedical applications such as drug delivery, cancer treatment and tissue ablation. To establish a fundamental understanding of the interaction between a microbubble with a sound wave, numerical simulations are performed using the Boundary Element Method (BEM). Bubble dynamics in terms of shape changes in time, maximum bubble radius obtained, jet velocity and translational movement of the bubble center is studied. The effect of varying ultrasound intensity and initial bubble size is examined as well. One important result is the determination of the conditions under which a clear high speed jet will be formed in the microbubble when it is hit by a specific sound wave. The jet is crucial to the success of the biomedical applications mentioned. Also, it is shown that one cycle of ultrasound consisting of a single negative part followed by a single compressive part would be the optimized wave form because collateral damage by re-expanding remnants of a collapsed microbubble by the subsequent negative pressure wave is prevented. The BEM model has greater computational efficiency in terms of speed and storage space over other full domain methods because only surface meshing is needed.
Evaluation of performance in some ultrasonic procedures for non-invasive thermal estimation into hyperthermia phantoms
Authors: Bazan Ivonne , Ramos Antonio , Vazquez Monica , Vera Arturo , Leija Lorenzo
Published: May 2008

To dispose of a precise and non-invasive temperature measurement over the treated area becomes very important during hyperthermia treatments, in order to make possible an optimization of their healing effects. A performance analysis of some previously reported ultrasonic techniques, which were proposed for non-invasive temperature estimation, is made in this work over phantoms mimicking human tissues. A first technique is based on discrete scattering modeling for tissue characterization and spectral analysis of frequency distributions related to average scatters spacing [R. Seip & E.S. Ebbini]. Other technique uses certain relations between tissue temperature changes and time-shifts in echoes due to thermally induced sound velocity changes and expansions [R. Maass-Moreno & C.A. Damianou]. And finally, the third procedure analyzed here, is a recently proposed alternative, based on phase demodulation processing, to estimate the indirect effects of echoes time-shifts in the phase domain [M. Vázquez, A. Ramos, et al.]. The three options are analyzed for the same simulated & measured multi-pulse echo patterns, looking for detecting possible advantages and inconveniences in each case. Finally, some improvement paths over the basic estimation methods are also explored.
Effect of inclination of articular surface on ultrasonic surface reflection and surface roughness in diagnosing cartilage degeneration
Authors: Kaleva Erna , Saarakkala Simo , Töyräs Juha
Published: May 2008

High-frequency Quantitative Ultrasound Imaging is a potential method for detecting early osteoarthrotic changes in articular cartilage. However, uncontrolled inclination of the ultrasound transducer or the curvature of the cartilage surface can jeopardize the reliability of the method. Visually intact and mechanically degraded osteochondral bovine patellae samples were imaged using a scanning acoustic microscope equipped with a 50 MHz ultrasound transducer. The surfaces of the sample and transducer were adjusted to a known relative inclination in three sequential scans (0, 2 and 5 degrees). Surface reflection was evaluated in time and frequency domains and surface roughness in time domain as a function of the inclination. Inclination of the surface of the sample had a greater effect on the reflection than on the roughness value. Despite the inclination-induced error, the degraded sample could be distinguished from the intact one at all inclinations with both the reflection and roughness parameters. However, as the inclination affected the reflection parameters significantly more, their reliability at greater inclinations is questionable. Furthermore, the proportion of scattering vs. reflection may change as a function of inclination. Provided that the amount of scattering varies against cartilage surface fibrillation, this can affect the reliability of ultrasound diagnostics significantly.
Measurement of dynamic shear modulus in soft solids using laser vibrometry
Authors: Izosimova Maria Y. , Korobov Alexandr I. , Prokhorova Ekaterina V. , Sapozhnikov Oleg A.
Published: May 2008

Shear modulus is an important property of biological tissue and can be imaged for diagnostic purposes. A related application involves the acquisition of precise shear modulus measurements in excised soft tissue. Because the mechanical properties of tissue are frequency-dependent, it is important to develop methods that characterize the elasticity of soft solids at various frequencies. Here, two methods of measuring shear modulus are presented that employ laser vibrometry. At low frequencies (1-10 Hz), the tissue sample is fixed between plates so that the displacement of one plate induces a shear strain. Vibrometer measurements of the plate displacement define the induced strain so that shear modulus can be deduced if the applied shear force is known. At higher frequencies (0.1-10 kHz), the sample lays flat on a surface and an impulsive force is applied to the exposed surface. Using the vibrometer to measure displacements along the exposed surface enables estimation of the surface wave speed and the implied shear modulus. To demonstrate the capabilities of these techniques, experiments were performed using plastisol tissue phantom samples. These experiments indicated a shear modulus that was 50% greater at high frequencies (300 Hz) than at low frequencies (10 Hz). Work supported by RFBR.
Instrumentation Synchonization Techniques for Large Microphone Arrays
Authors: Veggeberg Kurt
Published: May 2008

In many acoustic measurement applications, there is a need to correlate data acquired from different systems or synchronize systems together with precise timing. Signal Based and Time Based are the two basic methods of synchronizing instrumentation. In Signal Based synchronization, clocks and triggers are physically connected between systems. Typically this provides the highest precision synchronization. In many acoustic applications size and distance constrains physically connecting the systems needed for making measurements though the inter-channel phase information of simultaneously sampled signals is crucial. In Time Based synchronization, system components have a common reference of what time it is. Events, triggers and clocks can be generated based on this time. This is an overview of how you can use a variety of time references including GPS, IEEE-1588, and IRIG-B to correlate and synchronize measurements anywhere in the world with absolute timing with and without a direct connection between the measurement systems. The level of precision of the variety of methods that can be used for timestamping, generating a trigger at a user specified time as well as synchronizing multiple instrumentation types is covered. Specific applications where this has been applied to large microphone arrays will be described.
Acoustic payload on an aerostat detects and locates transient sources
Authors: Scanlon Michael V. , Reiff Christian , Solomon Latasha
Published: May 2008

The US Army Research Laboratory (ARL) has conducted experiments using acoustic sensor arrays suspended below tethered aerostats to detect and localize transient signals from mortars, artillery, and small arms fire. The airborne acoustic sensor array calculates an azimuth and elevation to the originating transient, and immediately cues a collocated imager to capture the remaining activity at the site of the acoustic transient. This single array's vector solution defines a ground-intersect region or grid coordinate for threat reporting. Unattended ground sensor (UGS) systems can augment aerostat arrays by providing additional solution vectors from several ground-based acoustic arrays to perform a 3D triangulation on a source location. The aerostat array's advantage over ground systems is that it is not as affected by diffraction and reflection from man-made structures, trees, or terrain, and has direct line-of-sight to most events. Helicopter detection and tracking algorithms can also be implemented.
Mechanism detection of stress corrosion cracking by acoustic emission and effect of manufacturing process on AE signals
Authors: Heidary Hossein , Refahi Oskouei Amir , Ahmadi Mehdi
Published: May 2008

Stress corrosion cracking could occur wherever a specific corrodent and sufficient tensile stresses coexist. In the objective to monitor online the SCC on real structures, it seems reasonable to characterize and recognize acoustic emission during static U-bend tests. The present study is concerned with static tests on 304 stainless steels in two different media (5% HCl and 5% H2SO4) in order to find a criterion to distinguish, the two different mechanism of SCC (anodic dissolution and hydrogen embrittlement) by characteristic parameters and waveform analysis of AE signals. In the next stage, effect of residual stress on stress corrosion cracking in chloride solution has been studied. Three samples have been prepared: one of them was stress relieved; the second one was made sensitive to SCC by heat treatment and the last one was cold worked by rolling. Cumulative count, amplitude distribution and waveform analysis were selected as AE-parameters. AE with amplitudes ranging from 39 to 65 dB with different counts and energy occurred during SCC of SS-304 at room temperature. According to the results, acoustic emission is able to be used as robust technique for mechanism detection of SCC. In addition it can be used to measure the effect of residual stress in manufacturing process on SCC.
PVB mechanical constants characterization in laminated glasses using low frequency ultrasound
Authors: Ramis Soriano Jaime , Frances Monllor Jorge , Alba Fernandez Jesús , Segovia Eulogio Enrique E. , Vera Guarinos Jenaro
Published: May 2008

To predict the behaviour of a partition made of laminated glasses, it's necessary to know the parameters of the layers composing it. These types of devices are composed by monolithic glass and an intermediate muffling layer usually made of PVB. In this study, we present a method to find the mechanical constants of PVB in laminated glasses. Mechanical constants characterization in these materials is studied using a model-based inverse problem and the data obtained from an ultrasonic transmission setup: a numerical simulation of the system is proposed using a lineal finite elements model of the ultrasonic propagation on the multilayered solid. Parameters are obtained by minimizing divergences between experimental and numerically predicted waveform.
High Accuracy Multisensor Hydroacoustic System for Models of Trawl Geometry Measurements
Authors: Marszal Jacek
Published: May 2008

The new high accuracy multisensor hydroacoustic system for models of trawl geometry measurements was designed for developing the construction of cod trawl net for the Baltic fishery. The system consist of 20 miniature hydrophones attached by the light-gauge cables to the measuring microprocessor device and notebook computer. The pulse excitation at high frequency and correlation digital signal processing make it possible to obtain high resolution of measurements. Additionally each of hydrophones is equipped with the thermistor which is used to calculate the local sound velocity and enable precision calibration of obtained measururing data. This method of calibration is particularly important for measurements investigated in the surface water layer with the high temperature gradient. The construction details, the measuring signal processing algorithms as well as examples of obtained data and the accuracy verification will be presented in the paper.
Transient behaviour of human and artificial brass players' lips
Authors: Stevenson Samuel , Campbell Donald M. , Chick John , Gilbert Joël , Bilbao Stefan
Published: May 2008

It is widely accepted that the starting transient is an extremely significant perceptual feature of musical sound. For players, the ease with which a note can be started on a particular instrument is also of great importance. However, until recently research has concentrated on the analysis of steady state sounds rather than the study of the starting behaviour of the instrument. The work reported here uses a high speed camera to capture the motion of lip reeds during the starting transient. Simultaneous recordings are made of the pressure signals generated in the mouthpiece of the instrument and radiated from the bell. Preliminary results on human players, already presented, have been extended and supplemented by measurements using an artificial mouth in order to separate effects due to the instrument from those dependent on the expertise of a particular human player. Computational simulations have been compared to these experimental findings.
Open and closed loop characterization of an air-jet reflection amplifier
Authors: Price John C.
Published: May 2008

Our laboratory has embarked on an effort to understand the steady-state behavior of a Yamaha YRT-304B tenor recorder. The instrument is split at the head-joint, and both sides are studied with a multi-microphone reflectometer using sinusoidal excitation. For the head joint, data is obtained versus frequency, blowing pressure, and excitation amplitude. We have two goals: First, to use our open-loop reflectometry data to understand the internal acoustic spectrum of the assembled instrument, as a function of blowing pressure and fingering; and second, to provide a well-defined set of open-loop observables for comparison with hydrodynamic calculations of the air-jet dynamics. This particular instrument is attractive for several reasons: it disassembles at a straight cylindrical section of the bore, and so is easily coupled to straight waveguide; it is large enough for accurate reflection coefficient and internal pressure measurements; it can be studied closed-loop as a complete instrument; and it represents a fiducial geometry that is readily available to any laboratory.
Measurements of woodwind tone-hole parameters using a double impedance head method
Authors: Dickens Paul , Kulik Yakov , Wolfe Joe
Published: May 2008

A woodwind tone hole is often represented as a T-junction with a shunt and series impedance. We measured the frequency dependence of the series and shunt impedances of open and closed tone holes using a pair of impedance heads, one on either side of a symmetric section of short bore pipe with a finger hole, and each calibrated on resonance-free loads. The shunt impedance is most accurately measured when the hole is located at a pressure anti-node (speakers in phase) and the series impedance at a pressure node (speakers in anti-phase). We use both conditions, in this way, to measure series and shunt impedances for all frequencies studied. Pipes with the same length and diameter, but having wall thicknesses 1.5-5.0 mm and tone hole diameters 1.5-15.0 mm were used. For open holes, results are compared with calculations and results measured using other methods. The results for holes closed with fingers are also used to calculate the effective length of finger intrusion. Examples of the inclusion of the results into woodwind models are given.
Sopranos' secondo passagio: a resonance adjustment and/or a laryngeal transition to the whistle voice
Authors: Garnier Maeva , Henrich Nathalie , Smith John , Wolfe Joe
Published: May 2008

How are glottal source and vocal tract involved in the sopranos' passagio around E5? This pilot study investigates a legit soprano singing C5 to C6 with a lyrical technique and C5 to D7 in a "light" voice. On (de)crescendi and glissandi over the passagio, we observed clear bifurcations from "light" to lyrical mode, with discontinuous changes in f0, larynx vertical position, amplitude and shape of the electroglottographic signal. No such discontinuities occurred from C5 to D7 within the "light" mode. We established phonetograms of both modes and characterised differences in voice quality (Spectrum, Harmonicity, Open quotient). For [oe] in both modes, this singer tunes the first vocal tract resonance (R1) to f0 over the passagio. For a free vowel, a single and strong resonance is observed in the "light" mode, which may correspond to the merging of R1 and R2 and which is tuned to 2 f0 below C6, then to f0 until F6. Above F#6, two resonances are observed again and R2 is tuned to f0. All these observations suggest that, for this singer, the secondo passagio may correspond to both a resonance adjustment and a transition from the second laryngeal mechanism to the third, also called whistle voice.
Nonlinear propagation of spark-generated N-waves in atmosphere: theoretical and experimental assessment of the shock front structure
Authors: Yuldashev Petr V. , Averiyanov Mikhail V. , Khokhlova Vera A. , Sapozhnikov Oleg A. , Sebastien Ollivier , Blanc-Benon Philippe
Published: May 2008

Extensive outdoor and laboratory-scale experiments on sonic boom propagation in turbulent atmosphere have shown that shock wave amplitude and rise time are important parameters responsible for sonic boom annoyance. However, accurate measurement of the shock front structure with standard microphone remains a challenge due to the broadband spectrum of the N-wave shock front. In this work the experimental setup utilizing a spark source has been designed and built to investigate nonlinear N-wave propagation in homogeneous medium. Short duration (30μs) and high amplitude (1 kPa) spherically divergent N-waves were generated. In addition to acoustic measurements with 1/8" B&K microphones, the shadowgraphy method using short duration flash lamp (20 ns) and CCD camera was employed to assess the shock front structure at different distances from the spark. It is shown that the shock rise time measured by the shadowgraphy method was in a good agreement with the theoretical predictions and it was 10 times shorter than in microphone measurements. The widening of the shock in acoustic measurements was therefore due to the limited bandwidth of the microphone. The combination of modeling, acoustic and optical measurements provided an accurate calibration of the shock wave measuring system. [Work supported by RFBR and INTAS.]
Acoustic test facility for aero engine fans
Authors: Khaletskiy Yuri , Mileshin Victor , Shipov Rollan
Published: May 2008

The facility for acoustic tests of aero engine fans in conditions of anechoic chamber is created in Central Institute of Aviation Motors (Moscow). The facility is designed for testing models of single rotating fans and counter rotating fans. The measurements of the sound are carried out in forward and rearward semi-spheres simultaneously. Design features of the anechoic chamber and its acoustic performance are presented. Also a fan drive system and systems of acoustic and aerodynamic measurements are described. In particular fan rotor max rotation frequency makes up 13,000 rpm at each shaft max power 2.5 MW. The rig acquisition system allows checking in real time results of complete three-octave analysis of machine noise on all 24 channels in a measurement frequency range of 0œ80 kHz.
Noise limits and noise levels along motorways in Europe
Authors: Alberts Wiebe
Published: May 2008

Environmental noise caused by traffic is one of the main local environmental problems in Europe. The National Road Authorities (NRA's), combined in the Conference of European Directors of Roads (CEDR), are aware of the environmental noise problem along their motorways. One of the main objectives of CEDR is to facilitate knowledge sharing on noise abatement issues among European NRA's. The CEDR noise group has made a comprehensive questionnaire survey on how the CEDR member states handle noise issues. The paper focuses on the part of the survey on noise limits and noise levels along motorways throughout Europe. It will deal with the: - status of noise limits; - noise indicators to express noise limits; - noise limits (outdoor and indoor) for motorways; - noise models to calculate noise levels. Due to the use of different noise indicators and different noise calculation models, the comparison of noise levels and noise limits along motorways in Europe is complicated to say the least. The only way to solve this problem is to have and to use a European noise model for road traffic based on the outcome of the HARMONOISE/IMAGINE projects.
A proposal for doing a touch of anova with noise levels
Authors: Maurin Michel
Published: May 2008

Because noise levels are logarithm of additive variables, the usual numerical processings are not suitable for them (mind 60+60≠120). Then one has to deal with them differently, following some other syntaxic rules which may be called in a general way the "logic of levels". Of course this question is correctly resolved with the "energetic mean" but it fails as soon as one has to deal with variances of levels or covariances with other variables (data analysis, linear regressions, œ). Some (necessarily) approximate compromises may be developped between the logic of levels and the arithmetical logic, (transforming variables in statistics for instance). Here we introduce a new statistic, the h-dispersion, which is not a variance but has many properties of variance, and very fortunatly takes account of the logarithmic status of data. This new compromise may be employed for levels in some cases of design of experiments, such as one-way cases and comparisons "before-after" in relation to acoustics operations for instance, and also more or less for two-ways cases. It remains approximate (a syntaxic compromise), but in any time this is an improvement in comparison with a crude ANOVA on levels.
A guideline for prediction and control of noise in railroads maintenance activities
Authors: Luzzi Sergio
Published: May 2008

In railroads routine maintenance as well as emergency maintenance can be represented by the acoustic point of view as a system of classified yard activities, including catalogued single and grouped noise sources, that is moved along the tracks areas. RFI (Rete Ferroviaria Italiana), the Italian National Railway Company, has provided a guideline for the correct evaluation of noise impact on receivers surrounding the yards, which can be adapted to many situations fitting the specific national law and local regulations disposals about noise assessment, prediction and reduction in temporary activities. Starting from their long term experience, the authors have developed a method for the production of local reports on maintenance railroad yard activities based on the modelling of standard scenarios. Each machinery employed in yards (for superstructure laying or repairing, electric traction, etc,) has been measured and characterized as noise source or as part of a noise sources system (emission box). The noise propagation scenarios are then build using an MS Excel based adaptation software. This methodology represents the technical and procedural architecture of the guideline which provides materials for the management of all the different typologies of maintenance yards operating on the RFI railroad network.
Numerical and analytical models for high speed train pantograph radiated noise prediction
Authors: Viscardi Massimo , Iadevaia Michele , Melchionna Salvatore , Lecce Leonardo
Published: May 2008

The present work deals with the development and comparison of an analytical and numerical models for the evaluation of the noise radiated from a pantograph of an high speed train. Under the numerical point of view, a simplified model has been developed for the pantograph; the model that substructures the problem approaching a complex structure as a combination of simple components, has been derived from a similar aeronautical problem (landing gear noise) but has been self-modified to adapt the formulation to the specific problem. The output of the model is the radiated noise level and spectra as a function of the pantograph speed. The CFD numerical model has been developed for the pantograph based upon a commercial code; only the upper part of the system has been herein simulated because it was addressed as the main noise source during previous laboratory acoustic tests. As an output of the model, the radiated noise has been derived with special reference to two main speed to which experimental data could be referred. Analytical and numerical results will be within the paper discussed and compared to highlight the single approach's advantage and drawbacks. At the and of the paper, some line experimental results will be also introduced and discussed.
Questionnaire survey on vehicle horn use
Authors: Takada Masahiko , Fukuda Yoko , Iwamiya Shin-Ichiro
Published: May 2008

The Japanese Road Traffic Law provides that a vehicle horn should be utilized in the dangerous situation or the place where the horn sign was installed. However, drivers are frequently seen to use their vehicle's horn as a signal in the situations when they pass each other. Given such situations, the mentioned above law is likely to become a law in name only. Therefore, a questionnaire survey was carried out to ascertain the current circumstance of a vehicle horn use. The respondents were asked the latest or last remembered case of horn use in various situations of both their driving or as pedestrians. With regards to an experience of being tooted at by another driver, the questionnaire included questions concerning place, traffic volume, the aim of the horn use, time pattern of horn tooting, respondent's mental reaction when tooted at by another driver, etc. As a result, drivers mostly had negative mental reactions (i.e., startled, noisy and irritating) by long toots. Pedestrians' negative mental reactions were mainly aroused by horn use calling another's attention to something or to inform of a danger. Furthermore, nearly 40 percent of the respondents were discontented with the volume and the sound quality of horn.
3D noise map of an hospital and noise sources evaluation
Authors: Sequeira Goncalves Paulo J.
Published: May 2008

This paper presents the tri-dimensional acoustical characterization of Castelo Branco Hospital. Traffic and air conditioning machines produce noise that influences the Hospital and the buildings nearby. The results are presented in two dimensions at a height of four meters above the ground and in the vertical direction to access the noise levels in the building floors. For the construction of the model were used and compared to types of measurements of vehicles counting, for characterization of the traffic noise. The first approach was performed at every hour during the 24 hours of the day, by counting periods of 10 minutes. In the second approach counting was performed for 30 minutes on six time intervals, identified by inquiries to the nearby population and by a 24 hour noise measurement. The air conditioning machines were modelled using the Portuguese norm, NP EN ISO 3744. Correlation results taken from the two previous approaches and the noise measurements used to validate the Cadna/A model showed values of 0.87 and 0.85. Since they are very similar, one can conclude that both approaches can be used in practice. Taking the economical factor, the second approach is preferable because it takes less time to be performed.
A fast time-domain model for wheel/rail interaction demonstrated for the case of impact forces caused by wheel flats
Authors: Pieringer Astrid , Kropp Wolfgang
Published: May 2008

The prediction of impact forces caused by wheel flats requires the application of time-domain models that are generally more computationally demanding than are frequency-domain models. In this paper, a fast time-domain model is presented to simulate the dynamic interaction between wheel and rail, taking into account the non-linear processes in the contact zone. Track and wheel are described as linear systems using impulse-response functions that can be precalculated. The contact zone is modelled by non-linear contact springs, allowing for loss of contact. This general model enables the calculation of the vertical contact forces generated by any kind of roughness excitation between wheel and rail. Here, the model is adapted to the excitation caused by wheel flats by introducing the irregular wheel shape as a form of extreme roughness. A brief parameter study is presented to demonstrate the functioning of the model. The results from the model are discussed and compared with results from literature.
Testing a new rail roughness measurement standard
Authors: Jones Chris J. , Létourneaux Fabien , Fodiman Pascal
Published: May 2008

Railway rolling noise arises from the combined roughness of the wheel and rail surfaces. The rail roughness is therefore an important parameter in the assessment of train pass-by noise. The Technical Specifications for Interoperability (TSI's) in Europe require noise to be measured on a 'reference track' the conditions of which are controlled. A spectral limit for the rail roughness is a major part of that control. The TSIs needed a new standard for rail roughness measurement so the CEN commissioned TC 256 Working Group 3 to draft one. The final draft of the new standard is now complete and will soon be published. This paper describes a 'road test' that was part of the standard development process. This test involved asking eight teams from all over Europe with seven different instruments to measure roughness at the same site, independently making their own interpretation of the standard. The paper outlines the aims of the new standard and describes the road test. It presents results and conclusions of the test that have been used already to improve the standard. Consideration had to be made of how rail-head defects are treated and how different measurement technologies are used.
Uncertainties and repeatability of the Reception Plate Method
Authors: De Geetere Lieven , Ingelaere Bart , Schevenels Pieter
Published: May 2008

The Reception Plate Method (RPM) as proposed by CEN/TC126/WG7 in prEN 15657-1 estimates the structure-borne sound power injected from a (high mobility) vibrating source into a (low mobility) building structure. In the near future, a round-robin test is planned to investigate repeatability and reproducibility issues of the RPM. As a preparation of this round-robin, uncertainties of the RPM are studied using the standard ISO tapping machine, placed on a 4 feet table on a reception plate. The injected power into the reception plate is calculated using different methods. The influence of the source position, accelerometer positions and airborne excitation are investigated, together with repeatability tests. Also, differences in injected power between two different brands of the ISO tapping machine will be studied. Finally, in-situ installed structure-borne sound power level will be predicted using prEN 12354-5 and compared to measurements on a simple building structure.
Building Isolation Design for Noise Critical Applications
Authors: Wilson George P.
Published: May 2008

Because it is a complex, multi-degree-of-freedom system, the success of a building isolation installation depends on careful selection of a number of design factors. The new Toronto Opera House, the Four Seasons Centre for the Performing Arts, opened in June 2006, is located directly adjacent to a surface light rail trackway and to a subway rail transit system. The results characterized as "the quietest Opera House in the world" demonstrate that groundborne noise and vibration is not a factor precluding the use of a noisy site for a noise-sensitive facility. Measurement of the existing groundborne noise provided the basis to determine the required noise reduction. Very stiff and massive foundation elements with stiff and massive structure directly above the isolation bearings allows the isolation design to be simplified to a single-degree-of-freedom system for deriving the performance of the isolation at low frequencies. Natural rubber bearings with thickness adjusted to achieve a specific amount of insertion loss for the structure-borne noise can be used to determine the expected performance at frequencies above 50-80 Hz. Isolation system design parameters for the new 2000-seat Opera House Performance Hall and graphical results from vibration and noise projections and tests are presented.
Rheology and mobility in a sono-fluidized granular packing
Authors: Clement Eric , Caballero Gabriel , Goldenberg Chay
Published: May 2008

Dynamics near jamming (glassy phase, aging, memory effects and intermittency) shows amazing analogies among a variety of very different systems (colloids, dense suspensions, foams, granular materials). Recently, several proposals have emerged with the aim of describing in a general and unified way this behavior. With the purpose of testing experimentally some of these ideas, we performed several experimental studies on dry granular materials under vibration. We found that even with a weak level of vibration, such as sound injection, the behavior of granular matter is changed dramatically. We directly observe that the grains undergo a sub diffusive collective dynamics on a very long time scale which results on global compaction effects. In this regime, we have studied the rheology of an intruder moving in the bulk as a function of the level of energy injected, the driving velocity and the shape of the moving object. We also present a simple model to account for the observed behavior.
Elastic waves in one-dimensional unconsolidated medium with Hertz nonlinearity
Authors: Korobov Alexandr I. , Izosimova Maria Y. , Brazhkin Yurii A. , Sovetskaya Elizaveta
Published: May 2008

Results of experimental study of elastic longitudinal harmonic wave's propagation in one-dimensional unconsolidated medium are presented. A 1-D chain of identical pre-pressed beads is used as an experimental model. To describe elastic properties of such medium the Hertz model is used. Presence of periodical structure causes elastic waves to be dispersive in such medium and to have a cutoff frequency. A cutoff frequency depends not only on material's elastic properties and beads' geometrical sizes but also on pre-press value. Velocity dependence on frequency of longitudinal harmonic wave of small magnitude is measured experimentally, and dispersion curves are built under different pre-press value. Pre-press value is regulated with applied external static force along chain axis. Measured dispersion dependences are in good agreement with theoretically calculated ones. Dispersion impedes observation of higher harmonics generation in such chain. Therefore to study nonlinear properties of 1-D structure, velocity dependence on longitudinal wave amplitude were investigated. The wave velocity depends not only on its magnitude but also on pre-press value on beads. It was experimentally shown the one-dimensional chain of elastic beads is a medium with dispersion, linear and nonlinear properties to be controlled with the applied external static force. Work supported by RFBR.
Localization of sound in a three-dimensional elastic network
Authors: Page John H. , Hu Hefei , Strybulevych Anatoliy , Skipetrov Sergey , Van Tiggelen Bart
Published: May 2008

A long standing question in physical acoustics has been whether or not the Anderson localization of sound can be demonstrated unambiguously in three dimensions. Here we address this question by reporting evidence for the localization of ultrasonic waves in a three-dimensional granular network of weakly sintered aluminum beads. In the upper part of the intermediate frequency regime, where the ultrasonic wavelength is comparable with the sizes of the pores and beads, the intensity time-of-flight profile of the multiply scattered waves exhibits non-exponential decay, which may be construed as a slowing down of the diffusion coefficient with propagation time and is consistent with predictions for localized waves. We use a quasi point source and detector to demonstrate how localization cuts off the transverse spreading of the multiply scattered waves, an effect, which we call 3D transverse localization, that has not been observed previously for any type of wave. These results are interpreted using recent theoretical predictions based on the self-consistent theory of the dynamics of localization, allowing the localization length to be determined. Further evidence is obtained from intensity statistics, which reveal a Thouless conductance g less than unity. These results unambiguously demonstrate the localization of sound in this system.
2D-ultrasonic tomography using first-order Born and canonical approximations
Authors: Lasaygues Philippe , Le Marrec Loic , Scotti Thierry
Published: May 2008

This paper deals with the two-dimensional image reconstruction of an elastic tubes using ultrasonic tomographic method based on first-Born approximation and a canonical approximations. The latter improvement makes it possible to extend the scope of tomography from lower impedance contrast media to higher impedance contrast situations, even when the ultrasonic propagation is greatly perturbed by the difference in acoustic impedance between the scatterer and the surrounding medium. The strategy used to solve this problem was based on comparisons between the experimental diffracted field and the canonical solution approached as a forward problem. The algorithm adopted, using the analytical solution to the local forward problem and an iterative process to recover the unknowns, is fast enough to yield real-time information about the shape. A single frequency does not suffice to determine the real solution as the global minimum of the cost function, and the inversion is improved by using all the frequencies present in the broadband of the transducers. The method presented is robust and is not perturbed by the experimental measurements or small errors in the material properties. The results are most promising. This method gives an image with an error, which is lower than the wavelength.
Light interaction with leaky acoustic wave radiation in YX-LiTaO3
Authors: Kazdailis Paulius , Rimeika Romualdas , Ciplys Daumantas
Published: May 2008

The theoretical model and experimental studies of 633 nm laser light interaction with radiation from leaky surface acoustic waves (LSAW) at various frequencies in YX-lithium tantalate (LiTaO3) are presented. The acousto-optic diffraction with and without polarization rotation has been observed. The values of BAW propagation angle and of the corresponding velocity have been calculated and compared to the ones extracted from the experiment. The differences of the light diffraction process in YX-lithium tantalate from the one in ZX-lithium niobate have been pointed. The potential of the described acousto-optic interaction for applications in light control devices and acoustic wave probing has been demonstrated.
Short access time acousto-optic deflector based on two cascaded Paratellurite devices
Authors: Ouail Nabil , Kastelik Jean-Claude , Pommeray Michel , Dupont Samuel
Published: May 2008

Acousto-optic deflectors (AODs) are used in many applications requiring optical scanning devices with various specifications regarding access time, resolution and wavelength. High time-bandwidth products can be achieved with AODs made in a tellurium dioxide (TeO2) crystal. As paratellurite crystals are available with relatively large dimensions, the time-bandwidth product can be increased by enlarging the optical aperture. However, the access time is increased which is not suitable for random access scanning mode. A new laser scanning system is then presented based on two wide-band paratellurite acousto-optic deflectors. Anisotropic interactions take place under two different tangential phase matching (TPM) configurations in such a way that the acousto-optic bandwidths add up. The optical arrangement of the two cascaded AODs is detailed. The feasibility of such a cascade deflection system has been demonstrated for the green wavelength λ= 514 nm of an argon laser. The total frequency bandwidth is Δft = 100 MHz, equally distributed between the two acousto-optic deflectors. The total angular scan at the output is Δθt = 4.5 ° leading to more than 120 resolvable spots for a 1 mm truncated Gaussian beam and a short access time (as low as 1.5 μs).
Practical analysis of the influence of basic meteorological phenomena on the long-term noise level
Authors: Lebiedowska Barbara Joanna
Published: May 2008

Current regulations on the prognosis of the acoustic climate outdoors require that meteorological conditions should be examined as part of long-term noise level calculations. The impact of meteorological conditions on the noise level was analysed using simulation calculations performed with NMPB-96 method and Mithra software. Their aim was to determine the relationship between the value of these influences and the distance between the receiver point and the noise source and its height above the ground.The distance between a source and the built-up area varied. A number of its locations in relation to the built-up area ranging between 200m and 4 000 m were considered. The built-up area consisted of a row of 11-storey buildings ca. 600 m long. The ground floor height and the floor height were accepted to be 3.5 m and 3.0 m, respectively. Calculations were performed for various meteorological conditions: from P=0 (homogenous conditions) to P=1.0, increasing by every 0.1. The receiver point was located 2 m away from the façade at varying heights: from the lowest point positioned at 5 m to the highest point at 27.5 m, increasing by 2.5 m, which corresponds to the median position of each successive storey, from first floor to tenth floor.
Investigation of the limp model validity for porous materials
Authors: Doutres Olivier , Dauchez Nicolas , Genevaux Jean Michel , Dazel Olivier
Published: May 2008

A new criterion to test the validity of using the limp model for porous materials is proposed. The limp model is derived from the poroelastic Biot model assuming that the frame has no bulk stiffness. Being an equivalent fluid model accounting for the motion of the frame, it has fewer limitations than the usual equivalent fluid model assuming a rigid frame. A criterion is derived to identify the porous materials for which the limp model can be used. This criterion relies on a new parameter, the Frame Stiffness Influence (FSI) based on porous material properties. The critical values of FSI under which the limp model can be used, are determined using a 1D analytical modeling for three boundary sets: absorption of a porous layer backed by a rigid wall, radiation of a vibrating plate covered by a porous layer and transmission loss of a double leaf panel filled in by a porous layer. Compared with other criteria, the criterion associated with FSI provides information in a wider frequency range and can be used for configurations which include vibrating plates.
Absorption and dispersion of acoustical waves in synthetic and natural compressed fibrous materials
Authors: Castagnede Bernard R. , Brouard Bruno , Depollier Claude , Dazel Olivier , Lafarge Denis
Published: May 2008

When a fibrous slab is compressed along its thickness, there are some changes in the basic physical parameters which describe the propagation of sound waves. For instance during compression, the acoustical resistivity and the tortuosity increase, while at the same time the porosity as well as the viscous and thermal characteristic lengths diminish. For a 1-D compression along the thickness of the porous layer, these changes are decribed by straightforward linear equations, as long as the compression ratio is kept small (e.g. between 1 and 5). Such simple expressions are derived theoretically on the base of conservation principles relying on some fundamental metrology indicators. Next, the influence of these changes on the 5 fundamental physical properties of any porous networks are studied numerically on the dispersion and attenuation curves versus frequency, in the frame of the "equivalent-fluid" model [4]. Finally, experiments are performed in order to check some of these predictions on various felt fibrous materials having different compression ratio.
Laser-Ultrasonic Measurement of Stress in Metal
Authors: Podolsky Aleksei , Koshkin Vladimir , Bel'Ko Viktor , Fetisov Andrei , Karabutov Alexander
Published: May 2008

Stress in metal was investigated by acousto-elastic effect. The dependence of longitudinal ultrasonic wave velocity on transverse stress was considered. A laser-ultrasonic defectoscope was used for precise ultrasonic velocity measurement. Optoacoustic transducer provides laser excitation and piezoelectric wide-band detection of ultrasonic pulse. The accuracy of the measurement exceeded 0.1% for 2 mm thick metal sample. Samples in the form of plates with the thickness of 2 to 4 mm made of aluminum and titanium alloys and stainless steel were tested. The samples were loaded quasistatically, the load was changing from zero to yield point stress. Load, deformation and velocity of ultrasound were measured. It is shown that the velocity changes significantly with the load. Some features of the velocity change under tensile stress are presented. The possibility of the local residual stress measurement with the laser-ultrasonic technology is discussed.
Generation and Evolution of Cavitation in Magma under Decompression Waves
Authors: Kedrinskiy Valeriy K. , Davydov Maxim N.
Published: May 2008

It's considered that presence of the dissolved water (with concentration up to 5-7 % (wt.)) and viscosity of magma play one of the key roles in volcanic processes. According to the geophysical data, both a character and a structure of explosive volcano eruptions are defined by dynamics of cavitation development and the viscosity increasing orders during the diffusion of the dissolved gas from magma in bubbles. This paper represents a full system of the equations, including the kinetics of phase transitions, which allows us to describe dynamics of a magma melt state in a gravity field behind the front of a decompression wave. The problem is solved numerically, using a known expression for the nucleation frequency as a function of current concentration of gas dissolved in magmatic melt. The notion of diffusion zones which arise around cavitation nuclei is introduced. The latter allow us to define real density of cavitation kernels generated in an unit of magmatic melt volume as a result of phase transitions behind a rarefaction-wave front. The dynamics of the size distribution of cavitation bubbles along a magma-melt column (1km height) and also of the magma viscosity changing dynamically vs. a concentration of dissolved water are investigated. (RFBR 06-01-00317a financial support).
Ultrasonic cleaning of submerged membranes for drinking water applications
Authors: Lauterborn Sonja , Urban Wilhelm
Published: May 2008

Ultrasonic cleaning of membranes used in water purification and waste water treatment is under investigation for avoiding fouling and scaling on the membranes. So far chemicals are used, but their use is under scrutinity for safety, waste removal and health issues. Chemicals often even do not solve the cleaning problem durably. For applications in the part of drinking water treatment it is necessary to ensure the filtered water is really clean. Therefore in the presented experiment the outflow is constantly controlled by turbidity measurements and by using a particle counter in an online system. A pilot plant for sonication of submerged membranes to produce drinking water from surface water was constructed and placed at the Rhine water works in Biebesheim. It could be shown that sonication with 130 kHz when backflushing the membranes only works with following air overflow. Then the permeability keeps high. No damage of the membranes occurs like often has been found in former studies. Only 30 seconds of sonication after 30 min of filtration are enough to keep high performance of the membranes. Thus energy demand is low, which is a pre-condition for an economical use in technical applications.