bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasound contrast agents in an in vivo murine melanoma model
Authors: Tranquart François , Bouakaz Ayache , Serriere Sophie
Published: May 2008

The purpose of the study was to test different types of microbubble contrast agents (SonoVue®, Definity® and targeted microbubbles against vascular endothelial growth factor receptors (KDR, antiCD31)) to quantify angiogenesis. After SonoVue® and Definity® injections, a strong, rapid and heterogeneous signal enhancement was detected in all tumors. According to the tumor size, the quantification of the perfused area revealed major inter-individual variations. Three groups of animals bearing tumors, following SonoVue® administration, were arbitrarily constituted to compare various sonographic parameters such as AUC, mTT, etcœ. The tumoral size increase seemed negatively correlated to a decrease in all quantified parameters. Non linear acoustic signal from microbubbles targeted to the molecular site was determined by an ultrasound-based destruction-reperfusion scheme. In tumor-bearing mice, an increase of the retention time (>10 minutes) was revealed following KDR and antiCD31 targeted microbubbles administrations when compared to the retention time of non targeted microbubbles. The amount of remaining targeted bubbles remains always lower than non specific agents. Results showed that quantitative contrast-enhanced ultrasound imaging could be an effective method for monitoring angiogenesis process in mice and so could be used for the follow-up of tumours under specific treatment.
Violent cavitation from optically configured microbubble pairs
Authors: Campbell Paul A.
Published: May 2008

The mutual interaction between two cavitating microbubbles was investigated using a novel optical trapping arrangement. This approach facilitated development of arbitrary, stable, and initial spatial configurations for two-bubble systems. Critically, exercising optical control over such a binary system can effectively isolate it from resident bubble populations during insonation. This ensures that any early stage dynamical evolution of the system is dominated by the mutual interaction of the two bubbles in view, rather than any extraneous influence arising from 'cross-talk'. In circumstances where the bubbles are located far from a rigid boundary, we observed, using high speed microphotography at framing rates of over 1MHz, that the action of secondary radiation forces leads to mutual bubble attraction often followed by the development of violent microjetting. Microbubble coalescence, with subsequent fragmentation could be observed, and the generation of short-lived anti-bubbles can often occur also. Finally, when cells are present as confluent monolayers on rigid substrates, the statistics for microbubble outcome and dynamics are modified somewhat. I will relate statistics to the parameter space that we interrogated, which included: inter-bubble spacing; relative bubble radii; and individual bubble stand-off parameters.
Frequency dependence of kidney injury induced by contrast-aided diagnostic ultrasound
Authors: Miller Douglas , Dou Chunyan , Wiggins Roger C.
Published: May 2008

Glomerular capillary hemorrhage (GCH) induced in rat kidneys by contrast aided diagnostic ultrasound was examined as a function of ultrasonic frequency. The right kidneys of anesthetized rats mounted in a water bath were exposed to image pulse sequences at 1 s intervals during intravenous infusion of diluted ultrasound contrast agent. Diagnostic ultrasound (DUS) scanners were utilized for exposure at 1.5, 2.5, 3.2, 5.0 and 7.4 MHz. A laboratory exposure system (LES) was used to simulate DUS exposure at 1.0, 1.5, 2.25, 3.5, 5.0 and 7.5 MHz at relatively high peak rarefactional pressure amplitudes (PRPAs). The exposed kidneys were removed and fixed for histology. GCH was measured by counting glomeruli with blood in the urinary (Bowman's) space on histological sections. The percentage of GCH at a fixed exposure frequency showed a rapid rise with PRPA above an apparent threshold. The threshold values were approximately proportional to the ultrasound frequency, with proportionality constants of 0.5 MPa/MHz for DUS and 0.6 MPa/MHz for LES exposures. The increasing thresholds with increasing frequency limited the GCH effect for contrast aided DUS, and no GCH was seen for DUS at 5.0 or 7.4 MHz for the highest available PRPAs.
Exact model of Langevin transducers with internal losses
Authors: Ebenezer D. D. , Nishamol P. A.
Published: May 2008

An exact method is presented to analyze classical Langevin transducers with internal losses. The transducers consist of an axially polarized piezoelectric cylinder sandwiched between two elastic cylinders. All three cylinders are of the same diameter. Exact solutions to the exact equations of motion of the piezoelectric and elastic cylinders and the Gauss electrostatic condition are used. Complex piezoelectric and elastic coefficients are used to model internal losses. For each cylinder, the first set of solutions contains Bessel functions that form a complete set in the radial direction. The second and third sets contain trigonometric functions that form complete sets in the axial direction. They are used to represent fields that are symmetric and anti-symmetric with respect to the plane midway between the ends of the cylinder, respectively. The interface and boundary conditions are satisfied by using the orthogonal properties of the functions. Transducers with identical elastic cylinders at the ends as well as those with a light head mass and a heavy tail mass are analyzed. Numerical results are presented to illustrate the input electrical admittances of transducers. They are compared with those obtained using ATILA - a finite element package for the analysis of sonar transducers.
Advanced Single Crystal Piezoelectric Transducers for Naval Sonar and Medical Ultrasound Applications
Authors: Hackenberger Wesley , Luo Jun , Snook Kevin
Published: May 2008

Single crystal piezoelectrics have received much attention due to their very high piezoelectric and electromechanical coupling coefficients. Naval sonar and medical ultrasound transducers, fabricated from this material, exhibit unprecedented increases in bandwidth, source level, and sensitivity compared to ceramic based devices. In this paper we report many new developments in the growth and manufacture of single crystals. These include increased diameter (> 3") crystal boules, improved compositional uniformity, increased thermal stability, and minimized surface damage. Manufacturing improvements are being applied to a broad range of crystal transducer applications. For navy sonar systems, crystals are resulting in very high bandwidths (> 100%) for transducer sizes that are 1/2 the resonating length and 1/4 the weight of ceramic counterparts with equivalent (or often lower) source level. Manufacturing improvements such as high tensile strength, achieved by precision polishing crystal surfaces, are enabling new transducer operational regimes not possible with ceramic. In particular, single crystal 1-3 composite projectors show promise for achieving high source level in a compact, integrated system designs. Single crystals are also enabling new applications in medical ultrasound including very broadband and extremely high frequency transducers. Further improvements are expected in the near future.
Finite Element Modeling of 2-D Transducer Arrays
Authors: Mestouri Hind , Loussert Alain , Keryer Gilles
Published: May 2008

Active sonar detects objects underwater by sending out sound waves in pulses, scientists could measure the time it takes these pulses to travel through the water, reflect off of an object, and return to the ship. There are a number of factors limiting the performance of low frequency transducer arrays for active sonar systems including the crosstalk and housing interactions which affects the directivity pattern and the sensitivity. Many important issues in transducer arrays design, such as crosstalk, cannot be accurately studied using analytic method due to the complexity of the partial differential equations involved. Finite element method is the only appropriate way to gain more detailed information. In this paper, a 2-D finite element model is constructed to analyze the crosstalk and structure interactions, using ATILA code and GiD graphical interface, of transducer arrays, consists of six active piezoceramic bars, and developed for shallow water use. The directivity pattern strongly depends on the transducer size versus wavelength, each transducer elements interacts directly with its neighbour and indirectly with the other elements, and the radiated acoustic power may considerably vary from one element to another. It is shown that crosstalk and housing interactions can be reduced through the use of different inter-element materials and housing characteristics.
Measurement of Sound Velocity in Water Using Optical Probe and Acoustical Holography
Authors: Ohbuchi Takeshi , Mizutani Koichi , Wakatsuki Naoto , Masuyama Hiroyuki
Published: May 2008

We propose a method for a determination of a three-dimensional sound velocity using optical computerized tomography (O-CT) and near-field acoustical holography (NAH) for measuring a phase object. Ultrasonic waves affect a phase of the light passing through radiated sound fields. The zeroth order diffraction light including sound pressure information is acquired by an avalanche photodiode. Eighteen projections are acquired by rotational scanning, and each projection along the optical axis is obtained by single linear scanning and electronically quadrature-detected as the complex amplitude. The complex sound fields are reconstructed by O-CT in a region of 40 × 40 mm2. Then the sound field on another plane is propagated using NAH from the acquired sound fields, and the sound field on the same plane is reconstructed by O-CT. Comparing the phase of propagated and reconstructed sound fields in wavenumber domain, we can obtain the sound velocity in three dimensional space in a region of 30 × 30 × 10 mm3. The experimental results are in agreement with the reference value measured by another mean.
Influence of a load on the nonlinear behavior of a piezoelectric rod under high sinusoidal voltages
Authors: Parenthoine Denis , Haumesser Lionel , Vander Meulen François , Tran-Hhuu-Hue Louis-Pascal
Published: May 2008

At high levels of excitation, appear, in piezoelectric devices, nonlinear phenomena which can adversely affect the quality of the applications to which they are devoted. It is, in particular, true in non-destructive evaluation, where the generation of harmonics in the ultrasonic tranducer can make inacurrate measurements in materials. In a previous work, third-order constants in a piezoceramic rod of PZT-21 under high sinusoidal electric fields have been evaluted from the analysis of second harmonic generation in the mechanical displacement. All these measurements have been performed under condition of complete free stress. In order to allow a better understanding of the nonlinear behavior of the transducer, various loads, are, now, applied at one end of the piezoceramic rod. Velocity masurements performed by a laser probe at the free end of the active element provides then informations about the nonlinear behavior of the system. Influence of load on the linear and nonlinear behavior of the piezoelectric rod is then studied in the case of an aluminium bar, and in the case of more nonlinear materials. Results are compared both experimentally and theoritically in loaded and unloaded configurations.
Application of contrast optimisation autofocus to flexible ultrasonic arrays for non-destructive testing
Authors: Hunter Alan J. , Drinkwater Bruce W. , Wilcox Paul D.
Published: May 2008

Flexible ultrasonic arrays are used for imaging within objects with complicated geometries for non-destructive testing and evaluation (NDT/NDE), e.g., thick-walled pipes, weld caps, etc. We consider the application of autofocus techniques (routinely used in synthetic aperture sonar (SAS)) to this engineering problem. A flexible ultrasonic array is functionally similar to a wide-beam, stripmap SAS with a single transmitter and receiver. Unfortunately, there are few autofocus algorithms available for this configuration. Popular algorithms, such as echo/image correlation, PGA, DPCA, etc., are better suited for use with a narrow-beam or multiple-receiver SAS. However, contrast optimisation is a more general technique that is well suited to the single transmitter/receiver geometry. In this presentation, we describe our implementation of contrast optimisation autofocus and show experimental results using a flexible array prototype.
An alternative and industrial method using low frequency ultrasound enabling to measure quickly tortuosity and viscous characteristic length
Authors: Fohr François , Parmentier Damien , Castagnede Bernard R. , Henry Michel
Published: May 2008

In the past, several different methods have been proposed in order to determine tortuosity and characteristic lengths, using various physical approaches. For instance, the BET (from S. Brunauer, P. Emmett and E. Teller) method used the adsorption of argon molecules within the surface of the pores to measure thermal characteristic length (or the so-called specific surface). Ultrasonic methods, during the two last decades, were efficiently implemented to measure these parameters, using large frequency bandwidth, different gazes including helium, and varying static pressures. The most standard and well-known method relies on phase spectrum measurements performed over short bursts, by plotting the inverse of the squared velocity as a function of the inverse of the square root of the angular frequency. Unfortunately, this method is quite sensitive on noise during the unwrapping procedure. We here propose a much simplier and efficient method, which is very robust with noisy signals, working at one single frequency, in most cases around 40 kHz. Measurements have been done onto a specific bench developped at CTTM, with some calibrated glass beads, enabling to recover the expected values of the physicalparameters. This method is particularly well suited for industrial and "on line" applications.
A new impedance tube for large frequency band measurement of absorbing materials
Authors: Le Roux Jean Christophe , Dalmont Jean-Pierre , Gazengel Bruno
Published: May 2008

The standard two microphones technique does not allow the measurement of absorbing materials characteristics at low frequency. Moreover, to cover a range from 100 to 6000 Hz two experiments have to be done with two different sample diameters. By using a sensor with a known volume velocity source developed by the LAUM together with the CTTM, it is demonstrated that the impedance can be obtained from 10 to 6000 Hz by performing only one measurement with a single material sample. Results showing the behaviour of some materials at low frequency are presented. On the other hand a comparison is done with classical Kundt tube results.
Does mass matter? Examining a concrete didjeridu
Authors: Amir Noam
Published: May 2008

The influence of wall material on the acoustics of musical wind instruments has been debated widely. While this has been examined for some western instruments, it has been barely touched upon regarding the Australian didjeridu. This is very interesting, considering that didjeridus vary enormously in materials and dimensions. Indeed, musicians and manufacturers alike often have very definite opinions concerning the influence of material type and thickness on instrument quality. As a first step towards examining this issue, we conducted a blind test involving three cylindrical didjeridus of identical internal dimensions: all three shared a basic structure of identical plastic tubing. However, a cement casing was cast on the exterior of one of these, bringing its weight to 17 kilograms. The three instruments were fixed to a stationary wooden frame, then covered so that only the mouthpieces were visible. 32 players of varying expertise were allowed to play each instrument for as long as they wished, and then asked to judge which instrument was different from the other two. Results indicate that the responses were random, regardless of player level. Further research will be necessary to show whether this holds for noncylindrical bores and different internal finishings.
Relationships among subjective assessments and measured physical properties in the didjeridu
Authors: Smith John , Rey Guillaume , Wolfe Joe
Published: May 2008

Traditional didjeridus are unusual and ancient lip-valve instruments with an irregular bore that is largely constructed by termites eating the interiors of small eucalypt trees. This produces instruments with a broad range of bore geometries with many details not immediately apparent to a player. They are therefore well-suited for examining relationships between subjective assessments by players and their measured physical properties. In this study, seven experienced players assessed 38 didjeridus that spanned a wide range of quality, pitch and geometry. A control group of 11 plastic cylindrical pipes were also studied. Eight subjective parameters (backpressure, clarity, resonance, loudness, overtones, vocals, speed, and overall quality) were assessed and the ranking of each instrument correlated with measurements of their geometry and acoustic input impedance spectrum. A strong result of these experiments was the finding that the ranked quality of a didjeridu correlated negatively with the magnitude of its acoustic input impedance, particularly in the frequency range from 1 to 2 kHz. Maxima in the impedance of the player's vocal tract would have a greater effect on instruments with a low impedance, thus favouring the production of the varying spectral peaks or formants in the sound envelope that characterise this instrument.
Design and manufacturing of an artificial marine conch by bore optimisation
Authors: Petiot Jef , Tavard Francois
Published: May 2008

The marine conch is a traditional instrument of the brass family. The resonator is made of the inner shape of the shell, with which the lips of the player interact by the way of a hole pierced in the extremity of the shell. Several notes can be played with this instrument. Unfortunately, the marine conch has become very rare and expensive. In order to build an artificial conch (by injection moulding), we studied the acoustics property of a natural conch. This paper is dedicated to the description of the measurements we made on the conch, and to the presentation of the method used to design the bore. Firstly, the input impedance of the natural conch was measured. Secondly, the size of the bore of the natural conch was assessed by the way of pictures and image processing tools. An initial bore of the artificial conch was designed with a CAD software, by taking into account manufacturing constraints. We developed next an optimisation procedure to improve the harmonicity of the artificial conch. Finally, an artificial conch was next manufactured by rapid prototyping. As a result, we noticed that the artificial conch manufactured can clearly be used as an interesting musical instrument.
A design strategy for brass instruments
Authors: Pyle Robert W.
Published: May 2008

This paper describes the processes being used to design a C trumpet. Since "one size fits all" is not a good approach for high-quality brass instruments, one of the goals is to create a basic design that, with minor variations, can be tailored to meet the needs of a variety of players. There are other goals, secondary to playing quality but nonetheless desirable. These include appearance and mechanical reliability ("fit and finish"), ease of manufacture (consistent quality at minimal possible cost), and ease of repair (accidents will happen, alas!). Existing instruments provide input data to the design process by way of physical dimensions, acoustic input impedance, and players' judgements. Computer modeling helps to predict the effect on intonation of changes of bore contour. Feedback from top professional players is essential to refine the design, especially the "black magic" aspects like brace placement and even the type of solder used to assemble the instrument.
Influence of acoustic waveguides lengths on self-sustained oscillations: Theoretical prediction and experimental validation
Authors: Ruty Nicolas , Pelorson Xavier , Van Hirtum Annemie
Published: May 2008

Human vocal folds and lips of brass instruments players produce self-sustained oscillations due to the interaction between airflow, acoustic waveguides and deformable tissues. This interaction is commonly modelled as a distributed one or two mass-spring system coupled with a simple airflow and acoustic description. This study focuses on the influence of the acoustic waveguide length on the resulting self-sustained oscillation characteristics, i.e. the minimum pressure required to sustain oscillations, the oscillation frequency. Both fixed and varying waveguide lengths are considered. Theoretical predictions with the simplified interaction model are compared to experimental data obtained with a deformable in-vitro replica suitable to produce self-sustained oscillations in presence of an upstream (12, 24 or 32cm) and downstream (varying from 0 up to 235cm) acoustic waveguide. The current study shows the strong influence on the minimum pressure regardless the waveguide length. In addition the waveguide length is shown to impose the resonance frequency for waveguide length superior to 40cm. A rapid change in waveguide length introduces bifurcations between different oscillation regimes.
Motor control in drumming: Influence of movement pattern on contact force and sound characteristics
Authors: Dahl Sofia , Altenmüller Eckart
Published: May 2008

Whereas wind instrumentalists and string players have a continuous control of the acoustic sound parameters during playing, a percussionists' direct contact with the instrument is limited to a few milliseconds. The player has no possibilities to adjust grip or dampening during the actual contact. Whatever timbre and sound level the player is aiming for therefore has to be integrated in the entire striking gesture. How can the player control the complex interaction between drumstick and drumhead? In order to investigate how the players' grip and striking gestures influence the sound characteristics of drum strokes we recorded movements, audio, contact time and contact force during drumming. Different instructions were given with the intention to influence how the player's grip controlling the drumstick. "Normal" strokes were allowed to freely rebound from the drumhead. For "controlled" strokes the player was asked to control the ending position of the drumstick, stopping it as close as possible to the drumhead after the stroke. Preliminary analysis showed that the instructions influenced contact force, contact time, and perceptual ratings of the strokes. Further results and implications will be discussed.
Extraction of lumped clarinet reed model parameters from numerically synthesised sound
Authors: Chatziioannou Vasileios , Van Walstijn Maarten
Published: May 2008

Fluid dynamical analysis and time-domain modelling of a single reed-mouthpiece-lip system can be used to inform the formulation of a lumped model of the woodwind excitation mechanism. Coupling this lumped model to a model of the instrument bore enables computationally efficient generation of sustained oscillations, using a small number of physical parameters that define the instrument and the way the player controls them. As such, the embouchure of the player as well as the geometry of the system is taken into account. In this paper, an attempt is carried out to use the numerically generated sound as an input to an inversion algorithm for the reed-mouthpiece-lip system. Assuming that the reed motion is proportional to the pressure difference across it, a relationship can be established between the pressure and the total flow inside the mouthpiece that allows a first estimation of the physical parameters using standard optimisation techniques. Currently we are undertaking efforts to apply the inversion to data measured under real playing conditions, i.e. effectively capturing player gesture information in the form of physical control parameters.
How to play the first bar of Rhapsody in Blue
Authors: Chen Jer-Ming , Smith John , Wolfe Joe
Published: May 2008

The two-and-a-half octave glissando opening Gershwin's Rhapsody in Blue is one of the great icons of 20th century music and one of the best known bars in music. Expert clarinettists combine unusual fingerings with even more unusual configurations of their vocal tract to achieve a nearly continuous rise in pitch. Using a novel method [1], we incorporated an acoustic impedance measurement head within a clarinet mouthpiece, allowing us to study the player's vocal tract at various stages in the glissando. We measured and compared vocal tract impedance spectra with the corresponding clarinet impedance spectra for the fingering used at that pitch. Partially uncovering an open finger-hole raises the frequency of clarinet impedance peaks in the lower register, thereby allowing smooth increases in the playing pitch. In the upper register, however, resonances in the clarinettist's vocal tract are manipulated to be comparable with those in the clarinet for frequencies in this range. Thus the pitch in the higher section of the glissando is largely controlled by smoothly varying a resonance of the player's vocal tract. [1] Chen, JM. Smith, J. and Wolfe, J., (2008) ''Experienced saxophonists learn to tune their vocal tracts''. Science, (in press).
A study of flute control parameters
Authors: Fabre Benoit , Montgermont Nicolas , De La Cuadra Patricio
Published: May 2008

The sound of musical instruments played in self-sustained oscillations can be interpreted as a sounding transposition of the player's gesture. The playing of wind instruments requires expert control of the blowing that may be difficult to grasp and to measure because it induces only very little motion of the player, as opposed to string or keyboard instruments. In the case of instruments of the flute family, the player seems to control mainly the air jet velocity for mode selection. Flutes in which the air jet is formed between the lips also allow for a control of the total jet flow by the player, through lip adjustments. We present measurements carried on several players, in different playing conditions. The score includes technical exercises such as scales and short musical excerpts from the flute repertoire. Time evolutions of the control parameters are analysed, based on pressure and geometrical measurement, in the framework of the current knowledge on the sound production in flutes, such as jet instability. The control over different parameters will be discussed, both for basic technical exercises and in a musical melodical context.
Acoustical analysis of timbral modulations on the flute as controlled by phonetic gestures
Authors: Lavoie Maryse , Traube Caroline , Breault Marie-Hélène
Published: May 2008

The purpose of this project is to study the control of timbre on the flute by varying articulatory parameters (i.e. embouchure) which correspond to distinct phonetic gestures. The main goal is to compare the production of a specific timbral modulation on the flute and its vocal reproduction (diphthong) by means of acoustical analyses of these sounds. The recordings of timbral modulations performed on the flute (e.g. by increasing the mouth opening) and reproduced vocally as diphthongs (e.g. [u] -> [a] transition) have been analyzed acoustically for intensity as well as for the first two formant trajectories. The results of the formant analyses as presented in an F1-F2 plane reveal the cardinal vowel triangle and confirm a correlation between the flute timbre modulations and the vocal diphthongs corresponding to the underlying phonetic gestures. In addition, a listening test has shown that flutists are able to perceive and recognize these timbral modulations from the sound alone.
Lip control of brass instruments
Authors: Campbell Donald M.
Published: May 2008

Brass instruments are frequently described in the acoustics literature as "lip reed" instruments, emphasising the fact that the sounding mechanism of this instrumental class is flow modulation by the vibration of the player's lips. As well as providing the source of sound, the lips act as the major interface through which the performer controls the intonation, dynamics, articulation and timbre of the performance. Indeed, on instruments such as the natural trumpet and the alphorn, the player's lips form the only control interface. This paper reviews recent studies which have examined the vibrational properties of brass players' lips, the types of motion which they undergo when playing different instruments, and the nature of the interaction between the lips and the instrument. It also considers the extent to which current physical models of the lips are capable of encompassing these control processes.
Vocal tract interactions in saxophone performance
Authors: Chen Jer-Ming , Smith John , Wolfe Joe
Published: May 2008

Although acousticians have debated the importance of the vocal tract in reed instrument performance, expert saxophonists report adjusting their vocal tract for advanced techniques including altissimo playing, subtone playing, bugling and multiphonics. Using a novel method [1], we incorporated an acoustic impedance head within a saxophone mouthpiece to study the vocal tract directly during playing. For fingerings above the first register, the operating peak in the saxophone's input impedance decreases with increasing pitch, falling to below 20 MPa.s.m-3 after 2.7 octaves, thus ending the standard range that is readily available to amateurs. Above this, in the altissimo, professional saxophonists produce peaks in the impedance of their tracts of about 20 to 40 MPa.s.m-3, which they tune to select the desired note. The crossover of the relative magnitudes of saxophone and tract impedance peaks coincides with the transition from standard to altissimo register. While professionals use the vocal tract thus for other extended effects, inexperienced players do not tune their tract resonances and are unable to produce advanced effects. [1] Chen, JM. Smith, J. and Wolfe, J., (2008) ''Experienced saxophonists learn to tune their vocal tracts''. Science, (in press).
Reproducibility of piano playing
Authors: Principeaud Nicolas , Boutillon Xavier
Published: May 2008

Mechanically, piano playing consists in giving to the hammer a certain escapement velocity at a certain time - te, ve - by means of a traditional keyboard and piano action. Numerous replacement systems for the keyboard, action or even for the pianist's finger have been proposed. They implicitly raise the question of the accuracy with which the (te, ve) information must be coded or reconstructed. The precision with which pianists are able to reproduce their playing sheds some light on this question. At this end we have asked several concert pianists to play the same passage several times with the highest reproducibility level they could achieve. The experiment was done on a traditional grand piano equipped with the Yamaha Disklavier system, used as a measurement tool for the escapement velocity of the hammers. The beginnings of a fugue by Bach and a study by Debussy were recorded. Results show that the reproducibility varies highly from note to note and can be as good as approximately 1%. Additional tests on auditors show that deviations on note amplitudes are not perceived unless they reach a level which turns out to be significantly higher than the reproducibility level achieved by the pianists.
A hybrid method for jet noise predictions based on Large Eddy Simulation and Reynolds-Averaged Navier-Stokes simulations
Authors: Bodard Guillaume , Bailly Christophe
Published: May 2008

A hybrid jet noise prediction method combining steady and unsteady flow calculations is discussed. The main objective is to merge advantages of each technique to obtain a robust acoustic prediction tool, which will be able to correctly evaluate design and installation effects such as chevron nozzles or jet-pylon interaction for instance. The low-frequency component of acoustic spectra is computed using large-eddy simulations and the integral formulation derived by Ffowcs-Williams & Hawkings (1969, Phil. Trans. Roy. Soc. Lond., vol. 264). The high-frequency component associated with fine scale turbulence is obtained thanks to Tam & Auriault's mixing noise theory (1999, AIAA Journal, vol. 37) from Reynolds-Averaged Navier-Stokes simulations. The oral presentation will detail the two methods, the LES simulations for subsonic round single and coaxial jets, and the matching between the two approaches to get a complete picture of the acoustic spectra.
Efficiency of optimized microjets on realistic nozzles
Authors: Vuillemin Alexandre
Published: May 2008

Even if chevrons nozzles are an efficient way to reduce jet noise during take off, they also decrease performances during cruise. An innovative way to avoid this decrease is the use of active devices that could be switch off after take off, such as microjets nozzles. Snecma led test campaigns at Martel Facility (LEA/CEAT) to optimize microjets settings (geometric and thermodynamic parameters) and to characterize their efficiency on both 2D axisymmetric and chevrons nozzles. Acoustic and PIV measurements were done on a single stream hot jet with and without external flow, and on a double stream hot jet with pylon.
Recent developments in helicopter rotor noise prediction
Authors: Brentner Kenneth S.
Published: May 2008

Prediction of discrete frequency noise for rotorcraft in steady flight has reached a high level of sophistication and understanding. The primary challenge in such rotor noise predictions is the accurate determination of the loading on and flow field around the blades. Although current rotor noise prediction tools have been demonstrated for steady flight conditions, the utility of rotorcraft comes from their unique ability to hover and maneuver. Such maneuvers often occur near the ground in close proximity to people. This paper describes an initial study to characterize maneuver noise. A maneuver noise prediction system has been developed, which consists of a flight simulation code, free-vortex wake code, and a maneuver noise prediction code, loosely coupled together. One of the key aspects of this system is the ability to investigate the additional noise caused during the transition from one flight state to another. Several maneuvers including turns, accelerations, and pop-up/popdown maneuvers were considered. Significant increases in the low-frequency noise can occur, depending on how aggressive the maneuver is performed. The status of advanced research on predicting acoustic scattering of the rotor noise by the aircraft and the first-principles prediction of rotor broadband noise will also be presented.
Direct Noise Computation in subsonic and transonic flows
Authors: Daude Frédéric , Emmert Thomas , Lafon Philippe , Crouzet Fabien , Bailly Christophe
Published: May 2008

In order to model flow phenomena involving interactions between aerodynamics and acoustics, it is necessary to use Direct Noise Computation (DNC) instead of hybrid methods that are not suitable to take into account the feedback of acoustics on the flow. The methods that are now available in the field of Computational AeroAcoustics (CAA) allows us to deal with DNC in realistic configurations. The numerical code SAFARI (Simulation of Aeroacoustics in Fluids And with Resonance and Interactions) has been developed for this goal. The set of equations are the compressible 3-D Navier-Stokes equations. High order finite difference schemes are used. Multidomain capabilities are implemented in order to deal with complex geometries. Block decomposition is used in order to take advantage of parallel processing on large clusters Validation cases are presented: diffraction by a cylinder, shock tube. Results on realistic configurations are also shown: ducted cavity, transonic sudden enlargment, airfoil interactions.
An Active Network Representation to Predict the Flow Noise Characteristics of Corrugated Ducts
Authors: De Roeck Wim , Solntseva Vasilisa , Desmet Wim
Published: May 2008

In this paper, an active network representation is used to numerically predict and gain more insight in the internally generated flow noise sources in corrugated ducts (the active bi-port component) as well as to describe the acoustic transmission characteristics of this type of application (the passive bi-port components) in the presence of a non-uniform mean flow. For this purpose a numerical approach is chosen, using compressible Large Eddy Simulations (LES) to predict the noise generation mechanisms and Linearized Euler Equations (LEE) with a plane pulse excitation to obtain the transmission characteristics for these components. The accuracy of the active network component determination is increased by separating the aerodynamic and the acoustic fluctuating field of the LES using both an aerodynamic/acoustic splitting technique and multiple plane mode-matching strategies. In this way, a numerical method is proposed to analyze the flow-acoustic behavior of corrugated tubes, which can be generally used for all types of duct system applications.
Aeroacoustic simulation based on linearized Euler equations and stochastic sound source modelling
Authors: Dechipre Hervé , Hartmann Michael , Delfs Jan W. , Ewert Roland
Published: May 2008

In order to continually improve passenger car acoustic comfort, effective methods are needed to simulate the noise generated by external flows as well as the noise produced by duct flows in HVAC systems. The present paper illustrates the use of two methods based on the Linearized Euler equations and derivatives thereof to compute the acoustic field. The two methods implemented in the DLR's aeroacoustic code PIANO are the introduction of a perturbation (vortex) in the flow and the stochastic sound source modelling by Ewert. The application considered by this study is the noise produced by a flat plate in a two-dimensional duct at a thickness related Reynolds number of 1300. Different sizes and edge shapes of the flat plate have been tested. The simulations show a good agreement of the results obtained by the two methods as well as the existence of a vortex street behind the plate corresponding to a Strouhal number of 0.18. It could be shown computationally, that even in the absence of the classical Aeolian tone generation (pure broadband turbulence related trailing edge noise generation) resonance type phenomena occur in the duct. The computed modes for the different configurations show encouraging correlations with the Parker-type modes or resonance phenomena described by Koch.
Service to his fellow men
Authors: McKinley Richard
Published: May 2008

Henning Von Gierke's life of service followed in the footsteps of his family legacy. This presentation will focus on Henning's 50 years of research at the Air Force Research Laboratory at Wright-Patterson Air Force Base, Dayton, Ohio and the recollections of Henning gathered from 20+ hours of video interviews. Henning's life and his research were dedicated to helping mankind. Beginning with his dissertation on noise produced by jet flow and continuing with the accomplishments of his division at the Air Force Research Laboratory his contributions to acoustics were outstanding. His contributions include the Air Force hearing conservation program, the EPA levels document, the BENOX report, the development of Bionics in the 1960's, car airbag research in the 60's, testing of the original 7 US astronauts, human limits of survival for impact, human limits of performance in vibration, pioneering work in hearing protector modeling, bone conduction, and microwave hearing, speech communication, as well as his extensive work in American National Standards and international standards. His contributions have in one way or another affected nearly everyone. He was a great researcher and a great mentor. He will be missed by his colleagues at the Air Force Research Laboratory and around the world.
Dr. Henning von Gierke—My mentor, everyone's mentor
Authors: Schomer Paul
Published: May 2008

Dr. Henning von Gierke was a leading force in acoustics for a majority of the 20th century. He led in human response to noise AND vibration and its assessment. He was a leading force in the US government and in the National Academy of Science (NAS) Committee on Hearing and Bioacoustics (CHABA). He was a leader in hearing assessment and conservation, and in Standards. And to many working in these various areas, he was a mentor, a confidant, and a friend. Mentoring did not stop at the doors of his laboratory, but rather, his mentoring extended to the world. He was a mentor to me in my first years after graduation when we developed the C-weighted procedure for the assessment of large-amplitude impulse noise, and in the development of related Standards and NAS studies. He thrust me into ISO work and CHABA studies, and, later, he chose me to succeed him as ISO delegation chair in acoustics and noise. Not enough can be said about Henning's impact on noise and vibration research and policy in the USA and in the world, and on the expanded reach of Henning's influence through the many like me that he mentored.
Noise source mapping for trucks, Part 2: Experimental results
Authors: Blake William , Plotkin Kenneth J. , Gurovich Yuriy , Donovan Paul
Published: May 2008

The elliptical array described in the previous paper (Part 1) was deployed road-side at a test track for measuring the sound emitted from trucks during passby. Measurements were made on various truck models in various operating states with and without trailers. Extensive spherical-source calibrations confirmed the array's beamforming at both on-normal and steering angles (to 45°); they also disclosed the magnitudes of ground reflection paths for localized sources at different elevations. In all cases, the array output was computationally inverted to produce two-dimensional spatial maps of source levels in the side profile of the truck. In the cases of stationary trucks, the source maps were correlated with simultaneously-obtained intensity maps. Comparisons verified that the array-based source maps for the trucks ranked sound sources of disparate levels in the same order as did the sound power levels deduced from the sound intensity data. Acoustic source maps obtained during truck passbys were then used to provide time-histories and spatial distributions of sources and source paths from the engine, muffler, tires, and certain body components. This project is funded by the National Cooperative Highway Research Program of the Transportation Research Board of the National Academies, USA.
The Milan agglomeration Strategic Noise Map
Authors: Zambon Giovanni , Radaelli Simone
Published: May 2008

The aim of this paper is to describe the procedure used for the Milan agglomeration Strategic Noise Mapping, as defined by Environmental Noise Directive (2002/49/EC). City of Milan is a complex case study because of the presence of a plurality of sources: road traffic, railway traffic (also tram traffic) and aircraft noise (Linate airport). The assessment method is based on the guidelines contained in the "Good Practice Guide for Strategic Noise Mapping and the Production of Associated Data on Noise Exposure" (WG-AEN). The study of noise generated from several sources was carried out with the integrated use of both numerical models and Geographic Information Systems (GIS). Numerical models allow us to estimate of noise levels in large areas near to a specific noise source and GIS enable the efficient acquisition, management and elaboration of geo-referenced data representative of territory, sources and buildings. By means of the study of specific GIS application it was possible to predict the global noise exposure for overall sources, by overlapping the noise maps of the single noise sources.
Budapest Noise Mapping Project I. - Experiences
Authors: Muntag András , Berndt Mihály
Published: May 2008

The Hungarian capital Budapest, and their agglomeration have recently finished their first strategic noise map. According to the Hungarian noise regulations and to the European Directive 2002/49/EC, this is a legal obligation. The main part of the costs was supported by the EU. The preparation of the strategic noise maps based on a computer model and describing the present noise situation of the municipalities, should be seen as the first step to build a true noise information and management system, based on the computer model initially developed. The main parameters of the project were the planned area 1100 qkm, number of dwellings 440 thousand, length of the mapped roads ca. 2000 km This paper based on the experience of 23 municipal noise maps - Budapest and other 22 settlements in the agglomeration. We successfully finished the project on time - the results (all maps) can be found on the internet-page: http://terkep.budapest.hu/website/zajterkep The first paper deals with the technical experiences of the project.
Austrian investigation on the influence of sound leakage in noise reducing devices
Authors: Conter Marco , Haider Manfred
Published: May 2008

Noise barriers are the most widely used means for road traffic noise abatement. Sound absorption and sound insulation are the key properties for noise barrier elements. The standard method of determining these properties by reverberation room measurements has recently been complemented by an in-situ method following CEN/TS 1793-5, also known as Adrienne method. This method allows flexible assessment of the acoustic performance of noise barriers in almost arbitrary places by means of mobile measurement equipment. Using the possibility to perform in-situ measurements the authors have investigated the presence of sound leakage due to structural imperfections which limit the sound insulation performance of noise barriers. This paper summarizes the results of Austrian research on different kinds of barriers regarding the difference in sound insulation between measurements carried out in front of the supporting post (where leakage is likely to occur) and in the middle of the barrier. A statistical correlation of the data was also performed.
A study of twenty-one cases of low-frequency noise complaints
Authors: Pedersen Christian Sejer , Mo/ller Henrik , Persson Waye Kerstin
Published: May 2008

From 203 cases of low-frequency complaints a random selection of twenty-one previously unsolved cases were investigated. The main aim of the investigation was to answer the question whether the annoyance is caused by an external physical sound or by a physically non-existing sound, i.e. low-frequency tinnitus. Noise recordings were made in the homes of the complainants, and the complainants were exposed to these in blind test listening experiments. Furthermore, the low-frequency hearing function of the complainants was investigated, and characteristics of the annoying sound was matched. The results showed that some of the complainants are annoyed by a physical sound (20-180 Hz), while others suffer from low-frequency tinnitus (perceived frequency 40-100 Hz). Physical sound at frequencies below 20 Hz (infrasound) is not responsible for the annoyance - or at all audible - in any of the investigated cases, and none of the complainants has extraordinary hearing sensitivity at low frequencies. For comparable cases of low-frequency noise complaints in general, it is anticipated that physical sound is responsible in a substantial part of the cases, while low-frequency tinnitus is responsible in another substantial part of the cases.