bluuebunny/crossref_metadata_2025 huggingface dataset:
Using the MBES for classification of riverbed sediments
Authors: Amiri-Simkooei Alireza , Snellen Mirjam , Simons Dick G.
Published: May 2008

For keeping the Dutch rivers suitable for commercial activities measures are required. For example, the bottom of the river Waal, connecting Rotterdam with German industrial areas, is subsiding. Since the subsidence varies along the river, dangerous shoals occur. Sediment suppletions are planned to counteract the subsidence. Appropriate suppletion material is expected to keep the bottom more stable. To monitor the suppletion effectiveness, multibeam-echosounder (MBES) measurements are planned, allowing for simultaneous estimation of bathymetry and sediment composition. For the latter, we apply a method employing the MBES backscatter data. It estimates the number of sediment types present in the survey area and discriminates between them by applying the Bayes decision rule for multiple hypotheses, implicitly accounting for the backscatter strength ping-to-ping variability. The method's applicability was demonstrated in a well-surveyed test area (North Sea). In 2007, MBES measurements were acquired at the Waal, accompanied with extensive sediment grabbing. Contrary to the test area, water depths are very shallow and significant bottom slopes exist, requiring corrections. The lower water depths correspond to smaller beam-footprints, resulting in a higher ping-to-ping variability. Consequently the discriminating power between sediments will decrease. The performance of the classification method for this river environment is assessed.
Emergence of the deterministic Green's function from thermal noise in inhomogeneous solids and fluid-solid structures
Authors: Godin Oleg A.
Published: May 2008

S. M. Rytov [A Theory of Electrical Fluctuations and Thermal Radiation (USSR Academy of Sciences, Moscow, 1953)] was apparently the first to establish theoretically a simple relation between deterministic Green's function and cross-correlation of fluctuations of wave fields generated by random sources. He used reciprocity considerations to analyze fluctuations of electromagnetic fields. An acoustic counterpart of the Rytov's approach was applied in [O. A. Godin, Emergence of the acoustic Green's function from thermal noise, J. Acoust. Soc. Am. 121, EL96-EL102 (2007)] to derive exact and asymptotic relations between acoustic Green's functions and cross-correlation of thermal noise in inhomogeneous moving or motionless fluids. In this paper, these results are extended to solid and fluid-solid media and compared to experimental and theoretical results previously reported in the literature. It is shown that, with the averaging time being sufficiently large, the two-point correlation function of thermal noise contains as much information about the environment as can be obtained acoustically by placing transceivers at the two points. A possibility of retrieving parameters of a fluid motion, such as a flow in a pipe or an oceanic current, from cross-correlations of diffuse noise fields is addressed.
Present state and future trends in ultrasonic characterization of bone
Authors: Laugier Pascal
Published: May 2008

Although it has been over 20 years since the first recorded use of a quantitative ultrasound (QUS) technology to predict bone fragility, the field has not yet reached its maturity. QUS have the potential to predict fracture risk in a number of clinical circumstances and has the advantages of being non-ionizing, inexpensive, portable, highly acceptable to patients and repeatable. However, the wide dissemination of QUS in clinical practice is still limited and suffering form the absence of clinical consensus on how to integrate QUS technologies in bone densitometry armamentarium. There are a number of critical issues that need to be addressed in order to develop the role of QUS within rheumatology. These include issues of technologies adapted to measure the central skeleton, data acquisition and signal processing procedures to reveal bone properties beyond bone mineral quantity and elucidation of the complex interaction between ultrasound and bone structure. In this presentation, we review recent developments to assess bone mechanical properties. We conclude with suggestions of future lines and trends in technology challenges and research areas such as new acquisition modes, advanced signal processing techniques, and models.
Estimation of femoral bone density from trabecular direct wave and cortical guided wave ultrasound velocities measured at the proximal femur in vivo
Authors: Barkmann Reinhard , Dencks Stefanie , Bremer Alexander , Laugier Pascal , Padilla Frederic , Brixen Kim , Ryg Jesper , Glüer Claus C.
Published: May 2008

Bone mineral density (BMD) of the proximal femur is a predictor of hip fracture risk. We developed a Quantitative Ultrasound (QUS) scanner for measurements at this site with similar performance (FemUS). In this study we tested if ultrasound velocities of direct waves through trabecular bone and of guided waves through cortical bone could be used to estimate BMD. In two centres, Kiel and Odense, we measured time-of-flight (TOF) of waves through the trabecular greater trochanter and cortical intertrochanter as well as a wave through soft tissue only. TOF was adjusted for leg width using ultrasound echoes reflected from the skin of the leg to yield speed-of-sound (SOS) of different wave components. Data were cross-calibrated and pooled (62 women). Bivariate correlations and a multivariate model were calculated for the estimation of femur BMD. BMD correlated both with trabecular and cortical SOS but not soft tissue SOS. Coefficient of determination, percentage residual error (RMSE) and level of significance (p) were R2=0.51, RMSE=12.6%, p<0.0001 for trabecular and R2=0.53, RMSE=12.3%, p<0.0001 for cortical measurements. The combination of trabecular, cortical and soft tissue SOS improved the correlation to R2=0.69, RMSE=10.4%, p<0.0001. Multiwave ultrasound methods allow estimation of femoral BMD with a low residual error.
Two-dimensional simulation of circumferential wave propagation in cortical bone at the femoral neck: sensitivity to bone geometry
Authors: Grondin Julien , Grimal Quentin , Laugier Pascal
Published: May 2008

Assessment of bone status using ultrasound techniques has proved to be efficient to quantify the risk of osteoporotic fracture. A prototype scanner is currently developed (European FEMUS project) to assess bone quality at the hip. Circumferential waves in femoral neck cortical bone are expected to propagate in the prototype configuration. In this work, the relationships between time of flight (TOF) of circumferential waves and femoral neck cross-section geometrical parameters were investigated. Two-dimensional finite-difference time-domain simulations of through transmission propagation of a plane wave at 0.5 MHz central frequency were performed on eight femoral neck cross-section models reconstructed from X-ray computed tomography data of one human femur. An ellipse with major radius (a) and minor radius (b) was fitted on the external circumference of each cross-section. The TOF was highly correlated to the ellipticity a/b (R = -0.9607, p<10-3) and to the area delineated by the endosteal surface (R = -0.9717, p<10-4). These results indicate that the TOF is sensitive to the shape of the femoral neck cross-section. This is interesting insofar as previous studies highlighted the importance of the relationships between geometrical parameters and bone strength. In future works, these 2-D results will be challenged in 3-D configurations.
Ultrasonic wave properties in the bone axis direction of bovine cortical bone
Authors: Yamamoto Kazufumi , Yaoi Yuichiro , Yamato Yu , Yanagitani Takahiro , Koizumi Takaaki , Matsukawa Mami , Yamazaki Kaoru , Nagano Akira
Published: May 2008

Quantitative ultrasound (QUS) is a good method to measure elastic properties of bone (one indicator of bone quality) in vivo. Bovine cortical bone has two typical microstructures, plexiform and Haversian. In the nanoscopic level, bone consists of calcium phosphate, which forms incomplete hydroxyapatite (HAp) crystal. The preferred orientation of c-axis of HAp crystallites induces anisotropy and inhomogeneity of elastic properties in bone. In this study, relationship between speed of sound (SOS) and HAp crystallites orientation in the axial direction were investigated in two foreign age bovine cortical bones. The dependence of attenuation on the anatomical position was also investigated. Two ring shaped cortical bone samples were made from 36 and 24-month-old bovine femur. SOS was measured by a conventional ultrasonic pulse system, using self-made PVDF transducers. The integrated intensity of (0002) peak obtained using X-ray diffraction was estimated to evaluate the amount of preferred orientation. Regardless of age, a significant correlation between SOS and preferred orientation of HAp crystallite was observed in the parts of the plexiform structure, and gradient of the relation showed a similar tendency. Attenuation seemed to strongly depend on bone microstructure because of its porosity.
Anisotropy of ultrasonic longitudinal wave in the cortical bone of bovine femur
Authors: Yaoi Yuichiro , Yamamoto Kazufumi , Koizumi Takaaki , Matsukawa Mami , Yamazaki Kaoru , Nagano Akira
Published: May 2008

Quantitative ultrasound (QUS) is a good method to measure elastic properties of bone. It is known that the mammalian cortical bone shows strong anisotropy and inhomogeneity. We have investigated the distribution of ultrasonic longitudinal wave properties in bovine femur, considering the structure in the nanoscopic level [Yamato et al. Calcified Tissue International, Accepted]. In this study, the anisotropy in the axial-tangential plane of bovine cortical bone is experimentally investigated using an ultrasonic pulse technique. The ultrasonic pulse measurement was performed using a PVDF focus transmitter (Custom made, Toray) and a self-made flat PVDF receiver. Three ring-shaped cortical bone samples were made from a 32-month-old bovine femur. Four cylindrical specimens were taken from one ring-shaped cortical bone sample along the radial direction. The anisotropy of speed was investigated by rotating the specimens. We found that directivities of ultrasonic longitudinal wave in these specimens were similar. In addition, the direction of the fastest wave speed was a little different from the bone axis. The results indicate the complicated anisotropy of the cortical bone.
Diffuse ultrasonic backscatter from cortical bone
Authors: Turner Joseph A. , Ghoshal Goutam
Published: May 2008

Diffuse ultrasonic backscatter techniques have been used primarily for characterization of microstructure in structural materials such as polycrystalline metals. Such measurements exploit the spatial variance of the signals from a modified pulse-echo technique. In this presentation, experiments are discussed using this technique on samples of porcine cortical bone at center frequencies of 15, 20, and 25 MHz. The time domain results obtained are analyzed with respect to a single-scattering model that includes statistical information about the microstructure. In addition, the model includes a rigorous description of the transducer beam pattern as it interacts with the liquid-sample. These results provide information regarding the ability of single-scattering models to capture the ultrasound propagation in such materials.
Measurement of the tortuosity and the viscous characteristic length of human cancellous bone via transmitted waves
Authors: Sebaa Naima , Boeckx Laurens , Fellah Zine , Naas Mouna , Goossens Tom L. , Boonen Steven , Van Der Perre Georges , Leclaire Philippe , Depollier Claude , Lauriks Walter
Published: May 2008

For a few years several authors have proposed the model of Biot to describe the ultrasonic wave propagation in cancellous bone. One drawback of this model is the number of parameters which it needs. Two significant parameters to describe the geometry of the trabeculae are tortuosity and viscous characteristics length. In this communication, we propose two methods to measure these parameters. The first method consists in estimating these two parameters by inversion from the transmission coefficient. In the second method, we get the tortuosity from direct measurement using the focused transducers. The scan of a layer of cancellous bone shows a good correlation between direct measurements and the results of the inversion.
Simulation and modeling of a new quantitative ultrasound imaging device using cylindrical crossed beam forming arrays
Authors: Haupert Sylvain , Reguieg Djelloul , Padilla Frederic , Defontaine Marielle , Laugier Pascal
Published: May 2008

Real-time quantitative ultrasound imaging (QUI) produces images of bone properties with the advantages of being non-ionizing, portable and repeatable. A real-time QUI technique has been proposed, based on two 2-D arrays (24x24 transducer elements) to produce a confocal spherical focusing in transmit and receive modes. However, the electronics to manage beam scanning and focusing is complex and remains expensive. To overcome these disadvantages, a new device has been developed, based on two 1-D transducer arrays (72x1 transducer elements) and confocal cylindrical crossed-beam forming. The intersection of two orthogonal cylindrical focus lines replaces the spherical focused beams. Initial results obtained with this approach showed a distortion and a shift of the spectrum in the low frequency range compared to the reference confocal spherical focusing technique. The aim of the study was to explain the observed differences between spherical and cylindrical focusing techniques using numerical simulations of elementary impulse responses calculated in the confocal and reception planes. The orthogonal configuration of the transmit and receive focusing line results in orthogonal curvatures of the transmitted wavefront and receiving aperture, with summation by the receiving aperture of an out-of-phase wavefront. We show that this effect is the major source for the frequency response artifacts.
Investigation of effect of trabecular microstructure on ultrasound propagation through cancellous bone using finite-difference time-domain simulations
Authors: Hosokawa Atsushi
Published: May 2008

Using finite-difference time-domain (FDTD) numerical simulations, it was investigated how the trabecular microstructure could affect the propagation of ultrasound waves through cancellous bone. Three-dimensional (3D) numerical models of cancellous bone were reconstructed from 3D micro-computed tomography images of bovine femoral bone with oriented trabecular structure. In these models, the trabecular elements were eroded to increase porosity using an image processing technique. Three erosion procedures were given to realize different changes in the trabecular microstructure with increasing porosity. FDTD simulations of the ultrasound pulse waves propagating through the cancellous bone models were performed in two cases of the propagations parallel and perpendicular to the main trabecular orientation, and the porosity dependences of the propagation properties, attenuation and propagation speed, were derived for various trabecular changes. It was demonstrated from the simulated results that the propagation properties in both directions parallel and perpendicular to the trabecular orientation could be affected by the trabecular microstructure. In addition, the effects of the major (or plate-like) and minor (or rod-like) trabecular elements on the ultrasound propagation were respectively investigated for both the parallel and perpendicular propagations.
Relationship between QUS parameters and a cellular model- based estimation of bone strength
Authors: Haiat Guillaume , Padilla Frederic , Laugier Pascal
Published: May 2008

The final goal of quantitative ultrasound (QUS) techniques is to assess bone strength. However, the translation of QUS results into bone strength remains elusive because the physical principles of ultrasonic propagation in bone are not fully understood yet. Here, the sensitivity of Broadband Ultrasonic Attenuation and Speed of Sound to variations of bone strength is derived. Therefore, a cellular model is combined to a multiple regression analysis resulting from the analysis of finite-difference time domain (FDTD) simulations coupled with imaging techniques. The variation of QUS variables induced by a variation of strength of 10%, realized either by a change in material properties or a change in bone volume fraction (BV/TV) is investigated. Except when BV/TV is high, the variations of BUA in response to a variation in strength realized by a pure change of BV/TV is higher than the technique imprecision and thus can be detected. When the variation of strength is realized by changes of elastic properties, the response in QUS properties is dominated by the variation in C11 over C44. The interpretation of these data, however, is not straightforward due to sparse description of elastic properties at the tissue level, which is a limitation of the cellular model.
Selective ultrasonic focusing towards an optical contrast agent by use of photoacoustic-guided time-reversal
Authors: Funke Arik R. , Bossy Emmanuel , Aubry Jean-François , Fink Mathias , Boccara Albert-Claude
Published: May 2008

We recently demonstrated experimentally that optically absorbing regions embedded at centimetric depths in an optically diffusive medium can be used, through the photoacoustic effect, as ultrasound sources for time-reversal techniques [Bossy et al., APL 89(18), 2006]. If the optically absorbing region is spatially localized, the emission of the time-reversed photoacoustic waves provides a method to automatically focus ultrasound towards the absorbing region. In biological tissue, this approach has the potential to automatically guide high-intensity focused ultrasound (HIFU) beams towards a targeted region labelled with an optically absorbing contrast agent. However, such an approach is conceivable only if the HIFU beam is guided towards the sole targeted region, and not towards other potentially strong endogenous optical absorbers (such as blood vessels). In this work, we present a method to selectively focus time-reversed photoacoustic waves towards an exogenous wavelength-dependent optical contrast agent. Experiments were performed in vitro on tissue-mimicking phantoms, with nano-particles as contrast agents. A tunable nanosecond pulsed laser was used with different optical wavelengths to generate photoacoustic waves. A multi-channel time-reversal ultrasound system was used to emit ultrasound signals derived from time-reversed photoacoustic signals obtained with different optical wavelengths.
Sound pressure estimation at an electroacoustic transducer's voicing face by way of all-electrical sensing
Authors: Sandoz Florian , Lissek Hervé
Published: May 2008

When it comes to designing active control disposals, sound pressure sensing is usually required. In the framework of active control of acoustic impedance, this work aims at conceiving a digital estimator that processes voltage and current measurement to compute an estimation of the pressure in the vicinity of the diaphragm of an electro-dynamic speaker. After dealing with modeling concerns of the actuator, the bilinear transform is used to obtain equations of two IIR filters. An adaptive identification using the LMS algorithm and a SVD-based identification are tested to compute filters coefficient, both leading to poor experimental results. Accordingly, the actual transfer functions of the speaker are measured and optimal IIR filters are designed using the simulated annealing algorithm. It is then shown that good results can be achieved experimentally when the speaker is loaded electrically by a short circuit or an open circuit. Finally, performances of the process are discussed regarding other operating conditions.
Virtual Prototyping of Electrodynamic Loudspeakers by Utilizing a Finite Element Method
Authors: Lerch Reinhard , Kaltenbacher Manfred , Meiler Martin
Published: May 2008

To speed up the development of electrodynamic loudspeakers, computer tools have to be applied. With appropriate computer simulations, the costly and lengthy fabrication of prototypes, as required within conventional experimental design, can be reduced tremendously. Present computer modeling tools are mainly based on equivalent circuit representations. The main drawback of these models, however, stems from the fact that the circuit element parameters have to be measured on a prototype, first. Therefore, the need for appropriate numerical simulation tools based on finite element method (FEM) arises, since as input parameters they suffice with geometrical and material data. However, present finite element tools suffer from their incompleteness in respect to full field couplings and nonlinear features. In this paper, a new finite element scheme is introduced and its utilization within the computer-aided design of electrodynamic loudspeakers is demonstrated. This scheme allows the precise and efficient calculation of the electromagnetic, mechanical and acoustic fields, including their couplings. Furthermore, nonlinear effects in the mechanical behavior of the spider as well as magnetic nonlinearities due to the nonhomogeneity of the magnetic field are taken into account.
Periodically poled transduction structures built on thinned single crystal Lithium Niobate layers bonded onto Silicon
Authors: Courjon Emilie , Ulliac Gwenn , Hauden Jérôme , Ballandras Sylvain
Published: May 2008

The demand for highly coupled high quality acoustic wave devices has generated a strong innovative activity, yielding the investigation of new excitation principles and wave guide structures. In a recent work, we have investigated the interest of periodically poled transducers (PPTs) on single crystal LiNbO3 Z-cut plates. The PPT simply consists of a periodically poled ferroelectrics layer metallized on its two faces for acoutoelectric excitation. In this work, we have fabricated PPTs on single crystal LiNbO3 Z-cut thinned layers reported on Silicon to develop a new kind of wave guide. Their fabrication is based on a home-made wafer bonding technique based on a metal-metal adhesion, the lithium niobate being lapped and polished in order to obtain a layer exhibiting a few tenth micrometer thick. The corresponding devices have successfully fabricated and tested in the frequency range 100-300 MHz. Comparison between experimental measurements and theoretical analysis (using a combination of finite and boundary element analysis) show that the modes are well controlled and that different kind of wave polarization may be excited.
CMUT membrane model based on theory of stratified plates
Authors: Senegond Nicolas , Teston Franck , Meynier Cyril , Certon Dominique
Published: May 2008

To optimize and characterize capacitive micromachined transducers, static and dynamic mechanical behavior of the membrane have to be considered and modeled. Most of cMUT models are based on the classical plate equation. The flexural rigidity is homogenized for multi-layer structure taking into account properties of each material. Homogenization relations are available provided the flexural plate equation can be separated from the in-plane deformation equation, so-called the membrane-like behavior equation. Practically, for membrane partially covered with electrode, at the metallized/non-metallized discontinuity, these equations cannot be solved separately and homogenization procedure is no more available. Moreover, initial membrane deflection introduces supplementary coupling between in-plane and flexural displacements requiring modification of homogenization relations. A complete analytical formulation of the plate equation is developed in this paper. A finite difference meshing has been used to numerically solve the new set of plate equations. First, a cMUT with simple geometry is modeled for validation and comparison with Finite Element simulation (COMSOL Multiphysics software). Then, the validity domain of the "simple" flexural plate equation is discussed. Finally, an example of membrane optimization is given, where a multi-layer structure is proposed to reduce influence of static pre-stresses in the membrane on collapse voltage and resonance frequency.
Pure-shear mode BAW resonators consisting of (11-20)textured ZnO films
Authors: Yanagitani Takahiko , Masato Kiuchi , Matsukawa Mami , Watanabe Yoshiaki
Published: May 2008

Thickness pure-shear mode film bulk acoustic wave resonators (FBARs) made of (11-20) textured ZnO films have been fabricated. We have also fabricated FBAR structure consisting of two layers of the (11-20) textured ZnO film with opposite polarization directions. This FBAR structure operated in second overtone pure-shear mode, and allowed shear-mode FBARs at higher frequency. The effective electromechanical coupling coefficients keff2 of pure-shear mode FBAR and second overtone pure-shear mode FBAR in this study were found to be 3.3% and 0.8%, respectively. The temperature coefficient of frequency (TCF) of thickness extensional mode FBAR, pure-shear mode FBAR, and second overtone pure-shear mode FBAR were measured in the temperature range of 10-60 °C. TCF values of -63.1 ppm/°C, -34.7 ppm/°C, and -35.6 ppm/°C were found for the thickness extensional mode FBAR, the pure-shear mode FBAR, and the second overtone pure-shear mode FBAR, respectively. These results demonstrated that pure-shear mode ZnO FBARs have more stable temperature characteristics than the conventional thickness extensional mode ZnO FBARs.
Multimode evaluation of cement behind steel pipe
Authors: Froelich Benoit
Published: May 2008

Oil wells are usually cased with a steel pipe, and cement is injected in the annulus between pipe and rock in order to provide hydraulic isolation of the reservoir. The traditional ultrasonic technique to evaluate cement behind steel pipe has been to excite the pipe thickness mode, and to extract the acoustic impedance of the material from the pulse-echo response. However, this technique suffers from some limitations, such as a limited depth of investigation or a poor discrimination between mud and light cement. To alleviate such limitations, the thickness mode can be combined with the pipe flexural mode. Although dispersive, the flexural mode has the unique property of a quasi constant group velocity in a specific frequency domain which is high enough to provide azimuthal resolution. Such property provides the means for an accurate measurement of the time of arrival and the amplitude of the different echoes generated by a particular geometry. In particular, the echo traveling within the annulus and reflected by the rock can be easily detected from within the pipe, and provide novel information on the annulus fill.
Condenser microphone as parametric electroacoustic system and its time-domain modelling via equivalent electrical circuit in SPICE software
Authors: Vlk Michal
Published: May 2008

Condenser microphone usually works with constant polarisation voltage. Where special attentions are prescribed for spectrum of self noise there may be useful to use high frequency voltage (pump) applied to transducer instead of DC charge. When frequency of pump is orders of higher than frequency of acoustic signals, large parametric gain occurs in the transducer. Method for describing such a system via equivalent electric network with approach of electronic filter design blocks was developped and special analogies were used for convergency improvement. Method was applied to time-domain simulation of pressure transducer with current-mode diode discriminator in SPICE computer analysis software. Simulations of transient behavior after switching system on was demonstrated.
Modelling of radiofrequency MEMS bulk acoustic wave resonators with Legendre polynomial method
Authors: Raherison Antoine A. , Ratolojanahary Faniry Emilson F. , Lefebvre Jean-Etienne J. , Elmaimouni Lahoucine L. , Gryba Tadeusz T.
Published: May 2008

Radio-Frequency electro-acoustic resonators and filters are key components for wireless communication devices. The next generation of mobile systems requires for these components a strict size reduction, higher operating frequency and better power resistance. So, MEMS BAW (Bulk Acoustic Wave) devices have emerged as an efficient alternative to established Surface Acoustic Wave filtering solutions. Knowledge of the electromechanical coupling coefficient and the Q-factor are of primary importance for the MEMS BAW device design. In our model, the Legendre polynomial method which describes the structure and incorporates automatically the boundary conditions in constitutive and propagation equations is used to calculate these parameters. It is the first time this method is applied to study standing rather than propagative waves. The advantage of this approach are, in a unique formulation, to take into account the presence of sources, existence of electrodes' losses and dissimilarity of the constituent materials of the resonator. To validate this approach, it is applied to a Al/ZnO/Al resonator. Through harmonic and modal analysis, the influence of electrodes properties on MEMS BAW resonator performances are illustrated; the results are compared with those published earlier. This method is an efficient tool for designing MEMS BAW filter.
Three-Dimensional FDTD Method for Analysing of the acoustic characteristics of Compact Acoustic Reproduction Systems
Authors: Koga Yuichiro
Published: May 2008

We propose a method for analysing of the acoustic characteristics of compact acoustic reproduction systems with Three-Dimensional FDTD method. We reproduce actual structure of compact acoustic reproduction systems and take the frequency characteristic of sound pressure level at a point with Three-Dimensional FDTD method. To compare the frequency characteristic of sound pressure level of actual measurement of compact acoustic reproduction systems to measurement of the proposed method, we show availability of the proposed method for analysing of the acoustic characteristics of compact acoustic reproduction systems. The proposed method could explain actual phenomena on compact acoustic reproduction systems well.
CNAQ: a MATLAB acquisition tool for computing transfer functions over audio cards
Authors: Pellerin Guillaume
Published: May 2008

Since transfer function measurements require very precise buffer management, it is not easy to find any free and/or educational software which processes them with consumer audio cards, cheaper than professional ones but useful. Some people often use musical sequencers to generate and acquire signals but data can't be easily analyzed in other specific engineering codes because the lengths of the samples can't be easily fixed for example. Therefore, we decided to develop a specific software for general audio acoustic measurements with these main constraints: choose a programming language compatible with existing educational and professional tools, promote multi-platform interpreted languages, be able to use consumer audio cards, publish the source code under the terms of a free software license. CNAQ provides a graphical interface under MATLAB to process sweep sine measurements for any kind of acoustical or electronic application in the audio range. The current features of the software and some development ideas, such as implementing convolution based Farina's method, will be also presented.
Perception, verbal description and gestural control of piano timbre
Authors: Traube Caroline , Bernays Michel , Bellemare Madeleine
Published: May 2008

Musical expressivity in virtuosic pianistic performance relies heavily on timbre and performers call upon a vast vocabulary to describe the nature of their sound; examples of adjectives include velvety, metallic, bright, round and dark. The present study aims to determine whether this vocabulary, its perceptual meaning and the gesture applied to obtain the sounds it describes, stand as consensual among pianists. The relations between timbre, articulation, register and dynamics are also examined. Nearly 100 verbal descriptors were collected as well as the description of the associated gestures. Some timbres are specific to certain dynamic levels and others are the result of a combination of at least two sonic elements into one resulting sound object, where articulation, - the relation between one note to the next - plays a crucial role. A subset of these adjectives has been selected for further study. A professional pianist performed, on a computer-controlled recording acoustic piano, three short project-designed pieces with several timbres, as designated by adjectives. The excerpts were also captured with microphones to serve as stimuli for a timbre recognition task, both in free form and by selection, to which a group of 17 pianists performed with great accuracy.
Spherical mapping of violins
Authors: Ravina Enrico , Silvestri Paolo , Montanari Pio , De Vecchi Guido
Published: May 2008

An original experimental approach oriented to the evaluation of the acoustic performances of violins is described. Starting from 14th Century the violins family have passed through significant changing, strongly influencing their sound. The "instrumental music" requires different parts for different voices: the violin family changes its mechanical structure following this requirement. The structural elements are modified in order to adequate the sound to the aesthetic taste of the historical period. Mechanical modifications involve geometry, relative positions and structural characteristics of fixed and mobile parts. The consequence is a significant alteration of vibration and acoustic responses. The paper describes a systematic approach oriented to evaluate the acoustic performances of differently mounted violins (baroque, classical, modern) by means a spherical mapping of the generated sound. A workbench based on a semicircular structure carrying an array of 10 microphones interfaced to a portable acquisition unit, has been designed and realized. The violin, played by the musician in anechoic chamber or in representation room, is located at the centre of this semicircle: changing the relative angular position between the violin and the array acoustic spherical maps describing the actual sound emission are generated. A systematic comparison among differently mounted violins is shown and discussed.
Considering the effect of hammer shank flexibility using a multibody dynamic simulation model of a piano action mechanism with string contact
Authors: Vyasarayani Chandrika P. , Birkett Stephen , McPhee John
Published: May 2008

A piano action mechanism converts a pianist's mechanical input into acceleration of the piano hammer, which impacts the string for tone generation. We present a multibody dynamic model of the mechanism, considering the differences when hammer shank flexibility is included as compared to a rigid shank. The model is developed using the graph theoretic approach and includes the hammer-string interaction. A Rayleigh beam model including complete second order deformation field is used for simulating hammer shank flexibility. The governing partial differential equation is discretized using Ritz approach considering Taylor monomials as assumed modes. A convergence study confirms that two bending modes and one axial mode are sufficient to represent the hammer shank deformation. The vibrating string is modeled using a standard modal analysis procedure. The many contacts between components of the mechanism include significant sliding during contact; for these contacts a modified Hunt-Crossley law is used to represent the normal force, and interface friction is handled using a Cull and Tucker friction model. The results of parametric studies show the effect of hammer head friction on the dynamics of the mechanism during string impact, as well as the influence of hammer shank flexibility on the frequency response of the string.
The physics of the American five-string banjo
Authors: Stephey Laurie , Moore Thomas
Published: May 2008

We report on a systematic study of the American five-string banjo, which was undertaken in an effort to understand the dynamics of this complex instrument. The deflection shapes of the membranic head were studied and catalogued using time-averaged electronic speckle pattern interferometry. The impedance presented to the strings was measured using laser Doppler vibrometry coupled with an integrated force sensor and harmonic driver. Additionally, time resolved spectral analysis of the plucked strings was used to quantify the characteristic decay of the coupled string/membrane system, while time-resolved interferometric studies of the membrane have led to a better understanding of the motion after a string is plucked. All of these investigations help to reveal the importance of the various parameters that affect the sound of this unusual instrument.
The influence of control parameters and physical parameters on reed instruments playing
Authors: Kergomard Jean , Guillemain Philippe , Silva Fabrice , Vergez Christophe
Published: May 2008

An attempt to summarize the influence of both control and physical parameters on production and radiation of sound of reed instruments is given. Some parameters, such as the shape of the resonator, are fixed by the instrument maker, or chosen by the instrumentalist itself: the the reed, and the fixation of the reed on the mouthpiece. These parameters, named physical parameters, are fixed when playing. The second kind of parameters can be totally or partially controlled when playing: the fingering is an obvious one, then the way the reed is pinched by the lip, with an effect on both the reed opening and the reed dynamics, finally the mouth pressure and the shape of the vocal tract. The influence of these parameters is discussed with respect to several attributes of the sound: the various thresholds (normal sound at pianissimo level, extinction at fortissimo level), the control of different regimes, the shape of transients, the playing frequency, the spectrum. The state of present knowledge is given, with emphasis of further research that should be done, and a comparison with the cases of sound controllers and artificial mouth is discussed.
Perceptual effects of radiation control with a multi-louspeaker device
Authors: Misdariis Nicolas , Lang Alexandre , Katz Brian F. , Susini Patrick
Published: May 2008

This study investigates the perceptual issue of acoustical radiation control with the following hypothesis: radiation control can reduce the perceptual gap between a sound coming from an acoustical source (e.g., an instrument) and a sound coming from an electro-acoustical device (e.g., the recording of an instrument played by a loudspeaker). The work is technically supported by a generic multi-loudspeaker device that allows sound reproduction with controlled directivity patterns in a given number of spatial dimensions. The conducted experiment involves two distinct sound corpus: speaking/singing voice (recorded and spatially measured) and a struck plate (synthesized and spatially computed with modeled directivity). Incremental levels of radiation pattern control, in terms of precision of the reproduction, are also considered by combining several diffusion systems and different directivity patterns. Participants are asked to evaluate the stimuli on three semantic differential scales: source width (largeur), distance (distance) and realism (réalisme). The results show a global significant effect of radiation on sound perception: the acoustical/electro-acoustical gap is significantly reduced through radiation control, especially when considering the scales of width and distance. Theoretical principles, technical elements, experimental set-up and overall results will be presented, detailed and discussed during the presentation.
Nonlinear vibrations of impacted rectangular plates. Comparison between numerical simulation and experiments
Authors: Camier Cédric , Arcas Kevin , Bilbao Stefan
Published: May 2008

Large amplitude vibrations of free-edge rectangular plates, subjected to an impulse excitation is addressed. In particular, this work is devoted to the analysis and simulation of a nonlinear von Kármán plate equations and by associate experimental investigations. Time domain simulations are achieved using implicit finite differences (FD) schemes recently developed by Bilbao. These energy-conserving methods guarantee the stability of the algorithm. To compare with simulations results, an experimental setup which allows reproducible impulse excitation and measurements by laser vibrometry has been developed. The time history of the force applied to a rectangular steel plate is recorded and this signal is used as excitation term in the simulations. We perform a parametric study, with both experimental and numerical approaches, by increasing gradually the amplitude of forcing. Non-linear phenomena, such as pitch glide and chaotic behaviour are observed and discussed.
Active control of a vibrating string
Authors: Berdahl Edgar , Niemeyer Guenter , Smith Julius O.
Published: May 2008

We discuss the specifics of applying active feedback control to a vibrating string. Using sensors, actuators, and digital controller hardware, we make the acoustics of the string programmable, yet the string retains its tangible qualities. As a consequence, fretting, bowing, and plucking controlled and uncontrolled strings have similar physical consequences. Consider that any controller emulating a network of springs, masses, and dashpots attached to the string is a passive controller. To allow the string's acoustics to be programmable over a wide range, we should be able to implement passive controllers. This means that there must be at least one linear and collocated sensor/actuator pair. We explain how to construct such a pair in the laboratory. Finally, we explain one controller particular to one-dimensional systems such as vibrating strings. Whenever the sensor detects a pulse arriving, the actuator emits a new pulse. The output spectrum consists of a harmonic series proportional to the sampling of the product of the pulse's Fourier transform and the transfer function from the actuator to the sound recording device. Sound examples are presented. Finally, we discuss an open source environment we have created for adjusting controller parameters in real time from standard computer music software.
Is there a perceptive signature of vehicles vibrations
Authors: Amari Maël , Parizet Etienne , Roussarie Vincent
Published: May 2008

The vibro-acoustic comfort of vehicles running at low speed has been studied for several years by car manufacturers. Even if car passengers are exposed to a complex environment involving sight, hearing and touch, it is generally agreed that vibrations transmitted through the seat is a very significant parameter in such situations. Previous laboratory experimentations revealed that vehicles were strongly discriminated even when subjects were submitted to seat vibrations only. The ranking of vehicles was also identical for different tested roads. All these observations raised the question of the existence of an identifiable signature of vehicles, independent of the road type. A perceptive experiment designed to evaluate the influence of such phenomenon was conducted. Subjects were submitted to a free sorting test. The categorisation task consisted in grouping vibrations stimuli recorded in 9 cars running on 3 differents roads according to their similarity. The RMS level of stimuli was normalised so that its effect was not predominant during the experiment. Results showed that stimuli groups corresponded to the 3 tested roads, and were correlated to time envelopes of vibrations. Vehicles were not significantly discriminated.
Improved perception of sound environments through room acoustic interventions
Authors: Janssen Marc R.
Published: May 2008

Noise in hospitals is apparently among the top complaints of patients, visitors, and staff. An increasing amount of evidence shows the negative effects of sound within health care environments, affecting the quality of care in the end. Very few hospitals have actually been able to characterize hospital noise and to find effective noise control approaches. This paper will show international results of room acoustic interventions on the patients and staff perception of the sound environment. Next to that the suggestions will be presented on the use of relevant acoustical parameters to support the performance and well-being of staff and patients. One specific example will deal with a case study at the Thorax ICU at the Karolinska University Hospital in Stockholm. The purpose of the study has been to clarify how room acoustics in a patient ward affect the staff's perception of the noise situation in that ward. Another purpose has been to develop a better understanding of how a set of requirements for room acoustics should be formulated in order to obtain a supportive health care environment. It is possible to conclude that, by adding more absorption to the room, the noise situation has been positively influenced and perceived.
"Vibration Kills" and other lessons from the trenches
Authors: Amick Hal , Gendreau Michael L.
Published: May 2008

In many areas of acoustics and vibration design, criteria are based upon parameters such as comfort, privacy, intelligibility, productivity, or machine precision. One can approach these criteria with a somewhat dispassionate attitude. However, when working with the biological research communities, one is periodically reminded by the researchers and medical practitioners that much of their work ultimately deals with life-and-death issues, either for patients for whom a drug or medical device is intended, or for organisms used in test protocols. The authors will share a collection of case studies in which these issues are illustrated. These include: Death of cells due to excessive vibration during electrophysiology. Vibration-induced nausea experienced by a surgeon using a surgical microscope for spine surgery. A life-saving medical technology resulting from a serendipitous discovery in a low-vibration lab environment. These case studies highlight the need for care in the specification, design, and construction of biological and biomedical research and healthcare facilities.
Transmissibility of a deformed rotating tyre
Authors: Van Doorn Ruud , Lopez Ines , Van Der Steen René , Roozen N.b. , Nijmeijer Henk
Published: May 2008

The major source of environmental noise exposure is road traffic noise. Of all noise sources, tyre rolling noise is dominant for speeds above 30 km/h for passenger cars. Tyre rolling noise can be subdivided into interior and exterior noise. For the interior noise to which the passengers are exposed to, the tyre transmissibility is essential since it relates the contact forces with the axle forces. These axle forces are responsible for the structure borne interior noise. Here, a Finite Element tyre model, including a fully coupled air column, is used to examine the transmissibility in the frequency domain 0-300 Hz. It is shown that three aspects are essential in modeling the axle forces resulting from tyre-road interaction: 1) the tyre deformation since it leads to a set of non-axisymmetric eigenmodes, 2) the relatively low-damped non-axisymmetric acoustic resonance, and 3) rotation. A methodology using substructuring techniques is presented to include rotational effects both in the case of an undeformed and deformed tyre. These effects of rotation on the transmissibility differ in the deformed and undeformed case: frequency loci veering occurs in the deformed case, while in the undeformed case rotation results in a pure split of the eigenfrequencies.