bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of filtering of room impulse responses on room acoustics parameters by using different filter structures
Authors: Huszty Csaba , Bukuli Norbert , Torma Ákos , Augusztinovicz Fülöp
Published: May 2008

Room acoustic evaluation is usually based on post-processing of measured room impulse responses (RIRs), and this often requires some kind of filtering, for instance to derive fractional octave band parameters of a room. In this paper it is shown that the considerable variance of room acoustic parameters of almost any hall is partly caused by the filtering method and the filter properties used in the course of post-processing. The paper proposes new qualification methods and parameters for determining the quality of FIR filter banks, taking their use for acoustic evaluation into account. It suggests practical considerations for the design as well, and shows the analysis and comparison of effects of various filter properties -- such as filter types and topology structures -- on some room acoustics parameters. By using the suggested methods, it is possible to derive more accurate and reliable results in room acoustic evaluation.
Mesoplodon densirostris transmission beam pattern estimated from passive acoustic bottom mounted hydrophones and a DTag recording
Authors: Ward Jessica , Moretti David , Morrissey Ronald P. , Dimarzio Nancy A. , Tyack Peter , Johnson Mark
Published: May 2008

The transmission beam pattern of a female Mesoplodon densirostris tagged on October 23, 2006 in the Tongue of the Ocean, Bahamas is estimated using data from a Woods Hole Oceanographic Institution DTag and simultaneous recordings from broadband, bottom mounted hydrophones at the Atlantic Undersea Test and Evaluation Center, Andros Island, Bahamas. The bottom mounted hydrophones are used to localize the tagged animal and measure the received level of each click. Pitch, roll and heading from the DTag are used to determine the horizontal and vertical aspect angles relative to the hydrophone. An estimate of the M. densirostris horizontal and vertical transmission beam pattern based on four dives will be presented.
Sound source segregation by goldfish: Two simultaneous tones
Authors: Fay Richard R.
Published: May 2008

In 1964, van Bergeijk asked, "...given that a fish can discriminate between sounds A and B when they are presented separately, can he still discriminate either one when both are presented simultaneously? Or do the two sounds blend to form a new entity (such as a chord)." This question was a very early query about sound source segregation by fishes. We have investigated the role that frequency separation plays in this phenomenon using classical respiratory conditioning with a stimulus generalization paradigm. Groups of animals were first conditioned to 2-tone mixtures comprised of 150 Hz (A) and another frequency (B) ranging from 300 Hz to 750 Hz. Generalization tests were then carried out using single tones between 50 and 900 Hz. Group mean generalization gradients showed that the two tones were segregated at the widest A-B spacings, and tended to be segregated as the A-B spacing was reduced. The limited resolution of the test procedure did not allow an answer at the narrowest spacings. Source segregation, even of abstract tones, may be a fundamental feature of the sense of hearing of all organisms, and occurs in the absence of auditory cortex and complex cognitive abilities.
Passive tomography of the oceanic environment using ambient noise cross-correlations
Authors: Sabra Karim G.
Published: May 2008

The random nature of noise and scattered fields tends to suggest limited utility. Indeed, acoustic fields from random sources or scatterers are often considered to be incoherent, but there is some coherence between two sensors that receive signals from the same individual source or scatterer. An estimate of the Green's function (or impulse response) between two points can be obtained from the cross-correlation of ambient noise recorded at these two points. Recent theoretical and experimental studies in ultrasonics, civil engineering, underwater acoustics and seismology have investigated this technique in various environments and frequency ranges. These results provide a means for passive tomography of the ocean environment using only the ambient noise field, without the use of active sources. The coherent wavefronts emerge from a correlation process that accumulates contributions over time from noise sources whose propagation paths pass through both receivers. We will examine the background physics of extracting these coherent structures and present experimental results confirming these theoretical arguments. Further we will present experimental results such as using noise for time synchronization and localization of unconnected acoustic receivers, and for constructing passive tomographic images of the environment.
Passive Geoacoustic Inversion using broadband ship noise in Bay of Biscay shallow water environment
Authors: Gervaise Cédric
Published: May 2008

Our communication proposes a new geoacoustic inversion method for shallow water environments (100 to 300 m). The method relies on the inversion of broadband noise produced by ships of opportunity. The interference patterns generated by the ship movement and the propagation properties of the waveguide are exploited to extract the relative dispersion curves on a chosen bandwidth. These curves are then inverted to estimate geoacoustic properties. This inversion scheme was previously tested (with success) against real data from a very shallow water (10 to 30 m) trial performed off the Southern coast of Barcelona, Spain [1]. To deal with shallow waters, our inversion scheme is improved and tests against real data from PASSTIME trial performed in Bay of Biscay during October 2005. Inversion's results are compared with ground truth and the results showed to be accurate and robust. The proposed technique, which is suitable to a small number of hydrophones and quite easy to implement, offers interesting perspectives for passive geoacoustic inversion. [1] S. Vallez, C. Gervaise, Y. Stephan, M. Andre, Inversion géoacoustique d'un canal très petits petits fonds à partir des navires en mouvement - traitement incohérent, accepté pour publication Revue Traitement du Signal
The passive mode tomography of the ocean using data from short vertical arrays bent by the ocean currents
Authors: Shurup Andrey , Sergeev Sergey , Burov Valentin
Published: May 2008

The possible realization of passive ocean tomography based on the widely discussed relation between the Green's function and ambient noise cross-correlation is discussed. The problem is considered in the mode representation of acoustic field in adiabatic approximation. The estimated time of signal accumulation required to determine the Green's function with sufficient accuracy reveals the possibility of implementing the schemes of the mode tomography of the ocean based on the measuring the ambient noise field of the ocean. It is shown that the use of the vertical arrays with vector receivers allows a decrease in the accumulation time to one or several hours, depending on the conditions of experiment. The mode structure of acoustic field is determined from the cross-correlation matrix of the noise field received by the hydrophones of short vertical arrays bent by the ocean currents and covering only the part of the sound channel. The proposed algorithm differs from the commonly used mode-filtering procedure and allows a compensation of antenna declination from the vertical profile and takes into account of the finite length of antenna aperture, that is ordinary explored in ocean experiments.
Acoustic modeshape inversion using deep water ambient noise measurements
Authors: Wage Kathleen E. , Almuhanna Khalid
Published: May 2008

Assuming that ambient noise can be represented by a sum of uncorrelated acoustic modes, the eigenvectors of the noise covariance matrix for a vertical line array should correspond to the sampled modeshapes. In previous work several authors have investigated using an eigendecomposition of the noise covariance to estimate the mode functions in shallow water, e.g., Wolf et al. [Proc. of the 1993 IEEE Oceans Conf.,vol. I, pp. 99-104], Hursky et al. [J. Acoust. Soc. Am., 109(4), pp. 1355-1366], and Nielsen and Westwood [J. Acoust. Soc. Am., 111(2), pp. 748-756]. While the same approach should work for deep water scenarios, only few deep water experiments have deployed arrays with sufficient aperture to resolve the modes, e.g., the work D'Spain et al. [Pure appl. geophys., Vol. 158, pp. 475-512]. This paper explores the problem of inverting for the acoustic modes of a deep water waveguide using ambient noise measurements. In particular the paper focuses on important signal processing issues, including data snapshot requirements, and the effects of array tilt. Data from a deep water propagation experiment will be used to quantify how well the empirical modes match the true modes derived from measured environmental data. [Work supported by an ONR Young Investigator Award.]
Relationship Between Mechanical Properties and Acoustic Parameters Obtained from Fast and Slow Waves for Cancellous Bone
Authors: Harada Masaki , Tanaka Kazuto , Katayama Tsutao , Mizuno Katsunori , Soumiya Hiroki , Matsukawa Mami
Published: May 2008

The bone-density measuring equipment using the characteristics of the ultrasound has been applied for the diagnosis of osteoporosis. The propagated ultrasonic wave in the cancellous bone changes dramatically due to its complicated structure, and is separated into fast wave and slow wave. The parameters obtained from two-waves are closely related to the structure properties and the elastic properties of bone, which is considered to provide important information related to bone strength. However, the relationship between the strength obtained by the mechanical tests and the fast and slow wave properties is not clearly investigated. In this study, compression tests of the cancellous bovine bone were conducted to determine the compressive strength in addition to the ultrasonic measurements. Our results showed that amplitude ratio of fast and slow wave significantly correlated (r2=0.88) with the compressive strength, which reasonably indicates that the bone strength increases in proportional to the density of the cancellous bone.
Using Singular Value Decomposition to analyse a low frequency contribution on human cortical bone with a 1MHz axial transmission probe
Authors: Sasso Magali , Talmant Maryline , Haiat Guillaume , Laugier Pascal , Naili Salah
Published: May 2008

The configuration of axial transmission technique dedicated to cortical bone characterization generates multiple contributions, associated with different propagation modes. The first arriving signal velocity is classically evaluated using time-of-flight measurements while the analysis of later arrivals requires the development of specific signal processing tools. We focus here on an Energetic Low Frequency (ELF) later contribution acquired by a 1-MHz multi-element bi-directional probe devised in the LIP. Using a procedure adapted from the Singular Value Decomposition (SVD), the ELF contribution was separated from the rest of the signal. The ability of the method to provide an accurate phase velocity estimate of a dispersive wave was established in a controlled-case study on the propagation of Lamb waves on plates using FDTD (Finite-Difference Time-Domain) simulations. The method applied on signals acquired previously in vitro on human radii using the bidirectional device show that the ELF is consistent with the A0 Lamb mode and that its velocity is related to cortical bone thickness (R2 = 0.6, p < 10-5). Identification of A0 type wave agree with results reported in the literature obtained with a mono-element device which operates in the 100-300 kHz frequency band.
A finite element model of the lamellar osteonal structure based on ultrahigh frequency acoustic impedance data
Authors: Raum Kay , Grimal Quentin , Gerisch Alf
Published: May 2008

Materials: A finite element (FE) model was developed, in which the osteon is considered to consist of a central Haversian canal filled with an incompressible fluid and surrounding sets of lamellar units. Each lamellar unit was further subdivided in five sublayers, whereas the orientation of the symmetry axis between adjacent sublayers was shifted clockwise. A sublayer consists of one to ten layers of parallel oriented mineralized collagen fibrils (thickness: 0.2 μm, constant transverse isotropic stiffness tensor). Results: A variation of the sublayer thicknesses results in either isotropic or anisotropic tissue compound properties. By changing the individual layer thicknesses various degrees of anisotropy could be produced. A good agreement with the lamellar pattern obtained in 1.2-GHz SAM images as well as with the anisotropic elastic coefficients measured at the tissue level (50-MHz ultrasound) was obtained by choosing an asymmetric lamellar unit. Conclusions: With the proposed combination of experimentally derived microelastic and microstructural data by 1.2 GHz SAM and a micromechanical FE the homogenized elastic stiffness tensor of lamellar bone tissue was derived. The tissue anisotropy was explained by the asymmetric twisted plywood structure.
Point spread function of the limited-view array transducers in optoacoustic tomography: numerical and experimental studies
Authors: Pelivanov Ivan , Khokhlova Tatiana , Simonova Varvara , Podolsky Alexei , Karabutov Alexander
Published: May 2008

Optoacoustic (OA) tomography utilizes pulsed laser radiation for thermoelastic excitation of wideband ultrasonic pulses. The distribution of laser-induced heat release can be reconstructed if the ultrasonic pulses are detected by an array of transducers. The resolution provided by an array depends on various aspects of its design - the number of elements, element size, spacing and arrangement - and is determined by the point spread function (PSF) of the array. In present work PSFs of arrays with different characteristics are calculated using the Rayleigh integral for simulating the direct problem, and backprojection algorithm for solving the inverse problem of OA tomography. Universal dependencies of the resolution provided by an array on the dimensions and arrangement of its elements are found. Numerical studies are validated by experimental measurements of PSFs of different arrays.
Resonance frequencies of the multilayered piezotransducers
Authors: Arnold Francisco J.
Published: May 2008

Piezoelectric transducers used in high power ultrasonic applications are composed of piezoelectric ceramics, metallic blocks and a central bolt that pre-stresses the assembly. The impedance characterization of these transducers has been done by using numerical methods but, in many cases, one-dimensional simplified models are enough to a good physical interpretation of the problem. In this work was used the Mason's equivalent electric circuit for one-dimensional modeling of composed transducers. It was derived Thevénin's equivalent circuit to simplify the problem and evaluate the effects of the central bolt on the resonances. Some transducers were mounted and the transmission line circuit was used to measure the resonance frequencies. The results show a good fitting between the experimental and simulated by electric circuit. By using the presented model it was identify other longitudinal vibration modes further that considered in previous models and, so that, it was increased the possibility of investigate the behavior of the transducers using the frequency spectrum.
Tactile Touch Plate with Variable Boundary Conditions
Authors: Ing Ros Kiri , Cassereau Didier , Fink Mathias , Nikolovski Jean-Pierre
Published: May 2008

The touch screen device is becoming more and more widespread because it is a very user friendly human/machine interface. In acoustic domains, several approaches are used to realize such a device. Triangulation or Rayleigh waves absorption are such classical methods. However, these approaches are limited because they need a large number of sensors and are only applicable to plates of constant thickness and homogeneous materials. To remedy these limitations, a new approach is proposed using only two sensors. In this approach, one sensor is used to excite the plate, either continuously or impulsively. The second sensor is used to detect the acoustic waves generated in the plate. When an object comes into contact with the plate, some acoustic wave characteristics change. These changes affect different frequencies and depend on the position of the contact point. Comparing these changes with pre-recorded values, it is possible to achieve a tactile touch plate that only responds to specific touch locations. Several experiments with different types of plates were conducted and the results will be presented.
Surveillance and Protection of Underwater Archaeological Sites: Sea-Guard
Authors: Akal Tuncay , Guerrini Piero , Kuperman William A. , Koprulu Kerem , Roux Philippe , Sabra Karim G.
Published: May 2008

Recent advances in underwater detection and survey techniques have increased the possibility of finding the wrecks of vessels and their cargoes. Since prehistoric times, many populations have used vessels for transportation and trade and built harbors and it is now estimated that there are about a million antique wrecks that lie underwater, still to be discovered. Many of these wrecks and ancient harbours lie within shallow depths and can be discovered and accessed easily by humans using available hardware such as side-scan sonars, multi-beam echo sounders, ROVs, GPS navigation, diving gear. Even though the majority of known archaeological sites on land are well protected by guards and high tech equipment, there is no technology for surveillance and protection of underwater archeology sites. This paper presents a new system specifically adapted for the surveillance and protection of underwater archaeological sites (SEA-GUARD). Options available to the acoustic sensor suite of this system are pressure hydrophones and/or vector sensors. The system is based on an underwater acoustic monitoring of the noise field near an archaeological site sending preprocessed signals as an alarm to the authorities on shore via GSM/GPRS or Satellite network.
Micromachined probe performance assessment
Authors: Legros Mathieu , Meynier Cyril , Ferin Guillaume , Dufait Rémi
Published: May 2008

In recent years, Capacitive Micromachined Ultrasound Transducer (CMUT) technology was widely investigated and functional prototypes have been released by several R&D teams. CMUT technology offers outstanding characteristics in acoustic, interconnect packaging capabilities or in integration features that are exciting criteria for new medical applications. We propose a full acoustic characterization report of a CMUT probe. A linear array was fully packaged with electronic preamplifier boards integrated. A complete acoustic characterization of the probe is then performed and presented. In a second phase, a linear probe with piezocomposite technology is realized. The conception is done in regard to the geometric characteristics and to the acoustic response of the micromachined probe. Then an electro-acoustical benchmark CMUT / piezocomposite is realized in the closest conditions. Using a commercial ultrasound imaging platform, an image assessment is performed. The images are first analysed in a quantitative way with a tissue mimicking phantom, using a computerized tool who considered imaging parameters such as contrast, resolution or signal to noise ratio. In a second way, a clinical perspective is discussed with in vivo images.
Design of dispersive layered SAW filters with CMOS low noise amplifier
Authors: Gryba Tadeusz T. , Carlier Julien , Ntagwirumugara Etienne , Zhang Victor Y. , Lefebvre Jean-Etienne J.
Published: May 2008

Up to now, RF front-end surface acoustic wave (SAW) filters for mobile communication are mainly fabricated on LiNbO3 and LiTaO3 substrates. A monolithic integration of these filters on Si substrates is highly desirable, but Si is non piezoelectric. One alternative is the deposition of a piezoelectric film on the semiconductor substrate. CMOS technology is very attractive for integrating the radio frequency modules in a single chip. This paper presents the analysis and realisation of a SAW passband filter on silicon substrate based on a piezoelectric ZnO thin film working near 1 GHz , integrated with a CMOS low-noise amplifier. We propose a modified coupling of modes (COM) approach for a layered ZnO/Si surface acoustic wave filter. The COM parameters in this formulation are the Rayleigh wave velocity, the electromechanical coupling coefficient, the complex reflection coefficient, the transduction coefficient and the inter-digital capacitance C. This is a dispersive SAW layered filter some parameters of which become frequency dependent due to the phase velocity dispersion. We present the theoretical and experimental results of the filter integrated with a CMOS low noise amplifier.
Performance Evaluation of 3D Sound Field Reproduction System with a Few Loudspeakers and Wave Field Synthesis
Authors: Naoe Munenori , Kimura Toshiyuki , Yamakata Yoko , Katsumoto Michiaki
Published: May 2008

A conventional 3D sound field reproduction system using wave field synthesis places a lot of loudspeakers around the listener. However, since such a system is very expensive and loudspeakers come into the listener's field of vision, it is very difficult to construct an audio-visual system with it. We developed and evaluated a 3D sound field reproduction system using eight loudspeakers placed at the vertex of cube and wave field synthesis. We compared the sound localization of a loudspeaker array with that of seventeen loudspeakers placed around the listener and found that their localization capabilities were equivalent except the normal direction of cube's planes.
Optimal array pattern synthesis with desired magnitude response
Authors: Pasqual Alexander Mattioli , Arruda José Roberto , Herzog Philippe
Published: May 2008

Letting Euclidean norm be the performance parameter, the task of finding the best approximation of a complex function in a finite dimension subspace leads to a convex optimization problem that can be easily solved by the least-squares method. However, this procedure leads to a sub-optimal solution in applications that have no phase requirements on the approximated function. In this case, semidefinite programming has been used to obtain optimal magnitude responses. In this work, this non-convex optimization problem is dealt with by using an iterative method based on the least-squares, which is illustrated on directivity synthesis by spherical loudspeaker arrays. Usually, instead of synthesize directly the desired pattern, the strategy adopted is to reproduce its truncated spherical harmonic representation. The truncation order is determined by the number of drivers of the spherical array. It is shown that truncation error and signal powers can be significantly reduced if phase error is neglected, providing potential means to improve directivity synthesis for applications requiring only magnitude response.
DELTAEC is also an acoustics teaching tool
Authors: Garrett Steven
Published: May 2008

A major revision of the Los Alamos thermoacoustics code, renamed DELTAEC, was released in 2007. It takes advantage of a user-friendly, menu-driven Windows environment and has indigenous plotting capabilities. DELTAEC is a differential equation solver that analyzes one-dimensional acoustical networks defined by a series of "segments" representing ducts, compliances, speakers, etc. This talk will relate experiences using this software to teach a first-year graduate core course on acoustics in fluids. Examples include illustration of effective length and quality factor of Helmholtz resonators, as well as the more challenging standing wave solutions within a resonator of variable cross-section. The plotting feature allows immediate illustration of the pressure and velocity fields as well as power flow within the resonator. DELTAEC will also adjust gas mixture concentration to match a specified frequency. Segments representing electrodynamic loudspeakers, radiation loading, and flow resistance in porous media will be used to demonstrate the coupled-oscillatory behavior of a bass-reflex enclosure's complex electrical impedance vs. frequency. Calculation of the modes of a catenoidal horn of finite length will be presented. The "thermo-physical property" feature provides fluid and solid properties at the students' choice of pressure, temperature and frequency, making it useful as a "handbook" for other assignments.
Systems control theory for sound synthesis: an overview
Authors: D'Andréa-Novel Brigitte , Matignon Denis
Published: May 2008

The aim of this talk is to present some classical techniques and methods from control theory to deal with the problem of sound synthesis based on physical models. A first part will be devoted to the case of finite-dimensional state space, illustrated by: 1. Kelly-Lochbaum structure for 1D wave equations; 2. Realization theory for passive impedance of rational type. The second part considers the infinite-dimensional case. More precisely the authors will present: 1. The operator associated to PDEs in acoustics, its diagonalization leading to "Riemann invariants" useful to study stability properties; 2. A Lyapunov method to elaborate boundary control to ensure stabilization of an equilibrium regime and some kind of robustness; 3. Diffusive realizations of fractional time derivatives, useful when modeling visco-thermal losses in acoustical ducts. These tools are well adapted to the class of "wind instruments".
Modeling and automatic control of a slide flute
Authors: D'Andréa-Novel Brigitte , Fabre Benoit , Coron Jean-Michel
Published: May 2008

In this paper, we consider the problem of modeling and control of a slide flute: a kind of recorder without finger holes but which is ended by a piston mechanism to modify the length of the resonator. A previous study has been done, but with a very simple boundary condition for the mouth, corresponding to an ideal situation assuming that the acoustic pressure is zero at the entrance of the resonator. In this work, we have taken into account a more realistic model, describing the coupling effects between the jet and the pipe. The jet is obtained by blowing through a flue channel and formed by flow separation at the flue exit, and finally directed towards a sharp edge, called the labium. The resulting structure will be described by two linear PDEs coupled with nonlinear ODEs describing the boundary conditions: for the mouth, taking into account the jet dynamics, and for the piston. A modal analysis is performed using the linearized boundary conditions which can also be used to compute the suitable blowing pressure and the suitable pipe length to obtain a desired fundamental frequency or equivalently a desired pitch. This will constitute the basis of our control algorithm.
Production and perception of goal-points and coarticulations in music
Authors: Godo/y Rolf Inge , Jensenius Alexander Refsum , Nymoen Kristian
Published: May 2008

From our studies of sound-related movement (http://musicalgestures.uio.no), we have reason to believe that both sound-producing and sound-accompanying movements are centered around what we call goal-points, meaning certain salient events in the music such as downbeats, or various accent types, or melodic peaks. In music performance, these goal-points are reflected in the positions and shapes of the performers' effectors (fingers, hands, arms, torso, etc.) at certain moments in time, similar to what is known as keyframes in animation. The movement trajectories between these goal-points, similar to what is known as interframes in animation, may often demonstrate the phenomenon of coarticulation, i.e. that the various smaller movement are subsumed under more superordinate and goal-directed movement trajectories. In this paper, we shall present a summary of recent human movement research in support of this scheme of goal-points and coarticulations, as well as demonstrate this scheme with data from our ongoing motion capture studies of pianists' performance and other researchers' motion capture data.
Inverse problem: Recovering the full-state of a simplified model of a trumpet-like instrument from the radiated pressure
Authors: Hélie Thomas , D'Andréa-Novel Brigitte
Published: May 2008

We consider a simplified model of a trumpet-like instrument composed of a valve (including the mechanics of the lips), a jet (coupled with the valve dynamics), and an acoustic pipe excited by the jet and radiating in the air. A special care is devoted to the energy balance of the whole system and its dissipative property. This leads us to introduce a model of a non-stationary jet. In a second step, the problem of the observation of the full-state (that is, the position and the velocity of the lips, the flow and the pressure in the jet and in the acoustic pipe) from the radiated pressure is analyzed. This problem can be recasted as a problem of control engineering, using a so-called neutral system (differential system including the delayed state and its time derivative). We show how the energy balance can help to solve this problem and define a naturally well-posed observator. As a last step, this work is recasted in the context of a more general inverse problem: What control input (pressure in the mouth, parameter of the lips, etc) must be used to feed the model in order to recover a target sound?
The interaction between the strings and soundboard of a harp
Authors: Waltham Chris
Published: May 2008

The harp is an instrument with a set of plucked strings that excite the sound board directly, without the medium of a bridge. The strings are positioned at an acute angle to the plane of the sound board. The quality of the sound produced depends on the motion of the string, which is non-planar, and its interaction with the resonances of the sound board. The interaction is intrinsically non-linear as the soundboard responds to changes in both the angle and the tension of the string. To avoid the difficulties of string-string interactions on a real harp, a small test "instrument" has been constructed with a single string and a variable-angle sound board. The string and sound board motions have been measured simultaneously. Preliminary results will be presented.
Exploration of timbre variations in music performance
Authors: Barthet Mathieu , Guillemain Philippe , Kronland-Martinet Richard , Ystad Solvi
Published: May 2008

Timbre has seen during the twentieth century a growing attention from both musicians and scientists, the former to expand a traditional music system until now governed by the structures of pitches, the latter to better understand how timbre is produced and how it is processed by the perceptive and cognitive systems. In the music performance context, many studies deal with the role of timing and dynamics, but much fewer are dedicated to the one of timbre. The works presented here aim at showing the importance of timbre variations from two points of view: the production of sounds and their perception. The relations between the control parameters (mouth pressure and reed aperture) of a simplified physics-based clarinet synthesis model and the generated timbres have been investigated. Experiments have further been done to measure the within-individual consistency of timbre variations of a clarinet player repeating several instances of a musical excerpt from a Bach piece while keeping the same musical intention. Brightness variations characterized by the time-varying Spectral Centroid showed a strong consistency across the repetitions. The influence of such brightness variations on the perceived musical quality of a performance was then assessed thanks to an analysis-transformation-synthesis paradigm.
A setup for measurement of bowing parameters in bowed-string instrument performance
Authors: Schoonderwaldt Erwin , Demoucron Matthias , Rasamimanana Nicolas
Published: May 2008

An accurate measurement of instrumentalists' actions in playing situations is the basis for several research topics such as musical performance analysis, control of sound synthesis algorithms or effective validation of theoretical results in musical acoustics. We present a setup for a complete and accurate measurement of bowing parameters in bowed-string instrument performance, with minimum interference for the player. The method is based on the combined use of motion capture and sensors attached to the bow. An optical motion capture system was used to track the position and orientation (6 DOF) of the bow and the instrument. In addition, sensors were attached to the frog of the bow for measuring bow acceleration in different axes and bow force exerted on the strings. Both sensors can be easily attached to any bow. We will describe how the data from the different systems are combined for an accurate calculation of bowing parameters, such as bow-bridge distance, bow velocity, bow acceleration, bow angles and bow pressure. Finally, we will present examples of measurements and briefly discuss some potential applications.
Eliminating environmental stressors in hospitals: managing noise through different interventions
Authors: Phiri Michael
Published: May 2008

There is growing body of knowledge of over 1,000 scientific studies which provide evidence that patients experience positive health outcomes in an environment that incorporates natural light, elements of nature, soothing colours, meaningful and varying stimuli, peaceful sounds, pleasant views and a sense of beauty. This paper reviews the research, its practical applications in order to enhance acoustics comfort and quality of care in healthcare settings. Healthcare planners can carry out small-scale, medium- and large-scale evidence-based design interventions. Small-scale interventions which minimise cost maximise impact on acoustic comfort can be implemented relatively quickly and easily e.g. provision of rubbish bins with a damping system to close lids slowly, dimming lights on the wards etc. Control measures include strategies to reduce noise levels in healthcare facilities with or without physical environmental alterations including specification of appropriate absorbent materials (e.g. acoustic ceiling tiles). Medium-scale interventions e.g. inpatient or nursing unit design involve consideration of the shape, geometry and other characteristics of a room in order to deal with background noise, speech intelligibility and other elements which promote acoustic comfort. Large-scale interventions involve large capital works notably entire hospital complexes, assemblies of departments/specialties but have evidence extrapolated from the small- and medium-scale interventions.
Don't forget the quench pipe when installing an MRI
Authors: Ostendorf Carel
Published: May 2008

An MRI is a useful medical device but it makes a lot of noise. A sound level of 90 dB(A) or more in the MRI room is not unusual. Placing an MRI in an existing hospital means that extra care has to be taken to prevent the noise from the MRI causing nuisance in adjacent rooms. In this paper the situation is discussed in which complaints appeared after the installation of the MRI. First sound measurements were done to see if the sound level in the office above the MRI fulfils the noise ratings. This way it would be clearer if the acoustic measures were doing their job. Whatever the outcome, the hospital wanted to put an end to the complaints. So, more sound measurements were done to establish the cause of the nuisance and to point out what extra measures have to be taken to solve the problem. It turned out that the quench pipe played an important role in this situation.
Development of low noise tyres in EC project SILENCE
Authors: Saemann Ernst-Ulrich
Published: May 2008

A lot of efforts were made in the last two decades to lower the tire/road noise. The tire industry has optimized the tread pattern as the main influence parameter so that nowadays the radiated sound pressure of a modern tire in the far field is very close to that of a blank tire with the same construction. Because the tread pattern is needed to achieve the required safety level further noise reduction has to be addressed mainly by tire construction. For many years tire manufacturers have been searching for a construction, which fulfils the targets of the automotive industry and generates less noise. The research was done not only in house but also with public projects. In the EC Project SILENCE a subproject has provided design solutions and hardware solutions for noise reduction, with respect to vehicle/tyre/road integration, under typical urban and suburban traffic conditions. This improvement is based on an increased understanding of noise generation and radiation mechanisms gained by the further development of experimental and simulation techniques. A series of low noise tyres (prototypes) has been developed and tested on a selection of appropriate low noise road surfaces.
A contact solver suitable for tyre/road noise analysis
Authors: Schutte Arjan , Wijnant Ysbrand H. , De Boer André
Published: May 2008

Road traffic noise is a major environmental problem in modern society. The interaction between tyre and road surface, the major noise source, is non-linear and is best described in the time domain. The currently used contact models for acoustic analyses have problems with either accuracy or calculation speed. At the Structural Dynamics and Acoustics group of the University of Twente an alternative contact algorithm has been developed. The characteristic feature of this algorithm is that, while solving the set of equations, the contact condition, i.e. the condition stating that there is no overlap between the bodies, is satisfied exactly. Hence, there is no need for contact elements or contact parameters. The possibility to optimize and speed up the algorithm, using multigrid is the major advantage of the new approach. In this paper the contact algorithm is applied to a two-dimensional finite element model. Coulomb friction is taken into account. Some test simulations illustrate the ease of the algorithm. The model will be extended and non-linear material behaviour will be added. Multigrid and multilevel will be used to speed up the calculation. The goal is to compute the vibrations and radiated noise pattern of a profiled tyre rolling on a road.
The effect of porous road surfaces on radiation and propagation of tyre noise
Authors: Peeters Bert , Kuijpers Ard
Published: May 2008

It is well-known that porous road surfaces are very effective for the abatement of tyre/road noise. However, the physical principles behind the noise-reducing properties of these surfaces are not well understood and often even misinterpreted. Lack of understanding becomes a problem when developing a prediction model for tyre/road noise to be able to optimize the road surface for noise abatement. In the framework of the EU SILENCE project and the Dutch IPG program a model has been developed to predict the influence of road surface porosity on the radiation and propagation of tyre/road noise. First step in the model development was to gain physical insight from stationary and vehicle measurements with passenger car and truck tyres on both dense and porous surfaces. Next step was to qualitatively and quantitatively describe the observed physical phenomena in a mathematical model according to the KISS principle: avoid unnecessary complexity, both in input parameters and in the mathematical model. The end result is a mathematical model that describes the noise reduction potential for a standard tyre on various (porous) road surfaces, using a sound absorption spectrum as input. This model is available for a broad audience in the recently launched SPERoN acoustic optimization tool.
Measurement Method for Noise Exposure of Jobs of the Construction Sector
Authors: Quintana Samuel , Fernandez Marcos D. , Chavarria Noelia , Ballesteros Jose A. , Gonzalez Isabel
Published: May 2008

Noise is one of the physical contaminants with a high presence in the construction sector. Nowadays, several negative effects produced by the exposure to noise are known, mainly regarding hearing. Although there is evidence of the existence of many other effects, some of them are not characterized precisely yet. Due to the importance that these effects have on the worker's health and well-being, it is necessary to develop some mechanisms to study and suggest preventive solutions on these questions. In this work, it has been studied the most appropriate measurement method for taking, as precisely as possible, the noise levels that the workers of the construction sector are exposed to. Several measures have been taken and analyzed to determine the best indexes and parameters to characterize the noise in the construction. For which, the current European regulations regarding the noise exposure (Directive 2003/10 of the EU) have always been taken into account.
Adaptive closed-loop control of cavity flows
Authors: Cattafesta Louis , Arunajatesan Srinivasan , Song Qi , Moreno Cesar , Palaviccini Miguel
Published: May 2008

Results from a combined experimental and computational study are presented on the development of an adaptive feedback controller for the suppression of cavity pressure loads. The experiments are performed in a variable-sized cavity in a high-speed wind tunnel, while the computations are performed using the CRAFT CFD flow solver. The adaptive control system incorporates recursive algorithms for system identification with disturbance rejection algorithms for feedback control. Results are presented using unsteady surface pressure sensors on the cavity walls and an array of zero-net mass-flux (ZNMF) actuators at the leading edge. The experimental data are used to compare with and validate the computations. These novel simulations form a virtual experiment testbed that is used to assess, for example, actuator type, placement, and requirements and also candidate identification and control algorithms.
A new instrument for the measurement of occupational vibration
Authors: Faiget Laurent , Dupont Fernand , Aujard Christine
Published: May 2008

Directive 2002/44/CE relative to the risks arising from vibration has been transcribed into national laws of most Member States. This directive deals with the determination of limits and action values for the daily exposure to vibration. Two physiological domains are addressed: the "hand-arm" and the "whole-body" domains, the acceptable statutory values of which are specified in the text. The experimental protocol, as well as indicators relevant for assessment, is defined in Standards ISO 5349-2 and ISO 2631-1. The equivalent frequency-weighted acceleration shall be measured on the 3 axes x, y and z, the bandwidth of which is defined for each domain. 01dB-Metravib introduces a new portable instrument that perfectly meets the requirements of this statutory application. A blind metrological instrument connected to a triaxial accelerometer is installed on site. The instrument is remotely controlled by the operator using a wireless remote control of the Pocket PC type. This remote control is used to manage measurement configurations ("whole-body", hand-arm"), to start acquisitions (immediate, delayed mode) and to collect measured data for post-processing and archiving purposes. We will present metrological and operational advancements of this new instrument and describe a real case study dealing with the assessment of daily exposure to vibration.
Exact solutions to the acoustic source reconstruction problem
Authors: Maury Cédric , Bravo Teresa
Published: May 2008

In this study analytical solutions are derived for the singular radiation and velocity patterns of a baffled elastic beam, thus leading to closed-form expressions for the singular value expansion of a number of integral operators which map a boundary velocity onto the acoustic pressure distribution radiated in far-field or intermediate regions. Exact solutions to this problem involve prolate spheroidal wave functions which correspond to a set of independent distributions with finite spatial support and with maximal energy concentration in a given bandwidth in the wavenumber domain. A stable solution to the inverse source reconstruction problem is obtained by decomposing the unknown boundary velocity into a number of efficiently radiating singular velocity patterns which corresponds to the number of degrees of freedom of the radiated field. It is found that the degree of ill-posedness of the inverse problem is significantly reduced when considering a hemi-circular observation arc with respect to a linear array of sensors, by a factor scaling on the small angular aperture subtended by the observation line. Estimates are derived of the spatial resolution limits that can be achieved in the source reconstruction problem from the dimension of the efficiently radiating subspace.
Tonalness perception of harmonic complex tones
Authors: Fingerhuth Sebastian , Parizet Etienne
Published: May 2008

Many everyday sounds have a more or less tonal characteristic. This normally means they have some peaks in the spectrum and generate one or more of the pitch sensations. In this work we present the results of a listening test which deals with the perception of tonalness of harmonic complex sounds. It consisted in presenting sounds via headphones to the 30 listeners who had to evaluate the tonalness using magnitude estimation with a reference sound. The sounds presented to the listeners varied in some parameters which modified the perception of tonalness. The parameters are: i) tone to noise level (3dB steps), ii) number of harmonics (1, 2, 4, 8 and 8 with f0 and f1 removed) and iii) spectral shape of the harmonics (constant, -5dB/oct and 5dB/oct). The loudness of the stimuli were equalized. Tonalness increases for higher tone to noise ratio. A change in the spectral shape is most important for a high number of harmonics. More harmonics also increase tonalness mostly for constant and increasing spectral shape. The results of the test were also compared with the tonalness calculation algorithm from Aures' and the german DIN45681 model. Both gave a correlation coefficient > 0.95.
Road pavement classification based on noise emission characteristics
Authors: Paulo Joel P. , Bento Coelho J. Luis
Published: May 2008

The measurement procedure to evaluate the influence of road surface characteristics on vehicle and traffic noise is designated by Close-Proximity (CPX) method, as described in the ISO 11819-2 draft. This procedure consists on acquiring the vehicle rolling noise signal near the tires and close to the surface by means of at least two microphones, in a special arrangement for the determination of the Close-Proximity Sound Index (CPXI). Roadtraffic noise is estimated by taking into account the absorption characteristics of road surface on the propagation of sound and the speed and type of vehicles. However, the particular characteristics of the different pavement types, which may influence the sound radiation, are not considered. The main goal of this research is to identify and classify different types of road pavements, for different stress conditions, using the CPX method. Such information can be used as a guideline for calibrating noise mapping models in order to achieve more realistic and accurate results. The classification of the different road surfaces consists on a supervised learning technique based on the Support Vector Machine, SVM, algorithms. Results based on error analysis are presented and discussed.