Σε αυτή τη διπλωματική μελέτη ασχοληθήκαμε με το σχεδιασμό και εσωτερικής ηλεκτρικής εγκατάστασης και ακουστικής μελέτης με τη βοήθεια ηλεκτρονικού υπολογιστή (AutoCAD και CATT-Acoustic), του Μαρκίδειου θέατρου της πόλεως Πάφου - Κύπρου. / --

Dans un grand nombre d'applications industrielles, il est nécessaire d'inspecter des structures rayonnantes à l'aide de techniques de caractérisation et de localisation de sources acoustiques instationnaires. Ces dernières décennies, plusieurs techniques d'imagerie acoustique ont été développées, reposant sur l'utilisation de mesures d'un jeu de grandeurs acoustiques (pression et/ou vitesse particulaire) sur des antennes microphoniques, structurées ou non. Le travail réalisé durant cette thèse porte plus spécifiquement sur les techniques d'imagerie instationnaires par retournement temporel. Nous nous intéressons plus particulièrement aux optimisations permettant de rendre les performances de ces techniques d'imagerie instationnaires insensibles aux conditions de mesures (environnement réverbérant et bruité). Pour cela, différentes améliorations sont proposées dans ce manuscrit, grâce à des mesures réalisées sur une antenne hémisphérique double-couche. En particulier, nous détaillerons un processus d'imagerie acoustique quantitative par retournement temporel grâce au calcul de l'intégrale de Helmholtz-Kirchhoff retournée temporellement, grâce aux mesures "double données" réalisées sur l'antenne. Ensuite, nous détaillerons les optimisations pour supprimer les effets de salle et les contributions de sources perturbatrices grâce à une méthode de séparation de champs, qui consiste à projeter les données mesurées sur la base des harmoniques sphériques puis à séparer les contributions "entrantes" et "sortantes". Pour finir, la résolution d'imagerie par retournement temporel, intrinsèquement limitée, est améliorée grâce à la définition automatique d'un puits à retournement temporel dont la formulation analytique tire partie de la structure double-couche des données mesurées. Il est essentiel de noter que ces différentes stratégies d'optimisation sont possibles grâce à l'enregistrement d'un double jeu de données (pression-pression ou pression-vitesse). La qualité de reconstruction du champ de pression par le processus d'imagerie par retournement temporel double couche complet est illustré à travers des études numériques et des études expérimentales, allant d'une configuration idéale (environnement anéchoïque et non bruité) à un cas complexe (environnement fortement réverbérant et bruité). / For many industrial applications, it is necessary to inspect radiating structures using non-stationary sources localization and characterization techniques. In the last decades, many acoustical imaging methods have been developed. These techniques are based on the measurement of a set of acoustical quantities (pressure and/or particle velocity) on structured (or not) microphones antennas. In particular, this thesis work aims at studying and optimizing non-stationary imaging methods using time reversal. More particularly, we are interested in improvements following to assess precisely the acoustic field with good performances, by making these methods performances insensitive to the measurements conditions (reverberant and noisy environment). For purpose, several improvements are proposed in this manuscript, thanks to measurements realised on a hemispherical double layer antenna. In particular, we detail a quantitative time reversal acoustical imaging process thanks to the calculation of the time reversed version of the Helmholtz-Kirchhoff integral, using the "double data" measurements realised on the antenna. Then, we will detail improvements to suppress both room effects and the perturbative sources contributions thanks to a field separation method, which consists in expanding the measured data onto spherical harmonics functions basis. Then, the "incoming" and the "outgoing" contributions are separated. Finally, the time reversal imaging resolution, intrinsically limited, is improved thanks to the automatic definition of a time reversal sink. Its analytical formulation takes advantage of double layer measurement structure. This of crucial importance to note that all these improvements take advantage from the recording of a double data set (pressure-pressure or pressure-velocity). The quality of the pressure field reconstructed using the full double layer time reversal imaging process is illustrated through numerical and experimental studies, from an idealized situation (anechoic and not noisy environments) to a hard case (highly reverberant and noisy environment).

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The musician needs to properly perceive the sound in rooms where it operates, either in an environment designed to be performed or to studying and practice music. For this, it is necessary that these sites are acoustically appropriate, enabling the development and enhancement of musical sound perception. In this study six classrooms of the music school of UFSM were characterized by acoustic impulse response measurements and computer simulation, and considered the user s feedback through questionnaires. The questionnaires enabled to understand the preferences of students and music teachers regarding the acoustic quality of a total of twenty rooms for music practice and teaching. Three study rooms and three collective classrooms were the most cited out of those available for the course, which were evaluated by acoustic impulse response, resulting in achieving specified objectives of the main parameters to assess the acoustic quality of rooms by ISO 3382: 2009. The information provided by the musicians proved to be coherent with the measurement data, as the rooms considered dry had presented reverberation times around 0.4 s, and the rooms considered reverberants had reverberation times (RT) around 1.5 s. The six rooms were characterized as clear and well defined rooms, with values for Clarity ranging between 1.0 and 2.0 dB for live rooms and around 22 dB for dry rooms. The definition has remained above 43% for all rooms with Central Time below 50 ms for rooms of greater clarity and less reverberant, and above 90 ms for the live rooms. In general, most rooms were considered weak in relation to acoustic conditioning, and only two out of twenty rooms were considered adequate by most musicians, without receiving considerable negative criticism, being one a study room with a volume of 79.9 m³ and TR equal to 0.4 seconds, and the other a collective classroom with a volume of 327.85 m³ and TR equal to 1.6 s. The computer simulation was efficient for the prediction of the acoustic behavior of the rooms in study and the data obtained in the simulations were compared to the just noticeable difference (JND) for acoustic parameters investigated (T30, EDT, C80, D50 and Ts). A good correlation was observed between measured and simulated data, particularly for parameters related to noise energy in the frequency range from 63 to 8.000 Hz. / O músico necessita perceber adequadamente o som nos recintos onde atua, seja em ambientes destinados à performance, seja em ambientes destinados ao estudo e prática musical. Para que isto seja possível é necessário que estes locais estejam acusticamente adequados, permitindo o desenvolvimento e aprimoramento da percepção sonora musical. No presente trabalho seis salas de aula do curso de graduação em Música da UFSM foram caracterizadas através de medições acústicas da resposta impulso e de simulação computacional, além de considerar a opinião dos usuários mediante questionários. Os questionários aplicados permitiram compreender as preferências dos estudantes e professores de música no que se refere à qualidade acústica de um total de vinte salas para prática e ensino musical. Três salas de estudo e três salas de aula coletiva foram as mais citadas dentre as disponíveis para o curso, as quais foram avaliadas acusticamente através da resposta impulso, resultando na obtenção dos principais parâmetros objetivos especificados para a avaliação da qualidade acústica de salas pela norma ISO 3382: 2009. As informações fornecidas pelos músicos se mostraram coerentes com os dados das medições, de forma que e as salas consideradas secas apresentaram tempos de reverberação (TR) em torno de 0,4 s, e as salas consideradas reverberantes apresentaram tempos de reverberação em torno de 1,5 s. As seis salas se caracterizaram como salas claras e definidas, com valores para Clareza variando entre 1,0 e 2,0 dB para as salas vivas e em torno de 22 dB para as salas secas. A Definição se manteve acima de 43% para todas as salas, com Tempo Central abaixo de 50 ms para salas mais claras e menos reverberantes e acima de 90 ms para as salas mais vivas. Em geral, a maioria das salas apresenta deficiências em relação ao condicionamento acústico, sendo que somente duas das vinte salas foram consideradas adequadas pela maioria dos músicos, sem receber críticas negativas consideráveis, sendo uma sala de estudo com volume de 79,9 m³ e TR igual a 0,4 s, e uma sala de aula coletiva com volume de 327,85 m³ e TR igual a 1,6 s. A simulação computacional se mostrou eficiente para predição do comportamento acústico das salas em questão e os dados obtidos nas simulações foram comparados em relação à diferença no limite do observável (JND) para os parâmetros acústicos investigados (T30, EDT, C80, D50 e Ts). Uma boa correlação foi observada entre dados medidos e simulados, principalmente para os parâmetros relacionados à energia sonora na faixa de frequência de 63 a 8.000 Hz.

Orientador: Sandra Lucia da Cruz / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-08T04:57:11Z (GMT). No. of bitstreams: 1 Sousa_ElisangelaOrlandide_M.pdf: 2598884 bytes, checksum: 7421959dcef02a5096290563b5f4500e (MD5) Previous issue date: 2007 / Resumo: Redes de tubulação são sistemas complexos de dutos utilizados no transporte de fluidos a longas distâncias. Um pequeno vazamento em uma tubulação pode provocar grandes perdas de produtos e sérios danos ao meio ambiente até serem detectados. Com o propósito de prevenir vazamentos em tubulações, várias técnicas são relatadas na literatura. Este trabalho descreve o desenvolvimento e teste de uma técnica de detecção de vazamento de gás em tubulação baseada no método acústico e na análise de transientes de pressão gerados a partir do vazamento. Transientes de pressão e o ruído sonoro gerado pelo vazamento foram detectados e analisados em uma tubulação operando sem e com escoamento contínuo de gás (ar) em várias condições de operação. O trabalho experimental utilizou um vazo de pressão de 34,5 litros e uma tubulação com 60 m de comprimento e ½¿ de diâmetro. A pressão de operação variou de 2 a 7 kgf/cm2. Vazamentos de várias magnitudes foram simulados através de um orifício localizado na tubulação cujo diâmetro variou entre 0,4 mm a 5 mm. O microfone e o transdutor de pressão foram instalados no vaso de pressão ou na tubulação para detectar a ocorrência de vazamento, ambos conectados a um computador PC através de um conversor ADA. O sinal gerado pelo microfone foi amplificado e passou por um banco de filtros passa faixa sendo transformado em três sinais com amplitudes independentes, cada uma com uma faixa de freqüência específica de 1kHz, 5kHz e 9kHz. O programa de aquisição de dados foi escrito em linguagem C para ler e processar os dados. Os resultados experimentais mostraram que é possível detectar vazamentos em tubulações através do método acústico. A análise dos sinais de amplitude para freqüências diferentes mostrou que o ruído sonoro gerado pelo vazamento depende da magnitude do vazamento e da pressão na tubulação. Em todos os experimentos a ocorrência de vazamento foi prontamente detectada pelo microfone enquanto as mudanças nos perfis de transientes de pressão não eram sempre significativas para detectar o vazamento / Abstract: Pipeline networks are complex systems of ducts used in the fluid transportation through long distances. Even small leaks in a pipeline can lead to great losses of product and serious damages to the environment before it could be detected. With the purpose of preventing leakage in pipelines, various techniques have been reported in the literature. This work describes the development and test of a gas leak detection technique in pipelines based on an acoustic method and on the analysis of pressure transients generated by the leak. Pressure transients and the noise generated by leakage have been detected and analysed in a pipeline operating with and without continuous flow of gas (air) under various operation conditions. The experimental setup made use of a 34,5 liters pressure vessel and a 60 m long, ½¿ in diameter pipeline. The operational pressure varied from 2 to 7 kgf/cm². Leakages of various magnitudes were simulated through an orifice located in pipeline whose diameter varied from 0,4 mm to 5,0 mm. A microphone and a pressure transducer were installed either in the pressure vessel or in the pipeline to detect leak occurrence, both being connected to a PC computer through an ADA converter. The signal generated by the microphone was amplified and also passed through a bank of band pass filters being transformed into three signals with independent amplitude, each one with a band of specific frequency of 1 kHz, 5 kHz and 9 kHz. The data acquisition software was written in C language to read and process all data. The experimental results showed that it is possible to detect leaks in pipelines based on acoustic method. The analysis of the signal amplitude for different frequencies showed that the noise signal generated by leakage depend on both leak magnitude and pressure in the pipeline. In all experiments leak occurrence was readily detected by the microphone while the changes in pressure transient profiles were not always significant to detect the leak / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestre em Engenharia Química

Cette thèse traite des effets de la turbulence atmosphérique sur la propagation d'ondes de choc acoustiques. Ces effets sont d'un grand intérêt pour des applications comme le bang sonique, le buzz saw noise ou le tonnerre. Une méthode numérique unidirectionnelle est développée pour modéliser et simuler la propagation tridimensionnelle d'ondes de choc acoustiques en milieu hétérogène en mouvement. Elle repose sur une approche à pas fractionnés qui permet de prendre en compte efficacement les différents mécanismes physiques présents. Pour s'attaquer à des problèmes 3D réalistes (de l'ordre du milliard de degré de liberté), l'implémentation de la méthode est réalisée en utilisant le paradigme de programmation parallèle " single program multiple data ". La validité de cette méthode est évaluée sur différents cas tests. La méthode est appliquée à l'étude des effets de la turbulence atmosphérique sur la propagation du bang sonique dans la couche limite planétaire. Ainsi, le bang sous trace et le bang dans la zone d'ombre sont calculés pour la configuration hypersonique développée dans le projet européen ATLLAS II. Enfin, la focalisation de chocs faibles sur une caustique cuspidée est simulée. Cela est, à notre connaissance, la première étude de la stabilité d'une caustique non linéaire à des perturbations dues à un écoulement. / This thesis deals with the effects of atmospheric turbulence on the propagation of acoustical shock waves. These effects are of major interest for applications such as sonic boom, buzz saw noise or thunder. A numerical one-way method is developed to model and to simulate three-dimensional nonlinear propagation of acoustical shock waves in a moving heterogeneous medium. It relies on a split-step approach that permits to take into account efficiently the different involved physical mechanisms. To tackle realistic 3D problems (of order of one billion of degree of freedom), the implementation of the method is done using the parallel single program multiple data paradigm. Validity of this method is assessed using multiple test cases. The method is applied to investigate the effects of atmospheric turbulence on sonic boom propagation through the Planetary Boundary Layer. Hence, both under-track boom and boom in the shadow zone are studied for a hypersonic configuration developed in the European project ATLLAS II. Finally, the focusing of weak shock waves on a cusped caustic is simulated. It is the first study of the stability of a nonlinear caustic to flow perturbations to our knowledge.

La difficulté de recyclage des pneus usagés en raison de la réticulation de la gomme représente un enjeu environnemental important. Une solution envisagée dans cette étude est la mise en œuvre de poudrettes de pneumatique recyclées (GTR) dans la conception de produits de plasturgie visant un bon amortissement choc, acoustique et vibratoire. Notre travail s’est orienté vers la conception et la caractérisation de deux types de matériaux : 1) Des composites Thermoplastique/GTR, sur 2 matrices thermoplastiques (TP) différentes (Acétate de vinyle (EVA) et polypropylène (PP) mis en œuvre par extrusion/injection, 2) Des plaques composées à 100% de poudrettes GTR élaborées par compaction/chauffage. La qualité de l’interface TP/GTR a été estimée par analyse micrographie électronique à balayage MEB. L’influence des charges GTR sur la cristallinité des matrices a été évaluée par DSC. Une étude en traction a permis de déterminer le module de Young en traction, le seuil d’écoulement ainsi que l’allongement à rupture. L’amortissement vibratoire a été caractérisé par analyse mécanique dynamique (DMA) avec la détermination du facteur de perte η sur une large gamme de températures permettant la construction des courbes maîtresses en fréquence (équivalence fréquence/température WLF). L’amortissement choc a été déterminé par impact de chute de masse instrumenté. Le coefficient d’absorption acoustique a été mesuré au moyen d’un tube de Kundt par la méthode des deux microphones. Ces différents moyens de caractérisation ont montré que l’amortissement de vibrations et d’impacts était augmenté par l’incorporation de charges GTR dans une matrice TP. L’étude de la résilience des mélanges PP/GTR a mis en évidence l’influence de la structure interne des éprouvettes moulées sur les mécanismes d’amortissement des chocs. Les plaques constituées à 100% de poudrettes compactées/chauffées ont démontré une bonne cohésion et d’excellentes propriétés d’amortissement aux chocs. Le coefficient d’absorption acoustique n’est intéressant qu’au voisinage de la résonance des différentes plaques testées. / The difficulty of recycling used tires due to the crosslinking of the gum is an important environmental issue. One solution proposed in this study consists in the integration of recycled tire crumb (GTR) in the design of plastic products aiming for a good impact, sound and vibration damping. Our work focused on the design and characterization of two types of materials : 1) Thermoplastic/GTR composites with two different thermoplastic matrix (TP) : vinyl acetate (EVA) and polypropylene (PP)processed by extrusion/injection, 2) plates made from 100 % GTR crumb processed by sintering. The quality of the TP/GTR interface was estimated with a Scanning Electron Microscope SEM. The influence of the GTR fillers on the TP matrix crystallinity was evaluated by DSC. Tensile test determined the Young’s modulus in tension, the yield point and the elongation at break. The vibration damping has been characterized by Dynamic Mechanical Analysis (DMA) with the determination of loss factor η on a wide range of temperatures to allow the construction of master curves frequency (frequency/temperature equivalence WLF). The shock damping was determined by an intrumentad drop test. The sound absorption coefficient was measured using a Kundt tube using the two microphones method. These different means of characterization showed that the vibration damping and impact energy absorption was increased by the incorporation of GTR fillers in a TP matrix. The study of PP/GTR blends revealed the influence of the internal damages of the molded specimens on the shock absorption mechanisms. Plates consisting of sintered GTR showed good cohesion and excellent shock absorption properties. The sound absorption coefficient only proved interesting in the vicinity of the resonance of various plates being tested.

De nos jours, le béton est le matériau de construction le plus utilisé dans le monde en raison de ses performances mécaniques, sa facilité de mise en oeuvre, son coût compétitif et sa « recyclabilité ». Toutefois, compte tenu de son caractère fragile en terme mécanique et de sa faible résistance à la traction, il est souvent renforcé par des armatures métalliques qui lui confèrent une bonne ténacité et une meilleure aptitude à supporter les efforts de traction. Ce composite béton-armature ne peut cependant assurer efficacement son rôle que si les deux composants sont étroitement liés l’un à l’autre. C’est donc dans la qualité de l’adhérence que réside l’efficacité du transfert des efforts entre les deux matériaux. Or, dès la mise en place des ouvrages en béton armé et pendant toute la durée de leur exploitation, différentes actions et agents agresseurs peuvent modifier la qualité de cette adhérence. Il peut s’agir de phénomènes naturels comme le gel/dégel et l’action du dioxyde de carbone atmosphérique, ou des sollicitations accidentelles comme l’incendie ou encore l’action de certains agents spécifiques comme les chlorures et les sulfates. Notre objectif dans cette thèse est de qualifier les modifications d’adhérence qui résultent de quatre types de sollicitations couramment rencontrées dans la vie des ouvrages en béton armé: l’effet des températures élevées, l’effet de la carbonatation, l’effet des cycles gel/dégel, l’effet de la corrosion. Nous évaluons la qualité de l’adhérence par la mesure de la résistance à l’arrachement et par l’analyse du comportement résiduel sous sollicitation mécanique. La technique d’émission acoustique est utilisée pour localiser en temps réel, l’endommagement du matériau sous sollicitation. Les applications de notre étude concernent non seulement les armatures et inserts classiques du béton armé mais aussi les nombreux dispositifs constructifs des structures mixtes acier – béton qui utilisent les liaisons par goujons pour relier les deux matériaux. / Nowadays, concrete is the most used construction material in the world because of its mechanical performances, its ability to be molded or cast, its competitive cost and its recyclability. However, concrete has a low ductility and a relatively low tensile strength compared to other construction materials. Therefore, concrete is often reinforced by steel rebars to improve the ductility and tensile strength. Nevertheless, to make reinforced concrete being highly efficient material, the two components need to be correctly bonded each to other. The bond quality the efficiency of the force transfer between rebar and concrete surrounding ensures. In fact, since the casting of concrete and during the service life of reinforced concrete structure, various actions such corrosion action, freeze/thaw attack and chemical attack etc. may affect the bond quality. The objective of this PhD research work is to qualify the changes of adhesion property causing by four types of action which frequently takes place in the service life of reinforced concrete structures: the effect of high temperatures, the effect of carbonation, the effect of cycles freeze/thaw, the effect of corrosion. The concrete-rebar bond quality is evaluated by doing pull-out tests under static mechanical action and measuring the bond strength and analyzing residual behaviour. Moreover, the acoustic emission technique is used to locate the cracks and evaluate the cracking evolution in real time. The founding of this study can be also extended to apply to other concrete-steel structures like composite structures in which headed studs are used to connect steel profiles to concrete.

Un nouveau code de simulation numérique pour la propagation des ondes de choc acoustiques dans des géométries complexes a été développé. Le point de départ a été la méthode de Galerkin discontinu qui utilise des maillages non structurés (ici des éléments triangulaires), particulièrement adaptés aux géométries complexes. Cependant, cette discrétisation conduit à l'apparition d'oscillation de Gibbs. Pour pallier ce problème, nous avons choisi d'introduire de la viscosité artificielle au voisinage des chocs. Cela a nécessité le développement de trois outils originaux : (i) un nouveau détecteur de choc sensible aux ondes de chocs acoustiques sur des maillages non structurés, (ii) un nouveau terme de viscosité artificielle dans les équations de l'acoustique non linéaire défini élément par élément et (iii) un nouveau terme permettant de régler le niveau de viscosité locale à partir du raidissement des fronts d'onde. Le code de calcul a été utilisé pour étudier deux configurations différentes. La première concerne la réflexion d'ondes de choc acoustiques sur des surfaces rigides. Différents régimes de réflexion ont alors été observés allant, de la réflexion classique de Snell Descartes jusqu'à celui dit de réflexion faible de Von Neumann. La deuxième configuration était consacrée à la focalisation d'ondes de choc acoustiques produites par un transducteur à haute intensité (comme ceux utilisés en HIFU). Un soin particulier a été pris pour étudier le calcul de l'intensité et pour étudier l'interaction entre les ondes de choc et des obstacles placés dans la région du foyer. / A new numerical solver for the propagation of acoustical shock waves in complex geometry has been developed. This is done starting from the discontinuous Galerkin method. This method is based on unstructured mesh (triangular elements here), and so, naturally it is well-adapted for complex geometries. Nevertheless, the discretization induces Gibbs oscillations. To manage this problem, we choose to introduce some artificial viscosity only in the vicinity of the shocks. This necessitates the development of three original tools. First of all, a new shock sensor for unstructured mesh sensitive to acoustical shock waves has been designed. It senses where the local artificial viscosity has to be introduced thanks to a reformulation of a new element centred smooth artificial viscosity term in the equations. Finally, the amount of viscosity is computed by the introduction of an original notion of gradient factor linked to the steepening of the waveform. The numerical solver has been used to investigate two different physical situations. The first one is the nonlinear reflection of acoustical shock waves on rigid surfaces. Different regimes of reflection have been observed ranging from the linear Snell Descartes reflection to the weak von Neumann case. The second configuration deals with the focusing of shock waves produced by high intensity transducers (like in HIFU). Special attention has been given to the careful computation of intensity and to the interaction between the shock waves and obstacles in the region of the focus.

No description available.

As a musical instrument construction material, wood is both musically and aesthetically pleasing. Easy to work and abundant, it has traditionally been the material of choice. Unfortunately, wood is also a very inconsistent material. Due to great environmental and climatic variations, wooden specimens present large variations in their mechanical properties, even within species of a similar region. Surprisingly, an industry based entirely on acoustics has done very little to account for these variations. For this reason, manufactured wooden guitars are acoustically inconsistent. Previous work has shown that varying the dimensions of a guitar soundboard brace is a good method for taking into account variations in the mechanical properties of the wooden soundboard plate. In this thesis, the effects of a scalloped-shaped brace on the natural frequencies of a brace-plate system have been studied and tools have been developed in order to calculate the dimensions of the brace required to account for variations in the mechanical properties of the plate. It has been shown that scalloped braces can be used to modify two natural frequencies of a brace-plate system simultaneously. Furthermore, the most important criteria in modifying any given frequency of a brace-plate system is the mass and stiffness properties of the brace at the antinode of the given frequency’s associated modeshape. Subsequently, designing a brace for desired system natural frequencies, by taking into account the mechanical properties of the wooden plate, is an inverse eigenvalue problem. Since few methods exist for solving the inverse eigenvalue problem of general matrices, a new method based on the generalized Cayley-Hamilton theorem was proposed in the thesis. A further method, based on the determinant of the generalized eigenvalue problem was also presented. Both methods work well, although the determinant method is shown to be more efficient for partially described systems. Finally, experimental results were obtained for the natural frequencies of simply supported wooden plates, with and without a brace, as well as the inverse eigenvalue determinant method. Good correlation was found between theoretical and experimental results.