La propagation des ondes acoustiques ou élastiques dans un milieu fini à faible atténuation se traduit par des signaux mesurés de longue durée (réverbération). Dans les techniques de contrôle non destructif et imagerie conventionnelles, seuls les premiers paquets d’ondes sont ordinairement exploités et l’information potentiellement contenue dans les codas de réverbération est alors perdue. Le travail présenté dans cette thèse a pour objectif d’exploiter le comportement d’ensemble des codas enregistrées dans des structures de type plaques, afin d’extraire le maximum d’information à partir d’un nombre limité de capteurs et traitement simple. Nous avons développé des modèles statistiques permettant de prévoir le comportement des ondes acoustiques réverbérantes dans une plaque (sous la forme de moyennes d’ensemble), à partir d’un ensemble limité de paramètres accessibles expérimentalement. Ainsi, il est montré que les moyennes des enveloppes, des corrélations ou de l’intégrale dite de Schroeder des signaux de réverbération reçus par quelques points contiennent des informations potentiellement utiles sur les propriétés structurelles du milieu, des sources ou des défauts. Après une validation numérique et expérimentale des modèles, des applications potentielles sont présentées telles que l’estimation de propriétés structurelles d’une plaque ou la localisation d’une source. La particularité de ces estimations est qu’elles ne nécessitent pas de mesure de temps, ni de synchronisation entre les capteurs, ce qui pourrait autoriser une implémentation avec peu de ressources embarquées. Ce type de méthode pourrait également être utilisé pour caractériser un défaut dans une structure réverbérante, de façon éventuellement complémentaire aux techniques classiques de CND et contrôle-santé de structures. / The propagation of acoustic and elastic waves in a finite media with low attenuation leads to measured signals of long durations (reverberation). In conventional techniques for non-destructive testing and imaging, only the first wave packets are usually exploited, and the information potentially contained in reverberation codas is lost. The work presented in this thesis aims to exploit the overall behavior of codas recorded in plate-like structures, in order to extract the maximum information from a limited number of sensors and simple processing. We have developed statistical models to predict the behavior of reverberant acoustic waves in a plate (in the form of ensemble-averages), from a limited set of experimentally accessible parameters. Thus, it is shown that theoretical expressions for the mathematical expectations of the envelopes, the correlation functions or the so-called Schroeder’s integral of reverberant signals received at some points contain potentially useful information about the structural properties of the medium, the sources or the defects. After numerical and experimental validation, potential applications are presented, such as the estimate of structural properties of a plate or source location. In addition, these techniques do not require any time measurement or even trigger synchronization between the input channels of instrumentation, thus implying low hardware constraints. Such methods could also be used to characterize a defect in a reverberant structure and can be considered as complementary to conventional NDT techniques and structural health monitoring.

This thesis contributes new algorithms and implementations for particle filter-based target tracking. From an algorithmic perspective, modifications that improve a batch-based acoustic direction-of-arrival (DOA), multi-target, particle filter tracker are presented. The main improvements are reduced execution time and increased robustness to target maneuvers. The key feature of the batch-based tracker is an image template-matching approach that handles data association and clutter in measurements. The particle filter tracker is compared to an extended Kalman filter~(EKF) and a Laplacian filter and is shown to perform better for maneuvering targets. Using an approach similar to the acoustic tracker, a radar range-only tracker is also developed. This includes developing the state update and observation models, and proving observability for a batch of range measurements. From an implementation perspective, this thesis provides new low-power and real-time implementations for particle filters. First, to achieve a very low-power implementation, two mixed-mode implementation strategies that use analog and digital components are developed. The mixed-mode implementations use analog, multiple-input translinear element (MITE) networks to realize nonlinear functions. The power dissipated in the mixed-mode implementation of a particle filter-based, bearings-only tracker is compared to a digital implementation that uses the CORDIC algorithm to realize the nonlinear functions. The mixed-mode method that uses predominantly analog components is shown to provide a factor of twenty improvement in power savings compared to a digital implementation. Next, real-time implementation strategies for the batch-based acoustic DOA tracker are developed. The characteristics of the digital implementation of the tracker are quantified using digital signal processor (DSP) and field-programmable gate array (FPGA) implementations. The FPGA implementation uses a soft-core or hard-core processor to implement the Newton search in the particle proposal stage. A MITE implementation of the nonlinear DOA update function in the tracker is also presented.

La prédiction du bruit de roulement ferroviaire est en enjeu majeur pour la maitrise des nuisances sonores. Au point de contact roue/rail, la roue et la voie sont excités de manière dynamique, ce qui enclenche le rayonnement du bruit de roulement. Les réponses vibratoires au point de contact ainsi que les taux de décroissance des ondes sont des données primordiales pour simuler de manière précise le bruit de roulement. Or, la dimension infinie de la voie ferrée conduit bien souvent à des modèles éléments finis coûteux et non adaptés à la recherche de solutions innovantes. La thèse a pour objectifs de proposer un modèle vibratoire de voie en éléments finis qui prenne en compte la dimension infinie périodique de la voie, mais aussi d’inclure une portion de voie non-périodique sur laquelle des solutions anti-vibratiles peuvent être testées. La propagation des vibrations est exprimée sous la forme d’une décomposition en ondes par la méthode WFE (Wave Finite Element). Le calcul de la réponse vibratoire de la voie périodique infinie est obtenu à partir du déplacement d’une cellule physique longue d’environ 0.6 m. Pour réduire les temps de calcul nécessaires à sa condensation dynamique, une méthode de bi-périodisation est proposée. Le couplage entre les méthodes éléments finis et WFE est développé pour prendre en considération les supports élastiques dans cette cellule. Les comparaisons avec des mobilités expérimentales ainsi que des taux de décroissance montrent un très bon accord calculs-mesures. Enfin, le modèle développé dans cette thèse a permis de tester l’efficacité d’une solution anti-vibratile innovante développée au sein du projet CERVIFER. Celle-ci offre un comportement bi-mode, elle assouplit les supports autour de la roue préservant ainsi l’infrastructure, mais elle rigidifie les supports loin de la roue pour augmenter les taux de décroissance. Les résultats numériques se révèlent prometteurs en termes d’efficacité du dispositif et entrevoient une poursuite du développement de cette solution anti-vibratile. / Railway noise is a critical issue concerning environmental noise. At the wheel/rail contact point, both the wheel and the track are dynamically excited and vibrate together to emit the well known rolling noise. The point receptance of the rail and the track decay rates are important quantities to accurately predict wheel-rail noise emission. However, the infinite dimension of the track leads to cumbersome numerical finite-element (FE) models and not adapted to assist the research of innovative solutions. The goals of this thesis are to build an efficient numerical model for calculating the vibration from an infinite railway track, but also to include a central non-periodic part with the aim of testing anti-vibration solutions. The vibration propagation along the track is expressed as a sum of different waves using the WFEM (Wave Finite Element Method). The displacements of a 0.6 m unit cell lead to the computation of the whole track. To reduce the dynamic condensation of this cell, a bi-periodic method is proposed in this thesis. The FEM - WFEM coupling is proposed to easily include elastic supports inside the unit cell. Results show a good correlation between test and calculation. Finally, the model proposed in this thesis was used to test the efficiency of an innovative anti-vibration solution developed within the CERVIFER project. It is a dual mode device which makes the supports softer around the wheel to protect the infrastructure, and stiffer away from the wheel to increase the track decay rates. The numerical results revealed to be really promising, and they will permit to pursue the development of this anti-vibration solution.

Orientador: Jose Roberto de França Arruda / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-05T19:37:58Z (GMT). No. of bitstreams: 1 Nunes_Osmar_M.pdf: 3751336 bytes, checksum: 2fc3b9c3cc2af03451617cae482065d1 (MD5) Previous issue date: 2005 / Resumo: As características acústicas de compressores herméticos têm se tomado cada vez mais críticas no projeto destes equipamentos e as predições destas características ao longo do projeto, obrigatórias para a adequação deste produto às condições de consumo. Este trabalho apresenta um método de avaliação vibro-acústica de compressores herméticos através de modelos de elementos finitos. Para estas avaliações, forças harmônicas com amplitudes unitárias são aplicadas em pontos específicos da carcaça e os seus campos de pressão sonora resultantes são calculados sob condições anecóicas, sendo que, estas condições foram modeladas através de elementos infinitos acústicos. Através deste método, é possível obter numericamente a potência acústica irradiada por diferentes versões de projeto, compará-las, escolher a versão mais adequada e, se for o caso, obter informações para direcionar modificações em uma versão para a sua adequação aos níveis de potência sonora exigidos. O trabalho mostra as verificações executadas durante o processo de desenvolvimento desta metodologia como análise modal, análises de convergência e comparações de resultados numéricos com analíticos através de modelos de fontes omnidirecionais. Para a verificação de seu funcionamento, são apresentadas as análises vibro-acústicas numéricas de duas versões de compressor. Além disto, dois protótipos com características semelhantes aos modelos analisados foram testados em câmara reverberante para a obtenção de suas potências sonoras e a comparação com os resultados numéricos. Os resultados obtidos desta comparação mostraram boas correlações entre numérico e experimental e fornecem subsídios para avaliar o desempenho entre as diferentes versões de projeto / Abstract: The importance of the acoustic characteristics in design of hermetic compressors has increased along the years. As a consequence, to predict these characteristics in the design phase is mandatory for this product to meet the consumption requirements. This work presents a method for evaluating the vibration and acoustic characteristics of hermetic compressors through finite element models. To perform these evaluations, harmonic forces with unitary amplitudes are applied in specific locations of the compressor housing and their resulting acoustic pressure fields are ca1culated under anechoic conditions obtained through the acoustic infinite elements. By using this method, it is possible to numerically obtain the acoustic power level irradiated by different versions of design in order to compare them and to choose the most adequate version. With the use of this method it is also possible to obtain information to guide modifications in the design and suit it to desired acoustic power levels. This work presents the verifications performed during the development process of this methodology such as modal analysis, convergence analysis and comparisons between analytical and numerical results by using omnidirectional sources. To validate this methodology, the acoustic numerical analysis of two versions of compressor' s housing was presented. Furthermore, two prototypes similar to the models characteristics were submitted to tests in reverberant chamber for obtaining their acoustic power levels and compared with the numerical results. The obtained results of this comparison presented a satisfactory correlation between numerical and experimental results and provided relevant information to evaluate different design versions / Mestrado / Mecanica Computacional / Mestre em Engenharia Mecânica

L'objectif de cette thèse consiste en l'étude d'une stratégie de contrôle actif à faible autorité avec comme application le contrôle actif du rayonnement acoustique d'une plaque. Depuis l'essor du contrôle actif, son application aux problèmes acoustiques et vibracoustiques a été investiguée par de nombreux chercheurs, exploitant soit la théorie du contrôle optimal, soit des approches originales basées plus particulièrement sur la physique. Des notions spécifiques au contrôle vibroacoustique ont été développées comme, par exemple, les modes radiatifs pouvant caractériser le rayonnement acoustique d'une plaque d'une manière adaptée au contrôle. <p>Le contrôle actif à faible autorité, pour lequel le Laboratoire de Structures Actives a développé une expertise dans le domaine de l'amortissement et du contrôle actif des vibrations, est une solution attractive par sa simplicité de mise en oeuvre. Le plus souvent implémenté sous la forme d'un contrôle décentralisé constitué de boucles indépendantes, le contrôle à faible autorité bénéficie de certaines garanties de stabilité et de robustesse. <p>Bien que notre stratégie de contrôle puisse s'appliquer à n'importe quel type de plaque, l'application considérée dans ce travail a été motivée par le contexte socio-économique actuel en rapport avec les nuisances acoustiques. Il était en effet intéressant d'évaluer la stratégie de contrôle pour le problème de la transmission acoustique d'un vitrage. La stratégie de contrôle se divise en deux étapes. Tout d'abord le développement d'un capteur unique destiné à fournir une mesure représentative du bruit rayonné par une plaque en basse fréquence. Deux capteurs de vitesse volumétrique (l'un discret, l'autre distribué) ont ainsi été développés et évalués expérimentalement. <p>Ensuite, une procédure d'optimisation de l'emplacement d'un ensemble d'actionneurs pilotés en parallèle est proposée. L'objectif de cette phase d'optimisation est de forcer la réponse fréquentielle du système à posséder les propriétés d'un système colocalisé. La stratégie de contrôle est ensuite évaluée sur deux structures expérimentales. <p><p>/ This thesis is concerned with a low authority active control strategy applied to the sound radiation control of a baffled plate. Since the development of active control ,numerous researchers have studied its application to acoustical or vibroacoustical problems using either the modern control theory or other methods based rather on the understanding of the physics of the problem. Vibroacoustical active control has lead to the definition of radiation modes allowing to describe the radiated sound of a plate in an appropriate manner for active control purposes. <p>Low autorithy control (LAC), for which the Active Structures Laboratory has gained an expertise for active vibration control applications is an interesting solution for its implementation simplicity. Most of the time it consists of several decentralized control loops, and benefits from guaranteed stability and robustness properties. Although our control strategy can be applied to any kind of plates, the application considered here has been motivated by the present socio-economical context related to noise annoyances. The active control strategy has been applied the problem of the sound transmission loss of glass plates (windows). This strategy is in two steps :first a volume velocity sensor is developed as to give a measure representative of the radiated sound at low frequencies. <p>Two sensors have been developed (one discrete and one distributed) and experimentally tested. Next, an optimisation strategy is proposed which allow to locate on the plate a set of several actuators driven in parallel. The goal of this optimisation task is to obtain an open-loop frequency response which behave like a collocated system. The control strategy is finally evaluated on two plate structures. / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

This master's thesis deals with design and implementation of modular system for two-way loudspeaker system's characteristics. Work focus mainly on the enclosure geometry and speaker placement. The individual modules of the system were designed and then implemented. Furthermore, the characteristics of these modules were measured and laboratory tasks using these modules were elaborated.

Treize Etudes Pour L?Orchestre is a thirteen-movement symphonic work for full contemporary orchestra. The purpose of this work has been to develop a sonic exploration of textural possibilities through the orchestral medium. The motivic materials of the whole piece were first utilized in pieces for one piano, piano and cello and two pianos combinations These smaller pieces ahs been included in the appendix section of this work. The orchestral work does not represent an orchestration of the smaller pieces, but an expansion of the material into different textural studies. Preparation for this work includes the study of twelve different bird sounds, first recorded and later musically transcribed to create thematic materials and secondary materials for this work; the study of production of fabric of sounds representing color spectrums and intensity through sound tapestries, and the sonic representation of water, a starry dark night and the jungle. The Treize Etudes Pour L?Orchestre is formally a through-composed work. The different musical materials created as motive unity of the whole work have been developed throughout it by means of using a variety of compositional devices and techniques including Schoenberg?s Klangfarbenmelodie, Messiaen?s ?Language Musicale?, Ives? quadraphonic effect, and Samuel Adler?s sound curtain technique, and, the use of folk-like materials; all within the parameters of acoustic instrumentation.

Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / O presente trabalho aborda a modelagem numérica da propagação das ondas sonoras em salas, a partir da avaliação do campo de pressão sonora quadrática na sala. Esta pesquisa apresenta um modelo computacional, baseado na abordagem modal de salas com geometria retangular, que melhora o desempenho do programa de simulação numérica de acústica de salas RAIOS 3 para as baixas frequencias. Inicialmente, foi feita uma análise modal teórica e experimental de uma sala retangular de paredes rígidas e não rígidas, onde se calcula pressão sonora de todos os modos como função da posição e do tempo. Para isso, determinam-se os números de onda e frequência de cada modo, ou seja, os autovalores e as autofrequências. O desempenho do modelo é avaliado a partir dos resultados obtidos com uma sala retangular e validado utilizando dados experimentais do PTB (Physikalisch-Technische Bundesanstalt), Alemanha, na intercomparação denominada Round Robin 3, fase 3. Os principais resultados foram obtidos pelo cálculo dos seguintes parâmetros: tempo de reverberação, (T30), fator de clareza (C80), difinição (D50) e o tempo de decaimento inicial, (EDT). / This article discusses the numerical modeling of the propagation of sound waves in rooms, from the assessment of the field of sound pressure quadratic in the room. This research presents a computational model, based on modal approach of rooms with rectangular geometry, which improves the performance of the program for numerical simulation of acoustics of rooms RAIOS 3 for low frequencies. Initially, there was a theoretical and experimental modal analysis of a rectangular room for non-rigid and rigid walls, where an estimated sound pressure of all modes as a function of place and time. For this, is determining of the wavenumbers and frequencies of each mode, namely the eigenvalues and eigenfrequencies. The performance of the model is assessed from results with a rec tangular room and validated using measurement data of the PTB (Physikalisch-Technische Bundesanstalt), Germany, an inter-comparison named Round Robin 3, phase - 3. The main results were obtained by calculating the following parameters: reverberation time, (T30), clarity factor, (C80), difinition, (D50) and early decay time.

O presente trabalho consiste em uma pesquisa em ensino de física, mais específicamente em ensino de acústica. Foi aplicada uma sequência didática em uma turma de primeiro ano do ensino médio, contextualizando os conceitos de acústica na audição de música e na vivência com a poluição sonora e utilizando como marco teórico a teoria da aprendizagem significativa desenvolvida por Ausubel. O objetivo foi aplicar a sequência didática para obter dados relativos à aprendizagem dos conceitos, analisando se foram, ou não, facilitadores significativos. Utilizou-se a gravação de áudio das aulas e um questionário, aplicado no início e no fim da sequência, para que se possa analisar o antes e depois, além do diário de campo, registrado pelo autor. A sequência foi composta por seis aulas de quarenta e cinco minútos. A análise dos dados obtidos aponta para uma facilitação da aprendizagem significativa de Acústica. Entretanto, seria importante dar continuidade à aplicação dos instrumentos de coleta de dados a um público mais numeroso e com perfis de turmas mais diversificados, para que os resultados propiciem resultados mais conclusivos e abrangentes. / The present work consists of a research in physics teaching, more specifically in acoustic teaching. A didactic sequence was applied in a first year high school class, contextualizing the concepts of acoustics in listening to music and living with noise pollution and using as theoretical framework the theory of meaningful learning developed by Ausubel. The objective was to apply the didactic sequence to obtain data regarding the learning of the concepts, analyzing whether or not they were significant facilitators. The audio recording of the classes and a questionnaire, applied at the beginning and at the end of the sequence, were used to analyze the before and after, besides the field diary, recorded by the author. The sequence consisted of six forty-five minute classes. The analysis of the data points to a facilitation of the significant learning of Acoustics. However, it would be important to continue the application of the data collection instruments to a larger audience and with more diverse class profiles, so that the results can lead to more conclusive and comprehensive results.

Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / O presente trabalho aborda a modelagem numérica da propagação das ondas sonoras em salas, a partir da avaliação do campo de pressão sonora quadrática na sala. Esta pesquisa apresenta um modelo computacional, baseado na abordagem modal de salas com geometria retangular, que melhora o desempenho do programa de simulação numérica de acústica de salas RAIOS 3 para as baixas frequencias. Inicialmente, foi feita uma análise modal teórica e experimental de uma sala retangular de paredes rígidas e não rígidas, onde se calcula pressão sonora de todos os modos como função da posição e do tempo. Para isso, determinam-se os números de onda e frequência de cada modo, ou seja, os autovalores e as autofrequências. O desempenho do modelo é avaliado a partir dos resultados obtidos com uma sala retangular e validado utilizando dados experimentais do PTB (Physikalisch-Technische Bundesanstalt), Alemanha, na intercomparação denominada Round Robin 3, fase 3. Os principais resultados foram obtidos pelo cálculo dos seguintes parâmetros: tempo de reverberação, (T30), fator de clareza (C80), difinição (D50) e o tempo de decaimento inicial, (EDT). / This article discusses the numerical modeling of the propagation of sound waves in rooms, from the assessment of the field of sound pressure quadratic in the room. This research presents a computational model, based on modal approach of rooms with rectangular geometry, which improves the performance of the program for numerical simulation of acoustics of rooms RAIOS 3 for low frequencies. Initially, there was a theoretical and experimental modal analysis of a rectangular room for non-rigid and rigid walls, where an estimated sound pressure of all modes as a function of place and time. For this, is determining of the wavenumbers and frequencies of each mode, namely the eigenvalues and eigenfrequencies. The performance of the model is assessed from results with a rec tangular room and validated using measurement data of the PTB (Physikalisch-Technische Bundesanstalt), Germany, an inter-comparison named Round Robin 3, phase - 3. The main results were obtained by calculating the following parameters: reverberation time, (T30), clarity factor, (C80), difinition, (D50) and early decay time.