Orientador: José Roberto de França Arruda / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T16:52:35Z (GMT). No. of bitstreams: 1 Siviero_DiegoAzevedo_D.pdf: 6891079 bytes, checksum: 7f974a708ef3ffdbbf5d21dd4528a176 (MD5) Previous issue date: 2011 / Resumo: O controle da transmissão sonora em painéis é um problema que tem despertado a atenção das indústrias automobilísticas, aeronáutica e aeroespacial. As estratégias de controle de ruído passivo utilizadas com esta finalidade não apresentam boa eficiência em todo espectro audível, pois apesar de ser uma solução robusta, não é eficaz na absorção de ruídos de baixas frequências (menos de 1kHz). Este trabalho apresenta o desenvolvimento de um protótipo de isolador acústico híbrido que agrega elementos do tradicional controle passivo (material poroso, espuma de melamina mais especificamente) e do controle ativo de ruídos (transdutores piezelétricos comandados por um sinal elétrico conveniente) para complementar a eficiência de absorção sonora em baixas frequências. Como a medição da perda de transmissão sonora não pode ser realizada diretamente, este estudo também apresenta uma simulação computacional comprovando a possibilidade de se atuar ativamente em outras grandezas acústicas para se obter o controle indireto da perda de transmissão sonora. O algoritmo de controle utilizado neste trabalho é o Filtered-X LMS normalizado, implementado no domínio do tempo e no domínio da frequência. Após a comprovação da efetividade do controle na simulação, um tubo de ondas planas foi construído para teste e desenvolvimento do isolador proposto. Finalmente, o protótipo foi aplicado a um painel reforçado fixado em uma janela que divide duas câmaras acústicas (uma anecóica e outra reverberante) para medir a perda de transmissão sonora do conjunto. Os resultados apontam um considerável aumento na perda de transmissão das baixas frequências no tubo de ondas planas. A aplicação do isolador no painel reforçado não apontou resultados conclusivos / Abstract: The control of transmission loss through panels is a problem that has attracted the attention of automotive, aeronautical and aerospace industries. The passive noise control strategies used for this purposed does not have high efficiency in all audible spectrum, although it consists in a robust solution, it is not effective in low frequency absorb (below 1kHz). This work presents the development of an acoustic insulator prototype that combines traditional passive noise control elements (porous materials, melamine foam more specifically) with active noise elements (piezoelectric transducer driven by a convenient electric signal) to complement the sound absorbing in low frequencies. As the transmission loss measuring cannot be performed instantaneously, this study also presents a computational simulation showing the possibility of actuating actively in other acoustical quantities to obtain the indirect control of the sound transmission loss. The active control algorithm used in this research is the normalized Filtered-X LMS, implemented in time and frequency domains. After verification of the effectiveness of this controller in the simulation, a plane wave duct was built for testing and development of the proposed isolator. Finally, the prototype was applied to a reinforced panel placed in a window that divides two acoustic chambers (anechoic and reverberant) to measure the sound transmission loss of the assembly. The results showed an increase in the low frequency transmission loss when the isolator was tested in the plane wave duct. The tests with the reinforced plate did not show conclusive results / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica

The impact noise is a challenge to builders and designers because of the difficulty in the interruption of vibrations due to the rigidity of the connections between the structural elements. Many previous researches aimed at the development of methods to diminish its effects and among them the floating floor , constituted by the interposition of an elastic material between the flagstone and the final covering of the floor, has presented significant advantages in presenting a solution still in the project phase. The introduction of new materials in the market made it possible the development of this study, whose objectives were to measure and to compare the performance of these materials as isolators, as well as to determine the relative advantage to the cost/benefit criterion in the construction of systems with porcelanate and plated melamínico wooden final coverings, and the utilization of glass wool, recycled blankets of rubber (E.V.A. residues) and high density Styrofoam and polyethylene blanket as resilient materials. The experiments carried out at the Thermo-acoustic laboratory (LaTA) in the university, according to the methodology suggested by ISO 140/VI and VIII (except the specifications as to the size of the samples that were tested with 1m ²) and ISO 717-2, permitted the classification of the tested materials in terms of their performance while impact noise acoustic isolators, and the market research made it possible to establish a hierarchy in the cost/benefit aspect. / O ruído de impacto é um desafio para construtores e projetistas pela dificuldade que se encontra para a interrupção das vibrações decorrentes da rigidez dos vínculos entre os elementos estruturais. Diversos estudos científicos visaram o desenvolvimento de métodos para amenizar seus efeitos, dos quais o piso flutuante , composto pela interposição de material elástico entre a laje e o revestimento final, tem apresentado vantagens significativas porque apresenta a solução ainda na fase do projeto. O surgimento de novos materiais no mercado ensejou a realização deste trabalho que teve como objetivo medir e comparar o desempenho desses materiais como isolantes, além de determinar a vantagem relativa no critério custo/benefício, na montagem de sistemas com revestimentos finais de porcelanato e laminado melamínico de madeira, e a utilização de lã de vidro, mantas de borracha reciclada (resíduos de E.V.A.), isopor de alta densidade e manta de polietileno como materiais resilientes. Os ensaios realizados no Laboratório de Termo-Acústica (LaTA) da UFSM de acordo com a metodologia preconizada pelas ISO 140/VI e VIII (exceto as especificações quanto ao tamanho das amostras que foram testadas com 1m²) e ISO 717-2 permitiram escalonar os materiais testados quanto aos seus desempenhos como isolantes acústicos ao ruído de impacto e a pesquisa mercadológica possibilitou determinar uma hierarquização no aspecto custo/benefício.

A simple, effective design for enclosing portable generators to reduce the radiated noise is an idea that seems to be desired by the consumers in this market. This investigation is to determine the feasibility of producing such an enclosure for a generator. Several engineering aspects are incorporated in the design of the enclosure. The first, and probably the most paramount, are the acoustical effects of the enclosure itself. The investigation follows the theories for insertion loss of a close fitting enclosure. The thesis examines the system behavior of a close fitting enclosure that most acoustic text books ignore and how the material stiffness, density and source-to-enclosure distance affect the insertion loss and effectiveness of the enclosure. Measured and theoretical sound pressure level around the generator before and after the application of the enclosure are presented using standards described by ISO standard 1344. The second important consideration for the enclosure design involves the heat transfer characteristics. The requirements of cooling air to the generator are discussed. Also presented are some acoustic design considerations to prevent any "direct line of sight" to any of the necessary openings which will help in the overall insertion loss. The use of an optimal engineering design technique is presented, demonstrating its strengths and weakness in this application. The optimization method used for the study is the Hooke and Jeeves, or pattern search method. This method solved for the optimum material properties in approximately 30 iterations depending on the initial starting points and the desired weighting parameters. / Master of Science

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The proposal of this project is analyze and compare different behaviors of natural floating wood floors, submitted an impact noise with several compositions, used in construction industry. The tests were done on the Thermo-acoustic Laboratory of UFSM, in according with the methods specified in the regulations ISO 140/ VI and ISO 717-2. The tests were done, using layers of wood, in different compositions and resilient materials. The results were analyzed, confronting the material with same characteristics but with different composition. The resilient materials used in the tests were: glass wool, polyethylene and polystyrene. The analysis of the results was done grouping the similar materials with different compositions. / Esta pesquisa faz uma análise e comparação de diferentes sistemas de pisos flutuantes de madeira natural submetidos a ruído de impacto, em diferentes composições utilizadas na indústria da construção civil. Os ensaios foram realizados nas câmaras para medir ruído de impacto do Laboratório de Termoacústica da UFSM, conforme metodologias especificadas nas Normas Internacionais ISO 140/ VI e ISO 717-2. Foram ensaiadas amostras de revestimento do tipo tábua corrida e taco, ambos de madeira natural, em diferentes composições quanto ao revestimento e o material resiliente. Os materiais resilientes utilizados nas composições foram lã de vidro, polietileno expandido e poliestireno expandido (isopor). A análise dos resultados obtidos foi feita agrupando-se materiais semelhantes nas diferentes composições.

Dans le domaine de l’acoustique du bâtiment, la structuredes constructions en bois est légère et ses capacités d’isolementacoustique sont faibles en particulier pour les basses fréquencesen comparaison à d’autres techniques de constructioncomme le béton. Les travaux de cette thèse se donc sont centréssur l’élaboration d’un outil prédictif visant à déterminer lesperformances acoustiques des planchers solivés en bois afin decompléter les outils prédictifs actuellement sur le marché. Laméthode des éléments finis est adaptée pour résoudre ce problèmevibro-acoustique car le comportement basses fréquencesest de type modal. Pour gagner en temps de calcul, une résolutionmixte éléments finis – formulation intégrale d’Huygens etdifférentes optimisations ont été mises en place. Grâce à l’utilisationde la méthode des éléments finis, il a été possible demettre en évidence des résonances de ce problème couplé quifont chuter localement la valeur de l’affaiblissement ; celles-cine peuvent être prises en compte par la méthode des matricesde transfert. Néanmoins, ces deux méthodes fournissent des alluresmoyennes de courbes d’affaiblissement équivalentes, enparticulier lors d’une étude en tiers d’octave. Pour aborder leproblème des transmissions latérales, nous avons montré lafaisabilité de la détermination expérimentale des propriétés mécaniqueséquivalentes d’un élément de jonction courant entreles planchers et les murs : le sabot métallique. Un modèle mécaniquesimplifié par éléments finis permet ainsi un couplagemécanique entre les solives et les poutres en intégrant les effetslocaux de dissipation présents pour ce type de jonction. / In building acoustics, the structure of wooden construction islightweight and sound insulation at low frequency are weakcompared to other construction techniques like concrete. Thework of this thesis is focus on the development of predictivetools for determining the acoustic performance of wooden joistfloors to complete the existing predictive tools available on themarket. The finite element method (FEM) is adapted to solvethis vibro-acoustic problem because behavior at low frequenciesis modal. To save computation time, a mixed resolutionfinite element with Huygens integral formulations and severaloptimizations were implemented. We could note the interest ofthe FEM : we observed that resonances of the coupled systemdrive locally down the value of the TL, which can not be takeninto account by the method of transfer matrices. However, wenote that these two methods provide equivalent average curveshapes of TL’s spectrum. To deal with the problem of flankingtransmissions, penalizing the lightweight construction, we experimentalydetermine the mechanical properties of a equivalentjunction element between floors and walls : the wood joisthanger. Through a simplified mechanical model, this numericalfinite element model allows a mechanical coupling between thejoists and beams by incorporating the local effects of dissipationpresent for this type of junction.