This thesis contains three papers investigating problems of interest for noise control in ducts. The first part of this thesis treats the sound propagation in rectangular ducts with flexible walls. Various experimental techniques are performed to measure the internal sound propagation and radiation to the surrounding. An analytical model is derived to calculate the coupled propagation wavenumber and radiated sound power. The two-port formalism is used. The second part starts with the sound propagation in open ended circular straight pipe with airflow (a tailpipe). Various aspects such as: acoustic damping, reflection and transmission at the open termination are investigated. Sound absorption due to vorticity shed at the opening is also treated. The geometry of the opening is then modified (oblique cuts, diffusers) and comparisons with the reference straight pipe is made for the sound transmission and flow induced noise generation. The effect of an upstream bend close to the opening is also investigated. In the third part the acoustic impedance of perforated plates are investigated. In particular the application to small perforation ratios ( ≈ 1% ) and holes or slits with apertures of sub-millimetre size, so called micro-perforated plates, are of interest. Linear and non-linear regimes are investigated. A model is derived to calculate the linear acoustic impedance of perforated elements. / QC 20101111

Intake and Exhaust system noise makes a huge contribution to the interior and exterior noise of automobiles. There are a number of linear acoustic tools developed by institutions and industries to predict the acoustic properties of intake and exhaust systems. The present project discusses and validates, through measurements, the proper modelling of these systems using BOOST-SID and discusses the ideas to properly convert a geometrical model of an exhaust muffler to an acoustic model. The various elements and their properties are also discussed. When it comes to Acoustic properties there are several parameters that describe the performance of a muffler, the Transmission Loss (TL) can be useful to check the validity of a mathematical model but when we want to predict the actual acoustic behavior of a component after it is installed in a system and subjected to operating conditions then we have to determine other properties like Attenuation, Insertion loss etc,. Zero flow and Mean flow (M=0.12) measurements of these properties were carried out for mufflers ranging from simple expansion chambers to complex geometry using two approaches 1) Two Load technique 2) Two Source location technique. For both these cases, the measured transmission losses were compared to those obtained from BOOST-SID models. The measured acoustic properties compared well with the simulated model for almost all the cases.

The noise propagating through the truck exhaust system is often attenuated by after treatment systems including truck silencers. The acoustic simulation of the truck silencers is usually based on pressure acoustics which does not include the influence of background flow. However, background flow can affect the acoustic attenuation ability of the truck silencers a lot. This thesis presents a simulation method for investigating the influence of the background mean flow on the silencers. In this method, the fluid information is first simulated with CFD software STAR-CCM+. The fluid data is then imported into COMSOL to conduct acoustic simulation using Linearized Navier-Stokes modulus. Flow noise is not simulated in this method in order to well capture the background mean flow's effect on the performance of silencer in a relatively short calculation time. Two simple silencer model groups are studied to validate this method. The first is a Helmholtz resonator. Another model group is expansion chambers with different setups. The sensitivity of the model towards different model setup is also studied. In the last part of the work, the method is applied to a common truck silencer model CAS1 F1gen, when this method counters challenge of high calculation load. A hybrid method is then developed, combining pressure acoustics and Linearized Navier-Stokes study, to simplify the method, reduce calculation time and at the same time capture the background mean flow's influence on silencers. / Bullret som fortplantar sig genom lastbilens avgassystem dämpas ofta av efterbehandlingssystem inklusive lastbilsljuddämpare. Den akustiska simuleringen av lastbilens ljuddämpare baseras vanligtvis på tryckakustik som inte inkluderar påverkan av bakgrundsflödet. Bakgrundsflödet kan dock påverka lastbilsljuddämparnas akustiska dämpningsförmåga mycket. Denna avhandling presenterar en simuleringsmetod för att undersöka påverkan av bakgrundsmedelflödet på ljuddämparna. I den här metoden simuleras vätskeinformationen först med CFD-programvaran STAR-CCM+. Vätskedata importeras sedan till COMSOL för att genomföra akustisk simulering med linjär Navier-Stokes modul. Flödesbrus simuleras inte i denna metod för att väl fånga bakgrundsmedelflödets effekt på ljuddämparens prestanda på en relativt kort beräkningstid. Två enkla ljuddämparmodellgrupper studeras för att validera denna metod. Den första är en Helmholtz-resonator. En annan modellgrupp är expansionskammare med olika inställningar. Modellens känslighet mot olika modellupplägg studeras också. I den sista delen av arbetet tillämpas metoden på en vanlig lastbilsljuddämpare modell CAS1 F1gen, då denna metod motverkar utmaning med hög beräkningsbelastning. En hybridmetod utvecklas sedan, som kombinerar tryckakustik och linjäriserad Navier-Stokes-studie, för att förenkla metoden, minska beräkningstiden och samtidigt fånga bakgrundsmedelflödets påverkan på ljuddämpare.

Les systèmes d’information actuels reposent fortement sur les technologies micro-ondes utilisées pour les communications hertziennes. L’amélioration des performances des MEMS radio fréquence aptes à fonctionner dans la bande X (8 GHz et 12 GHz) est un enjeu important pour des applications de télécommunications mais aussi pour les applications radar. Pour y parvenir l’intégration de matériaux ferroélectriques à haute constante diélectrique est requise. Les matériaux qui possèdent de telles propriétés et qui sont les plus adaptés, sont les composés qui dérivent de la structure pérovskite. Intégrer ce type de matériaux dans des commutateurs radio-fréquence (MEMS-RF) pose de nouveaux chalenges en termes de maîtrise du matériau et de compatibilité avec les technologies MEMS existantes. Cette thèse s’est portée sur le composé PMN-PT avec la composition 65/35 qui possède une permittivité relative supérieure à 10000 sous forme de matériau massif.Ce travail de thèse a été consacré à l’étude de l’intégration du composé PMN-PT dans des composants passifs que sont les commutateurs MEMS. Dans la gamme de fréquence d’intérêt, de 500 MHz jusqu’à 20 GHz, les propriétés de ces matériaux ont été peu étudiées sur les matériaux massifs et encore moins sous forme de films minces. L’objectif de cette thèse était de réaliser les couches minces ferroélectriques et de tester leur compatibilité dans l’ensemble du fonctionnement d’un composant MEMS mais aussi de mener une étude réciproque : l’analyse des FeMEMS (MEMS basé sur les ferroélectriques) permettant de compléter les connaissances de ces matériaux dans cette gamme de fréquence. Ce travail est d’intérêt pour l’industrie de la technologie MEMS mais aussi pour la science des matériaux ferroélectriques mais aussi par la compréhension des mécanismes physiques gouvernant aux propriétés diélectriques en termes de pertes notamment dans ce domaine de fréquences.Les caractérisations des MEMS-RF présentées dans cette thèse ont démontré la compatibilité du MEMS PMN-PT dans la gamme de fréquence entre 500MHz et 10 GHz avec de très bonnes performances. En utilisant cette adaptation, la technologie actuelle est ainsi capable de couvrir tous les bandes de fréquence les plus importantes : la bande de télécommunication civile de 1 GHz à 5 GHz en utilisant le PMN-PT, la bande X pour les satellites entre 5 GHz et 15 GHz avec PZT et la bande de haute fréquence de 15 GHz à 40 GHz pour la défense avec les diélectriques traditionnels (Si3N4). / The current information systems depend strongly on the microwave technology used for wireless communications. The enhanced performance of MEMS radio frequency capacity in X-band (8 GHz and 12 GHz) is an important issue not only for Telecom applications but also for Radar applications. The integration of ferroelectric materials with high-k t is highly demanded to replace the traditional dielectrics. This high-k property is accessible for compounds derived from the perovskite structure. Incorporating such materials in switches radio-frequency (RF-MEMS) impose however new chalenges in terms of the compatibility with the existing MEMS technologies. This thesis is focused on the compound PMN-PT with composition 65/35, which has a relative permittivity greater than 10,000 in the form of bulk material.This thesis has been devoted to the study of the integration of PMN-PT thin films in passive components such as MEMS switches. In the frequency range of interest, 500 MHz to 20 GHz, the properties of these materials have not been studied in bulk materials and even less in the form of thin films. The aim of this thesis was to fabricate the ferroelectric thin films and test their compatibility in the overall operation of a MEMS component. This study provides a reciprocal analysis FeMEMS (MEMS based on ferroelectrics) to complete knowledge of these materials in this frequency range. This work makes interest to both the industry and MEMS ferroelectric materials science who is trying to understand the physical mechanisms governing the dielectric properties in terms of losses in this particular range of frequencies.The characterizations of RF-MEMS presented in this thesis have demonstrated the compatibility of MEMS PMN-PT in the frequency range between 500MHz to 10 GHz with very good performance. Using this adaptation, the current technology is able to cover the most important frequency bands: the civil band telecommunication 1 GHz to 5 GHz using the PMN-PT, the X-band satellites between 5 GHz and 15 GHz with PZT and high frequency band of 15 GHz to 40 GHz for the defense with traditional dielectric (Si3N4).

Environmental noise at high levels and inappropriate construction techniques used in conventional buildings in Brazil claim for a transition to better construction systems. Recently the Brazilian standard NBR 15575:2013 established for the first time parameters and criteria for residential building performance. In standard minimum requirements for sound insulation are given, for example for external walls and roof structures. This way it is of fundamental importance to have sound transmission loss data for diferente types of such elements at hand. Taking into account that there is very little information on the sound transmission loss of external walls of the light steel frame (LSF) type measurements of sound insulation of different vertical external LSF walls typically used in Brazil were carried out. Eighteen different LSF walls were mounted in the sound transmission measurement chamber of the Federal University of Santa Maria and measurements were carried out in accordance with ISO 10140:2010. Sound insulation was characterized by means of the sound reduction index R, the weighted sound reduction index Rw and the sound transmission class, making it possible to compare the sound insulation of the LSF walls with data from the literature. The LSF walls under investigation in this study used different materials such as OSB panels, cement boards, plaster boards, Smartside panels, PVC panels, XPS panels and magnesium oxide boards for the outer face. The influence of resilient channels and sponge tape, placed between the outer face and the metalic studes, were also evaluated. The sound insulation of the diferente LSF walls were found to be 43 dB ≤ Rw ≤ 50 dB and 45 dB ≤ STC ≤ 52 dB. Within the LSF walls measured the one which used magnesium oxide boards on the outer face showed to have the highest weight sound reduction index (Rw = 50 dB). Resilient channels, fabricated especially for this study, and sponge tape were able to provide an increase of Rw and STC up to 5 dB compared to the same wall without this resilient elements, and provide better sound insulation especially for frequencies higher than 400 Hz. From the data it can be concluded that LSF walls are more efficient regarding the sound insulation than single walls of the same surface mass and in some cases even better than single walls of superior surface mass, such as walls made of massive brick or concrete blocks. / O excesso de ruído ambiental e as inadequadas técnicas construtivas dos sistemas convencionais utilizados no mercado da construção civil brasileira, fazem com que seja necessária a introdução de novas tecnologias construtivas mais racionais e produtivas. A partir da entrada em vigor da NBR 15575:2013 foram estabelecidos diversos parâmetros de desempenho para edificações habitacionais. A referida norma também estabelece exigências mínimas de isolamento acústico para os sistemas que compõem as edificações, entre eles, as vedações verticais. Desta forma, informações sobre o isolamento acústico providenciado pelos diferentes sistemas construtivos tornaram-se de fundamental importância. Tendo em vista a pouca informação existente na literatura sobre o isolamento sonoro de paredes externas em light steel frame (LSF), foram realizadas medições de perda de transmissão sonora em paredes externas executadas neste sistema construtivo, usadas tipicamente no mercado brasileiro. Dezoito composições de paredes em LSF foram montadas na câmara reverberante de transmissão sonora da UFSM para realização dos ensaios de perda de transmissão conforme procedimentos propostos pela ISO 10140:2010. O isolamento sonoro foi quantificado a partir dos espectros do índice de redução sonora R, pelo índice de redução sonora ponderado Rw e pela classe de transmissão sonora STC, facilitando a comparação entre diferentes composições de parede e dados de isolamento sonoro encontrados na bibliografia. Os principais materiais utilizados no revestimento das paredes LSF foram paineis OSB, placas cimentícias, placas de gesso acartonado, réguas Smartside, réguas de siding vinílico, painéis XPS e placas de óxido de magnésio. A influência da utilização de barras resilientes e fitas de espuma de PVC, entre as placas de revestimento e a estrutura metálica, também foi avaliada. Determinou-se que o isolamento sonoro das diferentes paredes LSF avaliadas é de 43 dB ≤ Rw ≤ 50 dB e 45 dB ≤ STC ≤ 52 dB. Dentre as paredes externas em LSF, aquela que utilizou placas de óxido de magnésio na face exterior apresentou o maior Rw = 50 dB. As barras resilientes e fitas de espuma de PVC foram capazes de aumentar o Rw e STC em até 5 dB, se comparado à parede semelhante sem estes dispositivos, especialmente nas frequências a partir de 400 Hz. A partir da análise dos dados, concluiu-se que as paredes LSF consideradas paredes duplas são mais eficientes no isolamento sonoro quando comparadas às paredes simples ou homogêneas de mesma massa e até do que algumas paredes com massa muito superior, como paredes de tijolos maciços, de blocos de concreto ou de blocos cerâmicos.

This thesis describes methods of high frequency noise and vibrations computation of cabin part of EV–55M (aircraft developed by Evektor Kunovice). There is a brief summary of methods used for determining high frequency noise and vibrations in the first part of the thesis. Detailed explanation is given for Statistical Energy Analysis (SEA) which is nowadays the most dominant method in this area. The energy balance equation is derived in this chapter and SEA parameters such as modal density, damping loss factor, coupling loss factor and power input are introduced here. Next part deals with main noise sources of propeller driven and jet aircraft and passive and active noise controls are discussed. Practical part of this thesis deals with modeling aircraft EV–55M fuselage using VA One SEA module. Two models were created. First of them is only an outside fuselage with aircraft flooring and the second one is extended by interior trim panels and is applicable for simulation of noise control treatments. Computational modeling is accompanied by experimental measurement of passive noise control material characteristics. Postprocessing of information obtained from impedance tube measurement was performed in FOAM – X. Determined characteristics of porous material were used as inputs to VA One and reduction of sound pressure level in fuselage cavities by using noise control treatment was found. In conclusion there is a summary of noise transmission paths from sources to interior cavity and some treatments of them are simulated