In this thesis, the tonal noise produced by flow over perforated plates at oblique angles of incidence is studied experimentally. A two-dimensional model of a perforated plate is used, where the circular holes of a typical perforated plate are replaced by a series of long rectangular Aluminum slats with an adjustable gap width between them. The slats are 3.175 mm thick and the gap width between them is set to 3.175 mm, 6.35 mm, and 12.7 mm. This simplified model is mounted at the exit of an open-loop wind tunnel and tested at angles of incidence of 0° to 40° and flow velocities of 0 to 30 m/s. An angle of 0° is defined as flow parallel to the plate. The acoustic response is studied using microphone measurements, and flow visualization is done using particle image velocimetry. The effect of the angle of incidence, flow velocity, gap width, and streamwise position are investigated. The flow visualization reveals that tonal noise is produced by the periodic shedding and impingement of vortices at the trailing edge of the gaps. Vortices form in the unstable free shear layer originating at the leading edge of the gap and impinge on the downstream side of the gap. At the downstream corner, these vortices separate into vortex pairs, consisting of one positively rotating and one negatively rotating vortex. These vortices are shed periodically, leading to the production of tonal noise at the shedding frequency. The effect of the angle of incidence is investigated by changing the angle of the plate with respect to the flow. For a given gap width, tones are produced only for a specific range of angles. Depending on the plate geometry, this range of angles is typically around 5° to 30°. Within this range of angles, the free shear layer impinges on the downstream side of the gap. For angles which are too small or too large, the free shear layer misses this downstream side and tones are not produced. For a larger gap width, tones are produced at smaller angles of incidence. Similarly, for a given plate geometry, there is a preferred range of flow velocities at which tonal noise is produced. The velocity at which the free shear layer is the most unstable at the tone frequency produces the strongest vortices and the loudest tones. The optimal velocity is lower for larger gap widths. Finally, it is found that the magnitude of the produced tones increases in the streamwise direction over repeated gaps along the length of the plate. This is due to the local flow conditions changing in the streamwise direction, only reaching the optimal conditions after a certain length of the plate. / Thesis / Master of Applied Science (MASc)

<p dir="ltr">Acoustic holography is a powerful tool in the visualization of sound fields and sound sources. It provides engineers and researchers clear insights into sound fields as well as their sound sources. Some widely-used methods include Nearfield Acoustical Holography (NAH), Statistically Optimized Nearfield Acoustic Holography (SONAH) and the Equivalent Source Method (ESM). SONAH and ESM were developed specifically to tackle the intrinsic deficiency of the Fourier-based NAH which requires that the sound field fall to negligible levels at the edges of the measurement aperture, a requirement rarely met in practice. Besides the aforementioned methods, the Inverse Boundary Element Method (IBEM) can be used, given sufficient measurements and computational resources. As useful as they are in visualizing the sound field, none of these methods can provide direct guidance on potential design modifications of the observed structure in order to unequivocally reduce sound power radiation. Acoustic radiation mode analysis has previously been primarily associated with active noise control applications. Since the radiation modes radiate sound power independently, it is only necessary to modify the surface vibration patterns so that they do not couple well with the radiation modes in order to guarantee a reduction of the radiated sound power. Since the radiation modes are orthogonal and complete, they can be used as the basis functions through which the source surface vibration can be described. Therefore, an acoustic holography method based on the acoustic radiation modes will enable the sound power ranking of the modal components of the surface vibration pattern, and in turn, point out the component(s) which should be targeted in order to reduce the overall sound power. However, use of the acoustic radiation modes in the inverse procedure comes with a price: the detailed geometry of the object to be measured must be obtained, thus enabling the calculation of acoustic radiation modes and the modal pressures. But this is not an issue for original equipment manufacturers given that almost all prototypes are now designed with CAD, as is the case with the engine example to be described next.</p><p dir="ltr">In modern engine design, downsizing and reducing weight while still providing an increased amount of power has been a general trend in recent decades. Traditionally, an engine design with superior NVH performance usually comes with a heavier, thus sturdier structure. Therefore, modern engine design requires that NVH be considered in the very early design stage to avoid modifications of engine structures at the last minute, when very few changes can be made. NVH design optimization of engine components has become more practical due to the development of computer software and hardware. However, there is still a need for smarter algorithms to draw a direct relationship between the design and the radiated sound power. At the moment, techniques based on modal acoustic transfer vectors (MATVs) have gained popularity in design optimization for their good performance in sound pressure prediction. Since MATVs are derived based on structural modes, they are not independent with respect to radiated sound power. In contrast, as noted, acoustic radiation modes are an orthogonal set of velocity distributions on the structure’s surface that contribute to the radiated sound power independently. As a result, it is beneficial to describe structural vibration in terms of acoustic radiation modes in order to identify the velocity distributions that contribute the majority of the radiated sound power. Measures can then be taken to modify the identified vibration patterns to reduce their magnitudes, which will in turn result in an unequivocal reduction of the radiated sound power. A workflow of the structural optimization procedure is proposed in this dissertation.</p><p dir="ltr">While acoustic radiation modes have great efficiencies in describing radiated acoustic power, the computation of acoustic radiation modes can be time consuming. In the last chapter of this thesis, a novel way of calculating acoustic radiation modes is proposed, which differs from the traditional singular value decomposition of the power radiation resistance matrix, and which is more efficient than previously proposed procedures. </p><p><br></p>

In the world today, Concert Halls for Symphony Orchestra and Choir are generally â enclosed performance spacesâ that are completely cut-off from the outside: Whether itâ s a time of daylight or moonlight, rain or shine, summer or winter, spring or autumn, the environment within remains the same all the time. I asked the question: â What if a concert hall offers views outside?â To be more specific, the question is: â What if a concert hall offers views outside through the use of glass, along with other building materials, despite the fact that glass offers lower reflectivity and lower transmission loss for lower frequencies of sound, compared to certain other materials?â Hence the title: Interaction of Low Frequency Sound with Glass and other Building Materials in the Design of a Concert Hall for Symphony Orchestra and Choir. / Master of Architecture

<p>Generally, heavier noise control treatments are favored over lighter ones since heavier acoustical materials tend to insulate (block) noise sources more effectively than do lighter materials. In automotive applications, however, heavier materials cannot always be adopted because of concerns over the total weight of the vehicle. Thus, it would be useful to identify lightweight acoustical treatments that can mitigate vehicle interior noise. Automotive sound packages have both absorption and barrier characteristics, and there is inevitably a trade-off between these two. Therefore, it is important to study the exchange between the absorption and transmission of acoustical materials particularly as it pertains to weight. Here, a procedure based on plane wave analysis is described that can be used to identify weight reduction opportunities by adjusting the acoustical properties of a generic sound package, consisting of a fibrous layer and a flexible microperforated panel surface treatment, so that it meets a target sound pressure level in a downstream interior space. It has been found, for the configuration studied here, that there are lightweight sound package configurations that can maintain acoustical performance equivalent to that of heavier noise treatments, and further, it has been found that the lightest treatments tend to favor barrier performance rather than absorption. Further, the impact of acoustical leaks has been considered, and it has been found that even very small leaks can result in a very substantial weight penalty if a specified level of acoustical performance is to be ensured. Further, the impact of changing the underlying panel mass and altering the frequency weighting used in the optimization process has also been considered.</p> <p>The optimizer used in the proposed procedure requires considerable calculation time; hence, the acoustic pressure calculation time needs to be minimized to enhance the efficiency of the solution process. Thus, the transfer matrix method (TMM) for a two-dimensional case was used to calculate the interior acoustic pressure for a simple geometry as a starting point in the process of identifying the minimum-weight sound packages. The TMM is a widely used analytical approach to predicting the sound pressure (and particle velocity) for a system that can be represented as a series of subsystems. Although the TMM can offer fast and simple calculations for the acoustic system, its application is limited to a plane-wave-based model. Thus, the TMM is not the best option for the acoustic pressure prediction in a complex geometry such as a vehicle interior, that involves non-planar wave propagation. Therefore, a hybrid TMM-FEA method is proposed in this research to evaluate the acoustical performance of the sound package in more complex geometries (here, a vehicle-like cavity). So, in this research, the TMM was introduced to obtain the initial solutions that can be used in conjunction with the FEA tool to calculate the sound pressure field in the complex geometry case. The correlation between the results of these two approaches was then analyzed to develop a space-averaged pressure prediction model for various absorptive cases in the interior space. Finally, this SAP prediction model was used to generate an acoustic map that can be used to graphically estimate the SAPs in the complex geometry case.</p> <p>In order to validate the usage of the developed equation for different sets of boundary conditions, several case studies were performed to study the effects of the surface impedance arrangements, geometrical shapes, and, lastly, the presence of extra features in the interior space. Finally, the SAP difference between the area near the driver’s right ear and the total interior cavity was studied to show that the SAP of the total cavity can be adjusted to evaluate the acoustic performance of the sound packages along the lines of conventional industry practice. </p>

Submitted by JOSIANE SANTOS DE OLIVEIRA (josianeso) on 2017-11-30T11:22:21Z No. of bitstreams: 1 Cláudio Trindade Scherer_.pdf: 4509704 bytes, checksum: 6adc0f4eb6a2c5abca0aa3ac53dbcea7 (MD5) / Made available in DSpace on 2017-11-30T11:22:22Z (GMT). No. of bitstreams: 1 Cláudio Trindade Scherer_.pdf: 4509704 bytes, checksum: 6adc0f4eb6a2c5abca0aa3ac53dbcea7 (MD5) Previous issue date: 2017-08-14 / Nenhuma / O conjunto de paredes e portas separadas pela circulação condominial em edifícios residenciais passou a ter seu desempenho acústico avaliado, a partir da entrada em vigor da norma brasileira NBR 15575, que trata do desempenho das edificações. Nesse contexto, esse trabalho propõe determinar a influência das características dos elementos construtivos – portas e circulações entre unidades habitacionais – no isolamento ao ruído aéreo do conjunto de paredes e portas separadas pelo hall de entrada. Primeiramente foi realizado um estudo piloto que envolveu ensaios em campo feitos em diversas obras. Com isso, foram escolhidos três prédios e executados uma série de ensaios de desempenho acústico em campo, abrangendo diversas situações. Também foram usados artifícios para a vedação das frestas das portas, a fim de verificar a melhora do desempenho do sistema. Os resultados obtidos apontam para a perda de desempenho acústico com o aumento das frestas entre a folha da porta e o piso. Foram encontradas também relações com tempo de reverberação dos ambientes de circulação e a distância entre as portas de entrada das unidades habitacionais. / Sets of walls and doors separated by condominium corridors in residential buildings started having their acoustic performance evaluated when the Brazilian standard NBR 15575 came into effect, which concerns the performance of buildings. In this context, this study proposed to determine the influence of the characteristics of constructive elements – doors and corridors between residential units – on the airborne sound insulation of the set of walls and doors separated by the entrance hall. First, a pilot study was conducted based on tests performed on many buildings, but it was noted that a deeper study on the subject would be required. Thereby, three buildings were chosen and a series of acoustic performance tests was executed, covering several situations. Maneuvers for sealing door gaps were used as well, in order to assess the performance gains of the system. The results indicated loss of acoustic performance when there were more gaps between the door leaf and the floor. Moreover, relations were found regarding the reverberation time of the corridors and the distance between the entrance doors of residential units.

Wong Chun Yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 137-143). / Abstracts in English and Chinese. / LIST OF FIGURES --- p.xi / LIST OF TABLES --- p.xv / LIST OF ACRONYMS --- p.xvi / Chapter CHAPTER ONE - --- INTRODUCTION / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Research background --- p.1 / Chapter 1.2.1 --- Urban park functions and challenges --- p.1 / Chapter 1.2.2 --- Urban park acoustic environment --- p.2 / Chapter 1.3 --- Urban Parks in Hong Kong --- p.5 / Chapter 1.4 --- Conceptual framework and research objectives --- p.7 / Chapter 1.5 --- Research significance --- p.9 / Chapter CHAPTER TWO - --- LITERATURE REVIEW / Chapter 2.1 --- Introduction --- p.11 / Chapter 2.2 --- Changing approach in managing noise problem in living environment: from noise control to soundscape planning --- p.12 / Chapter 2.2.1 --- Noise control: sound (noise) as a waste to avoid --- p.12 / Chapter 2.2.2 --- Soundscape planning: sound as a resource to utilize --- p.12 / Chapter 2.2.3 --- Soundscape as a guiding principle --- p.13 / Chapter 2.2.4 --- The importance of soundscape --- p.14 / Chapter 2.2.5 --- Criteria for soundscape planning --- p.15 / Chapter 2.2.5.1 --- Sound intensity and quietness --- p.15 / Chapter 2.2.5.2 --- "Sound source, soundscape clarity and sound preference" --- p.16 / Chapter 2.2.5.3 --- "Sound information content, sound-image congruence and acoustic masking" --- p.18 / Chapter 2.2.5.4 --- Acoustic comfort --- p.20 / Chapter 2.2.5.5 --- Acoustic objectives --- p.20 / Chapter 2.2.6 --- From soundscape planning to environmental design --- p.21 / Chapter 2.3 --- Impact of road traffic noise on human --- p.21 / Chapter 2.3.1 --- Detection of road traffic noise --- p.22 / Chapter 2.3.2 --- Response to road traffic noise --- p.22 / Chapter 2.3.2.1 --- Reaction to noise --- p.23 / Chapter 2.3.2.2 --- Physiological response --- p.24 / Chapter 2.3.2.3 --- Behavioural response --- p.24 / Chapter 2.3.2.4 --- Cognitive response --- p.25 / Chapter 2.3.3 --- Moderating factors for road traffic noise impact --- p.25 / Chapter 2.3.3.1 --- Auditory masking --- p.25 / Chapter 2.3.3.2 --- Visual screening --- p.26 / Chapter 2.4 --- Previous studies on urban park soundscape --- p.27 / Chapter 2.4.1 --- Focus on sound intensity --- p.27 / Chapter 2.4.2 --- Sound as a resource to utilize --- p.28 / Chapter 2.4.3 --- Recommendations on park design --- p.29 / Chapter 2.4.4 --- Research gaps --- p.31 / Chapter CHAPTER THREE - --- METHODOLOGY / Chapter 3.1 --- Introduction --- p.33 / Chapter 3.2 --- Site selection --- p.33 / Chapter 3.3 --- Characterizing urban park soundscape --- p.38 / Chapter 3.3.1 --- Identification of sound source --- p.38 / Chapter 3.3.2 --- Field Measurement of Sound intensity and frequency spectrum --- p.40 / Chapter 3.3.3 --- Contribution from road traffic noise --- p.41 / Chapter 3.3.4 --- Questionnaire design to study human perception --- p.43 / Chapter 3.3.5 --- Sampling strategy --- p.47 / Chapter 3.4 --- Summary --- p.48 / Chapter CHAPTER FOUR - --- SOUNDSCAPE OF URBAN PARKS IN HONG KONG / Chapter 4.1 --- Introduction --- p.50 / Chapter 4.2 --- Sound source --- p.50 / Chapter 4.2.1 --- Mechanical sounds --- p.57 / Chapter 4.2.2 --- Natural sounds --- p.57 / Chapter 4.2.3 --- Man-made sounds --- p.59 / Chapter 4.2.4 --- Soundscape clarity --- p.59 / Chapter 4.3 --- Sound Intensity --- p.63 / Chapter 4.4 --- Contribution from road traffic noise to urban park sound intensity --- p.66 / Chapter 4.5 --- Frequency spectrum --- p.73 / Chapter 4.6 --- Effect of topographic variations --- p.76 / Chapter 4.7 --- Conclusion --- p.82 / Chapter CHAPTER FIVE - --- PARK VISITOR'S PERCEPTION ON URBAN PARK SOUNDSCAPE / Chapter 5.1 --- Introduction --- p.84 / Chapter 5.2 --- Urban park noisiness --- p.84 / Chapter 5.3 --- Sound source --- p.85 / Chapter 5.4 --- Sound preference --- p.87 / Chapter 5.5 --- Effect of park size --- p.93 / Chapter 5.6 --- Effect of park function --- p.94 / Chapter 5.7 --- Effect of fountain --- p.95 / Chapter 5.8 --- Perceived importance of tranquility --- p.96 / Chapter 5.9 --- Conclusion --- p.101 / Chapter CHAPTER SIX - --- IMPLICATIONS OF RESEARCH FINDINGS ON URBAN PARK SOUNDSCAPE DESIGN / Chapter 6.1 --- Introduction --- p.102 / Chapter 6.2 --- Soundscape of urban parks in Hong Kong: undesirable yet being adapted… --- p.102 / Chapter 6.3 --- Enhancing soundscape identity of urban parks --- p.103 / Chapter 6.4 --- Small parks --- p.104 / Chapter 6.5 --- Large parks --- p.107 / Chapter 6.6 --- Conclusion --- p.109 / Chapter CHAPTER SEVEN - --- CONCLUSION / Chapter 7.1 --- Introduction --- p.110 / Chapter 7.2 --- Summary of findings --- p.110 / Chapter 7.3 --- Limitations of the research --- p.115 / Chapter 7.3.1 --- Park visitor's aspiration for desirable soundscape --- p.115 / Chapter 7.4 --- Further studies for designing a desirable urban park soundscape --- p.116 / APPENDIX ONE --- p.118 / APPENDIX TWO --- p.122 / REFERENCES --- p.137

Healing and clinical work requires a complex choreography of architectural acoustic design in healthcare settings. In most healthcare settings, medical staff members conduct vital tasks that may have life-and-death implications. Patients visit the hospitals to heal. Their expectations include fast recovery, restful sleep, and privacy (i.e., speech privacy). However, sound environment qualities of the care settings often fall far from supporting the mission of hospitals. There is strong and growing evidence showing that effective soundscapes in healthcare settings potentially impact errors, healing and stress for patients, families and staff but it is still not clear what measures of the sound environment best predict key healthcare outcomes and what design strategies best impact those measures. By using a multi-method approach (i.e., objective and subjective noise level measurements, in-situ impulse response measurements, heuristic design analysis, theoretical studies, acoustic simulations and statistical analysis), this study aims to develop evidence based design strategies by statistically defining the relationships between three types of variables: (1) architectural floor-plate design metrics, (2) acoustic metrics, and (3) occupant response. The research is conducted in three phases. The first phase of the study compared the objective and subjective qualities of the hospital sound environments with different architectural designs, assessed the effectiveness of a newer acoustic metrics in capturing caregiver perceptions, and evaluated the impact of particular noise sources on caregiver outcomes. The second phase of the study tested the validity of an acoustic simulation tool in estimating the acoustic qualities of the healthcare soundscapes. The third phase of the study systematically explored the relationship between floor-plate design and acoustics of complex inter-connected nursing unit corridors. Even though the relationship between design and acoustics of proportional spaces (a.k.a. rooms with more traditional dimensions) has been well documented, the number of studies linking design and acoustics of complex non-proportional spaces such as inter-connected corridors still remains limited. The findings of the first phase show that critical care sound environments with different designs can vary drastically and impact caregivers` perceived wellbeing and task performance (e.g., patient auditory monitoring). Despite their extensive use, traditional noise metrics sometimes may not be effective in capturing unique characteristics of healthcare sound environments. This study validated the effectiveness of a new more detailed noise metric, "occurrence rate", in capturing the differences between acoustic characteristics of healthcare sound environments. Moreover, particular noise sources such as impulsive noises are likely to dominate the ICU sound environments and interfere with perceived caregiver health and performance. The findings of the second phase suggest the potential effectiveness of acoustic simulation tools (with hybrid prediction programs) in estimating the acoustic qualities of complex inter-connected hospital corridors. The findings of the third phase suggest the potential significant impact of design features of particular hallways (e.g., number of turns, corridor length, and number of branches) and overall floor-shape characteristics of inter-connected corridors (i.e., relative grid distance, and visual fragmentation) on reverberation time. Overall, in the units with shorter, more compact, fragmented corridors with multiple number of branching hallways, reverberation times are likely to be less. Moreover receivers located at the corridors with less number of turns from the sound source also potentially experience lower reverberation times. According to previous research, the human auditory system`s ability to monitor auditory cues is likely to be higher in the less reverberant sound environments.

Orientador: Stelamaris Rolla Bertoli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-23T06:13:27Z (GMT). No. of bitstreams: 1 Maiorino_AlexandreVirginelli_M.pdf: 20810001 bytes, checksum: 874af06d3cad4ebebbbda0ac07b75cd5 (MD5) Previous issue date: 2013 / Resumo: A construção de Teatros para Múltiplo uso tem se tornado cada vez mais comum devido à necessidade de abrigar diversos tipos de espetáculos em um único espaço. Para adequar à acústica destes espaços para a música orquestral é necessário o uso de elementos que possibilitem a variação acústica do espaço como é o caso de conchas de orquestra. O principal objetivo das conchas de orquestra é melhorar a acústica no palco para os músicos e para o maestro, melhorando a sensação de conjunto e fazendo com que os músicos ouçam melhor seus instrumentos e o grupo em geral. Entretanto, a concha de orquestra pode também melhorar o desempenho acústico da área da platéia. A hipótese deste trabalho foi o de analisar a diferença do desempenho acústico percebido na área da platéia devido à inclusão de uma concha de orquestra no palco de um teatro de múltiplo uso. Medições acústicas foram realizadas em cinco diferentes tipos de montagem da concha de orquestra no palco. As medições foram feitas de acordo com a norma ISO 3382-1 (2009). Os parâmetros acústicos medidos foram o Tempo de Reverberação, Tempo Inicial de Decaimento e Índice de Clareza. Os resultados mostraram que a concha de orquestra pode de fato mudar o desempenho acústico na área da platéia, modificando a percepção acústica subjetiva do ambiente / Abstract: The construction of multiple use theatres is becoming more common due to the need to accommodate different kinds of performances at the same space. In order to acoustically adequate this space to concert music, the inclusion of an orchestra shell becomes necessary. The main objective of an orchestra shell is to improve the acoustic quality on stage, both for musicians and for the conductor. The goal is to improve balance of the group allowing musicians to hear themselves and the orchestra better. However, the orchestra shell can also improve the acoustic quality for the audience. The objective of this study was to analyze the difference of the acoustic performance perceived at the audience area with the inclusion of a lightweight orchestra shell with diffuse surface in a proscenium theatre. Acoustic measurements were done in five different assembles of the orchestra shell. Measurements were done using the impulse response technique according to ISO3382-1 (2009). Measured parameters were Reverberation Time, Early Decay Time and Clarity index. Results showed that the orchestra shell can in fact modify the acoustic performance at audience area, changing the subjective acoustic perception of the space / Mestrado / Arquitetura e Construção / Mestre em Engenharia Civil

Il y a plus d'un siècle, les conditions de travail ont fortement évolué sous l'influence de l'industrialisation et notamment à partir de nouvelles méthodes de travail du type Tayloriennes. Des bureaux ouverts à l'Action Office des années 50, c'est plus de 60% de la population active qui est concernée aujourd'hui en Europe. L'évolution des réglementations, liée à la prise de conscience collective des effets psychosomatiques des nuisances sonores, entraîne l'implication par les maîtrises d'ouvrages de bureaux d'études acoustiques pour la préconisation et la mise en œuvre dans la construction et la réhabilitation des espaces tertiaires. La rencontre d'acteurs scientifiques et industriels a donné lieu à ce travail de thèse, étudiant la propagation de l'énergie acoustique pour des espaces dont une des dimensions est différente des autres.La méthode se réduit à la conservation du tenseur énergie-impulsion puis à un système d'équations couplées sur l'intensité acoustique et sur la densité d'énergie. C'est un système hyperbolique d'équations linéaires aux dérivés partielles du premier ordre. Une méthode d'intégration sur une à deux dimensions de l'espace permet d'introduire les coefficients d'absorption et de diffusion moyens. Nous introduisons le potentiel d'intensité et nous écrivons le système sous la forme d'une équation hyperbolique linéaire aux dérivées partielles du second ordre impliquant la densité d'énergie, l'intensité acoustique ou le potentiel d'intensité sur une ou deux dimensions. Nous proposons une méthode analytique approchée permettant de vérifier les résultats à une dimension.Pour la conception acoustique des plateaux de bureaux, la modélisation informatique est un outil remarquable souffrant pourtant de limitations restreignant ses applications. Nous résolvons le formalisme introduit dans ce travail par la méthode des différences finies dans le domaine temporel sur une et deux dimensions. Les schémas utilisés sont stables et explicites et peu couteux en mémoires informatiques. Le fait que nous nous intéressions à une variable énergétique permet de considérer un pas de modélisation spatial important - de l'ordre du mètre - et d'accélérer d'autant les calculs.Le partenariat industriel nous a notamment permis d'accéder à des espaces de type plateaux de bureaux. Nous comparons les résultats des modélisations avec des mesures in situ conduites avec un microphone SoundField ST250 permettant l'estimation de la densité d'énergie et de l'intensité acoustique. / More than a century ago, working conditions have evolved under the influence of industrialization and especially of new management methods such as the Taylorism. From Open-Spaces to Action Offices in the 1950s, more than 60 % of the European working population is concerned today. The evolution of regulations, linked to the collective awareness of the psychosomatic effects of noise, has led clients to request the involvement of acoustical consultants for giving recommendations and supervising their implementation in constructions and rehabilitations of office spaces. This is why scientific and industrial stakeholders joined forces for this thesis dedicated to the propagation of sound energy within rooms characterized by one dimension different from the others.The method developed in this thesis reduces the conservation of the energy-stress tensor to a system of coupled equations for the sound intensity and the sound energy density. It is a hyperbolic system of linear, partial differential equations of first order. Integrating this system on one or two space dimensions leads to the introduction of the mean absorption and diffusion coefficients. We then introduce an intensity potential and write the system in the form of a linear hyperbolic equation involving partial derivatives of second order for the energy density, the sound intensity, or the intensity potential in one or two dimensions. We also propose an analytical approximated method to verify the results in one dimension.For the acoustic design of open-space offices, computer modelling is an outstanding tool. Yet limitations restrict its applications. We solve the equations introduced in this work by the finite-difference time-domain method in the one- and two-dimensional cases. We use stable and explicit schemes that require little computer memory. Considering energy variables allows the use of large spatial steps - of the order of the metre - and accelerates the calculations.The industrial partnership notably gave us access to open-space offices. We compare the results of the modelling with in situ measurements carried out with a SoundField ST250 microphone that makes it possible to estimate the sound energy density and the sound intensity.

The scope of this research concerns the passive damping of structural vibrations by the use of viscoelastic layers. It is motivated by the need for efficient numerical tools to deal with the medium frequency behaviour of industrial viscoelastic sandwich products. The sandwich modelling technique is based on the use of an interface element: the two deformable plates are modelled by special plate elements while the intermediate dissipative layer is modelled with interface elements. This interface element is based on the first-order shear deformation theory and assume constant peel and shear stresses in the polymer thickness. This element couples the lower and upper layers without additional degrees of freedom. The partition of unity finite element method (PUFEM) is applied to the development of enriched Mindlin plate elements. The element shape functions are obtained as the product of<p>partition of unity functions with arbitrary chosen enrichment functions. Polynomial enrichment leads to the generation of high-order polynomial shape functions and is therefore similar to a p-FEM technique. Numerical examples illustrate the use of both PUFEM Mindlin plate elements and interface elements for the simulation of viscoelastic sandwich structures. / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished