Dissertations / Theses on the topic 'Room Acoustic Simulation'

L’acústica de sales és la ciència encarregada d’estudiar la propagació del so en entorns tancats. La informació acústica de qualsevol entorn, coneguda com la resposta impulsional, s’expressa en termes del camp acústic com una funció de l’espai i el temps. La formulació analítica de la distribució de les variables del so és, en general, extremadament complexa d’obtenir i només existeixen solucions d’escenaris molt simples i irreals. Per tant, l’ús d’ordinadors per solucionar aquest tipus de problemes ha emergit com una alternativa adequada per calular funcions de resposta. En aquesta Tesi ens hem centrat en l’ús de mètodes basats en rajos per calcular funcions de resposta. Més concretament, presentem el disseny i la implementació d’un motor de traçat de rajos que calcula funcions de resposta en cualsevol entorn virtual, obtenint no només la funció de resposta per la presió sinó també pel vector de velocitats del camp acústic. Amb aquesta informació extra tenim totes les dades necessàries per modelar la propagació del so i podem de forma natural espacialitzar un so per qualsevol configuració d’altaveus. Aquesta recerca contribueix als aspectes principals del càlcul de funcions de resposta utilitzant mètodes basats en rajos. El motor de traçat de rajos que presentem inclou un mètode desenvolupat per aplicar la solució analítica de la Funció de Distribució Acústica de Reflectància Bidireccional (A-BRDF) al Model de Dispersió Basat en Vectors (VBS), fet que redueix molt notablement el cost computacional.
Room acoustics is the science devoted to study sound propagation in enclosures where the sound conduction medium is bounded on all sides by walls, ceiling and floor. The acoustic information of any room, the so-called impulse response, is expressed in terms of the acoustic field as a function of space and time. The analytical formulation of the sound variables distribution is, in general, extremely hard to obtain and there only exist solutions of very simple and unrealistic scenarios. Therefore the use of computers for solving this type of problems has emerged as a proper alternative to calculate impulse responses. In this Thesis we focus on the use of the ray-based methods to compute impulse responses. More precisely, we present the design and implementation of a sound ray tracing engine that computes the impulse response in any given environment not only for the pressure but also for the velocity vector of the acoustic field. With this extra information we have all the necessary data to model the propagation of sound and we can then naturally spatialize the sound to any speakers layout. This research contributes to the main aspects in the computation of impulse responses using a ray-based approach. The presented ray tracing engine includes a method developed to apply the analytical solution for the Acoustic Bidirectional Reflectance Distribution Function (A-BRDF) in the Vector Based Scattering Model (VBS), which reduces dramatically the computational cost.

The sound field distribution in a room is the consequence of the acoustic properties of radiating sources and the position, geometry and absorbing characteristics of the surrounding boundaries in an enclosure (boundary conditions). Despite there existing a consolidated acoustic wave theory, it is very difficult, nearly impossible, to find an analytical expression of the sound variables distribution in a real room, as a function of time and position. This scenario represents as an inhomogeneous boundary value problem, where the complexity of source properties and boundary conditions make that problem extremely hard to solve. Room acoustic simulation, as treated in this thesis, comprises the algebraical approach to solve the wave equation, and the way to define the boundary conditions and source modeling of the scenario under analysis. Numerical methods provide accurate algorithms for this purpose and among the different possibilities, the use of discrete-time methods arises as a suitable solution for solving those partial differential equations, particularized by some specific constrains. Together with the constant growth of computer power, those methods are increasing their suitability for room acoustic simulation. However, there exists an important lack of accuracy in the definition of some of these conditions so far: current frequency-dependent boundary conditions do not comply with any physical model, and directive sources in discrete-time methods have been hardly treated. This thesis discusses about the current state-of-the-art of the boundary conditions and source modeling in discrete-time methods for room acoustic simulation, and it contributes some algorithms to enhance boundary condition formulation, in a locally reacting impedance sense, and source modelling in terms of directive sources under a defined radiation pattern. These algorithms have been particularized to some discrete-time methods such as the Finite Difference Time Domain and the Digital Waveguide Mesh.
Escolano Carrasco, J. (2008). Contributions to discrete-time methods for room acoustic simulation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8309
Palancia

The best concert halls take benefit not only from the basic room shape but also from the corrugations of the walls. These diffusive surfaces are responsible for energy mixing, energy extraction from geometrical paths, for filling gaps and increasing reflections density in the impulse response. Hence, performance spaces are characterized by a complex sound field, due to the presence of absorptive and diffusive surfaces. The acoustic properties of these surfaces are characterized based on laboratory standardized measurements. Despite this, no sufficiently satisfactory databases exist. Thus, acousticians and practitioners alike rely on guidelines and experience to make their design choices. Based on this state of the art of diffusive surface design, the present work aims at giving more insight on their deployment by looking at the argument from a multidimensional point of view. First, it considers the estimation of the accuracy of the physical phenomenon measurements (only the random-incidence scattering coefficient has been considered), and further studies the effects of this accuracy on the objective room acoustic parameters, on the accuracy of simulation results and on perception. Knowing this interactions would give a measure of how much effort should be put into the acoustic characterization of diffusive surfaces and more freedom/ restrictions regarding the design of such surfaces could be determined. In Chapter 2, the experimental results aimed at providing a useful insight into the accuracy of the measurement procedure prescribed in the ISO 17497-1:2004 standard. The unsolved aspects of the measurements set-up have been systematically investigated and their contribution to the random-incidence scattering coefficient values has been estimated. It was found that some of these aspects contribute significantly to the measurement accuracy. In Chapter 3, in-situ evaluations of the acoustic effects that diffusive surfaces have on the objective room acoustic parameters have been investigated. To deepen such knowledge, acoustic measurements have been carried out in a variable-acoustic concert hall, the Espace de Projection, at the Institut de Recherche et Coordination Acoustique/Musique in Paris. The sensitivity of the sound field has been objectively investigated by observing the variation of the objective acoustic parameters, that is EDT, T30, C80, D50 and IACC, in either reflective and diffusive condition. It was found that some parameters are more affected by the degree of surface diffusivity, thus, its accuracy. In Chapter 4 has been investigated objectively the sensitivity of a virtual room sound field to the scattering coefficients accuracy. Two different prediction models have been used to simulate the sound field within a fan-shaped hall. It was found that some simulated parameters are affected by the random-incidence scattering coefficient accuracy, i.e. uncertainties of input data, which are higher than a limit value, lead to less reliable simulation results. In Chapter 5, an auditory experiment has been conducted to highlight some perceptual aspects regarding the use of diffusive surfaces in concert halls. These results provide more insight and help to understand whether listeners perceive the presence of diffusive surfaces, and how this perception is scattered throughout the audience area. Furthermore, the study is aimed at determining the objective measurements of a sound field which best correlate to the subject’s perception. This would give the measure of how much effort should be put into the determination of the diffusive properties of surfaces, and which could be the variables to relate in an analytic equation, which could readily express the effects of diffusion in room acoustic.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The study of room acoustics is linked to the importance of sound inside a room, so the architectural characteristics of the internal space determine the acoustic behavior. To get better acoustics of a room there are computational methods that simulate the acoustic behavior of a room before his execution, providing the prediction of the simulated environment behavior from the acoustic point of view. The acoustic parameters of the resulting acoustic simulations as Reverberation Time, Initial Decay Time, Clarity, Sharpness and Speech Transmission Index, are responsible for identifying the acoustic conditions of the geometric model of a classroom. This geometric model used as sample classrooms of different types of municipal schools in Santa Maria - RS, with the aim of developing a classroom typology for the music teaching from virtual acoustic models using computing simulation. Geometric models of classrooms for teaching music were developed using as input data, dimensions, shapes and elements usually used in these environments and developed representative virtual acoustic models these virtual classrooms, in which were measured acoustic parameters related to the reverberation time from the impulse response of the acoustic models of virtual rooms. We analyzed the experimental results and simulated with and without furniture for the acoustic parameters, and these comparisons were related to the values of JND (Just Noticeable Difference) near the standard tolerance according to ISO 3382/2009 with normalized values of 500 Hz to 1000 Hz. A geometric study was developed based on Bolt (1946) which defined the appropriate geometric measures of the room. Thus, a functional typology was originated which meets the architectural acoustic requirements and the initial proposal of presenting a music classroom typology providing an environment with acoustic quality, according to Law number 11.769/2008 that inserts education music in schools on a mandatory basis.
O estudo da acústica de salas está vinculado à importância do som dentro de um recinto, logo, as características arquitetônicas do espaço interno determinam seu comportamento acústico. Para buscar melhores condições acústicas de um recinto disponibilizam-se métodos computacionais que simulem o comportamento acústico de uma sala, antes de sua execução, proporcionando a previsão de comportamento do ambiente simulado do ponto de vista acústico. Os parâmetros acústicos resultantes das simulações acústicas, como: Tempo de Reverberação, Tempo de Decaimento Inicial, Clareza, Definição e o Índice de Transmissão da Fala são responsáveis pela identificação das condições acústicas do modelo geométrico de uma sala de aula. Este modelo geométrico utilizou como amostra as salas de aula das diferentes tipologias de escolas da rede estadual de educação de Santa Maria - RS, com o objetivo de desenvolver uma tipologia de sala de aula, para o ensino da música, a partir de modelos acústicos virtuais utilizando-se simulação computacional. Foram desenvolvidos modelos geométricos de salas de aula para o ensino da música utilizando-se como dados de entrada, dimensões, formatos e elementos, usualmente utilizados nestes ambientes, e desenvolvidos modelos acústicos virtuais representativos destas salas, aos quais foi feita uma avaliação dos parâmetros acústicos relacionados ao tempo de reverberação, partindo-se da resposta impulso dos modelos acústicos virtuais das salas. Foram analisados resultados experimentais e simulados na situação sem mobília e com mobília, para os parâmetros acústicos, e essas comparações foram relacionadas com os valores de JND (em inglês Just Noticeable Difference) padronizadas as margens de tolerância, de acordo com a ISO 3382/2009, com valores normalizados de 500 Hz a 1000 Hz. Também foi desenvolvido um estudo geométrico, a partir de Bolt (1946), que definiu as medidas geométricas adequadas da sala. Com isto, originou-se uma tipologia funcional, observando as exigências acústicas arquitetônicas, cumprindo a proposta inicial de apresentar uma tipologia de sala de aula, para a música, a fim de proporcionar um ambiente com qualidade acústica, atendendo a Lei nº 11.769/2008, que insere o ensino da música nas escolas, de forma obrigatória.

Sound propagation is a complex subject, especially in an enclosure. The study of room acoustics involves not only a research into how sound is propagated in a room, but also a search into how to measure sound under different condition and how to control sound in the case of various wall materials. For an acoustical environment, there are three separated parts: sound sources, room acoustics, and the listens. These three items form a source-medium-receiver chain, which is typical for most of communication models. In this thesis, the image method is applied to predict the acoustical quality of a real room, and the experiment for room acoustic measurement is set up. The simulation model using image method proved the design of the measurement system is efficient for room acoustics.

Bibliography: leaves 138-141.
This thesis consists of essentially two parts. The first deals with the theory and measurement of room acoustics while the second examines the room acoustic prediction methods.

L'acústica de sales s'encarrega de l'estudi del comportament de les ones sonores en espais tancats.La informació acústica de qualsevol entorn, coneguda com la resposta impulsional, pot ser expressada en termes del camp acústic com una funció de l'espai i el temps. En general, és impossible obtenir solucions analítiques de funcions resposta en habitacions reals. Per tant, en aquests últims anys, l'ús d'ordinadors per resoldre aquest tipus de problemes ha emergit com una solució adecuada per calcular respostes impulsionals.
En aquesta Tesi hem centrat el nostre anàlisis en els mètodes basats en el comportament ondulatori dins del domini temporal. Més concretament, estudiem en detall les formulacions més importants del mètode de Diferències Finites, el qual s'utilitza en moltes aplicacions d'acústica de sales, i el recentment proposat mètode PseudoEspectral de Fourier. Ambdós mètodes es basen en la formulació discreta de les equacions analítiques que descriuen els fenòmens acústics en espais tancats.
Aquesta obra contribueix en els aspectes més importants en el càlcul numèric de respostes impulsionals: la propagació del so, la generació de fonts i les condicions de contorn de reactància local.
Room acoustics is the science concerned to study the behavior of sound waves in enclosed rooms. The acoustic information of any room, the so called impulse response, is expressed in terms of the acoustic field as a function of space and time. In general terms, it is nearly impossible to find analytical impulse responses of real rooms. Therefore, in the recent years, the use of computers for solving this type of problems has emerged as a proper alternative to calculate the impulse responses.
In this Thesis we focus on the analysis of the wavebased methods in the timedomain. More concretely, we study in detail the main formulations of FiniteDifference methods, which have been used in many room acoustics applications, and the recently proposed Fourier PseudoSpectral methods. Both methods are based on the discrete formulations of the analytical equations that describe the sound phenomena in enclosed rooms.
This work contributes to the main aspects in the computation of impulse responses: the wave propagation, the source generation and the locallyreacting boundary conditions.

Performance of the buildings has always been a concern for the architects. With the enhancements in the technology, it is possible to measure, analyze and evaluate the performance of an architectural design before it is built via simulation tools developed. With the evaluation of the analysis performance of the concerned space can be upgraded if simulation tools are employed throughout the design process. However, even though the simulation tools are developed for the acoustical simulation and performance analysis, it is not always simple to integrate the simulation tools to whole design process because of both specific knowledge required for the usage of the tools and the nature of the acoustical simulation tools. Within the scope of the thesis, a simulation tool, which does not require advanced knowledge on acoustics and which provides rapid feedbacks about the performance of the design for the enhancement of the performance is developed using method of image sources.

This thesis is dealing with problem and solution of simulation in room acoustics. At the beginning is introduction with sound as waves and his behavior in closed space. Following part of text is dealing with computional methods in room acoustics, statistics methods , ray-based methods, wave-based methods. Following are focused FDTD wave method, which serves as the basis for creating simulation algorithm.Last part of this work is practical sample of MATLAB aplication enviroment for simulation of sound waves in closed room by explicit sub-methods of method FDTD. The last section contains an example and discussion of the results of simulations.

Esta tesis está centrada en el modelado de la acústica de salas en espacios cerrados mediante el uso de una ecuación de transferencia radiativa y una ecuación de difusión En este trabajo se investiga cómo a través de estos modelos teóricos se pueden simular el campo sonoro en espacios complejos. Recientemente, el modelo de la ecuación de fusión ha sido prppuesto para ser utilizado en el modelado de la acústica de salas con superficies que reflejan el sonido de forma totalmente difusa. Este enfoque del uso de la ecuación de la disusión de sido intensamente investigado en los últimos años, ya que proporciona una alta eficiencia y flexibilidad para simular las distribuciones del campo sonoro en diferentes tipos de salas; sin embargo, sólo se han realizado unas pocas investigaciones con el objetivo de indagar sobre la precisión y las limitaciones de este método alternativo. Por lo tanto, en primer lugar se presenta un modelo basado en la ecuación de transferencia por radiación siendo meta principal el unificar una amplia gama de métodos geométricos de modelado de acústica de salas. Además, esta tesis está especialmente dedicada a establecer las bases y suposiciones que permitan obtener un modelo de difusión acústica como particularización del modelo de transferencia radiativa con el objetivo de conseguir una descripción clara y adecuada de sus ventajas y limitaciones desde el punto de vista teórico. Este trabajo permite enlazar directamente al modelo de la ecuación de difusión con el grupo de métodos de la acústica geométrica reforzando sus características y permitiendo una adecuada comparación con estos métodos ampliamente reconocidos. Una vez realizado este análisis teórico, esta tesis también se dedica a cuestiones relativas a la implementación numérica del modelo acústico de la ecuación de difusión . En este trabajo, se modela el campo sonoro a través de esquemas en diferencias finitas. Los resultados de este estudio proporcionan soluciones simples y practicas que muestran unos requerimientos computacionales bajos tanto de consumo de memoria como de tiempo.
Navarro Ruiz, JM. (2012). Discrete-time modelling of diffusion processes for room acoustics simulation and analysis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14861
Palancia

The aim of this thesis was to make a practical tool for low frequency analysis in room acoustics.The need arises from Acad’s experience that their results from simulations using raytracing software deviate in the lower frequencies when compared to field measurements inrooms. The tool was programmed in Matlab and utilizes the Finite Difference Time Domain (FDTD) method, which is a form of rapid finite element analysis in the time domain.A number of tests have been made to investigate the practical limitations of the FDTD method, such as numerical errors caused by sound sources, discretization and simulation time. Boundary conditions, with and without frequency dependence, have been analysed bycomparing results from simulations of a virtual impedance tube and reverberation room to analytical solutions. These tests show that the use of the FDTD method appears well suited for the purpose of the tool.A field test was made to verify that the tool enables easy and relatively quick simulations of real rooms, with results well in line with measured acoustic parameters. Comparisons of the results from using the FDTD method, ray-tracing and finite elements (FEM) showed goodcorrelation. This indicates that the deviations Acad experience between simulated results and field measurements are most likely caused by uncertainties in the sound absorption data used for low frequencies rather than by limitations in the ray-tracing software. The FDTDtool might still come in handy for more complex models, where edge diffraction is a more important factor, or simply as a means for a “second opinion” to ray-tracing - in general FEM is too time consuming a method to be used on a daily basis.Auxiliary tools made for importing models, providing output data in the of room acoustic parameters, graphs and audio files are not covered in detail here, as these lay outside the scope of this thesis.
Målet för detta examensarbete var att undersöka möjligheten att programmera ett praktisktanvändbart verktyg för lågfrekvensanalys inom rumsakustik. Behovet uppstår från Acadserfarenhet att resultat från simuleringar med hjälp av strålgångsmjukvara avviker i lågfrekvensområdeti jämförelse med fältmätningar i färdigställda rum. Verktyget är programmerati Matlab och använder Finite Difference Time Domain (FDTD) metoden, vilket är en typav snabb finita elementanalys i tidsdomänen.En rad tester har genomförts för att se metodens praktiska begräsningar orsakade av numeriskafel vid val av ljudkälla, diskretisering och simuleringstid. Randvillkor, med och utanfrekvensberoende, har analyserats genom jämförelser av simulerade resultat i virtuella impedansröroch efterklangsrum mot analytiska beräkningar. Testerna visar att FDTD-metodentycks fungerar väl för verktygets tilltänkta användningsområde.Ett fälttest genomfördes för att verifiera att det med verktyget är möjligt att enkelt och relativtsnabbt simulera resultat som väl matcher uppmätta rumsakustiska parametrar. Jämförelsermellan FDTD-metoden och resultat beräknade med strålgångsanalys och finita elementmetoden(FEM) visade även på god korrelation. Detta indikerar att de avvikelser Acaderfar mellan simulerade resultat och fältmätningar troligen orsakas av osäkerheter i den ingåendeljudabsorptionsdata som används för låga frekvenser, snarare än av begränsningar istrålgångsmjukvaran. Verktyget kan fortfarande komma till användning för mer komplexamodeller, där kantdiffraktion är en viktigare faktor, eller helt enkelt som ett sätt att få ett”andra utlåtande” till resultaten från strålgångsmjukvaran då FEM-analys generellt är en förtidskrävande metod för att användas på daglig basis.Kringverktyg skapade för t.ex. import av modeller, utdata i form av rumsakustiska parametrar,grafer och ljudfiler redovisas inte i detalj i denna rapport eftersom dessa ligger utanförexamensarbetet.

Les systèmes d'assistance a la réverbération sont des dispositifs électroacoustiques installés dans les salles de spectacle pour moduler leur acoustique en fonction du type de représentation qui s'y déroule. Afin de pouvoir dimensionner ces systèmes en amont de leur installation, ce travail s'intéresse au développement, à la mise en œuvre et à la mise à l'épreuve de modèles prévisionnels de l'effet de ses systèmes sur les caractéristiques acoustiques d'une salle, en se concentrant sur les systèmes dits régénératifs diagonaux. Le premier modèle présenté est basé sur une approche systémique exacte et sur l'utilisation de simulations numériques. Il s'agit d'un modèle dont le principe est déjà décrit dans la littérature spécialisée, mais auquel est intégré ici un algorithme de détermination automatique des paramètres de réglage d'un système d'assistance à la réverbération reproduisant la méthode manuelle. Parce que l'utilisation de simulations numériques impose une modélisation détaillée de la salle et un important temps de calcul, ce modèle n'est pas compatible avec la réactivité demandée lors d'une phase d'avant-projet. Dans cette optique, deux autres modèles bases sur les hypothèses de champ diffus et, par là même, plus rapides d'exécution, sont développés. L'un repose aussi sur une approche systémique exacte, mais utilise la théorie stochastique de l'acoustique géométrique des salles plutôt que des simulations numériques. L'autre repose sur une approche énergétique simple. Les confrontations de ces deux modèles avec celui reposant sur des simulations numériques sont exposées pour cinq salles, en considérant la prévision d'évolution de six indices acoustiques courants due à l'introduction d'un système d'assistance à la réverbération. Il en ressort que ces deux modèles aboutissent à des erreurs prévisionnelles comparables et que celles-ci sont équivalentes à celles des formules de Sabine ou d'Eyring ou de la théorie révisée des champs diffus de Barron et Lee appliquées dans une salle sans système. Parallèlement, l'étude et la prévision de l'effet d'un système d'assistance à la réverbération régénératif en augmentation du couplage de deux espaces mal couples au sein d'une même salle sont présentées. Il est montré que ce type d'utilisation permet effectivement une augmentation du couplage et que celle-ci peut être correctement abordée à partir d'un modèle énergétique développé ici. Il est aussi montré à partir de simulations numériques, que cette utilisation permet d'homogénéiser les caractéristiques acoustiques entre les deux espaces couplés.

Une methode geometrique de propagation de cones associee a des techniques de traitement de signal est utilisee pour calculer la reponse impulsionnelle binaurale d'une salle de spectacle, c'est a dire les deux reponses impulsionnelles entre la source et le conduit auditif de chacune des oreilles d'un auditeur dans la salle. Des tests d'ecoute de salles non encore construites peuvent etre realises en convoluant les reponses impulsionnelles avec des enregistrements musicaux effectues en salle sourde. Ce travail a necessite la mesure des fonctions de transfert de l'oreille externe. En complement a ces mesures une etude statistique de ces fonctions a ete menee a l'aide l'analyse en composantes independantes afin de trouver un jeu de fonctions de base independant de la personne

Ce travail porte sur la simulation de champs sonores de haute qualité pour des applications graphiques interactives. Dans ce cadre, nous nous sommes intéressé à trois problèmes : le calcul interactif des effets de l'occultation des ondes sonores par des obstacles, l'intégration du son dans un système d'animation et de réalité virtuelle et la simulation adaptative des réflections du son dans des environnements réverbérants. Nous présentons une méthode originale permettant d'approcher les effets des obstacles sur la propagation des ondes sonores. Cette méthode qualitative est fondée sur le calcul de l'obstruction des premiers ellipsoïdes de Fresnel. Pour cela nous utilisons le rendu câblé des cartes graphiques spécialisées pour effectuer un calcul interactif entre une source et un récepteur ponctuels dans des environnements généraux. Une extension plus quantitative, basée sur la théorie de Fresnel-Kirchhoff est également décrite. Nous décrivons également un système interactif de simulation acoustique. Il permet le rendu synchronisé du son et de l'image dans le cadre d'applications d'animation de synthèse et de réalité virtuelle. Nous y avons intégré notre approche de traitement des occultations sonores. Nous présentons comment d'autres effets, comme les réflections spéculaires du son ou l'effet Doppler sont également pris en compte. Enfin, nous introduisons une technique originale de simulation adaptative fondée sur un formalisme proche de la radiosité hiérarchique utilisée en synthèse d'images. Elle permet de prendre en compte efficacement des réflections globales spéculaires et diffuses dans le cadre d'échanges énergétiques dépendants du temps. La solution obtenue est indépendante du point d'écoute et ouvre la porte à des applications de parcours interactifs de l'environnement virtuel. En outre, la complexité du processus peut être contrôlée, permettant des applications plus quantitatives, comme la prévision des qualités acoustiques de lieux d'écoute. Ces trois contributions peuvent permettre de réaliser un système de simulation complet d'une scène sonore virtuelle pouvant être utilisé dans une variété d'applications. Celles-ci ne se limitent toutefois pas à l'acoustique, mais peuvent être étendues à la simulation de propagation d'ondes radioélectriques pour la téléphonie mobile ou les réseaux sans fils.

Cette these contribue a l'etude du controle actif de l'acoustique d'une salle en utilisant des systemes electroacoustiques. L'idee essentielle est de constituer des murs actifs par un assemblage de cellules elementaires afin de changer la repartition energetique d'une salle. Chaque cellule doit permettre de regler le niveau de retour du haut-parleur a une valeur desiree tout en controlant la stabilite du systeme. Un ensemble des cellules convenablement couplees pourra alors controler le coefficient de reflexion globale d'un mur actif. Par consequent, le temps de reverberation et les premieres reflexions d'une salle seront controles. Une structure d'une cellule elementaire du systeme de mur actif est proposee. Deux filtres adaptatifs sont introduits pour controler respectivement la stabilite et le niveau de retour d'une cellule du systeme. Les algorithmes de calcul des deux filtres adaptatifs sont presentes. Les principaux resultats theoriques sont illustres sur des simulations. Le probleme de l'organisation des cellules d'un systeme de mur actif en vue de reconstituer un champ sonore le plus naturel possible a ete aborde. Les resultats de simulation de deux types de murs (un mur actif et un vrai mur de meme dimension) ont ete compares. La faisabilite pratique est discutee. Une realisation temps reel d'une cellule a ete implantee sur une carte specialisee (tms 320c30). Les performances du prototype d'une cellule sont testees notamment en ce qui concerne la stabilite d'un couple microphone haut-parleur. Un calcul acoustique theorique sous des hypotheses simplificatrices est donne. Nous pouvons donc evaluer en fonction du nombre de cellules le temps de reverberation d'une salle a partir de caracteristiques mesurees dans cette salle. Enfin un premier prototype simplifie d'un mur actif est presente

碩士
高苑科技大學
建築研究所
100
Good quality of indoor acoustic environment is an important factor for audience, includes both room acoustics and noise control. In performing art halls, good room-shaped design in order to prevent acoustic obstacles, and suitable interior decoration could create a better room acoustics to achieve the listening quality. There are some factors those affect room acoustical quality. This research changes the side walls of the concert hall and the stage reflectors to simulate the influences of room acoustics. In this study, Tainan Municipal Cultural Center is chose for sample of simulation, discuss the various side walls of concert hall and stage ceiling reflectors and different materials in the patterns by using the software ODEON. This study proposed the best optimum pattern to provide application for designers and users and recommended the simulation method for indoor acoustics of designing domestic concert halls. Keywords: Side wall of auditorium, Stage reflector, Acoustic design, Room Acoustics, Computer Simulation

Dissertação de Mestrado em Eficiência Acústica e Energética para uma Construção Sustentável apresentada à Faculdade de Ciências e Tecnologia
A reabilitação e requalificação do património edificado tem vindo a assumir um peso crescente na construção em Portugal. Em edifícios antigos, em particular quando se pretende uma alteração profunda das suas funções e a adaptação a recintos com elevadas exigências de conforto acústico, como são exemplo os auditórios e grandes salas polivalentes, é fundamental um estudo de condicionamento acústico aprofundado e uma forte interacção com as restantes especialidades envolvidas, garantindo a manutenção do valor patrimonial do edifício.Quando os edifícios se revestem de adicional importância, como é o caso de edifícios com elevado valor histórico, há especificidades que requerem investigação adicional nos âmbitos da história e da arquitectura.No presente trabalho, procuraram-se estratégias de condicionamento acústico adequadas à reabilitação de salas e edifícios de elevado valor histórico.Usou-se para tal um caso de estudo: o edifício da igreja do Colégio da SS. Trindade. Um edifício do séc. XVII ao estilo arquitectónico maneirista que agora cumpre a função de Grande Auditório da Casa da Jurisprudência, integrada na Faculdade de Direito da Universidade de Coimbra. Este espaço sofreu recentemente uma reabilitação durante a qual foram introduzidos alguns revestimentos com elevada absorção sonora, com o intuito de reduzir o tempo de reverberação.Foram feitas medições acústicas no auditório vazio. Recolheram-se os resultados de parâmetros relativos ao tempo de reverberação e à definição e inteligibilidade da palavra. Analisou se o campo sonoro do auditório e a sua geometria complexa, e identificaram-se os desafios acústicos existentes.Conhecendo o programa e os objectivos do utilizador final daquele espaço, um auditório maioritariamente dedicado à palavra, traçaram-se os objectivos acústicos e determinaram se as métricas ideais a alcançar.Para poder testar as estratégias desenvolvidas construiu-se um modelo numérico do auditório nas condições actuais, num programa de acústica de traçado de raios. A construção deste modelo necessitou da recolha de informação de projecto, no local e bibliográfica. De seguida, o modelo foi calibrado ajustando os coeficientes de absorção sonora dos materiais de revestimento das superfícies, minimizando o erro entre o tempo de reverberação simulado e medido, em cada banda de oitava de frequência. Foram ainda simulados os restantes parâmetros acústicos para comparação com os valores medidos, tendo-se verificado genericamente uma boa correlação.Avançou-se então para a investigação da história da igreja, no sentido de perceber as limitações na procura de soluções, por forma a respeitar o valor histórico e compatibilizar as estratégias com a arquitectura original e a arquitectura da reabilitação. Estas limitações podem ocorrer ao nível de elementos móveis ou fixos, de tipos de materiais e aparência, de contemporaneidade e anacronismo.Procedeu-se ao desenvolvimento de estratégias e definição e materialização de propostas de soluções para melhorar o desempenho acústico do auditório. Estas propostas foram testadas no modelo numérico e os resultados apresentados e analisados.Finalmente, foram tiradas conclusões e apresentados desenvolvimentos futuros.
The rehabilitation and requalification of the built heritage assumes an increasing weight in the construction industry in Portugal. In historic buildings, in particular when there is a deep change of its function and transformation to halls with high quality acoustics is required, such as auditoriums and large multipurpose halls, a thorough acoustics study and a strong interaction with other design stakeholders is mandatory, in order to safeguard that historical value.When buildings are of major importance, such as those with high historical value, there are specifics that require additional research in the fields of history and architecture.In this dissertation, room acoustics strategies were developed, in accordance with the rehabilitation of such kind of rooms or buildings, of high historical value.A case study was used: the church building of the Colégio da SS. Trindade. A 16th century church, of Mannerist architectural style that has been transformed to a grand auditorium of the Casa da Jurisprudência, integrated in the Faculdade de Direito da Universidade de Coimbra. This space has recently undergone a rehabilitation during which some lining materials with high sound absorption were installed, with the purpose of reducing the reverberation time.Acoustic field measurements were carried out in the auditorium, empty. The results of the reverberation time were taken, as well as for the definition and intelligibility of speech. The auditorium's sound field was assessed along with its complex geometry, and existing acoustic challenges were identified.Knowing that this auditorium is mainly dedicated to speech events, the acoustic objectives were defined and the metrics to be achieved were determined.In order to test the strategies developed, a computational model of the auditorium was created in its current conditions, using a ray tracing software. The creation of this model required the collection of design information, on-site surveys and bibliographical survey. Following that, the model was calibrated by adjusting the sound absorption coefficients of the surfaces materials, and thus minimizing the error between the simulated and measured reverberation times in each frequency octave band. Other acoustic parameters were also simulated for comparison with the measured values, and a good overall correlation was obtained.The next step was to survey the history of the church in order to perceive the constraints of the solutions, so that the historical value is preserved and the strategies embed with the original architectural design and the rehabilitation architectural design. These limitations can be of mobile or fixed features, types of materials and its appearance, contemporaneity and anachronism.Strategies were developed and solutions to improve the acoustic performance of the auditorium were proposed. These proposals were then tested in the computational model and the results presented and analysed.Finally, conclusions to this study were drawn and future developments were presented.