• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 6
  • 6
  • 3
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Proposição de algoritmo para avaliação da qualidade acústica em ambiente escolar / Proposition of algorithm for evaluation of acoustic quality in school enrironment

Reginaldo Costa 11 June 2008 (has links)
Este trabalho estuda as relações existentes entre a qualidade acústica dentro de um ambiente construído - salas de aula da rede pública estadual - o desempenho escolar alcançado pelos alunos, a qualidade de vida do professor neste ambiente de trabalho e a percepção por parte da sociedade sobre os problemas causados pelo excesso de ruído. Trata-se mais especificamente da proposição de um algoritmo que possibilite ao administrador escolar verificar a qualidade acústica das salas de aula e de elaborar um plano de trabalho que vise sanar os problemas detectados. A sala de aula é um ambiente que merece uma atenção especial no quesito acústica. Neste espaço, a transmissão do conhecimento se realiza, em sua maioria, através da fala e num ambiente comprometido acusticamente o resultado final é diretamente influenciado pela sua qualidade. Salas de aula com baixa qualidade acústica geram prejuízos aos alunos em relação ao processo de ensino-aprendizagem e ao professor no que se refere a sua saúde vocal. Através da aplicação do algoritmo, o administrador escolar envolve toda a comunidade escolar na busca de dados que possibilite uma análise detalhada da situação da escola. Este envolvimento coletivo possibilita que as ações elaboradas e implementadas sejam mais facilmente acatadas por todos, pois os envolvidos apresentam-se representados no processo de coleta de dados e tomada de decisões. / This work studies the relationships found among these elements: the acoustic quality of a building - classrooms in public schools, the students performance, the teachers life quality, the perception from society on the problems caused by the noise excess. It deals more specifically with the proposition of an algorithm that makes possible the school administrator verify the acoustic quality of the classrooms and elaborate a work plan that intended to solve the detected problems. The classroom is a place that deserves special attention in the acoustics conditions. In this space the exchange of knowledge takes place in its majority through the speech and in an atmosphere acoustically disturbed, the final result is influenced directly by its quality. Classrooms with low acoustic quality generate damages to the students teaching-learning process and to the teachers vocal health. Through the application of the algorithm the school administrator involves the whole school community in the search of data that makes possible a detailed analysis of the situation of the school. This collective involvement makes actions more easily accepted by all, because all the people involved are represented in the process of data collection and in the decisions taken.
2

Využití dlouhodobé formantové distribuce pro rozpoznatelnost mluvčího v různých akustických podmínkách / Using long-term formant distributions for speaker identification in various acoustic conditions

Lazárková, Dita January 2015 (has links)
The analysis of long-time formant distribution is relatively young but promising discipline of speaker identification. It is a method of mapping the long-term behavior of formants in speech of individual speakers. Frequently encountered problems in practice are bad acoustic quality and very short duration of analyzed recordings. This work aims to present the historical development of forensic phonetics and currently used methods. In the practical part, it deals with the usability of LTF method in forensic practice, especially in recordings containing background noise. It was shown that the noise appreciably affects extracted LTF values and unfortunately the change is not systematic. Therefore, we proposed several methods to compensate the noise in recordings, in order to be able to compare recordings with and without noise. We also investigated the minimum duration of recording, which is necessary for statistical reliability of the resulting values. This boundary is not exact and for each speaker, it is substantially individual. But it is apparent that recordings (vocalic streams) shorter than 15 s often provide incomplete information, wherefore they cannot be recommended for analysis. Keywords: LTF, long-time formant distribution, speaker identification, forensic phonetics, acoustic quality of...
3

Framtagning av en ljudanalysmetod för bedömning av ljudkvalitet i urbana utomhusmiljöer / Developing of a sound analysis method for assessment of acoustic quality

Heitmann, Simon January 2018 (has links)
Buller är en av de miljöföroreningar som har störst negativ påverkan på männi-skors hälsa. Några av dessa effekter är sömnstörningar, stress och i vissa fall kan detleda till hjärt- och kärlsjukdomar. Problematiken kring detta växer med en ökandebefolkningsmängd och urbanisering runt om i världen. Denna studie undersöker möj-ligheterna till att utveckla en ny ljudanalysmetodik för hållbara stadsmiljöer. Idag utförs trafikbullerutredningar som en del i miljökonsekvensbeskrivningar. Dessaanalyser innehåller i huvudsak en ljudnivåberäkning från de primära bullerkällornaoch dessa kopplas till gällande riktvärden för A-vägda ljudnivåer vid uteplatser ochfasader. Forskning kring urbana ljudmiljöer visar att endast ljudnivåerna från buller-källor inte är tillräckligt för att avgöra ljudkvaliteten. Bullrets relativa inblandning iljudmiljön, dess frekvensområde och tidsvariation samt platsens syfte och användningär faktorer som dels är kopplade till hur pass väl bullret maskeras, och dels hur passstörande ljudet faktiskt upplevs. Alla dessa faktorer behöver vägas in för att på bästasätt kunna bedöma ljudkvaliteten. Strategin som användes i denna studie bestod dels av en litteraturstudie där till-gänglig forskning kring urbana ljudmiljöer analyserades och dels i en fallstudie därtre olika typfall av urbana miljöer modellerades i det akustiska modelleringsprogram-met Olive Tree Lab. De tre fallen utgjordes av teoretiska platser, ett öppet gaturum,ett stängt gaturum samt ett gaturum med torg på ena sida. Utformningen av des-sa valdes utifrån att det är några av de vanligast förekommande urbana miljöernadär höga ljudnivåer uppstår. Utifrån litteraturstudien togs en beskrivningsmall förljudmiljöer som utgör den nya ljudanalysmetoden fram som sedan applicerades påfallstudien för analys och utvärdering. Mallens tyngdpunkt låg på att undersöka så-väl goda som negativa ljud och att koppla det till den platsen som analysen avser.Resultaten visade på att användning av mallen leder till en bredare och mer detalje-rad beskrivning av ljudmiljön som möjliggör flera olika typer av lösningar än de somföreslås idag. / Noise is one of the environmental pollutions that has the largest negative effect onhuman health. Some of these effects are stress, sleeping issues and in some cases itcan cause cardiovascular diseases. The problem about this is growing as a result froman increasing population and an increasing urbanization. This study investigates thepossibilities to develop a new sound analysis method for urban environments. Today traffic noise investigations are performed as a part of environmental impact as-sessments. These analyses comprise most of sound level calculations from the primarynoise sources, which are then connected to the existing benchmarks for A-weightedsound levels at patios and facades. Research around urban sound environments showsthat only taking the sound levels exceeded from the primary noise sources in con-sideration is an insufficient method for estimating the sound quality. The relativeinvolvment of the noise, the range of frequencies and the variation in time as well,as the purpose and use of the area, are factors which are all connected to how wellthe noise is masked, as well as how disturbing the noise is actually percieved as. Allthese factors have to be taken into consideration in order to assess the sound qualityin the best posssible way. The method used in this study consisted of two main parts; one literature study,where available research around urban sound environments was analysed; and onecase study where three different cases of urban environments were analyzed in theacoustic modeling program Olive Tree Lab. The three cases consisted of theoreticallocations, one open street canyon, one closed and one street canyon with a squareon one side. Based on the literature study a description template for sound environ-ments was developed and applied to the cases from the case study for analysis andevaluation. The main focus of the template was to investigate both positive and ne-gative sounds and relate them to the site of which the sound analysis is intended for.The results showed that use of the template resulted in a broader and more detaileddescription of the sound environment, which enabled different kinds of solutions thatare not commonly used today.
4

Optics and acoustics with a single nano-object : environment effects / Optique et acoustique avec un nano-objet individuel : effets d'environnement

Medeghini, Fabio 26 February 2018 (has links)
Dans cette thèse, les propriétés d'une nanoparticule unique ont été réglée en modifiant son environnement.Plus spécifiquement, dans la première partie de ce travail, la résonance des plasmons de surface des nanobipyramides d'or individuelles a été étudié expérimentalement dans un milieu sous pression contrôlable et son évolution encadré par modélisations théoriques.Afin d'accéder à l'optique d'une nanoparticule unique tout en générant un environnement sous haute-pression, la combinaison de la spectroscopie par modulation spatial avec la cellule en enclume de diamant a été atteint.Dans la seconde partie de la thèse, les vibrations acoustiques des nanodisques d'or individuels sur a substrat en saphir ont été caractérisé expérimentalement via spectroscopie pump&probe. Une attention particulière a été accordée à leur amortissement en fonction du rapport d'aspect des disques en soulignant la présence des amplifications en factor de qualité.Modélisations numériques ont fourni un aperçu des amplifications observées, montrant que l'hybridations entre modes se produit pour rapport d'aspect spécifiques, potentiellement en atténuant les pertes en énergie acoustique à travers l'interface disque/substrat / In this thesis, the properties of a single nanoparticle have been tuned altering its environment. Specifically, in the first part of this work, the surface plasmon resonance of individual gold nanobipyramids has been experimentally studied under a pressure adjustable surrounding and its evolution physically framed thorough theoretical modeling.In order to access to the single nanoparticle optics while generating a hydrostatic high-pressure environment, a challenging combination of the spatial modulation spectroscopy technique with the diamond anvil cell method has been achieved.In the second part of the thesis, the acoustic vibrations of individual gold nanodisks on sapphire substrate has been experimentally characterized via pump&probe spectroscopy. Particular attention has been paid to their damping as a function of the disks aspect-ratio enlightening the presence of quality-factors enhancements.Numeric modeling has provided a physical insight for the observed amplifications, showing that modes hybridizations occur at specific aspect-ratios, potentially reducing the acoustic energy loss towards the interface disk/substrate
5

Modelagem acústica de salas através da técnica de malhas de guias digitais de ondas / Acoustic room modelling using a digital waveguide mesh technique

Boaventura, Ana Paula Freitas Vilela 30 January 2014 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The modeling of reverberant environments using techniques based on geometry, such as Ray Tracing or behavior-based wave, such as Finite Elements are devoted respectively to large and small places . But the great difficulty arises in the simulation of medium enclosures, based on precision to the geometrical approach and the computational cost for the behavior-based wave. Therefore, the objective of this work is to obtain Impulse Response Room (Room Impulse Response - RIR ) in midsize through technical Digital Waveguide Mesh ( Digital Waveguide Mesh - DWG ) environments . During the simulations the excitation was made by a half-sine, representing an approximation of the Dirac Delta. To simulate the reverberant field, were explored different geometries of meshes. Applying the results obtained it was possible to predict numerically the acoustic behavior of a sample of the same audio playing through the auralization. Added to this, certain parameters of acoustic quality which are directly derived from the RIR could be calculated . Finally, a comparative study of the RIR obtained experimentally , theoretically and via DWG was performed . From the initial proposal of the work , we have reached a computational tool able to predict the acoustic behavior in two and three dimensional environments , a relatively low computational time and quality in their results . Therefore , it was possible to make a preliminary analysis of the acoustic quality of the room , including allowing the sound reproduced in the virtual room. / A modelagem de ambientes reverberantes por meio de técnicas baseadas na geometria, como o Ray Tracing ou na propagação de ondas acústica, como Elementos Finitos são consagrados respectivamente para recintos de grande e pequeno porte. Porém, a grande dificuldade reside na simulação dos recintos médios, em função da precisão, para a abordagem geométrica, e do custo computacional, para os baseados no comportamento da onda. Assim sendo, o objetivo deste trabalho consiste na obtenção da Resposta Impulsiva da Sala (Room Impulse Response RIR) em ambientes de médio porte por meio da técnica de Malhas de Guias Digitais de Ondas (Digital Waveguide Mesh DWG). Durante as simulações a excitação se deu por meio de um meio seno, representando uma aproximação do Delta de Dirac. Para simular o campo reverberante, foram exploradas diferentes geometrias de malhas. Aplicando os resultados obtidos numericamente foi possível prever o comportamento sonoro de uma amostra de áudio sendo reproduzida no mesmo, por meio da auralização. Somado a isso, certos parâmetros da qualidade acústica, que são diretamente derivados da RIR puderam ser calculados. Para finalizar, um estudo comparativo das RIR obtidas experimentalmente, teoricamente e via DWG foi realizado. A partir da proposta inicial do trabalho, chegou-se a uma ferramenta computacional capaz de prever o comportamento acústico em ambientes bi e tridimensionais, num tempo computacional, relativamente baixo e com qualidade em seus resultados. Por conseguinte, foi possível fazer uma análise prévia da qualidade acústica da sala, inclusive permitindo ouvir o som reproduzido no recinto virtual. / Doutor em Engenharia Mecânica
6

Revisión de los valores del espectro de absorción de la caja de escena en teatros, mediante la aplicación del método de superficies de respuesta

Pérez Aguilar, Blanca Natividad 07 September 2023 (has links)
[ES] El comportamiento acústico de una sala viene determinado, entre otros factores, por el coeficiente de absorción acústica de las soluciones constructivas de las superficies interiores que lo forman. El coeficiente de absorción se halla a través de ensayos de laboratorio o de las propuestas de la literatura científica. En teatros habitualmente el volumen de la caja de escena es equiparable sino superior al volumen de la sala propiamente dicho, y se comunica con la sala a través de la boca de escena. Para calcular el comportamiento acústico de un teatro no se tiene en cuenta el volumen de la caja de escena, sino que éste se sustituye en el modelo por la superficie de la boca de escena. El coeficiente de absorción de la boca de escena se toma de la literatura científica. Siendo la boca de escena un gran vacío, no es posible encontrar sus valores de absorción en laboratorio. Se desconoce cómo los distintos autores que han propuesto valores para el coeficiente de absorción de la boca de escena han llegado a dichos valores. En el presente trabajo se ha hallado el coeficiente de absorción de la boca de escena de seis teatros de diferentes características y épocas. Para ello, se ha recopilado información gráfica y constructiva de los espacios, se han realizado mediciones acústicas normalizadas con la boca de escena abierta y cerrada, y se han elaborado modelos informáticos tridimensionales que han sido calibrados con las mediciones tomadas "in situ". En una primera fase se ha calibrado el modelo con la boca de escena cerrada y en una segunda se ha repetido el proceso con la boca de escena abierta. El ajuste de los modelos virtuales se ha ejecutado mediante el empleo del método de las superficies de respuesta. Este método ha permitido considerar hasta dos soluciones constructivas con comportamiento acústico desconocido. De esta forma se ha podido deducir el coeficiente de absorción de la boca de escena en cada caso. Finalmente, los coeficientes de la boca de escena hallados en cada teatro se han comparado con los propuestos por diversos autores. Además, se ha evaluado la influencia de la absorción de la boca de escena en cada modelo. Constatando que los valores propuestos en las obras de referencia son adecuados en teatros antiguos, no así en los modernos en los que son válidos sólo en frecuencias medias y altas. / [CA] El comportament acústic d'un espai ve determinat, entre altres factors, pel coeficient d'absorció acústica de les solucions constructives de les superfícies interiors que el formen. El coeficient d'absorció és troba mitjançant assajos de laboratori o de les propostes de la literatura científica. En teatres habitualment el volum de la caixa d'escena és equiparable, sinó superior al volum de la sala, i es comunica amb la sala mitjançant la boca d'escena. Per calcular el comportament acústic d'un teatre no es té en compte el volum de la caixa d'escena, sinó que es substitueix al model per la superfície de la boca d'escena. Com que la boca d'escena és un gran buit, no és possible trobar els seus valors d'absorció al laboratori. Perla qual cosa els seus valors es prenen de la literatura científica Es desconeix com els autors que han proposat valors per al coeficient d'absorció de la boca d'escena han arribat a aquests valors. En aquest treball s'ha trobat el coeficient d'absorció de la boca d'escena de sis teatres de característiques i èpoques diferents. Per fer-ho, s'ha recopilat informació gràfica i constructiva dels espais, s'han realitzat mesures acústics normalitzades amb la boca d'escena oberta i tancada, i s'han elaborat models informàtics tridimensionals que han estat calibrats amb les mesures preses "in situ". En una primera fase el model s'ha calibrat amb la boca d'escena tancada i en una segona s'ha repetit el procés amb la boca d'escena oberta. L'ajust dels models virtuals s'ha executat mitjançant la utilització del mètode de les superfícies de resposta. Aquest mètode ha permès considerar fins a dues solucions constructives amb un comportament acústic desconegut. D'aquesta manera, s'ha pogut deduir el coeficient d'absorció de la boca d'escena en cada cas. Finalment, els coeficients de la boca d'escena trobats a cada teatre s'han comparat amb els proposats per diversos autors. A més, s'ha avaluat la influència de l'absorció de la boca d'escena a cada model. Constatant que els valors proposats a les obres de referència són adequats en teatres antics, no així als moderns en què són vàlids només en freqüències mitjanes i altes. / [EN] The acoustic behavior of a room is determined, among other factors, by the acoustic absorption coefficient of the interior surfaces that make it up. The absorption coefficient is found through laboratory tests or proposals from the scientific literature. In theaters, the volume of the stage house is usually equivalent to the volume of the room itself, if not greater; and it is connected to the room through the proscenium opening. To calculate the acoustic behavior of a theater, the volume of the fly tower is not considered, but instead it is replaced in the model by the surface of the stage opening. Since the proscenium opening is a large recess, it is not possible to find its absorption values in the laboratory; that's why they are taken from the scientific literature. It is not known how the different authors who have proposed values for the absorption coefficient of the stage opening have found these values. In the present work, the absorption coefficient of the proscenium opening of six theaters of different characteristics and periods has been found. For this, graphic and constructive information of the spaces has been compiled, standardized acoustic measurements have been made with the stage opening opened and closed, and three-dimensional computer models that have been calibrated with the on-site measurements have been prepared. In the first phase, the model has been calibrated with the stage opening closed and in the second one the process has been repeated with the stage opening opened. The adjustment of the virtual models has been carried out using the response surface method. This method has allowed to consider up to two constructive solutions with unknown acoustic behavior. This way it has been possible to deduce the absorption coefficient of the stage opening in each case. Finally, the coefficients of the proscenium opening found in each theater have been compared with those proposed by several authors. In addition, the influence of the absorption of the stage opening in each model has been evaluated. Noting that the values proposed in the reference works are adequate in old theaters, but not in modern ones, where they are valid only in medium and high frequencies. / Pérez Aguilar, BN. (2023). Revisión de los valores del espectro de absorción de la caja de escena en teatros, mediante la aplicación del método de superficies de respuesta [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/196753

Page generated in 0.0573 seconds