In the context of interior noise reduction, the present work aims at proposing Finite Element (FE) solution strategies for interior structural-acoustic applications including 3D modelling of homogeneous and isotropic poroelastic materials, under timeharmonic excitations, and in the low frequency range. A model based on the Biot-Allard theory is used for the poroelastic materials, which is known to be very costly in terms of computational resources. Reduced models offer the possibility to enhance the resolution of such complex problems. However, their applicability to porous materials remained to be demonstrated.First, this thesis presents FE resolutions of poro-elasto-acoustic coupled problems using modal-based approaches both for the acoustic and porous domains. The original modal approach proposed for porous media, together with a dedicated mode selection and truncation procedure, are validated on 1D to 3D applications.In a second part, modal-reduced models are combined with a Padé approximants reconstruction scheme in order to further improve the efficiency.A concluding chapter presents a comparison and a combination of the proposed methods on a 3D academic application, showing promising performances. Conclusions are then drawn to provide indications for future research and tests to be conducted in order to further enhance the methodologies proposed in this thesis.

Reducing interference noise in a noisy speech recording has been a challenging task for many years yet has a variety of applications, for example, in handsfree mobile communications, in speech recognition, and in hearing aids. Traditional single-channel noise reduction schemes, such as Wiener filtering, do not work satisfactorily in the presence of non-stationary background noise. Alternatively, supervised approaches, where the noise type is known in advance, lead to higher-quality enhanced speech signals. This dissertation proposes supervised and unsupervised single-channel noise reduction algorithms. We consider two classes of methods for this purpose: approaches based on nonnegative matrix factorization (NMF) and methods based on hidden Markov models (HMM).  The contributions of this dissertation can be divided into three main (overlapping) parts. First, we propose NMF-based enhancement approaches that use temporal dependencies of the speech signals. In a standard NMF, the important temporal correlations between consecutive short-time frames are ignored. We propose both continuous and discrete state-space nonnegative dynamical models. These approaches are used to describe the dynamics of the NMF coefficients or activations. We derive optimal minimum mean squared error (MMSE) or linear MMSE estimates of the speech signal using the probabilistic formulations of NMF. Our experiments show that using temporal dynamics in the NMF-based denoising systems improves the performance greatly. Additionally, this dissertation proposes an approach to learn the noise basis matrix online from the noisy observations. This relaxes the assumption of an a-priori specified noise type and enables us to use the NMF-based denoising method in an unsupervised manner. Our experiments show that the proposed approach with online noise basis learning considerably outperforms state-of-the-art methods in different noise conditions.  Second, this thesis proposes two methods for NMF-based separation of sources with similar dictionaries. We suggest a nonnegative HMM (NHMM) for babble noise that is derived from a speech HMM. In this approach, speech and babble signals share the same basis vectors, whereas the activation of the basis vectors are different for the two signals over time. We derive an MMSE estimator for the clean speech signal using the proposed NHMM. The objective evaluations and performed subjective listening test show that the proposed babble model and the final noise reduction algorithm outperform the conventional methods noticeably. Moreover, the dissertation proposes another solution to separate a desired source from a mixture with arbitrarily low artifacts.  Third, an HMM-based algorithm to enhance the speech spectra using super-Gaussian priors is proposed. Our experiments show that speech discrete Fourier transform (DFT) coefficients have super-Gaussian rather than Gaussian distributions even if we limit the speech data to come from a specific phoneme. We derive a new MMSE estimator for the speech spectra that uses super-Gaussian priors. The results of our evaluations using the developed noise reduction algorithm support the super-Gaussianity hypothesis. / <p>QC 20130916</p>

No description available.

Syfte: När städerna växer i allt snabbare takt behövs nya platser att bygga bostäder på. De kommuner som växer väljer allt oftare att bebygga platser som tidigare ratats på grund av bland annat buller. Från statens sida finns det krav på hur stor bullernivån får vara. Kraven har sitt ursprung i att över två miljoner svenskar utsätts för buller dagligen. Buller kan leda till hälsoproblematik, i form av sömnstörningar och hjärt- och kärlsjukdomar. För att minska hälsoproblemen görs bullerutredningar, där förslag hur bullernivåerna kan minskas ges. Syftet med arbetet är att ge läsaren kunskap i vilka faktorer som påverkar bullerutredningar och tillvägagångssättet vid valet av bullerreducerande åtgärder så att byggnation närmare trafikerad väg kan möjliggöras. Metod: De metoder som använts i arbetet är litteraturstudie, dokumentanalys och intervjuer. Den litteratur som samlats in består av vetenskapliga artiklar. Dokumenten består av bullerutredningar genomförda av olika företag på olika platser i Sverige. Utifrån bullerutredningarna har personer att intervjua valts. De personer som intervjuats har utfört några av de bullerutredningar som använts i dokumentanalysen. Resultat: För att besvara rapportens syfte ställdes tre frågeställningar upp. Den första frågeställningen behandlar bullerreducerande tekniker, vilka tekniker som används idag. I rapporten framkom det att det finns ett flertal sätt att reducera buller. I följande ordning rangordnas de som mest frekvent använda: tyst sida, bullerskärm, hastighetsminskning, avstånd mellan hus och väg, vegetation, flytt av väg och tyst asfalt. I rapportens andra frågeställning behandlas vilka faktorer som påverkar valet av bullerreducerande åtgärd. Från litteraturstudien framkom absorption, reflektion och reduktion som viktiga faktorer. I dokumentanalysen framkom omgivning, trafik och hastighet som viktiga faktorer. I intervjuerna framkom estetik och pris som viktiga vid val av reducerande åtgärd. I den tredje frågeställningen behandlas frågan om hur byggnation närmare väg kan möjliggöras. I resultatet framkommer det att alla lösningar som tidigare nämnts har förmåga att reducera buller, men hur effektiva de är och hur bra de reducerar buller varierar från fall till fall. Omgivning och trafikmängd har stor betydelse. Konsekvenser: Att utnyttja de tekniska lösningar som tidigare beskrivits ger en minskad bullernivå och således kan byggnation nära trafikerad väg möjliggöras. Att utföra en bullerutredning i ett tidigt skede medför att senare och dyrare ändringar kan undvikas, vilket gör att byggnationen kan ske snabbare. Rapporten föreslår att bullerproblematiken ska beaktas tidigt i projekt, detta för att skapa en lösning som alla i projektet kan acceptera. Begränsningar: Rapportens resultat är begränsat till ett mindre urval av bullerutredningar och intervjuer. Fler utredningar och intervjuer hade bidragit till ett större spektrum. Rapporten tar enbart hänsyn till buller utomhus och vilka möjligheter till bullerreduktion det finns. / Purpose: When cities grow at a faster rate, new places are needed to build housing.The municipalities that are growing tends to choose build sites that previously wererejected due to noise pollution. There are requirements from the state that the noise maynot exceed certain values. The requirements originate from the fact that over twomillion swedes are exposed to noise daily. Noise can lead to health problems, in theform of sleep disorders and cardiovascular disease. To reduce health problems noiseinvestigations are made, where suggestions are made in how noise levels can bereduced. The purpose of the work is to provide the reader with knowledge of whichfactors influence noise investigations and the approach to the choice of noise reductionmeasures so that construction can be made closer to trafficked roads. Method: The methods used are literature studies, document analysis and interviews.The literature gathered consists of scientific articles. The documents consist of noiseinvestigations conducted by different companies all over Sweden. Persons to interviewwere chosen from the conductors of the noise investigations documents. Findings: To answer the report's purpose, three questions were raised. The firstquestion deals with noise-reducing technologies and which technologies are used today.The report found that there are several ways to reduce noise. In the following order, themost frequently used are: silent facade, noise screen, speed reduction, distance betweenhouse and roads, vegetation, road moving and quiet asphalt. The second question of thereport addresses the factors that influence the choice of noise reduction measure. Fromthe literature study, absorption, reflection and reduction were found to be importantfactors. In the document analysis, surroundings, traffic and speed emerged as importantfactors. In the interviews, aesthetics and price emerged as important in the choice ofwhich reducing action should be taken. The third question deals with the question ofhow construction can be made closer to the road. In the result it appears that all of thesolutions mentioned earlier have the ability to reduce noise, but how effective they areand how well they reduce noise varies from case to case. Surroundings and trafficvolume are of great importance. Implications: Making use of the technical solutions previously described, results in areduced noise level and there for construction near road can be made possible.Executing a noise investigation at an early stage means that later and more expensivechanges can be avoided, which means that construction can take place sooner. Thereport suggests therefore that noise issues should be considered early in projects. It isalso important to get a solution that everyone can accept. Limitations: The report's results are limited to a smaller selection of noiseinvestigations and interviews. More investigations and interviews could hadcontributed to a larger spectrum. The report does only consider noise outdoors and whatopportunities for noise reduction there are.

Orientador: Jozué Vieira Filho / Banca: Suely Cunha Amaro Mantovani / Banca: Marco Aparecido Queiroz Duarte / Resumo: A proposta deste trabalho é aprimorar a performance da técnica de redução de ruído, subtração espectral baseado na relação SNR a Priori, através da implementação de dois novos parâmetros Potência de Articulação e Não-Articulação obtidas a partir de algumas técnicas psicoacústicas. Faz-se um estudo da anatomia do sistema de audição humana e algumas limitações físicas, com o objetivo de entender o princípio básico da técnica ANIQUE, que é um sistema de avaliação objetiva de voz e têm como princípio o modelamento da percepção humana da voz. Através do modelo ANIQUE são extraídas as principais técnicas psicoacústicas para obtenção dos novos parâmetros, Potência de Articulação e Não- Articulação. Procurou-se apresentar de maneira resumida o processo de equacionamento das técnicas de redução de ruído em sinais de voz e das técnicas psicoacústicas. Posteriormente são descritos todos os processos das técnicas utilizadas que foram simuladas utilizando a linguagem de programação do MatLab®, seguido das avaliações objetivas dos sinais processados pelo software PESQ, que é um programa de avaliação objetiva de voz. Os resultados mostram que a implementação das técnicas psicoacústicas foram eficazes para melhorar a performance da técnica subtração espectral baseada na relação SNR a Priori / Abstract: The purpose of this work is to enhance the performance of noise reduction techniques based on spectral subtraction, which take in account the a priori signal-to-noise (SNR a Priori) to be estimated considering psychoacoustic criteria. in order to understand the basic principle of the ANIQUE, which is a psychoacoustic based technique used to evaluate the quality of speech signals, it was necessary to develop a study of the anatomy of the human hearing and some physical limitations, From the ANIQUE are extracted new parameters namely Articulation and Non-Articulation Powers, used to estimate the SNR_prio. As a result, it was obtained a new spectral based technique which was implemented in the MatLab® environment and evaluated using the objective quality measure for speech signal simulations namely PESQ. The results show that the implementation of psychoacoustic techniques were effective in enhance the performance of the spectral subtraction technique based on SNR a Priori / Mestre

Made available in DSpace on 2014-06-11T19:29:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-25Bitstream added on 2014-06-13T19:59:46Z : No. of bitstreams: 1 kanda_az_me_ilha.pdf: 1642888 bytes, checksum: 49ebcd86d5690e7be50fcdca35a52a48 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A proposta deste trabalho é aprimorar a performance da técnica de redução de ruído, subtração espectral baseado na relação SNR a Priori, através da implementação de dois novos parâmetros Potência de Articulação e Não-Articulação obtidas a partir de algumas técnicas psicoacústicas. Faz-se um estudo da anatomia do sistema de audição humana e algumas limitações físicas, com o objetivo de entender o princípio básico da técnica ANIQUE, que é um sistema de avaliação objetiva de voz e têm como princípio o modelamento da percepção humana da voz. Através do modelo ANIQUE são extraídas as principais técnicas psicoacústicas para obtenção dos novos parâmetros, Potência de Articulação e Não- Articulação. Procurou-se apresentar de maneira resumida o processo de equacionamento das técnicas de redução de ruído em sinais de voz e das técnicas psicoacústicas. Posteriormente são descritos todos os processos das técnicas utilizadas que foram simuladas utilizando a linguagem de programação do MatLab®, seguido das avaliações objetivas dos sinais processados pelo software PESQ, que é um programa de avaliação objetiva de voz. Os resultados mostram que a implementação das técnicas psicoacústicas foram eficazes para melhorar a performance da técnica subtração espectral baseada na relação SNR a Priori / The purpose of this work is to enhance the performance of noise reduction techniques based on spectral subtraction, which take in account the a priori signal-to-noise (SNR a Priori) to be estimated considering psychoacoustic criteria. in order to understand the basic principle of the ANIQUE, which is a psychoacoustic based technique used to evaluate the quality of speech signals, it was necessary to develop a study of the anatomy of the human hearing and some physical limitations, From the ANIQUE are extracted new parameters namely Articulation and Non-Articulation Powers, used to estimate the SNR_prio. As a result, it was obtained a new spectral based technique which was implemented in the MatLab® environment and evaluated using the objective quality measure for speech signal simulations namely PESQ. The results show that the implementation of psychoacoustic techniques were effective in enhance the performance of the spectral subtraction technique based on SNR a Priori

Fluoroskopi är benämningen på kontinuerlig röntgengenomlysning av en patient. Eftersom patienten och även läkaren då utsätts för kontinuerlig röntgenstrålning måste strålningsdosen hållas låg, vilket leder till brusiga bilder. Det är därför önskvärt att genom bildbehandling förbättra bilderna. Bildförbättringen måste dock ske i realtid och därför kan inte konventionella metoder användas. Detta examensarbete avser att undersöka hur ortogonala s k. derivataoperatorer kan användas för att förbättra läsbarheten av fluoroskopibilder med hjälp av brusundertryckning och kantförstärkning. Derivataoperatorer är separerbara vilket gör dem extremt beräkningsvänliga och lätta att infoga i en skalpyramid. Skalpyramiden ger möjlighet att processa strukturer och detaljer av olika storlek var för sig samtidigt som nedsamplingsmekanismen gör att denna uppdelning inte nämnvärt ökar beräkningsbördan. I den fullständiga lösningen införes också struktur-/brusseparering för att förhindra förstärkning av och undertrycka bidrag från de frekvensband där en pixel domineras av brus. Resultaten visar att brus verkligen kan undertryckas medan kanter och linjer bevaras bra eller förstärkes om så önskas. Den riktade filtreringen gör dock att det lätt uppstår maskliknande strukturer i bruset, men detta kan undvikas med rätt parameterinställning av struktur-/brussepareringen. Förhållandet mellan riktad och icke-riktad filtrering är likaledes styrbart via en parameter som kan optimeras med hänsyn till behov och önskemål vid varje tillämpning. / In X-ray technology, fluoroscopy stands for continuous irradiation. For the sake of both patients and doctors the dose has to be kept low, which leads to noisy images and the question of possible enhancement by digital image processing. Since such enhancement has to be done in real-time, most conventional and available methods are unsuitable. The purpose of this thesis is to examine how derivative operators can be used to improve fluoroscopy images in terms of noise reduction and edge enhancement. Since the derivative operators are designed as highly separable convolution kernels the image derivatives can be computed very efficiently with a scheme that is readily embedded in a scale-space pyramid. In this pyramid, structures and details of different sizes can be processed separately with optimal parameter settings. In the final solution we also discriminate between structure and noise in order to avoid amplification, even suppress contributions from frequency bands where a certain pixel position is dominated by noise. Experimental results show that noise can indeed be suppressed while edges and lines are enhanced. Oriented filtering may induce false structures in areas where only noise is present, something that can be avoided by correcting the parameters in the noise/structure discriminator. The relation between oriented and non-oriented filtering is likewise controllable with a parameter that can be optimized for application dependent needs and desires.

Made available in DSpace on 2016-08-17T14:53:26Z (GMT). No. of bitstreams: 1 Dissertacao Aleksandro Costa.pdf: 1706153 bytes, checksum: 8d61027896dbab484303f78ed17b9b70 (MD5) Previous issue date: 2014-02-28 / FUNDAÇÃO DE AMPARO À PESQUISA E AO DESENVOLVIMENTO CIENTIFICO E TECNOLÓGICO DO MARANHÃO / This work has the objective to develop an analytical model that makes prediction of the behavior of the algorithm as a function of the design parameters (step adaptation, kernel function and its parameters).We use a non-quadratic function based on kernel, performing a nonlinear transformation of the input space filtering applied on line. Was developed and implemented in the system for adaptive filtering based on Kernel, which provides an analysis of the behavior of KRLS algorithm as well as its properties of convergence. It applies a kernel function in the cost function from the non-recursive quadratic function of an even power, which minimizes the error, defined as the expectation of the cumulative cost of actions taken along a sequence of steps. It appears that this approach allows the determination of the parameters of the problem with greater reliability and robustness and lower cost compared with traditional algorithms (RLS, KRLS, RNQ) . / Este trabalho tem como objetivo desenvolver um modelo analítico que faça a previsão do comportamento do algoritmo RLS como uma função dos parâmetros de projeto (passo de adaptação, função kernel e seus parâmetros). Utiliza-se uma função não quadrática baseado em kernel, realizando uma transformação não linear do espaço de entrada aplicada à filtragem. Foi desenvolvido e implementado na redução de ruídos para a filtragem adaptativa baseada em Kernel, que fornece uma análise do comportamento do algoritmo KRLS, bem como de suas propriedades de convergência. Aplica-se uma função kernel na função de custo a partir da função recursiva não quadrática de quarta potência, que minimiza o erro, definido como a expectativa do custo cumulativo de ações tomadas ao longo de uma sequência de passos. Verifica-se que essa abordagem possibilita a determinação dos parâmetros do problema com uma maior confiabilidade e robustez e o menor custo, quando comparado com algoritmos tradicionais (RLS, KRLS, RNQ).

Les lasers à état solide bi-fréquences constituent des sources de choix pour de nombreux domaines (métrologie, photonique micro-onde, Lidar-Radar, horloges atomiques). Cependant, de tels lasers souffrent d'excès de bruit d'intensité difficiles à supprimer avec les méthodes habituelles. Dans ce contexte, nous développons une nouvelle approche baptisée « buffer reservoir » pour la réduction de l'excès de bruit d'intensité des lasers à état solide. Cette méthode repose sur le changement du comportement dynamique du laser par insertion d'un mécanisme d'absorption non-linéaire faiblement efficace dans la cavité. Tout d'abord, nous étudions cette approche dans des lasers solides mono-fréquence en exploitant deux types d'absorption non-linéaire : l'absorption à deux photons (TPA) et l'absorption par génération de seconde harmonique (SHGA). Nous montrons qu'il est possible de réduire de 50 dB le bruit d'intensité à la fréquence des oscillations de relaxation d'un laser Er,Yb:verre sans en dégrader la puissance de sortie ni le bruit de phase. Nous explorons les mécanismes physiques sous-jacents en développant un modèle analytique décrivant le comportement dynamique du laser. L'effet de l'absorbant non-linéaire sur les pics de bruit à haute fréquence à l'intervalle spectrale libre de la cavité est également étudié. Nous démontrons l'intérêt de telles sources lasers auto-régulées en intensité pour la distribution d'oscillateurs locaux sur porteuse optique. Nous mettons ensuite en application l'approche « buffer reservoir » dans des lasers bi fréquences. En développant un modèle analytique prédictif, nous montrons expérimentalement que l'utilisation de TPA engendre, sous certaines conditions, une réduction de 40 dB de l'amplitude des pics de bruit en-phase et en anti-phase. Nous vérifions en outre les propriétés de couplage des modes dans le milieu actif lorsque les pertes non-linéaires sont présentes. Enfin, nous abordons l'utilisation de SHGA comme ''buffer reservoir'' dans les lasers bi-fréquences. Plus particulièrement, nous explorons expérimentalement et théoriquement le comportement du laser lorsque les pertes non-linéaires ne sont introduites que sur un seul mode propre du laser. Dans cette configuration, nous montrons qu'il est possible d'obtenir pour les deux modes à la fois une forte diminution des pics de bruit d'intensité résonants. / Dual-frequency solid-state lasers are attractive for numerous domains (metrology, microwave photonics, Lidar-Radar, optical clocks). However, such lasers suffer from excess intensity noise which is difficult to cancel with usual methods. In this context, we develop a new approach called “buffer reservoir” for reducing the excess intensity noise. This method relies on the change of the laser’s dynamical behavior by inserting a low efficient nonlinear absorption mechanism in the cavity. First, this approach is studied on single frequency solid-state lasers by using two types of non-linear absorption: two-photon absorption (TPA) and second harmonic generation absorption (SHGA). We show a possible reduction of the intensity noise at the relaxation oscillations frequency of an Er,Yb:glass laser up to 50 dB without degrading neither its power nor its phase noise. We explore the underlying physics by developing an analytical model describing the laser dynamical behavior. The effect of the nonlinear absorber on the noise peaks lying at high frequency at the free spectral range of the cavity is also studied. We demonstrate the relevance of such self-regulated lasers for the distribution of optically carried local oscillators. We then extend the “buffer reservoir” approach to dual-frequency lasers. By developing a predictive analytical model, we show experimentally that the use of TPA enables 40 dB reduction of both in-phase and anti-phase noise under certain conditions. The mode coupling in the active medium is analyzed when the nonlinear losses are present. Finally, we address the use of SHGA as a ''buffer reservoir'' in dual-frequency lasers. In particular, we experimentally and theoretically explore the laser behavior when the nonlinear losses are inserted on one eigen-mode of the laser only. This configuration enables a strong reduction of resonant noise peaks for both modes.

We address the problem of image denoising for additive white Gaussian noise (AWGN), Poisson noise, and Chi-squared noise scenarios. Thermal noise in electronic circuitry in camera hardware can be modeled as AWGN. Poisson noise is used to model the randomness associated with photon counting during image acquisition. Chi-squared noise statistics are appropriate in imaging modalities such as Magnetic Resonance Imaging (MRI). AWGN is additive, while Poisson noise is neither additive nor multiplicative. Although Chi-squared noise is derived from AWGN statistics, it is non-additive. Mean-square error (MSE) is the most widely used metric to quantify denoising performance. In parametric denoising approaches, the optimal parameters of the denoising function are chosen by employing a minimum mean-square-error (MMSE) criterion. However, the dependence of MSE on the noise-free signal makes MSE computation infeasible in practical scenarios. We circumvent the problem by adopting an MSE estimation approach. The ground-truth-independent estimates of MSE are Stein’s unbiased risk estimate (SURE), Poisson unbiased risk estimate (PURE) and Chi-square unbiased risk estimate (CURE) for AWGN, Poison and Chi-square noise models, respectively. The denoising function is optimized to achieve maximum noise suppression by minimizing the MSE estimates. We have chosen the bilateral filter as the denoising function. Bilateral filter is a nonlinear edge-preserving smoother. The performance of the bilateral filter is governed by the choice of its parameters, which can be optimized to minimize the MSE or its estimate. However, in practical scenarios, MSE cannot be computed due to inaccessibility of the noise-free image. We derive SURE, PURE, and CURE in the context of bilateral filtering and compute the parameters of the bilateral filter that yield the minimum cost (SURE/PURE/CURE). On processing the noisy input with bilateral filter whose optimal parameters are chosen by minimizing MSE estimates (SURE/PURE/CURE), we obtain the estimate closest to the ground truth. We denote the bilateral filter with optimal parameters as SURE-optimal bilateral filter (SOBF), PURE-optimal bilateral filter (POBF) and CURE-optimal bilateral filter (COBF) for AWGN, Poisson and Chi-Squared noise scenarios, respectively. In addition to the globally optimal bilateral filters (SOBF and POBF), we propose spatially adaptive bilateral filter variants, namely, SURE-optimal patch-based bilateral filter (SPBF) and PURE-optimal patch-based bilateral filter (PPBF). SPBF and PPBF yield significant improvements in performance and preserve edges better when compared with their globally-optimal counterparts, SOBF and POBF, respectively. We also propose the SURE-optimal multiresolution bilateral filter (SMBF) where we couple SOBF with wavelet thresholding. For Poisson noise suppression, we propose PURE-optimal multiresolution bilateral filter (PMBF), which is the Poisson counterpart of SMBF. We com-pare the performance of SMBF and PMBF with the state-of-the-art denoising algorithms for AWGN and Poisson noise, respectively. The proposed multiresolution-based bilateral filtering techniques yield denoising performance that is competent with that of the state-of-the-art techniques.