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.

The smart phone has become the major device for taking photos and filming. There are 800 hours of videos uploaded to YouTube every minute, and more YouTubers participating in generating videos. Because it is an era of we-media, there will be more and more people using video to promote himself. Nowadays, people can shoot 4k video by smartphones, but there’s no solution for people who want to shoot videos with good audio quality, without worrying about the issue of noise, time consuming, post-editing, expensive tools and long distance filming. This new product called WiMic, a wireless noise-reduction recorder for video-shooting on smartphones. The target audience will be YouTubers, video makers, travelers, families, bands, sports. Anyone who want to shoot good videos with great and clear audio quality will need wireless recorder like WiMic. In addition, there are some main features, such as noise reduction by ANR and ANC, light weight, long distance of audio recording, three-sound-tracks simultaneous recording and supporting live streaming, which help video-shooting lovers to produce better audio quality videos without noise and share them with friends and audience.

We report a new method for the reduction of noise from spectra. This method is based on casting vectors from one data point to the following data points of the noisy spectrum. The noise‐reduced spectrum is computed from the casted vectors within a margin that is identified by an envelope‐finder algorithm. We compared here the presented method with the Savitzky–Golay and the wavelet transform approaches for noise reduction using simulated Raman spectra of various signal‐to‐noise ratios between 1 and 25 dB and experimentally acquired Raman spectra. The method presented here performs well compared with the Savitzky–Golay and the wavelets‐based denoising method, especially at small signal‐to‐noise ratios and furthermore relies on a minimum of human input requirements.

This thesis deals with design and realization of methods of preprocessing of X-ray images and its storage. In the first part of this thesis, there were designed and implemented methods for preprocessing of series of X-ray images such as averaging after image registration or merging of images to a HDR image using Debevec method. In the following part of the thesis, there was done a literary research of data formats based on which was implemented a library for x-ray images storage. Both implemented methods allow to reduce a random noise by merging a series of images. Application of the Debevec method also allow to increase a dynamic range of image.

This master´s thesis deals with wavelet transformation and its signal and image noise reduction application method. Significant parameters problems as a wavelet type, a threshold technique selection, a threshold level and a level analysis selection for successful signal and noise image filtering are described. A relation between wavelet transformation and digital bank filter is used by anti-noise and sub-bandwidth filtration. A part of the master´s thesis is focused on nuclear magnetic resonation, where jaw-joint image is processed. Jaw joint image noise reduction filtration methods are used in experimental part of the master´s thesis. Consequently, filtration methods improve a jaw joint image quality, which helps a doctor with patient health state condition. Different types of wavelets were tested and in different application methods order. Filtration methods results were visually compared; therefore any conclusion comparison has subjective matter. Accordingly, only doctor is able to resolve which filtration method is convenient to use to determine patient health state.