Tracheal respiratory sounds analysis has been investigated as a non-invasive method to estimate respiratory flow and upper airway obstruction. However, the flow-sound relationship is highly variable among subjects which makes it challenging to estimate flow in general applications. Therefore, a robust model for acoustical flow estimation in a large group of individuals did not exist before. On the other hand, a major application of acoustical flow estimation is to detect flow limitations in patients with obstructive sleep apnea (OSA) during sleep. However, previously the flow--sound relationship was only investigated during wakefulness among healthy individuals. Therefore, it was necessary to examine the flow-sound relationship during sleep in OSA patients. This thesis takes the above challenges and offers innovative solutions. First, a modified linear flow-sound model was proposed to estimate respiratory flow from tracheal sounds. To remove the individual based calibration process, the statistical correlation between the model parameters and anthropometric features of 93 healthy volunteers was investigated. The results show that gender, height and smoking are the most significant factors that affect the model parameters. Hence, a general acoustical flow estimation model was proposed for people with similar height and gender. Second, flow-sound relationship during sleep and wakefulness was studied among 13 OSA patients. The results show that during sleep and wakefulness, flow-sound relationship follows a power law, but with different parameters. Therefore, for acoustical flow estimation during sleep, the model parameters should be extracted from sleep data to have small errors. The results confirm reliability of the acoustical flow estimation for investigating flow variations during both sleep and wakefulness. Finally, a new method for sleep apnea detection and monitoring was developed, which only requires recording the tracheal sounds and the blood's oxygen saturation level (SaO2) data. It automatically classifies the sound segments into breath, snore and noise. A weighted average of features extracted from sound segments and SaO2 signal was used to detect apnea and hypopnea events. The performance of the proposed approach was evaluated on the data of 66 patients. The results show high correlation (0.96,p < 0.0001) between the outcomes of our system and those of the polysomnography. Also, sensitivity and specificity of the proposed method in differentiating simple snorers from OSA patients were found to be more than 91%. These results are superior or comparable with the existing commercialized sleep apnea portable monitors.

Tracheal respiratory sounds analysis has been investigated as a non-invasive method to estimate respiratory flow and upper airway obstruction. However, the flow-sound relationship is highly variable among subjects which makes it challenging to estimate flow in general applications. Therefore, a robust model for acoustical flow estimation in a large group of individuals did not exist before. On the other hand, a major application of acoustical flow estimation is to detect flow limitations in patients with obstructive sleep apnea (OSA) during sleep. However, previously the flow--sound relationship was only investigated during wakefulness among healthy individuals. Therefore, it was necessary to examine the flow-sound relationship during sleep in OSA patients. This thesis takes the above challenges and offers innovative solutions. First, a modified linear flow-sound model was proposed to estimate respiratory flow from tracheal sounds. To remove the individual based calibration process, the statistical correlation between the model parameters and anthropometric features of 93 healthy volunteers was investigated. The results show that gender, height and smoking are the most significant factors that affect the model parameters. Hence, a general acoustical flow estimation model was proposed for people with similar height and gender. Second, flow-sound relationship during sleep and wakefulness was studied among 13 OSA patients. The results show that during sleep and wakefulness, flow-sound relationship follows a power law, but with different parameters. Therefore, for acoustical flow estimation during sleep, the model parameters should be extracted from sleep data to have small errors. The results confirm reliability of the acoustical flow estimation for investigating flow variations during both sleep and wakefulness. Finally, a new method for sleep apnea detection and monitoring was developed, which only requires recording the tracheal sounds and the blood's oxygen saturation level (SaO2) data. It automatically classifies the sound segments into breath, snore and noise. A weighted average of features extracted from sound segments and SaO2 signal was used to detect apnea and hypopnea events. The performance of the proposed approach was evaluated on the data of 66 patients. The results show high correlation (0.96,p < 0.0001) between the outcomes of our system and those of the polysomnography. Also, sensitivity and specificity of the proposed method in differentiating simple snorers from OSA patients were found to be more than 91%. These results are superior or comparable with the existing commercialized sleep apnea portable monitors.

Nearfield Acoustical Holography (NAH) is an acoustic field visualization technique that can be used to reconstruct three-dimensional (3-D) acoustic fields by projecting two-dimensional (2-D) data measured on a hologram surface. However, linear NAH algorithms developed and improved by many researchers can result in significant reconstruction errors when they are applied to reconstruct 3-D acoustic fields that are radiated from a high-level noise source and include significant nonlinear components. Here, planar, nonlinear acoustical holography procedures are developed that can be used to reconstruct 3-D, nonlinear acoustic fields radiated from a high-level noise source based on 2-D acoustic pressure data measured on a hologram surface. The first nonlinear acoustic holography procedure is derived for reconstructing steady-state acoustic pressure fields by applying perturbation and renormalization methods to nonlinear, dissipative, pressure-based Westervelt Wave Equation (WWE). The nonlinear acoustic pressure fields radiated from a high-level pulsating sphere and an infinite-size, vibrating panel are used to validate this procedure. Although the WWE-based algorithm is successfully validated by those two numerical simulations, it still has several limitations: (1) Only the fundamental frequency and its second harmonic nonlinear components can be reconstructed; (2) the application of this algorithm is limited to mono-frequency source cases; (3) the effects of bent wave rays caused by transverse particle velocities are not included; (4) only acoustic pressure fields can be reconstructed. In order to address the limitations of the steady-state, WWE-based procedure, a transient, planar, nonlinear acoustic holography algorithm is developed that can be used to reconstruct 3-D nonlinear acoustic pressure and particle velocity fields. This procedure is based on Kuznetsov Wave Equation (KWE) that is directly solved by using temporal and spatial Fourier Transforms. When compared to the WWE-based procedure, the KWE-based procedure can be applied to multi-frequency source cases where each frequency component can contain both linear and nonlinear components. The effects of nonlinear bent wave rays can be also considered by using this algorithm. The KWE-based procedure is validated by conducting an experiment with a compression driver and four numerical simulations. The numerical and experimental results show that holographically-projected acoustic fields match well with directly-calculated and directly-measured fields.

The objective of this research is to presents new acoustic echo cancellation design methods that can effectively work in the nonlinear environment. Acoustic echo is an annoying issue for voice communication systems. Because of room acoustics and delay in the transmission path, echoes affect the sound quality and may hamper communications. Acoustic echo cancellers (AECs) are employed to remove the acoustic echo while keeping full-duplex communications. AEC designs face a variety of challenges, including long room impulse response, acoustic path nonlinearity, ambient noise, and double-talk situation. We investigate two parts of echo canceller design: echo cancellation algorithm design and control logic algorithm design. In the first part, our work focuses on the nonlinear adaptive and fast-convergence algorithms. We investigate three different structures: predistortion linearization, cascade structure, and nonlinear residual echo suppressor. Specifically, we are interested in the coherence function, since it provides a means for quantifying linear association between two stationary random processes. By using the coherence as a criterion to design the nonlinear echo canceller in the system, our method guarantees the algorithm stability and leads to a faster convergence rate. In the second part, our work focuses on the robustness of AECs in the presence of interference. With regard to the near-end speech, we investigate the double-talk detector (DTD) design in conjunction with nonlinear AECs. Specifically, we propose to design a DTD based on the mutual information (MI). We show that the advantage of the MI-based method, when compared with the existing methods, is that it is applicable to both the linear and nonlinear scenarios. With respect to the background noise, we propose a variable step-size and variable tap-length least mean square (LMS) algorithm. Based on the fact that the room impulse response usually exhibits an exponential decay power profile in acoustic echo cancellation applications, the proposed method finds optimal step size and tap length at each iteration. Thus, it achieves faster convergence rate and better steady-state performance. We show a number of experimental results to illustrate the performance of the proposed algorithms.

Multisymplectic integration is a relatively new addition to the field of geometric integration, which is a modern approach to the numerical integration of systems of differential equations. Multisymplectic integration is carried out by numerical integrators known as multisymplectic integrators, which preserve a discrete analogue of a multisymplectic conservation law. In recent years, it has been shown that various discretisations of a multi-Hamiltonian PDE satisfy a discrete analogue of a multisymplectic conservation law. In particular, discretisation in time and space by the popular symplectic Runge–Kutta methods has been shown to be multisymplectic. However, a multisymplectic integrator not only needs to satisfy a discrete multisymplectic conservation law, but it must also form a well-defined numerical method. One of the main questions considered in this thesis is that of when a multi-Hamiltonian PDE discretised by Runge–Kutta or partitioned Runge–Kutta methods gives rise to a well-defined multisymplectic integrator. In particular, multisymplectic integrators that are explicit are sought, since an integrator that is explicit will, in general, be well defined. The first class of discretisation methods that I consider are the popular symplectic Runge–Kutta methods. These have previously been shown to satisfy a discrete analogue of the multisymplectic conservation law. However, these previous studies typically fail to consider whether or not the system of equations resulting from such a discretisation is well defined. By considering the semi-discretisation and the full discretisation of a multi-Hamiltonian PDE by such methods, I show the following: • For Runge–Kutta (and for partitioned Runge–Kutta methods), the active variables in the spatial discretisation are the stage variables of the method, not the node variables (as is typical in the time integration of ODEs). • The equations resulting from a semi-discretisation with periodic boundary conditions are only well defined when both the number of stages in the Runge–Kutta method and the number of cells in the spatial discretisation are odd. For other types of boundary conditions, these equations are not well defined in general. • For a full discretisation, the numerical method appears to be well defined at first, but for some boundary conditions, the numerical method fails to accurately represent the PDE, while for other boundary conditions, the numerical method is highly implicit, ill-conditioned and impractical for all but the simplest of applications. An exception to this is the Preissman box scheme, whose simplicity avoids the difficulties of higher order methods. • For a multisymplectic integrator, boundary conditions are treated differently in time and in space. This breaks the symmetry between time and space that is inherent in multisymplectic geometry. The second class of discretisation methods that I consider are partitioned Runge– Kutta methods. Discretisation of a multi-Hamiltonian PDE by such methods has lead to the following two major results: 1. There is a simple set of conditions on the coefficients of a general partitioned Runge– Kutta method (which includes Runge–Kutta methods) such that a general multi- Hamiltonian PDE, discretised (either fully or partially) by such methods, satisfies a natural discrete analogue of the multisymplectic conservation law associated with that multi-Hamiltonian PDE. 2. I have defined a class of multi-Hamiltonian PDEs that, when discretised in space by a member of the Lobatto IIIA–IIIB class of partitioned Runge–Kutta methods, give rise to a system of explicit ODEs in time by means of a construction algorithm. These ODEs are well defined (since they are explicit), local, high order, multisymplectic and handle boundary conditions in a simple manner without the need for any extra requirements. Furthermore, by analysing the dispersion relation for these explicit ODEs, it is found that such spatial discretisations are stable. From these explicit ODEs in time, well-defined multisymplectic integrators can be constructed by applying an explicit discretisation in time that satisfies a fully discrete analogue of the semi-discrete multisymplectic conservation law satisfied by the ODEs. Three examples of explicit multisymplectic integrators are given for the nonlinear Schr¨odinger equation, whereby the explicit ODEs in time are discretised by the 2-stage Lobatto IIIA– IIIB, linear–nonlinear splitting and real–imaginary–nonlinear splitting methods. These are all shown to satisfy discrete analogues of the multisymplectic conservation law, however, only the discrete multisymplectic conservation laws satisfied by the first and third multisymplectic integrators are local. Since it is the stage variables that are active in a Runge–Kutta or partitioned Runge– Kutta discretisation in space of a multi-Hamiltonian PDE, the order of such a spatial discretisation is limited by the order of the stage variables. Moreover, the spatial discretisation contains an approximation of the spatial derivatives, and thus, the order of the spatial discretisation may be further limited by the order of this approximation. For the explicit ODEs resulting from an r-stage Lobatto IIIA–IIIB discretisation in space of an appropriate multi-Hamiltonian PDE, the order of this spatial discretisation is r - 1 for r = 10; this is conjectured to hold for higher values of r. For r = 3, I show that a modification to the initial conditions improves the order of this spatial discretisation. It is expected that a similar modification to the initial conditions will improve the order of such spatial discretisations for higher values of r.

Ce travail concerne l’étude acoustique théorique et expérimentale des matériaux poreux à squelette métallique, macroscopiquement homogènes et inhomogènes ainsi que l’étude de leurs propriétés mécaniques de comportement au choc pour comparaison. Le modèle acoustique de Johnson -Champoux - Allard s’est montré adapté pour la modélisation acoustique. Ce modèle associé à une approche proposée récemment et utilisant le concept de matrices de transfert en parallèle a permis, dans une nouvelle approche basée sur les “mélanges de matériaux”, d’étudier les matériaux poreux macroscopiquement inhomogènes. Par ailleurs, une étude paramétrique du coefficient d’absorption en fonction de la porosité et de la fréquence a été proposée. Les maxima d’absorption ainsi que l’enveloppe des courbes d’absorption en fonction de la porosité ont été étudiés. En premier lieu, un matériau théorique à propriétés indépendantes a été étudié. Les matériaux réels à propriétés interdépendantes ont ensuite été abordés à l’aide d’un modèle reliant leurs propriétés à la porosité. Enfin, une comparaison entre les propriétés acoustiques et les propriétés mécaniques de comportement à l’impact a été initiée en vue de déterminer un critère objectif permettant de proposer un compromis entre les deux domaines. / This work is concerned with the theoretical and experimental study of the acoustical properties of macroscopically homogenous and inhomogeneous porous media as well as their mechanical response to impacts. The model of Johnson - Champoux - Allard appeared adapted for the acoustical modeling. This model, associated with a recently developed approach involving the concept of parallel transfer matrices has lead to a new approach of macroscopically inhomogeneous porous materials based on “mixtures of materials”. Furthermore, a parametric study of the absorption coefficient as a function of porosity and frequency has been proposed. The maximums of absorption as well as the envelop of the absorption curves have been studied as functions of porosity. First, a theoretical material with independent parameters has been studied. Real materials with nonindependent parameters were then investigated with the help of a model relating their properties to the porosity. Finally, a comparison between the acoustical and mechanical properties has been initiated in view of determining an objective criterion that will allow to propose a trade off between the two fields.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este estudo teve como objetivo principal caracterizar os padrões de distribuição do material particulado em suspensão ao longo da baía de Sepetiba, associando as variabilidades espaciais e temporais com ciclos de maré. Além disso, o estudo também avalia a utilização de equipamentos acústicos como ferramentas à estimativa das concentrações de material particulado em suspensão. A aquisição de dados foi realizada num total de sete campanhas realizadas entre novembro de 2010 e dezembro de 2011. Sete estações foram posicionadas nas proximidades do canal principal de acesso à baía, ao longo de um transecto que se estende do seu interior até sua desembocadura. As sete campanhas amostrais se distribuem em duas séries longas, de 13 e 25 horas, de aquisição em um ponto fixo, e cinco amostragens ao longo das estações. A aquisição de dados envolve: coleta de amostras de água, utilizadas nas estimativas das concentrações de material particulado; coleta de sedimentos de fundo para caracterização granulométrica das estações amostradas; perfis de parâmetros físico-químicos; dados de correntômetria adquiridos junto ao fundo. O processamento das amostras de água e sedimentos foi realizado no laboratório de Geologia Marinha da Faculdade de Oceanografia da Universidade do Estado do Rio de Janeiro. As concentrações de material particulado em suspensão foram utilizadas na calibração de sensores acústicos e óticos, permitindo uma avaliação espaço-temporal mais detalhada dos padrões de distribuição junto ao fundo e ao longo da coluna dágua. Os dados observados permitiram identificar que as maiores concentrações de material particulado em suspensão ocorrem em condições de maré enchente, e estão associadas à assimetria de maré. A baía pode ser dividida em dois setores: um na porção mais interna, onde se observou maior influência do aporte fluvial, onde as concentrações de material particulado em suspensão respondem à propagação da pluma do canal de São Francisco; e outro que se estende da porção central até sua desembocadura, onde predomina o domínio marinho, com influência de eventos oriundos da plataforma continental. Também pode ser identificada a influência do fenômeno La Niña, que provavelmente foi responsável por: altas salinidades encontradas no interior da baía e ocorrência da Água Central do Atlântico Sul à baixas profundidades. Quanto à utilização de equipamentos acústicos nas estimativas das concentrações de material particulado, os dados se demonstraram ricos em detalhes, que permitiram avaliar o comportamento do material particulado junto ao fundo frente a diferentes condições de maré, turbulência e incidência de oscilações. / This study aimed to characterize the distribution patterns of suspended particulate matter along the Sepetiba Bay, linking spatial and temporal variability with tidal cycles. Furthermore, the study also evaluates the applicability of acoustic devices as tools for estimation of concentrations of suspended particulate matter. Data acquisition was performed in a total of seven campaigns carried out between November 2010 and December 2011. Seven stations were located near the main channel access to the bay along a transect that extends from its interior to its mouth. The seven sampling campaigns are distributed in two long series of 13 and 25 hours of acquisitions at a fixed station, and five campaigns along the transect. Data acquisition involves: collecting water samples to estimate the concentrations of particulate matter, bottom sediments collected to characterize particle size of the stations sampled; profiles of physicochemical parameters; current data obtained at the bottom. The processing of water samples and sediments was conducted in the Oceanografic Geology Laboratory Laboratório de Oceanografia Geológica of the Faculdade de Oceanografia - Universidade do Estado do Rio de Janeiro. The concentrations of suspended particulate matter were used for the calibration of acoustic and optical sensors, allowing an evaluation of more detailed spatial and temporal patterns of distribution along the bottom and along the water column. The analysis allowed to identify that the highest concentrations of suspended particulate matter occur in conditions of high tide, and are associated with tidal asymmetry (highest current velocities). The bay can be divided into two sectors: one in the northern area, where riverine characteristics are more pronounced, and concentrations of suspended particles respond to the spread of the plume of São Francisco channel, and another that extends from the central portion to its mouth, where dominate the marine domain, influenced by events from the continental shelf. It can also be identified the influence of La Niña, which was probably responsible for: high salinities found inside the bay and occurrence of South Atlantic Central Water at lower depths. Regarding the use of acoustic equipment in the estimation of concentrations of particulate matter, the results were rich in detail, which allowed us to evaluate the behavior of particulate material near the bottom for different tidal conditions, turbulence and incidence of oscillations.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este estudo teve como objetivo principal caracterizar os padrões de distribuição do material particulado em suspensão ao longo da baía de Sepetiba, associando as variabilidades espaciais e temporais com ciclos de maré. Além disso, o estudo também avalia a utilização de equipamentos acústicos como ferramentas à estimativa das concentrações de material particulado em suspensão. A aquisição de dados foi realizada num total de sete campanhas realizadas entre novembro de 2010 e dezembro de 2011. Sete estações foram posicionadas nas proximidades do canal principal de acesso à baía, ao longo de um transecto que se estende do seu interior até sua desembocadura. As sete campanhas amostrais se distribuem em duas séries longas, de 13 e 25 horas, de aquisição em um ponto fixo, e cinco amostragens ao longo das estações. A aquisição de dados envolve: coleta de amostras de água, utilizadas nas estimativas das concentrações de material particulado; coleta de sedimentos de fundo para caracterização granulométrica das estações amostradas; perfis de parâmetros físico-químicos; dados de correntômetria adquiridos junto ao fundo. O processamento das amostras de água e sedimentos foi realizado no laboratório de Geologia Marinha da Faculdade de Oceanografia da Universidade do Estado do Rio de Janeiro. As concentrações de material particulado em suspensão foram utilizadas na calibração de sensores acústicos e óticos, permitindo uma avaliação espaço-temporal mais detalhada dos padrões de distribuição junto ao fundo e ao longo da coluna dágua. Os dados observados permitiram identificar que as maiores concentrações de material particulado em suspensão ocorrem em condições de maré enchente, e estão associadas à assimetria de maré. A baía pode ser dividida em dois setores: um na porção mais interna, onde se observou maior influência do aporte fluvial, onde as concentrações de material particulado em suspensão respondem à propagação da pluma do canal de São Francisco; e outro que se estende da porção central até sua desembocadura, onde predomina o domínio marinho, com influência de eventos oriundos da plataforma continental. Também pode ser identificada a influência do fenômeno La Niña, que provavelmente foi responsável por: altas salinidades encontradas no interior da baía e ocorrência da Água Central do Atlântico Sul à baixas profundidades. Quanto à utilização de equipamentos acústicos nas estimativas das concentrações de material particulado, os dados se demonstraram ricos em detalhes, que permitiram avaliar o comportamento do material particulado junto ao fundo frente a diferentes condições de maré, turbulência e incidência de oscilações. / This study aimed to characterize the distribution patterns of suspended particulate matter along the Sepetiba Bay, linking spatial and temporal variability with tidal cycles. Furthermore, the study also evaluates the applicability of acoustic devices as tools for estimation of concentrations of suspended particulate matter. Data acquisition was performed in a total of seven campaigns carried out between November 2010 and December 2011. Seven stations were located near the main channel access to the bay along a transect that extends from its interior to its mouth. The seven sampling campaigns are distributed in two long series of 13 and 25 hours of acquisitions at a fixed station, and five campaigns along the transect. Data acquisition involves: collecting water samples to estimate the concentrations of particulate matter, bottom sediments collected to characterize particle size of the stations sampled; profiles of physicochemical parameters; current data obtained at the bottom. The processing of water samples and sediments was conducted in the Oceanografic Geology Laboratory Laboratório de Oceanografia Geológica of the Faculdade de Oceanografia - Universidade do Estado do Rio de Janeiro. The concentrations of suspended particulate matter were used for the calibration of acoustic and optical sensors, allowing an evaluation of more detailed spatial and temporal patterns of distribution along the bottom and along the water column. The analysis allowed to identify that the highest concentrations of suspended particulate matter occur in conditions of high tide, and are associated with tidal asymmetry (highest current velocities). The bay can be divided into two sectors: one in the northern area, where riverine characteristics are more pronounced, and concentrations of suspended particles respond to the spread of the plume of São Francisco channel, and another that extends from the central portion to its mouth, where dominate the marine domain, influenced by events from the continental shelf. It can also be identified the influence of La Niña, which was probably responsible for: high salinities found inside the bay and occurrence of South Atlantic Central Water at lower depths. Regarding the use of acoustic equipment in the estimation of concentrations of particulate matter, the results were rich in detail, which allowed us to evaluate the behavior of particulate material near the bottom for different tidal conditions, turbulence and incidence of oscillations.

\"Ver o corpo humano por dentro\" sem a necessidade de intervenção cirurgica é objetivo que motivou a criação de diversos instrumentos como eletrocardiogramas, eletroencefalogramas, equipamentos de ressonância magnética e raio-X. Através daavaliação de imagens ou resultados numéricos, pode-se detectar patologias nos primeiros estágios, permitindo uma ação decisiva de especialistas médicos na cura destas. Especialistas da fala normalmente empregam instrumentos comovideolaringoscopia e videoestroboscopia para avaliar qualitativamente o comportamento da laringe e pregas vocais. Comprendendo que a voz transmite informações sobre alterações orgânicas ou funcionais nas estruturas de vocalização, este trabalhoapresenta um conjunto de medidas acústicas neste sinal que evidenciam alterações na periodicidade do movimento das cordas vocais e quantidade de ruído turbulento que atravessa a glote. A partir de avaliação estatística da capacidadedescriminatória destes índices acústicos e empregando-se redes neurais artificiais, define-se um método automático para identificação probabilística das patologias que afetam as estruturas da laringe. / \"To see the inside of the human body\" without the necessity of surgical intervention is the objective that motivates the conception of several instruments like electrocardiogram, electroencephalongram, magnetic resonance and X-ray equipments. Through the image analysis or numerical results, it is possible to identify pathologies, allowing a decisive action of physician specialists in cure of these. Voice specialists, normally, use instruments as videolaryngoscopy and videostroboscopy to assess the vocal folds and larynx comportment, qualitatively. Understanding that the voice transmits information upon functional or organic alterations in vocalization structures, this work presents a set of acoustic measurements, based on this signal, that evidences alterations on vocal folds movement periodicity and quantify of turbulent noise throught the glottis. From the statistic evaluation of discriminatory capacity of these acoustic indexes and using artificial neural networks, it defines an automatic method for the probabilistic identification of pathologies that affect the laryngeal structures.

Afin de réduire les bruits rayonnés en sortie de guide d’onde, des traitements acoustiques localement réactifs, comme les structures « Plaque perforée/Nid d’abeilles », peuvent être appliqués en liner. La conception de ces liners devient alors un challenge important avec l’apparition de nouvelles normes sur le bruit et impose de posséder une très bonne connaissance du comportement de ces traitements, en particulier leur impédance de surface. Néanmoins, la caractérisation de cette impédance n’est pas une chose facile et est généralement réalisée via des modèles semi-empiriques comme ceux de Guess, Elnady, Allam ou expérimentalement par des méthodes de mesures directes ou inverses. Ces approches inverses permettent, par la confrontation d’une modélisation du problème avec des observations expérimentales, de retourner, au travers d’une fonction coût, l’impédance du traitement. Ces méthodes ont l’avantage de réaliser une observation dans les conditions réelles d’utilisation du traitement. En effet, de nombreux paramètres influencent l’impédance de surface comme la présence d’un écoulement, l’incidence de l’onde… Dans cette thèse, une méthode d’identification de l’impédance est proposée. A partir de l’impédance de surface d’un traitement « Plaque perforée/Nid d’abeille » prédite par un modèle empirique via ses paramètres géométriques (épaisseur de la plaque, diamètre des perforations…), une méthode basée sur l’approche Bayésienne est implémentée afin de remonter à l’impédance réelle du traitement. Le problème étudié consiste en la propagation d’une onde dans un tronçon rectangulaire traité sur sa face supérieure et la mesure des pressions acoustiques est réalisée sur le banc d’essai de l’Université Technologique de Compiègne avec un écoulement rasant. Un modèle de propagation d’ondes dans le conduit est développé via la technique du raccordement modal, afin de prédire la pression aux positions des microphones pour n’importe quelle valeur d’impédance. A partir de la mesure et de la simulation, la règle de Bayes peut être appliquée afin de construire la densité de probabilité a posteriori. Cette densité de probabilité est alors échantillonnée au travers d’un algorithme Évolutionnaire de Monte Carlo par Chaîne de Markov (EMCMC). L’intérêt principale de cette méthode, est d’obtenir de nombreuses d’informations statistiques sur les paramètres caractérisant l’impédance de surface comme leur distribution et leur corrélation. / Locally reactive acoustic liners such as honeycomb structures with perforated panels can be modeled with a surface impedance in standard numerical models. However, the characterization of this impedance is not always straightforward. Empirical models or standing wave tube measurements are generally used to get the behavior of these acoustic treatments. Unfortunately, these methods provide only an evaluation of the impedance under specific conditions. Moreover, the conditions of use can change significantly the acoustic liners behavior as grazing flow conditions or oblique incident waves. A characterization of locally reactive acoustic liners is presented here. Starting from a set of parameters and represents a surface impedance using empirical model, an inverse method based on Bayesian approach is used to return the surface impedance taking in consideration the real conditions of use. A rectangular duct treated by a liner on its upper face is considered and these conditions are similar to the experiment present at the Université de Technologie de Compiègne. This inverse method requires a direct model to predict the pressure at some microphone positions with any surface impedance. The model used in the following is based on the Mode-Matching method. From the direct analytical model, the Bayes'rule is then used to get the posterior probability density function of the estimated impedance. An Evolutionary Monte Carlo by Markov chain (EMCMC) method is used to sample this posterior probability density. This method provides not only the best set of parameters but also some statistical information for each parameter.