• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 43
  • 21
  • 6
  • 5
  • Tagged with
  • 84
  • 84
  • 20
  • 20
  • 14
  • 13
  • 13
  • 12
  • 12
  • 10
  • 10
  • 9
  • 9
  • 9
  • 8
  • 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.
71

Approche analytique modale pour la prévision vibratoire de plaques couplées à des sols : Applications ferroviaires / Analytical modeling of ground-slab interaction : Railway application

Grau, Loïc 15 December 2015 (has links)
Ce travail de thèse présente la formalisation du problème de couplage d'une plaque en vibration de flexion avec le sol. La notion d'impédance intermodale de rayonnement vibratoire est définie de façon analogue à son équivalent acoustique. A partir de cette définition, la notion de masse, raideur et amortissement modal ajoutée sur la structure par le sol est introduite. L'effet sur le niveau vibratoire de la structure est présenté, notamment l'effet très amortissant du sol sur la structure. Une comparaison avec le modèle équivalent acoustique est présentée avec une attention particulière portée sur les différences entre les impédances intermodales. L'influence de la stratification sur le niveau vibratoire de la structure fait apparaitre des phénomènes nouveaux sur la partie imaginaire de l'impédance intermodale. Une comparaison théorie-expérience a été effectuée dans le cas d'une dalle de tramway couplée au sol. On présente également une comparaison avec un code numérique, MEFISSTO développé par P. Jean au sein du CSTB. On présente également une extension du modèle d'une plaque couplée au sol au cas de couplage de deux plaques avec le sol. On montre notamment que l'écriture du problème reste très similaire au problème d'une plaque couplée au sol. Les impédances intermodales peuvent encore être définies avec la prise en compte du couplage des modes d'une plaque sur les modes de l'autre plaque. On présentera trois applications de ce modèle. La première concerne l'utilisation d'une Barrière Vibratoire Horizontale à la surface du sol pour atténuer les vibrations issues d'une première plaque modélisant la dalle de tramway. Finalement une ouverture du problème de couplage d'une plaque avec le sol par l'utilisation de ce modèle dans des problématiques inverses est présentée. On montre qu'il est possible par un problème inverse de remonter aux efforts injectés sur une dalle de tramway au passage de celui-ci. / This thesis is concerned with the coupling between a fexural vibrating plate and a stratifed ground. A semi-analytical solution is introduced similar to the equivalent acoustical problem. The ground cross modal impedance is defined in a similar way as the equivalent acoustical impedance. From this definition, the ground added mass, stiffness and damping to the plate are presented. Similarities and discrepancies between the acoustical and the ground cross modal impedance are introduced. Influence of the ground stratification on the plate vibration shows new phenomena especially on the imaginary part of the ground cross modal impedance. A comparison between the model developed in this thesis and an experiment made on a tramway slab has been done as well as a comparison with a numerical model, MEFISSTO developed by P. jean at CSTB. One introduces an extension of the modeling developed and is concerned with modeling two flexural plates to the ground. It can be pointed out that problem formulation is still close to the problem formulation of one plate coupled to the ground. Three different fields of application of such modeling is presented. The first field of application is concerned with ground mitigation due to the passing tramway on. The first plate is the excited plate by the tramway and the second plate, called Horizontal Wave Barrier, is acting at the top surface as a ground attenuator. The second field of application is concerned with the modeling of building foundation. It is shown that the vibration received by the foundation of a building can be an input data for modeling an entire building vibration. The third field of application is concerned with different cases of tramway slab for reduction of ground vibration. Finally one presents an introduction of the use of this ground structure modeling in the case of inverse problem. It is shown that it is possible to identify injected force to the plate by the tramway. Furthermore the ground allows a regularization of the problem in the inversion which is not the case in the acoustical case.
72

Characterisation of air-borne sound sources using surface coupling techniques / Caractérisation de sources de son aérien utilisant des méthodes d'harmoniques de surface

Du, Liangfen 30 March 2016 (has links)
La thèse se base sur la recherche des possibilités de caractérisation du son aérien de sources sonores arbitraires. A cette fin, une approche particulière est étudiée à l’endroit où la caractérisation de la source est faite via une surface d’interface qui enveloppe totalement ou partiellement la source physique. Deux descripteurs qui dépendent de la fréquence sont definis au travers d’une telle surface: la pression sonore bloquée et l’impédance de la source. Le précédent représente la pression sonore créée par le système d’exploitation source qui agit sur la surface enveloppante quand elle est rendue immobile. Cette dernière représente le rapport des amplitudes de réponse de pression et les amplitudes de vitesse d’excitation normales au travers de la surface. La surface enveloppante définit un volume d’air qui contient la source physique appelée l’espace source. Les deux descripteurs définis sur l’espace source, la pression bloquée et l’impédance de la source sont montrés comme étant intrinsèques à la source, c’est-à-dire indépendants de l’espace acoustique environnant. Une fois définis, ces descripteurs permettent de trouver la pression sonore et la vitesse particulaire normale à la surface de l’interface quand l’espace source est couplé à un espace récepteur arbitraire, c’est-à-dire une pièce. Cela permet alors la prédiction du son dans l’espace récepteur. Les conditions de couplage nécessitent que l’espace récepteur soit caractérisé en utilisant la même surface enveloppante telle que l’espace source. En acceptant de garder à l’esprit la simplicité de la mesure, la surface enveloppante a été conçue vu qu’elle comporte une ou plusieurs surfaces rectangulaires planes. Le défi de la recherche était alors d’obtenir une impédance significative de la surface au travers de la surface plane rectangulaire (continue) ainsi que celle de la pression bloquée compatible avec la formulation de l’impédance. Cela a conduit à une décomposition dans l’espace de la pression sonore et de la vitesse des particules au sein du nombre fini des composants, chacun défini par une amplitude complexe et une distribution dans l’espace particulière. De cette façon, la pression bloquée se réduit à un vecteur d’amplitude de pression complexe, tandis que l’impédance devient une matrice de pression et des rapports d’amplitudes complexes de la vitesse de défauts de de décompositions ont été recherchés dans le détail: la méthode harmonique de surface et la méthode du patch. Le premier se rapproche de la pression de surface et de la vitesse normale par des combinaisons de fonctions de surface trigonométriques en 2D tandis que ce dernier partage la surface en petites parcelles et intervient sur chaque parcelle de façon discrète en utilisant les valeurs moyennes du patch. / The thesis investigates possibilities of air-borne sound characterisation of arbitrary sound sources. To this end a particular approach is studied where the source characterisation is done via an interface surface which fully or partially envelopes the physical source. Two frequency dependent descriptors are defined across such a surface: the blocked sound pressure and the source impedance. The former represents the sound pressure created by the operating source which acts on the enveloping surface when this is made immobile. The latter represents the ratio of pressure response amplitudes and normal velocity excitation amplitudes across the surface. The enveloping surface defines an air volume containing the physical source, called the source space. The two source descriptors defined on the source space, the blocked pressure and the source impedance, are shown to be intrinsic to the source, i.e. independent of the surrounding acoustical space. Once defined, these descriptors allow one to find the sound pressure and normal particle velocity at the interface surface when the source space is coupled to an arbitrary receiver space, i.e. a room. This in turn allows for sound prediction in the receiver space. The coupling conditions require that the receiver space is characterised using the same enveloping surface as the source space. Bearing the measurement simplicity in mind, the enveloping surface has been conceived as consisting of one or several rectangular plane surfaces. The research challenge was then to obtain meaningful surface impedance across a (continuous) rectangular plane surface as well as the blocked pressure compatible with impedance formulation. This has led to a spatial decomposition of sound pressure and particle velocity into finite number of components, each defined by a complex amplitude and a particular spatial distribution. In this way the blocked pressure reduces to a vector of complex pressure amplitudes while the impedance becomes a matrix of pressure and velocity complex amplitude ratios. Two decomposition methods have been investigated in detail: the surface harmonic method and the patch method. The former approximates the surface pressure and normal velocity by combinations of 2D trigonometric surface functions while the latter splits the surface into small patches and treats each patch in a discrete way, using patch-averaged values.
73

Investigation of anisotropic properties of musculoskeletal tissues by high frequency ultrasound

Sannachi, Lakshmanan 03 March 2012 (has links)
Knochen und Muskel sind die wichtigsten Gewebe im muskuloskelettalen System welche dem Körper die Bewegungen möglich machen. Beide Gewebetypen sind hochgradig strukturierter Extrazellulärmatrix zugrundegelegt, welche die mechanischen und biologischen Funktionen bestimmen. In dieser Studie wurden die räumliche Verteilung der anisotropen elastischen Eigenschaften und der Gewebemineralisation im humanen kortikalen Femur untersucht mit akustischer Mikroskopie und Synchrotron-µCT. Die homogenisierten elastischen Eigenschaften wurden aus einer Kombination der Porosität und der Gewebeelastizitätsmatrix mit Hilfe eines asymptotischen Homogenisierungsmodells ermittelt. Der Einfluss der Gewebemineralisierung und der Strukturparameter auf die mikroskopischen und mesoskopischen elastischen Koeffizienten wurde unter Berücksichtigung der anatomischen Position des Femurschaftes untersucht. Es wurde ein Modell entwickelt, mit welchem der intramuskuläre Fettgehalt des porcinen musculus longissimus nichtinvasiv mittels quantitativem Ultraschall und dessen spektraler Analyze des Echosignals bestimmt werden kann. Muskelspezifische Parameter wie Dämpfung, spectral slope, midband fit, apparent integrated backscatter und cepstrale Paramter wurden aus den RF-Signalen extrahiert. Die Einflüsse der Muskelkomposition und Strukturparameter auf die spektralen Ultraschallparameter wurden untersucht. Die akustischer Parameter werden durch die Muskelfaserorientierung beeinflusst und weisen höhere Werte parallel zur Faserlängsrichtung als senkrecht zur Faserorientierung auf. Die in dieser Studie gewonnenen detaillierten und lokal bestimmten Knochendaten können möglicherweise als Eingabeparameter für numerische 3D FE-Simulationen. Darüber hinaus kann die Untersuchung von Veränderungen der lokalen Gewebeanisotropie neue Einsichten in Studien über Knochenumbildung geben. Diese auf Gewebeebene bestimmten Daten von Muskelgewebe können in numerischen Simulationen von akustischer Rückstreuung genutzt werden um diagnostische Methoden und Geräte zu verbessern. / Bone and muscle are the most important tissues in the musculoskeletal system that gives the ability to move the body. Both tissues have the highly oriented underlying extracellular matrix structure for performing mechanical and biological functions. In this study, the spatial distribution of anisotropic elastic properties and tissue mineralization within a human femoral cortical bone shaft were investigated using scanning acoustic microscopy and synchrotron radiation µCT. The homogenized meoscopic elastic properties were determined by a combination of porosity and tissue elastic matrix using a asymptotic homogenization model. The impact on tissue mineralization and structural parameters of the microscopic and mesocopic elastic coefficients was analyzed with respect to the anatomical location of the femoral shaft. A model was developed to estimate intramuscular fat of porcine musculus longissimus non-invasively using a quantitative ultrasonic device by spectral analysis of ultrasonic echo signals. Muscle specific acoustic parameters, i.e. attenuation, spectral slope, midband fit, apparent integrated backscatter, and cepstral parameters were extracted from the measured RF echoes. The impact of muscle composition and structural properties on ultrasonic spectral parameters was analyzed. The ultrasound propagating parameters were affected by the muscle fiber orientation. The most dominant direction dependency was found for the attenuation. The detailed locally assessed bone data in this study may serve as a real-life input for numerical 3D FE simulation models. Moreover, the assessment of changes of local tissue anisotropy may provide new insights into the bone remodelling studies. The data provided at tissue level and investigated ultrasound backscattering from muscle tissue, can be used in numerical simulation FE models for acoustical backscattering from muscle for the further improvement of diagnostic methods and equipment.
74

Avaliação comportamental, eletroacústica e eletrofisiológica da audição em pacientes com lesão isquêmica do hemisfério direito / Behavioral, electroacoustic, and electrophysiological hearing assessment in patients with right hemisphere ischemic lesion

Magliaro, Fernanda Cristina Leite 18 August 2009 (has links)
INTRODUÇÃO: O Acidente Vascular Cerebral Isquêmico (AVCI) é o evento mais freqüente dentre os AVCs, sendo caracterizado pela interrupção da irrigação sanguínea ao cérebro, a qual pode acarretar em lesão celular e alterações nas funções neurológicas. As manifestações clínicas desta doença podem incluir alterações das funções motoras, sensitivas, cognitivas, perceptivas, da linguagem entre outras. Sendo assim, é extremamente importante que sejam identificadas possíveis alterações nas vias auditivas, periférica e central, as quais podem prejudicar a qualidade de vida destes indivíduos. OBJETIVO: caracterizar os achados das avaliações comportamentais, eletroacústicas e eletrofisiológicas da audição em indivíduos destros com lesão isquêmica do hemisfério cerebral direito, bem como compará-los aos obtidos em indivíduos normais da mesma faixa etária. MÉTODOS: foram realizadas audiometria tonal, logoaudiometria, medidas de imitância acústica, potencial evocado auditivo de tronco encefálico (PEATE), potencial evocado auditivo de média latência (PEAML) e potencial cognitivo (P300) em 17 indivíduos com lesão do hemisfério direito (grupo pesquisa) e 25 normais (grupo controle), com idades entre 20 e 70 anos. RESULTADOS: Na análise dos dados qualitativos não foram encontradas alterações na avaliação comportamental da audição para os dois grupos. Ambos os grupos apresentaram alterações nos resultados do PEATE e do PEAML, sendo que houve diferença estatisticamente significante entre os grupos, para esses dois potenciais, nas quais o grupo pesquisa apresentou maior ocorrência de alterações. No PEATE a alteração mais freqüente foi do tipo tronco encefálico baixo, sendo que, entre os grupos, houve diferença estatisticamente significante, na qual o grupo pesquisa mostrou maior ocorrência dessa alteração. No PEAML a alteração predominante foi do tipo ambas (efeito orelha e efeito eletrodo ocorrendo concomitantemente) para o grupo pesquisa, e do tipo efeito eletrodo para o grupo controle. Na análise dos dados quantitativos (realizada apenas para os potenciais evocados auditivos) verificou-se, no PEATE, que ocorreu diferença estatisticamente significante entre os grupos com relação às latências das ondas III e V e interpicos I-III e I-V. Para o PEAML, a diferença estatisticamente significante entre os grupos ocorreu apenas para a latência da onda Na na posição C3/A1. Para o P300, ocorreu diferença entre os grupos com relação à latência da onda P300, sendo que o grupo pesquisa apresentou tempo médio de latência maior; além disso, houve uma tendência estatisticamente significante entre as orelhas direita e esquerda dentro do grupo pesquisa, mostrando aumento de latência da onda P300 na orelha direita. CONCLUSÃO: Indivíduos destros com lesão de hemisfério direito apresentaram limiares auditivos dentro da normalidade na avaliação comportamental da audição, entretanto, apresentaram resultados indicativos de déficit no sistema nervoso auditivo central, nas avaliações eletrofisiológicas da audição. Foram observados comprometimentos em tronco encefálico baixo, bem como nas regiões subcorticais e corticais. Dificuldades auditivas não foram percebidas pelos indivíduos, sugerindo que, provavelmente tal sinal possa estar relacionado à uma heminegligência auditiva. Tornam-se necessários mais estudos que avaliem a via auditiva central destes indivíduos para uma melhor caracterização dos achados eletrofisiológicos / INTRODUCTION: The ischemic cerebral stroke (ICS) is the most frequent event among cerebral strokes. It is characterized by the interruption of blood supply to the brain, which can lead to cell damage and alterations in neurological functions. The clinical manifestations of this disease may include alterations in motor, sensory, cognitive, perceptual and language functions among others. Therefore, the identification of possible alterations in both peripheral and central auditory pathways that may impair the quality of life of these individuals is extremely important. OBJECTIVE: To characterize the findings of behavioral, electrophysiological and electroacoustic hearing evaluations in right-handed individuals with right hemisphere ischemic lesion, and to compare such data to those obtained in normal individuals with the same age. METHODS: Pure tone audiometry, speech audiometry, acoustic immittance measures, brainstem auditory evoked potential (BAEP), Auditory Middle-Latency Response (AMLR) and cognitive potential (P300) were carried out in 17 subjects with right hemisphere lesions (research group) and 25 normal individuals (control group), aged between 20 and 70 years. RESULTS: No alterations were found on the qualitative data analysis of the hearing behavioral assessment of both groups. Both groups showed alterations in the BAEP and AMLR results, with statistically significant differences between groups for both potentials and a higher occurrence of alterations in the research group. The lower brainstem was the most frequent alteration type in the BAEP, and a statistically significant difference between groups was observed, with higher occurrence of such alteration in the research group. With regards the AMLR, the alteration predominantly observed was the Both type one (ear effect and electrode effect occurring concurrently) for the research group, and the electrode effect type one for the control group. In the analysis of quantitative data (performed only for the auditory evoked potentials), a statistically significant difference between groups was observed with respect to the BAEP latencies of waves III, V and interpeaks I-III and I-V. Regarding the AMLR measures, a statistically significant difference between groups was observed only for the Na wave latency in the C3/A1 position. For the P300, a difference between groups was observed, with higher mean latencies for the research group. In addition, there was a trend to statistically significant difference between right and left ears in the research group, which showed increased latency of P300 wave in the right ear. CONCLUSION: Right-handed individuals with right hemisphere lesion showed hearing thresholds within normal limits in the behavioral hearing assessment. However, they presented results indicative of central auditory nervous system deficits on the electrophysiological assessment of hearing. Alterations were observed in lower brainstem and in sub-cortical and cortical regions. Hearing difficulties were not perceived by these individuals, suggesting that this signal can probably be related to an auditory hemineglect. Further studies that evaluate the central auditory pathway of individuals with ICS are needed to better characterize the electrophysiological findings
75

Avaliação comportamental, eletroacústica e eletrofisiológica da audição em encefalopatia crônica infantil não evolutiva. / Behavioral, eletroacoustical and electrophysiological hearing evaluation in non progressive chronic infantile encephalopathy.

Karin de Albuquerque Barros Nivoloni 26 August 2005 (has links)
Para avaliar a audição em crianças com paralisia cerebral foi realizada a avaliação comportamental, eletroacústica e eletrofisiológica em 61 sujeitos na faixa etária de três a seis anos e 11 meses, subdivididas em grupo experimental e controle. Foram observadas diferenças estatisticamente significantes na comparação entre os resultados obtidos nos dois grupos, bem como na comparação dos procedimentos no grupo experimental. Existe uma diversidade nos resultados dos procedimentos audiológicos em crianças com paralisia cerebral, o que torna importante a aplicação da bateria completa na determinação do perfil audiológico destas crianças. / In order to evaluate the hearing of children who have cerebral palsy disease the behavioral, eletroacoustical, electrophysiological evaluations were done in 61 people between three and six years and 11 months old, subdivided in experimental and control group. There were statistically significant differences when comparing the results obtained in both groups, as well as when comparing the procedures in the experimental group. There is diversity in the results of hearing procedures in children with Cerebral Palsy, which stresses the importance of a full battery of exams for determining the hearing profile of these children.
76

Avaliação comportamental, eletroacústica e eletrofisiológica da audição em pacientes com lesão isquêmica do hemisfério direito / Behavioral, electroacoustic, and electrophysiological hearing assessment in patients with right hemisphere ischemic lesion

Fernanda Cristina Leite Magliaro 18 August 2009 (has links)
INTRODUÇÃO: O Acidente Vascular Cerebral Isquêmico (AVCI) é o evento mais freqüente dentre os AVCs, sendo caracterizado pela interrupção da irrigação sanguínea ao cérebro, a qual pode acarretar em lesão celular e alterações nas funções neurológicas. As manifestações clínicas desta doença podem incluir alterações das funções motoras, sensitivas, cognitivas, perceptivas, da linguagem entre outras. Sendo assim, é extremamente importante que sejam identificadas possíveis alterações nas vias auditivas, periférica e central, as quais podem prejudicar a qualidade de vida destes indivíduos. OBJETIVO: caracterizar os achados das avaliações comportamentais, eletroacústicas e eletrofisiológicas da audição em indivíduos destros com lesão isquêmica do hemisfério cerebral direito, bem como compará-los aos obtidos em indivíduos normais da mesma faixa etária. MÉTODOS: foram realizadas audiometria tonal, logoaudiometria, medidas de imitância acústica, potencial evocado auditivo de tronco encefálico (PEATE), potencial evocado auditivo de média latência (PEAML) e potencial cognitivo (P300) em 17 indivíduos com lesão do hemisfério direito (grupo pesquisa) e 25 normais (grupo controle), com idades entre 20 e 70 anos. RESULTADOS: Na análise dos dados qualitativos não foram encontradas alterações na avaliação comportamental da audição para os dois grupos. Ambos os grupos apresentaram alterações nos resultados do PEATE e do PEAML, sendo que houve diferença estatisticamente significante entre os grupos, para esses dois potenciais, nas quais o grupo pesquisa apresentou maior ocorrência de alterações. No PEATE a alteração mais freqüente foi do tipo tronco encefálico baixo, sendo que, entre os grupos, houve diferença estatisticamente significante, na qual o grupo pesquisa mostrou maior ocorrência dessa alteração. No PEAML a alteração predominante foi do tipo ambas (efeito orelha e efeito eletrodo ocorrendo concomitantemente) para o grupo pesquisa, e do tipo efeito eletrodo para o grupo controle. Na análise dos dados quantitativos (realizada apenas para os potenciais evocados auditivos) verificou-se, no PEATE, que ocorreu diferença estatisticamente significante entre os grupos com relação às latências das ondas III e V e interpicos I-III e I-V. Para o PEAML, a diferença estatisticamente significante entre os grupos ocorreu apenas para a latência da onda Na na posição C3/A1. Para o P300, ocorreu diferença entre os grupos com relação à latência da onda P300, sendo que o grupo pesquisa apresentou tempo médio de latência maior; além disso, houve uma tendência estatisticamente significante entre as orelhas direita e esquerda dentro do grupo pesquisa, mostrando aumento de latência da onda P300 na orelha direita. CONCLUSÃO: Indivíduos destros com lesão de hemisfério direito apresentaram limiares auditivos dentro da normalidade na avaliação comportamental da audição, entretanto, apresentaram resultados indicativos de déficit no sistema nervoso auditivo central, nas avaliações eletrofisiológicas da audição. Foram observados comprometimentos em tronco encefálico baixo, bem como nas regiões subcorticais e corticais. Dificuldades auditivas não foram percebidas pelos indivíduos, sugerindo que, provavelmente tal sinal possa estar relacionado à uma heminegligência auditiva. Tornam-se necessários mais estudos que avaliem a via auditiva central destes indivíduos para uma melhor caracterização dos achados eletrofisiológicos / INTRODUCTION: The ischemic cerebral stroke (ICS) is the most frequent event among cerebral strokes. It is characterized by the interruption of blood supply to the brain, which can lead to cell damage and alterations in neurological functions. The clinical manifestations of this disease may include alterations in motor, sensory, cognitive, perceptual and language functions among others. Therefore, the identification of possible alterations in both peripheral and central auditory pathways that may impair the quality of life of these individuals is extremely important. OBJECTIVE: To characterize the findings of behavioral, electrophysiological and electroacoustic hearing evaluations in right-handed individuals with right hemisphere ischemic lesion, and to compare such data to those obtained in normal individuals with the same age. METHODS: Pure tone audiometry, speech audiometry, acoustic immittance measures, brainstem auditory evoked potential (BAEP), Auditory Middle-Latency Response (AMLR) and cognitive potential (P300) were carried out in 17 subjects with right hemisphere lesions (research group) and 25 normal individuals (control group), aged between 20 and 70 years. RESULTS: No alterations were found on the qualitative data analysis of the hearing behavioral assessment of both groups. Both groups showed alterations in the BAEP and AMLR results, with statistically significant differences between groups for both potentials and a higher occurrence of alterations in the research group. The lower brainstem was the most frequent alteration type in the BAEP, and a statistically significant difference between groups was observed, with higher occurrence of such alteration in the research group. With regards the AMLR, the alteration predominantly observed was the Both type one (ear effect and electrode effect occurring concurrently) for the research group, and the electrode effect type one for the control group. In the analysis of quantitative data (performed only for the auditory evoked potentials), a statistically significant difference between groups was observed with respect to the BAEP latencies of waves III, V and interpeaks I-III and I-V. Regarding the AMLR measures, a statistically significant difference between groups was observed only for the Na wave latency in the C3/A1 position. For the P300, a difference between groups was observed, with higher mean latencies for the research group. In addition, there was a trend to statistically significant difference between right and left ears in the research group, which showed increased latency of P300 wave in the right ear. CONCLUSION: Right-handed individuals with right hemisphere lesion showed hearing thresholds within normal limits in the behavioral hearing assessment. However, they presented results indicative of central auditory nervous system deficits on the electrophysiological assessment of hearing. Alterations were observed in lower brainstem and in sub-cortical and cortical regions. Hearing difficulties were not perceived by these individuals, suggesting that this signal can probably be related to an auditory hemineglect. Further studies that evaluate the central auditory pathway of individuals with ICS are needed to better characterize the electrophysiological findings
77

Avaliação comportamental, eletroacústica e eletrofisiológica da audição em crianças desnutridas / Behavioral, electroacoustic and electrophysiological hearing assessment of malnourished children

Renata Parente de Almeida 14 December 2012 (has links)
Introdução: A desnutrição energético-protéica é um dos maiores problemas de saúde pública no Brasil, ocorrendo mais frequentemente em pré-escolares e determinando o comprometimento do crescimento. A desnutrição pode provocar alterações no sistema nervoso central, dependendo da intensidade, da época de incidência e da duração da doença, comprometendo irreversivelmente as funções intelectuais. Levando-se em consideração a importância da integridade do Sistema Auditivo Periférico e Central na aquisição e desenvolvimento de fala, linguagem e aprendizado, torna-se imprescindível que anormalidades auditivas tanto periféricas como centrais sejam identificadas e tratadas precocemente nesta população. Objetivo: Caracterizar os achados das avaliações comportamentais, eletroacústicas e eletrofisiológicas da audição em crianças com desnutrição, bem como compará-los aos obtidos em crianças saudáveis da mesma faixa etária. Métodos: Foram realizados exames de audiometria tonal, logoaudiometria, teste dicótico de dígitos, imitanciometria, potencial evocado auditivo de tronco encefálico (PEATE) e potencial evocado auditivo de longa latência (PEALL) em 31 crianças desnutridas (grupo estudo) e 34 crianças saudáveis (grupo controle), com idade entre 7 e 12 anos, de ambos os gêneros. Resultados: Na análise dos dados quantitativos da audiometria tonal foi observada uma diferença estatisticamente significante entre os grupos para os limiares auditivos nas frequências de 250 e 8000 Hz, tendo o grupo estudo apresentado limiares auditivos mais elevados. Na análise qualitativa, não houve diferença estatisticamente significante entre os grupos, apesar de duas crianças do grupo estudo apresentarem perda auditiva discreta. Na análise dos dados qualitativos, não foram encontradas alterações na logoaudiometria para os dois grupos. No teste dicótico de dígitos, houve diferença estatisticamente significante entre os grupos, sendo observada uma maior proporção de crianças com alteração no grupo estudo. Ambos os grupos apresentaram resultados alterados na imitanciometria, não havendo diferença estatisticamente significante entre os grupos. Ambos os grupos apresentaram resultados normais do PEATE. Na análise dos dados quantitativos dos PEALL, verificou-se diferença estatisticamente significante entre os grupos para as latências dos componentes P1, N1 e P300, sendo que o grupo estudo apresentou latências maiores para todos os componentes. Na avaliação da amplitude do P300, houve diferença estatisticamente significante entre as orelhas direita e esquerda do grupo controle, sendo a amplitude do P300 maior na orelha direita. Por sua vez, no grupo estudo, não houve diferença significativa entre as orelhas direita e esquerda. Tanto o grupo controle quanto o grupo estudo apresentaram alterações nos resultados do PEALL, havendo diferença estatisticamente significante entre os grupos para os componentes P1, N1 e P300, sendo que o grupo estudo apresentou maior ocorrência de alterações. O tipo de alteração predominante nos componentes P1 e P300 foi o aumento de latência e, para o componente N1, foi a ausência de resposta no grupo estudo; para o grupo controle, o tipo de alteração predominante nos componentes P1, N1 e P300 foi o aumento de latência. Devido ao predomínio de crianças desnutridas de grau leve (58,1%), não foi possível estabelecer uma correlação entre o grau da desnutrição e a alteração dos PEALL. Conclusão: Crianças com desnutrição apresentaram mais alterações na avaliação comportamental da audição (audiometria tonal e teste dicótico de dígitos) e nos PEALL do que as crianças saudáveis, sugerindo déficit na via auditiva central e alteração no processamento da informação acústica. Há a necessidade de mais estudos para melhor caracterizar as alterações fonoaudiológicas e audiológicas desta população. / Introduction: Protein-energy malnutrition is a major public health problem in Brazil. It is more frequent among pre-school aged children and it compromises growth. Malnutrition may cause changes to the central nervous system depending on its intensity, time of incidence and duration, irreversibly compromising intellectual functions. Considering the importance of Peripheral and Central Auditory System integrity to the acquisition and development of speech, language and learning, it is crucial that both peripheral and central auditory abnormalities are identified and treated early in this population. Objective: To describe the findings of behavioral, electroacoustic and electrophysiological auditory assessments of malnourished children, as well as comparing them with findings from healthy children within the same age group. Methods: The following tests were performed in 31 malnourished children (study group) and 34 healthy children (control group), aged 7 to 12, from both genders: pure tone audiometry, speech audiometry, dichotic digit test, immittance measures, brainstem auditory evoked potential (BAEP) and long-latency auditory evoked potential (LLAEP). Results: While analyzing quantitative data from pure tone audiometry we observed statistically significant differences between groups for hearing thresholds at frequencies of 250 and 8000 Hz; the study group had higher hearing thresholds. As for quantitative analysis, there was no statistically significant difference between groups, although two children in the study group showed slight hearing loss. While analyzing qualitative data we did not find any changes in speech audiometry in any of the groups. As for the dichotic digit test, there was a statistically significant difference between groups, with a higher proportion of abnormal children in the study group. Both groups showed abnormal immittance measures results, although there was no statistically significant difference between the groups. Both showed normal BAEP results. When analyzing quantitative LLAEP data we observed a statistically significant difference between groups in terms of latency of components P1, N1 and P300; the study group had higher latencies for all components. When analyzing P300 amplitudes, there was a statistically significant difference between the right and left ears in the control group; P300 amplitudes was wider for the right ear. On the other hand, the study group did not show any statistically significant difference between the right and left ears. Both the control and study group shoed abnormal LLAEP results. There was a statistically significant difference between groups for components P1, N1 and P300; abnormalities were more frequent in the study group. The type of predominant abnormality in components P1 and P300 was increased latency and for component N1 it was lack of response in the study group; for the control group the type of predominant abnormality in components P1, N1 and P300 was increased latency. Because most children were only slightly malnourished (58.1%), it was not possible to establish a correlation between the level of malnutrition and LLAEP abnormalities. Conclusion: Malnourished children showed more abnormalities in auditory behavioral assessment (pure tone audiometry and dichotic digit test) and LLAEP than healthy children. This suggests a deficit in central auditory pathways and abnormalities in the processing of acoustic information. Further studies are necessary to better describe speech and language and hearing abnormalities in this population.
78

New Approaches to Analyze Sound Barrier Effectiveness

Beale, Michael P. 08 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Highway noise can cause annoyance, affect sleep patterns, and reduce the property value for people in the proximity. Current methods for analyzing the effectiveness of sound barriers only take loudness into consideration. This paper introduces new methods that can be used to analyze the effectiveness of the sound barriers. Our approach uses psychoacoustic measures including sharpness, roughness, fluctuation, strength, and annoyance. Highway noise is non-stationary, therefore each of these metrics are calculated over a short time. Finally analysis is performed the distribution and change over time. We used nth nearest neighbor algorithm to remove sounds that are not a part of the experiment. In the future, this data can be combined with human surveys to see if the change in sound quality due to the presence of sound barriers has a meaningful impact on people's lives.
79

Airborne noise characterisation of a complex machine using a dummy source approach / Caractérisation sonore aéroportée d'une machine complexe utilisant une approche source mannequin

Lindberg, Anders Sven Axel 28 September 2015 (has links)
La caractérisation des sources sonores dues aux vibrations est un défi dans le domaine du bruit et des vibrations. Dans cette thèse, une approche expérimentale pour caractériser la propagation du son d’une machine complexe a été étudiée. Pour caractériser de manière appropriée la source sonore placée dans un environnement quelconque, il a été indispensable de prendre en compte les phénomènes de rayonnement et de diffraction. Cela permet de prédire une pression acoustique. Une technique particulière, appelée source mannequin, a été développée pour répondre à cette problématique. Le mannequin est une enceinte fermée de taille similaire mais qui a une forme simplifiée par rapport à la machine complexe, et sert de modèle de diffraction sonore. Le mannequin est équipé d’une série de haut-parleurs alignés dans le prolongement de la surface de l’enceinte. La superposition du champ acoustique créé par chaque haut-parleur modélise le rayonnement acoustique de la machine complexe. Cette thèse introduit donc le concept de source mannequin et traite de trois problèmes émanant de la mise en pratique de celui-ci : (1) l’estimation du transfert d’impédance dans l’espace (fonction de Green), (2) les spécifications de l’enceinte et de la série de haut-parleurs, et (3) l’estimation des sources équivalentes en termes de débit volumique. L’approche est étudiée au travers de cas d’études expérimentaux et numériques. / The characterisation of vibrating sound sources is a challenge in noise and vibration engineering. In this thesis, an experimental approach to the characterisation of air-borne sound from a complex machine is investigated. A proper characterisation has to account for both radiation and diffraction phenomena in order to describe the sound source when inserted into an arbitrary space which enables prediction of sound pressure. A particular technique — a dummy source — has been conceived to deal with this problem. The dummy is a closed cabinet of similar size but much simpler shape than the complex machine, and it serves as a model of sound diffraction. The dummy is equipped with a flush-mounted array of loudspeaker drivers. The superposition of sound fields created by the individual drivers models sound radiation of the complex machine. This thesis introduces the concept of a dummy source and discusses three problems that need to be addressed for its practical application: (1) estimation of the transfer impedance of the space (the Green’s function), (2) the specification of the cabinet and the driver array, and (3) the estimation of the equivalent source strengths in terms of volume velocity. The approach is investigated via experimental and numerical case studies.
80

Experimental Investigations of Bassoon Acoustics / Experimentelle Untersuchung der Akustik des Fagotts

Grothe, Timo 19 August 2014 (has links) (PDF)
The bassoon is a conical woodwind instrument blown with a double-reed mouthpiece. The sound is generated by the periodic oscillation of the mouthpiece which excites the air column. The fundamental frequency of this oscillation is determined to a large extent by the resonances of the air column. These can be varied by opening or closing tone-holes. For any given tone hole setting a fine-tuning in pitch is necessary during playing. Musicians adjust the slit opening of the double-reed by pressing their lips against the opposing reed blades. These so-called embouchure corrections are required to tune the pitch, loudness and sound color of single notes. They may be tedious, especially if successive notes require inverse corrections. However, such corrections are essential: Due to the very high frequency sensitivity of the human ear playing in tune is the paramount requirement when playing music. This implies, that embouchure actions provide an important insight into a subjective quality assessment of reed wind instruments from the viewpoint of the musician: An instrument requiring only small corrections will be comfortable to play. Theoretical investigations of the whole system of resonator, reed, and musician by use of a physical model nowadays still seem insufficient with respect to the required precision. Therefore the path of well-described artificial mouth measurements has been chosen here. For the separate treatment of the resonator and the double-reed, existing classical models have been used. Modifications to these models are suggested and verified experimentally. The influence of the musician is incorporated by the lip force-dependent initial reed slit height. For this investigation a measurement setup has been built that allows precise adjustment of lip force during playing. With measurements of the artificial mouth parameters blowing pressure, mouthpiece pressure, volume-flow rate and axial lip position on reed, the experiment is fully described for a given resonator setting represented by an input impedance curve. By use of the suggested empirical model the adjustment parameters can be turned into model parameters. A large data set from blowing experiments covering the full tonal and dynamical range on five modern German bassoons of different make is given and interpreted. The experimental data presented with this work can be a basis for extending the knowledge and understanding of the interaction of instrument, mouthpiece and player. On the one hand, they provide an objective insight into tuning aspects of the studied bassoons. On the other hand the experiments define working points of the coupled system by means of quasi-static model parameters. These may be useful to validate dynamical physical models in further studies. The experimental data provide an important prerequisite for scientific proposals of optimizations of the bassoon and other reed wind instruments. It can further serve as a fundament for the interdisciplinary communication between musicians, musical instrument makers and scientists.

Page generated in 0.0687 seconds