Análise do problema de realimentação estrutural de um aparelho auditivo

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia MecânicaOs aparelhos auditivos são projetados para auxiliar indivíduos com perda auditiva, a qual ocorre em determinadas faixas de frequência sonora, sendo variável para cada indivíduo. O princípio de funcionamento dos aparelhos atuais consiste na captação do sinal sonoro pelo microfone, convertendo-o em um sinal elétrico, que é processado de modo que haja amplificação deste. Após isso, o alto-falante o converte em sinal sonoro (onda de pressão sonora), e assim se transmite à orelha do usuário. Trivialmente, devido à proximidade dos componentes, ocorre o problema de realimentação de sinal, tanto externa quanto internamente. Este se trata da vibração via estrutura interna do aparelho, em que a principal fonte é o alto-falante. Por conseguinte um apito é gerado, causando desconforto ao usuário. No estudo proposto foi investigado a realimentação interna no protótipo de um aparelho auditivo do tipo retro-auricular (fabricação Amplivox LTDA) via estrutura das carcaças plásticas. Foram realizadas análises experimentais, sendo feita validações numéricas pelo Método de Elementos Finitos (FEM), o que permite analisar e quantificar os problemas antes do produto ser fabricado. A metodologia adotada foi comparar (experimental e numericamente) o nível de vibração das carcaças, causado pelo alto-falante na região próxima e outra afastada do microfone. Para isso, numericamente, simplificou-se o modelo, em que o alto-falante foi considerado um corpo rígido (massa pontual) e sua suspensão de isolamento de vibrações como molas. Logo, foi necessário caracterizar materiais, verificar o comportamento dinâmico das carcaças pela análise modal experimental, analisar a força de excitação que o alto-falante gera quando em funcionamento e validar os modelos numéricos com o uso de um software comercial.Hearing aids are designed to overcome the hearing loss suffered by some individuals, which occurs in certain frequency ranges and is dif-ferent for each individual. These devices work by capturing the sound signal through the microphone and converting it into an electrical signal, which is processed in order to amplify it. The receiver then converts it into a sound signal (sound pressure wave) and it is eventually transmit-ted to the user's ear. As the microphone and the receiver are near, a feedback signal issue oc-curs, both externally and internally. The internal feedback is caused by structural vibrations produced mainly by the receiver. As the suspension receiver is not perfect, it vibrates the shells producing internal feedback. Then, a whistle is generated causing discomfort to the hearing aid user. In the proposed study, the internal feedback was investigated in proto-type Behind-The-Ear (Acoustic Amplivox-BR) through hearing aid shells. A numerical modeling based on Finite Element Method (FEM) for representation of the components was used to analyze and quantify the problems before the product was manufactured. The methodology that was used aimed to compare (experimental and numerically) the vibration level of shells caused by the receiver located near and far from the microphone. Thereby, the model was simplified numerically, in which the receiver was considered as a rigid body and its suspension isolation of vibrations as springs. Thus, it was necessary to characterize the material of shells, check the dynamic behavior of the shells by experimental modal analysis, analyze the operation excitation force of the receiver and validate the numerical models using commer-cial software

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

Generalized averaged Gaussian quadrature and applications

A simple numerical method for constructing the optimal generalized averaged Gaussian quadrature formulas will be presented. These formulas exist in many cases in which real positive GaussKronrod formulas do not exist, and can be used as an adequate alternative in order to estimate the error of a Gaussian rule. We also investigate the conditions under which the optimal averaged Gaussian quadrature formulas and their truncated variants are internal

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described