S5  Controle Ativo de Vibrações e Estruturas Inteligentes    Titulo: INFLUÊNCIA DO CONTROLADOR FILTERED-X LMS NAS IMPEDÂNCIAS DE UM DUTO   Resumo : INFLUENCE OF THE FILTERED-X LMS CONTROLLER IN THE IMPEDANCES OF A DUCT ABSTRACT. IN THE LAST DECADES, THE ACTIVE CONTROL OF NOISE IS BECOMING MORE WIDELY INVESTIGATED. SEVERAL APPLICATIONS HAVE APPEARED, SUCH AS THE ACTIVE CONTROL OF NOISE IN DUCTS. THE CONTROL METHODS ARE GETTING MORE AND MORE VARIED AND SOPHISTICATED. NOWADAYS, ONE OF THE MOST USED IS THE "FILTERED-X LMS". THIS WORK INVESTIGATES THE BEHAVIOR OF IMPEDANCE IN A DUCT OBSERVED BY THE DISTURBANCE SOURCE WHEN THE "FILTERED-X LMS" CONTROLLER IS WORKING. THE EXPERIMENTAL SET-UP HAS BEEN IMPLEMENTED USING TWO LOUDSPEAKERS, ONE AS DISTURBING SOURCE AND THE OTHER AS THE CONTROL SOURCE, PLACED TRANSVERSELY TO THE DUCT. THE IMPEDANCE MEASURES OBTAINED FROM THE QUOTIENT BETWEEN PRESSURE AND VOLUME VELOCITY. THE PRESSURE WAS MEASURED USING SEVERAL MICROPHONES PLACED ALONG THE DUCT, WHILE THE VOLUME VELOCITY WAS MEASURED USING A LASER DOPPLER VIBROMETER TO MEASURE THE VELOCITY OF THE LOUDSPEAKER CONE. IT WAS OBSERVED THAT THE CONTROLLER SIGNIFICANTLY CHANGES THE MEASURED IMPEDANCES AT POINTS LOCATED UPSTREAM RELATIVE TO THE ERROR MICROPHONE THERE IS A SMOOTHING OF THE IMPEDANCE CURVES WHILE AT LOCATED DOWNSTREAM AND AT THE ERROR MICROPHONE THE IMPEDANCES ARE GLOBALLY REDUCED. KEY WORDS: FILTERED-X LMS CONTROLLER, ACOUSTIC IMPEDANCE MEASUREMENT IN DUCTS, ACTIVE NOISE CONTROL IN DUCTS.     Autores : Arruda, José Roberto de França Donadon, Lázaro Valentim dos Santos, José Maria Campos Nunes, Ronaldo Fernandes     Trabalho Completo :   COBEM99 | Comissão  Organizadora | Palestras | Sessões Técnicas | Autor | Simpósios e Sessões Especiais | Revisores |  Título  dos  Trabalhos | Local