The active noise control in ducts: a theoretical experimental study / O controle ativo de ruído em dutos: um estudo teórico -experimental

AUTOR(ES)

Israel Jorge Cárdenas Nuñez

DATA DE PUBLICAÇÃO

2005

RESUMO

This work is dedicated to the study of the problem of active noise control, evaluating some numerical and experimental methodologies. The analysis is restricted to the case of noises in ducts, in which the acoustic propagation phenomena are modeled. Four approaches for this type of models are presented. The first one is formulated by using the basic equations of the acoustics. This procedure generates an infinite dimension model of the duct. In the second approach, the infinite model is truncated by using Taylors series. The third approach performs a modal expansion using the poles of the infinite dimension model, and, in the fourth, it is also considered a modal expansion, but in this case, by taking into account zeros and poles of the infinite dimension model. The four models studied are discussed and compared in the present contribution. A second part of this work is concerned with active noise control techniques. Monochannel (which uses only a loud speaker and a microphone) and multi-channel (which uses several loud speakers and microphones) controllers are studied. The studied active noise controllers use LMS adaptive algorithms. The noise signals are filtered using X-LMS techniques. These types of controller are usually simple and robust. The coefficients of the controller (modeled as a digital filter) are determined by using an online adaptive procedure looking for minimizing the noise levels. The control methodologies are tested numerically by using the mathematical model of the acoustic duct proposed. With the aim of validating experimentally these controllers a test rig instrumented with loud speakers and microphones was built, and the algorithms were implemented using a personal computer. At the remaining, the numerical and experimental results are discussed and some suggestions are presented in order to continue future works.

ASSUNTO(S)

filtros fxlms controle de ruído active noise control controle ativo de ruído engenharia mecanica filtros adaptativos filtered fxlms modelo de duto engenharia acústica duct model

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