ダクト内騒音能動制御のインピーダンスによる解析

概要

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In this paper, the principle of the active control of noise in duct is analyzed by means of impedance. It is shown that the principle is equivalent to making a short circuit on a transmission line by the equivalent impedance of the active system. From the result of the analysis, general equations and their equivalent circuits of multi-microphone and multi-loudspeaker system are deduced, and also general requirements for control without acoustical feedback which makes the system unstable, are made clear. For the practical use, some suitable combinations of microphones and loudspeakers which control the noise without acoustical feedback are shown. In addition, an electrical method by which the acoustical feedback is canceled is proposed.