0127 矩形ダクト曲がり部に設けたスプリッタの高次モード音波伝ぱに対する効果(J18-2 機械と環境の騒音評価,低減技術(2),J18 機械と環境の振動・騒音評価,低減技術の新展開)

概要

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A splitter that is a thin plate inserted in a rectangular duct can be used as a simple device for attenuating the sound propagating in the duct. In the frequency range where only the plane wave can propagate, this effect is obtained in the case that the splitter is inserted in a duct bend. On the other hand, the splitter in a straight duct works when the (1,0) mode sound wave propagates. In this research, the effect of the splitter inserted in a duct bend is examined experimentally in the frequency range where the (1,0) mode wave can propagate. In this range both the plane and the (1,0) mode waves are transmitted while the single mode wave, either of the plane or the (1,0), enters the bend. Using the measured data of sound pressure, the sound power of each wave is calculated, and then the transmissivity of the splitter is evaluated. The effect of the splitter depends on the splitter length and its insertion position. In addition, the effect differs depending on the mode of incident sound wave.
2007-09-07