空洞形消音器で発生する気流騒音 : 消音器内の流動パターンと騒音スペクトルの関係

概要

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The air flow patterns in the mufflers constructed with one cylindrical expansion chamber were visualized by the tuft-grid and the smoke-wire methods. Next the sound pressure levels (SPL) of the flow noise generated in the mufflers were measured by using the very long tail pipe. It is obvious from the results of these experiments that the spectrum of the flow-generated noise, namely, the relation of the SPL to the center frequencies in the l/3 octarve band (f_b) changes with the flow pattern determined by the ratio of the chamber length (l_c) to the duct diameter (d). The peak value in the spectrum, which occurs regardless of the resonance effects in the tail pipe, shifts toward the higher frequency with increase of the mean flow velocity in the duct (V). Therefore the band SPL-s in relation to overall SPL are showed as the functions of l_c/d and Strouhal number f_bd/V in figure 3.10 (a), (b), (c).
東海大学の論文