130 ドアミラーから放射される空力的な異音の能動制御(新しい騒音・振動改善技術(4),騒音・振動評価・改善技術)

概要

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In order to reduce an aerodynamic tonal noise from a rearview mirror, active control technique with oscillating jets was utilized. Since the aerodynamic tonal noise of rearview mirror was generated by a small perturbation caused by a small step on a surface of the rearview mirror, oscillating jets were introduced to break it. Wind tunnel experiments were conducted to measure aerodynamic sound and flow fields around the two dimensional backward-facing step. The experimental results showed that the noise reduction level depended on the frequency and intensity of the oscillating jets. The noise reduction level was over 40dB at the oscillation frequency about 400Hz and the amplitude of the jet about 1.0m/s. Both of the frequency and intensity of the jet were smaller than the frequency of the feedback noise (2kHz) and the velocity of the uniform flow (30m/s). These results indicated that the oscillating jets effectively reduced aerodynamic noise with small amount of energy.
一般社団法人日本機械学会の論文
2007-07-18