111 Study on lock-in condition of edge-tone by disturbance sound

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  • 111 外乱音によるエッジトーンのロックイン条件に関する研究(空力騒音(1))

Abstract

A sound level of noises generating from aero flow often grow by resonance of eddy fluctuation sound around structure objects and by lock-in phenomenon of the eddy fluctuation into the resonance sound frequency. An understanding of lock-in conditions is important to the control of the aero flow noise. We made a virtual resonance system in an edge-tone system by adding of disturbance sound to a part of the air nozzle and measured frequencies and sound pressure levels of the disturbance sound. This study evaluates the condition of lock-in phenomenon from the results. Edge tone locked in disturbance sound at about -18dB from the edge tone level without disturbance if the edge-tone frequency is close to disturbance frequency. If the edge-tone frequency is 20% away from disturbance, edge-tone locked in at a few dB lower than edge tone level.

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