329 開口部を有するダクトから発生する流体騒音 : 第2報,直管ダクトの流体音特性

概要

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An air conditioning equipment is usually set in a rail vehicle in order to keep comfort. However the noise is offensive to the ear especially when the rail vehicle is in a stop. Then the noise reduction is very important from the point of view of keeping the car room comfortable and is one of the distinguished techniques. This paper describes characteristics of flow noise generated from the duct with some holes. Both the acoustic experiment and the flow experiment were carried out in various parameters such as the flow velocity, the absorbing ability and the hole area by use of the straight duct. As a result, it was clarified that the noise reduction effect of the absorbing treatment was a little when the noise source was made only by the flow and is much when the fan noise is greater than the flow noise. Moreover the effect of the flow on the noise reduction effect of the absorbing treatment could not observed in case of the velocity being less than 30m/s.
2007-09-25