Acoustic and Flow Noise Characteristics of Duct with Expanded Part and Some Holes

Kunihiko Ishihara

Noise from an air conditioning duct of a rail vehicle is annoying for passengers especially when the rail vehicle is in a resting state. Then the noise reduction is very important from the point of view of keeping the car room comfortable and is one of the differentiating techniques. This paper described experimental results of flow noise characteristics. The air conditioning duct has some holes to ventilate the car room. I have studied the acoustic characteristics of the flow noise of the straight duct and the bending duct previously. In this study, the flow noise characteristics generated from the air conditioning duct have been studied experimentally by using the duct with expanded part and four holes. As a result, it was clarified that the noise increasing due to expanding is about 10dB and the effect of the absorbent is 3dB ～4dB in the existing of the flow.