Flow Characteristics of the Sound Pressure Level and its Prediction for a Low Pressure Axial Flow Fan

The relation between the noise level of an axial flow fan and the flow around the fan rotor was investigated over a wide range of fan flow rates. The magnitude of the wake width in the region where the velocity of air relative to the blade is large controls the noise level. The change in the noise level with fan flow rate can be estimated by a working formula proposed by the present authors for predicting the noise level of a fan working at its design point