Fans are used to move a large volume of air for ventilation, by bringing in fresh air from the
outside, blowing out dust, vapour or oil mist from an industrial environment, and for a drying or
cooling operation, etc. Industrial fans are usually low-speed, low-static-pressure and have a large volume flow rate. Ideally, fans should operate at the maximum efficiency point on the pressureflow
curve characteristic. Therefore, the choice between axial or centrifugal fans is made by the
manufacturer to satisfy maximum efficiency at a certain static pressure/flow rate.
Three basic noise sources are