During the development of Wingfan S2Z, S4Z and S6Z series of impellers, one of the main objectives was to reduce noise levels. An impressive 2 to 4 dBA noise level reduction was achieved. The wide sickle shaped profiles ensure stable pressure curves, high efficiency and low absorbed power. A given air capacity can often be obtained with a lower number of sickle blades than conventional airfoil blades and therefore at lower cost.