Low Noise High Efficiency Centrifugal Blower

A centrifugal blower for HVACR applications includes a squirrel cage forward-curved blower fan and a scroll housing. The blower fan comprises a plurality of blades that are configured to emit air radially outward and tangentially from between the blades when the blower fan rotates at a first speed. The air so emitted has a deviation angle defined as the difference between the direction of the emitted air and the blade exit angle. The scroll housing has a spline-shaped wall that has an axial cross-section that is configured such that the deviation angle of the air emitted from the blower fan at an axial plane deviates by no more than fifteen percent circumferentially about the blower fan in-between the spline-shaped wall and the blower fan and such that the average tangential velocity of air between the spline-shaped wall and the blower fan deviates by no more than thirty percent.