"Inflatable Air Blower" axis is not parallel with the motor shaft, pulley misalignment, housing or impeller friction with the air inlet, foundation or impeller loose rivet deformation, impeller or impeller loose rivet deformation, impeller shaft hole and the disk shaft with loose leaves have fouling, dirt, abrasion or bending the shaft of the rotor imbalance, fan inlet and outlet pipe installation poor resonance, chassis and bracket, bearing bracket, bearing and bearing cap bolts and other loose.