Typical case fans, no matter how quiet when spinning on their own, usually produce clear audible noise when installed as intake case fans. This higher-pitched noise is the result of air turbulence generated between fan blades and the case’s intake grille. The AP81, on the other hand, uses the award-wining fan blade design from AP123 with three distinct shape and sizes to create uneven airflow which is capable of reducing noise frequency effectively compared to traditional fan designs. Besides noise reduction, the unique fan blades are also designed to generate high airflow and static pressure simultaneously for great performance.