Bearing Types
CPU coolers can generally be classified into three types: sleeve bearings, ball-sleeve hybrid bearings, and dual ball bearings.
Among these, sleeve bearings produce the least noise but have the shortest lifespan and are highly susceptible to environmental factors. Dual ball bearings, on the other hand, are noisier but have a longer lifespan and a simpler manufacturing process, making them the mainstream choice. Some improved versions of sleeve bearings have been developed, significantly extending their lifespan while maintaining low noise levels, making them a popular choice for high-end coolers.

Blade Shapes
The most common blade shapes include scimitar, trapezoidal, and the patented folded-edge design by AVC.
Scimitar-shaped blades operate more quietly but generate lower air pressure.
Trapezoidal blades produce higher air pressure but tend to generate more noise.
Folded-edge designs offer the best balance, producing high air pressure while keeping noise levels low, though they are less commonly used.

Number of Blades
CPU fans typically have between 6 to 12 blades.
Fans with fewer blades usually generate higher air pressure but also create more operational noise.
Fans with more blades tend to be quieter but produce lower air pressure.

Airflow Direction
There are two types of airflow designs: axial flow and centrifugal flow.

Axial flow fans direct airflow along the axis of the fan, meaning the air moves perpendicular to the blade rotation surface.
Centrifugal fans push air radially outward in all directions along the blade’s rotation plane.
From a practical standpoint, centrifugal fans are less efficient in cooling as their airflow is harder to utilize effectively, and they generate more noise. However, their design makes it easier to implement in ultra-thin coolers, which is why they are often used in certain graphics card cooling systems.

Fan Speed Categories
CPU fans can be roughly categorized into high-performance (powerful) fans and silent (quiet) fans.
This classification is not strict, but in general, for fans of the same size and type, there is always a trade-off between air pressure and noise—higher airflow and pressure result in louder noise, while quieter operation typically means lower airflow and cooling performance.