| What used to be called a standard computer fan was 80 mm square. Nowadays they use all sizes from 40 mm (1U rack-mount) to 120 mm (and occasionally larger). Laptops use even smaller ones.
The smaller fans have to spin at high RPM in order to move any air and are, therefore, noisier than the big ones. Since you can't change the fan's size, all you can do is replace it with the quietest one of the same size that you can find.
Fans are usually easy to replace as they are often screwed to the cover of the enclosure. So you just take the cover off, unplug the fan, and unscrew the fan from the cover. If you're lucky, the manufacturer used one of a few standard fan connectors, in which case you'll be able to buy the new fan with the same connector type already installed.
If the fan is installed as an exhaust fan (pushes hot air out of the enclosure), you have the option of installing a thermally controlled fan. It senses the temperature of the air it is exhausting, and adjusts its speed accordingly. |