This site provides quieting and silencing solutions for 12v and 5v fans in PCs, computers and electronic equipment. Several options are available to quiet noisy fans, these include the following 3 options:

Lubricate the fan. To do this, you will need to remove any barrier to the bearing or sleeve area of the fan. Use any lightweight mechanical oil, such as sewing machine oil or 3-in-1 household oil. Do not use WD-40.

Replace the fan. Replacing the fan can be a difficult project because it is hard to find another fan that fits in the exact same place. If you decide to replace the fan itself, you need to ensure that the voltage, size, width, height and mounting hardware all match.

Install the Noisy Fan Quieting Component. This component easily installs on one of the wires going to the fan. It starts the fan at full speed, and then slows the fan speed down slightly to reduce vibration and fan noise. This component has been used successfully on power supply fans, CPU fans and in electronic equipment fans (specifically hubs and routers) since 2002. Benefits of the Noisy Fan Quieting Component include:

• Easy installation without replacing the fan.
• Quiets fan noise by half to two-thirds of the previous sound level.
• Reduces vibration and wear.
• Increases fan life.
• Provides for consistent speed control with controlled voltage drop.
• Reduces dust buildup.
• Maintains nearly the same temperature of cooled components.