Noisy PCs can create an uncomfortable work environment for users. The constant whirring and chirping sounds are distracting and can impede productivity, especially when there are many systems going at once. In this article, I will identify the culprits that generate noise pollution in PCs and show you how to build or modify a PC to make it quieter -- without the use of a sledgehammer. The problem
While a few computer manufacturers have started to account for excess noise in their designs and actually offer prebuilt low-noise PCs, the problem has continued to take a back seat to performance-driven and cost-saving designs that generally treat noise as a secondary issue. (Read more about sound measurements in this sidebar.) At the heart of the problem are the mechanical components used inside modern PCs. The main culprits are the heat generated by power-hungry components and the cooling methods implemented to deal with the problem. Another significant source of noise is the vibrations generated by moving components within drive subsystems.
Noise solutions related to cooling
Since most computer noise is caused by fans, which are necessary to combat heat, and the heat is associated with high-power dissipating components, lowering the power requirements of a system is one method you can use to reduce noise. By reducing power consumption, you can reduce cooling requirements and thereby reduce noise. Water cooling Since fans are the main cause of PC noise pollution, you might ask yourself why you couldn't just get rid of them completely and replace them with another cooling mechanism. Water cooling (or liquid cooling) relies on circulation of a fluid to dissipate heat generated by components. Companies such as Koolance are trying to widen the acceptance of water cooling by providing computer cases with prebuilt water-cooling solutions. The company provides easy-to-install cooling blocks for their cases that can replace fans on CPUs, video cards, and motherboard chipsets, and they even provide cooling for hard drives. However, there are limitations on which CPUs can be used and the dimensions of the motherboards. Also, you still need a power-supply fan, because the company's plan to use liquid-cooled power supplies has been abandoned. This partial solution to the noisy PC problem doesn't come cheap, so you should expect to add the equivalent of at least two to three hundred US dollars to the total cost of each system. Quieter power supplies The fans on power supplies can be a source of clatter if the supply isn't designed for low noise. Also, the higher the power rating of the supply, the greater the potential noise. However, you don't want to sacrifice the advantages and stability of a quality power supply just to reduce noise, and you certainly don't want to underpower your system. That is why quality power supplies with efficient fans are now available that help to minimise excess noise:

• PC Power & Cooling: While their high-quality Turbo-Cool model is noisy, the company also offers an ultra-quiet Silencer model that offers similar specifications to the Turbo-Cool without the excessive noise. They are available in a variety of power ratings, up to 400W.
• Enermax: Some Enermax models come with adjustable fan control knobs that allow you to set the fan speed. With many newer motherboards, Enermax power supplies support a feature that will allow the motherboard to monitor the fan on the supply and turn it off when the PC enters sleep mode.
• QuietPC.com: QuietPC sells 300W and 250W ATX power supplies that it claims will operate under 26 dB(A). The 300W is an ATX12V power supply that can work with Pentium 4 systems. The specifications for these supplies indicate that they are of high quality.

If you already have a high-quality, albeit noisy, power supply, another option to reduce noise is to replace its fan with a quieter case fan. Many power-supply fans are the same size as 80mm case fans. You should use caution when you change out fans, as there will likely be high voltages in the capacitors of your supply even when it is unplugged. In fact, the inside of a power supply on a modern ATX-based system is the only component within the PC's case that poses a significant shock hazard. The risk is minimal, however, because you shouldn't have to touch anything within the supply except the fan and its leads when you are changing it. But be aware that replacing your fan will most likely void your warranty. To replace a case fan, remove the supply from your system and open its case. Find the fan's leads. (The leads are usually soldered to the supply's printed circuit board. Don't try to unsolder them.) Clip the leads with a wire cutter, leaving plenty of length from the circuit board. Strip the ends of the cut leads and the ends of the leads from the new fan. After removing the supply's fan and replacing it with your new fan, connect the leads together with the correct polarity using electrical butt connectors. Replace the supply casing, and you're finished.