Water cooling systems are popular amongst enthusiasts and can provide superior cooling needed for a highly over clocked system. However they are expensive and the overall noise levels are on par with their cheaper counterparts. There's also the additional sound of running water which may put your bladder on overdrive.
Air cooling is reasonably cheap and easy to maintain. There's a wide range of fans available and providing you equip low dBA fans, your PC should be reasonably quiet. In terms of noise level, air cooling seems to be more effective so the following solutions will be based around that principle.
|Silverstone's 400W Passive PSU|
The power supply is one of the loudest components in a computer so should be a careful consideration. Some power supplies have been specifically designed for quiet operation so these are the ones to go for. Fractal Design have released the Newton R2 which runs from 20 to 30dBA. But the Scythe Chouriki 2 can run even quieter at 7 to 21dBA.
There are also passive power supplies which can be used in systems with low power requirements. Passive power supplies typically range from 350 to 500W and don't have a cooling fan. This would significantly reduce noise levels. Although this option would not be suited to most systems.
|Cooler Master's Hyper Z600 Passive Cooler|
Like with power supplies, there are coolers optimised for a quiet PC. Low noise coolers can be purchased and some of these have a replaceable fan that can be swapped with a quieter fan purchased separately. There are also passive coolers available which can cool the CPU without the use of a fan. These would obviously be completely silent but unsuitable for demanding tasks and over clocking.
|The Arctic Cooling Accelero S1 Passive Cooler|
Most graphics cards have reasonably quiet coolers but some of the higher end cards have more powerful fans for the higher temperatures. In these circumstances it may be worth considering a replacement.
You've probably guessed that there's a passive solution for graphics cards too and you'd be right. GPU passive coolers have large metal fins to compensate for the lack of a mechanical fan. For this reason you'll need a hefty case to fit one in your system. As expected, these coolers aren't so great for cooling so if you're temperatures are likely to exceed safe running measures then you'll need to fit an additional fan to tame the heat. Some conventional coolers also allow you to choose the fan. The Thermalright Spitfire is one such product with this particular feature. Combine this cooler with a quiet case fan and you'll be rolling.
|NZXT Sentry Fan Controller|
Fan controller can also reduce noise. These are available as either automatic or manual. With automatic fan controllers a pre-defined temperature is set and the fans will adjust speed according to this figure. This means that the fans won't always be running at full speed and will often be quieter. The manual variety allows the user to adjust fan speed as they see fit. If the computer is idle or resources are in low demand then the fans can be set to a lower speed and the computer will be quieter.The only problem with this is that bad decisions could lead to your computer overheating so an element of care is needed here.
Noise from the system can be emitted through the case. Fans and other components can also cause vibrations which produce noise. Inner panelling can be purchased which absorbs the sound, making the computer quieter. There are also vibration guards that are fitted onto fans to reduce vibration.
|The Scythe Quiet Drive Enclosure|
Conventional hard drives have rotating platters. Because they function mechanically, they make noise. Solid state drives don't have mechanical parts so they are also a lot quieter. These are a lot more expensive that standard hard drives so large storage space isn't usually an option (unless you're filthy rich of course). For large storage space a standard hard drive is needed. Hard drives with a low RPM (Revolutions Per Minute) will have slower rotations of the platters and will generally be quieter. The downside to this is that the hard drive will be slower. The hard drive can also be muffled with an enclosure. This will reduce noise but increase the temperature of the hard drive. This shouldn't be a problem as hard drives are usually located at the front of the PC, right behind the intake fan.
The upgrades with the greatest impact will probably be the power supply and the CPU cooler. Decent power supplies can be expensive but it should reduce noise. Case fans are relatively cheap so that's an alternative option. If all measures are taken to reduce noise then you should end up with a silent beast. However this is only an assumption as I'm currently broke and can't afford many upgrades.