How to Design a Quiet PC

If you're bothered by the loud noises your PC makes this excerpt from Building the Perfect PC, Third Edition gives you some options to make it quieter. Or you may decide to build your own PC and design it to be as quiet as possible.

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The ongoing PC performance race has had the unfortunate side effect of making PCs noisier. Faster processors use more power, which in turn requires larger (and noisier) power supplies. Faster processors also produce more heat, which requires larger (and noisier) CPU coolers. Modern hard drives spin faster than older models, producing still more noise and heat. Fast video adapters have their own cooling fans, which add to the din. While building a reasonably quiet PC that performs well is easier today, fast and powerful machines still need plenty of noisy moving air.

Fortunately, there are steps you can take to reduce the amount of noise your PC produces. No PC with moving parts is completely silent, but significant noise reductions are possible. Depending on your requirements and budget, you can build a PC that is anything from quietly unobtrusive to nearly silent. The key to building a noise-reduced PC is to recognize the sources of noise and to minimize or eliminate noise at the source.

The major sources of noise are typically the power supply, CPU cooler fan, and supplementary case fans. Minor sources of noise include the hard drive, chipset fan, video adapter fan, and optical drive. As you design your PC, focus first on major noise sources that can be minimized inexpensively, then minor noise sources that are cheap to deal with, then major noise sources that are more expensive or difficult to minimize, and finally (if necessary) minor noise sources that are expensive or difficult to fix. Use the following guidelines:

Choose a low-power processor

The amount of power consumed by the processor has a direct effect on the noise level of the system. The peak power consumption of mainstream processors ranges from about 30W to 140W. That power ends up as waste heat that must be exhausted from the case. Using a lower-power processor produces less waste heat, which in turn allows you to use a quieter CPU cooler, fewer and quieter case fans, and so on. Power consumption isn't necessarily proportional to processor performance. For example, one processor that draws 70W peak power may be faster than another that draws 130W. None of this is to say that there's anything wrong with choosing a high-wattage processor, but doing so complicates cooling and noise issues.

Choose a quiet case

Inexpensive cases are designed with little thought to noise abatement. Better cases incorporate numerous design features that reduce noise, including large, slow-spinning exhaust fans, sound-absorbing composite panels, rubber shock mounts for drives that isolate vibration, and so on. We cover case considerations thoroughly in the next chapter.

Choose a quiet power supply

In most systems, the power supply is potentially the first or second largest noise source, so minimizing power supply noise is critical. Here are a few tips:

• At the first level, choose a noise-reduced power supply, such as the models we recommend in the next chapter. Such power supplies cost little or no more than competing models of equivalent capacity and quality but are noticeably quieter. A system that uses one of these power supplies can be quiet enough to be unobtrusive in a normal residential environment.
  
  
• The next step down in noise level is a power supply that is specifically designed to minimize noise. These power supplies cost a bit more than comparable noise-reduced power supplies but produce as little as 18 dB at idle, and not much more under load. A system that uses one of these power supplies (and other similarly quiet components) can be nearly inaudible in a normal residential environment. You won't have any trouble recognizing any of these models, because all of them are advertised and promoted as "Quiet PC" or "Silent" models.
  
  
• Finally, some power supplies use huge passive heatsinks rather than cooling fans. These power supplies, such as the FSP ZEN 400 (http://www.fspgroupusa.com), have no moving parts, and the only noise they produce is a very slight buzz from the electronic components.

Choose an efficient power supply

Power supply efficiency has a direct bearing on system noise level. Every power supply requires higher input power than the output power it provides, and that power difference is converted to heat within the power supply. For example, if the system actually requires 200W from the power supply, a 67% efficient power supply draws 300W of input power to provide that 200W of output power (200W/0.67 = 300W). That extra 100W is converted to heat within the power supply. An 85% efficient power supply requires only about 235W of input power to provide 200W of output power. The difference between 300W input and 235W input power translates to an extra 65W of heat within your system. The efficiency of mainstream power supply models ranges from about 65% to 90% or higher.

Note: The 80 PLUS initiative sets standards for power supply efficiency. A power supply that meets the basic 80 PLUS requirements must be at least 80% efficient at 20%, 50%, and 100% load, and must have a power factor (PF) of at least 0.9 at 100% load. The 80 PLUS Bronze certification requires the power supply to be at least 85% efficient at 50% load and 82% efficient at 20% and 100% load, with a PF of 0.9 or better at all three load levels. The 80 PLUS Silver and Gold certifications require the power supply to be at least 85%/88%/85% efficient or 87%/90%/87% efficient, respectively, again with a PF of at least 0.9 at all three load levels.

Less than half of the power supplies currently sold have any 80 PLUS certification. Less than 4% have the 80 PLUS Gold certification, and about the same percentage have the 80 Plus Silver certification. Roughly 20% have the 80 PLUS Bronze certification, and another 20% the basic 80 PLUS certification.

Choose a quiet CPU cooler

As processor speeds have increased over the last few years, manufacturers have gone from using passive heatsinks to using heatsinks with slow, quiet fans to using heatsinks with fast, loud fans. Current processors differ greatly in power consumption from model to model. At the lower end of the range—less than 50W—nearly any decent CPU cooler can do the job with minimal noise, including the stock CPU coolers bundled with retail-boxed processors and inexpensive third-party units. At the middle of the range—50W to 90W—standard CPU coolers begin to produce intrusive noise levels, although specialty quiet CPU coolers can cool a midrange processor with little or no noise. At the upper end of the range, even the quietest fan-based CPU coolers produce some noise. Here are some tips to keep in mind when selecting a CPU cooler:

• For a processor with low to moderate power consumption, try using the stock CPU cooler supplied with the retail-boxed processor. If it produces too much noise, install an inline resistor to reduce the voltage supplied to the fan, which reduces fan speed and noise. Resistor kits are sold by quiet-PC vendors such as FrozenCPU, QuietPC USA, and Endpcnoise.com.
  
  
• For high-current processors, there are several alternatives. The CPU coolers that AMD and (particularly) Intel bundle with their retail-boxed performance processors are much better than they were a few years ago. Even with a hot processor, a retail-boxed CPU cooler does a reasonably good job of cooling the processor with little noise.
  
  
• To minimize noise with any processor, install a Thermalright or Zalman unit. For processors with low to midrange power consumption, some of these premium coolers can be run in silent (fanless) mode, which completely eliminates CPU cooler noise.

Note: If you choose an aftermarket CPU cooler, verify that it is physically compatible with your motherboard and case. Quiet CPU coolers often use very large heatsinks, which may conflict with protruding capacitors and other motherboard components. Most premium CPU cooler manufacturers post motherboard compatibility lists on their websites. It's just as important to verify that the CPU cooler fits your case. Some high-end CPU coolers are physically huge. Before you buy one of those, make sure the chassis structure won't prevent it from being installed, and make sure there's sufficient clearance between the motherboard and case cover that you'll be able to reinstall the cover with the CPU cooler in place.

Choose quiet case fans

Most modern systems have at least one supplemental case fan, and some have several. The more loaded the system, the more supplemental cooling you'll need to use. Use the following guidelines when selecting case fans:

• Case fans are available in various sizes, from 60 mm to 200 mm. All other things being equal, a larger fan can move the same amount of air with less noise than a smaller fan, because the larger fan doesn't need to spin as fast. Of course, the fan mounting positions in most cases are of fixed size, so you may have little choice about which size fan(s) to use. If you do have a choice—for example, if the case has two or three fan positions of different size—use the largest fan that fits.
  
  
• Case fans vary significantly in noise level, even for the same size and rotation speed. Many factors come into play, including blade design, type of bearings, grill type, and so on. In general, ball bearing fans are noisier but more durable than fans that use needle or sleeve bearings.
  
  
• The noise level of a fan can be reduced by running it at a lower speed, as long as it moves enough air to provide proper cooling. The simplest method to reduce fan speed is to install an inline resistor to reduce the supply voltage to 7V. These are available from the sources listed earlier, or you can make your own with a resistor from Radio Shack or another electronics supply store. Some fans include a control panel, which mounts in an available external drive bay and allows you to control fan speed continuously from zero to maximum by adjusting a knob. Finally, some fans are designed to be controlled by the power supply or a motherboard fan connector. These fans vary their speed automatically in response to the ambient temperature, running at high speed when the system is heavily loaded and producing lots of heat, and low speed when the system is idle.
  
  
• The mounting method you use makes a difference. Most case fans are secured directly to the chassis with metal screws. This transfers vibration directly to the chassis panels, which act as sounding boards. A better method is to use soft plastic snap-in connectors rather than screws. These connectors isolate vibration to the fan itself. Better still is to use the soft plastic snap-in connectors in conjunction with a foam surround that insulates the fan frame from the chassis entirely.

The preceding six elements are the major steps required to quietize your PC. Once you minimize noise from those major sources, you can also take the following steps to reduce noise from minor sources. Some of these steps cost little or nothing to implement, and all contribute to quieting the PC:

Put the PC on a mat

Rather than putting the PC directly on your desk or the floor, put a sound-deadening mat between it and the surface. You can buy special mats for this purpose, but we've used objects as simple as a couple of mouse pads, front and rear, to accomplish the same thing. The amount of noise reduction from this simple step can be surprisingly large.

Choose a quiet hard drive

Once you've addressed the major noise sources, hard drive noise may become noticeable, particularly during seeks. The best way to reduce hard drive noise is to choose a quiet hard drive in the first place. Seagate Barracuda and Samsung Spinpoint models are the quietest mainstream hard drives. If even those 7,200 RPM models are too noisy for your requirements, use a 5,400 or 5,900 RPM drive. If even those are too loud, install an SSD.

Choose a video card with a passive heatsink

All video adapter chipsets produce significant heat, but some video adapters use a passive heatsink rather than a fan-based cooler. If possible, choose a video adapter with a passive heatsink.

Choose a motherboard with a passive heatsink

The northbridge chip of modern chipsets dissipates significant heat. Most motherboards cool this chip with a large passive heatsink, but some use a fan-based cooler. Again, these coolers typically use small, fast fans that produce significant noise. If possible, pick a motherboard with a passive heatsink.

Note: Silent PC Review is an excellent source of information about quiet PC issues. The site includes numerous articles about reducing PC noise, as well as reviews of quiet PC components, a forum, and other resources.