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. The days when a high-performance PC sat under your desk making an unobtrusive hum are long gone.
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 that noise at the source.
The major sources of noise are typically the power supply, the CPU cooler fan, and supplementary case fans. Minor sources of noise include the hard drive, the chipset fan, the video adapter fan, and the optical drive. As you design your PC, focus first on major noise sources that can be minimized inexpensively, then on minor noise sources that are cheap to deal with, then on major noise sources that are more expensive or difficult to minimize, and finally (if necessary) on minor noise sources that are expensive or difficult to fix. Use the following guidelines:
Choose a quiet power supply
In most systems, the power supply is the primary noise source, so minimizing power supply noise is critical.
— At the first level, you can choose a standard power supply that is quieter than the norm, such as the Antec TruePower ( http://www.antec-inc.com) or the PC Power & Cooling Silencer ( http://www.pcpowercooling.com), which we describe in the next chapter. Such power supplies cost little or no more than equivalent competing models, and are considerably 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 is a power supply that is specifically designed to minimize noise, such as those made by Nexus ( http://www.nexustek.nl) and Zalman ( http://www.zalmanusa.com). These power supplies cost a bit more than comparable standard 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.
— Finally, there are completely silent power supplies, with no moving parts, that use huge passive heatsinks or convective water cooling to dissipate heat. We haven’t used any of those, so we can’t comment on them.
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, and finally to using heatsinks with fast, loud fans. Current processors vary in power consumption from less than 30W to more than 100W, with proportionate differences in heat production. At the lower end of that range—30W to 50W—nearly any decent CPU cooler can do the job with minimal noise, including the stock CPU coolers bundled with retail-boxed processors or inexpensive third-party units like those made by Dynatron ( http://www.dynatron-corp. com). In the middle of the range—50W to 80W—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 noticeable noise.
— For a slow processor, try the stock heatsink/fan unit 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. Such resistor kits are available from specialty quiet-PC vendors such as QuietPC USA ( http://www.quietpcusa.com) and Endpcnoise.com ( http://www.endpcnoise.com).
— For a midrange or fast processor, there are several alternatives. Some of the CPU coolers bundled with Intel Pentium 4 processors are reasonably quiet in stock form, and can be quieted further while still providing adequate cooling by using an inline resistor to drop the supply voltage to 7V. However, Intel uses different CPU cooler models and changes them without notice, so what you end up getting is hit or miss. For the quietest possible fan-based cooler, use the Thermalright SLK-900U/A ( http://www.thermalright.com) for an Intel Celeron/Pentium 4 or AMD Athlon, or the Zalman CNPS7000A-Cu or CNPS7000A-AlCu for an Intel Celeron/ Pentium 4 or an AMD Athlon/Athlon 64.
— To minimize noise for any processor, install one of the Thermalright or Zalman units listed above. In particular, with slow and midrange processors (up to the Northwood-core Pentium 4/2.8), Zalman “flower” coolers can be run in silent (fanless) mode, which completely eliminates CPU cooler noise.
If you choose an aftermarket CPU cooler, verify that it is physically compatible with your motherboard. Quiet CPU coolers often use very large heatsinks, which may conflict with protruding capacitors and other motherboard components.
Monitoring CPU Temperature
Most modern motherboards provide temperature sensors at important points such as the CPU socket. The motherboard reports the temperatures reported by these sensors to the BIOS. You can view these temperatures by running BIOS Setup and choosing the option for temperature reporting, which can usually be found under Advanced Hardware Monitoring, or a similar menu option. Alternatively, most motherboards include a monitoring utility—Intel’s, for example, is called the Intel Active Monitor—that allows you to monitor temperatures from Windows rather than having to run BIOS Setup.
CPU temperature can vary dramatically with changes in load. For example, a CPU that idles at 30°C may reach 50°C or higher when it is running at 100% capacity. A hot-running modern processor such as a fast Prescott-core Pentium 4 may reach temperatures of 70°C or higher under load, which is perilously close to the maximum acceptable temperature for that processor. It is therefore very important to verify that your CPU cooler and system fans are doing their jobs properly.
An idle temperature of 30°C or lower is ideal, but that is not achievable with the hottest processors, which idle at 40°C or higher with any but the most efficient CPU coolers. In general, a CPU cooler that produces an idle temperature of 40°C or lower suffices to cool the CPU properly under load.
If you want to verify temperature under load, run an application that loads the CPU with intense calculations, ideally with lots of floating-point operations. Two such applications we have used are the SETI@home client ( http://setiathome.ssl.berkeley . edu) and the Mersenne Prime client ( http://mersenne.org). Run the application for an hour to ensure that the CPU has reached a steady-state temperature, and then use the temperature monitoring application to view the temperature while the application is still running.
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 60mm to 120mm or larger. 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 sizes—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 the fan at a lower speed, as long as it still 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 above, or you can make your own with a resistor from Radio Shack or other 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 at 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 three steps are the main issues to address in quietizing 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 the PC 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 more 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 ATA and S-ATA models are the quietest mainstream hard drives available. To reduce hard drive noise further you can use a Smart Drive Enclosure or the Zalman Hard Drive Heatpipe, both of which are available from the sources listed above.
Choose a video card with a passive heatsink
All video adapter chipsets produce significant heat, but most use a passive heatsink rather than a fan-based cooler. If possible, choose a video adapter with a passive heatsink. If you must use a high-end video adapter with a fan-based cooler, consider replacing that cooler with a Zalman Video Heatpipe. The small fans used on video adapters typically run at high speed and are quite noisy, so replacing the fan with a passive device can reduce noise noticeably.
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 (see Figure 1-5 for an example), but some use a fan-based cooler. Again, these coolers typically use small, fast fans that produce significant noise. If you have a choice, pick a motherboard with a passive heatsink. If you must use a motherboard with a fan-based chipset cooler, consider replacing that cooler with a Zalman Motherboard Heatsink.
Use an aluminum case
Aluminum conducts heat better than steel, so using an aluminum case makes it easier to cool a system effectively. This has no direct impact on noise level, but it does allow you to use smaller, quieter fans than what you would need with a steel case. In effect, the aluminum case itself becomes a giant heatsink, radiating heat directly. Aluminum cases typically cost more than steel cases and their additional cooling efficiency is relatively minor, so this is probably the last step you should take in designing a quiet mainstream PC.
What Are dBs, Anyway?
Disclaimer: The following is a gross oversimplification, and we’re sure we’ll hear about it from people who know more about sound than we do. But here goes.
Sound is measured and specified in deciBels—a tenth of a Bel—which is abbreviated dB. (Some components specify Bels; multiply by 10 to get dB.) Because humans perceive identical sound levels at different frequencies as having different loudness, various weighting schemes are used. The most common, A-weighting, is abbreviated as dB(A). There are also dB(B) and dB(C) scales, but those are not commonly used.
A sound level of 0 dB is defined as the threshold of hearing, a sound level that is just barely perceptible in the absence of any other sound. Here are some reference points:
20 dB – A very quiet library or church; rural background noise at night; the quietest possible PC with moving parts
25 dB – A whispered conversation; a very quiet PC
30 dB – Suburban background noise at night; a quiet PC
40 dB – A quiet conversation; a standard PC
50 dB – Normal household noise; a normal conversation at 1 meter; a loud PC
60 dB – Office conversation; a loud gaming PC or server
The dB scale is logarithmic, which means that an increase of about 3 dB doubles sound level. For example, if a power supply produces 30 dB and a CPU fan also produces 30 dB, running both at the same time doubles sound level to 33 dB (not 60 dB). Doubling the sound level again by running four 30 dB devices simultaneously increases the sound level by 3 dB again, to 36 dB. Running eight such devices doubles the sound level to 39 dB, sixteen takes it to 42 dB, and so on.
However, because of the way humans perceive sound, a 1 dB difference is barely perceptible, a 3 dB difference is noticeable, and a sound must be about 10 dB louder to be perceived as “twice as loud.” For example, if one computer produces 40 dB and another 30 dB, the first computer actually produces more than eight times the sound level of the second, but to human ears it “sounds” only twice as loud.
PC components differ dramatically in sound levels. For example, a very quiet hard drive might produce 25 dB, while another model may produce 30 dB or more. At idle, a standard 400W power supply might produce 40 dB, a quieter model 30 dB (half as loud), and a specialty quiet model only 20 dB (half as loud again). The same differences exist among other noise-producing components, such as CPU coolers, supplemental case fans, optical drives, and so on. Merely by choosing the quietest standard PC components rather than noisier alternatives, you can reduce the noise level of your PC noticeably.
Silent PC Review ( http://www.silentpcreview.com) 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.
This chapter is from Building the Perfect PC by Robert Bruce Thompson and Barbara Fritchman Thompson (O'Reilly, 2004, ISBN: 0596006632). Check it out at your favorite bookstore today. Buy this book now.
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