By Michael Farnsworth
(Please note: This is more or less the article that appeared in the October issue of the prestigious and informative EQ Magazine. The article as it appeared in the magazine has some photos of some of the components mentioned in this article. Many thanks to Craig Anderton and the wonderful staff there. If you are into audio recording and production, this magazine is an excellent and invaluable resource.)
Acoustically quiet computers are essential for digital audio workstations (DAW's), home theaters, and professional work areas. Dedicated single-purpose computers such as DAW's deployed in production environments where extreme quiet (if not total acoustic silence) is mandatory, such as sound recording and music production studios, are usually custom designed and built. If you require an extremely quiet or silent PC there are certain key components you need to plan for when specifying your custom build (whether you do it yourself or not) and also certain principles that will help to make your computer quiet. This information also applies to upgrading a noisy computer. The CPU, hard drive, power supply, video card, and RAM all generate heat, so your computer needs cooling. Some PC cases have up to five or more cooling fans, which can create a lot of noise. Drastic options for reducing PC noise include placing your computer in a machine room and using mouse/keyboard/monitor extender cables, or buying a special rack enclosure designed to house, quiet, and cool your computer. However, you can reduce PC noise levels sufficiently to be acceptable with a thorough analysis and treatment. To turn your noisy computer into a very quiet or even silent computer requires minimizing heat generation and build-up, so you need to select the quietest component hardware before building (or if you already have a noisy computer and need to upgrade) by choosing the quietest PC cooling methods possible for each of these components, plus using appropriate acoustic noise reduction treatment, such as specially-designed acoustic dampening (damping) and acoustic foam sound absorption materials. Although I've recommended a few specific products, there are so many options (with new ones arriving all the time) it's impossible to cover all of them. Therefore, this article describes PC noise reduction basic principles so you can make informed decisions on the best approach for designing (or treating) your computer. See the links at the end for more information on products and computer silencing techniques.
Acoustic Soundproofing, Dampening (damping), and Sound Absorbing for Computers
There are several user-installable sound dampening and/or absorbing kits available. (Please note that "damping" is actually the correct term rather than "dampening" in the physics of acoustic principles.) These are often a better buy than purchasing a computer case with soundproofing materials pre-installed because you can customize the installation to your specific hardware. If you aren't planning on extensive upgrading then a PC case with pre-installed acoustic insulation package can work very well if the materials used are specifically and properly designed for that purpose. If you already own a noisy computer a good computer soundproofing package can work serious wonders.
The best kits contain special acoustic foam to absorb noise, along with sound dampening material to inhibit sympathetic vibrations. The foam should be "open-call" foam because "closed-cell" foam doesn't really absorb very much sound, it simply bounces much of it back into the the interior of the case. Closed-cell foam may deaden the sound from inside the computer to stop it from escaping somewhat, but open-cell foam will absorb much more of the energy of the sound waves that hit it, especially if the foam is designed to absorb audible sound wave energy frequencies.
Styrofoam is the perfect example of what not to use! It is closed-cell and highly reflective. The density factor is very low, this is why it is so light in terms of weight. You might as well not bother at all, Styrofoam is acoustically useless for anything except bouncing sound, particularly upper mid-range frequencies such as hard drive and fan whine. The second worse choice is the type of foam used for furniture padding and cushions. Again, it is closed-cell. It is better at acoustic damping and soundproofing than Styrofoam, but sound will still bounce off it to a much greater degree than it will with open-cell foam. Plus, furniture-type foam is generally not as dense as proper acoustic foam which is designed to reduce the amplitude of sound waves that hit it whereas furniture-type foam is not. Even though it will help deaden sound generated inside the computer case (and prevent it from getting outside to a certain degree) we must consider that the sound bouncing around inside keeps the volume of the unwanted noise inside the PC case at a higher level. It is simply not as efficient at noise reduction as an open-cell, higher density, sound-absorbing foam is.
Another thing to be very careful about is making sure any sound reduction products used in a computer are tested and approved to be fireproof. I have tested this property with some so-called computer silencing foam and when I put a match to it the stuff burst into flames immediately plus it emitted a high volume of thick, noxious black smoke. While computer fires aren't all that common it is certainly much more probable to occur if you stick something highly flammable in your computer case. A fan wire with a nick in the insulation can spark and, if left long enough undetected near something flammable, the situation might not have a happy ending.
Computer soundproofing kits with a good "barrier mass" component are ideal; they reduce unwanted resonance and block sound energy. A barrier mass is a layer of denser material that goes between the computer case itself and the layer of acoustic foam. It has more mass than acoustic foam and forms a barrier against sound waves penetrating through it. Barrier mass layers are a different density than the acoustic foam for two main reasons, one is because the more different densities of transmission medium sound waves have to pass through, the more they are diminished. The second reason is so that the panels of the computer case are prevented from vibrating and acting as an acoustic amplifier the same way the body of an acoustic guitar increases the volume of the sound from the strings. This is the sound "damping" (or many people refer to it as "dampening") principle.
Another effective way to deploy open-cell acoustic foam in a computer case is to place blocks of it in unused open spaces such as hard drive and CD bays that are needed. If the foam blocks are slightly tight-fitting they will also prevent structural sound vibration transmission to the PC case panels by damping it while absorbing ambient sound inside the PC case.
A well-designed soundproofing kit can be one of your best investments in your quest to make your computer quiet because it works in many ways and is effective with many of the components simultaneously. If a computer acoustic sound reduction kit is close to the same price as a hard drive noise-elimination case or a quiet CPU cooler/fan arrangement it is often better to start with the PC soundproofing kit since it will help reduce noise from all of the internal components at the same time.
Power Supplies and Fans
A poorly designed power supply is usually the major noise generator in a PC. Inexpensive (cheap!) fans may have poorly designed blades that cause the air to oscillate at audible frequencies as its pulled through the fan housing, as well as inexpensive, noisy bearings. Better fans have improved silent bearings or noiseless sleeve bearings designed to rotate at high RPM with little friction, and a more efficient blade design. Unfortunately, with power supplies its hard for sleeve-bearing fans to move enough air, so ball bearing-based units are usually preferred. A bonus of ball bearing fans is that they often get noisier just before failing, whereas sleeve-bearing fans can seize up without your knowing it potentially leading to failure of the whole power supply. Audible oscillation of air can be generated as the fan pulls air past internal components, adding even more noise. Poorly-designed chassis holes in the power supply case often cause an audible siren effect as air is forced through the openings. Unlike older single-speed power supply fans, some of the better power supplies now available include temperature-sensing circuits and variable speed control so the fan rotates only as quickly as needed for proper cooling. This is good for audio applications, but make sure you check out any power supply under full load; a unit that's quiet when idling can get very noisy when the fans higher speeds kick in. There are now off-the-shelf power supplies that produce in excess of 350W yet are virtually inaudible. Installing a quiet fan in the power supply can be a worthwhile upgrade, but the procedure requires a qualified technician. Power supply capacitors can retain a lethal shock, even when unplugged. Also, the fan connector may be non-standard or may require a direct solder connection to the board.
There are some relatively new models of fanless power supplies now available which are very well designed and very efficient, but remember that the main source of venting for most internal case heat build-up is usually the power supply fan so you may have to install an extra case fan anyway to exhaust the internal case heat. Also, a fanless power supply may not need a fan because it doesn't produce a very high output, so you may not be able to expand your computer without pushing it over the edge. There are more elaborate silencing methods, such as water or oil cooling, but these options are generally impractical in the typical sound production/playback environment. Nesteq offers what is perhaps the best of both worlds in their ASM line of power supplies. These have the option of manual or thermal fan speed control, with a further option of switching the fan off for a completely fanless operation. When selecting a power supply, look for sheathed cables that supply 5V and 12V power on the ATX connector (as well as the serial ATA connectors if so equipped) to the PCs various components. These improve airflow and don't have gaps that can generate noise as air goes through them.
Some power supplies have the exhaust fan mounted on the power supply's bottom. This helps keep fan noise inside the case rather than directly out of the back where there's a more direct path to your ear. However, as the area at the top of the inside of the case behind the power supply gets less air flow, try to mount hard drives toward the bottom of the case to avoid inadvertently creating heat pockets.
Older CPU coolers used heat sinks with a relatively small surface area, coupled with a fixed RPM high-speed fan to move air over the small surface area. Newer CPU cooling systems may use copper instead of aluminum for better heat transfer, employ heatpipe technology, and elaborate heat sink designs that dissipate more heat into the air. If you couple these with a large fan, the fan can rotate more slowly, further reducing noise levels even further. Some heat sink/fan designs, as used in some products pioneered by Zalman, don't couple the two components directly; the fan used in this example may be much larger than traditional designs, and suspended over the CPU heat sink by a special frame that connects to the PC chassis. This reduces noise dramatically due to using a larger fan, and minimizing noise-causing air flow effects. There are also some new models of CPU coolers from that have special sealed internal channels which contain chemical gases that cool more efficiently that traditional pure solid elements such as aluminum or even copper.
Innovative Zalman Quiet CPU Coolers with heatpipe technology are very efficient and quiet.
Some newer CPU's themselves have an improved physical architecture incorporating a narrower internal buss width and generate far less heat as a result. VIA even has a fanless CPU, but the math processing capabilities which are crucial for audio are less powerful than the better-known CPUs. (Its fine for general office duty, however.) CPU fan upgrade kits usually include thermal grease, a paste that maximizes thermal conductivity between the heat sink and the CPU. But its worth spending a little more for something like Arctic Silver 5, which has a special formulation incorporating a high-density filling of micronized silver and thermally conductive ceramic particles.
Hard Drive Enclosures
One of the most painful experiences I ever had in an audio career that spans 20+ years was editing on my first digital audio workstation, which had a Seagate Barracuda II SCSI hard drive. The whine was almost intolerable. Seagate figured out this was a problem, and their newer Barracuda drives are almost silent right out of the box, largely due to a new fluid-bearing design. These drives are now common in audio workstations. If you have a noisy drive, you can mount it in a special audio baffle unit that fits in a spare 5-1/4 drive bay such as the original 'SilentDrive' which is fine for drives dissipating heat levels up to 6.8 watts or for hotter-running drives you can use an enclosure like the SmartDrive 2002C Copper-lined Aluminum Hard Drive Enclosure which can even handle the heat from 15,000 RPM drives, or build a baffle around the area where the drive is mounted with special sheets of acoustic materials designed for this purpose.
Note that heat builds up quickly in an enclosed space. Using an enclosure used to only work for 5,400 RPM drives, and most (but not all) 7,200 RPM drives without overheating them until the newer enclosures became available. Inexpensive, stick-on thermal monitors can indicate the drive temperature, which you can check against the manufacturers temperature ratings to make sure you're not cooking the drive. 10,000+ RPM drives are much more difficult to silence but it can be done. Be realistic about what kind of track counts you need; a slower drive might create a more pleasant working environment.
Case fans, CPU fans, motherboard, and video card cooling fans share the same design considerations described under Power Supplies, and you pretty much get what you pay for. You can also decrease case fan noise with vibration isolation. Even rubber grommets placed over the mounting bolts, between the fan frame and the surface to which the fan mounts, will help reduce the transfer of vibrations to areas of the case that can resonate sympathetically and acoustically amplify the noise. You could also cut your own gaskets out of sound dampening materials and place them between the fan and mounting area. Recently, Acousti Products has introduced some fairly inexpensive, yet effective, silicone gel fan mounting grommets and similar fan gaskets. Acoustic absorbing materials (available from companies that sell components for quieting PCs) can be placed around the airflow path inside the case to absorb noise. Just be careful not to impede the airflow itself. Standard 80mm case fans usually come in one or two wiring configurations, and each has its own type of connector. A four-pin Molex connector (like the type that supplies power to a hard disk drive) delivers 12V DC. It doesn't inherently accommodate speed control. The three-wire type of fan allows feedback from the fan so the user can see the fan speed, and/or an alarm can sound if the fan fails. If your three-pin fan speed isn't controlled by the motherboard, inexpensive fan speed controls let you limit the fan speed to a lower RPM. This can drop unwanted noise levels quite a bit, but make sure there's still enough airflow to dissipate heat.
A fans spec sheet will specify air throughput in CFM, or cubic-feet-per-minute. As a general rule, bigger is better; a 120mm fan rotating at a low speed with usually move more air than a smaller fan running at a higher RPM. I've had the best results so far with the AcoustiFan 120mm fans from Acousti Products, which are literally inaudible. CASES Many people feel that aluminum cases are better at dissipating internal heat buildup than steel; however, a thick steel case reduces mechanical transmission and sympathetic resonance, while providing a barrier mass to stop internal sound from getting out of the case. Well-fitted case parts can help reduce noise that escapes through cracks (e.g., where the side panels meet the front bezel). Some people leave the side of their PC off, thinking it provides more ventilation. However, many cases need to be fully assembled for the air flow design to work effectively. When evaluating PC cases, consider getting a full-sized tower instead of a smaller tower even if you don't need the extra space. A larger internal space means that less air needs to go through the system per minute. Always think efficient air flow and convection is good when installing internal components. If you can leave some air space between multiple hard drives, do so.
Accessories for Heat Control
Motherboard heat sinks, video card heat sinks, memory heat sink spreaders, and round cables (as opposed to ribbon types) are good. Additional heat sinks can help pull concentrated heat out to areas where the heat buildup can be more efficiently dealt with by the fans. Also, new heat pipe technologies (e.g., from Zalman) seem very promising for improving heat dissipation.
PC Cases - The Final Frontier
If you are building your system from scratch or if you want to relocate your components in a new case specifically designed for silence there are now a variety of options available and they come with a wide range of price tags. You can opt for a well-designed conventional case that has comes with acoustic treatment and special goodies like sound-absorbing feet, anti-vibration fan mounts, extra EMI shielding and a special pre-cut AcoustiPack soundproofing materials kit such as the AcoustiCase pictured immediately below:
If a computer is not in a rack, place it on a carpet or some other soft surface to avoid mechanical sound transfer into the floor or other surface on which it sits. Place it as far as possible from reflective surfaces, and put soft carpet or acoustic energy absorbing material on surrounding surfaces to minimize sound reflections. There are a few special case feet on the market that reduce or eliminate mechanical transfer of noise to hard surfaces; I've had excellent results with QuietFeet from Quiet PC and also the AcoustiFeet from Acousti Products.
Cleanliness is next to Quietness
One common and very often overlooked potential source of a noise in a PC is simply not cleaning it regularly. Dust will be sucked in by computer fans over time (unless your computer is kept in a special facility with filtered air) and it will accumulate on fan blades and also heat sinks with fans directing airflow at them as well as everywhere else inside the case in general . A nice coating of dust acts as a thermal blanket to hold the heat in and this will cause chips to run hotter as well as make heat sinks inefficient and ultimately ineffective in really bad cases of dust build-up. The extra heat that is not being released will also shorten the life of your components.
The more heat that is allowed to build up, the faster your cooling fans will need to run. It is ironic that the very devices you are deploying to cool your computer may be inadvertently causing your computer to become noisier over time without a regular cleaning. Heat-activated fans will spin at higher RPM trying to deal with the higher internal case temperatures therefore becoming louder. Computers should be thoroughly cleaned about ever 6-12 months on average depending on how dusty your environment is. A cleaner computer is a cooler-running computer and therefore a quieter computer in most cases.
Some kits contain a mix of various bits of hardware such as a quiet power supply, CPU cooler, and case fan. Fortron makes some excellent kits for folks on tight budgets. Regarding video cards, you don't need a gaming card with a loud fan for most audio work. Less video card memory also means less heat. Many new hard drives and CD-R/DVD components have a smart onboard BIOS that some thermally intelligent motherboards such as the Green motherboards made by Fujitsu Siemens can directly control. Some motherboards have on-board thermal sensors, along with connectors for addition sensors that can be placed inside the case, for advanced thermal control. The fans connected to the motherboard will be speed-controlled accordingly. Also, don't trust all of the dB specs you read for computer components; sadly, many are fabrications. You can generally trust established companies with large product lines and a long production history. The final and surest way to silence a PC is simply to turn it off. A recommended follow-up procedure is to go outside into an area filled with natures serene beauty, or if its night-time, possibly a friendly tavern that serves up a good pint, but only if it has good music . . . or better yet, silence!
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(Please note: This article has been updated in a few places to reflect newer products now available)