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A quiet PC is a personal computer that makes little noise. Common uses for quiet PCs include video editing, sound mixing, home servers, and home theater PCs. A typical quiet PC uses quiet cooling and storage devices and energy-efficient parts.

Like noise, the term "quiet PC" is subjective^[1] and there is currently no standard definition for a "quiet PC". However, a general definition accepted by some is that the sound emitted by such PCs should not exceed 30dB when measured 1 meter away from the computer.^[2] In addition to the average sound pressure level, the frequency spectrum and dynamics of the sound are important in determining if the sound of the computer is noticed. Sounds with smooth frequency spectrum (lacking audible tonal peaks), and little temporal variation are less likely to be noticed. The character and amount of other sound in the environment also affects how much sound will be noticed or masked, so a computer may be quiet with relation to a particular environment or set of users.^[1]

Contents 1 Causes of noise 2 Noise reduction methods 2.1 Common noise reduction methods 2.2 Low/no cost methods 3 Sound Power and Pressure Measurement 4 Individual components in a quiet PC 4.1 Cases 4.1.1 Case Airflow 4.1.2 Case Soundproofing 4.2 Cooling Systems 4.2.1 Heat sinks 4.2.2 Fans 4.2.3 Watercooling 4.3 Power supplies 4.4 Motherboards 4.5 CPUs 4.5.1 Modern low power CPUs 4.6 Video cards 4.7 Secondary storage 4.7.1 Hard drives 4.7.2 Solid-state storage 4.7.2.1 Flash memory 4.7.2.1.1 Solid-state drive 4.7.2.1.2 Compact Flash cards 4.7.2.1.3 USB flash drives 4.7.2.2 Gigabyte i-RAM 4.7.2.3 Problems and solutions 4.7.3 Optical drives 4.8 Laptops 4.9 Monitors 4.10 Printers 5 References 6 External links

[edit] Causes of noise

The main causes of PC noise are:

• Mechanical friction noise generated by micro motors and fan bearings, as well as vibration noise from low quality chassis and improper assemblies.
• Turbulence caused by obstructions in the flow of air, such as poorly designed fan grilles and heatsinks.
• Noise generated by electrical coils or transformers used in power supplies, motherboards, video cards or LCD monitors.^[3]

Noise in personal computers has been increasing with rising computing power and number of transistors on a single die (integrated circuit). More transistors of a given size use more power, which releases more heat. Faster-rotating cooling fans are one common way to remove this heat. Also, motor rotation speed for hard disc drive (HDD) and Optical disc drive (ODD) has been rising for faster data processing with technical advances in micro motors. Faster rotation (usually measured in RPM) causes higher bearing friction, thus more noise, given the same bearing technology.

The noise issue had received widespread attention with AMD's early Athlon CPUs and Intel's Pentium 4 Prescott core CPU known for its excessive heat and bundled fan noise running on high RPM. With the introduction of Home Theatre PCs (HTPC), the excessive heat and noise problem, that had been mostly confined to the overclocking and quiet computing communities, came to the attention of the general public.

The main approaches to reducing noise problems from personal computers are:

1. Reduce heat generation by using energy efficient parts - nearly all the energy used by a computer is converted into heat.
2. Improve cooling - by using more efficient cooling parts and lower friction, quieter bearings.
3. Use Soundproofing to reduce the effects of remaining noise sources.

[edit] Noise reduction methods

Reducing noise with new CPU cooler.

[edit] Common noise reduction methods

• Replacing heat sinks with more efficient models. This often entails the use of larger copper or aluminum heat sinks which may incorporate heat pipes.
• Replacing fans with passive cooling solutions where possible, such as fans on motherboards and GPUs.
• Replacing fans with low-speed, large-diameter fans with low bearing and motor noise. Larger fans can move more air per revolution than smaller fans.
• Mounting fans on anti-vibration mounts.
• Replacing the power supply with a quieter model. The main considerations, from a noise-reduction point of view, in choosing a power supply are fan quality, AC/DC conversion efficiency, and how good the thermal fan speed control is at keeping the fan running slow and steady. Efficiency is important because the less heat that is produced the less work the fan has to perform.
• Replacing hard drives with quieter models. Hard drives can also be replaced with laptop hard drives, with solid state devices like compact flash or networked file systems like NFS.
• Covering the case with sound insulation material such as rubber, foam or fiber mat, although this method has limited effectiveness. The material can (because of its weight) dampen case resonance, and can also absorb some high-frequency sound. Care must be taken to be sure the soundproofing does not interfere with airflow and cooling.
• In energy-hungry computers, water cooling may be necessary for quiet operation. Older water pumps sometimes can make systems noisier than air-cooled, low-power computers. However, recent advances in 12v DC pump technologies has resulted in many pumps being inaudible. In a modern watercooling system geared towards silence rather than performance, the loudest component in the computer is often the Hard Drive or Optical disc drive when performing accesses to the media.
• Placing a dampening material around hard drives (or other spinning drives) such as Sorbothane

[edit] Low/no cost methods

• Undervolting CPUs. Many of today's CPUs can run stably at their stock speed, or even with a slight overclock, at a reduced voltage, which reduces heat output. Underclocking can be done for the same effect, however this reduces performance and is not as effective as undervolting; all the same, underclocking may allow further undervolting. Power consumption is approximately proportional to V²·f, that is, it varies linearly with the clock frequency and quadratically with the voltage.^[4] This means that even a small reduction in voltage can have a large effect in power consumption. Undervolting and underclocking can also be used with chipsets and GPUs.
• Reducing fan speed. This is easily done for fans with Molex connectors.^[5] With 3-pin fans, either fixed inline resistors or diodes, or commercial fan controllers such as the Zalman Fanmate can be used. Software like speedfan may allow fan speed control. Many newer motherboards support Pulse-width modulation (PWM) control, allowing the fan speed to be set in the BIOS or with software.
• Replacing the fan in the PSU with a quieter one (which still offer adequate airflow to cool the PSU), or undervolting it. Note that opening a PSU can be dangerous.
• Removing restrictive fan grills to allow easier airflow.
• Enabling Cool'n'Quiet for AMD CPUs or EIST on Intel's CPUs.
• Using software such as Nero Drivespeed to reduce the speed of optical drives.
• Isolating hard disk noise, either by using anti-vibration mounts (generally rubber or silicone grommets), or by suspending the hard disk to fully de-couple it from the PC chassis (generally mounting it in a 5.25" drive bay using high-grade elastic).
• Setting the hard disk's AAM value to its lowest setting. This reduces the seek noise produced by the hard drive, but also impacts performance slightly.
• Setting operating system to spin down hard drives after a short time of inactivity. This, however reduces drive's lifespan and commonly conflicts with the OS and running programs, though it can still be useful for drives which are only used for data storage.
• Defragmenting the hard drives to reduce the drive heads' need to search widely for data, also improves performance.
• Arranging components and cables to improve airflow. Wires hanging inside the computer can block the airflow, which can increase heat. They can be easily moved to the side of the case so that air can pass through more easily
• Removing dust from inside the computer. Dust on computer parts will retain more heat. Fans draw in dust along with outside air, it can build up quickly inside the computer. Dust can be removed with a vacuum, Gas duster or air compressor. Special anti static vacuums should be used however to prevent Electrostatic Discharge. Ideally this would be done at least twice every year.

[edit] Sound Power and Pressure Measurement

Though standards do exist for measuring and reporting sound power output by such things as computer components, they are often ignored.^[6][7] Many manufacturers do not give sound power measurements. Some report sound pressure measurements, but those that do often do not specify how sound pressure measurements were taken. Even such basic information as measurement distance is rarely reported. Without knowing how it was measured, it is not possible to verify these claims, and comparisons between such measurements (e.g. for product selection) are meaningless. Comparative reviews, which test several devices under the same conditions are more useful. Although even then, an average sound pressure level is only one factor in determining which components will be perceived as quieter.^[1]

[edit] Individual components in a quiet PC

The following are notes regarding individual components in quiet PCs.

[edit] Cases

Cases designed for low noise usually include reasonably quiet fans, and often come with a relatively quiet power supply. Some cases for quiet computers incorporate heatsinks to cool components passively.^[8]

Cases that provide lots of space make it easier to quiet a PC, both by allowing for airflow and by accommodating large coolers.

[edit] Case Airflow

Noise optimized cases like the Antec P180 and Antec P150 often have ducting and partitioning within the case to optimize airflow and thermally isolate components. For example, the P180 has the PSU mounted in the bottom of the case in an isolated partition. This design feature allows cooler air to enter the PSU, reducing the necessary airflow and accordingly, the noise output of the fan. Apple has also employed this tactic in their G5 workstations in an effort to reduce noise. Antec's Sonata is often considered by the mainstream to be one of the quietest PC cases; however, it has since been surpassed by the P180 and other more-advanced cases.^[9] Vents and ducts may easily be added to regular cases.^[10]

More obstructive fan grills increase pressure drop and lower airflow, necessitating higher fan speeds and more noise output. They also increase the turbulence of the flow, which causes some noise of its own. Cases designed to be quiet typically have wire grills or honeycombed fan grills, which perform almost as well as wire grills; both are far superior to the old style of stamped grill.

Features that facilitate neat cable management, such as brackets and space to run cables behind motherboard tray, help increase cooling efficiency.

[edit] Case Soundproofing

The inside of a case can be lined with dampening materials to reduce noise by:

• attenuating the vibration of the case panels via extensional damping or constrained-layer damping.
• reducing the amplitude of the vibration of the case panels by increasing their mass.
• absorbing airborne noise, such as with foam.

[edit] Cooling Systems

[edit] Heat sinks

Heat sinks that operate efficiently with little airflow are often used in quiet computers. Typically they are (relatively) large, and have larger spaces to allow freer airflow. Often heat pipes are used to help distribute heat. For instance, in 2007, the Scythe Ninja or the Thermalright Ultra-120 were frequently used as CPU heat sinks in quiet computers.^[11][12][13]

[edit] Fans

Bearing and motor noise vary between different fan models and often between different samples of the same model.

Quiet PCs typically use larger (e.g. 120 mm) low-speed fans. Although 140 mm fans are made by some manufacturers, such as Aerocool and Yate Loon, there are very few cases or heatsinks that can use them. Fan adapters, which allow larger fans to be used in place of smaller ones, and fan brackets, like the Zalman FB123, often help when replacing small fans.

Quiet fan manufacturers include Nexus, EBM-Papst, Yate Loon and Scythe. In situations where the resistance to flow is very low, like in free-air conditions, Noctua fans also perform very well.^[14] Extensive comparative surveys have been posted by Silent PC Review^[15][16] and MadShrimps.^[17][18]

Fan controllers can be used to slow down fans and to precisely choose fan speed. Fan controllers can produce a fixed fan speed using an inline resistor or diode, or a variable speed using a potentiometer or Pulse Width Modulation (PWM). Resistor-based fan control feeds the fan a lower voltage, while PWM fan control rapidly cycles between feeding the fan full voltage and no voltage. PWM fan control reduces rotational speed, but can also produce clicking sounds in some fan models. Fans can also be plugged into the power supply's 5 volt line instead of the 12 volt line (or between the two for a potential difference of 7 volts, although this cripples the fan's speed sensing) to run them at a reduced speed.^[5] Most fans will run at 5 volts once they are spinning, but may not start reliably at less than 7 V. Some simple fan controllers will only vary the fans' supply voltage between 8 V and 12 V to avoid this problem entirely. Some fan controllers start the fan at 12 V, then drop the voltage after a few seconds.

Soft mounting fans (e.g. with rubber or silicone fan isolators) can help reduce transfer of fan vibrations to other components.^[19]

Intel has recently developed a piezoelectric fan for use in desktop PCs, which is quieter than motor fans and consumes a fraction of the power.^[20]

[edit] Watercooling

Watercooling is a method of heat-dissipation by transferring the heat through a conductive material which is in contact with a liquid, most often demineralised water and an additive to prevent bacterial growth and provide cosmetic effects. This heated water travels in a loop which usually contains a reservoir, radiator and pump. Recent advances in 12v DC pump technologies (for the first time specifically geared-for pc development) allow for new pumps to be both extremely powerful and extremely quiet. Loops can be made up of any combination of these items and some aren't required such as the radiator or reservoir if alternatives methods are used. The radiator often uses two or more fans to air cool the radiator fins and dissipate the majority of the heat at this point.

The most common loop order is reservoir to pump, radiator then the watercooling block and back to the reservoir. The radiator and fan efficiency has the greatest effect on the noise level and cooling efficiency but watercooling is currently the most effective and potentially quietest methods of cooling above ambient temperatures.

There is an inherent danger in the use of liquid around electrical equipment and leak testing the loop is always recommended before attaching any parts to the motherboard, after all loop connections have been made. The 12v DC pump can be run using batteries or a psu making sure no power is going to any other part of the system. Because of these risks and the use of water under pressure watercooling is a greater technical challenge to set up due to the number of components and case modification usually required.

[edit] Power supplies

PSUs are made quieter through the use of quieter fans, more intelligent fan controllers (ones for which the correlation between temperature and fan speed is more complex than linear), higher efficiency, which reduces waste heat and need for airflow, more effective heatsinks and through designs which allow air to flow through with less resistance.

Selecting a power supply of appropriate wattage for the computer is important for high efficiency and minimizing heat. Power supplies are typically less efficient when lightly or heavily loaded. High wattage power supplies will typically be less efficient when lightly loaded, for instance when the computer is idle or sleeping. Most desktop computers spend most of their time lightly loaded.^[21] For example, most desktop PCs draw less than 250 watts at full load, and 200 watts or less is more typical.^[22]

Power supplies with thermally controlled fans can be made quieter by providing a cooler and/or less obstructed source of air. For instance, the power supply is in a separate compartment in the Antec P180 to keep the air supplied to the PSU cool.

The fan in a power supply can be replaced with a quieter one, although there is a risk of electric shock when doing this, and it usually voids the warranty.

Fanless power supplies are available.

• Some of them are equipped with large passive heat sinks and rely on convection or case airflow to dissipate heat. It is also imperative that such fanless power supplies be installed in a case with good ventilation.^[21]
• There are also fanless DC to DC power supplies that operate like those in laptops, using an external power brick to supply DC power, which is then converted to appropriate voltages and regulated for use by the computer.^[23] These power supplies usually have lower wattage ratings.

The electrical coils in power supplies can produce noise which can become noticeable in a quiet PC.

[edit] Motherboards

Many modern motherboard chipsets have hot northbridges (notably nForce4), which may come with active cooling, usually a small, noisy fan. Fanless heatsinks, such as the Zalman ZM-NB47J, ZM-NBF47 or the Thermalright HR-05, may be used to eliminate a noisy chipset fan.^[24][25] Some motherboard manufacturers have got rid of these fans by incorporating large heatsinks or heatpipe coolers, however they still require good case airflow to remove heat. Also, motherboard voltage regulators often have heatsinks and may need airflow to ensure adequate cooling.

Motherboards can also produce coil noise.

Undervolting and underclocking generally require motherboard support.

Some motherboards can control the fan speed using software like speedfan. Most recent motherboards have built in PWM based fan control for one or two fans.

[edit] CPUs

The heat output of a CPU can vary according to its brand and model - to be exact, its TDP. Intel's third revision Pentium 4, using the "Prescott" core, was infamous for being one of the hottest-running CPUs on the market. By comparison, AMD's Athlon series and the new Intel Core 2 perform better at lower clock speeds, and thus produce less heat.

Modern CPUs often incorporate energy saving systems, such as Cool'n'Quiet, LongHaul, and EIST. These reduce the CPU clock speed and core voltage when the processor is idle, thus reducing heat. The heat produced by CPUs can be further reduced by undervolting, underclocking or both.

Most modern mainstream and value CPUs are made with a lower TDP to reduce heat, noise, and power consumption. Most of Intel's desktop Core 2 Duo processors have 65W TDPs, and AMD has newer processors with a TDP between 35W and 65W.

[edit] Modern low power CPUs

Maximum TDP:

• Athlon 64 X2: 45W, 65W, 85W
• Intel Core and Core 2 series: 65W, 85W
• Intel Pentium M and Celeron M (lacks SpeedStep)
• VIA C7: 12W-20W (Fanless)
• transmeta processors
• Geode (processor): 5W, 25W
• Intel Atom: 2W, 4W, 8W
• Loongson: 1W, 5W, 7W (Fanless)

[edit] Video cards

Video cards can produce a significant amount of heat. A fast GPU may be the largest power consumer in a computer. For instance, 161 watts peak power consumption for an ATI Radeon HD 2900 XT 512^[26]. Because of space limitations, video card coolers often use small fans run at high speed, making them noisy.

Display options for making a quiet computer include:

• Use motherboard video output - typically low performance and low power
• Select a video card that does not use a fan
  • many of the more efficient GPUs are available in fanless models^[27]
  • many older video cards used little power, often not requiring heatsinks or fans
• Replace the GPU cooler with a larger heatsink^[25] and possibly a larger, slower fan
• No video card - use a terminal, thin client, USB display or desktop sharing software if display required

[edit] Secondary storage

[edit] Hard drives

Previously, hard drives used ball bearing motors, but they got noisy when the rotational speed of the drive was increased to 5400 RPM or 7200 RPM. More recent desktop hard drives use fluid bearing motors. The first hard drive widely reputed to be quiet was the Seagate Barracuda ATA IV.^[28]

The smaller 2.5" form-factor hard drives generally vibrate less, are quieter, and use less power than the traditional 3.5" drives.^[28][29] On the other hand, they often have lower performance and less capacity, and cost more per gigabyte.

To minimize vibrations from a hard drive being transferred to, and amplified by, the case, hard drives can be mounted with soft rubber studs, suspended with elastics or placed on soft foam or Sorbothane. Hard disk enclosures can also help reduce drive noise. Care must be taken to ensure that the drive gets adequate cooling. Hard disk temperatures can often be monitored by SMART software.

[edit] Solid-state storage

[edit] Flash memory

[edit] Solid-state drive

Solid-state drive (SSD) storage offers faster seek times, lower power consumption, no moving parts; making it theoretically more reliable and silent. There is scope for very high capacity drives; however, they are currently extremely expensive per GB and are fairly scarce.

[edit] Compact Flash cards

A few people use Compact Flash cards (or "CF cards" for short) for storage. Because they use IDE protocol, a simple adapter is all that is needed to connect CF cards to function as an IDE or PC Card hard disk. CF cards are also small, allowing SFF PCs to be made, produce no noise, use very little power (further reducing heat output in the AC/DC conversion in the PSU), and an insignificant amount of heat. However, they are very expensive per GB and are only available in small capacities. There are also issues regarding the maximum number of writes to each sector; often specified as 100,000 write cycles. However, there are industrial grade cards which specify a higher number of erase cycles, and different file systems, or technologies such as Enhanced Write Filter^[30] can reduce the writes to the card. Also, CF cards will fail gradually, so it will be easy to notice before any significant amount of data is lost, unlike the possible immediate failure of HDDs. Due to their small capacities they are easy to back up entirely, and often have 10 year or even lifetime warranties.

Windows minimization projects such as Winimize (Windows 98, less than 20MB) and Linux projects such as Puppy Linux mean that running an OS in small capacity, cheap compact flash card is possible. Because they have many OS components removed they are less prone to viruses and other malware.

The sustained transfer rate of current CF cards is a maximum of around 25MB/s, compared to an average of around 70MB/s for modern hard drives. However, the speed of flash memory is increasing at a faster rate than that of hard drives, and they have minimal seek times compared to hard drives, which increases the speed of loading many small files, and makes the PC seem more responsive as most operations performed by the OS include small files. Due to the fast seek times CF cards also don't show the effects of file system fragmentation like hard drives do. Newer CF cards support faster transfer protocols like DMA. It is possible to use a compact flash card for storing only information that isn't changed very often - such as music, videos and binary executables, while storing the small config files and other frequently modified data on a small hard drive or i-RAM.

[edit] USB flash drives

Where a motherboard supports booting from USB drives, they can be used in a similar fashion to CF cards to run the OS. With some Linux distributions, it is not much harder than using a CF card. As they both use flash memory, they have the same advantages and disadvantages, however speed is limited by the USB bus.

[edit] Gigabyte i-RAM

The i-RAM is a solid-state disk which has four DIMM slots to allow regular PC RAM to be used like a disk. It is much faster than a hard disk, does not have the write cycle limitations of flash memory, however it requires power continuously in order to maintain its contents (from standby power or a battery when the system is off), uses more power than many laptop hard drives, has maximum capacity of 4 GiB, and is expensive.

[edit] Problems and solutions

All forms of affordable solid-state storage offer relatively small capacity. They can be used as main storage for tasks which do not use large amounts of data or large programs, such as web browsing or word processing. Larger files and programs can be stored on a secondary hard drive which is only accessed when needed. Keeping the OS, often accessed files, and smaller programs on a solid-state drive means that the hard drives can be powered down much of the time. Network-attached storage, or NAS, is another alternative, allowing loud hard drives to be stored remotely.

Small USB drives or CF cards can be used to make the process of network booting easier also.

[edit] Optical drives

Optical drives can be slowed down by software to quieten them, such as Nero drivespeed, or emulated by virtual drive programs such as Daemon Tools to eliminate their noise entirely. Notebook optical drives can be used, which tend to be quieter, however this may be because they tend to run slower (typically 24x CD speed, 8x DVD speed). Some DVD drives have a feature, commonly called Riplock, which reduces drive noise by slowing the drive during video playback.

[edit] Laptops

Laptop computers typically do not have power supply fans or video card fans, and they use smaller hard drives. They also use many lower power components. However, laptop CPU coolers are usually smaller, so may be noisier than their desktop counterparts. Limited space makes silencing laptops more difficult.

A few laptops do not use cooling fans, for instance the Dell Latitude X1^[31], Panasonic Toughbook W5^[32] and T5^[33], Fujitsu Lifebook P7120.^[34]. The OLPC XO-1 has no internal moving parts.

[edit] Monitors

CRT monitors can produce coil noise, as can the power brick for an LCD monitor. LCD monitors tend to produce the least noise (whine) when at full brightness.^[3] Reducing brightness using the video card does not introduce whine, but may reduce color accuracy.^[3] An LCD monitor with a separate "power brick" tucked out of the way will produce less noticeable noise than one with the power supply built into the screen housing.

[edit] Printers

Dot matrix and particularly daisy wheel printers were often noisy, and boxes or cabinets were sometimes used to reduce the noise.

[edit] References

[edit] External links

The Wikibook How To Assemble A Desktop PC has a page on the topic of Silencing

• SilentPCReview.com hundreds of thoroughly researched articles on various aspects of PC acoustics.
  • A good starting point on SPCR is...What is a "Silent" Computer?
  • Followed by Reference/Recommended and SPCR in a nutshell
• Open Directory Computers: Hardware: Systems: Quiet
• CPU Heatsink Comparison Database, AMD S462/S754/S939/AM2 Intel S478/S775 air-cooled
• Build a Silent PC air-cooled
• The Silent PC
• Quietpc.com - A good website for quiet PC components.