A quiet, silent or fanless PC is a personal computer that makes very little or no noise. Common uses for quiet PCs include video editing, sound mixing and home theater PCs, but noise reduction techniques can also be used to greatly reduce the noise from servers. There is currently no standard definition for a "quiet PC", and the term is generally not used in a business context, but by individuals and the businesses catering to them. A proposed general definition is that the sound emitted by such PCs should not exceed 30 dBA, but 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 a smooth frequency spectrum (lacking audible tonal peaks), and little temporal variation are less likely to be noticed. The character and amount of other noise in the environment also affects how much sound will be noticed or masked, so a computer may be quiet in relation to a particular environment or set of users.
History Energy Star, in 1992, and similar programs led to the widespread adoption of sleep mode among consumer electronics, and the TCO Certified program promoted lower energy consumption.
Causes of noise The main causes of PC noise are:
Vibration from disk drives Air vortex effects from fan blade edges Electrical whine: noise generated by electrical coils or transformers used in power supplies, motherboards, video cards or LCD monitors.
Measuring noise Though standards do exist for measuring and reporting sound power output by such things as computer components, they are often ignored. 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, but even then, an average sound pressure level is only one factor in determining which components will be perceived as quieter.
Noise reduction methods
Common noise reduction methods Use large, efficient heat sinks Incorporate heat pipes, which have much higher effective thermal conductivity than solid copper Use fans with lower speeds and larger diameters Use fans with low bearing and motor noise Rather than constant-speed fans, use thermostatically controlled variable-speed fans that run at less than maximum speed, and thus run quieter most of the time Use an efficient power supply to minimize waste heat Use quieter models of hard drive Use solid state devices like compact flash or solid-state drives rather than traditional mechanical hard drives Use remote networked via SMB or NFS rather than local disks Place a damping material such as Sorbothane around hard drives or other spinning items Use sound insulation material to absorb sound and dampen case resonance Water cooling, although difficult to set up, may be useful in some situations
Low-cost methods A number of methods exist for reducing computer noise at little or no added cost.
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