Archive: A Primer on Noise in Computing

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In the last few years, PC makers have resorted to all kinds of extreme techniques to cool increasingly hotter components.

  • Large, heavy copper heatsinks for CPUs that require special mounting and transportation techniques in order to avoid damage to the motherboard.
  • Extremely noisy, high-speed fans on CPUs, video card heatsinks, and multiple high-speed fans for case cooling.

    What price cooling? Massive CPU cooler with 80 cfm fan rated for 53 dBA/1meter noise!

  • Intel now mandates an intake opening on the case cover near the CPU for additional cooling air, which opens another direct escape path for noise.
  • Water cooling - a pump circulates water through a closed loop in order to carry the heat from the CPU and other hot component parts to a radiator, often located outside the PC case and cooled by forced air with 2 or more 80~120mm fans.

    Watercooled system by Koolance uses 3 top mounted fans: A direct sound path to the PC user's ears.

  • Complex heatsinks integrating heat pipes to wick heat away from the CPU to another point in the case where it can be dissipated more efficiently; it is a kind of passively pumped water-cooling system, but requires customization.
  • Refrigeration technology, the ultimate liquid cooling. Complete with compressor pump, copper piping, Freon-substitute, etc.

Is it a fridge? An air conditioner? No, it's a computer!

The above cooling solutions add considerable expense, complexity, maintenance and noise. Some are so extreme as to be acceptable only for the fanatical or for highly specialized applications. All for the sake of increased clock speeds. One can't help ask: Is maximum clock speed a necessity for all computers?

The answer is no. Maximum clock speed is not a primary requirement for the vast majority of today's PC applications. Increasingly, the compelling requirements of a PC include:

  • Application performance
  • Ergonomic compatibility: access, operation, maintenance, noise
  • Aesthetics and physical design: size, shape, look and fit
  • Low total cost of ownership

Maximum clock speed is not a prerequisite for any of the above. In fact, maximum clock speed makes it more difficult to reach most of the above requirements.

Individual system builders and buyers of custom-built computers can take a different approach. A computer that performs well for your applications and needs makes a lot more sense than one that's been built for some idealized "everyman" consumer imagined by the industry.


The complexities of noise measurements and the importance of noise as a fundamental health, productivity and lifestyle issue leads us to the question of noise emission declaration standards. That is to say, how PC and PC component noise should be measured, and how that noise information should be reported.

  • Except for hard drive makers, noise emission reporting practices in the industry are spotty and inconsistent.
  • Fan makers generally provide only 1-meter (no load) SPL measurements.
  • Among the few power supply makers who report noise, many incorrectly cite the SPL data provided by the makers of fans used in their products. Even when the fan data is accurate, this does not reflect the actual noise that the PSU emanates, because of close-proximity turbulence effects of the impedances around the fan.
  • Makers of mainboards, video cards and optical drives rarely provide noise data, despite the fact that they all make noise - mainboards and video cards due to embedded fans often used for cooling, and optical drives due to their intrinsic motor-driven, spinning nature.
  • Suppliers of cases often include fans, but never provide any noise information. The fans never emit the same level of noise as specified by the makers, as mounting in a case causes mechanical vibrations that usually result in higher levels of noise.

Sound power and bel are already utilized by an important sector of the PC industry, hard drive manufacturers. It is also the primary metric used in the most applicable standards for PC noise:

ISO 7779 specifies operating and installation conditions in an acoustical lab in order to have reproducible and repeatable values. The two noise metrics in ISO 7779 are the A-weighted sound power level and the A-weighted sound pressure level at specified locations.

ISO 9296 specifies the declaration of noise emissions from information technology products. ISO 9296 specifies reporting statistical maximum values of the A-weighted sound power levels based on measurements taken according to ISO 7779.

SPCR urges all participants in the PC industry to join together in making noise emission declaration a standard practice for all components and systems. Acoustics labs are available all over the world, and with enough demand and testing in batches, costs can be made modest. The broader goal is the creation of a saner, healthier, more productive computing world.

This standard noise emission practice could be extended into all industries so that all human-made products bear the same noise labeling, allowing consumers to make intelligent choices based on apples-to-apples comparisons. In a related and perhaps more difficult challenge, I personally urge the industry to develop an acoustics metrology that integrates a qualitative yet objective appraisal of the noise emission.


Ever-increasing noise seems an inescapable byproduct of the machines, the technologies and the infrastructure support mechanisms we employ in our work and leisure time. As computers in their various forms become more pervasive in everyone's lives, they add increasingly to the universal din.

PC devices don't have to create the high noise levels they do and further contribute to the noise problem. Rather than employ noise reduction solutions after the fact, the best methodology is to use and end encourage the development of computer components that are quiet from the beginning of the design cycle - for both cost and environmental reasons. VIA's high efficiency C3 processor and Mini-ITX platform, AMD's speed/voltage adjusting Athlon 64 CPU, and Intel's high efficiency Pentium M processor are all positive recent movements towards this more enlightened direction.

Increased consumer awareness, education by institutions such as the World Health Organization, and the work of advocates (including Silent PC Review) is beginning to force manufacturers to address noise emission levels. Companies that wish to market effectively to noise sensitive environments, schools, offices and living rooms will be forced to reduce the noise of their products.

Hard drive manufacturers have provided useful noise data as part of their product specifications for some time, and the competition amongst them have helped lower the general noise level of hard drives. Cooling fans arguably create the most unnecessary system noise.

To create a level playing field for comparing products, that adherence to a standardized noise measurement system is imperative. As described earlier, Sound Pressure Level measured at 1 meter in dBA is a reasonable indicator of noise, but Sound Power (bel) measurements are more accurate and better correlate with human perception of noise. Qualified sound testing laboratories with anechoic chambers that provide the most suitable testing environments for sound measurements should be used to determine official results.

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