As musicians and home recordists, we often end up utilising a computer to handle various audio tasks, be it MIDI control, soft synths or even to run full-blown DAW (Digital Audio Workstation) software to record with. We often use sensitive microphones, and many a small studio consists of only one room. So the sound of a computer imitating a jet turbine is often unwelcome. Help is on hand however, as there are many replacement parts and simple modifications which can reduce the noise considerably - and not necessarily at a high price.

The problem

Unfortunately the focus for modern computers is on processing power, which has an unfortunate side effect - heat. The methods used to cool modern high powered machines are a combination of two things: heatsinks and fans. Heatsinks are made of either aluminium or copper, and carry the heat away from whatever is generating it to where it can be dissipated by air flow. Modern computers generate so much heat that fans must often be used to generate more airflow to help dissipate the heat from the heatsinks, and these can generate a lot of unwelcome noise.

The noise generated by fans comes from two different sources:

• Mechanical noise - Fans create most of their noise as mechanical vibration, which can be amplified by the computer case. Stock fans are usually not very well balanced, which causes more vibration. Small fans are hard to balance properly and added to that the noise they generate is higher pitched, often making them "whine".
• Turbulence - Air flow tends to create turbulence, which creates more noise (think of the sound of a strong wind and you'll get the idea). A smaller fan moving the same amount of air as a larger one will always have a more turbulent output flow.

There are other sources of noise in a computer, such as hard drive vibration, but the vast majority is generated by the fans themselves.

Solutions

In General
Swapping out existing fans with passive heatsinks or specially designed quiet fans makes a huge difference to noise levels for a relatively low amount of money. Where cooling is not as critical, a small heatsink and fan may sometimes be replaced by a larger heatsink with no fan attached, or a passive heatpipe cooler in some instances. Using a fan speed controller to run fans slower than their full speed can reduce levels enormously without affecting air flow too greatly. When possible, a larger fan running at a slower speed will be quieter than a smaller fan running at a high speed. When possible, multiple fans running slowly will move as much air (if not more) while being quieter than a single fan running at full speed.

Specific Examples:

Case Fans - Swap out for better quality fans designed to be quieter. My favorite brands here are Nexus and Vantec Stealth - while the Stealth is not as quiet as the Nexus, it is readily available and inexpensive. Some silent PC users prefer the ultra silent Papst or Panaflo fans, but I find these do not move enough air for adequate cooling. Running a case fan slower is best, if a lot of air needs to be moved for adequate cooling, multiple fans should be fitted. It is also possible to get silicone rubber mounts to replace the steel screws for mounting case fans, which help reduce the amount of fan noise transmitted to and amplified by the case.

Chipset Fan - The small heatsink and chipset fan on some motherboards can almost always be replaced with a better quality heatsink alone, getting rid of the small fan completely. Zalman make some effective and inexpensive chipset heatsinks.

PSU - Replacing the PSU (power supply) with one designed to run quietly is easiest and often best. A replacement PSU should be over rated - if you need a 300W supply get a 500W. This means the supply is never taxed and will rarely heat up much, so the built-in temperature controlled fan will usually run slowly and quietly. If you are on a budget, a generic PSU fan can be swapped for a high quality model, but this should only be done if you know what you are doing, as there is the ever present chance of electric shock.

Graphics Cards - Modern high powered graphics cards can run very hot and will sometimes have a small, very noisy fan fitted. A dedicated audio machine does not usually need a high powered graphics card, so a card with a heatsink is often good enough. If your audio computer doubles as a gaming computer and needs a fast graphics card, there are heatpipe based heatsinks which are very efficient. Zalman even do a range of heatsinks with "silent" fans for high end cards.

CPU Cooler - The CPU cooler is a critical item, without which the processor would soon burn out. Almost all CPU cooler designs utilise both a heatsink and a fan. Heatpipes are gaining in popularity for use as a cooler, but will usually use a fan too. For our purposes, replacing the cooler with a model that has a really efficient heatsink and a large, but relatively slow fan is best. The only thing to watch out for is the weight of a cooler - the more efficient coolers (especially those made with pure copper) will sometimes be very heavy. A heavy cooler is not a problem for a computer that is never moved, but may need to be removed before the machine is transported as any shock could damage the CPU or motherboard. Usually a combination of copper and aluminium gives the best weight/performance. My favorite models are the Zalman models, which meet all the requirements above, and usually come with a fan speed controller.

Hard Drives
Hard drives can also be a source of vibration, particularly the faster hard drives that spin extremely fast like 10,000 rpm SCSI drives. Some brands are quieter than others too. My usual choice for quieter hard drives are the Seagate Barracuda models, which are both quiet and high performance enough for the demands of a DAW. In addition to using a quieter hard drive, mounting the drives on rubber grommets can make a difference to vibration levels.

Air Flow
Ensuring that air has an unobstructed path to flow through the computer will cut down on air turbulence and noise. Simply using rounded cables instead of ribbon cables, as well as routing cables out of the way of air flow will make a difference. A big difference to turbulence can be made by cutting out the "honeycomb" fan grilles built into cases and PSUs and replacing with a rounded wire grille or leaving it completely open - although with the latter option you run the risk of occasionally getting your fingers hit by fan blades if you are not careful (I speak from experience).

Cases
Manufacturers are now making cases specially designed for quieter operation. Specifically, Antec have made it a point to build quieter cases for the last few years, and while at first, these cases were more expensive (such as the Sonata), the technology is filtering down into even the lower priced cases such as the SLK1650, and the future bodes well for quiet computing.

For the fanatical, Zalman has recently entered the market with a case which is entirely passively cooled (the entire case is a heatsink and it uses no fans at all!) and generates no noise whatsoever. Unfortunately this is an obscenely expensive solution, but once again the prices should come down, and hopefully the technology used will filter down to lower priced cases.

Anatomy of a Quiet Computer

The computer shown above uses a variety of cooling solutions to provide adequate cooling while remaining virtually inaudible Mind yer fingers! - The replacement PSU fan, with the grille removed

1. The graphics card utilises a Zalman heatpipe and heatsink which provides a large surface area to radiate the heat generated by the card. An added advantage of this heatsink is that it provides a large surface area on the rear of the card where the airflow from the CPU cooler and the case fan can effectively dissipate the heat. 2. The motherboard's chipset is cooled with a heatsink but no fan, which was one of the reasons this specific model of motherboard was chosen. 3. The case (Antec Sonata) came standard with a 120mm case fan, which was pretty good until the machine heated up and the fan sped up, then became relatively noisy. So the fan was replaced with a Nexus model which is run at a constant low speed. The grille behind the case fan has been removed to reduce air turbulence and the fan itself is attached to the case with the stock rubber mounts. 4. The CPU cooler is a large Zalman CNPS7000A-AlCu with a quiet 120mm fan. I have a P4 3GHz Northwood core processor, which produces far less heat over the more modern Prescott processor of the same speed, allowing me to run the fan at only 1500RPM. If you have a 3GHz+ Prescott you may have to run the fan faster or use the Copper version of this cooler to provide enough cooling at the low fan speeds of the "silent" mode. 5. The fan in the stock PSU was replaced with a Nexus model, the grille on the rear of the case was removed, and the air intake grille on the PSU (shown in the picture) was cut out. Also note: The cables are bundled together and run out of the way of the path of airflow going through the case. Rounded cables are used where possible for the same reason. The Antec Sonata case comes standard with removable hard drive bays and the hard drives are mounted on rubber grommets, which help reduce vibration. The case is fairly solid, which also helps reduce vibration. The CPU fan speed is controlled by a fan speed controller (not pictured). The case fan is run from the 5V rail from the power supply, instead of the normal 12V, which eliminates the need for a speed controller Cutting out PSU and case fan grilles effectively invalidates your warrantee on the case and PSU, so do this modification at your own risk. SAFETY - These modifications must also be done with all the electrical parts stripped from the case and the PSU case, to avoid the risk of metal fragments shorting out electrical components.