Action Plan

If it is not obvious where a noise is coming from, you could adopt the following procedure. Remove the side of a tower case or the lid of a desktop case. Using a pencil with a rubber on the end, momentarily stop the blades of a fan with the rubber. If the noise ceases or is reduced, that is the noisy fan. The fans to consider are in the PSU, on the CPU cooler and attached to the northbridge and VGA cards. Do not do this unless you are happy and competant to undertake work of this nature.

But, be aware. Once you eliminate the noisiest fan, the next noisiest fan will become apparent.

REMEMBER - always try to eliminate a noise first, then try to reduce it, then, finally, muffle it. And consider a silent, passive cooling device, providing it is adequate, before fitting a noisy, active device. And as a passive device has no moving parts, it can never make a noise, never fail nor wear out.

Please read the DISCLAIMER at the end of this section.

Fans. For every inlet fan fit a similar exhaust fan. In this way, each fan assists the other to improve airflow and fan life. The ideal situation is to have a slight positive pressure in the case. Don't forget that your power supply, the PSU, will have an exhaust fan built in, so this will need to be taken into account. The case inlet fan is normally located at the bottom front and the case exhaust fan at the top rear, either above or below the PSU.

Hot air rises so don't compete with the natural airflow.

Always fit some form of filter to an inlet fan as internal dust, fluff and dead bugs can reduce cooling efficiency and could cause electrical fires. Fit fans internally.

The standard case fan is 80 x 80 x 25 mm and most case manufacturers provide mountings for them. If you can fit a 92 mm fan, it can run more slowly for the same airflow, so it should be quieter. The same goes even more so for a 120 mm fan (raise your case off the floor and fit this size of fan in the base). Fit fans, of a particular size and of sufficient quality to have an inherently low noise level, preferably below 20 dBA at the required airflow. Otherwise fit larger fans and slow them down.

Temperature Control. To slow a fan down you can either fit a fan with a thermistor built in or use the Thermistor Kit with a standard fan.

Reduced Voltage. Fit the electronic Fan Mate to give manual control of the voltage. An alternative means of slowing the fan down is to fit a 5 or 7 volt Converter Cable (available with a sensor lead) or Zalman's Noiseless Connectors.

Interior. The air must find its way through your case and out through the exhaust fan(s). So the less obstructions en route the better. The major improvement here is to fit Round IDE and Floppy Cables instead of the flat, ribbon type as supplied. Tie Wrap cables neatly. Do not locate any items close to a fan, particularly on the inlet side.

Fan Aperture. Most case fan mounting areas are severely throttled with the pressed metal pattern, which can dramatically restrict airflow. This not only reduces fan performance and fan life but also increases noise. Remove all the metal from the aperture so that the fan operates through an unrestricted hole. Trim the sharp edge with black or white Edging Strip. For safety reasons, you may need to fit a thin wire grille Fan Guard.

Fan Mounting. Mechanical noise can be reduced by flexibly mounting the fan to the case. Either fit our Flexinuts, which require no plain washers, lock washers or nuts, or consider the special Papst flexible Fan Mounts or AcoustiFan Gel Mounts.

Fan Location. Noise is worse if the source is in line of site. So locate your case out of sight, by the side of your desk or round the corner. Worth a noticeable 3 dBA drop in the noise level. Noise varies with distance as an inverse square law. So if you double the distance to the noise source, it will seem one quarter as loud.

CPU Cooler. The biggest problem is with the noise of the fan. They are small, usually 60 x 60 x 10/12/15 mm or 70mm, and to keep costs down, a cheap fan may be used and this will tend to be noisy for a given airflow. The solution is either to fit a better quality fan of the same size, maybe deeper, or to fit a larger fan with a Fan Adapter. The Fan Adapter, which has built in flexible fan mounts, allows an 80 mm fan to be fitted on 60 mm mountings giving the same, or even improved airflow than the smaller fan, but at a lower speed and noise level. See above for the options to reduce the fan speed. A second option would be to fit a totally new, inherently quieter, heatsink fan unit.

Thermal Compounds. The heat sink should always be fitted to the processor using a thermal interface material (TIM) such as Arctic Silver 5, Ceramique or Arctic Alumina. This ensures the maximum heat transfer between the processor and the heat sink and therefore the best cooling performance. We suggest that you do not consider thermal tapes or unbranded, so called, thermal grease.

Video Card. An AGP video card can run very hot, particularly at serious gaming speeds. Passive heatsinks are available to fit to the card. Consider Zalman's standard passive product or the latest passive heat pipe units. Arctic-Cooling offer the VGA Silencer.

PCI Slot Cooler. Another option, to reduce local temperatures around the VGA and PCI cards, is to fit a PCI Slot Cooler. The slot cooler is quiet and can move around 40 cfm of air. High temperature components should always be located close to air outlets. This cooler will double as an exhaust fan.

Hard Drives. As hard drives get faster, they get hotter. A slow unit may use 10 watts, but a high speed SCSI drive may rise to 40 watts. Two types of Passive Heatsink are available together with a Zalman passive heatpipe cooler. For active cooling, either fit an Internal Cooler with a single fan, that screws to the hard drive casing or fit a front mounted Bay Cooler into a spare 5.25" bay. The former uses internal case air and recirculates it but the bay cooler introduces cooler, ambient air from outside the case.

If you are using Raid and need space for extra hard drives, our Hard Drive Carrier and Cooler will take three hard drives and fit into two 5.25" bays. It has a removeable filter behind a drop down flap at the front. Cooling is provided by a single 80 mm fan.

PSU. The standard ATX power supply probably provides the main or only air exhaust from the case. At its simplest, air is drawn through grilles and slots into the body of the PSU and out through an exhaust fan.The more sophisticated units have a second fan located in the base of the PSU and even a single large 120 mm fan in the base, adjacent to the processor. In quality units, these fans have sophisticated progressive thermal speed control.

Always consider fitting a high quality PSU. The temperature controlled fans responds to demand, so reducing the noise level at idle. You might consider a higher rated PSU than you need, on the principle that with reduced demand it will run cooler and thus quieter. However at lower output it is running less efficiently so a greater proportion of the power used is being rejected as waste heat. A 120 mm fanned PSU may supply all the case airflow a medium power system may require. However, if you fit a quiet exhaust fan below the PSU, it will reduce the waste heat flow through the PSU, so the latter will run more slowly and therefore quieter.

Processor. The hottest item in the case is usually the processor. It can theoretically reach 90 degC and reject upwards of 80 watts of heat at full speed. The coldest air that can cool it is outside the case - ambient air. So why not consider ducting air from outside the case, directly onto the processor heat sink, rather than using the warm internal case air? The ideal path would be a straight line from the side of the case, mounting the fan in the middle.

There are also secondary advantages. By taking the fan off the motherboard, the latter will no longer be subjected to fan vibration, so reducing noise and extending its life. And this fan now doubles as an inlet fan so removing an inlet fan from the case. The range of Zalman flowers have their cooling fans isolated from the heatsink.

Sound Proof the Case. Your computer case is made of a thin material, probably sheet steel, which can be excited by various mechanical noises, such as fan and hard drive motors. It will also reflect internal airborne noises generated by turbulent air from the fans. To reduce these two types of noise, fit a bespoke, self adhesive sound proofing material to the inside of the case. The results can be quite dramatic. We recommend the newly introduced products from AcoustiProducts and innovatek's Soundproofing Professional Kits.

DISCLAIMER.

All advice is given in good faith and we cannot be held responsible for the specific actions of any individual or group. Any work you undertake is at your own risk. We are not responsible for any consequential loss or expense. We do not warrant any component as being fit for a specific purpose.

Whilst working on a computer, ensure that the mains power lead is disconnected from both the PSU, at the back of the case, and from the mains socket. Be aware of the dangers of static electricity. Do not undertake any work that you feel you are unqualified or incapable of handling.