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Well, the intention of this Wiki page is to create a guide on how to build a quiet PC (or quieten down a noisy PC), and provide tips on what components to use (budget and super-silent), etc.

Introduction

With many computers nowadays being used in places where excessive noise is considered unacceptable (such as HTPCs or in peoples' bedrooms), quiet PCs are getting more and more popular. However, how do we quieten down our PCs?

Some might say 'Air cooling is for Volkswagen Beetles, watercool it', but whilst the CPU and video card might be the biggest heat generators, there are other components in a PC which may also generate noise.

What is noise, though? I guess it's a case of 'know your enemy' :) Noise is defined in the Compact Oxford English Dictionary as:

Noun 1: A sound, especially one that is loud, unpleasant, or disturbing, 2 Continuous or repeated loud, confused sounds.

The first definition applies best in our case, loud, unpleasant, unwanted sound. Sound is defined as:

Noun 1: Vibrations which travel through the air or another medium and are sensed by the ear, 2 A thing that can be heard.

Essentially, sound is caused by vibrations, hence to eliminate unwanted sound, we must track down and eliminate unwanted vibrations. These may come from anything with moving parts, particularly fans, although there are other sources as well. The vibrations may be transferred to another, larger object (such as parts of the case), which in turn vibrates, amplifying the noise.

Hence, to eliminate much noise, we must eliminate, or at least isolate, these vibrations.

The sources of noise in a PC

While most people think of fans being the only source of noise in a computer, there are other important ones. Below is a list of the main noise contributers.

Case fan(s)
CPU fan(s)
graphics card fan(s)
PSU fan(s)
Motherboard chipset fan(s)
Hard drive vibrations
Inductor / capacitor buzz

There is little that can be done about inductor/capacitor noise (typically high pitch buzz), other than replace the offending part (psu, motherboard, sometimes graphics card). In some cases it is possible to add some resister load on power supply (if thats whats doing it), for example some Seasonic PSUs have been buzz at low loads. But for fans noise and hard drive vibrations, lots can be done to reduce noise to (near) inaudible levels.

Fans

As many people will have noticed, fans are a major source of noise in a system, but with computers getting more and more powerful, and running hotter (until recently), are lots of fans a necessary evil in order to keep a system cool?

To eliminate fan noise, we have three options:

Replace fans with lower-speed, lower noise fans
Reduce the voltage going to the fans
Decouple fans from case chassis.

Fan models

There are many brands of fans to buy, each with different noise (dBA) and air flow (CFM). Generally noisier fans move more air, and quieter fans less. Its a trade off. Buying large fans (say 120mm instead of 80mm) allows more airflow compared to smaller size fan at same noise level, of course your case has have mounts for the large size fan. Also using two fans will double the airflow for a very small increase in noise compared to one fan (so for example 2 low speed 92mm fans can be quieter than a single 120mm fan for same airflow). Unfortunately a lot of brands tend to 'fudge' their ratings (CFM higher than actual, noise ratings lower than actual), SilenX being the most notable. SilentPCReview is about the only source that has airflow measurements, allowing accurate comparison of fans. The tables below list data based on those measurements, rather than manufacturer specified. In addition, the actual quietness of a fan has a subjectiveness to it that raw dBA ratings don't show. For example a buzzy, clicky or whiney fan will be a lot more irritating than one that makes a smooth 'woosh', yet both might measure the same loudness by a sound level meter.

Recommended 80mm Fans

Manufacturer	Model / Link	Bearing type	CFM 12V	CFM 9V	CFM 7V	CFM 5V	dBA 12V	dBA 9V	dBA 7V	dBA 5V	noise character	Review	Price
Nexus	Real Silent 80mm	Sleave	22	14	10	5	20	19	<18	<18	Very smooth	SPCR	$19
Panaflo	FBA08A12L (80mm low speed)	Hydrowave	30	21	15	8	24	19	<18	<18	smooth	SPCR	$19

Recommended 92mm Fans

(waiting for SPCR to review some)

Recommended 120mm Fans

Manufacturer	Model / Link	Bearing type	CFM 12V	CFM 9V	CFM 7V	CFM 5V	dBA 12V	dBA 9V	dBA 7V	dBA 5V	noise character	Review	Price
Nexus	Real Silent 120mm	Sleave	47	35	27	16	22	19	<19	<19	Very smooth	SPCR	$29
Scythe	S-Flex 120mm 800rpm	Fluid Dynamic	32	23	14	NA	20	<19	<19	NA	Very smooth	SPCR	$30

Methods to quiet existing fans

Reducing voltage going into fans (Undervolting)

Most fans, except the low speed Nexus and Scythe fans, are too loud at the default fan voltage of 12V. The main technique to quieten them is to lower the voltage, so they spin slower (reducing bearing noise) and move less air (lowering air turbulence noise). The table of recommended fans gives an idea of the tradeoff of noise verses airflow, however with a well designed system the trade off is minimal - computer becomes a lot quieter even inaudible but for small increases in system temperatures.

The main two techniques for undervolting fans are using a fan controller, or the '7V' or '5V' molex tricks. The fan controller is a bit more expensive, but allows precise control over fan speed, simply plug the fan in and adjust the knobs until the fans are silent. Alternatively if the motherboard supports has fan headers that fan control, the speed can be adjusted in the bios or software such as SpeedFan. The molex trick is cheaper, but only two options are possible - 7V and 5V. These are done by rewiring the power connector the fan plugs into. 7V is achieved by putting the fan between the 12V and 5V rails (12-5 = 7). 5V is achieved by running the fan off the 5V rail instead of 12V rail. One thing to be careful about is if your rewiring molex connectors (in particular the way shown in techpowerup guide below), don't plug in any other non fan devices after the fans, or you could damage your power supply when shorting 5V or 12V to ground. Guides to do this include: OcForums [TechPowerUp http://www.techpowerup.com/articles/other/137]

For the techpowerup method of using an extended, the 7V or 5V mod only needs to be done once, and then the rest of the fans can cascade off that and will all receive the same voltage, again make sure NO non fan devices are plugged in after it. Another way to quieten fans is to insert a resister in series with the fan, which can also be used to slow down a cpu fan if the motherboard doesn't have fan speed control. OCAU has a guide to this method.

Decouple fan from chassis

As well as air flow (turbulence) and bearing noise, fans also produce vibrations. On there own these do basically nothing noise wise, but when hard mounted (ie screwed in to the case with metal screws) these vibrations are transmitted into the case. The science concepts of forced vibrations and resonance come into play here (with the case amplifying these transmitted vibrations, and even worse resonating in some cases), the important thing to note is decoupling the vibrations with a material such as silicone, these fan vibrations won't add to the noise of the computer. One way to decouple is to use silicone washers, for example: http://www.pccasegear.com.au/prod882.htm

Another (probably more effective) way encase the whole fan side in silicone, for example: http://www.coolpc.com.au/catalog/product_info.php?cPath=127_38&products_id=517

Hard Drives

Hard drives are an often overlooked source of noise in a computer. Rotating at typically 7200rpm, they create lots of vibrations which resonate when mounted in the typical way - Screwed in tight to a metal case with metal screws. The metal case then amplifies the noise through forced vibration and resonance, making the hard drive noise a lot louder than when its loose outside the case. The solution is soft mounting techniques to reduce even stop vibrations being transmitted to the case. The main methods are listed below

Rubber Grommets

Rubber grommets are featured in most Antec cases, and allow the hard drive to be securely mounted but onto rubber instead of metal. Vibration noise is reduced a fair bit, sometimes considerably. The down side is the case has to be pre-designed to have them usually, such as the Antec P150 or P180.

Suspended in elastic

This is the ultimate silencers tool is to suspended the hard drives in elastic, eliminating vibration noise altogether. Instead of mounting the hard drive in the usual 3.5 inch bay, its mounted in a 5 1/4 inch bay with the cd drives. Generally a low speed fan is recommended to cool the drive(s) with a fan since it is no longer getting the 'heatsink' effect of being hard mounted to metal. SPCR has a good guide to doing this.

Notebook hard drives

Another way to get a quieter PC is to use a notebook hard drive instead. The reason is they spin at a slower speed, so vibrations are a bit less, but more impotently at a lower frequency (our hearing is less sensitive to lower frequencies), so is less noticeable. For HTPC use, hard drive performance isn't critical. Additionally, a notebook hard drive can easily be suspended in a standard hard drive bay, whereas typically a normal size drive has to be suspended in the less appalling cdrom bays.

Power Supplies

There are a number of factors that can contribute to the noise performance of a power supply.

PSU Efficiency

One of the factors of how much heat and noise a PSU puts out is its efficiency - how much of the power the system draws is used for the system, and how much is wasted (for example, as heat). A high-efficiency PSU (usually over 80%) will mean that less energy is lost as heat, thereby needing a lower speed fan to cool the PSU down.

PSU Fan Speed

Like with system fans, a reduction in PSU fan noise will produce a noticible reduction in total noise. Many power supplies will vary PSU fan speed depending on the temperature of the PSU, and others will enable the fan speed to be manually controlled, so you can set a suitable fan speed. Some have taken to replacing the fan in their PSU with a quieter one, although we would say to take care, the inside of power supplies is dangerous stuff, so take all precautions, and for Pete's sake, unplug it first! Maybe leave it for a while, too, gotta be sure the large capacitors in it don't have any charge in them.

Motherboard Chipsets

A large number of motherboards these days (typically cheaper and power hungry nvidia chipset based boards) are equipped with an active (with a fan) cooler for their chipset. These are often noisy, and are prone to failure. However, replacement with passive alternatives may be difficult, especially in motherboards where the chipset is near graphics card slots (like many nForce 4 boards), interfering with video cards. However passive heatpipe based cooling solutions in motherboards are becoming more popular, so its definitely worth paying a bit extra to get a motherboard with these

Graphics Cards

Likewise with CPUs, motherboards, and power supplies, many modern graphics cards are often equipped with a small, high-speed fan, which often generates a lot of noise. Low end cards are particularly notorious, compensate for having a smaller (and cheaper) sized heatsink by running the tiny cheap fan at a high speed even while doing 2d work. High end cards can also be rather noisy due to their high power consumption, while some are not so bad. loud video cards can often be silenced with aftermarket cooling from companies such as Artic Cooling, Thermalright, Zalman etc.

Footnotes

I know this guide is very much a draft, but hopefully once it gets going, more information will be added, and the page layout will be tidied up :)

-- Page started by Deanodriver, and expanded by --Snoop-wiggles, last updated 29th December 2006, 02:17 AEDT

Quiet PC

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