Silence your PC

Posted at: Friday 7th October 2005 by James Morris

A powerful PC doesn't necessarily have to sound like a jet engine. James Morris investigates how to make a high-end PC more acoustically demure

The sound level was recorded with the 01dB-Metravib's Symphonie sound and vibration measurement system (www.01db-metravib.com), and a 0.5in Bruel and Kjaer microphone and pre-amp were used to pick up the audio. These were positioned 50cm from the test PC to simulate the usual distance a person sits from their system. The test setup sampled frequencies between 80Hz and 20KHz over a ten-second period, and measurements were taken from both the front and side to determine the difference made by the person's orientation to the system.

Our test system was a standard high-speed gaming rig. We started off with a Jeantech Apollo JN8005 case, primarily because its mounts give you a choice of 80mm, 92mm or 120mm chassis fans. We then added an Asus P5WD2 Premium motherboard, as it's the current state-of-the-art model for an Intel-based PC. We then installed a 3.6GHz Pentium 4 560 with a standard Intel reference heatsink and 1GB of Kingston DDR2 memory.

Our chosen hard disk, meanwhile, was a 10,000rpm Western Digital Raptor. This is still one of the top choices for a performance PC but, with its high rotational speed, it isn't exactly whisper-quiet. Also, as this was a high-end gaming system, we added a generic Nvidia GeForce 6800 Ultra card , using the stock cooler. The 7800 GTX may have taken the honours as the pinnacle of single-card graphics performance, but there will be many recently purchased PCs with either a 6800 Ultra or the ATi equivalent, and their two-slot coolers will be screaming out to be replaced.

Once we had assembled our basic PC and recorded the noise level from the front and side, both with and without hard disk activity, we then removed and added some of our chosen upgrades to see what effect each part had. Finally, all of the most effective components were then installed simultaneously to show how much the overall din could be reduced. You can see a breakdown of our results on p109.

Fantastic

One rule of thumb concerning quietening your PC is that smaller fans have to spin faster to produce the same amount of airflow as larger ones. There are two factors to bear in mind here. The first is that you can cut down on the noise simply by reducing the fan speed with a fan controller. These cost as little as £7 for a Zalman FanMate from www.kustompcs.co.uk, and are certainly worth the investment, as long as your fans spin fast enough to keep your PC cool.

The second factor to bear in mind is that you'll get more airflow from a larger fan, which means you can spin it at a slower speed, making your PC even quieter, while still keeping everything cool. Basically, slower revs produce less noise at a lower, less irritating frequency. In simple terms, the bigger the fan, the better it will be for keeping noise levels low.

For this reason, you need to ensure that your case uses 120mm rather than 92mm or 80mm fans, and then fit fans with quiet bearings. For the first base PC test, we replaced the stock 120mm fans on our Jeantech chassis with two standard 80mm units, which may look inconspicuous, but aren't particularly quiet. Using standard sleeve bearings, they're rated at 27.85dBA at 2,500rpm, and generate 32.4cfm (cubic feet per metre) of airflow.