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April 28, 2005 by Douglas Klassen
SPCR advises that the ideal way to achieve PC silence is to start with quiet components. What to do if you already have a PC with lots of expensive noisy components? Douglas Klassen faced this challenge and opted for an unusual solution: Build a case using pine boards and a design to contain the noise, with a little advice from SPCR forum members. His DIY project is nicely detailed here. Doug lives in Saskatoon, SK, and works for a small company involved in pro audio and acoustic consulting. He is currently looking into ways to silence his fridge.
- Mike Chin, Editor
I bought my current computer about two years ago. It's an Athlon XP 2100+ on an nForce2 motherboard with integrated graphics. The old one was a PII 266, to give you an idea of where I was coming from. The first time I turned the new one on my first thought was "Wow that's loud!" I then proceeded to ignore the noise for most of a year. Eventually, though, it started to drive me nuts, and I went on an initial round of quieting which brought the noise levels down to near those of the old PII. Unfortunately, replacing the PSU and the stock HSF unmasked an extremely annoying high pitched chattery hissing sound that came off the motherboard whenever the CPU was under load. In addition to the motherboard, the primary sources of noise were the Thermaltake PurePower 360 PSU, the Arctic Cooling Copper Silent 2 (non-TC, constant 2200 RPM) HSF, and the WD Caviar 80GB HDD.
Recently, I decided that the time had come to do something to bring the volume down further. However, the question of what to do was rather puzzling. Part way through my first round of silencing I'd discovered SPCR, and my reading of the resources here indicated that the ideal way to achieve silence is to start with quiet components, as case damping and the like tend not to attenuate noise levels as much as one would like. However, replacing all the noisy components in my case would have meant buying a whole new system, and the budget for that just wasn't there.
So, I adopted a different plan: Building a wooden case. Wood, I thought, should block much more sound than the thin sheetmetal of an ordinary case, and by designing from scratch, good ventilation could be achieved without giving sound any easy escape routes to my ears. This, I thought, should cut dramatically into the volume especially at high frequencies, which would mitigate the worst of the hard drive whine and motherboard coil hiss. With better airflow, I could slow down the CPU fan, and since my design called for a differently configured PSU anyway, I would upgrade to a Seasonic Super Tornado.
Here is a complete list of the components in the system:
CPU: AMD Athlon XP 2100+
HSF: Arctic Cooling Copper Silent 2, stock fan later replaced with Panaflo 80L
Motherboard: MSI K7N2G-L
HDD: 80GB Western Digital Caviar
GPU: Onboard Geforce MX
CD-RW: LG 52X (GCE-8520B)
DVD-R: LG 16X (GDR-8163B)
PSU: Thermaltake PurePower 360, later replaced by Seasonic Super Tornado 400
The design revolves around airflow. The intakes are situated in the bottom of the case, with the exhaust pushed out the back. The sides, front, and top are sealed up against noise leaking. To escape via the bottom intakes sound has to bounce off the carpet, which should absorb most of it. Sound escaping with the exhaust is traveling away from the user and less worrisome. The design also calls for separate airflow for the PSU, which necessitates it being placed at the bottom rear of the case. The exhaust for the rest of the case is provided by a single 120mm fan. This isn't really a revolutionary layout, but the options are fairly restricted if one wants all the I/O jacks at the back. Anyway, given its placement in the room, a case with a roughly conventional tower shape was desirable.
One issue that came up during the design phase of the project was the resonant nature of wood. A few experiments running fans on my desktop convinced me that this could be a significant problem, but one without any really definitive solution. The best option seemed to be to plan to isolate all moving parts from the case, using various sorts of foam and elastic to hold things in place.
The final feature of the design is an acoustic absorbing panel made from 1" compressed fiberglass to be fitted to the inside of the left side door. A panel of this sort effectively absorbs sound down to around 1000 Hz, and should help to muffle the high frequencies coming off the motherboard and hard drive. Even though the panel only covers one side of the interior, sound will have a tendency to bounce around inside the case until it encounters the panel, at which point it will be converted to heat. Or so the theory goes.
I decided to build the case out of pine boards, principally because I had already made a few pieces of furniture from pine, including the computer desk. To make things easier, I opted to cannibalize the motherboard tray and 5.25" drive rack from my old case.
The first few pieces tacked together.
Here we see the first few pieces tacked together in order to establish where the holes in the back needed to be cut. It was a bit tricky - the case needed to be partially assembled to accurately tell where the rear I/O port would be, but I needed to cut the holes before putting anything together.
Here the basics have been assembled - intake vents on the bottom, exhaust and I/O port on the back. The top hole in the front is for optical drives, and the bottom for a switch panel. The top half of the bottom hole also lines up with the bottom slot in drive rack, so it could someday house a fan controller or whatever. I used fairly simple joinery techniques, mostly butt joints, screwed and glued. Most of the strength comes from the glue; the screws act as clamps while the glue sets, but only contributes a bit to the strength of the joints. Where screws would be visible on the outside, I used cleats instead of screwing into the ends of the joints. You can see some cleats in the above picture at the top of the motherboard backing, ready to be fastened to the top of the case.
Primary assembly complete.
All that remained was to mount the doors, and that had to wait till the finish was applied. Note the feet holding the bottom up off the ground with long cutouts for unrestricted air intake. I wanted the side doors to close snugly, so I put in backing strips along the top and bottom of the opening, to which I later glued strips of felt.
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