This Linux Box Is too Loud!
Step 1. Figure Out What You Really Need
The first rule of Linux box quieting is there's a balance between silence, coolness and power. Servers aren't noisy to impress customers; they're noisy because they're designed to stay cool even if some fans fail, so they have more and bigger fans than they need.
Outside the server room, though, silence is golden.
When starting this article, the home office where the victim PC lives measured about 41 dBA with the computer off and 49 dBA with the computer on. The goal is to get the box quiet enough that it's not noticeable in its normal environment. A system for a factory floor or a recording studio would be handled differently.
Step 2. Learn to Measure Your Results
Because you'll be changing the balance of power, cooling and sound, you need to measure all three. A general rule that applies to both management and hacking is, "Don't change anything unless you know how to measure the effect of the change." Therefore, let's get the measurement tools down before we start changing stuff.
Power is up to you. Use your favorite benchmark. If your Intel-inside system suddenly drops to half speed, the processor is trying desperately not to fry itself, and you need to cool it down again.
Cooling is an area where the PC hardware manufacturers thoughtfully help you out with temperature sensors on the critical components. Get lm_sensors working to keep an eye on your processor temperature, and use smartmontools to log the temperature of your hard drive or drives. Helpful LJ articles on both are in Resources for your convenience. As you make quieting improvements, check to make sure the temperatures don't go out of spec. If you weren't sure that your system was cool enough to start with, you can look up the specs on the processor vendor's and hard drive vendor's Web sites.
For measuring the noise level, get a small sound pressure level (SPL) meter, such as the Check Mate CM-100 from Galaxy Audio.
Step 3. Cheat by Moving the System
The noise that reaches your ear is what counts. If you're silencing your Linux box purely for the hack value, skip this section. Otherwise, remember that moving the system is allowed. Put the noisy box on the other side of the desk or even in another room.
In most cases, every device that you want to touch--the mouse, keyboard, CD burner, scanner and any other input device--is available in a USB version. That's good news, because it means you need to run only one VGA cable per monitor, plus one USB cable, from the system unit to your work area. Put one USB hub in your work area and a second USB hub somewhere in between if you need to go more than five meters.
If you're an IBM Model M keyboard aficionado or otherwise attached to one particular PS/2 keyboard and pointing device, use a pair of PS/2 extension cables, which are inexpensive. Alternatively, invest in one of the USB adapters that make your old-school keyboard and mouse show up as a standard USB keyboard and mouse.
Putting the box in another room involves cutting a hole in the wall that looks like it's supposed to be there. You'll need a drill, a jab saw, two low-voltage rings, two junction box covers, and--very important--a vacuum cleaner for the drywall dust. Do a neat job and practice saying, "I don't know, it was like that when I got here", just in case. If your Linux box ends up in someone else's office, though, you'll have to explain it. Just say it's "for security".
Step 4. Listen for Loud Parts and Make Improvements
In most cases, the four loud parts to deal with are the processor fan, the power supply, the hard drive or drives and miscellaneous fans.
The processor fan accounts for a surprising amount of the noise from the system, because it's coupled to a resonating surface, the motherboard. Replace the fan and heat sink with a high quality cooling unit that has a lot of surface area. We used a Zalman CNPS7000A-Cu, which is specific to the Intel Pentium 4 processor. Zalman's coolers come with a speed control knob, so you can adjust the fan speed to meet your processor temperature goal.
Zalman recently introduced a new cooler in which the fan is attached to the case, not the motherboard. We'll try that when we get a hold of one, as we expect that not making the motherboard resonate will be a big win.
The second loud part to deal with is the power supply. Zalman comes to the rescue again, with the ZM400B-APS. It has a thermostat, which is a "why doesn't everyone do this" feature. If the system heats up too much, the power supply fan speeds up to compensate--no knob tweaking here.
Seagate Barracuda drives receive good recommendations in quiet PC circles, and this one doesn't disappoint. Because we thought ahead and already had one in the test system, we don't have before and after numbers.
As home office system is a run-of-the-mill PC, we're able to get by without extra case fans by positioning the hard drive in a good spot and keeping an eye on it with smartmontools.
Finally, we make a pass through the system to look and feel for loose screws, cables that rub against things, loose case parts and other annoyances. Tighten everything up, remembering never to use a screwdriver on a thumbscrew that goes into a threaded aluminum part; it will strip before you think you're putting any torque on it at all. Fasten cables with Velcro, not cable ties, so they're easier to reposition if needed.
Step 5. Configure the System to Minimize Noisy Activity
We can get the hard drive to be quiet by putting the system into laptop mode, a new 2.6 kernel feature that minimizes disk activity. Although it originally was intended for laptops, any reduction in hard drive noise is good news for quiet desktops too.
Watch the September issue for an easy introduction to laptop mode.
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