Langa Letter: Cool and Quiet, Part III - InformationWeek

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Hardware & Infrastructure
09:33 PM
Fred Langa
Fred Langa

Langa Letter: Cool and Quiet, Part III

Fred Langa wraps up his exploration of the causes--and cures--of noisy PCs. His step-by-step process, including successes and failures, ensures you won't make mistakes as you work to make your PC cool and quiet.

In Cool and Quiet, Part One, we started with the basics of quieting a PC's noisy fans, and saw how PC noise reduction can actually be rather easy and cost just a few dollars. A high-quality, nearly silent PC fan can cost under $10, for example.

We continued our exploration in Cool and Quiet, Part Two and took a close look at some of the science of PC fan noise, including the odd fact that two slow-spinning fans can be quieter and yet provide more cooling than one fast-spinning fan. We also looked at the most common and effective PC noise-reducing technologies and hardware, including inexpensive, snap-in (no tools needed) add-on fan speed controllers that let you slow down--and quiet--almost any PC fan.

In fact, by the end of Part Two, we'd covered nine major elements of PC noise and its control:

  1. Most ongoing (nontransient) PC noise usually comes from the cooling fans.
  2. There are three main components to fan noise: air turbulence (a "whoosh"); tip noise (a whir or whine), and mechanical noise (clicks, grinds, rattles).
  3. The simplest way to reduce all fan noise is to reduce fan speed.
  4. Reducing fan speed also reduces airflow, which reduces cooling ability, a potential danger.
  5. You should monitor your PC's internal temperatures using a tool like the free MBM5 before, during and after any changes to your PC's cooling system.
  6. To maintain a safe and effective level of cooling with lower fan speeds, you'll need to do one or more of the following: increase the size of the fans; increase the number of fans; increase the size of heat sinks.
  7. It's counterintuitive, but increasing the number of fans in your system may reduce the total system noise: Replacing, say, a 30dB factory-installed fan with two 20dB fans will cut the noise by 7dB, but can still produce the same or greater air flow.
  8. You easily can attain truly "whisper quiet" operation (around 30dB or less) for all your PC's fans combined, using standard, inexpensive, off-the-shelf fans and components, good fans can be amazingly inexpensive.
  9. The simplest way to reduce a PC fan's speed is by reducing its voltage from the usual 12v to 5v. This can be done by directly connecting the fan to the PC's 5v power supply, or by stopping down the normal 12v via a resistor. And again, ready-made parts for this are easily available, and very inexpensive.

If you haven't done so already, please read Parts One and Two now, as they contain the full background and additional details on the above that make today's article--Part Three--make sense.

Five Changes
In this article, we'll wrap it all up: I'll show you exactly how I modified my system in five successful ways--and in one unsuccessful way. I'll also show you my final results both for sound and for temperature, even after running the system through a worst-case thermal stress test.

If you recall from Part One, my initial concern was with a clicking noise produced by my system's main case exhaust fan. The PC--a brand-new and well-made 3.2GHz P4--has thermal sensors and a fan-control system (in the BIOS) that can adjust the speed of the case fans according to need: When the system is working hard, the fans operate at full speed, with all the whooshing and whirring that's common to most PC fans. But when the system isn't working flat-out--which is most of the time--the BIOS intermittently cuts the power to the fans. By cutting and restoring the power to the fans several times a second, the fan spins more slowly, practically eliminating the whooshes and whirs of high-speed turbulent air flow. Nice.

Unfortunately, each time the power is restored to the fan, the fan assembly jumps just a bit, producing a small but audible click or tick. Like a pebble in one's shoe, this steady ticking, repeated several times a second all day long, eventually becomes quite irritating.

So, when I began looking at noise-reduction options for my PC, my initial goal was to eliminate these sharp ticking sounds, but without increasing the other fan noises beyond their already low levels.

Plus, as also described in Part One, I'd also discovered that the airflow in my PC's case largely bypassed the hard drive, which consequently ran warmer than I wanted, averaging about 20 degrees F/12 degrees C warmer than the air inside the system case. This was well within spec, but it seemed to me that there was no real reason for the drive to be more than a few degrees warmer than the rest of the case. (Needless extra heat would eventually shorten the life of the drive.) So, I also wanted my cooling solution to eliminate the dead-air spot near the hard drive and thus keep the hard-drive temperature closer to the system's internal air temperature.

Small Initial Missteps
Initially, my tinkering was personal and very casual--it wasn't part of a controlled experiment, and wasn't intended as a topic for publication. Nevertheless, I did take some standard precautions before doing anything: As always, I made a full backup (actually a software "image" of the hard drive) so no files were at risk. And I was monitoring the temperatures of the CPU, motherboard and hard drive via MBM5. I even had the software set up to trigger an automated orderly shutdown of my system if any temperatures got too high. So I wasn't worried about toasting my system or losing data.

But beyond that, my initial approach was very casual: I assumed the ticking noise was caused by a flaw in the fans themselves, so I went online and after a brief search, bought a pair of fans (both under $10) that claimed to operate at a quiet 20dB each. No, it wasn't a very scientific process--yet.

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