Silencing a noisy fan

A long time ago in a galaxy far, far away, I wrote a four-part series on how to silence noisy PC fans. The 4th article is here, and it has links to the three earlier parts which explain all the hows and whys of fan noise. There are three main factors:

First, there's the turbulent flow of the air itself--this is the white-noise "whoosh" normally produced by all fans. It's speed dependent: The faster the fan spins, the more energetic the turbulence, and the greater the airflow noise.

Second, the fan blades themselves also make noise as they slice through the air. Most of the noise actually comes from the tips of the blades, which are the fastest-moving part of the fan assembly. The faster the fan spins, the more noise the blade tips make.

Finally, there's the mechanical noise of the fan assembly itself. The motors and bearings in fans make at least a little noise, but cheap fans using needle or sleeve bearings make more noise than ball-bearing fans; and fans manufactured sloppily may suffer from vibration-inducing imbalances. All these noises get worse with speed: The faster the fan spins, the more mechanical noise it produces.

PC makers usually opt for the cheapest solutions for cooling: small, cheap, high-speed fans. As a result, many PCs sound like hair dryers.

They don't have to.

I won't repeat the stuff in the above article--- it's just a click away. But the bottom line is that replacing small, fast-spinning fans with larger, slow-spinning fans can make your PC literally whisper-quiet without sacrificing any cooling ability. In fact, your PC can end up quieter *and* cooler.

After December's ice storm ate my main PC's motherboard (despite its being connected to a UPS/surge suppressor), I decided it was time for a new one. The PC death was annoying, but I'd gotten four years of very hard use out of it (running nearly 24/7, with lots of hardware and software experiments and upgrades along the way). I really couldn't complain too much.

Plus, that PC was a home-built model, something I've been doing for quite a while now. Usually, when a PC needs replacement, parts of it are still fine. Buying a PC kit or a "bare bones" unit lets you reuse the still-good parts in the new machine, saving time and money.

For example, a few years ago I built a $500 1 terabyte "network storage device" for an article I was working on. At the time, the least expensive commercial models cost double that.

I still had the four lightly-used 250GB drives that had been the core of that project; I didn't need to buy a PC with yet another humongous drive. So buying a kit-built PC would let me spec the new machine without drives, enabling me to re-use the large drives I had on hand.

Kit-built and "bare bones" PCs are easily available (eg Tigerdirect.com) and inexpensive, and they've served me well over the years.

But this time, I screwed up. I cheaped out on the motherboard, getting one that the various reviews and user forums were split on: an nVidia 680i. The board could perform very well, but users complained about high "infant mortality" (yes, a real term used in the PC business for parts that arrive dead, or die soon after being put in service) and about noisy fans.

Well, the fans I could deal with, and I'd watch for early trouble and simply return the board for replacement if there was a problem.

The parts arrived and I spent a day deep in the geek zone, assembling and testing the new PC. It worked fine, except, as noted, the fans were awful.

I used the new box for a few days, figuring than any instances of infant mortality would happen then. Everything worked fine.

nVidia motherboards come with a very nice monitoring tool that lets you see (among other things) the temperatures of critical parts. I used this a lot, to get a sense of what "normal" temps were for this board with the OEM cooling in play.

Once the system seemed reliable, it was time to replace the offending fans. This tiny terror was the worst (click for larger images):



Despite the name (below) there was nothing magic about this piece of plastic crap. It spun at incredibly high speed and volume, generating a persistent mosquito-like whine.



Here it is (below) in its natural habitat, just to the left of the memory sticks.



Closer and flat-lit for detail:



It had to go.

I removed the fan and its tiny, cheap, stamped-steel heat sink:


It had gone easily, so far, so I figured "why not?" and also went after the other small fan on the motherboard, although it was neither as small nor as loud as the the little siren-like sucker I'd just pulled.

Say goodbye to this fan, too:



Out it came, followed by its heavy, die-cast heat sink:


In this motherboard design, the heatsinks are held in place with plastic spring-loaded prongs which fit through drilled openings in the motherboard itself. It's easier to work on with the motherboard removed from the case. Here's the naked motherboard with the the offending fans and heat sinks removed:


Heat sinks work by increasing the mass and surface area of a chip: The sinks absorbs heat from the chip and releases it to the fan-forced air circulating in the case.

Heat gets from the chip to the heat sink by simple conduction: the heat sink's base presses firmly against the top surface of the chip. The better the contact between the heat sink and the chip, the better the heat transfer.

"Thermal grease" is a compound that improved conduction by filling tiny imperfections in the surfaces of the heat sink and chip. I'd collected a bunch of small tubes of the stuff over the years. Replacement heat sinks usually come with a tube or two; and it's cheap anyway.

I did have one tube of high-quality stuff:


It's a tiny syringe filled with a nonhardening plastic compound that contains a high percentage of tiny silver shavings; silver is an outstanding heat conductor (even better than copper).


I think that tube cost me $10, and it's lasted literally for years. You don't need a lot; just a small dollop on the surfaces, which you then spread to a uniform thin coat.




Once the chips were greased up, I reattached the now-fanless heat sinks:


Next step was ensuring that the reinstalled heatsinks would get plenty of airflow, but from large, slow-spinning fans instead of the original screamers. Here are the small original fans (left) and the large replacement fans (right):


I also had those larger fans on hand from older projects, they were about $8 each when I bought them. Cheap! They spin slowly and very quietly, but move a *ton* of air.

I ganged the two fans together with zip ties:


And then used more zip ties to position the fans exactly where I wanted them:


I love working with zip ties: They're strong, cheap (maybe a penny each, in bulk), infinitely adjustable (so you can position things precisely where you want) and they're plastic to they don't conduct sound or vibration very much. Perfect for suspension-mounting fans!

With the fans on, a veritable hurricane was blowing inside the case, but the fans only made a gentle sustained whooooshing sound instead of the raucous whine of the original fans.

Once the system had booted, the first thing I did was fire up the nVidia system monitor, and was pleased to see that the chip temps were actually a bit lower than they'd been with the factory fans. Success!

I left the PC on its side with the case open and used a tool called Burn In to stress the CPU to its max, running the CPU flat out under full load for several hours--- way more than it would ever be likely to be pushed under real-life conditions. Everything ran perfectly. The CPU temp climbed a bit to 118F (47C) and stabilized there, nowhere near the max allowable temps of 149F/64C.

I placed the case upright, replaced the cover, and reran the tests: Essentially the same results, within a degree or two. I now had a much quieter, cool-running PC. I was good to go, with cooling to spare!

That evening, I set the PC to work overnight importing hundreds of gigs of files I've stored. I checked in on the PC from time to time, making sure all was well. With the new fans blowing a hurricane inside the case, and with the system not working very hard, all the temps inside the case were not much above room temperature. The CPU itself--- the hottest part of the PC--- remained just under 100F/37C. Great!

But in the morning, the system was dead. What!?

The fans were spinning and the lights were on, but no one was home. The system was totally nonresponsive. Everything inside the case was still cool or only slightly warm to the touch, just as it had been when I last checked it. The only thing that was different was that the it wouldn't do anything; or, when powered off, would not boot. There were no failure messages, and no beep-codes for diagnostics. I used all my geek mojo and tried every trick I know, all to no avail. It was just plain dead.

All I can surmise is that the motherboard had indeed suffered infant mortality, as that specific board is known to do. But it happened after I'd removed the fans and heatsinks--- making the board ineligible for product return. I was now the proud owner of a dead and nonreturnable motherboard.

The story has a happy ending though. In fact, I'm using the same PC to type this post. But there were a few more hoops to jump through before I get everything the way it should be. More on that next week!