(Figured I'll just post this here in case anyone else is considering a similar project...)

I have a dual 866 desktop running in a Lian-Li PC-60 case that I was liking in just about every respect except noise. The Tyan 230 MB is behaving, the case has gobs of space and fans -- but it sounded like a 707 taking off. It was really getting on my nerves.

I decided to throw the book at it, more or less, with different soundproofing add-ons (some of them expensive). Before starting, I put a Radio Shack SPL meter on a tripod 16 inches away from the front panel of the PC and recorded noise level (with everything else in the vicinity turned off).

The initial reading was 58db (C weighting)

Step 1 was to line the interior of the case with a product called DexDamp. It is a better Dynamat -- doesn't smell, easier to apply (but would be a *bear* to remove). I even put this on the back of the motherboard tray. I also added some 1/2" mylar-coated foam sound-proofing sheet on the PC's big side panels. I got all this stuff from a local marine pump supply place called Hamilton Jet.

Result after step 1?: 55-56db. And some of the more annoying vibration/harmonic noises seemed much reduced.

Step 2 was to a add a pair of nastily expensive CPU coolers from Germany called Silverados. I got them from a place called Plycon (www.plycon.com). they include resistor adapters that allow you to drop fan voltages to 6 or 9 volts. I'm not running 1.x G AMDs or anything, so I set them to 6V.

Result after step 2: <=50 db Yes, a slight problem with my methodology. I dropped off the bottom of my meter's scale. I should have taken a second set of readings from closer to the box (but I didn't want to get too close lest I read the sound level from a single source like the front fans. Oh, well!)

Step #3: I added a fan controle module (also from Plycon) called a Digital Doc 5. It has 8 thermistor sensors and 8 corresponding headers for fans. I installed 5 sensors. I don't let it turn off the 2 CPU fans, but i let it control the other case fans. I used a program (called CPU-Burn, I think) to heat up the CPUs then set the case fans to come on at a range of temps between 29 and 31 centigrade. Those fans mostly stay off now unless I fire up a game or something demanding.

Not sure what the sound-reducing effect of step 3 is, bu the overall effect of the effort was gratifying. $60 for a CPU cooler was a bit much, but it is a lot easier to sit next to this PC now!

Oh, another nice little program I discovered during this process is a Windows utility called MBM - Motherboard Monitor. And a spin-off benefit may be that I'm going to add a touch of DexDamp to the front door panels of my car to see if I can get rid of a slight buzz that occasionally comes from the right-front speaker.

[edit = typos]