Re: Austin DIY HT Projects
Hey guys,
I'm working on the computer again, and have some questions (sorry for the post length - you quiet PC aficionados and acoustics guys might like this though).
1) I need to quiet down my case. I mean I need it really, really quiet, not for personal preference but because my application demands it (PC based acoustic measurements that are ambient-noise sensitive - no air conditioner noise, as little PC noise as possible, etc). I have a PS fan, a case fan, a free case fan spot in the front, and a fan in front of my HD that all measure 10cm diagonally from mounting screw to mounting screw and about 8cm diameter around the blades. I take it these are 80mm fans? Can I replace the PS fan too if I keep a similar CFM to what's in there? It's a stock Antec 350w PS. Also I read there are 2 wire and 3 wire and 4 wire fans. What's the diff? What should I get?
2) What is a good, very quiet 80mm fan to replace my current 80mm fans? I realize I need to maintain good airflow, esp in the power supply (don't want any damn blown or leaking electrolytic caps - ugh). I could use the empty case fan slot in addition to normal case fan to keep total case fan CFM up instead of using just 1 case fan in the back that is louder than 2 quieter fans combined (I assume 3dB increase in dB SPL using two identical quiet fans over one fan of the same model since the fan noise will be uncorrelated?)
3) I have an AMD AthlonXP 1.8Ghz 2200+ (socket A). What is the quietest fan/heatsink solution while still maintaining adequate cooling? I will be doing some processor intensive Matlab signal processing. But then again, frying the chip would give me a good excuse to upgrade to a 3000+ or so AMD Athlon XP so I could up my FSB to 200MHz instead of 133, so frying it might not be *too* bad. Let's pick a quiet solution that will provide just adequate cooling. For the moment I am hoping that going from a single 512mb stick to dual 1gb sticks for dual-channel memory will provide enough improvement for my matlab stuff, but it might not. Matlab is mostly a memory bitch (fantastically powerful, but jeez these guys need to learn about mem management).
4) I have a 6600GT vid card with cooling fan. Not sure of the mfgr, but I'm sure it's some cheap off-brand thing (had a Doom3 sticker on the fan enclosure which I thought was tacky). Do they make aftermarket video card cooling fans that are quieter that would be appropriate for this card? I'll be doing this as much to quiet it down as get rid of that damn sticker.
I have a Radio Shack SPL meter and can measure the relative loudness of the fans by sticking it close to them. I can select A or C weighting. In A weighting mode, in relative dB, the HD fan at the surface of the case measures about 0dBA (just used as reference level, it measured much higher in absolute dBA SPL), the PS fan at about +2dBA relative, and the case fan about +8dBA relative. In C weighted mode, it's +4dBC relative for the HD fan, +20dBC relative for the PC fan, and +25dBC relative for the case fan, all relative to the A weighted, 0dBA baseline measurement for the HD fan. At 1 meter from the case, the SPL meter registers 55dBC SPL (absolute). That's way too sucky for my measurements, which happen in the 70-90 dB range (albeit the mic is placed further from the computer, 6-12 feet away).
A/C weighting curves are available here:

I guess I know now why everyone rates their fans in dBA and not dBC It appears most of my fan noise is coming from low frequency sources, which I could have told you from listening to it. It's definitely not a high-pitched whine like some, it's lower frequencies but just loud.
I can't even remotely accurately measure the CPU fan or the graphics card fan (not that my other measurements are accurate, just ballpark) just because there's too much noise contamination from the other fans inside the case, but the CPU fan looks smaller than all the other fans (looks like maybe 60mm? I'm sure it's whatever the stock CPU cooler was that came with the system). Again, a better heatsink with a bigger fan recommendation would be appreciated. Or at least tell me where to look.
Any recommendations on cooling would be greatly appreciated.
OTHER QUESTIONS NOT RELATED TO COOLING:
My mobo (Asus A7N8X2.0) has 6 USB ports - 4 on the back and 2 on the front. The two on the front are low speed (ie not USB 2.0). I thought they were supposed to be USB 2.0. USB1.1 or whatever rev it is is just barely adequate for my purposes, I understand that with an external USB soundcard USB 1.1 or whatever will be good for 24/48 sampling but not 24/96 - 24/96 would be nice but apparently requires USB 2.0. Does anyone know if a BIOS update or some other kind of update might get me 2.0 support? I though the front panel jacks were supposed to support 2.0 but I could be wrong.
DVD-RW: What brand should I look at? These things have gotten cheap. Only requirement is a good name brand and a black bezel (for my black case).
PCI Slot Covers: Looks like the person I inherited this comp from pulled some of his PCI cards but didn't replace the PCI slot covers on the back of the case. Cleaning out the dust tonight I found a dead cockroach which must have gotten through the open PCI covers. I also figure some noise could be escaping out the back through the open panels. I tried stealing some cover panels from an old Dell but they didn't fit. Can replacements be found?
Also, are there any products made to line PC cases that absorb sound? I frequently use fiberglass and foam based products in my acoustic work but am hesitant just to go using spray adhesive and sticking it all over the inside of the case. I was mainly thinking about the removable size panel and maybe the bottom of the enclosure. That stuff tends to be pretty insulative though so it may be a problem. Just wanted to know if any PC-specific acoustic damping solutions are available.
I might think of some more quesitons, but I think this just about covers it. Thanks for any and all recommendations!!!
Domo arigatou mina-san!