I'm looking to quiet my computer, but I'm not sure how quiet it needs to get. I was wondering is there and way to get a good judge on what my ambient noise level at a reasonable accuracy without investing in sound equipment? I don't mind picking up something under $20, but much more than that and I might as well spend the cash on the computer components.

An SPCR recommended fan would give you some idea. Obviously it would be best if you could run it without the computer, from a separate power supply that is silent. Batteries work and are cheap enough, you probably have some already anyway. 8x1.5V batteries would give you 12V, and you could remove one at a time untill the fan becomes inaudible. Somethihng like a Nexus or Yate-Loon fan should work nicely for this purpose.

I don't quite see how this would get me the ambient sound lvl in my house. Is it possible to then take the # of volts for the given fan and look up how loud it is? Does silent mean the fan is at or below ambient dba for the room?

Just to clarify a bit, I want to find out what my ambient dba is with a reasonable degree of accuracy (Is +/- 3-5 reasonable accuracy?)

the actual rated number value of ambient sound consitions is pretty meaningless for end users. Its only real use is to compare like products to see which is quieter.

Just pick quality quiet components, and you wont be dissapointed.

Exactly, you will use the fan as a gauge, because you can find in SPCR's fan reviews articles a chart of noise in dB vs. voltage. I'm not sure though how you can relate the dB of the fan and the fact that it is more or less inaudible with the ambiant noise in dB in your house. Maybe the comments in the articles will be more useful, saying for exemple that "at 7v the fan becomes inaudible at 1 meter with a 20dB ambient sound level in SPCR's lab.

I would say +/- 1 is a reasonable accuracy with a proper measuring device, but with this fan gauge technic maybe you can expect to be within +/-2 dB of the real noise.

But in the end, I think like Aris that it will be of little use to you. Maybe it will avoid the step by step process of tackling each time the noisier component, until you find out that your first quiet component bought is not quiet enough now that your computer is close to silent, but apart from deprieving you of that fun journey ...

The point was not to get accurate measurments but to get some idea of your ambient noise, if you cant hear a Nexus at 7V positioned where your computer would be then good for you. I guess you could get some idea of your ambient noise by looking at SPCR stats of the fan, but absolute numbers are pointless in the end. If a fan is inaudible then that's what it is, it doesn't matter if its 20dB or 76dB.

also bear in mind dB numbers are distance-dependent. I would guess ambient noise for people in rural areas is 20-30dB during the daytime, less at night, with urban areas significantly higher. Generally, if you get SPCR recommended parts (Seasonic PSU, Nexus fans, etc) your computer should be below this level.