concerning fan voltages and noise...

well, i was just thinking about this since i have around 6 places for fans in my case...

if you can, plz put these in order of softest to loudest.

Fan X at 12v
2 Fan Xs at 5v
1 Fan X at 5v, 1 Fan X at 7v
2 Fan Xs at 7v

oh, and if you haven't figured it out, they are all "Fan X" because I want them all to be exactly the same fan.

and this is only a generalization, so no specifications.

for some complicated reason, dB is actually approximately linear with voltage and CFM.

so. the question is: Which is louder, FanX at 12v or 2x FanX @ 7v?

FanX at 12v is "X" dB. 2x FanX @7v produce 7/12X + 3dB. (2x fans at Z noise each produce Z + 3dB when combined). 5/12X is certainly > 3 dB. (X is probably at least 20 dB).

So, in order of noise, loudest first:
1x FanX at 12v
2x FanX at 7v
1x FanX at 7v, 1x FanX at 5v
2x FanX at 5v

So: for least noise for same CFM, have more fans or larger fans.

thanks Wesson, that's exactly what I wanted to know.