How to calculate fan dba & cfm?

ok, im really bad at maths, i really just cant do it and dont even begin to comprehend how most of it works - and im completely stuck on the following question:

My 120mm case fans are too loud (not for me, but everyone else I live with says theyre too loud), so theyre up for replacement...thing is iv no idea what dba theyre currently running at and what cfm theyre pushing...so I dont know what to look for in new fans (as i dont wanna lose much airflow).

Atm im running 120mm sanyo denki's (the ones dockguys was selling with SSS' endorsement a while back) which i think are supposed to be like 110-ish cfm at 45/40dba? I run them all at 7v the whole time (as at 5v they wont start up) -
can anyone work out what estimated cfm & dba they should be running at at 7v based on the 12v specs?

I cant be sure of the exact 12v specs as I couldnt find them online...but theyre roughly right.

thanks folks!

Hmm, either time how long it takes to have the fan fill a plastic bag of X volume...

or ....

Look up the MFG's spec sheet?

maybe emailing the mfg could get you in contact with an engenier that can give you a better system than i.

how do you change the voltage of the fans? o0r make them run at a different voltage other than the max

one way is to hook them up to a fan controller, or you can use a motherboard header and use software to turn them down - tho my prefered method is to rewire up a molex to run them at 5 or 7v

rewire a molex anywhere I can find a guide or tut because only one of my fans get rpm control

Hows this - http://www.dslwebserver.com/main/fr_index.html?/main/5-7-adapter.html centercore?


I think, based on what the link higher up told me (tho my maths is atrocious) i can roughly estimate that if my Sanyo Denkis run 110cfm at 12v theyre pushing about 65cfm at 7v...and thats at about 35dba? have i got that right?
Can someone check my math before I go out and look for 60cfm fans?

thx

Someone here, Voodoo Rufis I think? Has an excel spreadsheet of a couple of fans and their differences between rpm, voltage, cfm, and db. You can plug any fan into the equation.