21 dBa + 21 dBa = 21 dBa??? Anyone know noise levels?

[Szech]

Short of the Papst low noise fans (which are rated at 12 dBa), I have found the Panaflo FBA08A12L-1A to have the lowest noise specification. 21 dBa!!! However, for my case, I would want to put two in. What noise level would this be then? Because I could also use one 120mm Panaflo instead, which is rated at 30 dBa, if it would end up being quieter.

I know that an increase of 10 dB is twice as loud, so would two 21 dBa sounds end up being 31 dBa? Or would it just be 21 dBa?

Thanks http://www.sysopt.com/forum/smile.gif

[AuraEdge]

I think dBa's are go up logarithmicly...so double the sound is 10 Dba higher. So if thats right, then it would be 31dBa. like you said. I guess if two people hear it, its probably true eh?
I still think that you would be better off with the 120mm fan even if thats not true, since thats far more airflow then two smaller fans can deliver. Not only that, but the noise would be lower pitched. Smaller fans always have higher pitched squeals, sicne they run higher RPM.

[Szech]

Oh, wait a minute... I just read off a google search that 10 dB louder is 10 times louder, and 20 dB louder is 100 times louder. My head hurts.

[Underclocked]

Since the ratio is logarithmic, increasing dB by three is double the volume. Right????? 24dB is twice as loud as 21 dB according to my thunkin'. As far as putting two together, there is not an easy answer because you are mounting them in a case which would certainly have an effect on the noise level.

[Graham]

Up 3dB = twice power

G

[Mungla]

Graham is correct. For every 3db that your signal or sound increases, you double the strength.

[Szech]

Thanks! I will go for the dual 80's. Every dB counts when a power supply sounds like a jackhammer.

[Szech]

It's all good in the hood http://www.sysopt.com/forum/smile.gif

[BBA]

Graham is right...3 db increase is twice the power. 1db= the smallest change in sound the ear can detect.

When dealing with multiple sound sources, the sound does not 'add' unless they are both in perfect synch. Usually, this never happens, due to the acoustics of the environment and the physics of the source sound. A lot of times, the sounds cancel out each other as well as add to each other. ( People who do stereo setups know this effect of mismatched phasing very well...especially in bass intensity ).

Also, the level of sound decreases proportionately to the square of the distance from the source to the measurement point. IE...it will be 4 times louder at a distance of 1 foot away from the source than it will be at 2 feet away from the source.

[AuraEdge]

lol
Did I mention I dropped Calculus this semister cuz I was failing it? sorry bout that.