Sorry but another fan noise q :)

[scaryjeff]

I am looking at panaflow fans to blow through the radiator I haven't yet. On tweakbox.com, it gives the CFM and DbA for each fan, and for the '92mm low speed' model, it gives the CFM as 42.7 and the noise as 27 DbA. I can understand the CFM, but how loud is 27 DbA? I have heard a delta fan and that was noisy, aparently that is about 48 DbA.
Does this mean that this panflow is just over half as loud as the delta, or doesn't it work like that? I am hoping that my watercooled system when I get it will not be as loud as my current one, so noise is quite a big issue for me. The case fans I use at the moment are out of 486 power supplies, so what would their DbA be? I realise that my question is not very clear, but I want a quiet fan, but I don't know what the noise level of a quiet fan is.
Thanks for your help.

 

[TheHorta]

It doesn't work like that.

27dB is extremely quiet. You'd never hear it.

In my younger days I knew all about decibels, sound, etc - but in my old age I've forgotten the technicalities. I may be wrong, but I believe that each 10 points up the dB scale double the effective sound. In other words, the Panaflow at 27dB is less than 1/4 as loud as the 48dB Delta.

Of course all of the drugs and alcohol I did as a youth could have turned me into a raving, psychotic lunatic and I could've fabricated the whole thing.

 

[mlchang]

Ten points on the dB scale is approximately twice as loud to our hearing.

The dB scale is logarithmic, so dB = log (I1)/(I0) * 10. So if I1 (intensity 1) has a power of say 1000W/sq. meter and then I0 (intensity 0) has a power of 10W/sq. meter then the difference in decibels would be 1000/10 = 100. Then take the base 10 log of that and you get 2. Then multiply that by 10 to get a 20 decibel difference.

Two fans of the same power would only be 3dB difference. You can do the math and see that this is true. A 2:1 ratio has a log of ~0.3. Mulitply that by 10 and you get 3dB. So twice the power gives you 3dB difference, but 10X the power gives you 10dB difference.

Human hearing is kind of logarithmic as well. So a 10dB difference works out to be twice as loud. A 3dB difference is usually just noticeable.

So given that the Delta is about 46dB and the Panaflo (no "W&quot is about 27dB then the difference is about 20dB so 1/2 of 1/2 is 1/4, so despite the drugs and alcohol, TheHorta appears to be right . Of course, my alcohol usage may have affected me as well.

Now most things that I've read say that 20dB is the volume of a whisper or rustling leaves. I guess at 1 meter. 30dB is supposed to be a quiet, rural area. So apparently this fan is somewhere between the sound of a whisper and a quiet rural area. I have a 21dB 80mm Panaflo and it is quiet. Granted my HSF is a 36dB Y.S. Tech, so that pretty much drowns out everything else. Yay me.

 

[ReeseCup]

So if you have two 80mm Panaflow L1A's mounted side by side, you would be doubling the airflow but the sound difference would only be about 3db louder?

I ask because I want to get at least 1 L1A and mount it in my entertainment cabinet to intake air behind my hot running Kenwood VR407 receiver. The cabinet has a glass door and a fiberboard back which I want to keep on because of my extremely dusty house. I have been trying to figure out if I'd be better off to get one 120mm fan or two 80's to intake as much air as possible with the lowest possible noise and use a filter.

Chris

 

[mlchang]

<< So if you have two 80mm Panaflow L1A's mounted side by side, you would be doubling the airflow but the sound difference would only be about 3db louder?

Chris >>



I don't know much about DC fan physics, so I can't say whether two 80mm Panaflos mounted side by side is necessarily twice the airflow, although that makes sense to me. From what I've heard, but never tested or researched myself to see if its true or not, 2 80mms may move almost as much air as a 120, but because the 120 is bigger it will still cool better as it moves a bigger area even though CFMs are similar. That's just what I hear, I don't know much about this at all, but I merely mention this as a suggestion that you may want to look into the airflow thing a little more.

But yeah, two fans together would only be 3dB louder, which to my ears is just barely louder than a single fan. Of course, my ears aren't the best judge any more thanks to clubs, raves, headphones, etc...