Are 25mm and 38mm fans any different?

[Phoenix]

I am new to the forums so I don't know if this has been discussed before or not. And since the search function is not functioning at the moment I will just go ahead and ask it here.
Are 25mm and 38mm fans any different?
OK I know that they are different in thickness but does this have any effect on their noise especially especially with respect to air turbulance noise?

I have an Antec SLK3800 case which comes with standard Antec tricool fan 120X25 mm.
It is a very nice fan and I am content with its noise at low speed. At this speed it is virtually inauidible for me. However it blows only 35 CFM. It would be nice to have a bit more air in my case since I do some overclocking too. The problem is I don't want to use its medium speed for more air. Although it blows 57 CFM air at this speed the noise caused mainly by air turbulance is distrubing. I thought maybe this is an innate characteristic for 25mm fans and 38 mm fans a better to cut the turbulance noise.

I am interested in buying CoolerMaster AAF-B12-E1 120x120x38 mm fan for this. They claim that it transfers 56 CFM at only 23dB which looks nice on paper. How would it sound when it ransfers this much air with respect to wind noise? I usually dont care about the noise the fan itself is making (bearing ticking etc) since I have noisier equipment in my case anyway.

What do you think?

[wim]

i think the most important difference with thickness is neither noise nor cfm, but how much pressure the fan pushes (i.e. which affects many cfm you will get in real 'usage', with some restrictive back pressure. thicker fans are better here) although i'm not certain about that. maybe someone else can confirm or correct me.

[hofffam]

I believe the thicker fans have the same number of blades, but the blades have a steeper pitch (or angle). If all else is equal (mainly RPM), the steeper blade will push more air, and cause more turbulence.

The tradeoff then is a more powerful fan at reduced RPM vs. a less powerful fan at higher RPM.

So if you want more airflow than your tricool at its lowest speed you could try a 38mm fan - or get a fan quieter than your tricool such as a YL D12SL and run it at higher speed. On my SLK3000B I replaced the tricool with a YL and run it somewhere in the middle of its speed range. It is quiet enough for me and my temps are good.

You have to ignore manufacturer's noise specs. They are useless unless you are comparing various models of the same brand.

I admit I don't like how much 38mm fans intrude into the case.....

[Bluefront]

If you're using a thick 38mm fan as a case fan, it's usually easy to mount the fan externally on the outside of the case. This improves airflow inside the case quite a bit....

[Phoenix]

I believe the thicker fans have the same number of blades, but the blades have a steeper pitch (or angle). If all else is equal (mainly RPM), the steeper blade will push more air, and cause more turbulence.

The tradeoff then is a more powerful fan at reduced RPM vs. a less powerful fan at higher RPM.

So if you want more airflow than your tricool at its lowest speed you could try a 38mm fan - or get a fan quieter than your tricool such as a YL D12SL and run it at higher speed. On my SLK3000B I replaced the tricool with a YL and run it somewhere in the middle of its speed range. It is quiet enough for me and my temps are good.

You have to ignore manufacturer's noise specs. They are useless unless you are comparing various models of the same brand.

I admit I don't like how much 38mm fans intrude into the case.....

Thanks for all your replies.

When SPCR reviewed SLK3000 they measured the sound level of tricool fan. according to that at low setting it is 21 dB and at medium setting it is 28 dB. For me this 28 dB was a bit too loud. Can you compare the noise level of YL D12SL to the mid setting of tricool fan?

By the way what do you guys think of the Cooler Master 120x38 fans?