Quick Fan Question.

[Yakusoku]

 

Just a quick one.

 

I've cleaned my system recently. Then I decided to reverse 3 fans on the top of the case. (They are in the exhaust orientation then changed to intake).

 

First booting it after the cleaning & fan change, I noticed the fans are louder than usual. I've read in a forum that its said that removing dust from the fans may increase its noise. (As dust is somewhat adds damper they said) Not sure if this is confirmed or not.

 

Now I've tried returning my fan into the old orientation (Exhaust instead of Intake).

 

The noise was gone.

 

 

Wanted to just know whats the science behind this. What caused it? Why does Exhaust have less noise then intake?

 

Thanks!

 

P.S.

 

Case: 450D Corsair

Fans: AF120 LED Quiet Edition Corsair

[NeoSk11zle]

1 minute ago, Yakusoku said:

 

Just a quick one.

 

I've cleaned my system recently. Then I decided to reverse 3 fans on the top of the case. (They are in the exhaust orientation then changed to intake).

 

First booting it after the cleaning & fan change, I noticed the fans are louder than usual. I've read in a forum that its said that removing dust from the fans may increase its noise. (As dust is somewhat adds damper they said) Not sure if this is confirmed or not.

 

Now I've tried returning my fan into the old orientation (Exhaust instead of Intake).

 

The noise was gone.

 

 

Wanted to just know whats the science behind this. What caused it? Why does Exhaust have less noise then intake?

 

Thanks!

 

P.S.

 

Case: 450D Corsair

Fans: AF120 LED Quiet Edition Corsair

For a second I thought you were talking about some mishap information about Linus.lol.

[Electronics Wizardy]

Probably bearings. Sometimes they make more noise when pointed one way.

[Yakusoku]

4 minutes ago, Electronics Wizardy said:

Probably bearings. Sometimes they make more noise when pointed one way.

Oh! I would like to clarify. Its not a different noise, its "louder fan noise". Its as if I turned the fan curve higher.

[Orangeator]

6 minutes ago, Yakusoku said:

Oh! I would like to clarify. Its not a different noise, its "louder fan noise". Its as if I turned the fan curve higher.

 

This is due to there being less weight on the fan blades (ie. dust) thus they can spin faster and more aerodynamically... Which means they move more air.

[Yakusoku]

2 minutes ago, Orangeator said:

This is due to there being less weight on the fan blades (ie. dust) thus they can spin faster and more aerodynamically... Which means they move more air.

I see, so dust can act as a dampener to sound then.

 

But why did the noise change (significantly quieter) when I decided to put it into Exhaust instead of Intake?

[raine]

Well part of the issue is that unless your fans in the front and back are both changed to exhaust when the top 3 are intake you are trying to pull in 5x as much air as you are pushing out. Even with the positive air pressure pushing air out through the vents in the back, the fans are still trying to pull in air and that air is creating more pressure to a point where it is high enough that the air is trying to escape out the top, which is creating more resistance so the fans have to work harder to pull air in.

[Yakusoku]

6 minutes ago, raine said:

Well part of the issue is that unless your fans in the front and back are both changed to exhaust when the top 3 are intake you are trying to pull in 5x as much air as you are pushing out. Even with the positive air pressure pushing air out through the vents in the back, the fans are still trying to pull in air and that air is creating more pressure to a pint where it is high enough that the air is trying to escape out the top, which is creating more resistance so the fans have to work harder to pull air in.

 

I see, thanks for the science!

[SpradTech]

It could also come from one fan blowing air into another fan (CPU fan, for instance). It would make a different noise rather than sound like the fan is spinning faster, though. If you want to see this effect in the extreme, take one of your fans and blow into the fan blades.

 

Unless it's sitting in open air, the fan will have some resistance that it must overcome from the mesh cutout and fan filter on your case. It may not be much resistance, but it is there. Fans can respond a little bit different depending on if the resistance is on the intake side or the exhaust side. Try covering the intake and exhaust with your hand and see how it responds when you vary how much of the intake/exhaust is covered by your hand and when you move your hand closer and further away from the fan.