Fan Noise, what are we missing?

C

Comte

Gawd
Joined
Jan 2, 2001
Messages
946
Ok, fan noise is a big problem for modders, and I think we are missing something in efforts to reduce it. I dont know what, though. What, exactly, is causing the noise? Faster fans, blades spinning faster, the air restriction, what?

Plus, that dead zone right up under the fan. If you were to get a spacer and lift the fan up 1/2 to 1 inch from the heat sink, would it eliminate that dead zone and cut down on the noise of these highspeed fans?

Or any other bright ideas? How about some sort of noise canceling device in the tower to cover it....
 
The fact is that the noise from fans is caused by mechanical vibration and air turbulence. You can reduce mechanical vibration to a certain extent by isolating the fan from the case (via suspension or dampening). You will not be able to prevent vibration within the fan (with the spinning blades & hub and the stationary box), but you can reduce it by using ball bearing fans. You will also not be able to prevent the air turbulence. The best thing you can do is to port it through sound-absorbing foam towards out away from yourself. You can also use a baffle, but that will reduce cooling effiency.

[edit]The best thing to do would be to reduce the speed of your fans, isolate them from the case, and buy quality ball bearing fans (they also will not wear out as quickly as brushed fans). The final word is that you can reduce fan noise easily, but making it inaudible is very difficult.[/edit]

-special [k]
 
Special[k] pretty much has it down. You can isolate and dampen mechanical vibrations to an extent, but you must also pick well balanced (usually more expensive) fans to really cut down on vibration. With regards to blade noise, you can slow down the blade velocity with any number of fan controller designs. Beyond that, you can use some aviation tricks like shrouding or ducting the fan, or even applying dimples along the span of the fan blades. These are pretty exotic tricks, so I suggest looking at optimal fan placement and speed before delving into the aerodynamics of fans.
 
I agree, but I find that generally, _really_ good sleeve bearing fans beat any ball bearing, noise-wise. And then there's the custom magnetic-beearing fan on the proc... NO contact between rotor and stationary parts... :heart:
 
Ever heard the difference between a fan with and without a wire fan grille attached? I think that's where a LOT of the noise comes from; air turbulence.

Read the thread in regards to sound-dampening spray, and click on the link to yoshi's quiet case to get some ideas as far as what can be done about it.
 
So if I knock off the fangrills off the back it will be quieter? Drool I think ill attempt it then :p no dremel so it will be a challenge :(
 
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