Quieting A Cooling Fan

Discussion in 'Home Theater Projects' started by Jeff W, Mar 27, 2003.

  1. Jeff W

    Jeff W Auditioning

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    Hi,

    We had an entertainment center built when we finished our basement last year. It has a built-in equipment rack with a smoked glass door on the front. Because it is enclosed, there is quite a bit of heat buildup when everything is on.

    To solve the heat problem, I bought a 2” A/C cooling fan from Radio Shack. I drilled a 1½ inch hole through the back of the cabinet near the top (the cabinet backs up to the mechanical room, so I have access to it from behind). I mounted the fan on the back of the equipment cabinet (on the mechanical room side) so that it draws the hot air out. The fan is plugged into a switched outlet on the receiver so it only comes on when needed.

    The problem is, the fan makes just enough noise that it is audible (although just barely) during quiet parts of a movie. I put rubber washers between the fan and the sheetrock so vibration isn’t the problem. The noise is generated from the air movement caused by the fan blades. I’m trying to figure out a way to eliminate this noise. The only idea that comes to mind is to try to find a flexible hose 1½ to 2 inches in diameter, relocate the fan a couple of feet from the hole, and then feed the air through the hose. So far I haven’t been able to figure out how to attach the hose to the sheetrock or the fan itself.

    Does anyone have any ideas on this, or are there kits out there for this purpose that I just haven’t found? Thanks for the help!
     
  2. Wayne A. Pflughaupt

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    Jeff,

    I suggest using a bigger fan. At a lower RPM a bigger fan can move the same amount of air (or more) as a small fan does at high RPM. Lower speed = less air noise.

    I’m using 4” so-called “muffin” fans, A/C powered. I have them wired to a ceiling fan dimmer to reduce the speed. They also make these DC powered, in which case you could use an AC adapter with switch that changes the voltage output.

    You should have no problem finding a 4” fan at Radio Shack or a local electronics hobby store.

    Regards,
    Wayne A. Pflughaupt
     
  3. Jeff W

    Jeff W Auditioning

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    Wayne,

    Those are two excellent suggestions. I have a couple old dimmer switches lying around, so I think I will try that first. I don't know what the RPMs are on the fan, but it takes several seconds to get up to speed (at which point it is really moving), and that's when the noise becomes noticeable. If that doesn’t solve the problem, or if the 2” fan doesn’t provide adequate cooling at lower speeds, I could move up to a 4” fan.

    Thanks for the help!
     
  4. TimForman

    TimForman Supporting Actor

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    Another possibility is using a PC case fan There is a large selection of fans for 10 bucks, some have manual speed controls and some are rated at only 21 db!
    Check out this thread. You guys are working on the same issue. DIY Fan Thread
     
  5. Joe Tilley

    Joe Tilley Supporting Actor

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    Yours may have different results but I wouldn't waste you time with tubbing it only amplifies the fan noise at the end. I run a single 4" that I made a couple radiused plates for both sides out of 3/4" MDF & used a 1/2" round-over bit on them. Without them the fan drove me nuts from across the room, but with them it's almost unnoticeable.
     
  6. stallej

    stallej Auditioning

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