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Ducts to reduce fan noise

post #1 of 7
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Does anyone have experience with using ducts to channel air flow? Specifically, my ideas look like this:



The idea being the radiator air is blown into the fan duct, and a nice, slow turning (600rpm max) fan is turning to gently move air along the duct and out of the rear of the case. This puts an additional barrier between the noise makers (fans) and a listener. It also lets me make a solid case ceiling, again for noise mitigation.

Any thoughts or experience with ducts like this?
    
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post #2 of 7
That looks like it would create resonance and add noise actually.
post #3 of 7
Depends on the material used I would think. You would need to tune it internal baffles also otherwise the high power fans will push out both sides. At best this will change the pitch of the sound,resonance. If you want to make a muffler then make one.
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post #4 of 7
You might have something. There are places where ducts are use to "direct" sound (but not reduce it)

It might add noise, but it would direct it in a different direction that the user. If you're ok with changing noise quality in different parts of the room, it might be worth a try. Now, I wouldn't suggest that you then take this air-duct and place it 6" from a wall! You might also need to play the the height of the duct to see what yields the best results.

What fans are you looking at using on the radiator? Particularly how much CFM are you expecting total?
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post #5 of 7
You'd want to coat the inside of the duct with something that doesn't reflect sound well and you'd want the duct to be made of a dense material (the thicker/denser, the better). And I'd forgo the third fan if you can. If this isn't inspired by nanoxia's ds1 chimney design, you might want to take a look at it also. (which btw is newly back at newegg!) http://www.newegg.com/Product/Product.aspx?Item=N82E16811281001
post #6 of 7
Quote:
Originally Posted by BBEG View Post

This puts an additional barrier between the noise makers (fans) and a listener.

This is the same idea that many "silent case" manufacturers use, by making the front of the case solid but with slit vents on the sides. Sound becomes attenuated when it isn't directed at you. I agree with 404Error in that you should put something on the inside surface of the duct to further attenuate sound.

You don't need a "guidance fan" because air will find its way out. At those low RPMs you do want to use fans that do higher static pressure.
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post #7 of 7
Google - sound proofing rockwool

We use it at work and does a great job on v16 diesel engines. Also standard foam would help I reckon. Just line the inside of your ducts with it and Walla!
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