DIY fan muffler (30% noise reduction) for $30

[FreezerBoy]

sweet scilencer designs, great thread! this is exactly what I need for my setup to make it really stealth.

cheers, Ez

Silencer is not a good description. While it will reduce noise greatly, there is still noise. I've added a fan speed reducer and there's still noise. I'm going to try insulated ducting and a sound proof box for the fan and see where that gets me.

Maybe it's just semantics but, to me, stealth is when you can hang out next to the cabinet, answering Detective's questions about the dead body on the other side of the house. Been there, done that. With this alone, I wouldn't let them in the garage. But at least I can now open my garage door, something I was terrified to do before I added the muffler.

This thing works. It works REALLY well!!! But, I wouldn't want people to expect silence.

 

[StealthFarmer]

Good tutorial!

This looks awesome for a setup in which the exhaust would be blown into the attic, outdoors, or away from living spaces but isn't this bad to use inside where you sleep and stuff? Im pretty sure tiny particles of the fiberglass insulation gets blown around and I heard breathing that stuff can be pretty bad for the lungs (cancer, etc.)

Im going to do this but with polyfill, seems much safer because this thing will be in my bedroom. Anyways K+ for the tutorial!

 

[slimshady]

Nice Information,Thanks man.

 

[weedworm]

+1

 

[ItsAllOver]

Basically, constructing one of these is like fabricating a short piece of rigid insulated ducting, right?
I set up my 410cfm Sunleaves Windtunnel and used flexible insulated ducting on the exhaust side, which leads into another area of my house, and the exhaust emits barely any sound whatsoever at the outlet. Now I know fan size is important here, I have not tried it on much larger fans myself, but I bet it would work. I have heard from experienced acquaintances, though, that the insulated ducting does wonders on multiple large (~1k cfm) fans

Maybe before you build one of these, y'all should just grab a section or two of flexible insulated ducting at a hardware store and give that a shot. I think you'll be surprised an pleased with how quiet it makes the exhaust side ducting.

Now to take care of the fan itself.... I'm thinking of wrapping mine, which is currently hanging from the ceiling, in some kind of fleece-like blanket. Maybe 4" thick.
I'll report back with results.

Sorry to naysay, I'm just throwing out other options that might be effective.

Peace!

 

[pontiac]

This goes to both kovenant and Nubie Biatch.

 

[DIRT DIGGLER]

I saw this thread and went directly to the hardware store....works like a charm.
Thanks for the helpful DIY..now I can finally sleep at night.

 

[jawnroot]

For a 4" fan in the 150 cfm range, would one need to build the full, four foot, six inch diameter muffler, or can one get away with reducing it to 6 and 4 (as opposed to 8 and 6)? Can the length be reduced to around 3 feet as well? The four foot example with 6" outlet is a bit too large for the space I have to work with.

 

[FreezerBoy]

Try asking redgreenery over at Ventilation 101

My guess would be reducing the diameters core would increase both pressure and noise while reducing length would lessen noise reduction.

 

[EdIsOnnOsIdE]

Thank you Kovenant for this tutorial. This is one of the things i overlooked in my system build. NOISE.
jawnroot "For a 4" fan in the 150 cfm range, would one need to build the full, four foot, six inch diameter muffler, or can one get away with reducing it to 6 and 4 (as opposed to 8 and 6)? Can the length be reduced to around 3 feet as well? The four foot example with 6" outlet is a bit too large for the space I have to work with."
Yes,you can. this tutorial was for a 6" fan. I have a 175ish cfm vortex. I used a 4-6" increaser/6-4"reducer then I made mine 4 feet long. It took out about 85% of that rushing air noise. The muff stuck out over my tent too much so i cut it in half.. I wish i hadnt. I could hear a faint rushing air noise again. I added back a foot. 3' total seems just right. I used polyfil for mine and not fiberglass as i vent inside my house. hope that helps. grow on.

 

[jawnroot]

Yes,you can. this tutorial was for a 6" fan. I have a 175ish cfm vortex. I used a 4-6" increaser/6-4"reducer then I made mine 4 feet long. It took out about 85% of that rushing air noise. The muff stuck out over my tent too much so i cut it in half.. I wish i hadnt. I could hear a faint rushing air noise again. I added back a foot. 3' total seems just right. I used polyfil for mine and not fiberglass as i vent inside my house. hope that helps. grow on.

Awesome. That's exactly what I wanted to hear.

 

[jawnroot]

Got it all hooked up. Definitely attenuates the sound by about 50% or more. The rushing air noise of the exhaust is completely eliminated. I applied some stick-on insulation to the external length of duct, which further reduced noise. 100% worth the trouble of building.

There's still some noise coming from the fan and duct, but it's much less than what it was. Before, it was barely tolerable, almost as loud as an air conditioner. Now, it's a fairly gentle noise, which is completely canceled out if another device is running (TV, fan, etc). I'm still going to run the main ventilation fan 12/12 with the light, as realistically at night when everything's quiet I can still hear it pretty well, and don't like that kind of racket when I'm trying to sleep.

FYI, my muffler is 4" internal, 6" OD, and three feet long. Filled with poly, as it exhausts into the house.

 

[Hollaachu]

This is the Best Thread In The World

 

[Granger2]

This IS a great thread. Here's a great product that I've used for multiple things and have plans for more.
http://www.insulation4less.com/Insulation4lessProduct-21-Prodex-Total-4-ft-x-25-ft.aspx

I have my whole room except for the floor lined with 2 layers of this. R-15.67, 19db sound reduction when installed properly [with a 1/4" air layer]. I insulated my door with it, and if you put your ear to it, you can just barely hear a slight fan sound. Super light and easy to work with, cut, etc., infrared barrier, 1/4" thick, impervious to water, reflective.

It's a bit of a chunk to order the minimum, but once you get it, the possibilities are many. I plan to insulate my air cooled lamps with it. To get the full R value and I assume db value, you have to have the air space, which isn't hard. You just cut little strips of it and tape them on to lay the sheet over. No drooping unless you have more than 2' horizontally without support under the sheet.

I don't need to insulate my 3 6" vortex fans for sound, but this would take up much less space than fiber batting of any kind, and you could put 2 layers with 2 air space layers, and it would only be 1" thick.

Just an idea that I would do if I needed to, that maybe someone would like to try. Have fun. -granger

 

[omgwt]

Great thread indeed. I made two mufflers and for the cost of roughly 1 pre-fab muffler i got 2 custom mufflers with a total length of 5 feet. I used the poly thing on a roll - took about 2 hours and I have a hard time hearing the air rush anymore. Unfortunately I have a cheap inline fan so even tho I insulated it in a cardboard box it still makes noise.
Mufflers worked great to remove the whosing air noises though so i give this guide a 10/5

 

[omgwt]

I bought a new fan with a brushless DC motor since my last post - my tent now makes the same amount of noise as that of a regular computer. It's awesome, and I sleep like an angel every night with no significant noise pollution.