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


I was asked what materials I used and how I designed the mufflers for my vortex fans. I thought I would share it for anyone interested. I noticed a good 30% in noise reduction by applying a simple and pretty inexpensive (around $30) solution in my attic.

You will need to buy:

1x 8" hard duct
1x 6" to 8" reducer
2x 6" starter collar
4' by 4' (or 4' by 6') Machine Cloth (Mesh)
Wall insulation or polyfill batting (like in pillows or stuffed animals)
Steel Tape

Step 1:
Roll the Machine Cloth into a tight 4' long cylinder, then slide it inside the 6" starter collar(s) and the 6" to 8" reducer - 6" part of the reducer facing out - and let the mesh expand so it opens fully inside of the collars. I used an extra collar to support the middle (you could do without the collars, but they make it easy to size it correctly - and make it a bit more stable.) Use steel tape to fix the mesh to the collars.

Step 2:
Attach your 8" hard duct to the 8" side of the reducer. You will now have an 8" duct with a 6" mesh duct running through the inside of it.

Step 3:
I used wall insulation... but polyfill batting works just as well. I wrapped the insulation around the 6" mesh cylinder and then slid the entire thing into the 8" hard duct. If using polyfill batting, I would suggest just stuffing it between the two ducts once you have completed step 2. If you are not using batting, and have something you can roll out - it is easier to roll it around the 6" mesh duct and then just slowly slide it in making sure it doesn't kink or group up. Use the steel tape to fix the 8" duct to the reducer and you're all done.

This is the side that connects to your vortex

and this is the side you can aim anywhere into your attic or direct toward an outside vent

once installed it should look something like this:

Hope this helps anyone looking for an easy, cost effective way to help muffle sound. Using bungie cords to suspend the fan in the attic helps as well!


reaperz --> good question. in my experience (i've built a couple between 4-6' long...) i notice diminishing returns after about 5'. i'd say it would be a good idea to try even a longer one... maybe 10 or 12' if you have it - would maybe be nearly undetectable. it is very quiet as it is at 4-6'

glad a few of you find this helpful! :joint:


mysticls -> this is for 6" fans. if you wanted to make one for a 4" fan, you'd just make adjust the parts accordingly. (ie. 4" to 6" reducer, 2x 4" starter collars, and 6" hard duct...)

i have a 6" Cannon fan (250 CFM) on one of these, and a 6" vortex (449 CFM)
thas how i made mine
but i'd have to say it doesnt quite ur fan
it quiets the rushing air
i still had to wrap my vortex fan in insolation
now thats quiet, can barley hear a thing

steve green

gangsta, u just wraped your vortex in insulation..?
i have a 6 inch vortex ,,im not using it right now because its way too powerful
and loud..when i turn it on,,i feel like i can strap it to my back like a jet pack and fly away .

i thought of using insulation,but am paranoid about starting a fire or something.,,...can u explain more on the insulation u did and the effects?
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gangsta -> yes, and no for me. it did quiet my fan, but mostly quiets the air rushing out of the fan. it also works better at quieting the 250 CFM vs the vortex (less flow to muffle.)

i also re-installed my fans in the attic, suspended with bungie, and wrapped insulation around them. i recommend that as well - just didnt post it originally because its really not a 'part' of the muffler. thanks for bringing it up though! the better stealth in our operations, the better off we are! :headbange
yea all i did was get heavy duty trashbag
wraped the fan wit insulation then covered it wit the trashbag to hold the insolation
then tapped it shit then cut holes for the intake and exhaust openings
it super quiet now, i have a 6'' too its a lil bit quieter now than the central AC

Nubie Biatch

Active member
Great DIY Kovenant! I took it one step further and added a DIY Ozone Generator to the Muffler for a little added odor kill as well.


Nubie Biatch

Active member
rr14 & Siddartha,

I have yet to install the duct muffler. I have used the ozone plates with a fan before and they worked great by themselves. I only had a small closet grow last time with two 1m tall plants.

I'm upgrading right now to a 16 bucket recirc DWC. When I get my grow area finished I will start a journal recapping everything.

Hope to be up and running within about 3 weeks. Till then.....


Active member
I didn't take any pictures but I went by this tutorial and put this muffler on my Vortex 440CFM inline and it made a world of difference. I had it in the atic with hose running through the closet ceiling and you could easily hear the air rushing out of the fan. I installed this muffler and it is all quiet now. You cannot hear it at all. There is more noise as the air is sucked through the can filter than from the fan. Thanks a BUNCH!

NubieBiatch - Nice job and good thinking! Hope it works well and please give us an update when you put it into use.



Nubie Biatch -> great idea man, let us know how it works out!

SoulShine -> glad it helped! i had mine setup pretty much the same way you did and once i added the muffler i was alot happier. how do you explain the sound of a bathroom fan running in your house when you have guests over? i love it quiet! or at least quiet enough


another good idea is to use insulated ducting as well, it will also help cut down on the noise, great muffler kovenant, I could use one as the 6" vortex is not quiet on full speed.


Dude: that O3 generator in there is saWEE t. I have a diy ozone generator i built, but i haven't deployed it cause it's in a box and i couldn't get it out of my head there's gotta be a better more streamlined way. 'course um i'm hoping the f word couldn't possibly be a problem but saWEET layout. Much appreciated d.i.y inspiration photo. G1

Mine's a neon 9kV and stainless steel race car grill screen. I've got it in an enameled electrical box. Actually it's a phone box but same deal. Heavy duty 1/2oz shot glasses are the standoffs, siliconed the screen to the glass. Puts out loads.

I just used the O3 generator to kill mold in an attic; worked a charm.
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Nubie Biatch

Active member
Duct Muffler + O3 Generator in Action

Duct Muffler + O3 Generator in Action

I've finally installed the DIY Duct Muffler w/ a DIY Ozone Generator inside.
It works like a charm.
I loaded the room with my favorite incense ("Zen Garden" from World Market) and went up to the attic to see if I could catch a whiff...nada! I just got a good snootfull of O3.

I've attached an additional 6' of ducting to the exhaust end of the muffler to allow the O3 to mix with the air. By adding an 8" duct it allows for the air to mix without impeding the airflow from the 6" vortex on the other side.

I attached the muffler & O3 generator with strapping to minimize any vibrations (there were none). It only generates a faint hum when I turn my 6" 449cfm vortex on. I've also mounted my vortex with the brackets that came with it. I wrapped it in some r-13 insulation to cut down on the noise. (The noise is minimal).

This is the bad little bazooka that's blasting the odor out of my air.

The Ozone Generator kicks out some serious O3

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