Inline fan box: Make it silent

Krip, that's badass. I love the small spaces + stealth. There is no way I would be growing if I had the original inline noise. Sounded like a industrial vaccum hiding under my stairs. I had a hell of a time finding silencing projects. I wish I saw your box before I made mine...

Busted, I'm not knowledgeable about this stuff. I had to wing it. You are correct about the material, or amount. It isn't "silent", sounds more like a small refrigerator running. My box is rather large for a smaller inline. To do it again I would use a 6in inline with speed controller in a box with more insulation. At least my brain worked to get rid of those hella small wood screws. The inline vibrations are at a minimum due to rubber. It was a fun project. After 2.5 years the sucker is still going strong. Shared info is always appreciated! Thx hommes.
 
All you'd really need to do is make the washers a little thicker. That, or put some rubber feet on the chassis to improve it noticeably. A fan isn't like a studio monitor or larger air-exchange systems. The noise-cancellers don't need to cover jet engines. I went into detail just to paint a fuller picture. :cool:

Edit, if you do use rubber feet, make sure the rubber isn't too hard or you'll be close to square one. The stick-on felt variety might suit better for this application and you could screw through the felt to bury the screw heads a little and protect surfaces.
 
Sorry, but I'm thinking as I go.

Think of a fan like a tire on your car. If a balance weight falls off, the resulting effect increases with speed. If a bearing's worn or there's more dirt/dust on one blade it can be enough for it to try to shake itself apart. Think of what the dashboard does with an unbalanced tire at 65 MPH on the highway. It tries to shake itself from the car. At city speed you'd never notice there was an issue. Same effect on a lesser scale, here. Point is, make sure fan blades are clean if you want to be as silent as possible. Devil's in the details.
 
Sheesh, the tighter you compress a material, here the rubber grommets, the more you lessen the desired effect by 'stiffening' the mechanical connection.
 
Last thing, cross my heart. You want the rubber sandwich between the screw head and the outside of the enclosure and inside between the fan 'feet' and box. Sandwiching the feet of the fan defeats the whole purpose. Doh!
 
I built one of these. Basically I suspended it inside the box with rubber tarp straps and caulked the crap out of the interior joints then filled it with fire retardant noise reducing fill. The only noise is air riding through the ducting. Worked out great.

Good idea, glad you thought of it! ;)

Yeah, after I posted my plans I started thinking I was going overboard. I'm used to de-coupling things much larger and that shake violently as a purpose. Even rubber bungies would be good, just chop one or two up. An old inner tube, cut up a folded to multi layer bands would work.
 
Good idea, glad you thought of it! ;)

Yeah, after I posted my plans I started thinking I was going overboard. I'm used to de-coupling things much larger and that shake violently as a purpose. Even rubber bungies would be good, just chop one or two up. An old inner tube, cut up a folded to multi layer bands would work.
I actually got really short rubber tie downs and it works great. My grow box is so small that I didn't have room for it in the box but I didn't want to half-ass it either. Again, no noise save the air rushing through the ducting but even that isn't that loud as I've got it turned down so low it's barely audible.
 
Right. So your hanging on rubber while connected to ducting and the box is filled/caulked. Your fire fill is stuffed in all crevices? Then sound is gone. If I'm ever in need of a new fan I'll do this. I assume you can do a much smaller box with that setup.
 
Right. So your hanging on rubber while connected to ducting and the box is filled/caulked. Your fire fill is stuffed in all crevices? Then sound is gone. If I'm ever in need of a new fan I'll do this. I assume you can do a much smaller box with that setup.

I have a 4" inline fan/blower. I loosely measured around it and gave it just enough space so that it fit snuggly but not tight. I mounted 4 small u "brackets" to what I call the top, strung the rubber tarp tie downs, which are very short and sturdy, through the u brackets then put the hooks from the tie downs through the mounting holes of the fan which suspended the fan inside the box.

This buffered the vibration from the fan which at the speed I'm running it was minimal. The noise from my fan is mostly the air rushing through the ducting but the speed is set so low that the fan is almost, especially inside the box, inaudible which was the goal.

To deaden the sound of the air through the ducting, insulate it with some material from one of the craft stores like "Joann" or something like that. I bought some remnants of fleece to zip tie it around the ducting as I didn't need much but I didn't do it because it was quiet enough as it was. Buying insulated ducting wasn't practical for my application so I returned it.

U bolt.JPG


tie downs.JPG


Then I bought one of those 2600f, or whatever it was, fire retardant blankets on ebay and stuffed it all around the fan. It acts as both noise suppressant and fire safe.

blanket.JPG


The box itself was chaulked and sealed, made from 1/2" plywood. The fire danger on one of these fans is really low to the point of being infinitesimal so I'm not worried about that but a little insurance is smart.

20180926_094858.jpg


Size wise I think it's only 13" tall by 8" deep by 13" across..something like that.

I've seen several examples of this online, this post included, and just made up something that works for me in my space.

I hope that helps. I wish I had taken photos of the build but I didn't darn it. Let me know if you've got any questions.

:Namaste:
 
Back
Top Bottom