G’day everyone, I’m looking to build a noise reducing box for an inline fan;would love to hear any ideas or tricks you guys may have,
I have a fair Idea in mind putting together a insulated mdf box suspended to reduce vibration etc but would love to hear any ideas before I tackle it. 
as I won’t be doing much of the work due to my eyesight issues I figured if I had some good instructions/plans I can show my wife and together we can work it out.
Thanks in advance guys your help is always really appreciated.
Happy new years OG’s
5 Likes
i found some thin sheets of insulation in my garage and they work well. it’s about an eighth inch thick, has squares so it can be easily estimated for cutting, foil backed on both sides, says alside on the piece i have that i can read right now. thisis what it looks like. looks a lot like thinner pieces of styrofoam board we used to use on walls for houses in between the plywood corners as that was half inch thick. the half inch stuff also works well but limits space.
i built a small box to cover mine out of osb, put the alside over the entire inside, and used foil duct tape around the flex hose entrance and exit. worked good enough that my 16 yo daughter didn’t know i was growing under her bedroom about 20 odd years ago, and she was a pot smoker at the time. she brought the habit with her when she came to live with me at 16. i’ve also heard that using rubber washers to absorb the vibrations work but i didn’t need to go that far after using the foam. one of these days i’m gonna look up pics of that grow and the crap i made to help it along.
3 Likes
Sometimes I will take a small blanket and wrap it around the fan. It helps. I do see one that comes in a nice case. Terra Bloom
2 Likes
heres what i found when i was looking earlier
2 Likes
Definitely also look into acoustic resonance as it relates to duct size, fan blade size and RPMs, often noise that is resonant can be broken by changing one of those parameters:
2 Likes
I use a Styrofoam box my dad got his meds in. I just cut holes for the ducts and wiggled the fan into it. I could see a box store party cooler doing the same thing. Might actually fit better.
2 Likes
insulated ducting can help quite a bit. most of the noise of an inline fan is from the air rushing rather than the fan itself. if you can choke the noise at intake and outtake its pretty quiet
2 Likes
Nice, I wouldn’t have thought that the pass though would make a big difference.
As Beacher said, most of the sound is radiated axially and the best sound suppression I’ve found is insulated ducts. Which are a PITA to work with (compared to regular). Here’s some test data showing the difference.
{edit} The noise data is in the Phase 2 section, halfway through.
Cheers
G
3 Likes
Thanks heaps guys this is all really helpful 
it’s my first project for 2023 to tackle. I’ll be using insulated ducting but the fan itself has a fair hum to it that’s pretty recognisable so any efforts I make to quieten it the better:v:
Look for Fat Mat, Dyna mat, or at Walmart if your area is infested with one, car sound deadening mat. A fan hanging from bungees can also be a bit quieter then hanging off a hook that is fastened into a rafter/joist. Good luck!!
2 Likes
not sure your set up but i will be venting into my attic and i will be placing my exhaust fans in the attic itself.
3 Likes
I use a Styrofoam box to house my exhaust fan and it is totally quiet but the air entering the carbon filter in the tent is now more noticeable, short ducting with as few bends as possible helps too
4 Likes
Most of the sound comes out of the fan axially. If you use an insulated air duct you can zap most of the sound. (I ran numbers on my setup)…
Cheers
G
6 Likes
Cheers for the info guys it’s really appreciated,
I’m going to test out a few ideas & work out my best options
2 Likes
I have a horn case. It’s about 4 foot long. I’m thinking of making it sound prof.
1 Like
My first set up, maybe 22 years ago. I found a sweet spot, from basement up to the attic.
I built this exhaust system that shuttled the hot air up to attic.
It worked like a dream!!
Fast forward to one morning, we wake up, and there is about a foot of snow, had fallen.
I go out and start to shovel the driveway off, to get to the mail box.
Driveway is about 60’ long, about 17’ wide and we got a turn around. Takes about 3 hours.
I take out yesterdays mail, out of the mail box, and I’m absentmindedly looking at the litter, when I see a car going by, and they are looking past me, with the classic WTF look on their face!
As I turn to go back indoors, I look up at the roof, and there as a perfect round hole, about 3’ wide, smack in the middle of the front facing slope of the roof!
Talk about sudden impact, to the brain, and how the fuck do I explain that?
I went and got a tube type heater from the garage, and blasted the heat in the attic for a couple of hours to melt a huge area, so it was not a thing. It did freak me out, then we laughed like hell about it.
All the best to all!
4 Likes
To silence the fan on top of my tent, I wrapped it in old winter coats from a previous job.
I once had a fan in the attic screwed to joists but I could hear the vibration from inside. To fix that, I put a couple screws in the roof joists and hung the fan from a couple bungee cords. The cords dampened all vibrations and you couldn’t tell it was there anymore. It’s just hard to explain if you have someone go up there for work.
3 Likes
That makes sense to me, I’ve seen lots of shaky big fans strung up in a cobweb of bungees so they can float and vibe up there quieter and not jump around in my time in kitchens and warehouses. Also it makes me think of the underground raves I used to throw with my friends, we had a long-running overnight monthly house music party that was also sort of a rent party for the loft we held it in. Small room, lots of subbass speakers, and a shaky old factory building meant that we needed good isolation for our turntables and mixer setup for the DJs, no point in bringing in $10k of Technics turntables and Rode or Allen and Heath mixers if the whole setup is just going to get shaken to hell, ruining the sound. Professional iso tables are expensive, often use air and water or gel cushions or even electromagnetic levitation nowadays. We made one by hanging a large box like a shallow garden bed 24" x 84" from the ceiling rafters with heavy chains and eyehooks, screw links, then the tabletop was sized a few inches smaller in all dimensions to drop down inside of the box hanging by the chains. The two were connected by hundreds of small cup hooks and thousands of thick rubber bands from an office supply store. Worked pretty damn good to keep the needle from skipping or flutter and wowing.
4 Likes
Whatever works! I’ve tried dampening the area around my turntable too but can’t rig something up or the wife will throw a fit.
Big marble topped mid century dresser is what it’s sitting on now. Could be better but I haven’t found anything cheap and pretty yet
3 Likes