Most of the sound comes out of the fan axially.
As Foreigner said, insulated duct makes a big difference (& it is a PITA to work with).
Here’s some test data on a 6" AC Infinity to back that up:
AC Infinity T6 evaluation and test data
(see Phase II section)
Cheers G
I can vouch for homemade tote fan silencers. It worked really good.
Using insulated ducts or abs will help…
Running a bigger fan with a speed controller does help…
Reminds of my kid when she was little and the very same for me, when I was little. Kid not knowing that sound travels. Crinkling of the chip bag, carried through the silent house.
I’m agree with @Foreigner and the others about using a bigger fan than you need and running it slower with a controller or variac.
Like @Gpaw i noticed most of the noise comes from the motor end of the fan, fixing the fan directly to the filter helps cut noise quite considerably, I’ve never used a silencer but they’re not too different to a carbon filter, can fan or rvk are better suited to fixing directly.
For my climate i get on much better now with slow and continous ventilation, i get the best temp/rh% figures and close to 0 noise.
Thanks for all the advice
I did get the bigger fan with a speed controller and I am running it on low
I probably should have gotten the ac infinity 6 in and rrun it continuously
So plan is
Move it away From the adjacent wall first
Attach filters directly at the motor
Build silencer
Paps
I did not read this but just looked through the pictures. Agree about it reducing noise. We did it at work (I was a part of a HVAC crew - controls - in a 3 million sq ft campus across 30 buildings), enclosed fans when they were in ceilings and were a problem for the people. I also like using a dense foam to put around ducting rather than fiberglass. The foam works well in the box also, carpet underlay could be used two layers better than one), check your local flooring place to see if they have scraps.
Advice taken
Moving the fan and attaching the filter directly to the fan made a big difference
And keeping it on low dose the trick
Paps
Hey @Papalag
So it is legal there, but not to grow it??? Are there “caretakers” set up you can buy from or is all bought from disp’s ???
No home grow at all ! No small growers either it’s big Money running the show
Under 9 plants 2 years
10 and over manufacturing 10 minimum
Rec to smoke
No medical home grow either
It’s worth the time to balance the impeller on an in-line fan. If you can run it open, without the intake side of the shell, it’s not too difficult to add weight in the form of electrical or aluminum tape. One of mine vibrated like mad until I did that.
The majority of irritating noise occurs where the blades meet the air.
Nice one mate I’m glad it’s worked out for you, the fan to filter connection is the reason i get the rvk style fans there’re easier to hang in a tent as one unit.
French do some things right… Super silent and size is manageable too.
Secret Jardin DF16 filter and fan combo, could be installed filter outside, fan inside with that plastic flange… Brilliant for smaller tents and cabins… EC motor and adjustable speed… Really silent.
I recently bought a 6” AC Infinity Cloudline fan and it was LOUD! They advertised 34 decibels and it was more like 55-70 decibels. I’m thankful i was able to return it.
Ok final report
I no longer need to worry about it being silent
It just stopped working altogether so it’s as silent as it gets
Only had it since early November
Contacted Amazon and vivosun
Amazon was the 1st to respond it’s being returned and I will order a different manufacturer
If it’s only running 1 month and set on a timer once every 4 hours and it breaks down no sorry @VIVOSUN it’s not for me
I’m happy with the light but from now on I’m worried
If you don’t mind me asking I’m curious which exact unit you got (the failed one). I have two ac infinity 6” one for each tent. They’re dc motors that use power supplies so they take a few moments to spool up but they’ve lasted three years.
I got one with the ac infinity controller and I run the other with an inkbird.
@Papalag was saying his Vivosun fan died, I have one of their cheap $50 ones and it’s still holding up as a booster but it’s not that well made compared to the AC Infinity I upgraded to. Paps, maybe you can get an AC through one of the members here who’s a vendor for them like @Ris ?
I think using an 8" Cloudline, ducted down to 6" if you need to, would reduce your noise a lot besides the oversized fan running lower and the EC motor being much quieter than my Vivosun.
Dc motors are the way to go if noise/vibration matter. You’re always going to get some 60hz x blade # resonance in a 110ac fan and anything coupled with it. A large a/c fan will also pull a significant starting current. Possibly sufficiently higher than the relay of your timer can pass. If the motor doesn’t turn it becomes a heater. For a little while…
I run two 5x5’s with one 6” each. They change the air completely in about 90 seconds.
It’s the ribs in your ducting that is amplifying the sound even more too , go smooth pipe also
Exhaust silencers do work , they for very end of outtake
An oversized good quality inline ( I use S&P aka solar palau with an added fan controller eg GSE or smscom ) and smooth pipe is all that’s needed , altho those that need super stealthy a silencer at the end is perfection ( this setup for eu peeps )
You have the same fan as me! But mine sound like a truck! Worst fan ever! Probably got a faulty one 
Edit: Got this instead, no vibrations, super silent and have better airflow that the secret jadin one.
Noctua NF-A14 iPPC-3000
With these attachments 3d printed
Pz 
Hi there
it was the vivosun fan that the bolt holding the Propeller in disappeared it’s not even laying in the carbon filter! The propeller drop and started to bind up in the housing . This actually could’ve been a potential fire hazard I just so happen to get up extra early today and when I walked by my room I heard a very peculiar hum and when I investigated it it was the motor spinning and the propeller like I said minded up against the house you’re not moving
Has anyone ever tried the ac infinity lite fan it’s not there pro model and much less expensive?
