Need to quiet intake fan noise. Please help!?

Hey everyone,
So I'm new to Rollitup. But been growing a little over a year. (3-4 cycles)
I recently have been having heat issues with this summer coming in hot! Expessially being in the hot detached garage. So I decided I would cool my light and tent with my vortex 6 in. By sucking in air from outside, as it is almost always cooler outside. I have it set up with ducting from the window to the intake to the 6 in vortex with a phresh duct silencer. Then a y connector on the output on the fan.

THE PROBLEM
I live in a close proximity to my neighbors in a crowded suburban neighborhood and the sound of the fan in taking air from outside is too loud even with the phresh silencer. Does anyone have a fix for this? Please! I have tried puting hepa like filters and towels in between the duct and window but they either restrict airflow (towel) or don't help sound very much( filter). There must be some way of quieting the intake airflow sound.

Also does insulated ducting help the air intake sound? Does anyone know from experience?

Ps- I am planning on getting another silencer to have both intake and output silenced as much as possible. Is this a good idea?
Also I'm using a 1000hps in my 6x6x7 tent 12 plants. Ebb n flo bucket system.

I assume you are hearing the air flow, not noise from the fan. As you noted, most thing to quiet air flow also reduce air flow.

You could:
- add some insulation to your ductwork
- move the inlet opening away from neighbor's window, such as run it up the outside wall like a chimney
- have a longer run inside your garage (increase distance from window inlet to fan)
- slow fan down
- upgrade to 8+" fan and ductwork

If you fan is loud, consider placing fan in insulated box.


I am not real clear on your setup. Straight rigid ductwork from inlet to muffler to fan? Not flexible ductwork? What is the Y connector after the fan? Where does the fan exhaust? Do you have noise concerns with exhaust?
You might get more input with a thread in the grow room design forum.

mrwood said:

I assume you are hearing the air flow, not noise from the fan. As you noted, most thing to quiet air flow also reduce air flow.

You could:
- add some insulation to your ductwork
- move the inlet opening away from neighbor's window, such as run it up the outside wall like a chimney
- have a longer run inside your garage (increase distance from window inlet to fan)
- slow fan down
- upgrade to 8+" fan and ductwork

If you fan is loud, consider placing fan in insulated box.


I am not real clear on your setup. Straight rigid ductwork from inlet to muffler to fan? Not flexible ductwork? What is the Y connector after the fan? Where does the fan exhaust? Do you have noise concerns with exhaust?
You might get more input with a thread in the grow room design forum.

Click to expand...

@mrwood and @PAP3RBOY thank you for your replies the sound Im hearing is the intake airflow sound and not the motor (the silencer helps the motor sound tremendously.) the one window is the only access I have to the outside, there is an attic however theres no opening to outside and it extremely hot in there.
the set up goes :

window----> a bigger one of these things (http://www.homedepot.com/p/t/202907285?productId=202907285&storeId=10051&langId=-1&catalogId=10053&MERCH=REC-_-SearchPLPHorizontal1-2-_-NA-_-202907285-_-N#.UaAp2Ff2J8E) a big dryer vent up against a hepalike filter in the window----> normal aluminum duct------> Phresh duct silencer--> Vortex ---> y spliter --> ducting----> one directly into tent, the other into the 1000w hps.

also i have put an A/C filer between the window and the intake for bugs and shit.

i really dont wanna upgrade to 8 inch stuff cuz i already have everything for 6 and should create enough air. ( when i first set it up regardless of sound, it really cooled the room significantly now its just a matter of not being able to hear the intake sound. i have been reading all day and saw somewhere about spreading a sock across it Im trying that tonight, ill let yous know.) i am open to getting a speed controller but it would be nice to have all the air flow possible as my tent is 6x6x7.

so the question at hand is how do you go about quieting the sound of the air getting sucked into the ducting.

PS- the large dryer vent i got from homedepot is not the exact on listed. i got one with a larger surface area, i believe its a 12 in by 4 in rectangle and it made the sound a bit better. thanks in advance.

If temps are currently well controlled I'd say go for the speed controller. Should help. Beats upgrading if you don't need to.

I gave you the answer in my reply in the other thread along with general problems with fan installations. So I will make it perfectly clear this time ,YOU DID NOT size your duct work correctly ,this is why the air is so loud . YOU NED to go bigger and transition the ductwork , Again this is your problem , I am new to growing ,but I do have over 30yrs exp in HVAC Design and build. Good luck.

I concur with Jrainman. It's hard for some people to believe it at first but just because the output of the exhaust fan is 6" doesn't mean you will get the same cfm rating of the fan to flow when sizing the duct the same and you will get much more noise to boot even with flexible ducting. Here's how you could design the exhaust trunk for a 6" fan/silencer ( I'm assuming no filter because the air is pulled from outside and expelled outside of the grow) to get max cfm output and a quiet exit. How many cfm is the fan rated for? Take that number and now go to the ACCA manual D youtube video and check out what size flexible duct you need to get that cfm rating. After you get that duct connected to the output side of the fan , go ahead make a silencer with two rigid duct reducers and a 4 foot piece ( or 6 foot piece ) of rigid round duct pipe sized 2" greater than the flex duct. Connect in this order: reducer-pipe-reducer. Don't forget to line the inside of the straight section of the silencer with fiberglass insulation and hold that lining in place with steel mesh ( the kind with the diamond pattern used to reinforce a concrete sub-floor). That's your standard duct silencer DIY and there are a few videos available out there that do a good job of explaining it. While I'm here, let me give you a 10" fan/silencer example with actual numbers that pertain to ACCA manual D. So lets say I want to pull air through a 1000 watt hps vented hood. Lets pretend the hood has a 10" round diameter port to connect an exhaust fan ( they usually have an 8" port but I like 10" fans better). Here's what I would do to get the most cfm through the exhaust line using flex duct ( rigid duct has a better cfm output per inch diameter when compared to flex but I like the versatility of flex and most people do as well, I think). Connect a short piece of 10" flex to the fixture and keep it horizontal with no bends. Then go ahead and put a 10" can-fan next and install with the proper vibration arrestor kit that Jrainman already told you about. Now the Can Fan company lists that the 10" fan I'm using is about 790 cfm capable. I go over to Manual D and they tell me I need 16" round flex duct to get that output ( I'm going by memory, Jrainman please correct me if I'm wrong). Now connect a custom made enlarger from a reputable duct shop that enlarges from 10" to 16" in a smooth fashion so as to minimize friction losses.Attach 3 feet of 16" flex duct to the outflow of that custom made 10"-16" enlarger. Attach a 16" -18" rigid metal enlarger. Attach a fiberglass and diamond mesh inner lined 6 foot piece of straight rigid metal 18" duct pipe to that. Now put an 18"-16" rigid metal duct reducer on the end of that straight pipe. Put another 3 feet of 16" flex duct on the end of that silencer. Figure out a low friction/low resistance way of making a stealth exit straight outside through a window or something else to vent that air. If I did everything in 10" I wouldn't even get half of the max cfm output of the fan and it would be very noisy. Oh, by the way... By enlarging from 10" to 16" duct I probably will reduce the sound of the air exiting the house so much that I probably won't need a duct silencer in the exhaust trunk.

Hey contrap. It is obvious you know a bit on the subject of duct sizing and layout and such.

One piece of advice I would like to humbly give you is that you break long posts up into paragraphs. It makes em so much easier to read.

An observation on your post would be that it is not practical for most folks to have a 16" hole coming out of the side of their house or building. Pretty hard to hide something like that. Unless it is going through a roof fan or something. So while upsizing your duct this far would certainly reduce friction and make your fan run quieter and more efficiently it wouldn't exactly be stealth either.

I do like your diy tutorial on the duct silencer. Many can use this info.