Silencing an extractor fan

[kushedy]

Yes another fan silencing thread!
I need to quiten down an extractor fan in a cupboard grow. I know the most common methods of reducing the noise from an extractor fan are:
1: putting the fan in a box and then filling it with expanding foam.
2: taking something like a blanket and repeatedly wrapping it around the fan.

I don't really have time to test out both ways. Does anyone on here have experience of these methods & can tell me which is the most effective?

 

[iloveweed123]

Yes another fan silencing thread!
I need to quiten down an extractor fan in a cupboard grow. I know the most common methods of reducing the noise from an extractor fan are:
1: putting the fan in a box and then filling it with expanding foam.
2: taking something like a blanket and repeatedly wrapping it around the fan.

I don't really have time to test out both ways. Does anyone on here have experience of these methods & can tell me which is the most effective?

I've tried both and in my opinion the box method is best, i didnt fill it with expanding foam but rockwell roof insulation type stuff tho. Combined with a variac i can hardly hear my 6'' RVK

 

[kushedy]

Thanks for info iloveweed123. Did you use roof insulation because it's better for noise dampening or as that's what you had to hand?

 

[iloveweed123]

Thanks for info iloveweed123. Did you use roof insulation because it's better for noise dampening or as that's what you had to hand?

Hi

Sorry for the late reply. After reading various posts on UK forum's as that's where i'm from it was recommended to me.

In the UK at the moment because of our stupid laws noise issues are a big concern.I have a huge block of roof insulation i keep spare anyway so i made sure i used loads and rammed it in and around the fan and then some. Expanding foam will do the same job i'm sure

Forgot i do use acoustic ducting ( just on exit side )

 

[troutman]

I got myself a duct silencer and it cuts down on the noise very well.

 

[who dat is]

If you can afford the space get insulated ducting like you would have for an HVAC system for you furnace in your house. You can get either R6 or R8 insulated flex duct and that helps as far as the duct itself goes. I would also get a fan speed adjuster if you don't have one already so you can dial the fan speed down to where you actually need it instead of having it go full speed. Lastly you can wrap blankets and whatnot around the fan if you need to or I use a rubbermaid container stuffed with old blankets as well in addition to the other measures I mentioned and you can hardly hear the fan.

 

[noreason]

Boxing it with fibers/foams or other solution is very effective, but don't forget the box itself. Wood ones are not all the same…guess the best ones are made of HDF but I'm not sure.

Blankets are effective too, but not as a proper boxing.

I often use water tray blankets to wrap already silenced extractor fans. I realized they're pretty useless as water tray blanket but they have a good noise insulation, being pretty cheap.

Silencers will do the job on ducts. They do pretty nothing for the noise coming from the fan itself.

Insulated ducts are a must (avoid breathing inner fibers wearing a mask…and better be covered and use gloves too).
Keep ducts as straight as possible and avoid too short ducting.

I bought an IsoMax to test it, still waiting to be mounted, but for sure I can say it's really easy to wrap it because of its simple shape.

Hope it helps

 

[yesum]

I went with a S & P TD-Silent fan the 100X. Low speed is really quiet. Not likely what you are looking for now but in the future maybe.

 

[kushedy]

Thanks for all the responses. I am UK based as well so I really need to keep all signs of grow activity down to a non-existent level!

I have just upgraded an 8" hyperfan which considerably oversized for my grow space. This has a speed controller on it so I can do away with my old variac.
I have also just got some acoustic ducting which will help.

For a box I was actually considering the box the fan came in. Bear with me here I know that's not the recommended mdf built unit everyone recommends.
The box itself is fairly sturdy for a cardboard box. Inside the box the fan was pressed into a polystyrene mould back piece & front piece, close to an inch thick.

I was thinking I could cut through the polystyrene to allow the ducting through & do the same with the outer box. Then fill the gaps in-between the polystyrene & inner box walls with foam or insulation.

As it happens I have both spray foam & roof insulation to hand. Decisions decisions.

 

[iloveweed123]

Thanks for all the responses. I am UK based as well so I really need to keep all signs of grow activity down to a non-existent level!

I have just upgraded an 8" hyperfan which considerably oversized for my grow space. This has a speed controller on it so I can do away with my old variac.
I have also just got some acoustic ducting which will help.

For a box I was actually considering the box the fan came in. Bear with me here I know that's not the recommended mdf built unit everyone recommends.
The box itself is fairly sturdy for a cardboard box. Inside the box the fan was pressed into a polystyrene mould back piece & front piece, close to an inch thick.

I was thinking I could cut through the polystyrene to allow the ducting through & do the same with the outer box. Then fill the gaps in-between the polystyrene & inner box walls with foam or insulation.

As it happens I have both spray foam & roof insulation to hand. Decisions decisions.

Build your box idea and use insulation fiber and polystyrene, if you think it could be better after firing it up swap and change. Expanding foam is permanent unless you wrap your fan in a bag first

 

[jikko77]

if you can get this kind of sponge (the image is just a reference):

http://img.diytrade.com/seimg/2156809/40478514/Soundproof_material_melamine_sponge_foam.jpg

the material used (melamine) have a quite nice soundproof proprety, may it be either in sponge form (like the reference above) or just foam.
if you use a wooden box keep in mind the vibration as well.

 

[Bobby Boucher]

Don't buy 6's or 8's. Go with a 10 or 12 and dial it down. Same airflow, half the noise.

 

[kushedy]

I thought an 8" was overkill for the space let alone 10".
This is going in a 60cm wide, 130xm long & 150cm tall cupboard.

I think I will try boxing the fan with a pile of loft insulation 1st of all & then take it from there. At best I'm going to be having a crack at this over the weekend/1st half of next week. So if anyone else has any experience or input feel free to comment.

Thanks to all contributors.

 

[Bobby Boucher]

Overkill is the idea. Fans make a lot of noise, but so does the actual wind blowing through it. Increasing the inside diameter of the vent reduces the force of the air moving through it. Even if your fan was completely silent, blowing a ton of air through a small vent is going to sound like a wind tunnel. For a cab that small, you could probably get by with one of those panasonic whisper bathroom fart suckers.

 

[kushedy]

I don't think a bathroom fan will have enough pull for a carbon filter & to maintain reasonable temperatures.
I went with an 8" fan specifically so I could run it on low speed & still move enough air.

I've been doing a bit of reading online about noise dampening materials. Apparently polystyrene has next to no effect in dampening noise. Insulation helps but again is not classed as that effective & neither is expanding foam.

Looks like I may have to acoustic foam pads like jikko77 suggested. From what I have read they appear to offer the most effective sound dampening.

 

[Chevy cHaze]

The trick is to detach everything that rattles or hums from everything else.Nothing hard/rigid must be allowed to carry vibrations over to anything. Extruded PU foam mats are great for that. and if you have enough left over, wrap the fan in it and tighten it up with zip ties.It will not get too hot or anything as the airflow on the inside is more than enough to keep the motor cool. looks ghetto, but works miracles. Then insulated ducting like sonodec of course. Buy bigger diameter ducting and tighten it down around the ports of the fan. bigger diameter= less wind velocity=less noise.Silencers too, one before and one after the fan and you will not hear a thing.
Check my super silent thread if you will, there are some examples in there.
All the best to you and your stealth endeavours mate,

CC

 

[kushedy]

Will have a look Chevy. I don't really have room for silencers. It's quite a small grow area. I have used acoustic ducting before so I know that will deal wit the bulk of the noise created by air movement. What I am looking to do is silence the fan motor itself.
All fans make some sort of noise running, either a low hum or a high pitch noise. That's what I'm hoping to reduce.

 

[Chevy cHaze]

Then by far your cheapest and one of the best solutions is to wrap the readily installed fan (with ducts already attached) in an extruded pu foam mat. You can use hot glue to glue the wrap-over part to the rest like rolling a blunt ;-)
zip ties left and right, tighten them down to seal fan in. Super easy and works like a charm. Since it only ads moderate weight, you can install this to a running system .
Oh and most of all get a dimmer for your fan! In most small grow spaces a fann on full is not needed. Get a good one though, the ones for your lights in the living room will not work here.

 

[kushedy]

Hey Chevy cHaze

I had come to a similar conclusion. Did a bit of research over the weekend into acoustics.
Turns out that foam & softer padding doesn't block sound that well. Mainly deflects its direction or at best slightly muffles certain pitch's. From what I read foam is better used as a filler between solid layers. Multiple layers works better than one solid thick layer.
Apparently the best option for blocking noise is solid mass. I guess this is why a lot of people have had good success with fitting their fans into diy solid mdf box's.
I came across MLV (mass loaded vinyl, from memory) sound barriers while I was looking around. These are rolls of thick heavy vinyl that are designed to block noise rather than dampen or misdirect sound vibrations. These some in various weights per meter. Some have a soft foam layer attached to create a multiple layer system. You can buy rolls of this online at reasonable prices.

So the plan is to do what you suggested but using mlv sound barrier instead of a pu foam mat. I figure multiple wraps of this around the fan should be my best bet. I have a sound barrier on order that should be delivered tomorrow so I should be able to start testing then.

 

[Chevy cHaze]

Good stuff, but if you look up extruded PU foam, that stuff is not feathery like other foam, it's heavy and thick and dense and absorbs just about everything.
You can also use heavy bitumen mats glued to the outside of your growbox to get rid of all ratteling...
Good luck !
CC