Making exhaust quieter

[nizmo]

Got a 220 cubic meters/hour exhaust fan. Works great and unit itself is quiet but the sound of the air rushing out is too noisy. Is there anything i can do like maybe splitting the ducting into 4 to reduce the airflow going out each duct? Its just the sound of the air rushing out.

 

[Smuggler]

Can you use a speed controller on the fan and adjust it's speed/sound to suit you? S

 

[Essex]

I made a silencer just by cutting some carpet and rolling into a tube oversized to your duct by a few inches and a foot or longer and placing over the duct exit so the duct stops inside the carpet tube. It works a little and dont obstruct the flow.

 

[snoopygrower]

best way is to stick a pair tights across the end hole. works a treat

 

[nizmo]

Can you use a speed controller on the fan and adjust it's speed/sound to suit you? S

I'm a bit unsure about that, because i've heard that some fans don't take well to having their speed reduced. I've got the prima klima 2 speed fan, and its already on the low setting.

I made a silencer just by cutting some carpet and rolling into a tube oversized to your duct by a few inches and a foot or longer and placing over the duct exit so the duct stops inside the carpet tube. It works a little and dont obstruct the flow.

So you place this rolled carpet INSIDE the vent? So would it just hang out, and then act as an extension to the vent? How quieter are we talking here? I need to reduce this sound by at least 4 times... Its pretty loud. But then again, i have the fan probably about a foot from the vent exit - i might extend the vent longer so that noise from the fan will travel less.

best way is to stick a pair tights across the end hole. works a treat

This sounds easy ill try this one first haha. Cheers.


Anyone ever used a silencer like this one; http://www.securimax.co.nz/ducting/duct_fittings/duct_silencers.php ?

 

[desertrat]

Anyone ever used a silencer like this one; http://www.securimax.co.nz/ducting/duct_fittings/duct_silencers.php ?

yes, they're also called duct mufflers if you want to search other options, and they work great.

 

[nizmo]

Well the pantyhose didnt do much. Extending the duct a few meters worked ok but still too loud. Might have to try a silencer...

Anything i stuff into the ducting just makes the noise worse.

 

[hehehemann]

Put some filter pads on the ends. I use it folded over itself several times and fill the last part of the exit ducting before it goes out of the window.
Its $1 sheets in walmart. Comes in a plastic bag in the lighting/paint area. Its a black filter made to let you cut it to size required.
This stops the rush of air sound.

For ultimate noise control I bought an 8" inline cheapo fan for $100 and a Variac for $50. I use the fan at half speed and its near silent sucking the heat from a bare bulb 4x8x6 tent.

 

[bloatedcraig]

The best thing to do is to buy oversized ducting, example 4" fan use 6" ducting it gives less resistancce to the air less noise (fan also last's longer). Also you can get issulated ducting, so over sized ducting and inssulated will sort it. Trust me i did it.

 

[nizmo]

Perhaps i should explain my situation a bit better.

I am in a room directly next to the lounge. Above my room is an attic, and i have the air pumping out from the attic (where the plants are) back into the house next to the stairway going up. What really sucks is that i already have a vent in the room which goes outside which would be perfect - but i'm paranoid about cops flying over with thermal sensors. Heated air pumping out at 150cfm+ in the middle of winter will stick out like dogs balls on a thermal sensor.

What this basically means is, the extraction duct is probably about 4 meters from the people who im trying to hide this from. Its quite high in the roof and they can't see the actual duct but the noise travels the short distance easily. I need a way to silence the sound of the air rushing through the duct because it is noticably loud.

The best thing to do is to buy oversized ducting, example 4" fan use 6" ducting it gives less resistancce to the air less noise (fan also last's longer). Also you can get issulated ducting, so over sized ducting and inssulated will sort it. Trust me i did it.

This sounds like it just might work...

 

[desertrat]

i'm paranoid about cops flying over with thermal sensors. Heated air pumping out at 150cfm+ in the middle of winter will stick out like dogs balls on a thermal sensor.

relax, practically impossible to pick out a small grow amongst all those fireplaces and furnaces. tracking grows by thermal signature is only practical for catching large, multiple 1000 watt light grows.

 

[hehehemann]

Run the lights at night 9pm to 9am. Way less chance of any helicopters scanning at those times.
Also check your cities regulations. Out here the cops cant use thermal imaging unless they get a warrant first. Thing is if they have a warrant they would enter instead of using the helicopter in the first place.

 

[johnnytsmitw]

relax, practically impossible to pick out a small grow amongst all those fireplaces and furnaces. tracking grows by thermal signature is only practical for catching large, multiple 1000 watt light grows.

I agree with desertrat. You may want to invest in just taking some time and doing some research on whether or not the infrared choppers are even used in your area.
I am just guessing here but 150cfm wont show off anymore than a heater exhaust or even the heat escaping from windows.
you could also extend the exhaust pipe, perhaps even extend it outside, the longer the air is in the pipe the cooler it will be.

 

[gumball]

The best thing to do is to buy oversized ducting, example 4" fan use 6" ducting it gives less resistancce to the air less noise (fan also last's longer). Also you can get issulated ducting, so over sized ducting and inssulated will sort it. Trust me i did it.

i agree with bloatedcraig, this sounds easiest if space is a constraint.

but if you can just extend the length in the straightest direction with as smooth a "pipe" as possible. i would love to find something flexible with smooth inside. i even thought of using the wind socks, or something similar. but I think they are not air tight, so that would not work well.

good luck and happy growing.

 

[nizmo]

We rigged it up so its flowing out the duct i was talking about so its blowing straight outside now... Much to my surprise, the noise is still there (albeit slightly quieter) so now i am not sure whether the noise of the air flowing out of the duct was even the problem. I made the noise even quiter by putting the fan in the very back corner - away from the walls near the lounge.

My plan is to seal the fan as best as i can inside the room (we're going to build a small insulated box to house the fan) to reduce its noise. Once i've done that, ill have another go a placing the duct back inside and i'll update with how noisy that is. If its still noisy, ill go for larger ducting.

1) Unlike other electrical devices, a closed centrifugal fan - as far as my logic goes - would be fine to cover in insulation, because the device is cooled and gets all its airflow from the air moving though it. Right? The fan housing never gets hot, so it wont matter if its covered in insulation will it?
2) Will adding a carbon filter significantly reduce the fan speed?

 

[420forme]

Try insulated ducting. It reduced the noise a lot with my setup.
Also a filter will reduce flow, by how much I don't know.

 

[BongKong420]

I have my fan sucking the air through a filter and then blowing into a oversized insulated ducting that runs about 10ft and it is almost completely silent. I did get a speed controller to go with it that I havent used on it yet but will put that on and see the difference..... so i would say first if you dont have a filter GET ONE that will help and use the oversized insulated ducting and you will be straight. Ohh and I have seen a lot of people do the idea that you said about housing the fan and youre right it wont over heat it

 

[bloatedcraig]

My whole grow room is in my loft directly above my bed and i am a light sleeper. To make everything quiet what you need is to hang everything from the roof by spring's or bungee cords. My biggest issue was the air pump because a grow DWC, and to fix that i packed a cardboard box with bubblewrap and put the airpump in that then put more bubble wrap on top and hung that from the roof. Will try a get a picture up to show you, it is a site to behold.

I also run it through the night, because of choppers and the fact that it is easier to keep temp's in check. So when i am in bed, 10ft above my head i have a fan, ossilating fan and air pump all running i can not hear a thing.

Spring and bubblewrap is the serect - anything that absorb's vibrations.