Stealth is the Word - Silencing exhaust fans

[L84AD8]

Hi all

As the title suggests I'm in the middle of planning/setting up my 2nd ever grow room. I've worked out of a wardrobe previously (pictured below) to much success. Considering how compact/micro it was it produced 1oz on avg per cycle on just 150w&200w CFLs. I've run aboutabout half a dozen or so cycles in there. Strains of worthy of mention would be Northern Lights and Blue Dream

Setup - 4" Fan, CanFilter,150w Veg CFL, 200w Flower CFL, Coco Coir/Chem

I've since moved out and into my own place and have a roughly 1m2 area to work with. Changing over however to 100% organic, Lumatek 200 Attis, 6" Phresh Hyperfan V2 w/controller.

My question for the masses is how can I silence the exhaust? the silencer that came with the Fan really does quite minimal. Everythings contained inside but the ducting is vented upwards through the roof of the room i'd just built. Even at 10% there's audible hum that is reverbing through the ducting at the top. The whole room bar the door is double walled/insulated and does a great job muffling sound coming outward from the room

Some thoughts that come to mind include
- Acoustic Ducting
- Acoustic Hose Clamps
- 2nd Filter on the outtake side? my setup currently is FILTER > ELBOW ducting > PHRESH Fan > Ducting/vent through the roof

My first post on here. Look forward to getting to know the forums =D

 

[cannabineer]

Hi all

As the title suggests I'm in the middle of planning/setting up my 2nd ever grow room. I've worked out of a wardrobe previously (pictured below) to much success. Considering how compact/micro it was it produced 1oz on avg per cycle on just 150w&200w CFLs. I've run aboutabout half a dozen or so cycles in there. Strains of worthy of mention would be Northern Lights and Blue Dream

View attachment 4777344View attachment 4777345View attachment 4777346 Setup - 4" Fan, CanFilter,150w Veg CFL, 200w Flower CFL, Coco Coir/Chem

I've since moved out and into my own place and have a roughly 1m2 area to work with. Changing over however to 100% organic, Lumatek 200 Attis, 6" Phresh Hyperfan V2 w/controller.

My question for the masses is how can I silence the exhaust? the silencer that came with the Fan really does quite minimal. Everythings contained inside but the ducting is vented upwards through the roof of the room i'd just built. Even at 10% there's audible hum that is reverbing through the ducting at the top. The whole room bar the door is double walled/insulated and does a great job muffling sound coming outward from the room

Some thoughts that come to mind include
- Acoustic Ducting
- Acoustic Hose Clamps
- 2nd Filter on the outtake side? my setup currently is FILTER > ELBOW ducting > PHRESH Fan > Ducting/vent through the roof

My first post on here. Look forward to getting to know the forums =D

I built an S-box. I was running a 4” so I made a box 12 wide and 24 long. Down up down with thin foam (open cell) on the vertical and end surfaces.
Light and sound were zeroed.

 

[L84AD8]

great idea! ive read a few ways to do DIY box enclosures and by all accounts sounds like they're better than the metal silencers available??

how fast do you run your 4" ?

 

[CrvenaZvezda]

While I dont have a need to silence my intake/exhaust I’m quite curious what can be done in the event that this is necessary. I run 8 inch for exhaust and 4 inch for intake and during the summer the 8 inch running at full speed and moving 700cfm can be quite loud.

 

[Renfro]

The best way to make your exhaust system silent is to oversize the fan and run it at a greatly reduced speed. This allows you to move the same amount of air without hearing the fan noise.

If using a fan that runs on AC current I suggest a variac as many of the cheap speed controls will actually make the motor groan at reduced speeds. This is due to the fact the sine wave is beat all to hell.

As an example I have a 2x4 tent that has a 10 inch vortex on the exhaust but I run it at a greatly reduced speed, you can't even hear the fan running.

 

[cobshopgrow]

oh yeah oversize the fan and run low rpm.
also this stuff is quite effective as silencer.

 

[lazaah]

A few years back I had a whooshy exhaust duct. I half filled a bucket with packing peanuts, drilled a bunch of holes in the lid, and used a hole saw to put an entry for the ducting. It was surprisingly effective in reducing the outlet whoosh and fan noise at the duct end

 

[Rurumo]

Lots of good advice here, I agree with Renfro, get a big fan and run it at a lower speed. The duct mufflers really do help too if kept close to the fan, as does the sound reducing ducting, which just seems to have extra layers of material. Besides those things, you'll have to build a box.

 

[L84AD8]

While I dont have a need to silence my intake/exhaust I’m quite curious what can be done in the event that this is necessary. I run 8 inch for exhaust and 4 inch for intake and during the summer the 8 inch running at full speed and moving 700cfm can be quite loud.

What're your CFM requirements? my total space is about 80 cubic feet. With a built in silencer to the fan and carbon filter the current setup is rated for 330CFM. At 10% on the controller it came with - it was almost at the point I would accept but still would hum along. but 10% is only 33 CFM I need it to be dead silent

 

[L84AD8]

The best way to make your exhaust system silent is to oversize the fan and run it at a greatly reduced speed. This allows you to move the same amount of air without hearing the fan noise.

If using a fan that runs on AC current I suggest a variac as many of the cheap speed controls will actually make the motor groan at reduced speeds. This is due to the fact the sine wave is beat all to hell.

As an example I have a 2x4 tent that has a 10 inch vortex on the exhaust but I run it at a greatly reduced speed, you can't even hear the fan running.

Interesting. Almost similiar area im working with. What's your CFM minimum requirements vs what the 10" CFM rating?

To run the 6" at an acceptable sound level means its running at about 10-15% which is only 33-49CFM. Short of the minimum of 80. Curious to hear if the 10" would work for my setup? do you running a 10" filter as well?

 

[L84AD8]

A few years back I had a whooshy exhaust duct. I half filled a bucket with packing peanuts, drilled a bunch of holes in the lid, and used a hole saw to put an entry for the ducting. It was surprisingly effective in reducing the outlet whoosh and fan noise at the duct end

Nice. Wondering if introducing a 2nd can filter on the outlet could act the same as your DIYjob

 

[Star Dog]

Another vote for a larger fan than required turned down with a variac or digital comp speed controller.

I can maintain my temps and humidity running my fan at around 30% and it almost silent, I've got dodgy neighbours I couldn't afford them to hear it through the night.

Idk about dc units but a variac gives you the option of wiring it through a relay with varying idle and cooling speeds.

 

[MyMommaMakesArmyBoots]

oh yeah oversize the fan and run low rpm.
also this stuff is quite effective as silencer.

Also great if you have to bring in Canadian/northern winter air, stops condesation dripping.

 

[JoeBlow5823]

To run the 6" at an acceptable sound level means its running at about 10-15% which is only 33-49CFM. Short of the minimum of 80. Curious to hear if the 10" would work for my setup? do you running a 10" filter as well?

Exactly what fan speed controller are you running? The % of power you are sending to the fan does not have a direct linear correlation with CFM's. Like for example a 600cfm fan that takes 200w at full power will likely move about 400cfm if you run it at 100w (50%). But with that same setup adding a carbon filter will dorp your CFMs down anywhere from 200-300. Carbon filter size and quality plays a big role in how much it reduces air flow. How do you know you are at 10-15%?

 

[Renfro]

Interesting. Almost similiar area im working with. What's your CFM minimum requirements vs what the 10" CFM rating?

To run the 6" at an acceptable sound level means its running at about 10-15% which is only 33-49CFM. Short of the minimum of 80. Curious to hear if the 10" would work for my setup? do you running a 10" filter as well?

all I can say is that on a very low setting of <50 volts it tries to turn the tent inside out silently.

 

[L84AD8]

Exactly what fan speed controller are you running? The % of power you are sending to the fan does not have a direct linear correlation with CFM's. Like for example a 600cfm fan that takes 200w at full power will likely move about 400cfm if you run it at 100w (50%). But with that same setup adding a carbon filter will dorp your CFMs down anywhere from 200-300. Carbon filter size and quality plays a big role in how much it reduces air flow. How do you know you are at 10-15%?

Hi Joe

speed controller is the default one the Phresh EC fans came with - Link . Just reading off the dial

 

[Cookie Rider]

The can silencers mounted on my fans work well.
At 70-80% speed with a 6" intake and 6" exhaust I have to feel my exhaust to see if it's on.
Fans all hung w rubber straps.
I'd love to go 8-10" for efficiency.

 

[JoeBlow5823]

Hi Joe

speed controller is the default one the Phresh EC fans came with - Link . Just reading off the dial

Reading off the dial likely isnt telling you anything useful... Most of those speed controllers have a minimum speed that is about 50% of what the fan can do. You have to plug it into a kill-a-watt meter to see what % of power its actually at.

 

[L84AD8]

Reading off the dial likely isnt telling you anything useful... Most of those speed controllers have a minimum speed that is about 50% of what the fan can do. You have to plug it into a kill-a-watt meter to see what % of power its actually at.

Might be a hard one. I live in aus and dont have access to the meter - quick google doesnt show any aussie ones I can acces readily annoyingly enough

 

[JoeBlow5823]

ill give that a go. thanks mate

Yeah being a 6'' fan max draw is probably like 150w. So then 15w=10%, 30w=20% and so on.