# Noise dampening...Any ideas?



## LaserKittensGoPewPew (Apr 13, 2007)

Well...I'm going to be working on my pepsi fridge flower box...The 600w hps at the top is going to be cooled by 2 8" 500cfm inline duct fans. They're the simple straight tube ones, not those big ones expensive ones. I was planning on having one blow air through the fixture and over the front of the bulb while the other one sucks all the air out. 

I was wondering what could be done to help dampen the noise they make. I have one in my house by my stove if they sound like that one...Noise is definitely going to be a problem with 2 of them going. Does anyone know any ways to damped the noise or better yet of fans that are quiet but still push a lot of air? Thank's.


----------



## Bubby (Apr 13, 2007)

There aren't many ways to dampen fan noise, as most of the noise comes through the moving air. Be sure to mount the fan on rubber grommets, or anything else that'll absorb vibrations.. hanging it with string works too. There's a few muffling techniques, but it'll reduce your air flow, so I'm not sure if it's worth the effort as you could instead buy a smaller fan or put it on a controller. Basically the idea is to have the air pass through something that'll absorb the sound, like a box lined with foam that makes the air turn 90degrees.
Goodluck!


----------



## tango420 (Apr 14, 2007)

do you really need the 2? sounds like a little overkill to me but i could very well be wrong. all i can suggest for dampening the noise is insulate it with anything soft and mabye rubber around the ducting/fans.


----------



## LaserKittensGoPewPew (Apr 14, 2007)

I'm really not sure if I need the 2 or not. I'm just trying to get the 600w hps temps down as much as possible so my plant's can grow closer to the fixture without burning.


----------



## Bubby (Apr 25, 2007)

*Here's a bit of bathroom reading (har har) for fans*: http://pages.quicksilver.net.nz/geoffm/fan_FAQ.htm#ROT

*Some of the useful information at the very bottom*:

Fan noise is largely dependent on the air velocity through the grilles, so most solutions involve reducing the air speed, and larger ducting and grilles, or multiple inlets usually do this.

Generally, the noise is also proportional to the amount of airflow and the fan speed, If you have problems with a noisy fan or are putting a system in:

1/ Mount the fan towards the end of the duct

2/ use larger ducting to reduce the air velocity, and hence the noise through fittings and grilles

3/ Use a larger fan but turn it slower. This can make a big difference, as the noise varies with the square of the fan tip speed  i.e. RPM. Most fans can be speed controlled, and the makers sell variable speed controllers for their fans.

4/ Use multiple intakes to reduce the air velocity through each grille

5/ If all else fails, try using "acoustic ducting"  you will have to try an air conditioning place for this. Try to find some where the inner core is not perforated into the fibreglass wool around it, so the moisture in the air cannot escape.


----------



## jeffca (Jul 14, 2008)

is it really that loud? i mean wouldn't people just think you have a fan on all day?

how loud is the ballast and the fans really? like does it loud enough for people to be like "that's not a fan, i wonder what that is?"?


----------



## That crazy vancouver guy (Jul 14, 2008)

I don't think yer gunna get an answer, jeffca... the thread is from April of last year...


----------



## jeffca (Jul 14, 2008)

ya but i knew it would be bumped up and i was hopin' someone would read it. like you! lol


----------



## King Bud (Jul 17, 2008)

> 2 8" 500cfm inline duct fans





> is it really that loud? i mean wouldn't people just think you have a fan on all day?


I use a 4inch vortex fan, and the noise bugs the hell out of me.. but maybe I'm more used to living in complete silence.  Even the hum oh my computer sometimes irritates me. It's not that loud, but when noise is an issue, quieter is always better.

Does anyone have experience using a larger centrifugal fan (with respectively larger carbon filter) on a speed controller? Is the change in dB significant?


----------



## papabeach1 (Jul 17, 2008)

yea you will still need 2 duct fans if ya use it for entering air, and for air to exit and all that air flow,  use rubber mounts, you can go to autozone and ask for suspension  mounts race kind, get 8, 4 for each,  mount the duct fans with that mounts on the wall (less vibrant and sound than on floor) that will reduce much better be sure its screw , not nails to mount with  hope that help answer your question


----------



## King Bud (Jul 17, 2008)

Thanks papabeach!
Are these the kind of mounts you're thinking of?: http://www.antivibrationmethodsrubber.co.uk/html/silentfix.html
http://www.antivibrationmethodsrubber.co.uk/html/flanged_high_deflection_mount_.html

Just the kind of thing I was looking for.


----------



## PeaceKiller (Jul 18, 2008)

I have a 6" intake fan @ about 400 cfm. It sounds like a darn vacuum cleaner when I plugged it in. I spent about $30 on a speed controller and have it turned down to the lowest setting. It is sooo much more quiet, and still pushes a sufficient amount of air.


----------



## BuddyLuv (Jul 19, 2008)

King Bud said:
			
		

> I use a 4inch vortex fan, and the noise bugs the hell out of me.. but maybe I'm more used to living in complete silence.  Even the hum oh my computer sometimes irritates me. It's not that loud, but when noise is an issue, quieter is always better.
> 
> Does anyone have experience using a larger centrifugal fan (with respectively larger carbon filter) on a speed controller? Is the change in dB significant?


 
Yes the filter works almost lke a muffler for it.


----------



## I EAT WEED (Mar 11, 2009)

PeaceKiller said:
			
		

> I have a 6" intake fan @ about 400 cfm. It sounds like a darn vacuum cleaner when I plugged it in. I spent about $30 on a speed controller and have it turned down to the lowest setting. It is sooo much more quiet, and still pushes a sufficient amount of air.



Which particular speed controller do you use?  I have heard some make the noise worse (a motor type noise).  

I'm in the same boat.  I would like a nicer inline fan, but I'm worried about the noise.  I will be using a large carbon filter on the "suck" side of the fan to help dampen.


----------



## midibullets (Dec 10, 2009)

Just to add to the info on this thread:   Add ducting to your fans!  If you add ducting to it, the sound level cuts down a TON.  I have 25ft of ducting on each side of my 400cfm can fan, and its MUCH quieter.  the vibration then becomes an issue. so be ready to mount it in a wood box and hang the box on rubber rings from your ceiling, or just mount it in the attic like I did   I also got my 8 outlet air pump to quiet down alot, just put a coiled up 50 foot 1/2" hydroponics hose on the intake nozzle and it helped considerably.


----------



## Smokey Mcpotster (Dec 10, 2009)

I have a 425 or so cfm fan. I cut up a black bungee cord, the kind with hooks on the end. I put that between the mounting bracket and the shelf. I took a large 24x24" box and glued carpet pad to the inside, cut holes for the ducts coming out. Cut the noise by about 50-75%. No vibration noise at all.


----------



## zem (Dec 11, 2009)

Smokey Mcpotster said:
			
		

> I have a 425 or so cfm fan. I cut up a black bungee cord, the kind with hooks on the end. I put that between the mounting bracket and the shelf. I took a large 24x24" box and glued carpet pad to the inside, cut holes for the ducts coming out. Cut the noise by about 50-75%. No vibration noise at all.


you can add insulation material on your ducts and curve them a bit. theres the kind of insulation used to wrap hot-water tanks with it works great. if you really want to eliminate the noise you can make a gypsum board box with insulation in it and pass your insulated duct through it with exit on other end. if you can keep an air gap between your duct and the insulation in the box it's even better. the fan isnt the only noise problem so you might wana insulate your whole room first and then see how much inside work you need to do. check out the gypsum board rockwool fiber sound insulation, it worked great for my drums' room , the door area is usually the weakest points in sound leaks and hardest to insulate, if you need more info on insulation just ask i've insulated a couple of music rooms, cheers


----------



## Budders Keeper (Dec 11, 2009)

I got a bigger fan (elicent) than I needed and mounted the carbon filter on outside of room, last in line. fan hanging with rubber bungies inside room. Room is in garage and from other vside of garage you can't even hear it. Prior to putting filter on outside you could hear my fan from the driveway!


----------

