air noise question

[babystarbud]

a silencer will help, but again...do you really need a fan that powerfull....how many lights are you running? what wattage?

babystarbud Reviewed by babystarbud on 01-25-2007. air noise question I'm in the process of moving my growroom. We have a good location for the new one, the only problem is the proximity of a couple of open windows (on warm days) about 30 feet from the growroom. My question is concerning exhaust air noise. I'm going to be using a 1500 cfm fan to exhaust warm air through a window opening. The actual window frame itself is going to be boarded up and I'm making a wood box to surround the open window portion. The wood box will have a 12 inch hole cut in it to mount Rating: 5

[houdini]

I'm running 6000w ( 6 lamps) of HPS light in a 25ft. x 25ft. room. I need to empty the room in about 4 minutes and that requires a large fan.

[Garden Knowm]

Hello Houdini...

I had a 2000 CFM fan running with 16 inch ducting ...20 feet... The five OH came to the house one day.. NO problem.. no noise.. nothing...

I mounted the EXHAUST using a bicycle tire and spray foam,.. this reduced the vibration and noise!!!

NOW.. there are other prioblems using such a big fan.. it will fOOk the air flow up in your entire HOUSE.. no more fires in the fire place.. and many doors will get bent over several months of intense suction..

If you use a speed regulator on your fan.. it will probably make more noise at slower speeds..

iloveyou

[trynagethigh]

Man for that kind of setup I would run a duct straight up through the walls through to the attic roof and possibly use a whole house fan (attic fan) to pull the air instead of pushing it out with such great volume. This way you can use a smaller fan pushing (less noise) if you have a nice size one pulling as well. Man thats one big ass grow, 6000? Man I hate to see your light bill? LOL

Tryna

[trynagethigh]

If you can mount the fan in a wooden box of some sort, in other words contain the unit and try wrapping it in dynamat. its a sound deadener that is used mainly for trunks of cars to reduce the noise from high amped car audio.

Tryna

[farmerjz]

Thanks a lot folks for your kind replies. I appreciate the noise INSIDE is a consideration which I can deal with. My biggest concern is the roar of the air as it exits the window. Will a silencer on the o/p of a 1500 cfm fan reduce this so that folk behind windows 30 feet away will not be curious (or pissed off !).

I have the same problem but i solved it i have a furnace blower hooked up 2 my carbon air filter that exits the room im using dryer flex tube than attach 4" PVC piping i cut a 2 liter pop bottle in half and stuck this over 4 " PVC pipe with this its reduced 2 like 1 " this works awesome very very quiet noise reduction what size is ur piping ur u using look at my pics to see i have a small room so if ur using bigger piping u need to reduce the end pipe as small as u can

[farmerjz]

i 4got one pic this is the end with pop bottle cut in half the reduce the noise

[Garden Knowm]

HEY FARM,,,

doesn't that tiny opening cause your fan to work extra hard... and severly reduce its life?

cheers - nice picture

[houdini]

Thanks for the pics and your suggestions, Farmer. I have the same question as Garden Knowm - surely if you reduce the air output like that, the fan is going to be working like hell to push air through the small gap ? Garden Knowm, thanks for yr. advice. Tryna, my light bill is big, but its all relative, really

[babystarbud]

damm thats a big rig lol

cant really give advice, but the replies to this thread have given me a few ideas...

with somthing that size i would think you need to tackle the problem from a few angles...

the noise crated by the fan itself
dynamat is an exellent suggestion, used on the fan unit itself and/or any nearby hard surface to damp down the noise.

vibration from fan mountings/fixtures
rubber fixtures like bike tyres sound a great idea, also use rubber gaskets where any hard joints are made (screws/bolts) to isolate any vibrations as much as you can

exhaust exit and intake noise(air noise)

making the intake exit diameter smaller will indeed strain the fan bearings, maybe a sleved duct will help,if you have a 12 duct, fit a 13" duct over the top of it for some insulation and maybe fill the gap with pillow stuffing or some kind of spray-foam, although i think it dries hard so not too practical for mooving the duct around.

if you can vent into a wall cavity or loft space rather than directly outside it will also act as an acoustic barrier. a loft space full loft insulation will damp the noise down nicely, you could even line the apex of the roof as well as the loft floor.

thats about all i can thinkof lol