Killing the sound of an air duct... got some questions!

[TroubleGuy]

I decided to find alternative ways of silencing my exhaust duct instead of building a giant window box. I'm exploring a couple options and I have some questions before I decide on one... Some might seem dumb, but like I said, I'm exploring a few options... the more of these I can get answered the better off I'll be. I've looked around but can't find anything specific enough. I've taken some ideas from the ways ducts are silenced in recording studios.


I'll just list them off instead of typing a ton...

1. Does insulated ducting REALLY help that much?


For a small box at the end of the duct...

2. Will "egg carton" foam mold in 70-90 degree temps and 30% - 60% humidity?
3. If so, will regular egg cartons reduce noise?
4. Will styrofoam insulation boards reduce sound if a box at the end of the duct is lined with it and small slots are made to allow the exhaust air to escape? (see pic below)

^^^replace fiberglass with that egg carton foam or anything else mentioned above


For a duct muffler/silencer...

5. Would a thick cardboard box filled with insulation or "quilt batting" (quilt filler) work?
6. Will either of those mold when exposed to the same temps & humidity mentioned above?


Hope to get some answers soon so I can get to work on this.

Thanks!

 

[Philosophelon]

I always build my own duct mufflers, cuz I make them bigger than the ones you can buy. I use hardware cloth to keep the insulation from impeding airflow, and then wrap the hardware cloth with fiberglass insulation, and then use a vapor barrier around the outside (e.g. rigid ducting, PVC, a garbage can, etc.). Never had any mold problems, but I don't exhaust humid air.

Here are some DIY duct muffler links.

http://www.icmag.com/ic/showthread.php?t=42646

http://www.icmag.com/ic/showthread.php?t=65345

 

[TroubleGuy]

Actually my humidity is only at 30% and the highest it's ever been is 33%... I'm just thinking should it get higher (I want it between 40-60% as that's the best for flowering plants) I don't want mold issues.

I saw those DIY topics, just don't want a garbage can hanging in my room. The other one might work, I'll have to take a trip to Home Depot cause I have none of the required items for that other one.

I'd like to build something I haven't seen another grower build though...I'm all about innovation Thinking I'll at least try this other idea I have though, if it doesn't pan out I'll follow someone else's example.

 

[rustymetal]

Most of the whooshing noise in the vent is because of the air hitting on the ridges in the flexible ducting. I use flat duct, as well as carbon filter on the intake. The only noise (on mine) really is where the air comes out.

I would not recommend humidity above 40% during flowering. I have had a whole harvest of bud rot because of humidity above 50%.

 

[TroubleGuy]

Hey, as long as humidity in the 30s doesn't affect my yield, I can keep it that way.

The only noise I hear aside from the fan itself is the whooshing as it exits the duct...kinda why I'm looking at insulated enclosures as a fix for it I'll get something thrown together and see what happens.

 

[messn'n'gommin']

Something to consider.



Namaste, mess

 

[Philosophelon]

I saw those DIY topics, just don't want a garbage can hanging in my room.

Lol, I can't bring myself to use a muffler the size of my res either. I've never actually used a garbage can, but if I was super-worried about exhaust noise I bet it'd work well.

I make them by attaching 1/4" machine cloth (metal mesh with 1/4" square holes) to the inside rim of the small end of 2 reducers, say 8" to 10" for example, then wrap that with insulation. Then cover that with 10" ducting, and caulk everything to seal it. In the example you would have made an 8" muffler, as the machine cloth forms an 8" duct inside the insulation and 10" rigid duct.

I don't know if that made sense, let me know if you want me to draw it for ya.

 

[Philosophelon]

Here is a drawing of what I just described. It might be more confusing than the aforementioned explanation, as I suck major balls at drawing.

 

[Calimed]

I'm working on lowering my fan noise at the moment as well. I picked up some 6 inch duct insulation from the hardware store, and wrapped a couple packages of it around my fan. It worked wonders (much quieter) and now looks like a silver egg.

 

[ben ttech]

duct insulation is great...
but a trick i learned from a drummer tuning a head is quite useful...

whatever situation your staring at that is making noise you want to change...
take a thumb and start pressing it against the parts all over them...

you will notice the character of the noise their making changes given the slight pressure...

a drummer will do this with a drum head and when hes found the more ideal tone he will add a piece of adhesive tape to that place on the head...

you can put a sizable dent in the sound a given duct or motor is radiating...
by hindering the offending vibrations sweet spot...

which your thumb pressures investigation will reveal rather quickly...

in the case of ducting...
instead of adding tape to the spot...

ive dabbed on some epoxy and attached a cord...
which i then drew tight to something nearby after it had set...

amazing how much of the top end effect of unwanted sound you can kill this way...