insulated sound dampening box for inline fan

hello there ic!
i looked around for a while and i havent seen anything yet that resembles this. anyway im not taking credit for this design or anything just thought id pass it along. its pretty common sense. ive found that it cuts down noise a good bit. suspend from some heavy bungies or that thick rubber stuff for shocks is what ill be using. have at thee!

i used half inch MDF for my box. 3/4 seemed like it would be much too heavy to hang from ceiling. i found a guy at my local flea market that sells this 2 inch thick foam stuff. i dont know what its supposed to be for, he told me it floated when i bought it. im pretty sure he makes it somehow. im using the leftover to cover the window. no brainer.

so you guys can see where this is going now eh?

measure your foam and fan, cut your box out. cut your holes, make sure you off set for your fan feet. i left mine on anyway.


i cut my foam accordingly with a utility knife, was able to use the hole saw for the cutouts. decided not to use any glue and that was a good call.

i decided to tuck the power cord through the main exhaust since i had some breathing room. taped a couple feet of duct to one end and worked my fan on in. i had to cut out the two side panels in the middle some.


worked my ductwork onto the other side and sealed it up. made a note of the top and presto!


please excuse the phone pics. and please note that this is the first one of these ive made.(made two actually) test ran for a while and it works great. as of this posting im unaware of any long term type stuff. will change post if it catches on fire or something.

A few points, if you don't mind:

1. Dedicated acoustic foam is fire-retardant. The thicker the foam, the lower (in frequency) is its absorption. IOW, if the noise is a low-frequency hum, one would need ~6" thick foam.

2. The bulk of the noise suppression is provided by the enclosure. If it's not sufficient, meaning, the fan is still too loud, there are two factors to consider - is it the vibration caused by the fan that's driving the noise and/or the noise of the fan, itself? Vibration suppression can be handled with a Butyl-based automotive deadening material. The Butyl-based part is important, as most are asphalt-based coupled to a very thin foul layer - essentially useless. If the noise is caused by the sound of the fan, mass-loaded vinyl, seamlessly covering the internal area will kill the bulk of the sound. The MLV has to be installed in such a way, as to provide a gapless barrier. Typically, its edged overlay, and are glued together If anyone is interested, I can link the materials. HTH

3. I really like how you configured the box.

Simon

insulated sound dampening box for inline fan

Looks good liquidmaco, it's amazing what you can accomplish with a bong load, a trip to the home improvement store, some power tools, and some old fashion stoner ingenuity. You mentioned hanging the box. How are you planning to hang it? (eye hooks, bungee cords?) If you plan to keep the box on the floor, you want to make sure to prevent any of the remaining vibrations from spreading to the floor. A layer of rubber (such as one from a rubber mat or even the rubber pedestals like on the bottom of some ballasts) will help to defer the vibrations. The prototype looks good and I'm sure you can make an even better one with a bit more practice.

simon- thanks for the input and tips. id appreciate it if youd post those links so i can check that stuff out. i can easily change out the baffling in the boxes. they work good but could definitely be better. ive got six inch eco supremes in there and they arent exactly whispering. gonna dial down some if temps allow. but all in all id say worth the time and money invested . im curious about how much this auto stuff is.
gs - thanks man! right you are. i am indeed hanging them from a tent and a ceiling. i might just chain them temp. style until i find something im comfortable with. didnt see any bungees id be ok with screws and vibrations and all. whatever i pick im going to wrap it all the way around the bottom for the most strength.

Yeah that looks sweet! From what I've gathered checking out insulated fans, many are suspended inside the box with rubber bands. Thick, durable, and only little flexing types, that is. The fan itself doesn't touch the box at all, it's the vibration one gotta look out for in my experience. An insulation box with a floating fan and some insulation with really high mass could be the ticket here, and of course proper damping/insulation for air flow in the air ducts and and their openings. The box itself should be made of as thick mdf as possible, but the weight factor forces one to compromise. Also, all seams of the box should really be glued and screwed airtight but that's also problematic, I wouldn't wanna cut a box open for maintenance.
Really nice box you got there, makes me wanna get down to some d.i.y right away.

thank you sir. the limiting factors for me were weight and size. my initial plan was to glue and screw with 3/4 but my buddy talked me out of it. im sure glad he did. if i had glued even the assembly would have been more troublesome. not to mention down the road..i still cant find any suitable rubber straps around here. ill have to order some off the nets i guess. until then im stuck with chain.hanging everything today, well see how she goes.