We're restoring two Navy static display jets in one of the old base hangars, an immense structure built mostly out of planks and sheets of echo multipier. The building is dead, no power, no water (it will be demolished at some future date not yet ascertained) so we're running a generator borrowed from a Navy museum, a generator built before noise was a recognized hazardous substance (and substance it is, in that reverberation chamber of a hangar, loud enough to stand on). We need to build a soundproof enclosure around the generator so we can talk to each other and get rid of the earplugs. What's the best approach? A simple structure of 2 x 4s with gypsum board mounted internally on noise damping standoffs? Adding additional batting/layering of soundproofing material (and what type)? Can it be done for less than $500? Would enclosing only the top & three sides of the generator be effective (enclosing the 4th side is problematic). How large could cutouts be in the enclosure for access to the throttle, reading the output gauges and to the receptacles? Thanks for any advice!
Build a basic frame with 6" horizontal plates at the top and bottom, stagger the vertical 2X4's so that the gypsum board on one side does not touch the other. Regular house construction where gypsum board on both sides are nailed into the same 2X4 actually transmits the sound quite nicely to the other side. When you are ready to mount the gypsum board go down to the hardware store and ask the clerk for ah hell I forgot. Give me a minute or two and I'll draw it up for you and try to find the material. Be right back . . .
Here's a picture of how the wall should be constructed . . . The little spacers between the gypsum board and the studs are rubber or some other kind of soundproofing material usually shaped like a washer. That should do it and probably keep the cost way down. If'n the generator isn't to big you might be able to go to construction sites and tell them what you're doing and ask for the scrap material, Might even build it for free that way! lane: p.s. oops almost forgot, the fourth side could be build like a styrofoam cooler top and fit into place, that way you could just remove the entire side to gain access to the generator. Don't forget to cut a couple of "U" shaped holes in the bottom and run hoses outside for exhaust and air.
You've probably thought of this, so I'll ask why the generator can't be located outside. A fourth wall, even if it's not connected to the other three, would still absorb some sound, and keep it from reflecting off all the other walls. For cheap and simple sound insulation, have the gang start collecting egg cartons. I've seen them used with good results in a basement band room - they're ugly, but effective.
It'd be stolen in less than 24 hours. It was stored outside in a fenced compound before we got it and thieves had already chopped out all copper wiring, which we had to replace. Even inside the hangar losing the wiring again is a risk, as "copper miners" have rappeled down into the hangar at night from the roof (a 42 foot free rappel) to rip out the old building's wiring. When we brought the A7 inside the 1st thing we did was take off the external ordnance, 8 practice bombs & two missiles, and lock them inside a windowless room to prevent them showing up on eBay.
Then put the generator into the same room, run exhaust and air hoses outside and insulate the walls that face the interior. Then go to the pound and adopt the meanest nastiest looking dog you can find, treat him nice, feed him and care for him but let him live in the hangar and at night leave his "Kibbles and Bits" next to the most valuable thing in the hangar.
Assuming that you can design in proper ventilation both for combustion air as well as cooling (ducted fans etc) build the interior of the surround structure out of irregular shaped material. One of the best sound absorbing materials is cardboard egg crates. If you can get ahold of a few hundred from some commercial kitchen, staple them to the interior walls, ceiling and floor. (Be aware of fire protection however!. Gypsum wall board is a bad choice as it has a very high sound transmittance. You can buy from any good lumber yard, 4x8 sheets of fuzz board, 1/2" thick. Use this at least on the inside of your surround, and ideally on the out side as well. Stagger your studs as TREB has suggested, and add fiberglass in between. Isolate the generator on as thick a rubber pad as you can from the floor. If this is a big industrial genny, find a good piece of industrial rubber to put under the genny. (assuming it is on a concrete floor) If you are on a framed floor, you are pretty much sunk. Just make sure that what ever you do, you pay attention to flameability if you care, as most of the products I mentioned are not fire rated. If you have to, for some inspection standard, you can cover most of these products (except the egg crate) with 5/8" fire rated GWB. If it is a temporary structure with no one living in it,, I wouldn't bother. Also insulate the air intake and exhaust ducts with fuzz board and or egg crate as the ducting will transmit a lot of sound. Icarus The reason the egg cartons work so well is they are soft so they absorb much sound, bur more importantly they are irregular shaped so that they bounce the sound back on themselves. The other thing you can do is hang a number of thick blankets and or moving quilts a few inches off the ceiling and the walls. Make the enclosure as small as practicable. We made a recording studio out of a vacant dorm room once, using egg crate and you practically couldn't hear the band out side!
Poly filler(quilts) is what I would put in a speaker enclosure to absorb, or paper backed insulation, stapled. I'd make two enclosures with an open side, one on top of the other(2" air clearance) , openings staggered, on top of something, rubber mat?
The generator is on rubber tires - is a rubber mat still necessary? I like the egg-carton idea - it's cheap & sounds effective. Doing anything to the hangar itself is out of the question. The ceiling is 42 feet above us, the bay we're in is about an acre in size. Also, it's still property of the Navy & although dead and unmaintained we are not free to remove so much as a nail without clearances. I forgot to mention that another important reason we need the generator adjacent to us is that it is our lighting. It's got a 4 1000W lamp tower and we need every lumen it generates. So we can't move it away. Funny how something that obvious slips your mind when looking in close detail at a problem. Thanks very much all for the advice thus far!
I'm suggesting that you make a small room, 4 wall and a ceiling surrounding the genny, making sure you have proper ventilation. Icarus
And I'm suggesting you stack two rooms with a wall missing on each for ventilation, rubber tyres are good for vibration control, putting them on a mat would control sound also.
Personally, why are you thinking in the stone age Bra... a soundproof box isn't the best solution IMHO I think for <$500 you could make an active noise cancellation device... Think like the folks do at Bose... only a little larger, and you will get the idea I'm sure APK. [ame=http://en.wikipedia.org/wiki/Noise_cancelling]Active noise control - Wikipedia, the free encyclopedia[/ame]
The light's probably much better outside the hangar, and then you wouldn't need a noisy, polluting generator. Perhaps when the aircraft are sufficiently re-assembled, they could be rolled outside on a cradle to be worked on in the sunshine, and rolled back in at night?
Hmmm. I'll scope it out - I thought that was possible only with headsets, but I see I'm wrong about that. Thanks!
