Suggestions for sound insulation.

13 years ago

I recently put the finishing touches on a 'Cold' greenhouse for rain forest orchids and want to increase the humidity. Instead of the conventional plug-in hydrofogger I bought a rebuilt Carel MC 2000 atomizing nozzle which can put out a ton of water at 10 micron droplet size. It needs RO water delivered to it at a low pressure, 2 to 4 psi, no problem, a container of water at 7' height level is doing that, keeps full with a toilet tank water level device.

Air needs to be delivered at 10 to 40 psi. An air compressor does that. Increase the air pressure and more water is delivered up to 15 lbs/hr. Droplet size is not affected by that. The lower the water pressure, the smaller the droplet size, by raisinng or lowering the nozzle in relation to the water source, droplet size can be controled. All this is good, the nozzle was $100 on Ebay, a 5HP 20 gal compressor was $100 on Craig List, all the pieces are in play for very minimal cost.

It works great, the compressor takes 5 minutes to fill the tank to 120psi, the nozzle bleeding the air at 15psi setting drains it down to 100psi in 5 minutes. This restarts the motor which needs about 30 seconds to bring the pressure back to 120psi. Without any noise protection it sounds like Attila the Hun is about to attack but the green house feels like the rain forest in Costa Rica. So every 5 minutes a deafening compressor goes on for 30 seconds, just the kind of lullaby you want to wake up to on a Sunday morning. My neighbors told me that I could stay but the compressor had to go.

I got some QuietRock soundproof drywall, item #525 to be exact, and built a box just for the motor which sits in a corner of the garage inside that box. The noise is significantly reduced and I can run it during reasonable daylight hours. It is still too loud to run it 24 hrs/day.

Does anyone have any experience soundproofing a 5 HP oil less compressor? There is a less expensive sound absorbing particle board available from HD, they also sell sheets of Styrofoam, 2' x 4' x 2". I was planning to add layers of these 2 items around the box like layers of an onion. In addition there are some sound absorbing tile (ceiling tile, I believe) one could add. Someone also suggested to create a 6" wall of sand around the whole thing. Another idea was to throw a sleeping bag over it. I also have a ton of 1' cement blocks, (HD blocks) I could build an igloo over the top of the contraption. Unless I get some intelligent advice, I just plan to add layer upon layer of stuff until the noise level is acceptable.

Any suggestions would be appreciated.

Nick

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Comments (10)

dcarch7 d c f l a s h 7 @ y a h o o . c o m
13 years ago
Post a picture of the setup and the compressor first.

dcarch
orchidnick
Original Author
13 years ago
Sorry, no pictures. The motor separates from the tank so the only thing that needs to be insulated is a round 8" x 12" electric motor with a small fist sized air pump on top of it.

The 20 gallon tank, which has the controls on top of it, can sit apart from the motor. It, of course, does not make noise.

Nick
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orchidnick
Original Author
13 years ago
I built a second layer of sound dampening particle board from HD today, this had little benefit.

I think I will bury the thing in the ground, housed in a 30 gallon tote box with at least a foot of dirt on top of it. A snorkel of 1 1/2" PVC pipe along with an air pump, going while the compressor is on, should deliver fresh air into the box. This is the set up I have started to build.

Comments?

Nick
penfold2
13 years ago
More mass will help. Concrete, earth, sand, etc will perform better than wood or foam because sound waves need more energy to vibrate a larger mass. Also, decoupling the pump from the floor by sitting it on a soft pad (like foam or rubber) will help since the pad will prevent vibrations from being directly transmitted to a rigid floor. Buried in the ground, this may not be much of an issue. A snorkel will allow some sound to pass, but is necessary in this case. I wouldn't bother with an air pump unless it's serving some other purpose. The compressor will draw in air on its own, and a typical diaphragm air pump probably couldn't keep up with a compressor anyways.
orchidnick
Original Author
13 years ago
Thanbks for the advice, it's going in the ground with 1' of dirt on top. 1 1/2" snorkle and 1 1/2" air pump. This is a fairly strong pump that I used a long time ago with a koi pond set up. It's a rotary pump of 1/3 HP and puts pout some serious air.

I'm using it for 2 reasons:

1) It's been collecting dust in the garagew, may as well put it to use.

2) To dissipate heat from the motor.

Thanks, Nick
dcarch7 d c f l a s h 7 @ y a h o o . c o m
13 years ago
Really a picture will help.

There is a big difference between insulation and isolation, depending on situation.

For every 100% of sound power improvement there is only a 3 db of perceptable improve to the human ears.

dcarch
penfold2
13 years ago
Ok, a 1/3 HP air pump is much more than I was thinking of, and should provide good air exchange. I think a small muffin fan would be more efficient, but if the pump works for your situation, go for it.

I am planning on building a small evaporative pad cooler for my greenhouse, and will probably use a similar elevated RO tank + float valve to keep it topped up. Do you find the mister lowers the temperature significantly, or is it mainly for humidity?
orchidnick
Original Author
13 years ago
Before I had the humidity system I used to hose the green house down with a gardenhose, this defunitly dropped the temp by a few gegrees. Now the nozzle keeps the humidity high and it is hard to tell what actual effect it has on temp.

As long as there is oportunity for evaporation there will be cooling. I have a swamp cooler going nearly all day long, the humidity system adds to the humidity level and probably drops the overall temp by 2 or 3 degrees.

I built the green house with 6 mil agricultural plastic, which gives 12% light reduction and then added 50% shadecloth on top. For Southern California this was not enough and near the beginning of July I added an aditional layer of 30% Aluminet which made a noticable difference.

Despite these 3 layers, standing inside, it still is not comfortable to look directly at the sun so plenty of light is getting through.

Nick
orchidnick
Original Author
13 years ago
I'm 70 and when I feel like working, I usually lie down until the feeling passes. This morning I dug 1/2 the necessary hole, discovering in the process that digging a hole in the ground is no longer my favorite activity. I will have to do some serious resting this afternoon.

Nick
orchidnick
Original Author
13 years ago
My curiosity got the better of me so I finished the job. The beast is tamed but it is amazing how much noise these guys make. With all that insulation and buried in the ground it is still very much noticeable. About like a dryer, no more, the neighbors won't know when it's on. Anyone inside the greenhouse will definitely hear it but they are there at their discretion so no problem. I'll take it off the timer and leave it on 24/7.

The only thing I worry about is heat entrapment, but that little air pump will be on the same circuit as the compressor so it should hopefully blow out the heat.

Mission accomplished, I hope. I'll breathe easier at the end of a 95F day.

Nick

Suggestions for sound insulation.

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Suggestions for sound insulation.

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dcarch7 d c f l a s h 7 @ y a h o o . c o m

orchidnickOriginal Author

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