Acoustic Panel Encapsulation? (Portable Generator Sound Wall)

[Sullivan]

I've got a strange one here.  I started to post it in the finishing section but think it might fit better in home improvement.

I have a portable emergency generator that is very noisy when in use.  I watched a Youtube video where a guy leaned OSB / plywood against his generator for a dramatic noise reduction.  I thought that I would do something similar and build a sound reflecting/absorbing "wall" using acoustic panels instead of plywood.  I have 4 acoustic panels that are 2" thick, 24" wide and 48" long.  They are made of mineral wool and are semi-rigid (think very dense fiberglass batt insulation).

The panels are itchy like fiberglass insulation and I would like to encapsulate them with something. So far I have thought of the following:
1) glue something (thin paneling/plywood, fiberboard, etc.) to both sides.  I'm not sure how well glue would hold or what kind of glue would work best.
2) coat each panel with epoxy - this would get somewhat expensive
3) coat the panels with some sort of clear finish (polyurethane, etc.) or paint

Right now I am leaning towards #3 with polyurethane.  I may do some experimenting today since I already have some poly.

Anyone have any additional ideas or comments to any of my proposals?

[Robert Adams]

It sounds like the material you have is exterior rockwool insulation or a very similar product.  Rockwool does not absorb water so no need to waterproof it. 


        I built an insulated generator years ago to take to the track and it worked well.  In your case with your panels In an affrdable case...

         I would start off with plywood and apply a layer of sound deadening material to it. The material is a butyl based used in cars and basically it turns sound into heat (like all sound absorption materials) but the density makes a big difference. Then I would attach the rock wool to it using screws and plastic caps just like you would when installing external insulation. 
     Then I would cover the rockwool in a material basically like a seat cushion. For a budget build I would use a good quality geo textile. The weed block fabric for flower beds will work as well just don't get the super cheap paper thin stuff. Just swap it around and staple it on. 

           Now you can make brackets to support the panels around the generator and straps to attach one panel to the next to self support them around the generator. Just make sure to have enough air space around the generator for cooling. 

  
            Also if you have nothing else you can use plywood around the generator. Put the plywood at a 45* angle to the ground as this will deflect much of the sound upwards when it hits the plywood. Works great on jobsites with no onsite power.

[Snipe Hunter]

Ok... Instead of building a fire box around it...

Why don't you just put a better muffler on it? The stock pancake mufflers don't really do much more than arrest sparks. I did this with our old Generac 6500kw. I found everything I needed at Tractor Supply, just had to open up the mounting holes a little. Could barely hear it in the house. The muffler was about 3" dia. and 18" long. I hung it from the generator frame with a cheap muffler hanger from the auto parts store. I'd bet I didn't spend $35 for everything. There's a bunch of them on Amazon too.

[Robert Adams]

Ok... Instead of building a fire box around it...

Why don't you just put a better muffler on it? The stock pancake mufflers don't really do much more than arrest sparks. I did this with our old Generac 6500kw. I found everything I needed at Tractor Supply, just had to open up the mounting holes a little. Could barely hear it in the house. The muffler was about 3" dia. and 18" long. I hung it from the generator frame with a cheap muffler hanger from the auto parts store. I'd bet I didn't spend $35 for everything. There's a bunch of them on Amazon too.

    The vast majority of the sound comes from the mechanical noise from the engine itself. Once you put a quiet muffler on it you find that you really haven't accomplished much. BTDT with the first mod on that generator for the track being a small automotive muffler.  Also rock wool isn't combustible as it's made from rocks and if that burns you have way bigger issues in the world to deal with.

         The super quiet generators out there are expensive as the engines are much more expensive to produce as they need to be better balanced made from different materials and on and on. If it were as simple as a muffler and a case with sound deadening material everyone would be doing it.

[Cooler]

Where is this going to be located?  If it is outdoors boxwood hedges do a terrific job of attenuating sound.  If it is indoors, you have to concern yourself with heat build up that could damage the generator.

[Roly]

    The vast majority of the sound comes from the mechanical noise from the engine itself. Once you put a quiet muffler on it you find that you really haven't accomplished much. BTDT with the first mod on that generator for the track being a small automotive muffler.  Also rock wool isn't combustible as it's made from rocks and if that burns you have way bigger issues in the world to deal with.

         The super quiet generators out there are expensive as the engines are much more expensive to produce as they need to be better balanced made from different materials and on and on. If it were as simple as a muffler and a case with sound deadening material everyone would be doing it.

+ 1,  I installed a after market muffler on my generator and while it did quit the exhaust it was amazing how much mechanical noise there was.   As far as the fiberglass just put a open netting over it but be sure and allow for a lot of air flow for cooling.  Roly

[Cooler]

The most effective noise blocker is a berm with a hedge at the top and an acoustic fence.

Again, we don't know exactly where you are placing this.

https://www.acoustiblok.com/2018/07/20/a...gL-R_D_BwE



https://homeguides.sfgate.com/evergreen-...30787.html

[Sullivan]

Thanks for the replies so far.

The generator is located on the back porch (yes, away from doors and windows).  It's a portable generator that I have converted to tri-fuel (gasoline, propane, natural gas) and the location is dictated by the location of the natural gas connection on one side and the tie-in to the transfer switch on the other.  Here's a diagram:


I have researched enough online to understand that most of the noise comes from mechanical sources as opposed to the exhaust - thus the sound reflecting / absorbing "wall".  Since my yard backs up to an open field I am only concerned with the sound coming towards my house - so a wall rather than a box will suffice.

Here are the acoustic mineral wool panels I will be using:



I plan to leave them as panel like as I can for storage purposes and experiment with the configuration that give me the best reflection / absorption results.

The main reason for my original post was to get ideas on best how to encapsulate them to make them less "itchy" and maybe protect them somewhat from damage while in storage.

[Robert Adams]

Yup those are just regular Rockwool exterior insulation panels. Mount them to plywood and wrap with geo textile fabric. It won't inhibit the sound from traveling into the insulation.(Like in my original post) 
       You could really just make a couple panels with legs and stand them up between the generator and the house. 


   Another use of these is for making AC condensers quieter. Build a fence around your condenser (far enough away for airflow obviously) Then wrap the insulation in geo tex and screw it to the inside of your fence. You will be amazed at how much quieter it is being in your back yard. Add a compressor blanket and it will be even better. I need to do this to ours but I need to do some ground work around the area like putting a few feet of gravel from the house out (nothing will grow on the north side in the shade). 
       Also a great thing to do to your neighbors condenser. I really need to do it to our neighbors. The builder used a garbage Payne unit and they are the loudest compressors I have ever heard. Almost like my 60 gallon air compressor running...

       
         Now this reminds me I gotta check out our 8K generator as I haven't started it in a while. Need to get a tri fuel carb for it as well. We bought it because we were loosing power several times a month for hours at a time. Since purchasing it our power doesn't go out as much but I know when it will go out. My battery backups will start to squeal from unstable power then a few seconds later I will hear the fuse pop on a transformer a few streets over. They have changed something though as it used to totally kill our power. Now it's usually just a temporary interruption of less than a minute.   

           I really hate the voltage drop we have here. The run from the house to the pole is 150' and the transformer is on a pole about 500' from there. Not to mention they typically way undersize their wires as they don't care how hot they get. Can't tell you how many houses I see with melted insulators over the crimps because of undersized service conductors and bad crimps. But the elec company doesn't care.

[Sullivan]

I bought this generator following Hurricane Ike when we were without power for 2 weeks.  7,100 watt peak.  Since then it's been a series of small projects.  The year after I bought it I added the tri-fuel kit, the following year I tied into the natural gas and the year after that I added a 6 circuit transfer switch.  Now I'm trying to quiet it down a bit.

I like your idea of the landscape fabric and the plywood - I think I'm going to go with that.

I've downloaded a sound meter app to my phone and plan to play around with different configurations to get the maximum benefit.