The box or enclosure can be constructed of lightweight materials such as aluminum or a heat resistant plastic material. You would line the inside of the enclosure with a closed cell vinyl nitrile foam mat. Quinn, you will need to duct in ventilation into the enclosure, and also be able to duct the exhaust away from the camp site.
Quinn, this will take a small degree of set up, but when you are done, you can put the Honda and the Yamaha campers to shame. It can be done , believe me.
Another method is the little box inside of the big box method which might alleviate you from having to do the ducting of the ventilation or the exhaust if it is done properly.
This method would consist of 2 boxes one large than the other, you would cut out one side of each box and place th smaller box over top of the generator, and then slip the the large box with the same open end directly over top of the smalled box. You would line both box interiors with the closed cell foam. This method allows exhaust removal as well as ventilation into the generator.
The box diagram and muffler is at [url]http://soundproofing.org/infopages/generator.htm
Quinn, I sure hope this gives you a solid plan for quieting your outdoor generator. Thanks for the post.
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