Hey Rovito, First and foremost; do not run your generator in an enclosed space. If you are to run in a sound dampening box of some kind you want to make sure it is well ventilated. you can search how to build sound dampening enclosures on youtube and similar products can be purchased. For those looking to buy I would simply recommend purchasing an INVERTER generator which going to be much quieter than a conventional generator. In addition to being quieter, inverter generators are also compatible with sensitive electronics and will not damage the microprocessors found within. Rovito since you have already bought the inverter and are looking to run it as quietly as possible I would just run an extension cord away from your trailer. Hope this helps somewhat.
All the best,
Dave
http://www.quietpowergenerators.com/