Jon,
When I was drag racing a few years back I had 2 generators.
1/ 2.6 kW for power tools compressor etc, this had the standard muffler running into a nice muffler that came of a Suzuki road bike that had been trashed (early GSXR I Think) which helped to cut the noise down quite a bit from the exhaust, but most of the noise ended up being mechanical.
2/ A small suitcase 1.5 kW generator for running the RV and TV/PC etc. The advantage of these is that the plastic moulded case is designed to muffle all mechanical noise, and with it being an "Inverter" type (12V generation feeding into a solid state inverter) it gave a much cleaner mains supply for the PC.
I hate to say it, but have a look on evilBay for ideas.
Neil