BGE "Emerald" Series? We had a BFA that looked like a BGE and our engine mounts were collapsed. That transmitted vibration which translated to noise, throughout the coach. I lined the genny compartment with insulation board, don't know how much hit helped. Nor sure fiberglass is the correct medium for sound suppression. Foam board might be better.
For the neighbors, a folding three-sided "box" of foam board could do a lot to contain the noise.
BFA and BGE are twin-cylinder 1800-RPM machines. We now have a 4KY Microlite that's single-cylinder 3600-RPM. It may be "quieter" in dBA terms, but I find its tone more annoying.