Generator quieting

I've been doing some reading -- always dangerous! -- and thinking about imitating Sound Guy's box. It turns out there is a difference between soundproofing and sound absorbing materials. Soundproofing actually blocks the transmission of sound, like concrete or lead -- drywall is another example. Sound absorbing stuff blocks the reflection of sound -- things like foam or fiberglass insulation.

It seems like there should be a way to combine the two inside a box.

That is as far as my thinking has gotten -- still pondering.