Been meaning to build one, not for noise primarily for storm coverage. Because, it will likely be raining/storming when I need one. More than once, I've just thrown a small sheet of plywood on top. And then curse the next time I do it again in the rain. I have seen some interesting designs for noise abatement though. I hear they can get pretty smoky, so venting is an issue and incorporated in some of the designs. The engine also needs to breathe.