OK - house purchase has fallen through - turns out there were too many illegalities with the proposed purchase so to keep my sanity I'm reverting to finishing a project started a while bask: quietening my generator.
It's a 6 litre turbo charged diesel in a steel box with virtually no internal sound absorbing material - currently I've lifted off the box (2.6m x 1.5m x 1m) to do a bit of welding on rusty bits, and intend to line it before I crane it back on. Currently giving 90dBA @ 1 metre target is to reduce it to 70dBAor so.
Hunting around there seems to be a shortage of suitable materials at a reasonable price. I'm looking for a sandwich construction accoustic foam laminated with either lead foil or other dense material giving at least 32mm thick overall, preferably 45mm. Best so far seems to bebut at a heck of a price.
So if anyone has about 14 sq metres of suitable fireproof, oil proof, rot proof and sound absorbing foam to hand or knows a better source please get in touch.