Just to add an oddball install here among the sensible yard of concrete versionsalready mentioned:
I had to move my Metro 6/1 near a shed. Unfortunately the best spot for it already had a small 4" thick concrete pad, and three low masonry walls around it about 5 feet square, and that was obviously not going to work. I didn't want to crack the slab out, or add 24" on top of it (can't truck in a yard or more of concrete now in mud season), so I did the following:
Laid a rubber horse stall mat over the existing slab.
Set two 4-1/2 foot long 9" sq railroad ties on top of the mat.
Poured a 1 foot cross section concrete ledge a few inches in front of the ends of the ties (a 4th wall)
Filled in around the ties and between the 4 walls with 9" of mixed sand and gravel.
Bolted the I beam engine/generator frame across the ties.
Started her up and amazingly quiet. No more ground pounding at all. With the new exhaust system I put in, I actually had a hard time when cranking telling when the first power strokes kicked in so I could remove the hand crank. I haven't pulled full load because the generator isn't connected yet, so things may change. But so far there is a total difference from what she ran like before, even idling.
I used to be able to feel ground vibration from 30 feet away. It also was notable especially when starting, as it came up to governed speed from hand crank speed. Yet I really had a hard time telling when she started firing this time. Just valve ticking and injector clanking. So I'm hopeful she'll be quiet under load as well.
I think the horse pad will protect the 4" slab from being cracked. The rubber pad seems to isolate the block noise from the concrete pad which would otherwise act as a diaphragm. The rubber pad also acts as a spring, while the gravel and sand damp the spring like a shock absorber, I believe. That's my story anyway and I'm sticking with it unless things change.
