For my LNC2 I soundproofed the area underneath the rudder pedal subfloors only.  This area is basically inaccessible once the floor is installed.  For all other areas of the plane, I plan to evaluate the noise level with an ANR headset.  If I'm not happy then I'll start adding more soundproofing, although I don't expect to need any.  For this reason I will do my initial flights without the interior installed.  (Plus, I expect to be broke at that time....)

I used a single layer of ADC-006, which is a thin foam with aluminum backing, stuck to the inner skin with the peel-and-stick adhesive it comes with.  Over that I put a custom shaped pillow of fiberglass batting with a vapor-proof heat-sealed cover (the vapor barrier is kinda like plastic tissue paper that you seal up with a household iron).  The subfloor goes over that.  If anyone wants more details I can go look at the boxes to get part numbers.  The minimum order was enough for at least two Lancairs, but it's still a small amount of stuff.  My recollection is that I only added about a pound of stuff (both sides combined).

- Rob Wolf