Additional Sound proofing ?

[daviesbike]

So the D3 Facelift model had improved sound deadening and then again improved in the second stage facelift with 3G mmi and square fogs ect

they are extraordinarily quiet compared to the standard ones and I was wandering what this is ?

what did they do to reduce noise levels a further 20% that's staggering ?

and can this be done as a retro fit ie DIY secondary insulation install

when I change my interior over to a black Napa one all seats will be out and I was thinking of adding an extra layer to make it super quiet while its out of course .....