Your welcome Philippe!
I went to an aircraft soundproofing workshop at OSH. The presenter was from
PegasusAeroMarine.com. He had a lot of good tips about soundproofing your aircraft. They have many good articles on aircraft soundproofing on their website. After I went to the workshop, I toured the A-380 and saw some of the same stuff he talked about. I am going to get the vinyl nitrile sheets with self-adhesive back from
Aircraft Spruce and cover every interior (sheet metal) surface inside the cockpit area. 1/4 inch in the baggage area and 1/2 inch in the forward area. Every since I lined the inside of my air compressor box with foam rubber, I've become a believer in it's noise reduction capability.
Have a goodun!