I was an electronics engineer myself before flying, and I would echo what Engr and Barret suggest.
Also, I assume you have checked other headsets in the same socket you are using, and your headset in other sockets? It is unlikely that the A380 socket has been miswired by the manufacturer, but not impossible.* It could also be a faulty ACP on the aircraft, so try using your headset with other ACPs.
When you have discounted by substitution all other possible reasons for the noise then the cause must be your headset, and you can start to work through that.
*We were once using an airship for some TV work, and one of its (Porsche flat 6 piston) engines was occasionally misfiring. To cut a long story short, it was found that the coaxial cable feeding the ignition system had been cross-wired on the faulty engine - the outer screen was carrying the signal and the inner conductor was connected to earth. This is the wrong way round and it meant that external interference was affecting the ignition signal, instead of it being shielded from it by an earthed outer screen.
Last edited by Uplinker; 27th Sep 2015 at 15:54.