SRAM xx1 1 x 11 drive train very noisy
Even though you mentioned in a comment that the high and low seemed to be adjusted properly, it still sounds to me like the 'L' limit of the rear derailleur is improperly set and does not allow the upper guide pulley to fully move the chain onto your largest cog. 

If this is indeed the case, shift into the largest cog and  adjust the 'L' limit screw (the outermost 3mm adjusting screw) until the center of the upper guide pulley is aligned with the center of the largest cog.

Another possibility is the chain gap is not properly set. The chain gap for the XX1 groupset should be between 12 and 16mm and should be set while the chain is shifted onto the largest cog. You adjust this with the single 3mm adjusting screw located by the derailleur mounting point. Make sure the limit screws are properly adjusted before checking or changing this setting.

The chain gap is the distance between the top of the teeth on the upper guide pulley and the top of the teeth of the largest cog as shown in the following illustration from the User Manual for SRAM 1x11 rear derailleurs:



In the picture above 15 is High set screw and 14 is Low set screw 

If these adjustments do not resolve the issue, bring the bike to the bike shop you purchased it from and have them check it out. My LBS has had several customers (including me) experience issues with the 1x11 cassettes for which the ultimate solution was SRAM sending out replacement cassettes and chains. (Although I think in all of these cases the issue was the chain unexpectedly derailing onto smaller cogs while back pedaling on the largest couple of cogs.)