I had the audio dropouts from the start in the Norn storyline. Now I’m level 8 in Asura and haven’t experienced it a single time.
I deleted the “Local.dat” file in Guild Wars 2 folder in “My Documents”. It got recreated by the game, although only about 2MB as opposed to around 12MB before.
New installation and only played the Norn up to level 3 before.
Might be worth a try, just do a backup before, in case something goes wrong.