Greetings. Just to add to this issue. I experienced sound cutting out randomly as well.

I did not have this problem prior to the most recent patch.

After playing for about 6 hours yesterday, the game sound cut out in the middle of Castrum Meridianum.

I did not introduce any changes to hardware or software on my machine neither at the time or prior to the issue happening.

I started up some other applications to test out the sound - the sound in other applications worked without any issues.

After restarting FFXIV the sound returned - but unfortunately you can't just restart FFXIV in the middle of a duty.