Might have found a fix for some Mac users on this thread! Seems to have worked for me. (Edited to add: Using a 2020 M1 Macbook pro, Big Sur 11.6)
https://forum.square-enix.com/ffxiv/...to-Mac-players
"Work around:
After a lot of fiddling I discovered a mitigation:
1) Launch "Audio MIDI Setup" (You can find it via Spotlight with Command Space and type Audio MIDI)
2) Select your output device on the left pane
3) Change the audio format for the device *if possible* (EG, this is not possible with HDMI sound out). I've had the following results:
- 44.1khz (default on most devices) - Produces horrendous static/popping in game
- 48khz - Sounds better, but still scratchy
- 88.2khz - Sounds fine at first, but eventually breaks down into static again. (within 30 minutes in my testing)
- 96khz - So far this holds up
Note: You must exit and re-launch the game for the changed setting to affect it."
Switching to 96Khz has worked for me but didn't work for someone else so ymmv, but it's worth a shot.