Someone else called it a "slow memory leak", whatever that is, that is brought on by the intense strain of a variety of factors such as:

- The Duty Finder
- Fates
- Extended duration of play

So it happens to me rather frequently (at least once a day) because I fall into basically all of those categories. The solution? Restart FFXIV. I've tried Log Out and Exit Game, but those didn't do the trick for me. I had to get back to the square 1 PS3 menu. Now before anyone starts saying that it's not fair to PS3 players or anything like that, please give this young mmo a chance to work out the kinks. Defiance had similar issues with "Ark Falls", which are pretty much the exact same thing in a different genre (some field appears on the map, lots of players converge upon said spot, lots of monsters start spawning, etc) as Fates, and the sound would get wayyyy crazy. It never went "out" for me completely, but it definitely had some serious bugs which I don't see a reason in describing here. All I will say is that Defiance eventually patched something, and it stopped being an issue.

I can only assume that SE will do something similar, eventually, but with the laundry list of other problems they are currently addressing, there's no telling how high or low on the list of priorites the PS3 sound issues are. So when it happens, just tell your friends, FC, whatever, "Hey I'll be back in a few, gotta restart", do so, and waste no more concern on it.