I commented on this thread when it was active last month, but since @TargasBR posted a link back here bringing up the audio issue I thought I'd give another comment here, folding in an answer regarding communication.
Considering @DaliLama123 's question as to why you'd limit yourself to just in-game chat: the answer is fair play.
There is a pervasive attitude that anything that can be done in-game is not only allowed but to be encouraged, and thus double-gunners and discord chatters abound while many uninterested in exploiting any loophole and quirk in the tech or mechanics winge and whine about "game-breakers." Fair play, however, is not about what can be done but what should be done, and in my experience Brits are generally better at getting this than N. Americans.
Regarding audio, everyone (in my opinion) should just use game-chat, but you can't expect them to. Crews should communicate well, but many players won't. Finding those players who are good at communicating and do it in such a way that it adds to the game and doesn't become just a pirate-skinned Unreal Tournament (my personal benchmark for multiplayer nastiness) is part of the game's challenge.
When I started playing I almost always solo-slooped to learn the game. I've started playing more and more on open-crewed brigantines to try and build my list of friends I'd like to play with more, and in-game communication is a key criterion alongside a sense of fair-play. The next phase is to outfit a galleon with a crew I can really work with...
