I hear positioning is key for a lot of fighting, especially on Sloop.
If you know where your opponent is and where you are, and gather info on the activities they may be performing, for example, going for a board. You should be able to hear:
- Cannon Firing, but no sound of a cannonball whizzing past/hitting your ship. If you don't hear the cannon, that might mean your opponent's boat is really close to you, and they might sneak a board without having to use a cannon.
- Water splashing, usually accompanied by swimming and (hopefully) the sound of a player climbing up the ladder from the water, as Silent Boarding (intentionally) has been patched.
- Your anchor being dropped. Unless your opponent is extensively clever and kills you before lowering the anchor, you can prepare an attack against the enemy boarder if you hear the anchor drop because that usually means someone that is not your crewmate, is on board and trying to kill you.
That high level of awareness keeps you ready for fights, but that doesn't necessarily mean you will immediately succeed. Give it some practice in learning the sound cues and your defenses against enemies might get stronger!