if it sounds like ouch (e.g. stonecrusher, ravenous assault), it's probably a buster. if it also sounds spooky, it might be a magical buster (shadowflame). sometimes se is a troll and makes magical busters that sound physical (ravenous assault) but you don't have to worry about that much unless you play drk or to an extent gnb

occasionally you'll have bosses with few to no busters per say, but heavy autos that chunk you as well, then you just have to memorize when they go out