I've been wondering about this for ages. Hanmin Liao is credited for music in the ending, so I'd assume it is supposed to have sound. But IIRC the ending isn't normally accessible (in emulators anyway) because in one of the later levels, a fireball appears within a block so you can't eat it. So either the game really is unfinished/broken, or there's some kind of copy protection/bad emulation/bad dump at work here... but someone might need to find an original cart and play it on an original MD (or a decent clone, nothing AtGames) before we have the answer.