Yes it's normal. Dev said:
Lol, actually, there's no sound literally because that's the trauma the MC is suffering from. The journey is for him to rediscover his "Sound", through the colours of his life (the LIs). MC is subconsciously blocking/scrambling music specifically. He can still hear sounds just fine. He can still distinguish and identify patterns and origins of sounds, etc. What he hears when he hears music is just noise because the "soul" or "colour" of music is lost to him. He derives no joy nor any emotion out of music.
Music will not be implemented fully until the story has progressed sufficiently for it. However, it makes sense to have music in scenes before the MC was broken. So scenes such as the beginning or any flashbacks should have music. I also think various background sounds/simple tunes will help with the dead silence of the rest of the game. So if I can find anything that works well as ambience, I will add them. This will come after the patch mentioned above. Because I haven't started work on this, I have no idea when this will be ready.