Just now I had to ask him to turn the volume on the TV down as I couldn't hear my music (I'm wearing headphones) and he got really snippy with me. If I go on the computer after him I have to check the volume because he turns it up to 100 (while he's wearing headphones.) I can't have it too loud or it hurts my ears, I have the volume between 30 and 40, although if everyone else is out it goes up to 50. We also wear different types oh headphones, which I think is relevant, he has in-ear ones and I prefer on-ear because the other kind irritate my ears.
Also, yesterday while I was trying to watch TV he was watching a YouTube video on full volume, again when I asked him to turn it down he got snippy.
I told him I think he needs his hearing tested and he said it's fine, he just likes things loud. 
I'm thinking if he carries on like this he's going to permanently damage his hearing. I think mine isn't that great and I suffer a lot from ear infections, but I don't need things that loud.