I walked into my apartment the other day to get something from my bedroom. As I walked in - I could hear snoring. The cat. Snoring. It was 2:30 in the afternoon - I figured I'd wake him up and say "hey". So I called his name.
Nothing. Just more snoring.
I clapped my hands (in true power-clap fashion).
Nothing.
So I did the only rational thing I could think to do. I set up photobooth to take a video, went to the kitchen to get a pot and wooden spoon, and then I came back. He woke up after I moved the pot closer to his head. I bet you're thinking - he woke up to the sound - he must be hearing. Well - I'd counter with this - even my Dad (who is profoundly deaf) can hear an ambulance siren when it's but a few feet away. He usually says something like "wow - that must be really loud for you" after it goes on it's siren-y way.
All that to say - the fact that Hern didn't jolt right up says to me - he's pretty deaf. Here is some video proof.