Responses

well it might be because he can't hear that he doesn't want to speak because he can't hear how loud he is speaking and so he might fear that he will annoy others (● ̄(エ) ̄●)

Yes. There are different ways to think about that... Would've been nice to have a short explanation to that (just a panel would've been enough)
If he only lost his hearing a year ago he should still be able to speak. It's only when children are born or go deaf at a very young age who can't 'properly' speak.