I have a 14-year-old cat who showed signs of deafness about a year ago. I suspect that the hearing loss started before that, but it didn't become noticeable until there was a significant loss. He is now - I suspect - completely deaf. You can bang two pans behind him loudly, and he will not twitch an ear. The vet says that, unfortunately, as this is age-related, there is nothing to be done.
In some ways he is less nervous now as he always hated loud noises (the Hoover was especially frightening), but the problem is that I worry about him... a lot. We live somewhere very quiet with hardly any traffic, which does take a bit of the worry away, and I check where he is before starting the car. Keeping him inside is not an option as he very much likes to go outside still, but he has naturally restricted himself to the garden more and more as his deafness worsened. Previously, he'd happily explore several fields away. I never worried as he was very reliable at coming when he was called. You could whistle and then he'd soon be trotting through the fields to come home. He'd also walk with me down the lane, but he stopped doing that as his deafness worsened.
I don't know why I am posting really. Maybe just for some support from others with older cats with hearing issues. We have had other old cats before, but none went deaf to this degree. Maybe for some tips to stop me worrying needlessly!