The trouble with sub-titles is..... even if you understand the dialogue easily, you seem to be mostly reading the subtitles instead of watching the action. I have a friend who has a deaf son, and her TV has the sub-titles on permanently, and I find that very distracting.

I do take Steve Shaw's point about the background music, though. Sometimes it overpowers the dialogue enough to be irritating, and I have good hearing. How anyone with partial or tonal loss manages is anyone's guess.